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Hepatitis C virus infection in injection drug users Grebely, Jason Steven 2007

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HEPATITIS C VIRUS INFECTION IN INJECTION DRUG USERS by JASON STEVEN GREBELY B.Sc, The University of British Columbia, 2002 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Pharmacology and Therapeutics) THE UNIVERSITY OF BRITISH COLUMBIA May 2007 © Jason Steven Grebely, 2007 ABSTRACT Injection drug users (IDUs) represent the core of the hepatitis C virus ( H C V ) epidemic, but little is known about the natural history and treatment of H C V in IDUs. This thesis characterizes spontaneous clearance of H C V , investigates H C V re-infection following clearance and evaluates novel models for improving uptake and treatment responses among IDUs. To better understand characteristics associated with H C V clearance in IDUs, data from a community-based cohort study were linked with longitudinal laboratory databases to compare individuals with H C V clearance to those with H C V persistence to evaluate factors associated with clearance of H C V infection. Aboriginal ethnicity and female gender were associated with increased rates of H C V clearance, while H I V co-infection and i l l ici t drug use were associated with increased H C V persistence. To further investigate the impact of i l l ici t drug use on H C V persistence, we compared the rate of re-infection in individuals with H C V clearance to the rate of infection observed in previously uninfected individuals to evaluate whether previous clearance o f H C V infection is protective against re-infection. Those with viral clearance were about 4 times less likely to become re-infected than those infected for the first time, suggesting that individuals with H C V clearance have a lower risk of acquiring H C V than individuals who have never been infected, despite ongoing exposure to H C V . Lastly, we sought to evaluate novel models for improving uptake o f and response rates to the treatment o f H C V among current and former IDUs. First, we demonstrated that within a prospective, multidisciplinary, directly observed therapy program for the treatment of H C V infection o f IDUs, overall response rates parallel results from large, randomized controlled trials, despite ongoing ill icit drug use during treatment. Second, we demonstrated a high uptake of and response to therapy among IDUs infected with H C V attending a weekly support group. Taken together, these data demonstrate that IDUs can be safely and successfully treated for H C V infection within a multidisciplinary program integrating H C V , addiction and primary care. i i Given the considerable burden of H C V infection in IDUs, this data contributes significantly to the field by providing a greater understanding of the natural history and treatment of H C V in this setting. i i i TABLE OF CONTENTS page ABSTRACT ii LIST OF TABLES J . vii LIST OF FIGURES .viii LIST OF SYMBOLS AND ABBREVIATIONS ix LIST OF PUBLICATIONS AND ABSTRACTS x ACKNOWLEDGEMENTS xii CO-AUTHORSHIP STATEMENT xiv CHAPTER I: INTRODUCTION TO HEPATITIS C VIRUS INFECTION IN INJECTION DRUG USERS 1 1.1 Injection Drug Users: The Overlooked Epicentre of the HCV Epidemic 1 1.2 Epidemiology of HCV Infection 2 1.3 Natural History of HCV infection 3 1.3.1 Introduction 3 1.3.2 Acute HCV Infection 4 1.3.3 Spontaneous Clearance of HCV 5 1.3.3.1 Host Factors Associated with HCV Clearance 5 1.3.3.2 Pathogen Factors Associated with HCV Clearance ,. 7 1.3.3.3 Spontaneous Clearance of HCV in IDUs - A Special Case? 8 1.3.3.4 HCV re-infection in IDUs 9 1.3.4 When Spontaneous Clearance Does Not Occur - Chronic HCV Infection 10 1.3.4.1 Progression of Fibrosis 11 1.3.4.2 Hepatic Consequences of Liver Disease 12 1.3.4.3 Factors Associated with Liver Disease Progression 12 1.4 Therapy for HCV Infection 13 1.4.1 Introduction 13 1.4.2 Interferon-a and Ribavirin 14 1.4.2.1 Interferon-a 14 1.4.2.2 Ribavirin 14 1.4.2.3 Interferon-a and Ribavirin Combination Therapy 15 1.4.3 Improving the Pharmacology of Interferon a and Ribavirin 16 1.4.3.1 Pharmacokinetics of Interferon a and Ribavirin 16 1.4.3.2 Pharmacodynamics of Interferon a and Ribavirin 18 1.4.4 Pegylated Interferon a and Ribavirin in Clinical Practice 21 1.4.4.1 Predicting Response to Therapy 22 1.4.4.2 Adverse Events 24 1.4.4.3 Current Treatment Guidelines 24 1.5 The Treatment of Hepatitis C Virus Infection in Injection Drug Users 25 1.5.1 Barriers in the Treatment of HCV in IDUs....... 25 1.5.2 HCV Treatment Uptake and Willingness Among IDUs 27 iv 1.5.3 Treatment of HCV Infection in IDUs: Early Anecdotal Reports 28 1.6 Summary 31 1.7 Key Gaps 32 1.8 Purpose and Specific Aims 33 1.9 References 34 CHAPTER II: FACTORS ASSOCIATED WITH SPONTANEOUS CLEARANCE OF HCV AMONG ILLICIT DRUG USERS 54 2.1 Introduction 54 2.2 Patients and Methods 55 2.2.1 Study Population 55 2.2.2 Laboratory Testing 55 2.2.3 Statistical Analysis 56 2.3 Results 57 2.4 Discussion 58 2.5 References 66 CHAPTER III: HEPATITIS C VIRUS RE-INFECTION IN INJECTION DRUG USERS 69 3.1 Introduction 69 3.2 Patients and Methods 70 3.2.1 Study Population 70 3.2.2 Laboratory Testing 71 3.2.3 Statistical Analysis 72 3.3 Results 72 3.4 Discussion 74 3.5 References 83 CHAPTER IV: DIRECTLY OBSERVED THERAPY FOR THE TREATMENT OF HEPATITIS C VIRUS INFECTION IN CURRENT AND FORMER INJECTION DRUG USERS 86 4.1 Introduction 86 4.2 Patients and Methods 87 4.3 Results ... 89 4.4 Discussion 90 4.5 References 100 CHAPTER V: TREATMENT UPTAKE AND OUTCOMES AMONG CURRENT AND FORMER INJECTION DRUG USERS RECEIVING DIRECTLY OBSERVED THERAPY WITHIN A MULTIDISCIPLINARY GROUP MODEL FOR THE TREATMENT OF HEPATITIS C VIRUS INFECTION 103 v 5.1 Introuction 103 5.2 Patients and Methods 104 5.3 Results 106 5.4 Discussion 108 5.5 References. 114 CHAPTER VI: GENERAL CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK 116 6.1 General Conclusions 116 6.1.1 Natural History of HCV in IDUs...... 116 6.1.2 Treatment of HCV in IDUs 118 6.2 Limitations 119 6.3 Overall Significance of Results and Future Directions 120 6.4 Closing Remarks 122 6.5 References 124 APPENDIX 127 vi LIST OF TABLES page Table 2.1 Characteristics of participants with persistent HCV versus those with HCV clearance 62 Table 2.2 Characteristics of participants with persistent HCV versus those with HCV clearance 63 Table 2.3 Multiple logistic regression of factors associated with clearance of HCV infection 64 Table 3.1 Characteristics of participants without previous infection versus those with HCV clearance 78 Table 3.2 Occurrence of HCV viremia in all participants without previous infection versus those with HCV clearance 79 Table 3.3 Occurrence of HCV viremia in HIV negative and HIV positive previously infected individuals with HCV clearance 80 Table 3.4 Characteristics of participants with HCV re-infection 81 Table 4.1 Baseline Characteristics 94 Table 5.1 Baseline characteristics among the 18 subjects in whom treatment for HCV infection was initiated I l l Table 5.2 Treatment for hepatitis C virus (HCV) infection among the 18 current and former injection drug users initiating therapy at the Pender Community Health Centre in Vancouver, Canada 112 v i i LIST OF FIGURES page Figure 1.1 Natural history of HCV infection 4 Figure 1.2 Proposed model of immune response to HCV infection 5 Figure 1.3 Natural history of chronic HCV infection 11 Figure 1.4 Steady-state HCV kinetics during chronic infection, based on mathematical modeling of viral decay during interferon alpha therapy 19 Figure 1.5 Development of therapy for chronic hepatitis C virus infection 21 Figure 1.6 Virologic response to interferon-based therapy 23 Figure 2.1 Subject Disposition 65 Figure 3.1 Subject Disposition 82 Figure 4.1 Subject Disposition 95 Figure 4.2 Number of patients discontinuing interferon-based therapy early 96 Figure 4.3 Virological response to treatment in all patients as measured by HCV RNA.... 97 Figure 4.4 Virological response to treatment according to genotype and regimen received as measured by SVR, sustained virologic response 98 Figure 4.5 Virological response to treatment according to duration of drug abstinence and intercurrent drug use as measured by SVR 99 Figure 5.1 Patient Disposition 110 Figure 5.1 Virological response to treatment according to genotype in the 12 patients having completed therapy as measured by HCV RAN at the end of treatment 113 vi i i LIST OF SYMBOLS AND ABBREVIATIONS H C V hepatitis C virus IDUs injection drug users R N A ribonucleic acid A L T alanine aminotransferase HIV human immunodeficiency virus CD4 cluster of differentiation 4 (cell receptor) CD8 cluster of differentiation 8 (cell receptor) N K natural killer H L A human leukocyte antigen IL-10 interleukin 10 IL-19 interleukin 19 IL-20 interleukin 20 TNF-alpha tumor necrosis factor alpha Rh rhesus factor SVR sustained virologic response D N A deoxyribonucleic acid P E G polyethylene glycol a alpha E V R early virologic response ETR end of treatment response R V R rapid virologic response DOT directly observed therapy IFN interferon PEG-IFN pegylated interferon C H A S E Community Health and Safety Evaluatior H B V hepatitis B virus EIA enzyme immunoassay chi-squared OR odds ratio A O R adjusted odds ratio CI confidence interval IU international units Ab antibody RNA+ ribonucleic acid positive R N A - ribonucleic acid negative R B V ribavirin U L N upper limit of normal PCR polymerase chain reaction IQR interquartile range H C C hepatocellular carcinoma ix LIST OF PUBLICATIONS AND ABSTRACTS Material from this dissertation has been published in: • Grebely J, Raffa JD, Meagher C, Duncan F, Elliott D, Gallagher L , Genoway K A , Khara M , MacKenzie L , McLean M , Mead A , Quesnelle J, Showier C, Suvorova N , Viljoen M , Vincent K , deVlaming S, Fraser C and Conway B. Directly Observed Therapy for the Treatment of Hepatitis C Virus Infection in Current and Former Injection Drug Users. Journal of Gastroenterology and Hepatology. 2007. (In Press) • Grebely J, Conway B , Raffa JD, Lai C, Krajden M and Tyndall M W . Hepatitis C Virus Re-infection in Injection Drug Users (Letter, Author's Reply). Hepatology. 2007; 45(5): 1331. • Grebely J, Raffa JD, Lai C, Krajden M , Conway B and Tyndall M W . Factors Associated With Spontaneous Clearance of H C V Among Illicit Drug Users. Canadian Journal of Gastroenterology. 2007. (In Press) • Grebely J, Duncan F, Viljoen M , Khara M , DeVlaming S and Conway B. Current Approaches To H C V Infection in Current and Former Injection Drug Users. Journal of Addictive Diseases. 2007. (In Press) (Invited Review) • Grebely J, Genoway K A , Khara M , Duncan F, Elliott D, Raffa JD, deVlaming S and Conway B. Treatment Uptake and Outcomes Among Current and Former Injection Drug Users Receiving Directly Observed Therapy Within a Multidisciplinary Group Model for the Treatment of Hepatitis C Virus Infection. International Journal of Drug Policy. 2007. (In Press) • Grebely J, Conway B , Raffa JD, Lai C, Krajden M and Tyndall M W . Hepatitis C Virus Re-infection in Injection Drug Users. Hepatology. 2006; 44(5): 1139-45. • Conway B , Grebely J and Duncan F. Time For A Systematic Approach To The Treatment Of Hepatitis C Virus Infection in Injection Drug Users. Future Virology. 2006; 1(2):139-141. (Invited Editorial) • Conway B , Grebely J, Tossonian H , Lefebvre D and deVlaming S. A Systematic Approach to the Treatment of HIV & H C V Infection in the Inner City: A Canadian Perspective. Clinical Infectious Diseases. 2005; 41(S1):S73-S78. (Invited Review) Material from this dissertation has been presented in oral format at the following international meetings: • Grebely J, Conway B, Raffa J, Lai C, Krajden M and Tyndall M W . Impact Of HIV Infection On Hepatitis C Virus (HCV) Persistence Among Injection Drug Users (IDUs) [Abstract THPE0034]. In: Program and Abstracts of the X V I International AIDS Conference, Toronto, Canada, August 13-18, 2006. • Grebely J, Meagher C, Raffa J, Duncan F, Khara M , Viljoen M , Genoway K , Fraser C, DeVlaming S, Conway B. Treatment of hepatitis C virus (HCV) infection in injection drug users (IDUs) enrolled in a directly observed therapy (DOT) program [Abstract We.03.3]. In: Program and Abstracts of the 17th International Conference on the Reduction of Drug Related Harm, Vancouver, Canada, April 30-May 4; 2006. x • Grebely J, Conway B , Raffa J, Lai C, Krajden M and Tyndall M . Natural History of Hepatitis C Virus Infection Among Injection Users in Vancouver, Canada [Abstract 87]. Hepatology 2005; 42(S1):230A. Material from this dissertation has been presented in poster format at the following international meetings: • Grebely J, Raffa J, Lai C, Krajden M , Conway B and Tyndall M W (Accepted November 13, 2006). Effect of Hepatitis C Virus (HCV) and Human Immunodeficiency Virus (HIV) Infections on Mortality Among Illicit Drug Users. In Programs and Abstracts of the 14 t h Annual Conference on Retroviruses and Opportunistic Infections, Los Angeles, C A , February 25-28, 2007. • Grebely J, Raffa J, Lai C, Krajden M , Conway B and Tyndall M W . Impact of Human Immunodeficiency Virus (HIV) Infection on Hepatitis C Virus (HCV) Persistence Among Illicit Drug Users. In Programs and Abstracts of the 57 t h Annual Meeting of the American Association for the Study of Liver Disease, Boston, M A , October 27-31, 2006. • Grebely J, Conway B , Raffa J, Lai C, Krajden M and Tyndall M W . Impact Of HIV Infection On Hepatitis C Virus (HCV) Persistence Among Injection Drug Users (IDUs) [Abstract THPE0034]. In: Program and Abstracts of the X V I International AIDS Conference, Toronto, Canada, August 13-18, 2006. • Genoway K , Grebely J, Raffa J, Duncan F, Khara M , Viljoen M , DeVlaming S, Tyndall M , Conway B. Initiation of Hepatitis C Virus (HCV) Treatment among Injection Drug Users (IDUs) [Abstract We.l42P]. In: Program and Abstracts of the 17th International Conference on the Reduction of Drug Related Harm, Vancouver, Canada, April 30-May 4, 2006. • Grebely J, Meagher C, Duncan F, Viljoen M , Khara M , Raffa J, Genoway K , DeVlaming S, Fraser C and Conway B . Treatment Of Hepatitis C Virus (HCV) Infection In Injection Drug Users (IDUs) Using Directly Observed Therapy (DOT) [Abstract 103]. Global Antiviral Journal 2005; 1(S2):102. • Duncan F, Grebely J, Genoway K , Viljoen M , Khara M , Raffa J, Tyndall M , DeVlaming S and Conway B. Barriers Associated With The Initiation Of H C V Treatment In Injection Drug Users (IDUs): An Opportunity For Optimizing Outcome In Marginalized Populations [Abstract 102]. Global Antiviral Journal 2005; 1(S2):101. • Grebely J, Meagher C, Duncan F, Viljoen M , Khara M , Raffa J, Genoway K , DeVlaming S, Fraser C and Conway B . Directly Observed Therapy (DOT) For The Treatment Of Hepatitis C Virus (HCV) Infection In Injection Drug Users (IDUs) - A n Interim Analysis [Abstract 1241]. Hepatology 2005; 42(S 1):686A. • Grebely J, Conway B, Raffa J, Lai C, Krajden M , Kerr T, Wood E and Tyndall M . Effect of HIV co-infection on spontaneous clearance of hepatitis C virus (HCV) in the downtown eastside of Vancouver [Abstract TuPel. lC18]. In: Program and Abstracts of the 3 r d Conference on HIV Pathogenesis and Treatment (Rio de Janeiro, Brazil), 2005. Material from this dissertation has also been presented orally for the Graduate Student Seminars Series in the Department of Anesthesiology, Pharmacology and Therapeutics at U B C xi ACKNOWLEDGEMENTS M y time as a graduate student has been enjoyable and has taught me lessons that w i l l prove valuable in my endeavors as an investigator. Foremost, my deepest thanks go to Dr. Brian Conway, who embodies everything one could ask for in a scientist, supervisor and friend. Through his guidance, I have developed a stronger focus and achieved considerable development as an individual and a scientist. He has provided me with opportunities that very few graduate students experience, which have significantly developed my understanding and capacity for research. I owe him a great sense of gratitude for the knowledge and experiences he has shared with me and for his confidence in my abilities, his trust in my leadership, his encouragement and his never-ending patience. Wi th this, I owe you a great deal of gratitude and thanks. Thank you. Second, I must thank my good friend and colleague, M r . Jesse Raffa. Without you, much o f this work could not have been possible. Your continuous statistical expertise and patience has enhanced my knowledge, helping me to become a better researcher. I appreciate everything you have done for me and I look forward to our continued work together in the field. Also, I must thank Dr. Mark Tyndall, Dr. M e l Krajden and Dr. Ismail Laher. A s committee members, you have gone above and beyond your duties. First, I must thank Dr. Tyndall and Dr. Krajden for their continuous guidance, patience and continuous encouragement in the conduct of my research. Y o u have consistently dedicated a considerable amount o f time to my development as a researcher, acting as co-supervisors rather than committee members. I appreciate your efforts in this regard and none o f this work would have been possible without your support. I must also thank Dr. Ismail Laher for providing his pharmacology expertise and his guidance in developing my future research plans. Your involvement has been greatly appreciated. Over the past several years, I have also had the opportunity to learn and work with an exceptional group of trainees, physicians, nurses, counselors and administrative staff at the Pender Community Health Centre (PCHC) . I would like to thank Harout Tossonian and Krista Genoway for your hard work and dedication. Al so , I must thank Dr. Stanley deVlaming. A s physician leader at the P C H C , you have provided me with limitless resources and support in my x i i aspirations to expand H C V treatment in the Downtown Eastside of Vancouver. I also owe a deep gratitude towards Dr. Fiona Duncan, Dr. Mark Vil joen and Dr. Mi lan Khara for all o f your efforts in the development of the H C V treatment program at P C H C . Without your considerable dedication towards improving the lives o f those l iv ing with H C V , we would not have achieved such success. I respect you as colleagues and friends and look forward to continuing this relationship in the future. In addition, I must thank the nurses at P C H C , Lian McKenz ie , Jennifer Quesnelle and Natasha Suvorova, without whom there would be no program for the treatment of H C V infection. Y o u are truly valued in the work that you do. I must also thank one special nurse, Lesley Gallagher. Since the beginning of my studies, you have constantly been there for support, as a co-worker and friend. I have always appreciated your input and have immensely enjoyed working with you. Your dedication towards patients l iving with H C V does not go unnoticed and you have played a key role in the success of our research program. For this I thank you. Lastly, I must thank Doug Elliott, our H C V counselor. Your assistance with the development of the H C V program at Pender has translated into considerable success, as measured by our explosive growth over the past year. I appreciate your help and you have become a good friend. To the rest of the physicians, nurses, counselors and administrative staff at P C H C , thank you for your support. I perhaps owe the greatest gratitude to my mother, father and sister, who throughout my life have continuously forced me to push the envelope towards reaching my goals, explore new opportunities and achieve the unattainable. Your guidance has been essential in my inherent drive and my development as an individual. I must also thank my uncle, Andrew Grebely, for providing my with countless opportunities that contributed to my development as an individual and spending the time with an inquisitive young mind with a mil l ion questions that needed answers. To my most amazing family and friends, thank you for your encouragement, advice, love and support. Thank you for understanding when I couldn't be there and thank you for being there when I needed you. Finally, I would like to acknowledge the Natural Canadian Research Training Program in Hepatitis C for salary and training support and Schering Canada, Hoffmann-La Roche Ltd., the B C Medical Services Foundation and Vancouver Coastal Health for their financial assistance. x i i i CO-AUTHORSHIP STATEMENT Chapter 2: Factors Associated With Spontaneous Clearance of HCV Among Illicit Drug Users Mark W. Tyndall was responsible for the development and recruitment of the cohort described in this paper and reviewing the final draft. Calvin Lai performed necessary data linkages and database management tasks. Jason Grebely developed the experimental approach together with the Brian Conway, Mel Krajden and Mark W. Tyndall. Jason Grebely conducted the analysis of research in collaboration with Jesse D. Raffa, who performed the detailed statistical analysis. Jason Grebely wrote the initial draft of this chapter and attended to the revisions required for final publication. Brian Conway and Mark W. Tyndall supervised the research and assisted with revisions of the final draft. Chapter 3 : Hepatitis C Virus Re-infection in Injection Drug Users Mark W. Tyndall was responsible for the development and recruitment of the cohort described in this paper and reviewing the final draft. Calvin Lai performed necessary data linkages and database management tasks. Jason Grebely developed the experimental approach together with the Brian Conway, Mel Krajden and Mark W. Tyndall. Jason Grebely conducted the analysis of research in collaboration with Jesse D. Raffa, who performed the detailed statistical analysis. Jason Grebely wrote the initial draft of this chapter and attended to the revisions required for final publication. Brian Conway and Mark W. Tyndall supervised the research and assisted with revisions of the final draft. Chapter 4: Directly Observed Therapy for the Treatment of Hepatitis C Virus Infection in Current and Former Injection Drug Users Jason Grebely developed the experimental approach and the study protocol together with the Brian Conway. Milan Khara, Fiona Duncan, Mark Viljoen, Chris Fraser, Annabel Mead, Mark McLean, Stanley deVlaming and Brian Conway were the physicians involved in patient xiv recruitment, the provision of H C V treatment and assisted with the design of the proposed study. Jason Grebely also performed all the data analysis in consultation with Jesse D . Raffa. Jason Grebely wrote the initial draft of this chapter and attended to the revisions required for final publication. Brian Conway supervised the research and assisted with revisions of the final draft. Caite Meagher assisted with data collection for the study. Brian Conway also supervised the research. Chapter 5: Treatment Uptake and Outcomes Among Current and Former Injection Drug Users Receiving Directly Observed Therapy Within a Multidisciplinary Group Model for the Treatment of Hepatitis C Virus Infection Jason Grebely and Doug Elliott were involved in the development of the weekly support group described in this paper. Jason Grebely developed the questionniares and study protocol under the supervision of Brian Conway. Jason Grebely also developed the experimental approach together with the Brian Conway. Mi l an Khara, Fiona Duncan, Mark Vil joen, Stanley deVlaming and Brian Conway were the physicians involved in patient recruitment, the provision of H C V treatment and assisted with the design of the proposed study. Jason Grebely performed all the data analysis in consultation with Jesse D . Raffa. Jason Grebely wrote the initial draft of this paper and attended to the revisions required for final publication. Brian Conway supervised the research and assisted with revisions of the final draft. Krista A . Genoway assisted in data collection and analysis of this study. Brian Conway also supervised the research. xv CHAPTER I Introduction to Hepatitis C Virus Infection in Injection Drug Users 1.1 Injection Drug Users: The Overlooked Epicentre of the HCV Epidemic Hippocrates first described viral hepatitis in the fifth century B C as an epidemic o f jaundice. Epidemics o f jaundice were particularly common during vaccination campaigns and wars occurring in the 19 t h and 20 t h centuries and are likely attributed to outbreaks of viral hepatitis. The first documentation of viral hepatitis transmitted by direct inoculation of blood or blood products was described by Lurman in Bremen, Germany, in 1883 during a smallpox immunization campaign (1). Various other outbreaks of hepatitis were subsequently described in a variety o f risk groups (2, 3). However, the lack of appropriate diagnostic assays precluded the identification o f the responsible agent(s). In the 1930s and 1940s, epidemiologic studies provided evidence to suggest that hepatitis was caused by at least two different etiologic agents. In 1947, MacCal lum and Bauer (4) proposed a nomenclature for two of these agents; hepatitis A , an agent predominant in children transmitted primarily by an oral-fecal route, and hepatitis B , which was common in adults and transmitted by percutaneous exposure to blood products. A s diagnostic assays became available to distinguish hepatitis A and hepatitis B , it became clear that there existed distinct etiologic agents responsible for a form of non-A, non-B hepatitis. Studies of patients infected with non-A, non-B hepatitis (5) led to the identification of hepatitis C virus ( H C V ) infection in 1989 (6) and hepatitis E virus in 1990 (7). H C V has spread extensively throughout the world as a result of its efficient parenteral transmission via transfusion of contaminated blood products, medical procedures and injection drug use. In developed nations, the availability of sensitive assays for the detection of H C V , universal blood donor screening and the development of health policies for the sterile administration o f therapeutic injections led to a virtual elimination of iatrogenic transmission of H C V . However, H C V transmission remains rampant among individuals engaged in injection drug use as a result of the sharing of injection equipment. It is now evident in this setting that injection drug users (IDUs) represent the majority of infected cases o f H C V and are the major source of new infections. Among long-term injectors, 90% o f IDUs are infected with H C V and 1 are at considerable risk of developing serious liver complications, including cirrhosis, end stage liver disease^ hepatocellular carcinoma and death. A n y effort to reduce the global burden of H C V infection must include research into the natural history and treatment of H C V infection in IDUs, the overlooked core of the H C V epidemic. 1.2 Epidemiology of HCV Infection Since its discovery in 1989, H C V has been recognized as a major cause o f chronic liver disease. The most recent estimates from the Wor ld Health Organization suggest that the global prevalence of H C V is -2 .0%, representing 125-170 mil l ion infected individuals worldwide (8). In Canada, it is estimated that 300,000 individuals (0.8%) are infected with H C V , with 5,000-7,000 new infections occurring each year (9). However, these figures l ikely underestimate the true burden o f H C V , given that homeless and incarcerated populations, in which infection is most prevalent, are not included in these estimates. Risk factors most commonly attributed to H C V transmission include blood transfusion from unscreened donors, injection drug use, unsafe therapeutic injections, and other health-care related procedures (10). Although sexual and maternal-fetal transmission of H C V has been observed, this occurs relatively infrequently. In developing nations, the widespread administration o f unsafe therapeutic injections and transfusions from unscreened donors represent major modes of H C V acquisition (10). IDUs represent the core of the H C V epidemic in many developed nations, with the majority of new and existing infections occurring in this group. In Canada, the United States, Europe and Australia, IDUs account for 50-70% of existing infections (11-16) and the proportion of new infections attributed to injection drug use is steadily increasing. Data from Canada and Australia suggest that 65-93% of incident H C V infection is associated with injection drug use (17, 18). H C V infection is thought to occur rapidly after the initiation of injection drug use. In one study, the prevalence of H C V infection was 78% among individuals with at least 1 year of injection drug use experience (19). A s the duration o f injection drug use increases, so does the likelihood 2 of acquiring H C V infection. In the same study, 94% of individuals with >10 years o f injection drug use tested positive for H C V infection. This association between the increased risk H C V acquisition as a result of longer injection drug use duration has also been observed in other populations o f IDUs (20-23). Among long-term IDUs with an injection history o f more than 6 years, the prevalence of H C V remains high, with 64-94% of IDUs testing positive for H C V (19, 24). Similar results have been reported from high-risk cohorts of IDUs in Canada. Among 2,000 such individuals recruited into the V I D U S (Vancouver Injection Drug Users Study) and SEOSI (Scientific Evaluation of the Supervised Injection Site) cohorts, the H C V prevalence was 82-88% (13, 25). Recent data from Vancouver and San Francisco suggest that the spread of infection is still rampant, given that H C V incidence rates ranging from 30-52% have been observed among high-risk, young IDUs (26, 27). If any effort is to be made to alter the current epidemiology o f H C V and curtail the epidemic in this population, it is imperative that programs are designed to address H C V infection in this group, with the goal of preventing long-term liver related morbidity and mortality associated with H C V and the transmission o f infection. 1.3 Natural History of HCV infection 1.3.1 Introduction Hepatitis C infection is caused by a small, single-stranded positive sense R N A virus (28, 29). H C V primarily infects and replicates in hepatocytes in the liver. However, evidence exists for extrahepatic reservoirs of infection including peripheral blood lymphocytes (29), epithelial cells in the gut (30) and the central nervous system (31). In the liver, H C V replicates at a high rate, generating average serum H C V R N A levels o f 1 to 2 mil l ion genome equivalents per millilitre (32). Replication occurs via the H C V RNA-dependent R N A polymerase, which is highly error prone and lacks proofreading capacity, resulting in the development of random mutations into the viral genome (29). This can lead to the establishment of a population o f closely related, yet heterogeneous sequences of H C V within an individual, the viral quasispecies. This high error rate of RNA-dependent R N A replication and interactions between the virus and host over time have led to considerable global diversity in the genetic composition o f H C V . Overall, 6 genotypes of H C V exist, which vary in nucleotide sequence by 30 to 50% (33). The distribution of H C V genotypes often vary by either geographic region or the risk behaviour for acquisition (34). O f the six identified genotypes, H C V genotypes 1, 2 and 3 are the most common in North America, with 65-75% of subjects in the United States and Canada infected with genotype 1 (35-3 38). Data suggests that the prevalence of H C V genotype 3 a is much higher in IDUs than in other risk groups, although this may vary with geographic region (38-44). H C V genotype appears to have no effect on the pathogenesis and natural history of H C V . 1.3.2 Acute HCV Infection Initial infection with H C V is characterized by the rapid appearance of H C V viremia in the blood (within 2-14 days o f exposure), increases in liver-associated serum enzymes (i.e. alanine aminotransferase, A L T ) and the gradual appearance of HCV-specif ic antibodies (within 20-150 days o f exposure) (27, 45-47). Infection with H C V is often asymptomatic, with only 15-30% of individuals developing an acute hepatitis syndrome, which is generally mild, occurs within 5-12 weeks of exposure and lasts 2-12 weeks (48, 49). Acute infection with H C V generally lasts 6 months and is characterized by a low likelihood of spontaneous clearance, defined by the resolution o f infection. However, in the majority of acutely infected subjects (55-85%) viremia persists beyond 6 months, leading to the development of chronic H C V infection (Figure 1.1). I HCV 15-45* j Acute hepatitis 55-85% | Chronic hepatitis \ Recovery 15-25% Cirrhosis H C C , ESLD Figure 1.1 Natural history of H C V infection. Two patterns o f H C V viremia during the acute phase o f H C V have been described among humans (50, 51) and chimpanzees (52, 53) (Figure 1.2). The first pattern involves a significant drop in viremia after it reaches peak levels and is associated with successful spontaneous clearance o f H C V . Although a transient rebound in viremia may occur after an initial peak, in this setting, H C V R N A is cleared from the blood o f these individuals during the first 6 months of infection. The other pattern of viremia occurs among individuals who do not achieve viral clearance and develop persistent viremia. In some individuals, H C V R N A may be continuously detected in the plasma during the entire phase of acute infection, resulting in chronic infection. 4 Alternatively, some individuals may temporarily control viral replication, but then subsequently lose control, leading to viral rebound and the development o f persistent infection. In the setting o f acute H C V infection, successful spontaneous clearance w i l l occur in -15-45% of subjects. A B * o 8 ~ I 1 i r 1 1 1 — 1 2 3 4 5 6 Time after infection (months) (t 2 3 4 5 6 Time after infection (months) - o 7 X Figure 1.2 Proposed model of immune response to H C V infection. A . H C V clearance. B . H C V persistence (50, 51). 1.3.3 Spontaneous Clearance of HCV Clearance of H C V is dependent on the route of transmission and other host and pathogen-related characteristics. Host factors associated with H C V clearance include the initial immune response to H C V (54-61), the age at time o f H C V infection (62, 63), alcohol (64), sex (63, 65-69) and race (70, 71). In addition, pathogen-associated factors such as the diversity of H C V viral quasispecies (72), the H C V viral load (63) and co-infection with H I V (63, 70, 73) have been associated with the host's ability to resolve H C V infection. However, the ability to develop a complete understanding of virologic clearance in the setting o f acute infection is limited by the small numbers of reported cases, the frequent asymptomatic nature o f acute infection and the fact that infection often goes undetected. 1.3.3.1 Host Factors Associated with HCV Clearance The most important factor in the spontaneous clearance o f H C V is the breadth and vigour o f initial immune response to H C V (74, 75). Chimpanzees (75-77) and humans (54-61) who mount an early, multi-specific CD4+ and CD8+ T-cell response to H C V proteins can achieve virologic clearance. Moreover, the inability to maintain sustained activation of CD4+ and CD48+ T-cell responses in both humans (55, 61) and chimpanzees (75, 77) with acute H C V infection leads to a 5 loss o f spontaneous control and the development of persistent infection. These data speak to a co-ordinated role for both CD4+ and CD8+ T cells in the control o f initial infection with H C V . In addition to immunity, several other host factors are important in determining clearance of H C V . Increased alcohol consumption has been observed to reduce clearance of infection, however, the mechanism behind this observation is not clear (64). The impact of age at infection on H C V clearance is apparent from the observation that H C V clearance rates in transfusion associated-hepatitis that largely included individuals >50 years of age are - 1 5 % (5, 78) compared to ~45% among infected infants and young women (62, 65, 79, 80). In one study of hemophiliacs without H I V infection, individuals infected before the age o f 2 years had a much higher rate of H C V clearance (40%) as compared to those infected after the age of 15 years (15%>). This is consistent with several other studies demonstrating that a younger age at infection is associated with increased rates of H C V clearance (79, 81). Gender may also be important in determining clearance of H C V . In a systematic review of thirty-one longitudinal studies evaluating the correlates of spontaneous H C V clearance, gender was the only significant predictor of clearance with males being two-times less likely to clear H C V spontaneously (19%) when compared to females (40%) (69). Wi th respect to ethnicity, it has been demonstrated that African Americans may have decreased rates of H C V clearance when compared to Caucasians (70, 71). Conversely, there are data from Canada and the United States demonstrating higher rates o f spontaneous clearance among Aboriginal people when compared to Caucasians (82-84). Although the relationship between age, gender and clearance of H C V is well defined, further studies are needed to investigate the role o f ethnicity in this context. The association o f gender and race with spontaneous H C V clearance suggests that host genetic factors encoding immunity to H C V may play an important role in viral control of H C V infection. It has been demonstrated that genetic polymorphisms encoding proteins involved in the innate and adaptive immune response to H C V may be associated with clearance (85-91). Inhibitory N K cells and the innate immune response may be important in clearance (91). It has been demonstrated that the activity of certain genes encoding interactions between H L A class I molecules and N K cells may play an important role in the effectiveness of this process (91). Given the importance o f the inflammatory response in the eradication of H C V infection, data suggest that certain genetic polymorphisms o f proteins involved in inflammatory and cellular immune responses to H C V (such as IL-10, IL-19, IL-20 and TNF-alpha) are associated with 6 reduced viral clearance (85, 90, 92). Immunologic studies in Aboriginals suggest a lower genetic tendency to produce IL-10 than Caucasians and a reduced susceptibility to H C V protein induced IL-10 immune responses, implicating a role for the immune system in this enhanced protection (93). Additionally, polymorphisms in genes encoding enzymes with antiviral activity against H C V may have an impact of the host to naturally resolve H C V infection (94). There are also data to suggest that polymorphisms in genes encoding H L A class I and II molecules, which interact with C D 4 and CD8 T cells and stimulate an efficient adaptive immune response against H C V , are associated with clearance of H C V infection (86, 87, 89, 95, 96). A number o f these studies have demonstrated that the expression of genetic polymorphisms of many of these proteins differs among various ethnicities and may partially explain differences in clearance among different ethnicities (85, 87, 90). However, further research is needed in order to better understand the associations between host genetics, the immune system and H C V clearance. 1.3.3.2 Pathogen Factors Associated with HCV Clearance In addition to host-related characteristics, pathogen-associated factors such as the diversity o f viral quasispecies (72), H C V viral load (71, 97) and co-infection with H I V (63, 70, 73) have been associated with clearance of H C V infection. Given the infidelity o f the RNA-dependent R N A polymerase, mutations are frequently incorporated into the replicating H C V R N A genome. This leads to the generation of a diverse population of closely related viral variants known as the quasispecies, which may allow the virus to circumvent the immune response to H C V . In humans, the development of a diverse viral quasispecies during acute H C V infection has been associated with mutations in various H C V proteins and an impaired ability to spontaneously resolve H C V infection (72). The fact that lower levels of H C V R N A are associated with increased clearance may relate to some reduction in quasispecies generation (71, 97). There have been several studies which have demonstrated that H I V infection is associated with a two-fold decrease in clearance of H C V infection (63, 70). However, the absence of systematic testing in these populations and the asymptomatic nature of H C V infection often has made it difficult to detect the order of H I V and H C V infections and determine whether H I V decreases H C V clearance or increases H C V persistence, through either a recrudescence of existing low-level viremia or an increased susceptibility towards re-infection. Further studies are needed to fully elucidate the impact of H I V infection on persistence of H C V . 7 It is clear that a delicate balance between host, viral and environmental factors, determines spontaneous clearance of H C V infection. Host immunity and CD4+ and CD8+ T-cell responses against H C V probably determine the ability of the host to resolve infection. However, this is countered by the considerable diversity o f H C V and its ability to evade the host immune response during initial infection. This is complicated by a number o f external factors that can tip the balance in favour of the virus or the host. 1.3.3.3 Spontaneous Clearance of HCV in IDUs - A Special Case? It is important to note that although these studies of virologic clearance have significantly improved our understanding of the natural history of H C V infection, the majority of them have been performed in groups other than IDUs. These include community-based studies o f young women and children infected with H C V following exposure to contaminated blood products (65, 79, 80), blood donors (98) or persons with post-transfusion hepatitis (99). Such individuals are at an increased risk of engaging in alcohol and injection drug use, both o f which may increase the persistence of H C V infection. Additionally, the use of il l icit drugs has a significant impact on the immune system (100) and may impair the ability of the host to spontaneously clear H C V infection. A s such, it is important to understand the factors associated with clearance among IDUs and current knowledge in this field is limited at best. This being said, viral clearance rates among cohorts of injection drug users range from 11% to 42%, depending on the population studied (63, 70, 71, 101). Currently, the majority of what is known o f the natural history of H C V infection among IDUs comes from a large longitudinal study in Baltimore developed to investigate the natural history of H I V infection in this population (19, 70, 71). In one study from this cohort, 43 individuals developing acute H C V infection were assessed for viremia and factors associated with viral clearance. Vira l clearance was observed in 19% (6/34) of individuals, with white ethnicity (vs. black), icteric presentation and lower peak viral titre associated with viral clearance (71). In follow-up to this study, the investigators evaluated H C V clearance among a larger subset of 919 subjects with chronic H C V infection (70). Overall, only 11% of subjects had spontaneous clearance o f H C V , with clearance occurring more frequently in non-blacks and individuals without H I V co-infection. However, in these studies, ~90% of subjects were black and ~80% were male, both o f which are associated with reduced clearance of H C V , making it difficult to generalize the interpretations of these data to other settings with higher proportions o f other ethnicities and females. One study from 8 Australia evaluating H C V clearance among 57 young IDUs with acute H C V infection in a predominantly Caucasian population (63%) demonstrated a clearance rate of 42%. However, given the small sample size in this study, no factors associated with H C V clearance could be identified (101). Further data from a cohort of 418 H C V seropositive IDUs in New York demonstrated that 25% achieved H C V clearance (63). Factors associated with clearance of H C V included female gender and the absence of both H I V co-infection and injection drug use behaviours. A s such, given the small number o f studies investigating the natural history of H C V infection and the small sample sizes in those studies with data available, there are considerable gaps in our knowledge in this area. The association of injection drug use and decreased clearance of H C V is interesting and warrants further research, given that re-infection with H C V as a result of ongoing injection drug use may increase H C V persistence. Moreover, further work is required to understand the impact o f H I V infection on persistence o f H C V in IDUs, given that the order of H I V and H C V infections are often not known and it is not certain whether H I V is impacting clearance or persistence of H C V . Lastly, the impact of other ethnicities on H C V clearance remains to be determined. It is apparent that further work investigating factors associated with clearance o f H C V among IDUs wi l l be essential in understanding the pathogenesis of H C V in the population which is most affected by this condition. 1.3.3.4 H C V re-infection in IDUs Following spontaneous clearance of H C V infection, it is not clear whether previous clearance provides protection against re-infection among IDUs with ongoing injection drug use. Re-infection can occur and has been demonstrated in a variety of settings. Viremia reappeared in 5 thalassemic children that were re-challenged after spontaneous H C V clearance (102) and H C V patients who receive a liver transplant from an H C V + donor have shown super-infection with a new genotype (103). Re-infection has also been observed among IDUs who were subsequently re-exposed to the virus (104-106). However, in chimpanzees re-infected with H C V , there is often rapid control o f viral replication, short-lived viremia and universal spontaneous resolution of secondary infection (107). Although re-infection can occur in chimpanzees re-challenged with H C V after its clearance (77, 108-110), there is a relative resistance to subsequent H C V infection likely related to immune protection 9 (108, 111). A l l infected chimpanzees that have been studied to date demonstrate an attenuated course of infection, with lower H C V levels and no evidence of liver disease (77, 109-111). This is consistent with protective immunity. Also , rapid control o f re-infection was associated with HCV-specif ic T-cell responses (77, 109). When CD4+ T-cells were depleted in vivo before re-infection, chronic H C V infection ensued (75). Similarly, the depletion of CD8+ T-cells led to prolonged H C V viremia, which was only controlled once CD8+ T cells reappeared in the liver (77). However, there are limited data about whether protective immunity to H C V exists in humans. One study of acute H C V infection and re-infection demonstrated that H C V viremia in the setting o f H C V re-infection was at a lower level, generally transient and shorter duration than compared to initial infection (56). In one epidemiological study o f IDUs, the incidence of H C V infection over 6 -24 months was 12% in 98 subjects who were known to be H C V antibody positive but aviremic, as compared to 21% in 164 subjects never infected with this virus (73). This suggests that IDUs with previous clearance of H C V had a lower risk of developing de novo infection as compared to individuals with no evidence of previous infection. Moreover, individuals that had spontaneously cleared H C V infection and subsequently acquired H I V infection during the follow-up period lost this apparent immune protection, implicating a role for CD4+ T-cells in HCV-specif ic immunity. Although these studies suggest that HCV-specif ic protective immunity may occur in some individuals with resolution of H C V , further studies are required to confirm these findings. Additionally, it w i l l be important to understand whether the protective immunity that is observed in the setting of natural H C V clearance also applies to treatment-induced clearance of viremia. If protection against H C V re-infection does occur, this could have important implications for the treatment of H C V in IDUs and development of vaccines for individuals at highest risk, with the goal of preventing the long-term liver-related morbidity and mortality associated with H C V infection. 1.3.4 When Spontaneous Clearance Does Not Occur - Chronic HCV Infection The clinical course of chronic H C V infection generally unfolds over several decades and the majority of individuals do not manifest symptoms that can be clearly linked to the infection (Figure 1.3). Chronic H C V infection is defined by the persistence of H C V R N A >6 months beyond initial exposure. Subsequent to infection with H C V , the serum H C V R N A w i l l often reach a stable level between 4 and 6 logio which w i l l remain relatively constant for decades, 10 while the serum alanine aminotransferase ( A L T ) levels often fluctuate (112-114). The most important sequelae of chronic H C V infection are progressive liver fibrosis, leading to cirrhosis, end-stage liver disease and H C C (hepatocellular carcinoma). 0 0.5 1 2 5 10 15 20 25 30 35 40 45 50 Years After Exposure Figure 1.3 Natural history of chronic H C V infection (115). 1.3.4.1 Progression of Fibrosis Despite the fact that there may be very few clinical symptoms and signs o f liver progression before the development o f end-stage liver disease, histopathologic evidence of progression can be identified earlier. The gold standard for the assessment of the extent o f liver disease is the liver biopsy (116, 117), which provides important information on inflammation and fibrosis occurring in the liver. During persistent H C V infection, there is a chronic inflammatory response which is associated with the development o f fibrosis (118, 119). Fibrosis w i l l often progress into cirrhosis, eventually leading to end-stage liver disease or H C C (120). However, disease progression is affected by a number of factors and not all chronically infected patients follow this sequence o f events, and those who do progress do so over 20 to 40 years or even longer. 11 1.3.4.2 Hepatic Consequences of Liver Disease The percentage of chronically infected individuals developing cirrhosis during the first 10 to 20 years o f infection ranges from 5% to 25% (121-126). However, very little information is available regarding progression beyond 30 years. Although follow-up studies of persons infected at the time of blood product transfusion demonstrated a high rate o f cirrhosis two to three decades after exposure (17%-55%), these reports likely overestimated this risk due to a referral bias, given that these studies were performed in tertiary care clinics (119, 127-129). In one long-term study in which transfusion recipients with H C V infection were followed and matched with a group of uninfected transfusion recipients (99, 130), it was demonstrated that 15% o f H C V -infected subjects had cirrhosis within 20 years, with infected individuals having increased rates o f liver-associated mortality as compared to HCV-uninfected individuals (4.1% vs. 1.3%, P=0.05). However, lower rates o f cirrhosis have been observed in community-based studies. In one cohort of 1667 HCV-infected IDUs infected for an estimated mean of 14 years and followed for a mean of 8.8 years, a random sample of 210 HCV-infected subjects had liver biopsies performed and only 10% demonstrated serious liver disease (Ishak modified fibrosis scores of 3-6) (70). Similarly, in two other community-based studies o f females infected by contaminated R h immune globulin, the incidence of cirrhosis was <5% after 15 to 20 years of follow-up (65, 80). This is consistent with low rates o f cirrhosis (<5%) observed 20 years after infection during or shortly after birth (79, 131). O f those developing cirrhosis, it is estimated that end-stage liver disease and hepatocellular carcinoma occur at rates o f 2% to 4% and 1% to 7% per year, respectively (132-134). 1.3.4.3 Factors Associated with Liver Disease Progression Factors associated with increased progression of HCV-related liver disease include older age at infection (70, 135, 136), male sex (136), H I V co-infection (137-147), non-alcoholic steatohepatitis (148, 149) and heavy alcohol intake (150-154). Perhaps the most important predictor o f fibrosis progression is the age at which infection occurs (70, 135, 136). Low rates of progression to cirrhosis have been observed in young women infected via Rh immune globulin (65), young injection drug users (70) and persons infected during childhood (79, 155-157). This is in contrast with other studies containing a wider range o f age groups demonstrating that higher cirrhosis rates are observed in older individuals, even after adjusting for the duration of infection (136). In a large systematic review of 57 studies, the rate o f cirrhosis progression after 20 years o f chronic H C V infection was 22% among tertiary care liver clinic cohorts, 24% in studies of 12 post-transfusion hepatitis, 7% in community-based studies and 4% in studies of blood donors (158). Importantly, age at infection was significantly associated with increased liver disease progression, in addition to male gender and heavy alcohol intake. Alcohol intake is perhaps the most important environmental factor affecting liver fibrosis (150-154) and interacts in a synergistic fashion with H C V , with one study demonstrating that heavy alcohol intake (>50-125 g/day) leads to approximately a 100-fold increased risk of cirrhosis (152). Similarly, co-infection with H I V leads to rapid progression o f liver disease (137-147). In one study comparing fibrosis progression rates in 122 H I V / H C V co-infected subjects with 122 H C V infected controls, the time to progression of cirrhosis was significantly higher among H I V / H C V co-infected subjects, especially in the setting of increased alcohol consumption (137). Overall, the progression of chronic H C V is highly variable and is dependent on a number of host and environmental related factors. However, the availability o f an effective regimen for the treatment of H C V provides an important means of altering the natural history of H C V , thereby reducing the impact o f liver disease and its complications. 1.4 Therapy for HCV Infection 1.4.1 Introduction Advances in the treatment of H C V infection have led to the development of treatment regimens that can result in a cure in at least half of treated patients. The sustained virologic response (SVR) is the best indicator to date of treatment response, defined as the absence of viremia 24 weeks after the end of therapy. In most cases with S V R , viral eradication from the serum and the intrahepatic reservoirs remains durable over the long-term, given that 95-98% of these individuals w i l l remain aviremic following S V R (159, 160), consistent with a virologic cure (161). The long-term outcome of an S V R include the normalization o f A L T liver enzymes (162), improvement in hepatic necroinflammation and fibrosis stage (162), improvement in health related quality of life (163), a decreased chance of developing hepatocellular carcinoma (164) and improved survival (165). 13 1.4.2 Interferon-a and Ribavirin 1.4.2.1 Interferon-a In 1986, the causative agent responsible for the development of "non-A, non-B" hepatitis had not yet been discovered. A s such, nothing was known of the suspected viral characteristics that would assist in drug design and there was no way of evaluating antiviral activity. However, given its activity against a wide spectrum o f hepatitis viruses (including hepatitis A , B and delta viruses), recombinant human interferon a was a natural choice as a possible agent for the treatment o f non-A, non-B hepatitis. This led to a small pilot study which evaluated various doses of recombinant human interferon a (0.5 to 5 mill ion units) for 48 weeks in 10 patients with non-A, non-B hepatitis (166). A significant decline in A L T was observed in 8 of 10 subjects and a significant improvement in hepatic histology was documented in the 3 subjects having undergone liver biopsies. Interestingly, a 10 year follow-up study o f this cohort demonstrated that 5 of 10 patients had no detectable H C V R N A and had achieved an S V R after treatment (167). Although this response rate (50%) was higher than was seen in subsequent studies (12-16%), it could likely attributed be to the young age, mild to moderate degree of fibrosis and high proportion o f subjects infected with H C V genotypes 2/3, all o f which are factors associated with improved response to interferon a (168, 169). This led to a number of randomized controlled trials investigating the optimal dosing and duration o f interferon a for the treatment of chronic H C V infection (170, 171). Based on data from these studies and a meta-analysis o f randomized trials of interferon a (171), the first N I H Consensus Development Conference on Management of Hepatitis C , held in 1997, recommended standard interferon a at a dose of 3 mil l ion units three times a week for 48 weeks to be the standard treatment for chronic hepatitis C (172). However, S V R rates of only 12% to 16% were observed with this schedule (170), outlining a clear need to develop other therapies which could improve treatment outcomes. 1.4.2.2 Ribavirin Efforts to find other therapies to supplement interferon led to the testing of a number of investigational agents in humans, including the nucleoside analogue, ribavirin, known to have a broad spectrum of activity against many R N A and D N A viruses. The first clinical trial o f ribavirin was performed in 1991 (173) and significant reductions in A L T liver enzymes were observed, suggesting a biochemical response during ribavirin treatment. Unfortunately, 14 subsequent studies demonstrated that although ribavirin improved A L T levels, there was little impact on viral replication (174-176). Although this tempered initial enthusiasm for this drug, Brillanti and colleagues had already initiated a study to investigate the efficacy of interferon a in combination with ribavirin (177). Overall, 40% o f subjects receiving combination therapy with interferon a and ribavirin achieved an S V R , as compared to no subjects in the interferon a only arm. This landmark study had a major impact on the management of H C V infection. 1.4.2.3 Interferon-a and Ribavirin Combination Therapy These findings prompted the launch o f several randomized controlled trials to evaluate the efficacy of interferon a and ribavirin combination therapy (168, 169). Response rates of 38-43%) were achieved among subjects receiving 48 weeks of combination therapy as compared to only 13-19%o o f subjects receiving monotherapy with interferon a (168, 169). Although combination therapy with thrice-weekly standard interferon-a and daily ribavirin offered improved response rates over interferon a alone, the interferon component of the therapy remained problematic in many respects. Following subcutaneous injection, standard interferon-a is rapidly absorbed (absorption t m 2.3 hours), reaches peak plasma levels within 1-8 hours, is widely distributed throughout body fluids and tissues and rapidly metabolized and cleared by the kidney (178, 179). This leads to rapid elimination (elimination t m 3-8 hours) and undetectable concentrations in the serum within 24 hours of administration (178, 179). The pharmacokinetic properties o f interferon a certainly suggested that the thrice-weekly dosing regimen was sub-optimal, especially given that there are two consecutive days each week where patients have no detectable levels of the administered medication. Given that H C V has a high rate of replication (approximately 3.7 x 10" virions per day) (32), there is the potential for viral rebound and the development o f viral mutations leading to drug resistance in the presence of suboptimal drug concentrations. Wi th this in mind, pegylation technology was applied to improve the pharmacokinetics and pharmacodynamics of interferon a to avoid large fluctuations in serum concentrations and to improve the inconvenient dosing regimen. 15 1.4.3 Improving the Pharmacology of Interferon a and Ribavirin 1.4.3.1 Pharmacokinetics of Interferon a and Ribavirin Pegylated interferon a (peginterferon a) was developed by the conjugation of a polyethylene glycol (PEG) molecule to standard interferon a. Polyethylene glycol (PEG) is linear, uncharged, hydrophilic polymer with low toxicity and is non-immunogenic (180). The conjugation of polyethylene glycol (PEG) to standard interferon a results in a molecule with improved pharmacologic activity and increased half-life. There are currently two forms of peginterferon currently approved for the treatment o f H C V infection: peginterferon a2a (Pegasys, Hoffmann-L a Roche) and peginterferon a2b (Peg-Intron, Schering-Plough). These two forms of pegylated interferon differ somewhat in their pharmacokinetic properties. Peginterferon a2a is monopegylated and contains a 40 kDa branched P E G molecule, which can exist as four major positional isomers at the L y s 3 1 , L y s 1 2 1 , L y s 1 3 1 , L y s 1 3 4 positions of interferon a (181). In healthy volunteers, a single dose of 180 pg produces a mean maximum serum concentration ( C m a x ) of 14.2 pg/L, which is reached in a mean time ( T m a x ) of 78 hours (182). In patients with chronic H C V receiving multiple doses of peginterferon a2a (180 pg once-weekly), the C m a x and T m a x values are 25.6 pg/L and 45 hours, respectively (183). Peginterferon a2a demonstrates an increased absorption (50 hours vs. 2.3 hours) and elimination half-life (65 hours vs. 3-8 hours) as compared to standard interferon a2a (184). Five to eight weeks after the initiation of therapy, a steady state is achieved, and the ratio of serum peak to trough concentrations o f peginterferon a2a is about 1.5 to 2.0, indicative of sustained serum drug concentrations during the 1 week dosing interval. The mean terminal half-life is 80 hours, which is 16 times that of conventional interferon a2a (5.1 hours). After the completion of a 48 week course o f treatment with peginterferon a2a (180 pg once-weekly), it takes 4 to 6 weeks for serum concentrations to become undetectable (183). The bio-distribution is restricted, with the highest concentrations occurring in the liver (185). Clearance occurs via the kidney and the liver, although given the large size o f peginterferon a2a, it is primarily cleared by the liver. Peginterferon a2b is also monopegylated, but is covalently attached to a smaller, 12 k D a linear P E G molecule. Given the smaller size of the P E G chain, peginterferon a2b generally exists as one o f 14 monopegylated positional isomers attached to nucleophilic amino acids of interferon including lysine, serine, tyrosine, histidine and N-terminal cysteine (186). Similar to peginterferon a2a, peginterferon a2b has an improved mean absorption (4.6 hours vs. 2.3 hours) 16 and elimination half-life (40 hours vs. 4 hours) when compared to standard interferon a2b following a subcutaneous dose (187). Additionally, at therapeutic doses, peginterferon a2b demonstrates 10-fold greater peak levels than interferon a2b (187). The time required to reach peak serum concentrations o f peginterferon a2b ranges from 15 to 44 hours. These peak concentrations are generally sustained for up to 48 to 72 hours (187, 188). In patients with chronic H C V infection, the mean terminal half-life is 40 hours. Importantly, given that peginterferon a2b is widely distributed throughout the body fluids and tissues (volume o f distribution 1.4 L/kg) and their volume o f distribution is dependant on the individual's body weight, weight-based dosing is recommended (189). Renal clearance accounts for 30% of peginterferon a2b, with the remainder degraded through interactions with cellular interferon receptors or via the liver. Co-administration of peginterferon with ribavirin does not affect the pharmacokinetics of ribavirin. Similarly, there is no evidence to suggest that ribavirin influences the pharmacokinetics of pegylated interferon (188). In subjects treated with 600, 800 and 1000-1200 mg ribavirin daily (in combination with peginterferon a2b), the mean peak plasma ribavirin concentrations in week 1 were 741 ng/mL, 799 ng/mL and 1101 ng/mL, respectively. The T m a x occurred between 1 and 2 hours after dosing. Mean peak plasma ribavirin concentrations in week 4 were 1770 ng/mL, 2297 ng/mL and 2750 ng/mL for subjects treated with 600, 800 and 1000-1200 mg ribavirin daily (in combination with peginterferon a2b), respectively. Apparent ribavirin clearance appears to be consistent (23-26 L/h) across all dosing groups (188). These data illustrate that the pegylation o f both interferon a2a and cc2b have considerably improved the pharmacokinetic profile of both molecules. Additionally, there seems to be no pharmacologic interaction between peginterferon and ribavirin that would require adjustment of dosing regimens. However, there are subtle differences in the pharmacokinetic and pharmacodynamic properties o f each peginterferon molecule. Peginterferon a2b reaches peak concentrations more quickly when compared to peginterferon a2a, however, it is also cleared more rapidly and has a shorter absorption and elimination half-life. This results in more sustained serum concentrations o f peginterferon a2a over the dosing period when compared to peginterferon a2b. Pharmacodynamic data suggest that pegylated interferon a2b has greater activity as measured by interferon response gene profiling (186), which is supported by the only in vivo randomized comparison of these two agents without the addition of ribavirin (190). 17 However, similar response rates have been observed in clinical trials of these agents, bringing into question the clinical significance of their differing pharmacokinetic and pharmacodynamic profiles. 1.4.3.2 Pharmacodynamics of Interferon a and Ribavirin A n appreciation o f the pharmacodynamic effects of peginterferon and ribavirin requires an understanding of the H C V steady-state kinetics in chronically infected patients, which have been elucidated using mathematical models of viral decay during therapy with interferon a therapy (32). The liver o f an individual infected with H C V is composed o f infected and uninfected hepatocytes (Figure 1.4). Infected hepatocytes are the site of H C V replication and continuously produce virions, which pass into the peripheral circulation, to infect naive hepatocytes. Ce l l death of both infected and uninfected hepatocytes also occurs via apoptosis. In the liver and the periphery, circulating virions are continuously degraded via unknown mechanisms in immunologically protected compartments. Thus, during chronic infection with H C V , the steady-state viral kinetics are characterized by: 1) an equilibrium between the death of infected hepatocytes and the infection o f naive hepatocytes, leading to a pool size o f infected cells which remains constant; and 2) an equilibrium between the release of newly produced H C V viral particles into the peripheral circulation and their subsequent degradation, resulting in a H C V viral load which remains constant. With this in mind, the goal o f therapy for H C V infection is to alter this equilibrium by promoting the clearance of H C V infected cells and reducing H C V virion release into the peripheral blood. Once all infected cells have been cleared from the body, virologic cure is achieved. 18 ®2® Infected cell death INFECTED CELL DEATH N O N INFECTED CELL DEATH t t Infected Non infected hepatocytes hepatocytes Infected extra-hepatic cells PRODUCTION PRODUCTION DE NOVO INFECTION Non infected extra-hepatic cells Per ipheral blood ("viral load") DEGRADATION INFECTION Degradation compar tment N O N INFECTED CELL DEATH Figure 1.4 Steady-state H C V kinetics during chronic infection, based on mathematical modeling of viral decay during interferon alpha therapy (32). Mathematical modelling of the first phase of viral decline during therapy for H C V suggests that interferon a elicits its antiviral effects by directly inhibiting H C V viral replication (32). However, the absence of a suitable cell model precluded the confirmation of this hypothesis. In 1999, the development o f an in vitro subgenomic H C V replicon cell model (191) represented a major advance in the field and subsequent studies using this in vitro cell model demonstrated that interferon acted by directly inhibiting H C V replication (192-194). This led to further studies demonstrating a direct antiviral effect of interferon a on H C V replication in assays of virus productive cell cultures (29) and in primary cultures of normal human hepatocytes (195). However, the interferon-induced proteins and enzymatic pathways associated with the establishment of an antiviral state among infected and uninfected hepatocytes have not been completely elucidated (196). Interferon a is a cytokine which has extremely important functions in the innate antiviral immune response (196). The binding o f interferon a to cell-surface receptors activates a signalling cascade involving Janus-activated kinases, signal transduction, activation of various transcription factors and the induction of multiple interferon stimulating genes (197). This complex signalling cascade results in the induction o f host genes that encode 19 double-stranded RNases, inhibitors o f viral protein translation and proteins that destabilize viral messenger R N A . Interferon a also induces the expression o f genes involved in the immune response, resulting in the activation of natural killer cells, maturation of dendritic cells, proliferation of memory T cells and prevention of T-cell apoptosis (198). Mathematical modelling suggests that the second phase of viral decline during therapy with interferon a is a result of the clearance of infected hepatocytes from the peripheral circulation (32). However, it is unclear whether the immunomodulatory effects of interferon a are associated with increased clearance of hepatocytes or whether interferon a acts solely as a direct inhibitor of viral replication. Thus, the direct antiviral effects of interferon a remain elusive. The precise mechanisms of action of ribavirin during therapy for H C V infection are unclear. Ribavirin is a synthetic guanosine analogue, which is activated via intracellular phosphorylation to its active form, ribavirin triphosphate. However, interestingly, ribavirin only has a moderate and transient dose-dependent inhibitory effect on H C V replication in vivo (199). It has been demonstrated that the clinical effect o f ribavirin acts to decrease relapse in subjects responding to combination therapy with ribavirin and interferon a (200), which may be associated with a shortened half-life o f H C V infected cells in the presence of interferon a. However, a number of other mechanisms of action for ribavirin have been proposed. In vitro data suggests that ribavirin only has a minimal direct impact on H C V replication, by weakly inhibiting the H C V R N A -dependent R N A polymerase, which is required for the replication of H C V (201). Ribavirin also inhibits inosine monophosphate dehydrogenase ( IMPDH) , which may lead to the depletion of intracellular guanosine triphosphate (GTP), which is required for H C V viral R N A synthesis (202). Ribavirin may also have immune modulatory effects, shifting the balance between T-helper (Thl)/Th2 responses towards a T h l response (203), which is important in the eradication of H C V in both humans and chimpanzees (204). Lastly, evidence from mathematical modelling of H C V viral kinetics during interferon a and ribavirin combination therapy suggests that ribavirin may render H C V virions less infectious (205). Thus, ribavirin may act to decrease the de novo susceptibility of uninfected hepatocytes, while interferon a inhibits virus production. Interestingly, it has also been demonstrated that ribavirin is a R N A mutagen and may increase the rate at which random nucleotide mutations are incorporated into the viral genome during H C V replication (206). This may lead to a concept known as "error catastrophe", where there is a loss of viral fitness by the lethal accumulation of nucleotide mutations during H C V replication. However, no studies to date have demonstrated an increased mutagenesis o f H C V during therapy 20 with ribavirin (207, 208). These data suggest that ribavirin may act via a number of different mechanisms. Further research is required to fully understand the most important components attributable to the antiviral effect observed in the clinic. 1.4.4 Pegylated Interferon a and Ribavirin in Clinical Practice Combination therapy with peginterferon and ribavirin is the cornerstone for the current treatment of chronic H C V infection (Figure 1.5). A s previously mentioned, the most important therapeutic endpoint in subjects receiving combination therapy for chronic H C V infection is sustained virologic response (SVR) , which is defined by the absence o f detectable H C V R N A in the serum 6 months after the completion of therapy by an assay with a sensitivity of at least 100 copies per m L . In two large, randomized controlled trials, the rates of S V R after 48 weeks of treatment with peginterferon in combination with ribavirin were 54% and 56% as compared to 44% and 47% with standard interferon and ribavirin and only 29% with peginterferon alone (162, 209). 80n 60-m a © a. 9 OS "3 • i 40-54-61% 38-43% 45-47% 31-35% S 20-13-19% 6% C/j IFN I F N I F N / R B V I F N / R B V I F N / R B V P E G - I F N / R B V 24 wks 48 wks 24 wks 48 wks 48 wks 48 wks 1998 2001/2 Figure 1.5 Development of therapy for chronic hepatitis C virus infection (210). The S V R rates were much higher in individuals infected with H C V genotypes 2 or 3 and ranged from 76 to 84%), as compared to 42 to 52%o in those infected with genotype 1 (162, 209). In a subsequent study evaluating various regimens of peginterferon and ribavirin it was demonstrated that individuals infected with H C V genotype 2 or 3 only require 24 weeks of treatment, given similar S V R rates in those receiving 24 (81-84%) or 48 weeks (79-80%) of treatment (211). In addition to genotype, factors associated with an S V R include lower baseline viral load, lower 21 body weight, younger age and milder hepatic fibrosis (162, 209, 211). Understanding these characteristics associated with improved response rates to therapy have been important in the clinical management o f chronic H C V infection. 1.4.4.1 Predicting Response to Therapy Virologic testing for H C V infection has also become an important tool for not only the diagnosis of infection and the assessment o f response to treatment, but also for tailoring treatment for H C V based on the virologic response during therapy. H C V genotyping prior to the initiation of therapy provides an indication of the duration of therapy required, the dose of ribavirin and the virologic monitoring procedure (117). Based on the viral kinetics during therapy for H C V a number of virologic monitoring markers can be used to determine the response to treatment (Figure 1.6). Given that 70 to 80% of subjects infected with H C V genotype 2 or 3 wi l l respond to therapy, viral load monitoring is currently not indicated. However, in individuals infected with genotype 1, only 40-50% of subjects w i l l respond to therapy and virologic assessments prior to and during therapy can provide important information as to whether an individual w i l l respond to therapy. This allows the early discontinuation of treatment in those with a low chance of achieving an S V R , avoiding the toxicities and cost associated with the full duration of treatment. Vira l quantification is performed at baseline and at week 12 in order to better understand the viral kinetics of response to therapy (Figure 1.6). Among treated patients, one subset are null-responders who do not achieve an early virologic response ( E V R , undetectable or <2 log decrease in H C V viral load by week 12). Null-responders generally do not manifest further decreases in H C V viral load during continued therapy for 48 weeks and have almost no chance of achieving an S V R (212, 213). Treatment discontinuation is recommended in this group (117). The second subset of patients are partial responders who achieve a >2 log decrease in H C V viral load by week 12, which however continues to be detectable by week 24. Partial responders also have a low likelihood o f developing an S V R and treatment is generally discontinued (unless the goal of therapy is to slow the progression of disease in those with a poor prognosis) (213). The third subset of patients are termed relapsers, who achieve an end o f treatment response (ETR, defined as undetectable H C V R N A at the cessation of therapy), but do not go on to achieve an S V R . This occurs in only - 1 5 % of subjects that achieve an E T R . The final subset of patients are 22 those that are responders to therapy. Nearly always, this group achieves an E V R at 12 weeks and has a high likelihood of sustained response to therapy. ETR SVR i 0 i L ' i i i i i i i I i i I I i I I -8 -4 -2 0 4 8 12 16 2 0 24 32 40 48 52 60 72 Weeks After Start of Therapy Figure 1.6 Virologic response to interferon-based therapy. Emerging data suggest that among individuals with an E V R , there is a further group of "super responders" who achieve a rapid virologic response ( R V R ) or undetectable H C V R N A by week 4. It has been demonstrated that a rapid virologic response after 4 weeks of therapy is predictive of an S V R during therapy (214). Additionally, data are available to suggest that among individuals infected with genotypes 2 and 3, shorter treatment durations may be possible among subjects achieving an R V R by week 4 (215). Further prospective clinical trials evaluating this as a strategy for the treatment of H C V infection are required before this is routinely integrated into clinical practice. However, i f the duration of treatment could be shortened in some individuals, it would have a considerable impact on the management of H C V infection, allowing for therapy to be truncated in individuals experiencing side effects to therapy. 23 1.4.4.2 Adverse Events Adverse events affect virtually all patients who receive treatment. The most common side effects attributed to peginterferon include muscle aches and fatigue (162, 209, 211). Flu-like symptoms and cytopenias are also commonly observed. Interferon can also lead to neuropsychiatric side effects in those with and without pre-existing psychiatric disease, including depression, anxiety, irritability, sleep disturbance and difficulty concentrating (216-218). This can be managed with medications, such as selective serotonin re-uptake inhibitors (218, 219). Other common side include anorexia, nausea, skin rash, diarrhoea, arthralgias, headaches, dizziness, and paresthesias. Wi th respect to ribavirin, the most commonly reported adverse event is hemolysis, which may lead to clinically significant anemia (162, 209, 211). Ribavirin is also teratogenic, requiring strict adherence to birth control for both men and women receiving this drug. It is not known whether ribavirin is contained in sperm and i f it exerts teratogenic effects upon fertilization of the ova. However, because o f the potential human teratogenic effects of ribavirin, male patients should be advised to take every precaution to avoid risk o f pregnancy for their female partners. The majority of adverse events occurring with these agents subside after the cessation of treatment and can be managed with appropriate clinical monitoring during therapy. 1.4.4.3 Current Treatment Guidelines Given the available data, the current indications for the treatment o f H C V are based on statements from a Consensus Development Conference Panel of the National Institutes of Health and the Canadian Consensus Conference (117, 220). Persons with chronic H C V who are wil l ing to be treated and do not have any contraindications for therapy are candidates for treatment i f they have detectable H C V R N A in serum and evidence of chronic hepatitis (identified by elevations in serum alanine aminotransferase levels or the presence o f considerable necroinflammatory activity and fibrosis on biopsy). The currently recommended regimen for the treatment of H C V infection is weekly subcutaneous injections of peginterferon in combination with twice-daily oral doses of ribavirin (117, 220). The recommended dose of peginterferon a2a is 180 pg per week (209), and that of peginterferon a2b is 1.5 pg per kilogram of body weight per week (162). In Canadian guidelines, ribavirin dosing varies according to the regimen of peginterferon. Individuals infected with genotype 2 or 3 receiving peginterferon a2a should receive 800 mg of ribavirin, while individuals with H C V genotype 1 should receive weight-based dosing (1000 mg or 1200 mg). Individuals receiving peginterferon <x2b should receive weight-based dosing of ribavirin (800-1200 mg), regardless of genotype. Therapy duration is 24 dependant on genotype, with individuals infected with HCV genotype 2 or 3 requiring 24 weeks of therapy as compared to 48 weeks in individuals infected with HCV genotype 1. With respect to injection drug use, statements from both consensus conferences suggest that injection drug use should not be considered a contraindication for therapy and that in all cases the decision to treat must be individualized (117, 220). This represents a significant advance in the provision of treatment for IDUs. 1.5 The Treatment of Hepatitis C Virus Infection in Injection Drug Users 1.5.1 Barriers in the Treatment of HCV in IDUs The treatment of HCV-infected IDUs presents multiple challenges, such as co-morbid psychiatric disease, adherence to therapy, relapse of substance use, access to care and the potential for HCV re-infection (221). In 1997, guidelines recommended that IDUs not be offered HCV treatment until they had remained abstinent from all illicit drug use for > 6 months, raising some questions about fairness and discrimination (222). However, extensive evidence exists that, when specific needs-oriented programs are developed, IDUs can be successfully engaged in care (223-235). With respect to the treatment of HCV infection, it is important to recognize the barriers associated with treatment and develop individualized approaches for addressing these issues. Psychiatric disease is highly prevalent among IDUs (236-238). It has been suggested that since peginterferon is associated with significant neuropsychiatric side effects, including depression and anxiety (216-218), its administration in IDUs may exacerbate pre-existing depressive disorders in this population (216). However, several studies have shown that patients with depression can be treated safely and successfully while on treatment with interferon (217, 218, 239). Strategies for managing depressive symptoms in patients receiving therapy for HCV infection may include the prophylactic administration of antidepressants and psychiatric counseling. In one small pilot study, the prophylactic administration of the antidepressant, citalopram, was shown to significantly reduce the number of discontinuations due to major depression among psychiatric risk patients receiving therapy for HCV infection (240). 25 IDUs may also exhibit poor adherence to scheduled appointments and medication regimens (228, 230, 231, 241-243). However, this is a problem common to many chronic medical conditions (244, 245). In IDUs, strategies shown to improve adherence include directly-observed therapy (DOT), cash incentives, and comprehensive case management (223, 242, 243, 246-254). Weekly I F N dosing now provides a means o f improving H C V treatment adherence, and makes a D O T approach more practical (162). In the context of adherence and drug use, failure to achieve a high level of adherence necessary to achieve therapeutic success should be viewed as a flaw in the treatment program rather than a failure on the part of the patient. Therapy for H C V infection may place some IDUs at a risk of relapsing to injection drug use. The side effects of peginterferon therapy (sleeplessness, sweating, nausea, vomiting, fever, headache and pain) mimic opioid withdrawal symptoms. It has also been postulated that prescribing an injectable medication in IDUs may be thought to stimulate drug craving (255, 256). However, no study to date has documented a causal relationship between peginterferon injections and relapse to il l icit drug use (257). Moreover, increases in i l l ici t drug use during treatment for H C V have not been observed (258-260). On-site counseling and peer-support groups may be important in managing this component of H C V treatment. However, there are limited data on strategies for the prevention of relapse to il l icit drug use during therapy for H C V infection. Access to care may be difficult for HCV-infected IDUs seeking treatment. Up until recently, given that injection drug use was a contraindication for the treatment of H C V , very few clinics offered treatment to those continuing to use i l l ici t drugs. However, with the recent revision of consensus guidelines, there are a greater number of inner city clinics that are offering treatment for H C V infection. Using lessons learned from the field o f H I V , it is clear that by using the infrastructure for addiction treatment, IDUs can be successfully engaged in care for H C V . IDUs may also be at an increased risk of H C V re-infection and the perceived high risk of H C V re-infection is often cited as a reason to withhold treatment (255). Although re-infection has been described in several settings, it has been demonstrated in chimpanzees (108, 111) and in humans (73) that spontaneous clearance o f H C V may be protective against re-infection in some individuals. Whether this protection extends to individuals with clearance as a result of treatment 26 remains to be determined. However, in 18 IDUs responding to H C V therapy, no more than 2 (and possibly none) were found to be re-infected over a mean 33.8 month follow-up period (261). However, further research is required to confirm these findings in the setting of both natural and treatment induced clearance of viremia. If such protection extends to those who have cleared their viremia following antiviral therapy, it could provide a stronger rationale for expanding treatment programs to IDUs who continue to be at risk for H C V re-exposure. 1.5.2 H C V Treatment Uptake and Willingness Among IDUs Although most guidelines currently allow for the treatment of H C V infection in IDUs, support for this approach remains limited at best. In our centre, only 3.4% of 1,361 HCV-infected inner city residents evaluated in 2003-2004 reported having received treatment for H C V infection despite it being freely available to them (262). These results are similar to those reported in Australia, where only 4% of 2,500 current IDUs attending needle exchange programs in 2003 had been treated, with only 0.6% actually on treatment at the time of the survey (196). There are no data to suggest that higher treatment uptake should be expected in the United States and Europe. However, there is now mounting evidence current and former IDUs are interested in receiving treatment for H C V infection. In a survey conducted in 216 treatment-naive IDUs in three American cities, 82% were interested in receiving treatment for H C V infection, but only 27% had been given the opportunity to do so (263). Those who were told they were at risk for cirrhosis or liver cancer were 7 times more l ikely to be interested in receiving treatment. In Australia, a study of 100 IDUs documented an increase in motivation to be treated from 63% to 93% i f they were told there was a 70% chance o f the treatment being effective (264). In our centre, 40/50 (80%) expressed an interest in receiving treatment, probably driven by the fact that 76% felt their H C V has negatively impacted their health (265, 266). O f those interested in receiving H C V treatment, 15% had never been approached in this regard, their caregivers citing concerns about unstable drug use (100%), unstable housing (67%) and medical co-morbidities (33%). O f those who had been approached, only 23% had started treatment or were being considered for its initiation, due to lack of follow-up by the patient or physician (26%), non-adherence to pre-treatment appointments (9%), medical co-morbidities (12%), ongoing drug use (56%), unstable housing (21%) and ongoing alcohol use (12%). The majority (65%) had 27 multiple barriers to treatment. This largely parallels information reported in four separate studies of a total of 673 HCV-infected individuals in various inner city settings. Overall, only 5% or less received treatment and 60-72% (depending on the study) were deemed "ineligible" for treatment for reasons such as lack of follow-up with appointments and issues of medical or psychiatric co-morbidity or ongoing substance abuse (267-270). Taken as a whole, the current medical literature confirms a very low uptake o f H C V treatment in IDUs, despite the fact that the majority of current and past IDUs may be interested in receiving treatment, especially i f the issues are discussed in an appropriate context. In surveys of health care providers, the majority o f such patients are deemed ineligible for treatment (271), and this is often presented as the justification for why therapy is not even considered as part of the overall plan o f care. However, the exclusion criteria may often be barriers that can be overcome i f the appropriate structures are in place. Improved communication between patients and health care providers about the long-term potential risks o f chronic H C V infection and the high probability of treatment success in patients infected with viral genotypes that respond more favourably to treatment and the availability of strategies to overcome perceived impediments to a successful therapeutic partnership may be important in improving patient willingness and motivation to receive treatment. The evaluation o f each patient individually with all o f these factors in mind may be the key to the implementation o f optimal practices for the treatment of H C V infection in IDUs. 1.5.3 Treatment of HCV Infection in IDUs: Early Anecdotal Reports The first reports o f patients with a history of substance abuse receiving treatment for H C V infection were published in 1995 (272). Overall, 94% of the 31 previous drug users completed the 6 months of interferon a monotherapy and 28%> achieved an S V R , results similar to those reported in contemporary non-IDU populations. Little was published on this topic over the next 5-6 years, until the work of Backmund in 2001 (256). This was the first study to evaluate treatment for H C V infection in individuals continuing to engage in injection drug use. Patients were examined and treated by specialists in both addiction medicine and hepatology in the setting of an existing opiate detoxification unit. Fifty patients were offered self-administered treatment with interferon a2a (n=34) and interferon a2a 28 plus weight-based ribavirin (n=16), as it became available. H C V treatment was initiated during the final two weeks of detoxification treatment. In total, 36% of patients achieved an S V R (48% and 26% of patients infected with H C V genotypes 2/3 and genotype 1, respectively). These results were achieved despite the fact that 80% of patients relapsed back to il l icit drug use during treatment. Uncontrolled relapse did reduce response rates (24% S V R , vs. 53% S V R in those who subsequently enrolled in a methadone maintenance program). Overall, the factor most associated with success was not drug use per se, but adherence to treatment, in that attendance at greater than two-thirds of clinic visits was significantly associated with improved response rates (45% vs. 6%, p<0.05). In subsequent studies of approximately 100 patients with a history of substance use, S V R rates of 30-40% were reported (273-276). A l l of these data are encouraging, but still leave a significant gap in knowledge about the impact o f i l l icit drug use on H C V treatment outcomes. Information is now available from a study by Sylvestre and colleagues in patients enrolled in a methadone maintenance program and receiving H C V treatment in a community-based setting (258, 277). Seventy-six current and former IDUs at two sites in Oakland and New York received self-administered interferon a2b plus ribavirin. A t baseline, 59% of patients reported a previous psychiatric diagnosis, 60% were infected with H C V genotype 1, the mean abstinence from ill ici t drug use was one year (range 0-18 years, 30% < 6 months). A n E T R was achieved in 49%, and an S V R in 28% of patients. These results were achieved despite the fact that 59% of patients engaged in il l icit drug use during treatment. In this study, the duration o f pre-treatment abstinence from ill ici t drug use was not statistically associated with response rates, nor was intercurrent drug use during therapy, although 0 of 8 individuals with every day/other day drug use responded to treatment. This suggests that occasional drug use does not significantly impact response rates, but an individual threshold effect may be present. In this context, a study was conducted in a hospital-based setting in Australia in which 12 active IDUs received treatment with either interferon or peginterferon with or without ribavirin (278). In most cases (11/12), drug use occurred at least every week. The E T R and S V R rates were 58% (7/12) and 50% (6/12). In 50 patients enrolled in a methadone maintenance program and receiving H C V treatment, 11 discontinued therapy within the first 8 weeks due to non-adherence (260). O f the remaining 39, 90% then went on to complete treatment with a 54% S V R . This 29 suggests that we should invest resources in patient support within the first 1-2 months of treatment to maximize the likelihood of success. Overall, S V R rates o f 29% to 50% have been observed among current and former IDUs. From these studies a number o f important themes have emerged. First, the treatment o f H C V infection in current and former IDUs is both safe and effective when incorporated into an existing infrastructure for the treatment of addiction (256, 258, 260, 279). Second, H C V treatment can be successful even for individuals continuing to engage in ill icit drug use, although more frequent use may be associated with poorer outcomes (258, 278). Lastly, H C V treatment does not have a significant impact on drug dependency treatment requirements or lead to increased injection drug use (258-260). It is important to note, however, that the majority of these studies were conducted prior to the availability of peginterferon and some included interferon monotherapy regimens. Further studies investigating the treatment of H C V in current and former drug users with newer combinations of peginterferon are needed. Moreover, it w i l l be important to identify novel strategies for improving treatment uptake and outcomes in this population. This may include the use of opiate dependence treatments, such as methadone and buprenorphine, as a method of engaging subjects in care for H C V treatment. Several studies have shown encouraging results using these strategies (256, 280). Also , studies investigating novel models for the delivery o f H C V treatment are urgently needed in order to enhance adherence and improve outcomes during therapy. Lastly, given the importance of patient support during therapy, research is needed to understand methods for improving the uptake of treatment in IDUs and novel models for improving engagement in care. Since the first tentative reports a decade ago, there is now a growing confidence that, in certain settings, IDUs can be successfully treated for H C V infection. The key w i l l be to develop systematic programs for the evaluation and follow-up of these individuals to ensure engagement in care before, during and after a decision to initiate treatment has been made. 30 1.6 Summary Globally, there continues to be a high prevalence and incidence of H C V infection. The current H C V epidemic in developed countries is almost entirely fueled by IDUs. Following infection, a quarter of individuals w i l l spontaneously clear their infection. However, the majority w i l l develop chronic, persistent infection and be at risk for significant morbidity and mortality. Although some factors associated with viral clearance have been identified, it is not clear whether additional environmental factors among IDUs wi l l impact their ability to resolve infection, including continued exposure to the virus through ongoing injection drug use. Following the development of chronic H C V infection, the progression o f liver-disease wi l l occur slowly but inexorably over time. Without treatment, a significant subset of those w i l l develop cirrhosis, which may culminate in the development of end-stage liver disease, hepatocellular carcinoma or death. Although a number of host and viral factors are important in determining how quickly the progression of hepatic fibrosis w i l l occur, poorly understood host-related factors also contribute significantly to disease progression. H C V is unlike other chronic viral infections such as H I V , in that a cure is possible with currently available regimens o f once-weekly peginterferon injections and twice-daily ribavirin pills. Although treatment response depends on the H C V genotype that an individual carries, overall response rates are - 8 0 % in a subset of individuals infected with genotypes 2 and 3. Despite the considerable burden o f H C V infection among those that use injection drugs, treatment has often been denied from this group on the basis that a number o f barriers to therapy, including a low perceived adherence to therapy, H C V re-infection and a lack of interest in receiving treatment, would yield poor response rates in this population. A s such, there has been an extremely low uptake of treatment for H C V infection in this population. There is now a growing body of knowledge which demonstrates that when IDUs are offered treatment for H C V , results similar to large, randomized trials for the treatment of H C V among subjects without addiction can be achieved. 31 1.7 Key Gaps Before we embark on public health initiatives focused on expanding access to treatment for H C V infection among IDUs, there are a number of gaps that exist in the body of knowledge surrounding H C V infection in IDUs and several important questions that must be answered. Very little is known about the natural history of H C V in IDUs. Specifically, do IDUs clear H C V infection at the same rate as non-IDUs and what are the factors associated with spontaneous viral clearance? In those that spontaneously clear H C V infection, do IDUs become re-infected with H C V i f they continue to be exposed as a result of ongoing injection drug use? There are limited human data in this regard, although chimpanzee studies suggest that protective immunity against H C V may be possible. If this extends to individuals that clear infection following treatment, it would have important implications for the treatment of H C V in IDUs. Further, i f we do embark on treatment in this group, w i l l IDUs respond at the same rates that are observed in non-IDUs and what factors are associated with successful response to therapy? There is limited experience with novel formulations o f peginterferon and ribavirin in IDUs and a paucity of data on the impact of il l icit drug use during therapy for H C V . Importantly, as we refine programs for the treatment of H C V in IDUs, what are the specific components that are required to ensure that higher levels of success can be achieved? Understanding strategies for enhancing engagement in care for H C V and improving adherence during therapy w i l l be essential i f treatment is to be successful in IDUs. With this in mind, the focus of this thesis is to characterize spontaneous clearance of H C V , evaluate H C V re-infection following spontaneous clearance and to evaluate novel models for improving uptake and treatment responses among IDUs. Taken together, these findings represent an important contribution to the field and provide important guidance for the development of health policy with respect to H C V infection in IDUs. 32 1.8 Purpose and Specific Aims I chose to work towards a better understanding of H C V infection in IDUs through 4 specific aims: > 1) To determine the rate and characteristics of spontaneous clearance of H C V among infected individuals enrolled in a large, community-based cohort in Vancouver. > 2) To determine whether spontaneous clearance of H C V is protective against H C V re-infection. > 3) To evaluate the antiviral efficacy of interferon a-2b or pegylated interferon a-2b in combination with ribavirin among IDUs enrolled in a directly observed therapy program, as measured by sustained virologic response. > 4) To evaluate the uptake and response to treatment among current and former IDUs infected with H C V enrolled in a novel, weekly support group designed to enhance long-term engagement in medical care. 33 1.9 References 1. Lurman A. Eine icterus Epidemic. Berlin K l in Wochenschr 1855;22:20-23. 2. Flaum A , Malmros H , Perrson E. Eine nosocomiale icterus-epidemic. Acta Med Scand 1926;16:544. 3. Neefe JR, Gellis JJ, Stokes J. Homologous serum hepatitis and infectious hepatitis: studies in volunteers bearing on immunological and other characteristics of etiologic agents. Am J Med 1946; 1:3-22. 4. MacCallum FO, Bauer DJ. Homologous serum hepatitis. Lancet 1947;ii:691-692. 5. Alter HJ, Purcell R H , Shih JW, Melpolder JC, Houghton M , Choo QL, Kuo G. Detection of antibody to hepatitis C virus in prospectively followed transfusion recipients with acute and chronic non-A, non-B hepatitis. N Engl J Med 1989;321:1494-1500. 6. Choo QL, Kuo G, Weiner A J , Overby LR, Bradley DW, Houghton M . Isolation of a c D N A clone derived from a blood-borne non-A, non-B viral hepatitis genome. Science 1989;244:359-362. 7. Reyes GR, Purdy M A , Kim JP, Luk K C , Young L M , Fry K E , Bradley DW. Isolation of a cDNA from the virus responsible for enterically transmitted non-A, non-B hepatitis. Science 1990;247:1335-1339. 8. Perz JF, Farrington L A , Pecoraro C, Hutin YJF, Armstrong G L . Estimated global prevalence of hepatitis C virus infection. In: Program and Abstracts of the 42nd Annual Meeting of the Infectious Diseases Society of America; 2004 Sept 30-Oct 3; Boston, M A , USA; 2004. 9. Remis R. A study to characterize the epidemiology of hepatitis C infection in Canada, 2002. Final Report. Ottawa: Health Canada; 2004. 10. Shepard CW, Finelli L , Alter M J . Global epidemiology of hepatitis C virus infection. Lancet Infect Dis 2005;5:558-567. 11. Dore GJ, Law M , MacDonald M , Kaldor J M . Epidemiology of hepatitis C virus infection in Australia. J Clin Virol 2003;26:171-184. 12. Armstrong GL, Wasley A , Simard EP, McQuillan G M , Kuhnert W L , Alter MJ . The prevalence of hepatitis C virus infection in the United States, 1999 through 2002. Ann Intern Med 2006;144:705-714. 13. Patrick D M , Tyndall M W , Cornelisse PG, L i K, Sherlock C H , Rekart M L , Strathdee SA, et al. Incidence of hepatitis C virus infection among injection drug users during an outbreak of HIV infection. C M A J 2001;165:889-895. 14. Zou S, Tepper M , Giulivi A . Current status of hepatitis C in Canada. Can J Public Health 2000; 91 Suppl LS10-15, S10-16. 15. Dalgard O, Jeansson S, Skaug K , Raknerud N , Bell H . Hepatitis C in the general adult population of Oslo: prevalence and clinical spectrum. Scand J Gastroenterol 2003;38:864-870. 34 16. Mele A , Tosti M E , Marzolini A , Moiraghi A , Ragni P, Gallo G, Balocchini E, et al. Prevention of hepatitis C in Italy: lessons from surveillance of type-specific acute viral hepatitis. SEIEVA collaborating Group. J Viral Hepat 2000;7:30-35. 17. Wu H X , Wu J, Wong T, Donaldson T, Dinner K , Andonov A, Ip Chan J, et al. Enhanced surveillance of newly acquired H C V infection in Canada, 1998 to 2004. Scand J Infect Dis 2006;38:482-489. 18. Robotin M C , Copland J, Tallis G, Coleman D, Giele C, Carter L, Spencer J, et al. Surveillance for newly acquired hepatitis C in Australia. J Gastroenterol Hepatol 2004;19:283-288. 19. Thomas DL, Vlahov D, Solomon L, Cohn S, Taylor E, Garfein R, Nelson K E . Correlates of hepatitis C virus infections among injection drug users. Medicine (Baltimore) 1995;74:212-220. 20. Coppola RC, Masia G, di Martino M L , Carboni G, Muggianu E, Piro R, Manconi PE. Sexual behaviour and multiple infections in drug abusers. Eur J Epidemiol 1996;12:429-435. 21. Garfein RS, Doherty M C , Monterroso ER, Thomas DL, Nelson K E , Vlahov D. Prevalence and incidence of hepatitis C virus infection among young adult injection drug users. J Acquir Immune Defic Syndr Hum Retroviral 1998; 18 Suppl 1: S11 -19. 22. Hagan H , Thiede H , Weiss NS, Hopkins SG, Duchin JS, Alexander ER. Sharing of drug preparation equipment as a risk factor for hepatitis C. Am J Public Health 2001;91:42-46. 23. Garfein RS, Vlahov D, Galai N , Doherty M C , Nelson K E . Viral infections in short-term injection drug users: the prevalence of the hepatitis C, hepatitis B , human immunodeficiency, and human T-lymphotropic viruses. A m J Public Health 1996;86:655-661. 24. Diaz T, Des Jarlais DC, Vlahov D, Perlis TE, Edwards V , Friedman SR, Rockwell R, et al. Factors associated with prevalent hepatitis C: differences among young adult injection drug users in lower and upper Manhattan, New York City. Am J Public Health 2001 ;91:23-30. 25. Wood E, Kerr T, Stoltz J, Qui Z, Zhang R, Montaner JS, Tyndall M W . Prevalence and correlates of hepatitis C infection among users of North America's first medically supervised safer injection facility. Public Health 2005; 119:1111-1115. 26. Miller C L , Spittal P M , Frankish JC, L i K , Schechter MT, Wood E. HIV and hepatitis C outbreaks among high-risk youth in Vancouver demands a public health response. Can J Public Health 2005;96:107-108. 27. Page-Shafer K , Lum P, Hahn J, Evans J, Cooper S, Tobler L , Andrews W, et al. Effective Detection of Acute Hepatitis C Infection Using R N A Screening and Antibody Testing in Young Injectors in San Francisco: The UFO Study. In: Program and Abstracts of the 13th Conference on Retroviruses and Opportunistic Infections; 2006; Denver, CO, USA; 2006. 28. Lauer G M , Walker BD. Hepatitis C virus infection. N Engl J Med 2001;345:41-52. 29. Lindenbach B D , Rice C M . Unravelling hepatitis C virus replication from genome to function. Nature 2005;436:933-938. 35 30. Deforges S, Evlashev A , Perret M , Sodoyer M , Pouzol S, Scoazec JY, Bonnaud B , et al. Expression of hepatitis C virus proteins in epithelial intestinal cells in vivo. J Gen Virol 2004;85:2515-2523. 31. Forton D M , Karayiannis P, Mahmud N , Taylor-Robinson SD, Thomas HC. Identification of unique hepatitis C virus quasispecies in the central nervous system and comparative analysis of internal translational efficiency of brain, liver, and serum variants. J Virol 2004;78:5170-5183. 32. Neumann A U , Lam NP, Dahari H , Gretch DR, Wiley TE, Layden TJ, Perelson AS. Hepatitis C viral dynamics in vivo and the antiviral efficacy of interferon-alpha therapy. Science 1998;282:103-107. 33. Simmonds P, Bukh J, Combet C, Deleage G, Enomoto N , Feinstone S, Halfon P, et al. Consensus proposals for a unified system of nomenclature of H C V genotypes. Hepatology 2005;42:962-973. 34. Simmonds P. Viral heterogeneity of the hepatitis C virus. J Hepatol 1999;31 Suppl 1:54-60. 35. Alter MJ , Kruszon-Moran D, Nainan OV, McQuillan G M , Gao F, Moyer L A , Kaslow R A , et al. The prevalence of hepatitis C virus infection in the United States, 1988 through 1994. N Engl J Med 1999;341:556-562. 36. Blatt L M , Mutchnick M G , Tong MJ , Klion F M , Lebovics E, Freilich B, Bach N , et al. Assessment of hepatitis C virus R N A and genotype from 6807 patients with chronic hepatitis C in the United States. J Viral Hepat 2000;7:196-202. 37. Nainan OV, Alter MJ , Kruszon-Moran D, Gao F X , Xia G, McQuillan G, Margolis HS. Hepatitis C virus genotypes and viral concentrations in participants of a general population survey in the United States. Gastroenterology 2006; 131:478-484. 38. Chaudhary R X , Tepper M , Eisaadany S, Gully PR. Distribution of hepatitis C virus genotypes in Canada: Results from the L C C D C Sentinal Health Unit Surveillance System. Can J Infect Dis 1999;10:53-56. 39. van Asten L, Verhaest I, Lamzira S, Hernandez-Aguado I, Zangerle R, Boufassa F, Rezza G, et al. Spread of hepatitis C virus among European injection drug users infected with HIV: a phylogenetic analysis. J Infect Dis 2004;189:292-302. 40. Pawlotsky J M , Tsakiris L , Roudot-Thoraval F, Pellet C, Stuyver L , Duval J, Dhumeaux D. Relationship between hepatitis C virus genotypes and sources of infection in patients with chronic hepatitis C. J Infect Dis 1995;171:1607-1610. 41. Bourliere M , Barberin JM, Rotily M , Guagliardo V , Portal I, Lecomte L, Benali S, et al. Epidemiological changes in hepatitis C virus genotypes in France: evidence in intravenous drug users. J Viral Hepat 2002;9:62-70. 42. Altamirano M , Delaney A , Wong A, Marostenmaki J, Pi D. Identification of hepatitis C virus genotypes among hospitalized patients in British Columbia, Canada. J Infect Dis 1995;171:1034-1038. 43. Chaudhary R, Tepper, M , Eisaadany, S, Gully, PR. Distribution of hepatitis c virus (HCV) genotypes in Canada: Results from the L C D C Sentinel Health Unit Surveillance System. Can J Infect Dis 1999;10:53-56. 36 44. Grebely J, Conway B, Raffa J, Lai C, Krajden M , Tyndall M . High prevalence of hepatitis C virus (HCV) genotype 3 infection among injection drug users in Vancouver, Canada [Abstract 35]. Can J Gastroenterol 2006;20:200. 45. Busch MP. Insights into the epidemiology, natural history and pathogenesis of H C V infection from studies of infected donors and blood product recipients. Transfus Clin Biol 2001;8:200-206. 46. Prince A M , Pawlotsky JM, Soulier A , Tobler L , Brotman B, Pfahler W, Lee D H , et al. Hepatitis C virus replication kinetics in chimpanzees with self-limited and chronic infections. J Viral Hepat 2004;11:236-242. 47. Cox A L , Netski D M , Mosbruger T, Sherman SG, Strathdee S, Ompad D, Vlahov D, et al. Prospective evaluation of community-acquired acute-phase H C V infection. Clin Infect Dis 2005;40:951-958. 48. Orland JR, Wright TL, Cooper S. Acute hepatitis C. Hepatology 2001 ;33:321-327. 49. Marcellin P. Hepatitis C: the clinical spectrum of the disease. J Hepatol 1999;31 Suppl 1:9-16. 50. Alter HJ, Sanchez-Pescador R, Urdea M S , Wilber JC, Lagier RJ, D i Bisceglie A M , Shih JW, et al. Evaluation of branched D N A signal amplification for the detection of hepatitis C virus RNA. J Viral Hepat 1995;2:121-132. 51. Farci P, Alter HJ, Wong D, Miller R H , Shih JW, Jett B, Purcell R H . A long-term study of hepatitis C virus replication in non-A, non-B hepatitis. N Engl J Med 1991;325:98-104. 52. Abe K , Inchauspe G, Shikata T, Prince A M . Three different patterns of hepatitis C virus infection in chimpanzees. Hepatology 1992;15:690-695. 53. Beach M J , Meeks EL, Mimms LT, Vallari D, DuCharme L, Spelbring J, Taskar S, et al. Temporal relationships of hepatitis C virus R N A and antibody responses following experimental infection of chimpanzees. J Med Virol 1992;36:226-237. 54. Lechner F, Gruener N H , Urbani S, Uggeri J, Santantonio T, Kammer A R , Cerny A , et al. CD8+ T lymphocyte responses are induced during acute hepatitis C virus infection but are not sustained. Eur J Immunol 2000;30:2479-2487. 55. Lechner F, Wong DK, Dunbar PR, Chapman R, Chung RT, Dohrenwend P, Robbins G, et al. Analysis of successful immune responses in persons infected with hepatitis C virus. J Exp Med 2000;191:1499-1512. 56. Gerlach JT, Diepolder H M , Zachoval R, Gruener N H , Jung M C , Ulsenheimer A , Schraut WW, et al. Acute hepatitis C: high rate of both spontaneous and treatment-induced viral clearance. Gastroenterology 2003;125:80-88. 57. Thimme R, Oldach D, Chang K M , Steiger C, Ray SC, Chisari FV . Determinants of viral clearance and persistence during acute hepatitis C virus infection. J Exp Med 2001;194:1395-1406. 58. Diepolder H M , Zachoval R, Hoffmann R M , Wierenga EA, Santantonio T, Jung M C , Eichenlaub D, et al. Possible mechanism involving T-lymphocyte response to non-structural protein 3 in viral clearance in acute hepatitis C virus infection. Lancet 1995;346:1006-1007. 37 59. Missale G, Bertoni R, Lamonaca V , Vall i A , Massari M , Mori C, Rumi M G , et al. Different clinical behaviors of acute hepatitis C virus infection are associated with different vigor of the anti-viral cell-mediated immune response. J Clin Invest 1996;98:706-714. 60. Tsai SL, Huang SN. T cell mechanisms in the immunopathogenesis of viral hepatitis B and C. J Gastroenterol Hepatol 1997;12:S227-235. 61. Gerlach JT, Diepolder H M , Jung M C , Gruener N H , Schraut WW, Zachoval R, Hoffmann R, et al. Recurrence of hepatitis C virus after loss of virus-specific CD4(+) T-cell response in acute hepatitis C. . Gastroenterology 1999;117:933-941. 62. Zhang M , Rosenberg PS, Brown DL, Preiss L , Konkle B A , Eyster M E , Goedert JJ. Correlates of spontaneous clearance of hepatitis C virus among people with hemophilia. Blood 2006;107:892-897. 63. Strasfeld L , Lo Y , Netski D, Thomas DL , Klein RS. The association of hepatitis C prevalence, activity, and genotype with HIV infection in a cohort of New York City drug users. J Acquir Immune Defic Syndr 2003;33:356-364. 64. Piasecki B A , Lewis JD, Reddy K R , Bellamy SL, Porter SB, Weinrieb R M , Stieritz DD, et al. Influence of alcohol use, race, and viral coinfections on spontaneous H C V clearance in a US veteran population. Hepatology 2004;40:892-899. 65. Kenny-Walsh E. Clinical outcomes after hepatitis C infection from contaminated anti-D immune globulin. Irish Hepatology Research Group. N Engl J Med 1999;340:1228-1233. 66. Alric L , Fort M , Izopet J, Vinel JP, Bureau C, Sandre K , Charlet JP, et al. Study of host- and virus-related factors associated with spontaneous hepatitis C virus clearance. Tissue Antigens 2000;56:154-158. 67. Inoue G, Horiike N , Michitaka K , Onji M . Hepatitis C virus clearance is prominent in women in an endemic area. J Gastroenterol Hepatol 2000;15:1054-1058. 68. Yamakawa Y , Sata M , Suzuki H , Noguchi S, Tanikawa K . Higher elimination rate of hepatitis C virus among women. J Viral Hepat 1996;3:317-321. 69. Micallef J M , Kaldor J M , Dore GJ. Spontaneous viral clearance following acute hepatitis C infection: a systematic review of longitudinal studies. J Viral Hepat 2006; 13:34-41. 70. Thomas D L , Astemborski J, Rai R M , Anania FA, Schaeffer M , Galai N , Nolt K , et al. The natural history of hepatitis C virus infection: host, viral, and environmental factors. J A M A 2000;284:450-456. 71. Villano SA, Vlahov D, Nelson K E , Cohn S, Thomas DL. Persistence of viremia and the importance of long-term follow-up after acute hepatitis C infection. Hepatology 1999;29:908-914. 72. Farci P, Shimoda A , Coiana A , Diaz G, Peddis G, Melpolder JC, Strazzera A , et al. The outcome of acute hepatitis C predicted by the evolution of the viral quasispecies. Science 2000;288:339-344. 73. Mehta SH, Cox A , Hoover DR, Wang X H , Mao Q, Ray S, Strathdee SA, et al. Protection against persistence of hepatitis C. Lancet 2002;359:1478-1483. 74. Shoukry N H , Cawthon A G , Walker C M . Cell-mediated immunity and the outcome of hepatitis C virus infection. Annu Rev Microbiol 2004;58:391-424. 38 75. Grakoui A , Shoukry N H , Woollard DJ, Han JH, Hanson H L , Ghrayeb J, Murthy K K , et al. H C V persistence and immune evasion in the absence of memory T cell help. Science 2003;302:659-662. 76. Cooper S, Erickson A L , Adams EJ, Kansopon J, Weiner AJ , Chien D Y , Houghton M , et al. Analysis of a successful immune response against hepatitis C virus. Immunity 1999;10:439-449. 77. Shoukry N H , Grakoui A , Houghton M , Chien D Y , Ghrayeb J, Reimann K A , Walker C M . Memory CD8+ T cells are required for protection from persistent hepatitis C virus infection. J Exp Med 2003;197:1645-1655. 78. Aach RD, Stevens CE, Hollinger FB, Mosley JW, Peterson DA, Taylor PE, Johnson RG, et al. Hepatitis C virus infection in post-transfusion hepatitis. An analysis with first- and second-generation assays. N Engl J Med 1991;325:1325-1329. 79. Vogt M , Lang T, Frosner G, Klingler C, Sendl AF, Zeller A , Wiebecke B, et al. Prevalence and clinical outcome of hepatitis C infection in children who underwent cardiac surgery before the implementation of blood-donor screening. N Engl J Med 1999;341:866-870. 80. Wiese M , Berr F, Lafrenz M , Porst H , Oesen U . Low frequency of cirrhosis in a hepatitis C (genotype lb) single-source outbreak in germany: a 20-year multicenter study. Hepatology 2000;32:91-96. 81. Messick K , Sanders JC, Goedert JJ, Eyster M E . Hepatitis C viral clearance and antibody reactivity patterns in persons with haemophilia and other congenital bleeding disorders. Haemophilia 2001;7:568-574. 82. Minuk G Y , Zhang M , Wong SG, Uhanova J, Bernstein C N , Martin B, Dawood MR, et al. Viral hepatitis in a Canadian First Nations community. Can J Gastroenterol 2003;17:593-596. 83. Minuk G Y , Uhanova J. Viral hepatitis in the Canadian Inuit and First Nations populations. Can J Gastroenterol 2003;17:707-712. 84. Scott JD, McMahon BJ, Bruden D, Sullivan D, Homan C, Christensen C, Gretch DR. High rate of spontaneous negativity for hepatitis C virus R N A after establishment of chronic infection in Alaska Natives. Clin Infect Dis 2006;42:945-952. 85. Thio C L , Goedert JJ, Mosbruger T, Vlahov D, Strathdee SA, O'Brien SJ, Astemborski J, et al. An analysis of tumor necrosis factor alpha gene polymorphisms and haplotypes with natural clearance of hepatitis C virus infection. Genes Immun 2004;5:294-300. 86. Thio C L , Gao X , Goedert JJ, Vlahov D, Nelson K E , Hilgartner M W , O'Brien SJ, et al. HLA-Cw*04 and hepatitis C virus persistence. J Virol 2002;76:4792-4797. 87. Thio C L , Thomas DL, Goedert JJ, Vlahov D, Nelson K E , Hilgartner M W , O'Brien SJ, et al. Racial differences in H L A class II associations with hepatitis C virus outcomes. J Infect Dis 2001;184:16-21. 88. Barrett S, Ryan E, Crowe J. Association of the HLA-DRB1*01 allele with spontaneous viral clearance in an Irish cohort infected with hepatitis C virus via contaminated anti-D immunoglobulin. J Hepatol 1999;30:979-983. 3 9 89. Thursz M , Yallop R, Goldin R, Trepo C, Thomas HC. Influence of M H C class II genotype on outcome of infection with hepatitis C virus. The HENCORE group. Hepatitis C European Network for Cooperative Research. Lancet 1999;354:2119-2124. 90. Oleksyk TK, Thio C L , Truelove A L , Goedert JJ, Donfield S M , Kirk GD, Thomas DL, et al. Single nucleotide polymorphisms and haplotypes in the IL10 region associated with H C V clearance. Genes Immun 2005;6:347-357. 91. Khakoo SI, Thio C L , Martin M P , Brooks CR, Gao X , Astemborski J, Cheng J, et al. H L A and N K cell inhibitory receptor genes in resolving hepatitis C virus infection. Science 2004;305:872-874. 92. Lio D, Caruso C, D i Stefano R, Colonna Romano G, Ferraro D, Scola L , Crivello A , et al. IL-10 and TNF-alpha polymorphisms and the recovery from H C V infection. Hum Immunol 2003;64:674-680. 93. Khatkar S A K , Kaita K and Rempel JD. The impact of H C V core and NS3 proteins on Aboriginal and Caucasian P B M C IL-10 production in response to IFN-a. In: 18th Annual Spring meeting of Canadian Society for Immunology; 2005; Whistler, Canada.; 2005. 94. Knapp S, Yee LJ , Frodsham A J , Hennig BJ, Hellier S, Zhang L , Wright M , et al. Polymorphisms in interferon-induced genes and the outcome of hepatitis C virus infection: roles of M x A , OAS-1 and PKR. Genes Immun 2003;4:411-419. 95. McKiernan SM, Hagan R, Curry M , McDonald GS, Kelly A , Nolan N , Walsh A, et al. Distinct M H C class I and II alleles are associated with hepatitis C viral clearance, originating from a single source. Hepatology 2004;40:108-114. 96. Minton EJ, Smillie D, Neal K R , Irving W L , Underwood JC, James V . Association between M H C class II alleles and clearance of circulating hepatitis C virus. Members of the Trent Hepatitis C Virus Study Group. J Infect Dis 1998;178:39-44. 97. Spada E, Mele A, Berton A, Ruggeri L , Ferrigno L, Garbuglia AR, Perrone MP, et al. Multispecific T cell response and negative H C V R N A tests during acute H C V infection are early prognostic factors of spontaneous clearance. Gut 2004;53:1673-1681. 98. Alter HJ, Conry-Cantilena C, Melpolder J, Tan D, Van Raden M , Herion D, Lau D, et al. Hepatitis C in asymptomatic blood donors. Hepatology 1997;26:29S-33S. 99. Seeff L B , Hollinger FB, Alter HJ, Wright EC, Cain C M , Buskell ZJ, Ishak K G , et al. Long-term mortality and morbidity of transfusion-associated non-A, non-B, and type C hepatitis: A National Heart, Lung, and Blood Institute collaborative study. Hepatology 2001;33:455-463. 100. Ugen K E , Nyland SB. Injecting drugs of abuse and immunity: implications for HIV vaccine testing and efficacy. Springer Semin Immunopathol 2006;28:281-287. 101. Jauncey M , Micallef J M , Gilmour S, Amin J, White PA, Rawlinson W, Kaldor J M , et al. Clearance of hepatitis C virus after newly acquired infection in injection drug users. J Infect Dis 2004; 190:1270-1274. 40 102. Lai M E , Mazzoleni AP, Argiolu F, De Virgilis S, Balestrieri A , Purcell R H , Cao A , et al. Hepatitis C virus in multiple episodes of acute hepatitis in polytransfused thalassaemic children. Lancet 1994;343:388-390. 103. Tisone G, Baiocchi L , Orlando G, Palmieri GP, Pisani F, Rapicetta M , Strati F, et al. Hepatitis C reinfection after liver transplantation in relation to virus genotype. Transplant Proc 1999;31:490-491. 104. Proust B, Dubois F, Bacq Y , Le Pogam S, Rogez S, Levillain R, Goudeau A. Two successive hepatitis C virus infections in an intravenous drug user. J Clin Microbiol 2000;38:3125-3127. 105. Payen JL, Izopet J, Barange K , Puel J, Selves J, Pascal JP. [Hepatitis C virus reinfection after an intravenous drug injection]. Gastroenterol Clin Biol 1998;22:469-470. 106. Asselah T, Vidaud D, Doloy A , Boyer N , Martinot M , Vidaud M , Valla D, et al. Second infection with a different hepatitis C virus genotype in a intravenous drug user during interferon therapy. Gut 2003;52:900-902. 107. Major M E , Dahari H , Mihalik K , Puig M , Rice C M , Neumann A U , Feinstone S M . Hepatitis C virus kinetics and host responses associated with disease and outcome of infection in chimpanzees. Hepatology 2004;39:1709-1720. 108. Farci P, Alter HJ, Govindarajan S, Wong DC, Engle R, Lesniewski RR, Mushahwar DC, et al. Lack of protective immunity against reinfection with hepatitis C virus. Science 1992;258:135-140. 109. Nascimbeni M , Mizukoshi E, Bosmann M , Major M E , Mihalik K , Rice C M , Feinstone SM, et al. Kinetics of CD4+ and CD8+ memory T-cell responses during hepatitis C virus rechallenge of previously recovered chimpanzees. J Virol 2003;77:4781-4793. 110. Lanford RE, Guerra B, Chavez D, Bigger C, Brasky K M , Wang X H , Ray SC, et al. Cross-genotype immunity to hepatitis C virus. J Virol 2004;78:1575-1581. 111. Wyatt C A , Andrus L , Brotman B, Huang F, Lee D H , Prince A M . Immunity in chimpanzees chronically infected with hepatitis C virus: role of minor quasispecies in reinfection. J Virol 1998;72:1725-1730. 112. Alter MJ , Margolis HS, Krawczynski K , Judson F N , Mares A , Alexander WJ, Hu PY, et al. The natural history of community-acquired hepatitis C in the United States. The Sentinel Counties Chronic non-A, non-B Hepatitis Study Team. N Engl J Med 1992;327:1899-1905. 113. Thomas DL , Astemborski J, Vlahov D, Strathdee SA, Ray SC, Nelson K E , Galai N , et al. Determinants of the quantity of hepatitis C virus RNA. J Infect Dis 2000;181:844-851. 114. Inglesby T V , Rai R, Astemborski J, Gruskin L, Nelson K E , Vlahov D, Thomas DL. A prospective, community-based evaluation of liver enzymes in individuals with hepatitis C after drug use. Hepatology 1999;29:590-596. 115. Seeff L B . Natural history of chronic hepatitis C. Hepatology 2002;36:S35-46. 116. Strader DB, Wright T, Thomas DL, Seeff L B . Diagnosis, management, and treatment of hepatitis C. Hepatology 2004;39:1147-1171. 41 117. Seeff L B , Hoofnagle JH. Appendix: The National Institutes of Health Consensus Development Conference Management of Hepatitis C 2002. Clin Liver Dis 2003;7:261-287. 118. Perrillo RP. The role of liver biopsy in hepatitis C. Hepatology 1997;26:57S-61S. 119. Kiyosawa K , Tanaka E, Sodeyama T, Furuta K , Usuda S, Yousuf M , Furuta S. Transition of antibody to hepatitis C virus from chronic hepatitis to hepatocellular carcinoma. Jpn J Cancer Res 1990;81:1089-1091. 120. Goodman ZD, Ishak K G . Histopathology of hepatitis C virus infection. Semin Liver Dis 1995;15:70-81. 121. Mattsson L, Sonnerborg A , Weiland O. Outcome of acute symptomatic non-A, non-B hepatitis: a 13-year follow-up study of hepatitis C virus markers. Liver 1993;13:274-278. 122. Hopf U , Moller B, Kuther D, Stemerowicz R, Lobeck H, Ludtke-Handjery A , Walter E, et al. Long-term follow-up of posttransfusion and sporadic chronic hepatitis non-A, non-B and frequency of circulating antibodies to hepatitis C virus (HCV). J Hepatol 1990;10:69-76. 123. D i Bisceglie A M , Goodman ZD, Ishak K G , Hoofnagle JH, Melpolder JJ, Alter HJ. Long-term clinical and histopathological follow-up of chronic posttransfusion hepatitis. Hepatology 1991; 14:969-974. 124. Tremolada F, Casarin C, Alberti A , Drago C, Tagger A , Ribero M L , Realdi G. Long-term follow-up of non-A, non-B (type C) post-transfusion hepatitis. J Hepatol 1992;16:273-281. 125. Koretz R L , Abbey H , Coleman E, Gitnick G. Non-A, non-B post-transfusion hepatitis. Looking back in the second decade. Ann Intern Med 1993;119:110-115. 126. Rai R, Wilson L E , Astemborski J, Anania F, Torbenson M , Spoler C, Vlahov D, et al. Severity and correlates of liver disease in hepatitis C virus-infected injection drug users. Hepatology 2002;35:1247-1255. 127. Tong M J , el-Farra NS, Reikes AR, Co R L . Clinical outcomes after transfusion-associated hepatitis C. N Engl J Med 1995;332:1463-1466. 128. Yano M , Kumada H , Kage M , Ikeda K , Shimamatsu K, Inoue O, Hashimoto E, et al. The long-term pathological evolution of chronic hepatitis C. Hepatology 1996;23:1334-1340. 129. Niederau C, Lange S, Heintges T, Erhardt A , Buschkamp M , Hurter D, Nawrocki M , et al. Prognosis of chronic hepatitis C: results of a large, prospective cohort study. Hepatology 1998;28:1687-1695. 130. Seeff L B , Buskell-Bales Z, Wright EC, Durako SJ, Alter HJ, Iber FL, Hollinger FB, et al. Long-term mortality after transfusion-associated non-A, non-B hepatitis. The National Heart, Lung, and Blood Institute Study Group. N Engl J Med 1992;327:1906-1911. 131. Casiraghi M A , De Paschale M , Romano L , Biffi R, Assi A , Binelli G, Zanetti AR. Long-term outcome (35 years) of hepatitis C after acquisition of infection through mini transfusions of blood given at birth. Hepatology 2004;39:90-96. 42 132. Fattovich G, Giustina G, Degos F, Tremolada F, Diodati G, Almasio P, Nevens F, et al. Morbidity and mortality in compensated cirrhosis type C: a retrospective follow-up study of 384 patients. Gastroenterology 1997; 112:463-472. 133. Colombo M , de Franchis R, Del Ninno E, Sangiovanni A , De Fazio C, Tornmasini M , Donato M F , et al. Hepatocellular carcinoma in Italian patients with cirrhosis. N Engl J Med 1991 ;325:675-680. 134. Tsukuma H, Hiyama T, Tanaka S, Nakao M , Yabuuchi T, Kitamura T, Nakanishi K , et al. Risk factors for hepatocellular carcinoma among patients with chronic liver disease. N Engl J Med 1993;328:1797-1801. 135. Alberti A , Noventa F, Benvegnu L, Boccato S, Gatta A . Prevalence of liver disease in a population of asymptomatic persons with hepatitis C virus infection. Ann Intern Med 2002;137:961-964. 136. Poynard T, Bedossa P, Opolon P. Natural history of liver fibrosis progression in patients with chronic hepatitis C. The OBSVIRC, M E T A V I R , CLINIVIR, and DOSVIRC groups. Lancet 1997;349:825-832. 137. Benhamou Y , Bochet M , D i Martino V , Charlotte F, Azria F, Coutellier A , Vidaud M , et al. Liver fibrosis progression in human immunodeficiency virus and hepatitis C virus coinfected patients. The Multivirc Group. Hepatology 1999;30:1054-1058. 138. Eyster M E , Fried M W , Di Bisceglie A M , Goedert JJ. Increasing hepatitis C virus R N A levels in hemophiliacs: relationship to human immunodeficiency virus infection and liver disease. Multicenter Hemophilia Cohort Study. Blood 1994;84:1020-1023. 139. Darby SC, Ewart DW, Giangrande PL, Spooner RJ, Rizza CR, Dusheiko G M , Lee CA, et al. Mortality from liver cancer and liver disease in haemophilic men and boys in U K given blood products contaminated with hepatitis C. U K Haemophilia Centre Directors' Organisation. Lancet 1997;350:1425-1431. 140. Lesens O, Deschenes M , Steben M , Belanger G, Tsoukas C M . Hepatitis C virus is related to progressive liver disease in human immunodeficiency virus-positive hemophiliacs and should be treated as an opportunistic infection. J Infect Dis 1999;179:1254-1258. 141. Pol S, Lamorthe B , Thi NT, Thiers V , Carnot F, Zylberberg H, Berthelot P, et al. Retrospective analysis of the impact of HIV infection and alcohol use on chronic hepatitis C in a large cohort of drug users. J Hepatol 1998;28:945-950. 142. Graham CS, Baden LR, Y u E, Mrus J M , Carnie J, Heeren T, Koziel M J . Influence of human immunodeficiency virus infection on the course of hepatitis C virus infection: a meta-analysis. Clin Infect Dis 2001;33:562-569. 143. Ragni M V , Belle SH. Impact of human immunodeficiency virus infection on progression to end-stage liver disease in individuals with hemophilia and hepatitis C virus infection. J Infect Dis 2001;183:1112-1115. 43 144. Soto B, Sanchez-Quijano A , Rodrigo L, del Olmo JA, Garcia-Bengoechea M , Hemandez-Quero J, Rey C, et al. Human immunodeficiency virus infection modifies the natural history of chronic parenterally-acquired hepatitis C with an unusually rapid progression to cirrhosis. J Hepatol 1997;26:1-5. 145. Garcia-Samaniego J, Rodriguez M , Berenguer J, Rodriguez-Rosado R, Carbo J, Asensi V , Soriano V . Hepatocellular carcinoma in HIV-infected patients with chronic hepatitis C. Am J Gastroenterol 2001;96:179-183. 146. K im WR, Gross JB, Jr., Poterucha JJ, Locke GR, 3rd, Dickson ER. Outcome of hospital care of liver disease associated with hepatitis C in the United States. Hepatology 2001;33:201-206. 147. Monga H K , Rodriguez-Barradas M C , Breaux K , Khattak K , Troisi C L , Velez M , Yoffe B. Hepatitis C virus infection-related morbidity and mortality among patients with human immunodeficiency virus infection. Clin Infect Dis 2001;33:240-247. 148. Adinolfi L E , Gambardella M , Andreana A , Tripodi M F , Util i R, Ruggiero G. Steatosis accelerates the progression of liver damage of chronic hepatitis C patients and correlates with specific H C V genotype and visceral obesity. Hepatology 2001;33:1358-1364. 149. Hui J M , Sud A , Farrell GC, Bandara P, Byth K , Kench JG, McCaughan GW, et al. Insulin resistance is associated with chronic hepatitis C virus infection and fibrosis progression [corrected]. Gastroenterology 2003;125:1695-1704. 150. Ostapowicz G, Watson K J , Locarnini SA, Desmond P V . Role of alcohol in the progression of liver disease caused by hepatitis C virus infection. Hepatology 1998;27:1730-1735. 151. Coelho-Little M E , Jeffers LJ, Bernstein DE, Goodman JJ, Reddy KR, de Medina M , L i X , et al. Hepatitis C virus in alcoholic patients with and without clinically apparent liver disease. Alcohol Clin Exp Res 1995;19:1173-1176. 152. Corrao G, Arico S. Independent and combined action of hepatitis C virus infection and alcohol consumption on the risk of symptomatic liver cirrhosis. Hepatology 1998;27:914-919. 153. Fong TL, Kanel GC, Conrad A , Valinluck B, Charboneau F, Adkins R H . Clinical significance of concomitant hepatitis C infection in patients with alcoholic liver disease. Hepatology 1994;19:554-557. 154. Pessione F, Degos F, Marcellin P, Duchatelle V , Njapoum C, Martinot-Peignoux M , Degott C, et al. Effect of alcohol consumption on serum hepatitis C virus R N A and histological lesions in chronic hepatitis C. Hepatology 1998;27:1717-1722. 155. Bortolotti F, Resti M , Giacchino R, Azzari C, Gussetti N , Crivellaro C, Barbera C, et al. Hepatitis C virus infection and related liver disease in children of mothers with antibodies to the virus. J Pediatr 1997;130:990-993. 156. Chang M H , N i Y H , Hwang L H , Lin K H , Lin H H , Chen PJ, Lee C Y , et al. Long term clinical and virologic outcome of primary hepatitis C virus infection in children: a prospective study. Pediatr Infect Dis J 1994;13:769-773. 44 157. Kage M , Fujisawa T, Shiraki K , Tanaka T, Fujisawa T, Kimura A, Shimamatsu K , et al. Pathology of chronic hepatitis C in children. Child Liver Study Group of Japan. Hepatology 1997;26:771-775. 158. Freeman A J , Dore GJ, Law M G , Thorpe M , Von Overbeck J, Lloyd A R , Marinos G, et al. Estimating progression to cirrhosis in chronic hepatitis C virus infection. Hepatology 2001;34:809-816. 159. McHutchison JG, Poynard T, Esteban-Mur R, Davis GL, Goodman ZD, Harvey J, Ling M H , et al. Hepatic H C V R N A before and after treatment with interferon alone or combined with ribavirin. Hepatology 2002;35:688-693. 160. Veldt BJ, Saracco G, Boyer N , Camma C, Bellobuono A , Hopf U , Castillo I, et al. Long term clinical outcome of chronic hepatitis C patients with sustained virological response to interferon monotherapy. Gut 2004;53:1504-1508. 161. Fontaine H, Nalpas B, Poulet B, Carnot F, Zylberberg H, Brechot C, Pol S. Hepatitis activity index is a key factor in determining the natural history of chronic hepatitis C. Hum Pathol 2001;32:904-909. 162. Manns MP, McHutchison JG, Gordon SC, Rustgi V K , Shiffman M , Reindollar R, Goodman ZD, et al. Peginterferon alfa-2b plus ribavirin compared with interferon alfa-2b plus ribavirin for initial treatment of chronic hepatitis C: a randomised trial. Lancet 2001;358:958-965. 163. Bernstein D, Kleinman L, Barker C M , Revicki D A , Green J. Relationship of health-related quality of life to treatment adherence and sustained response in chronic hepatitis C patients. Hepatology 2002;35:704-708. 164. Hung C H , Lee C M , Lu SN, Wang JH, Hu TH, Tung HD, Chen C H , et al. Long-term effect of interferon alpha-2b plus ribavirin therapy on incidence of hepatocellular carcinoma in patients with hepatitis C virus-related cirrhosis. J Viral Hepat 2006;13:409-414. 165. Yoshida H, Arakawa Y , Sata M , Nishiguchi S, Yano M , Fujiyama S, Yamada G, et al. Interferon therapy prolonged life expectancy among chronic hepatitis C patients. Gastroenterology 2002; 123:483-491. 166. Hoofnagle JH, Mullen K D , Jones DB, Rustgi V , D i Bisceglie A , Peters M , Waggoner JG, et al. Treatment of chronic non-A,non-B hepatitis with recombinant human alpha interferon. A preliminary report. N Engl J Med 1986;315:1575-1578. 167. Lau DT, Kleiner DE, Ghany M G , Park Y , Schmid P, Hoofnagle JH. 10-Year follow-up after interferon-alpha therapy for chronic hepatitis C. Hepatology 1998;28:1121-1127. 168. McHutchison JG, Gordon SC, Schiff ER, Shiffman M L , Lee W M , Rustgi V K , Goodman ZD, et al. Interferon alfa-2b alone or in combination with ribavirin as initial treatment for chronic hepatitis C. Hepatitis Interventional Therapy Group. N Engl J Med 1998;339:1485-1492. 169. Poynard T, Marcellin P, Lee SS, Niederau C, Minuk GS, Ideo G, Bain V , et al. Randomised trial of interferon alpha2b plus ribavirin for 48 weeks or for 24 weeks versus interferon alpha2b plus placebo for 48 weeks for treatment of chronic infection with hepatitis C virus. International Hepatitis Interventional Therapy Group (IHIT). Lancet 1998;352:1426-1432. 45 170. Lindsay K L . Therapy of hepatitis C: overview. Hepatology 1997;26:71S-77S. 171. Poynard T, Leroy V , Cohard M , Thevenot T, Mathurin P, Opolon P, Zarski JP. Meta-analysis of interferon randomized trials in the treatment of viral hepatitis C: effects of dose and duration. Hepatology 1996;24:778-789. 172. National Institutes of Health Consensus Development Conference Panel statement: management of hepatitis C. Hepatology 1997;26:2S-10S. 173. Reichard O, Andersson J, Schvarcz R, Weiland O. Ribavirin treatment for chronic hepatitis C. Lancet 1991;337:1058-1061. 174. Dusheiko G, Main J, Thomas H , Reichard O, Lee C, Dhillon A , Rassam S, et al. Ribavirin treatment for patients with chronic hepatitis C: results of a placebo-controlled study. J Hepatol 1996;25:591-598. 175. Reichard O, Yun ZB, Sonnerborg A , Weiland O. Hepatitis C viral R N A titers in serum prior to, during, and after oral treatment with ribavirin for chronic hepatitis C. J Med Virol 1993;41:99-102. 176. D i Bisceglie A M , Shindo M , Fong TL , Fried M W , Swain M G , Bergasa N V , Axiotis C A , et al. A pilot study of ribavirin therapy for chronic hepatitis C. Hepatology 1992;16:649-654. 177. Brillanti S, Garson J, Foli M , Whitby K , Deaville R, Masci C, Miglioli M , et al. A pilot study of combination therapy with ribavirin plus interferon alfa for interferon alfa-resistant chronic hepatitis C. Gastroenterology 1994; 107:812-817. 178. Wills RJ, Dennis S, Spiegel HE, Gibson D M , Nadler PI. Interferon kinetics and adverse reactions after intravenous, intramuscular, and subcutaneous injection. Clin Pharmacol Ther 1984;35:722-727. 179. Wills RJ. Clinical pharmacokinetics of interferons. Clin Pharmacokinet 1990; 19:390-399. 180. Karnam US, Reddy KR. Pegylated interferons. Clin Liver Dis 2003;7:139-148. 181. Bailon P, Palleroni A , Schaffer C A , Spence C L , Fung WJ, Porter JE, Ehrlich GK, et al. Rational design of a potent, long-lasting form of interferon: a 40 kDa branched polyethylene glycol-conjugated interferon alpha-2a for the treatment of hepatitis C. Bioconjug Chem 2001;12:195-202. 182. Algranati NE , Sy S, Modi M . A branched methoxy 40 kDa polyethylene glycol (PEG) moiety optimizes the pharmacokinetics (PK) of peginterferon a -2a (PEG-JFN) and may explain its enhanced efficacy in chronic hepatitis C (CHC) [abstract 120]. Hepatology 1999;30:190A. 183. Modi M W , Fried M , Reindollar RW, Rustgi VR, Kenny R, Wright TL . The pharmacokinetic behavior of pegylated (40KDA) interferon alfa-2a (Pegasys) in chronic hepatitis C patients after multiple dosing. Hepatology 2000;32:394A. 184. Harris JM, Martin NE, Modi M . Pegylation: a novel process for modifying pharmacokinetics. Clin Pharmacokinet 2001;40:539-551. 185. Modi M W , Fulton JS, Buckman D K , Wright TL, Moore DJ. Clearance of pegylated (40 kDa) interferon alfa-2a Pegasys is primarily hepatic. Hepatology 2000;32:371 A . 4 6 186. Grace M , Youngster S, Gitlin G, Sydor W, Xie L , Westreich L, Jacobs S, et al. Structural and biologic characterization of pegylated recombinant IFN-alpha2b. J Interferon Cytokine Res 2001;21:1103-1115. 187. Glue P, Fang JW, Rouzier-Panis R, Raffanel C, Sabo R, Gupta SK, Salfi M , et al. Pegylated interferon-alpha2b: pharmacokinetics, pharmacodynamics, safety, and preliminary efficacy data. Hepatitis C Intervention Therapy Group. Clin Pharmacol Ther 2000;68:556-567. 188. Glue P, Rouzier-Panis R, Raffanel C, Sabo R, Gupta SK, Salfi M , Jacobs S, et al. A dose-ranging study of pegylated interferon alfa-2b and ribavirin in chronic hepatitis C. The Hepatitis C Intervention Therapy Group. Hepatology 2000;32:647-653. 189. Lindsay K L , Trepo C, Heintges T, Shiffman M L , Gordon SC, Hoefs JC, Schiff ER, et al. A randomized, double-blind trial comparing pegylated interferon alfa-2b to interferon alfa-2b as initial treatment for chronic hepatitis C. Hepatology 2001;34:395-403. 190. Silva M , Poo J, Wagner F, Jackson M , Cutler D, Grace M , Bordens R, et al. A randomised trial to compare the pharmacokinetic, pharmacodynamic, and antiviral effects of peginterferon alfa-2b and peginterferon alfa-2a in patients with chronic hepatitis C (COMPARE). J Hepatol 2006;45:204-213. 191. Lohmann V , Korner F, Koch J, Herian U , Theilmann L , Bartenschlager R. Replication of subgenomic hepatitis C virus RNAs in a hepatoma cell line. Science 1999;285:110-113. 192. Frese M , Pietschmann T, Moradpour D, Haller O, Bartenschlager R. Interferon-alpha inhibits hepatitis C virus subgenomic R N A replication by an MxA-independent pathway. J Gen Virol 2001;82:723-733. 193. Guo JT, Bichko V V , Seeger C. Effect of alpha interferon on the hepatitis C virus replicon. J Virol 2001;75:8516-8523. 194. Lanford RE, Guerra B, Lee H , Averett DR, Pfeiffer B, Chavez D, Notvall L, et al. Antiviral effect and virus-host interactions in response to alpha interferon, gamma interferon, poly(i)-poly(c), tumor necrosis factor alpha, and ribavirin in hepatitis C virus subgenomic replicons. J Virol 2003;77:1092-1104. 195. Castet V , Fournier C, Soulier A , Brillet R, Coste J, Larrey D, Dhumeaux D, et al. Alpha interferon inhibits hepatitis C virus replication in primary human hepatocytes infected in vitro. J Virol 2002;76:8189-8199. 196. Feld JJ, Hoofnagle JH. Mechanism of action of interferon and ribavirin in treatment of hepatitis C. Nature 2005;436:967-972. 197. Sen GC. Viruses and interferons. Annu Rev Microbiol 2001;55:255-281. 198. Tilg H . New insights into the mechanisms of interferon alfa: an immunoregulatory and anti-inflammatory cytokine. Gastroenterology 1997;112:1017-1021. 199. Pawlotsky J M , Dahari H , Neumann A U , Hezode C, Germanidis G, Lonjon I, Castera L , et al. Antiviral action of ribavirin in chronic hepatitis C. Gastroenterology 2004;126:703-714. 47 200. Bronowicki JP, Ouzan D, Asselah T, Desmorat H , Zarski JP, Foucher J, Bourliere M , et al. Effect of ribavirin in genotype 1 patients with hepatitis C responding to pegylated interferon alfa-2a plus ribavirin. Gastroenterology 2006;131:1040-1048. 201. Lau JY, Tarn RC, Liang TJ, Hong Z. Mechanism of action of ribavirin in the combination treatment of chronic H C V infection. Hepatology 2002;35:1002-1009. 202. Maag D, Castro C, Hong Z, Cameron CE. Hepatitis C virus RNA-dependent R N A polymerase (NS5B) as a mediator of the antiviral activity of ribavirin. J Biol Chem 2001;276:46094-46098. 203. Hultgren C, Milich DR, Weiland O, Sallberg M . The antiviral compound ribavirin modulates the T helper (Th) 1/Th2 subset balance in hepatitis B and C virus-specific immune responses. J Gen Virol 1998;79(Pt 10):2381-2391. 204. Neumann-Haefelin C, Blum HE, Chisari F V , Thimme R. T cell response in hepatitis C virus infection. J Clin Virol 2005;32:75-85. 205. Dixit N M , Layden-Almer JE, Layden TJ, Perelson AS. Modelling how ribavirin improves interferon response rates in hepatitis C virus infection. Nature 2004;432:922-924. 206. Crotty S, Maag D, Arnold JJ, Zhong W, Lau JY, Hong Z, Andino R, et al. The broad-spectrum antiviral ribonucleoside ribavirin is an R N A virus mutagen. Nat Med 2000;6:1375-1379. 207. Chevaliez S, Brillet R, Hezode C, Dhumeaux D, Pawlotsky J M . Assessment of ribavirin mutagenic properties in vivo and the influence of interferon alpha-induced reduction of hepatitis C virus R N A load upon therapy. Hepatology 2005;42:679A. 208. Lutchman G A , Danehower S, Park Y , Ward C, Liang TJ, Hoofnagle JH, Thomson M Z , et al. Mutation rate of hepatitis C virus in patients during ribavirin monotherapy. Hepatology 2004;40:385A. 209. Fried M W , Shiffman M L , Reddy KR, Smith C, Marinos G, Goncales FL , Jr., Haussinger D, et al. Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection. N Engl J Med 2002;347:975-982. 210. Manns M P , Wedemeyer H, Cornberg M . Treating viral hepatitis C: efficacy, side effects, and complications. Gut 2006;55:1350-1359. 211. Hadziyannis SJ, Sette H , Jr., Morgan TR, Balan V , Diago M , Marcellin P, Ramadori G, et al. Peginterferon-alpha2a and ribavirin combination therapy in chronic hepatitis C: a randomized study of treatment duration and ribavirin dose. Ann Intern Med 2004;140:346-355. 212. Ferenci P, Fried M W , Shiffman M L , Smith CI, Marinos G, Goncales FL, Jr., Haussinger D, et al. Predicting sustained virological responses in chronic hepatitis C patients treated with peginterferon alfa-2a (40 KD)/ribavirin. J Hepatol 2005;43:425-433. 213. Davis G L , Wong JB, McHutchison JG, Manns MP, Harvey J, Albrecht J. Early virologic response to treatment with peginterferon alfa-2b plus ribavirin in patients with chronic hepatitis C. Hepatology 2003;38:645-652. 48 214. Jensen D M , Morgan TR, Marcellin P, Pockros PJ, Reddy KR, Hadziyannis SJ, Ferenci P, et al. Early identification of H C V genotype 1 patients responding to 24 weeks peginterferon alpha-2a (40 kd)/ribavirin therapy. Hepatology 2006;43:954-960. 215. Dalgard O, Mangia A . Short-term therapy for patients with hepatitis C virus genotype 2 or 3 infection. Drugs 2006;66:1807-1815. 216. Ho SB, Nguyen H , Tetrick L L , Opitz G A , Basara M L , Dieperink E. Influence of psychiatric diagnoses on interferon-alpha treatment for chronic hepatitis C in a veteran population. Am J Gastroenterol 2001;96:157-164. 217. Mulder RT, Ang M , Chapman B, Ross A , Stevens IF, Edgar C. Interferon treatment is not associated with a worsening of psychiatric symptoms in patients with hepatitis C. J Gastroenterol Hepatol 2000;15:300-303. 218. Trask PC, Esper P, Riba M , Redman B. Psychiatric side effects of interferon therapy: prevalence, proposed mechanisms, and future directions. J Clin Oncol 2000;18:2316-2326. 219. Kraus M R , Schafer A , Csef H , Faller H , Mork H, Scheurlen M . Compliance with therapy in patients with chronic hepatitis C: associations with psychiatric symptoms, interpersonal problems, and mode of acquisition. Dig Dis Sci 2001;46:2060-2065. 220. Sherman M , Bain V , Villeneuve JP, Myers RP, Cooper C, Martin S, Lowe C. The management of chronic viral hepatitis: a Canadian consensus conference 2004. Can J Gastroenterol 2004;18:715-728. 221. Edlin BR. Prevention and treatment of hepatitis C in injection drug users. Hepatology 2002;36:S210-219. 222. Edlin BR, Seal K H , Lorvick J, Krai A H , Ciccarone D H , Moore L D , Lo B. Is it justifiable to withhold treatment for hepatitis C from illicit-drug users? N Engl J Med 2001;345:211-215. 223. Gourevitch M N , Wasserman W, Panero M S , Selwyn PA. Successful adherence to observed prophylaxis and treatment of tuberculosis among drug users in a methadone program. J Addict Dis 1996;15:93-104. 224. Marco A , Cayla JA, Serra M , Pedro R, Sanrama C, Guerrero R, Ribot N . Predictors of adherence to tuberculosis treatment in a supervised therapy programme for prisoners before and after release. Study Group of Adherence to Tuberculosis Treatment of Prisoners. Eur Respir J 1998; 12:967-971. 225. Paterson D, Swindells S, Mohr J, Brester M , Vergis E, Squier C, Wagener M , et al.: How much adherence is enough? A prospective study of adherence to protease inhibitor therapy using M E M S caps [abstract 92]. In: 6th Conference on Retroviruses and Opportunistic Infections, Chicago, January 31-February4, 1999. 226. Eldred L J , Wu A W , Chaisson RE, Moore RD. Adherence to antiretroviral and Pneumocystis prophylaxis in HIV disease. J Acquir Immune Defic Syndr Hum Retroviral 1998; 18:117-125. 49 227. Singh N , Berman SM, Swindells S, Justis JC, Mohr JA, Squier C, Wagener M M . Adherence of human immunodeficiency virus-infected patients to antiretroviral therapy. Clin Infect Dis 1999;29:824-830. 228. Tulsky JP, Pilote L , Hahn JA, Zolopa A J , Burke M , Chesney M , Moss AR. Adherence to isoniazid prophylaxis in the homeless: a randomized controlled trial. Arch Intern Med 2000;160:697-702. 229. Bangsberg DR, Hecht F M , Charlebois ED, Zolopa AR, Holodniy M , Sheiner L , Bamberger JD, et al. Adherence to protease inhibitors, H I V - l viral load, and development of drug resistance in an indigent population. AIDS 2000;14:357-366. 230. Arnsten J, Demas P, Gourevitch M , Buono D, Farzadegan H , Schoenbaum E: Adherence and viral load in HIV-infected drug users: comparison of self-report and medication event monitors. In. In: Program and Abstracts of the 7th Conference on Retroviruses and Opportunistic Infections, San Francisco, 20 January-2 February 2000. Alexandria, V A : Foundation for Retrovirology and Human Health, 2000; 88. 231. Gebo K A , Moore RD: Do social stressors, health beliefs, and illicit drug use correlate with adherence to antiretroviral therapy [abstract 360]. In: Program and Abstracts of the 38th Annual Meeting of the Infectious Diseases Society of America, 7-10 September 2000, New Orleans, L A . In. Alexandria, V A : Infectious Diseases Society of America, 2000; 102. 232. Mezzelani P, Venturini L, Turrina G, Lugoboni F, Des Jarlais DC. High compliance with a hepatitis B virus vaccination program among intravenous drug users. J Infect Dis 1991; 163:923. 233. Steinhoff M C , Auerbach BS, Nelson K E , Vlahov D, Becker RL, Graham N M , Schwartz DH, et al. Antibody responses to Haemophilus influenzae type B vaccines in men with human immunodeficiency virus infection. New Engl J Med 1991;325:1837-1842. 234. Harrison K , Vlahov D, Jones K , Charron K , Clements M L . Medical eligibility, comprehension of the consent process, and retention of injection drug users recruited for an HIV vaccine trial. J Acquir Immune Defic Syndr 1995;10:386-390. 235. Bangsberg DR, Hecht F M , Clague H , Charlebois ED, Ciccarone D, Chesney M , Moss A . Provider assessment of adherence to HIV antiretroviral therapy. J Acquir Immune Defic Syndr 2001;26:435-442. 236. Milby JB, Sims M K , Khuder S, Schumacher JE, Huggins N , McLellan AT, Woody G, et al. Psychiatric comorbidity: prevalence in methadone maintenance treatment. Am J Drug Alcohol Abuse 1996;22:95-107. 237. Mason BJ, Kocsis JH, Melia D, Khuri ET, Sweeney J, Wells A , Borg L , et al. Psychiatric comorbidity in methadone maintained patients. J Addict Dis 1998;17:75-89. 238. Musselman DL , Kell MJ . Prevalence and improvement in psychopathology in opioid dependent patients participating in methadone maintenance. J Addict Dis 1995;14:67-82. 239. Pariante C M , Orru M G , Baita A , Farci M G , Carpiniello B . Treatment with interferon-alpha in patients with chronic hepatitis and mood or anxiety disorders. Lancet 1999;354:131-132. 50 240. Schaefer M , Schwaiger M , Garkisch AS, Pich M , Hinzpeter A , Uebelhack R, Heinz A , et al. Prevention of interferon-alpha associated depression in psychiatric risk patients with chronic hepatitis C. J Hepatol 2005;42:793-798. 241. Lin M K , Celentano DD, Strathdee SA, Vlahov D. Self-reported adherence to antiretroviral therapies among HIV sero-positive injection drug users in Baltimore, Maryland [abstract 562]. In: 62nd Annual Scientific Meeting of the College on Problems of Drug Dependence; 2000 17-22 June; San Juan, Puerto Rico; 2000. p. 58. 242. Lorvick J, Thompson S, Edlin BR, Krai A H , Lifson AR, Watters JK. Incentives and accessibility: a pilot study to promote adherence to TB prophylaxis in a high-risk community. Journal of Urban Health 1999;76:461-467. 243. Lorvick J, Edlin BR, Lifson A . Randomized controlled trial of adherence to preventive TB therapy among injection drug users. In: 126th Annual Meeting of the American Public Health Association; 1998 November 15-19, 1998; Washington, D.C.; 1998. 244. Balkrishnan R. Predictors of medication adherence in the elderly. Clin Ther 1998;20:764-771. 245. Carney R M , Freedland K E , Eisen SA, Rich M W , Jaffe AS . Major depression and medication adherence in elderly patients with coronary artery disease. Health Psychology 1995;14:88-90. 246. Curtis R, Friedman SR, Neaigus A , Jose B, Goldstein M , Des Jarlais DC. Implications of directly observed therapy in tuberculosis control measures among IDUs. Public Health Rep 1994;109:319-327. 247. Seal K H , Krai A H , McNees A , Gee L, Lorvick J, Edlin BR: High adherence by drug users to vaccine research: a randomized trial of cash incentives vs. outreach among street-recruited injection drug users (abstract #21) (oral presentation). In: AIDS Vaccine 2001 Program and Abstracts, Philadelphia, Pennsylvania, 5-8 September 2001. Alexandria, Va.: Foundation for ADDS Vacine Research and Development, 2001; 29. 248. Seal K H , Lorvick J, Moore J, Thawley R, Hammond JP, Gann D, Edlin BR: Incentives for research involving liver biopsy in HCV-infected injection drug users: ethical and practical considerations (session #6014). 128th Annual Meeting of the American Public Health Association, Boston, Massachusetts, 12-16 November 2000 (oral presentation). In, 2000. 249. Chesney M A . Factors affecting adherence to antiretroviral therapy. Clin Infect Dis 2000;30(suppl 2):S171-176. 250. Volmink J, Garner P. Interventions for promoting adherence to tuberculosis management. Cochrane Database Syst Rev 2000:CD000010. 251. Bangsberg DR, Hecht F M , Clague H , Charlebois E, Ciccarone D, Chesney M , Moss A. Provider assessment of adherence to HIV antiretroviral therapy. In press. 252. Sorensen JL, Mascovich A, Wall TL , DePhilippis D, Batki SL, Chesney M . Medication adherence strategies for drug abusers with HIV/AIDS. AIDS Care 1998; 10:297-312. 51 253. Dunbar-Jacob J, Burke L E , Puczynski S. Clinical assessment and management of adherence to medical regimens. Washington, DC: American Psychological Association, 1995. 254. Conway B, Prasad J, Reynolds R, Farley J, Jones M , Jutha S, Smith N , et al. Directly observed therapy for the management of HIV-infected patients in a methadone program. Clin Infect Dis 2004;38 Suppl 5:S402-408. 255. Davis GL, Rodrigue JR. Treatment of chronic hepatitis C in active drug users. N Engl J Med 2001;345:215-217. 256. Backmund M , Meyer K, Von Zielonka M , Eichenlaub D. Treatment of hepatitis C infection in injection drug users. Hepatology 2001;34:188-193. 257. Fattovich G, Giustina G, Favarato S, Ruol A . A survey of adverse events in 11,241 patients with chronic viral hepatitis treated with alfa interferon. J Hepatol 1996;24:38-47. 258. Sylvestre DL, Litwin A H , Clements BJ, Gourevitch M N . The impact of barriers to hepatitis C virus treatment in recovering heroin users maintained on methadone. J Subst Abuse Treat 2005;29:159-165. 259. Van Thiel DH, Anantharaju A , Creech S. Response to treatment of hepatitis C in individuals with a recent history of intravenous drug abuse. Am J Gastroenterol 2003;98:2281-2288. 260. Mauss S, Berger F, Goelz J, Jacob B, Schmutz G. A prospective controlled study of interferon-based therapy of chronic hepatitis C in patients on methadone maintenance. Hepatology 2004;40:120-124. 261. Backmund M , Meyer K, Edlin BR. Infrequent reinfection after successful treatment for hepatitis C virus infection in injection drug users. Clin Infect Dis 2004;39:1540-1543. 262. Grebely J, Conway, B, Raffa, J, Lai, C, Krajden, M and Tyndall, M W . Uptake of hepatitis c virus (HCV) treatment among injection drug users (IDUs) in Vancouver, Canada. In: Program and Abstracts from the 41st Annual Meeting of the European Association for the Study of the Liver 2006. 263. Strathdee SA, Latka M , Campbell J, O'Driscoll PT, Golub ET, Kapadia F, Pollini R A , et al. Factors associated with interest in initiating treatment for hepatitis C Virus (HCV) infection among young H C V -infected injection drug users. Clin Infect Dis 2005;40 Suppl 5:S304-312. 264. Doab A , Treloar C, Dore GJ. Knowledge and attitudes about treatment for hepatitis C virus infection and barriers to treatment among current injection drug users in Australia. Clin Infect Dis 2005;40 Suppl 5:S313-320. 265. Genoway K GJ, Duncan F, Viljoen M , Khara M , Raffa J, Tyndall M , DeVlaming S and Conway B. Initiation of Hepatitis C Virus (HCV) Treatment among Injection Drug Users (IDUs). In: Program and Abstracts from the 17th Annual International Conference on the Reduction of Drug Related Harm 2006. 266. Duncan F, Grebely, J, Genoway, K , Viljoen, M , Khara, M , Raffa, J, Tyndall, M , DeVlaming, S and Conway, B . Barriers Associated With The Initiation Of H C V Treatment In Injection Drug Users (IDUs): A n Opportunity For Optimizing Outcome In Marginalized Populations. Global Antiviral Journal 2005;l:101_Abstract 102. 52 267. Fleming C A , Craven DE, Thornton D, Tumilty S, Nunes D. Hepatitis C virus and human immunodeficiency virus coinfection in an urban population: low eligibility for interferon treatment. Clin Infect Dis 2003;36:97-100. 268. Fishbein D A , Lo Y , Reinus JF, Gourevitch M N , Klein RS. Factors associated with successful referral for clinical care of drug users with chronic hepatitis C who have or are at risk for HIV infection. J Acquir Immune Defic Syndr 2004;37:1367-1375. 269. Restrepo A , Johnson TC, Widjaja D, Yarmus L, Meyer K , Clain DJ, Bodenheimer HC, Jr., et al. The rate of treatment of chronic hepatitis C in patients co-infected with HIV in an urban medical centre. J Viral Hepat 2005;12:86-90. 270. Falck-Ytter Y , Kale H , Mullen K D , Sarbah SA, Sorescu L , McCullough A J . Surprisingly small effect of antiviral treatment in patients with hepatitis C. Ann Intern Med 2002;136:288-292. 271. Thompson V V , Ragland K E , Hall CS, Morgan M , Bangsberg DR. Provider assessment of eligibility for hepatitis C treatment in HIV-infected homeless and marginally housed persons. AIDS 2005;19Suppl3:S208-S214. 272. Van Thiel D H , Friedlander L, Molloy PJ, Fagiuoli S, Kania RJ, Caraceni P. Interferon-alpha can be used successfully in patients with hepatitis C virus-positive chronic hepatitis who have a psychiatric illness. Eur J Gastroenterol Hepatol 1995;7:165-168. 273. Neri S, Bruno C M , Abate G, Ierna D, Mauceri B, Cilio D, Bordonaro F, et al. Controlled clinical trial to assess the response of recent heroin abusers with chronic hepatitis C virus infection to treatment with interferon alpha-n2b. Clin Ther 2002;24:1627-1635. 274. Dalgard O, Bjoro K , Helium K, Myrvang B, Skaug K , Gutigard B, Bell H . Treatment of chronic hepatitis C in injecting drug users: 5 years' follow-up. Eur Addict Res 2002;8:45-49. 275. Dalgard O. Follow-up studies of treatment for hepatitis C virus infection among injection drug users. Clin Infect Dis 2005;40 Suppl 5:S336-338. 276. Schaefer M , Heinz A , Backmund M . Treatment of chronic hepatitis C in patients with drug dependence: time to change the rules? Addiction 2004;99:1167-1175. 277. Sylvestre DL. Treating hepatitis C in methadone maintenance patients: an interim analysis. Drug Alcohol Depend 2002;67:117-123. 278. Matthews G, Kronborg IJ, Dore GJ. Treatment for hepatitis C virus infection among current injection drug users in Australia. Clin Infect Dis 2005;40 Suppl 5:S325-329. 279. Schaefer M , Schmidt F, Folwaczny C, Lorenz R, Martin G, Schindlbeck N , Heldwein W, et al. Adherence and mental side effects during hepatitis C treatment with interferon alfa and ribavirin in psychiatric risk groups. Hepatology 2003;37:443-451. 280. Jeffrey GP, MacQuillan G, Chua F, Galhenage S, Bull J, Young E, Hulse G, et al. Hepatitis C virus eradication in intravenous drug users maintained with subcutaneous naltrexone implants. Hepatology 2007;45:111-117. 53 CHAPTER II Factors Associated With Spontaneous Clearance of HCV Among Illicit Drug Users1 2.1 INTRODUCTION Illicit drug use is associated with high rates of hepatitis C virus ( H C V ) transmission in many urban centres. O f the estimated 170 mil l ion H C V prevalent cases in the world, greater than 50% occur among injection drug users (IDUs) and over 75%> of incident infections occur in this population (1). Acute infection with H C V is characterized by the detection of viremia, subsequent development of HCV-specif ic antibodies, a high likelihood of persistent viremia and chronic infection (2, 3). Following acute infection, the overall rate of spontaneous viral clearance is estimated to be 25%>, but appears to be dependent on the route o f transmission and other host and pathogen-related characteristics (4-9). Factors that have been associated with spontaneous clearance include female sex (10-14) and younger age at the time of infection (15, 16). Conversely, black race and co-infection with human immunodeficiency virus (17) (5, 7, 18) have been associated with reduced rates of H C V clearance. In 1997, studies from the Downtown East Side of Vancouver, home to greater than 5,000 IDUs, reported annual H C V incidence rates remaining above 16 cases per hundred person years between 1996 and 1999 (19-21). The corresponding prevalence of H I V and H C V was 23%> and 88%, respectively (20). This neighborhood received international attention in the late 1990s due to increasing visible drug use, a significant rise in overdose deaths and the declaration of a public health emergency due to epidemic rates o f H I V and H C V infection. These outbreaks of H I V and H C V infection occurred despite the presence of needle-exchange programs and free access to medical treatment. 1 A version of this chapter has been accepted for publication. Grebely, J., Raffa, J.D., Lai, C , Krajden, M . , Conway, B . and Tyndall, M.W. (2007) Factors Associated With Spontaneous Clearance of H C V Among Illicit Drug Users. Can J of Gastroenterology. "Reproduced with permission, Pulsus Group, Can J Gastroenterology 2007:In Press." 54 To increase our understanding of the HCV epidemic in this population, identifying the determinants of early clearance of viremia (generally understood to represent a "spontaneous cure" of HCV) is essential. With this in mind, we measured the rate and characteristics of HCV clearance among infected individuals enrolled in a large, community-based cohort in Vancouver. 2.2 PATIENTS AND METHODS 2.2.1 Study Population The Community Health and Safety Evaluation (CHASE) project is a prospective open cohort study designed to evaluate health service use in the Downtown Eastside of Vancouver. Between January 2003 and June 2004, 3,553 subjects were recruited via community organizations and door-to-door canvassing of a random sample of single occupancy hotels in the community, based on census information. Subjects were eligible for inclusion if they lived, or utilized health services, in the community. Study participants received a CDN$ 10 stipend to complete a short, interviewer-administered questionnaire to collect information about demographics, health service utilization, HIV testing, HCV testing and recent illicit drug use. Subjects were requested to provide a time limited consent for the researchers to perform linkages with provincial health services databases. This included HCV, HIV and hepatitis B virus (HBV) testing performed at the British Columbia Centre for Disease Control and the University of British Columbia Virology Department. Subjects who received treatment for HCV infection were excluded from this study to eliminate the possibility of treatment induced viral clearance as a confounding factor. Of the CHASE cohort participants, 762 were included in the study based on demonstrating anti-HCV reactivity and having one or more commercial HCV RNA tests performed (Figure 1). The University of British Columbia/Providence Health Care Research Ethics Board approved this study. 2.2.2 Laboratory Testing Samples from individuals with a confirmed positive test for anti-HCV antibodies were further evaluated for the presence of HCV RNA. HCV persistence was defined by the presence of one or more detectable HCV RNA tests following a positive test for anti-HCV. HCV clearance was defined by the presence of one or more undetectable HCV RNA tests following a positive test for anti-HCV. Individuals were suspected of having acute HCV infection based on a single HCV 55 R N A positive or negative result within 6 months o f their first ant i -HCV positive test and were not considered in this analysis because of the potential misclassification of spontaneous viral clearance. A l l H C V antibody and R N A testing was performed at two certified provincial laboratories between 1992 and 2005. H C V antibody testing was performed using, second- or third-generation EIAs (May 1992 to September 1993: U B I H C V E I A v2.0 (Organon Teknika, Durham, North Carolina); October 1993 to July 1994: U B I H C V E I A v 2.1 (Organon Teknika, Durham, North Carolina); August 1994 to March 1997: U B I H C V E I A v 4.0 (Organon Teknika, Durham, North Carolina); Apr i l 1997 to present: A x S Y M H C V v 3.0 (Abbott Diagnostics, Chicago, Illinois). Specimens reactive for an t i -HCV antibodies were retested by the second or third generation Recombinant Immunoblot Assay (Chiron, Emeryville, California) until 1999 for confirmation. Between Apr i l 1997 and July 1999, A x S Y M H C V 3.0 ant i -HCV reactive specimens were retested by U B I H C V v4.0 and from August 1999 to present, A x S Y M H C V 3.0 reactive samples were retested by Ortho E e l (Ortho Diagnostics, Mississauga, Canada). Only specimens reactive by both manufacturer's tests were considered to be ant i -HCV reactive. H C V R N A testing was performed by the qualitative C O B A S A M P L I C O R H C V Test v2.0 (Roche Diagnostic Systems, Mississauga, Canada) with a limit of detection of 50 IU/mL. H B V and H I V serology test results were abstracted as recorded in the B C C D C virology database by confidential record linkage. 2.2.3 Statistical Analysis Variables of interest in this analysis included sex, estimated age at infection, ethnicity, housing status, recent treatment with methadone, recent ja i l time, H C V treatment history, alcohol use, injection drug use, non-injection r i l l icit drug use, previous H B V infection and H I V status. The duration of H C V infection in H C V seroprevalent individuals was calculated using the date of their first recorded positive E I A test for H C V antibodies. In 658 patients that were seroprevalent upon their first test, age at infection was estimated by random sampling from the age distribution o f the incident cases. The duration o f infection in 104 individuals with H C V seroconversion between 1992 and 2005 was estimated by using the midpoint between the first positive and last negative H C V antibody tests. Aboriginal ethnicity includes all peoples with an indigenous heritage, including Inuit, First Nations, Native Americans, Alaskan Natives and Metis. Exposure to H B V was defined by current or historical anti-hepatitis B core antibody. Act ive H B V infection was defined by the detection of H B V surface antigen. H I V status was determined by 56 either serological testing from the British Columbia Centre for Disease Control H I V testing database or by subject self reporting for individuals diagnosed outside the province. Unstable housing was defined as l iving in a shelter or l iving on the street/homeless. Injection and non-injection i l l ici t drug use and alcohol use in the past six months was evaluated as "frequent use" (everyday/most days), or "any use" (sub-classified as 2-3 times/week, 2-3 times/month or once/month). Specific drug use evaluations included injection and non-injection cocaine, heroin and crystal methamphetamine use. We then compared characteristics o f subjects with and without H C V clearance using two-sample t-test for quantitative variable, a x2 test or Fisher's Exact Test, as appropriate, for testing differences between proportions. A multiple logistic regression model was then fit comprised of all variables and subsequently reduced using backwards elimination. Statistically significant differences were assessed at a significance level of 0.05 and all reported p-values are two-sided. 2.3 RESULTS O f the 1,315 H C V antibody positive subjects enrolled in the C H A S E cohort, a total of 762 individuals received testing for H C V R N A and were subsequently followed for a median period o f 4.4 years. The mean number o f H C V R N A tests per individual was 1.6 (range, 1-10). No significant differences were observed in the demographics among H C V antibody positive individuals that did and did not receive H C V R N A testing, including age (P=0.86), male sex CP-0.95), ethnicity (P=0.15), unstable housing (P=0.19), i l l icit drug use (P=0.42) and H I V infection (P=0.15). However, subjects that did not receive H C V R N A testing were more likely to engage in recent injection drug use (64.3% vs. 56.6%, P=0.006). Overall, 583 (76.5%) subjects had persistent viremia, with 179 (23.5%) determined to have spontaneous clearance of viremia (Figure 1). The demographic and behavioral characteristics of individuals with persistent viremia versus those with spontaneous clearance are shown in Tables 1 and 2. Overall, the mean age was 42.0 and the estimated age at H C V infection was 32.2 years. There were no significant differences in the mean age (41.7 years vs. 42.5 years, P=0.32) or the estimated age at infection (32.4 years vs. 31.5 years, P=0.27) between individuals with persistent viremia versus those with spontaneous clearance. In the univariate analysis, the ability to develop protective immunity to H C V , evident here by spontaneous clearance of H C V infection, occurred more frequently among individuals of Aboriginal ethnicity [odds ratio (OR), 2.8; 95% confidence interval (CI), 2.0-4.0, PO.001] and 57 female gender (OR, 1.8; 95% CI, 1.3-2.6, P=0.001). Decreased rates of spontaneous H C V clearance were observed in individuals with H I V co-infection (OR, 0.68; 95% CI, 0.46-1.0, P=0.06). Estimated age at infection, housing status, previous methadone treatment, recent jai l time, H B V infection, alcohol use, and il l ici t non-injection or injection drug use in the preceding six months were not associated with H C V persistence or clearance (Tables 1 and 2). A s shown in Table 3, after adjusting for confounding variables using multiple logistic regression analysis, the factors independently associated with spontaneous clearance of H C V included Aboriginal ethnicity [adjusted odds ratio (AOR) , 2.9; 95%> CI, 2.0-4.3, P O . 0 0 1 ] and female sex ( A O R , 1.6; 95%o CI, 1.10-2.35, P=0.01). Spontaneous clearance of H C V was inversely associated with the use (versus no use) of any i l l ici t drugs ( A O R , 0.54; 95%> CI , 0.29-1.0, P=0.05) and H I V infection ( A O R , 0.58; 95% CI , 0.38-0.88, P=0.01). In order to identify whether H I V infection impacts H C V clearance or persistence, we identified 51 subjects in whom we could establish the order o f H C V and H I V infections based on documented timing of H C V and H I V seroconversion. In total, 48/51 (94%) individuals acquired H C V infection a median o f 2.4 (0.2 - 10) years before being diagnosed with H I V . 2.4 DISCUSSION W e investigated the rate and characteristics associated with H C V clearance among inner city residents in Vancouver in a large, community-based cohort consisting mainly o f i l l ici t drug users. We documented that 23.5% of individuals, in whom testing for H C V antibodies and viremia were available, spontaneously cleared their infection. This is consistent with previously reported clearance rates o f 14-46% in non-IDUs (4-8). In our cohort, Aboriginal ethnicity and female sex were associated with an enhanced capacity to clear H C V infection. In contrast, H I V co-infection and il l ici t drug use were associated with increased persistence of H C V infection. Our findings with respect to Aboriginal race are consistent with data from other centers in Canada suggesting that spontaneous H C V clearance may be higher in these individuals (22, 23). A similar finding has recently been published in studies of Alaskan Natives (24). Interestingly, other data suggest that African Americans exhibit decreased rates o f H C V clearance (5, 7, 18). The basis for this association between race and H C V clearance is not well understood. 58 We observed that female sex was associated with increased rates of H C V clearance. This is supported by previously published data (10-14) and a recent systematic review of thirty-one longitudinal studies evaluating the correlates of spontaneous H C V clearance (9). In a pooled analysis of 675 subjects with H C V clearance, the investigators determined that males were significantly less l ikely (OR, 0.43; 95% CI, 0.36-0.53, P O . 0 0 1 ) to clear H C V spontaneously (19%) when compared to females (40%). It has been postulated that H C V clearance in females may be facilitated by estrogen (11, 25). However, this difference could also be attributed to genetic or immunologic differences that have not yet been determined. The association of sex and race with spontaneous H C V clearance speaks to possible roles for host genetics and immunity in viral control. Genetic polymorphisms in a number of immunological proteins involved in the regulation o f cellular immune responses (such as IL-10, IL-19, IL-20 and TNF-alpha) as well as in both H L A class I and II molecules are associated with reduced clearance (26-31). Immunologic studies in Aboriginals suggest a lower genetic tendency to produce IL-10 than Caucasians and a reduced susceptibility to H C V protein induced IL-10 immune responses, implicating a role for the immune system in this enhanced protection (32). It has recently been determined that inhibitory N K cells may be important in H C V clearance, and that differing activity of certain genes encoding interactions between H L A class I molecules and N K cells may play an important role in the efficacy o f this process (33). However, further research is needed in order to understand the associations between host genetics and the immune system with H C V clearance. H I V infection was associated with reduced rates of H C V clearance. Similar observations have been found in studies among United States veterans (18), haemophiliacs (16) and IDUs (7). The results from our study suggest that the majority of i l l ici t drug users are infected with H C V a median of 2.4 years prior to H I V infection, which is consistent with reports from other groups (34). Therefore, given that H C V clearance generally occurs within the first 6-12 months of infection, H I V is most often impacting persistence of H C V rather than its initial clearance in this setting. H I V infection may decrease circulating HCV-specif ic C D 4 and C D 8 T cells that are generally present in higher levels in individuals that cleared H C V infection (35). This preservation of higher C D 4 cell levels, associated with preserved ant i -HCV lymphoproliferative responses, may be reduced or eliminated upon H I V infection (35). Our cohort, as currently recruited, does not provide us with the statistical power to evaluate this hypothesis. 59 In addition, i l l ici t drug use was associated with diminished capacity to resolve H C V infection. Relationships between specific drug use patterns and viral clearance were not detected, though this may reflect sample size. Alternatively, the effect may be of marginal significance, as the overall rate o f H C V clearance in our cohort that included a large proportion of IDUs approximated that previously reported in non-IDU populations. The lower level of viral clearance among those who report injecting may also relate to a higher risk of re-infection. It is interesting to note that data from this cohort (36) and others (37) have demonstrated that H C V re-infection after H C V clearance occurs less frequently than de novo H C V infection in IDUs and non-IDUs alike, suggesting little or no effect of this behavior on the virus-host relationship. This study has a number of limitations, mostly those inherent to observational cohorts. Testing for ant i -HCV antibodies and H C V R N A occurred as clinically indicated. In practice, antibody testing would be done periodically in individuals with such high risk of H C V infection, but less symptomatic patients (who may be more likely to resolve infection) may not be tested for H C V R N A and would be missing from our analysis. Moreover, the majority of H C V R N A testing was performed in recent years because of the increased availability of H C V treatment in this population. Vi ra l clearance was, in some cases, confirmed by a single negative test, which may represent fluctuating low levels of viremia rather than true clearance. Also , given the level of detection of the assay used (<50 IU/mL), some individuals defined as spontaneously clearing H C V infection may have low but undetectable viremia. However, the overall rate of H C V clearance (24%) is consistent with other studies and reassures us that our conclusions are valid. Additionally, not all patients received H C V R N A testing, introducing a potential selection bias against individuals who might not have come forward for more comprehensive testing or were likely to receive follow up care. Drug use was only assessed in the 6 months preceding the questionnaire and historical drug use information was not available. However, the similar demographics and H I V status between the two groups suggest a relative comparability of the groups and would indicate similar testing patterns. A n additional limitation with this study is that many o f the variables such as illicit drug use behaviors were based on patient self-report and may be prone to socially desirable responses. Given the limited currently available data investigating H C V clearance in IDUs, the results of our study provide novel insights into this issue. Our results suggest that Aboriginal ethnicity and 60 female sex may promote clearance (perhaps by enhanced immunological control), while H I V co-infection and ill icit drug use may reduce the likelihood of clearance, presumably by a similar mechanism. Understanding the mechanisms underlying our observations may be helpful in the management of individuals with acute infection. Moreover, the understanding o f factors that promote or hinder the generation of protective immunity may aid in the development of vaccines or improved treatment options for H C V infection. Further studies are required to confirm our observations from a clinical and pathohysiological perspective. This information w i l l be an important step in refining our approach to H C V infection in medical practice. 61 Table 2.1. Characteristics of participants with persistent HCV versus those with HCV clearance. Characteristic HCV Persistence HCV Clearance OR (95% CI) P* (AD+/RNA+) (AD+/RNA-) (N=583), n (%) (N=179), n (%) Sex Male 411 (70.5) Female 172 (29.5) Ethnicity White 389 (66.7) Aboriginal 145 (24.9) Other 49 (8.4) Estimated Age at Infection <30 years 236(40.6) >30 years 345 (59.2) 102 (57.0) 77 (43.0) 82 (45.8) 86 (48.0) 11 (6.2) 81 (47.3) 98 (54.7) 1.8 (1.3-2.6) 0.001 2.8 (2.0-4.0) <0.001 1.1 (0.53-2.1) 0.99 0.83 (0.59-1.2) 0.31 <20 41 (7.1) 21-30 195 (33.6) 31-40 208 (35.8) 41-50 111 (19.1) >50 26 (4.5) Housing Status Unstable 434(74.4) Stable 149 (25.6) Methadone Treatment No Methadone Treatment 368 (63.1) Methadone Treatment 215 (36.9) Jail time No Jail time 446 (76.5) Jail Time 137 (23.5) HBV Co-infection** No Active HBV Infection 559 (95.9) Active HBV Infection 24 (4.1) fflV-1 Co-infection HIV-1 negative 406 (69.6) HIV-1 positive 177 (30.4) 16 (8.9) 65 (36.3) 63 (35.2) 27 (15.1) 8 (4.5) 124 (69.3) 55 (30.7) 125 (69.8) 54 (30.2) 138 (77.1) 41 (22.9) 170 (95.0) 9 (5.0) 138 (77.1) 41 (22.9) 0.85 (0.45-1.6) 0.75 0.78 (0.41-1.5) 0.55 0.62 (0.31-1.3) 0.27 0.79 (0.30-2.1) 0.81 1.3 (0.89-1.9) 0.20 0.74 (0.52-1.1) 0.12 0.97 (0.65-1.4) 0.95 1.2 (0.56-2.7) 0.67 0.68 (0.46-1.0) 0.06 * A s determined by the % or Fisher's exact test as appropriate. 62 Table 2.2. Characteristics of participants with persistent HCV versus those with HCV clearance. Characteristic HCV Persistence (Ab+/RNA+) (N=583), n (%) HCV Clearance (AD+/RNA-) (N=179), n (%) OR (95% CI) P* Alcohol Use** None 323 (55.4) 94 (52.5) - -Any 260 (44.6) 85 (47.5) 1.1 (0.80-1.6) 0.55 Illicit Drug Use** None 42 (7.2) 19 (10.6) - -Any 541 (92.8) 160 (89.4) 0.65 (0.37-1.2) 0.19 Injection Drug Use** None 243 (41.7) 88 (49.1) - -Any 340 (58.3) 91 (50.8) 0.74 (0.53-1.0) 0.09 Injection Cocaine Use** None 306 (52.5) 106 (59.2) - -Any 277 (47.5) 73 (40.8) 0.76 (0.54-1.1) 0.14 Injection Heroin Use** None 388 (66.6) 128 (71.5) - -Any 195 (33.4) 51 (28.5) 0.79 (0.55-1.2) 0.25 Crack Cocaine Use** None 162 (27.8) 56 (31.3) - -Any 421 (72.2) 123 (68.7) 0.85 (0.59-1.2) 0.42 *As determined by the % or Fisher's exact test as appropriate. **In the past 6 months. 63 Table 2.3. Multiple logistic regression of factors associated with clearance of HCV infection. Characteristic AOR 95% CI P Aboriginal Ethnicity (vs. White) 2.9 2.0-4.3 <0.001 Female Sex 1.6 1.1-2.4 0.01 HIV-1 positive 0.58 0.38-0.88 0.01 Any Illicit Drug Use 0.54 0.29-1.0 0.05 64 Figure 2.1. Subject Disposition 3,553 Subjects with Questionnaire Data I 2,117 Subjects Received H C V Ab 1,315 (63.6%) H C V Ab+ Subjects 48 Subjects Excluded (Received H C V Treatment) 762 (58.0%) Subjects with H C V R N A Testing Available H C V Persistence (n=583, 76.5%) [Ab+/RNA+] H C V Clearance (n=179, 23.5%) [Ab+/RNA-] 65 2.5 REFERENCES 1. Shepard CW, Finelli L , Alter MJ . Global epidemiology of hepatitis C virus infection. Lancet Infect Dis 2005;5:558-567. 2. Cox A L , Netski D M , Mosbruger T, Sherman SG, Strathdee S, Ompad D, Vlahov D, et al. Prospective evaluation of community-acquired acute-phase hepatitis C virus infection. Clin Infect Dis 2005;40:951-958. 3. Rehermann B , Nascimbeni M . Immunology of hepatitis B virus and hepatitis C virus infection. Nat Rev Immunol 2005;5:215-229. 4. Gerlach JT, Diepolder H M , Zachoval R, Gruener N H , Jung M C , Ulsenheimer A , Schraut WW, et al. Acute hepatitis C: high rate of both spontaneous and treatment-induced viral clearance. Gastroenterology 2003;125:80-88. 5. Villano SA, Vlahov D, Nelson KE,- Conn S, Thomas DL. Persistence of viremia and the importance of long-term follow-up after acute hepatitis C infection. Hepatology 1999;29:908-914. 6. Seeff L B . Natural history of chronic hepatitis C. Hepatology 2002;36:S35-46. 7. Thomas DL, Astemborski J, Rai R M , Anania FA, Schaeffer M , Galai N , Nolt K , et al. The natural history of hepatitis C virus infection: host, viral, and environmental factors. Jama 2000;284:450-456. 8. Jauncey M , Micallef JM, Gilmour S, Amin J, White PA, Rawlinson W, Kaldor J M , et al. Clearance of hepatitis C virus after newly acquired infection in injection drug users. J Infect Dis 2004; 190:1270-1274. 9. Micallef J M , Kaldor JM, Dore GJ. Spontaneous viral clearance following acute hepatitis C infection: a systematic review of longitudinal studies. J Viral Hepat 2006;13:34-41. 10. Kenny-Walsh E. Clinical outcomes after hepatitis C infection from contaminated anti-D immune globulin. Irish Hepatology Research Group. N Engl J Med 1999;340:1228-1233. 11. Alric L , Fort M , Izopet J, Vinel JP, Bureau C, Sandre K, Charlet JP, et al. Study of host- and virus-related factors associated with spontaneous hepatitis C virus clearance. Tissue Antigens 2000;56:154-158. 12. Inoue G, Horiike N , Michitaka K , Onji M . Hepatitis C virus clearance is prominent in women in an endemic area. J Gastroenterol Hepatol 2000;15:1054-1058. 13. Yamakawa Y , Sata M , Suzuki H , Noguchi S, Tanikawa K . Higher elimination rate of hepatitis C virus among women. J Viral Hepat 1996;3:317-321. 14. Bakr I, Rekacewicz C, E l Hosseiny M , Ismail S, E l Daly M , El-Kafrawy S, Esmat G, et al. Higher clearance of H C V infection in females compared to males. Gut 2006. 15. Zhang M , Rosenberg PS, Brown DL, Preiss L , Konkle B A , Eyster M E , Goedert JJ. Correlates of spontaneous clearance of hepatitis C virus among people with hemophilia. Blood 2006;107:892-897. 66 16. Messick K , Sanders JC, Goedert JJ, Eyster M E . Hepatitis C viral clearance and antibody reactivity patterns in persons with haemophilia and other congenital bleeding disorders. Haemophilia 2001;7:568-574. 17. Krajden M , Shivji R, Gunadasa K , Mak A , McNabb G, Friesenhahn M , Hendricks D, et al. Evaluation of the core antigen assay as a second-line supplemental test for diagnosis of active hepatitis C virus infection. J Clin Microbiol 2004;42:4054-4059. 18. Piasecki B A , Lewis JD, Reddy K R , Bellamy SL, Porter SB, Weinrieb R M , Stieritz DD, et al. Influence of alcohol use, race, and viral coinfections on spontaneous H C V clearance in a US veteran population. Hepatology 2004;40:892-899. 19. Patrick D M , Tyndall M W , Cornelisse PG, L i K , Sherlock C H , Rekart M L , Strathdee SA, et al. Incidence of hepatitis C virus infection among injection drug users during an outbreak of HrV infection. Cmaj 2001;165:889-895. 20. Strathdee SA, Patrick D M , Currie SL, Cornelisse PG, Rekart M L , Montaner JS, Schechter MT, et al. Needle exchange is not enough: lessons from the Vancouver injecting drug use study. Aids 1997;11:F59-65. 21. Tyndall M W , Currie S, Spittal P, L i K , Wood E, O'Shaughnessy M V , Schechter M T . Intensive injection cocaine use as the primary risk factor in the Vancouver HIV-1 epidemic. Aids 2003;17:887-893. 22. Minuk G Y , Zhang M , Wong SG, Uhanova J, Bernstein C N , Martin B, Dawood MR, et al. Viral hepatitis in a Canadian First Nations community. Can J Gastroenterol 2003;17:593-596. 23. Minuk G Y , Uhanova J. Viral hepatitis in the Canadian Inuit and First Nations populations. Can J Gastroenterol 2003;17:707-712. 24. Scott JD, McMahon BJ, Bruden D, Sullivan D, Homan C, Christensen C, Gretch DR. High rate of spontaneous negativity for hepatitis C virus R N A after establishment of chronic infection in Alaska Natives. Clin Infect Dis 2006;42:945-952. 25. Hayashi J, Kishihara Y , Ueno K, Yamaji K , Kawakami Y , Furusyo N , Sawayama Y , et al. Age-related response to interferon alfa treatment in women vs men with chronic hepatitis C virus infection. Arch Intern Med 1998;158:177-181. 26. Thio CL , Goedert JJ, Mosbruger T, Vlahov D, Strathdee SA, O'Brien SJ, Astemborski J, et al. An analysis of tumor necrosis factor alpha gene polymorphisms and haplotypes with natural clearance of hepatitis C virus infection. Genes Immun 2004;5:294-300. 27. Thio CL , Gao X , Goedert JJ, Vlahov D, Nelson K E , Hilgartner M W , O'Brien SJ, et al. HLA-Cw*04 and hepatitis C virus persistence. J Virol 2002;76:4792-4797. 28. Thio CL , Thomas DL, Goedert JJ, Vlahov D, Nelson K E , Hilgartner M W , O'Brien SJ, et al. Racial differences in H L A class II associations with hepatitis C virus outcomes. J Infect Dis 2001;184:16-21. 67 29. Barrett S, Ryan E, Crowe J. Association of the HLA-DRB1*01 allele with spontaneous viral clearance in an Irish cohort infected with hepatitis C virus via contaminated anti-D immunoglobulin. J Hepatol 1999;30:979-983. 30. Thursz M , Yallop R, Goldin R, Trepo C, Thomas HC. Influence of M H C class II genotype on outcome of infection with hepatitis C virus. The HENCORE group. Hepatitis C European Network for Cooperative Research. Lancet 1999;354:2119-2124. 31. Oleksyk T K , Thio C L , Truelove A L , Goedert JJ, Donfield SM, Kirk GD, Thomas DL , et al. Single nucleotide polymorphisms and haplotypes in the IL10 region associated with H C V clearance. Genes Immun 2005;6:347-357. 32. Khatkar S A K , Kaita K and Rempel JD. The impact of H C V core and NS3 proteins on Aboriginal and Caucasian P B M C IL-10 production in response to IFN-a. In: 18th Annual Spring meeting of Canadian Society for Immunology; 2005; Whistler, Canada.; 2005. 33. Khakoo SI, Thio C L , Martin MP, Brooks CR, Gao X , Astemborski J, Cheng J, et al. H L A and N K cell inhibitory receptor genes in resolving hepatitis C virus infection. Science 2004;305:872-874. 34. Thomas DL, Vlahov D, Solomon L, Cohn S, Taylor E, Garfein R, Nelson K E . Correlates of hepatitis C virus infections among injection drug users. Medicine (Baltimore) 1995;74:212-220. 35. Kim A, Schulze Zur Wiesch J, Allen T, Gandhi R, Davis B, Jones A , Robbins G, et al. Virus-specific T-cell Responses and Loss of Spontaneous Control of H C V in HIV+ Individuals. 13th Conference on Retroviruses and Opportunistic Infections 2006:Abstract_84. 36. Grebely J, Conway B , Raffa J, Lai C, Krajden M , Kerr T, Tyndall M . Natural history of hepatitis C virus infection among injection drug users in Vancouver, Canada [Abstract 86]. Hepatology 2005;42:230A. 37. Mehta SH, Cox A, Hoover DR, Wang X H , Mao Q, Ray S, Strathdee SA, et al. Protection against persistence of hepatitis C. Lancet 2002;359:1478-1483. 68 CHAPTER III Hepatitis C Virus Re-infection in Injection Drug Users1 3.1 INTRODUCTION Hepatitis C virus ( H C V ) infection constitutes a major public health burden, affecting more than 170 mil l ion individuals throughout the world (1). Injection drug use has emerged as the primary mode of transmission globally, accounting for more than 75% of incident cases (1). The prevalence of H C V infection in injection drug users (IDUs) is 60-90% (2-4), with 80% of these individuals going on to develop persistent, chronic infection (5). Pharmacologic advances have led to the development of effective treatment regimens leading to a virological "cure" in 50% of H C V infected subjects receiving pegylated interferon in combination with ribavirin (6, 7). Although these outcomes have been replicated in active IDUs (8, 9), there is still concern that the risk o f H C V re-infection through recurrent parenteral exposure wi l l negate the benefits of treatment. In fact, re-infection with H C V after spontaneous clearance has been demonstrated to occur in IDUs with ongoing risk behavior (10, 11), as well as in other groups, including polytransfused children with thalassemia (12) and subjects undergoing liver transplantation (13). Re-infection does occur in chimpanzees rechallenged with H C V after clearance of the original infection (14-17), but the resistance to subsequent H C V infection is relatively greater, which is l ikely related to immune protection (14, 18). In humans, preliminary data from one cohort suggested that IDUs who successfully clear H C V are less l ikely to develop viremia following reexposure to H C V then are previously uninfected individuals (19). Given that a greater proportion of IDUs are receiving treatment for H C V , a clearer understanding of this protection from re-infection and its determinants is important. With this in mind, we compared the rate of H C V re-infection among 1 A version of this chapter has been published. Grebely, J., Conway, B . Raffa, J.D., Lai, C , Krajden, M . and Tyndall, M.W. (2006). Hepatitis C Virus Re-infection in Injection Drug Users. Hepatology. 44(5): 1139-45. "Reprinted with permission of Wiley-Liss, Inc. a subsidiary of John Wiley & Sons, Inc." 69 individuals who had spontaneous H C V clearance with the rate of primary H C V infection among participants in a large observational, community-based cohort. 3.2 PATIENTS AND METHODS 3.2.1 Study Population The Community Health and Safety Evaluation ( C H A S E ) project is a prospective open cohort study designed to evaluate health service use in the Downtown Eastside o f Vancouver. Between January 2003 and June 2004, 3,553 subjects were recruited via community organizations and door-to-door canvassing of a random sample of single occupancy hotels in the community, based on census information. Subjects were eligible for inclusion i f they lived or utilized health services in the community. Study participants received a CDN$10 stipend to complete a short, interviewer-administered questionnaire that gathered information on demographics, health service utilization, H I V testing, H C V testing and recent drug use. Subjects were requested to provide time-limited consent for the researchers to link with specific provincial health services databases using subject names and personal health card numbers in order to acquire historical data, including H C V , H I V and hepatitis B virus ( H B V ) testing performed at the British Columbia Centre for Disease Control and the University of British Columbia Virology Department at St. Paul's Hospital. The University of British Columbia /Providence Health Care Research Ethics Board approved this study. Individuals were defined as H C V uninfected i f the result of their first linked enzyme immunoassay (EIA) test for H C V antibodies ( H C V Ab) was negative. Participants were considered H C V infected i f the results of their first recorded E I A test for H C V antibodies was positive. H C V clearance was defined as the presence of H C V antibodies followed by one subsequent negative test for H C V R N A ( H C V A b + / H C V R N A - ) . H C V persistence was defined as a positive test for H C V antibodies followed by at least one H C V R N A positive test with all subsequent tests remaining positive ( H C V A b + / H C V RNA+) . Individuals with persistent H C V R N A were excluded from analysis except for the evaluation of demographic characteristics. We then compared the incidence of H C V infection between 1992 and 2005 in individuals with ( H C V A b + / H C V R N A - ) and without ( H C V Ab-) previous infection in order to evaluate the effect of prior infection on subsequent infection rates. 70 For the purpose o f this study, the index visit by an uninfected subject was considered the date of the first negative H C V antibody test. The incidence of new cases of H C V infection was measured by an H C V antibody negative test and a subsequent positive test during follow-up ( H C V A b - / H C V Ab+), with the date of H C V infection estimated as the midpoint between the last H C V antibody negative test and the first H C V antibody positive test. During the follow-up period, the incidence of H C V re-infection was determined by the detection of H C V R N A following spontaneous clearance of H C V ( H C V A b + / H C V R N A - / H C V RNA+) , with the date of H C V re-infection estimated as the midpoint between the last H C V R N A negative test and the first H C V R N A positive test after clearance. Follow-up for individuals developing viremia was defined as the time from the index visit to the date of re-infection or infection. For individuals who remained clear o f viremia, this was defined as the time from the index visit to the date of the most recent negative H C V R N A test or H C V antibody test in previously infected and previously uninfected subjects, respectively. 3.2.2 Laboratory Testing A l l virology testing was performed at 2 certified provincial laboratories between 1992 and 2005. H C V antibody testing was performed using first-, second- or third-generation enzyme-linked immunosorbent assays (May 1992 to September 1993: U B I H C V E I A v2.0 [Organon Teknika, Durham, N C ] ; October 1993 to July 1994: U B I H C V E I A v2.1 [Organon Teknika, Durham, N C ] ; August 1994 to March 1997: U B I H C V E I A v4.0 [Organon Teknika, Durham, N C ] ; Apr i l 1997 to present: A x S Y M H C V v3.0 [Abbott Diagnostics, Chicago, IL]). Specimens reactive for ant i -HCV antibodies were retested by a second or third generation Recombinant Immunoblot Assay (Chiron, Emeryville, C A ) until 1999 to confirm the E I A specificity. Between Apr i l 1997 and July 1999, A x S Y M H C V v3.0 ant i -HCV reactive specimens were retested by U B I H C V v4.0 and from August 1999 to the present time, A x S Y M H C V v3.0 reactive samples are retested by Ortho Eel (Ortho Diagnostics, Mississauga, Canada). Only specimens reactive by both manufacturers' tests were considered to be an t i -HCV reactive. The presence or absence of viremia was detected by H C V R N A testing performed when requested by a physician. Since January 1998, H C V R N A testing has been performed by the qualitative C O B A S A M P L I C O R H C V Test v2.0 (limit of detection: 50 IU/mL, Roche Diagnostic Systems, Mississauga, Ontario, Canada). To ensure specimen integrity, H C V R N A 71 testing was performed using dedicated serum samples separated within 4-6 hours of collection or E D T A plasma separated within 3-5 days of collection. H B V and H I V status were determined by confidential record linkage to the British Columbia Centre for Disease Control virology testing database. 3.2.3 Statistical Analysis Variables of interest in this analysis included age, ethnicity, housing status, alcohol use, injection drug use, non-injection ill icit drug use, previous H B V infection and H I V status. The age o f a participant was determined as the age on the date the questionnaire was administered. Unstable housing was defined as l iving in a shelter, rooming house or single occupancy hotel or as l iv ing on the street/being homeless. Illicit drug use behavior was defined as the use o f injection cocaine, injection heroin, injection crystal methamphetamine, as well as the use of heroin, crack cocaine and crystal methamphetamine though inhalation. Illicit drug use, injection drug use and alcohol use in the past six months was categorized as 'frequent,' i f used everyday/most days; 'any,' i f any reported use in the preceding 6 months; or "none," i f no use reported. Exposure to H B V was defined as having had historical positive tests for H B V surface antigen or anti-hepatitis B core total. H I V status was determined by a confidential record linkage to the British Columbia Centre for Disease Control H I V testing database or by subject self-report. W e compared characteristics of subjects with and without previous H C V infection using 2-sample t-test for quantitative variables and the x2 or Fisher's Exact Test, as appropriate, for testing differences between two proportions. We also compared the characteristics of subjects with and without incident H C V infection using x or Fisher's Exact Test, as appropriate. A multiple logistic regression model comprising potential confounders was used to assess i f previous H C V infection was independently associated with reductions in the incidence of H C V infection. Differences were considered statistically significant at P < .05 and all reported p-values are 2-sided. 3.3 RESULTS O f the 3,553 subjects enrolled into the cohort, 2,117 (59.6%) had H C V antibody testing (Fig. 1). Forty-eight subjects reported having previously received treatment for H C V infection and were excluded from further analysis. A t baseline, we identified 926 subjects (43.7%) uninfected with H C V , as documented by negative testing for H C V antibodies. The remaining 1,143 individuals 72 (55.2%) were H C V antibody positive on their first recorded test. H C V R N A testing was available in 658 of these subjects. No significant differences were observed in the demographics between H C V antibody positive individuals that did receive H C V R N A testing and those who did not, including age (P=0.87), male sex (P=0.95), i l l icit drug use (^=0.27) and H I V infection (P=0.32). However, subjects who did not receive H C V R N A testing were more likely to have engaged in recent injection drug use (62.9% vs. 54.4%, ^=0.004). After identifying 506 individuals with persistent H C V infection on the basis of being H C V R N A positive, we found 152 (23.1%) with spontaneous clearance of viremia. A comparison between the participants without previous H C V infection and those with H C V clearance is shown in Table 1. The two groups were similar in sex (P=0.41) and housing status (P=0.84); however, individuals with previous H C V clearance were older (43.7 years vs. 41.2 years, .PO.001), more likely to be of Aboriginal ethnicity (50.3% vs. 29.0%, P O . 0 0 1 ) , more likely to have previous H B V infection (5.9% vs. 1.3%, P<0.001) and more likely to be co-infected with H I V (23.5% vs. 7.3%, P O . 0 0 1 ) than those previously uninfected with H C V . Although there was no difference in the proportion of subjects who engaged in any il l ici t drug use (i^=0.50), individuals previously infected with H C V were more l ikely to be engaged in frequent i l l ici t drug use (68.0% vs. 55.2%, P=0.004) and injection drug use (any; 48.0% vs. 26.0%, P O . 0 0 1 , frequent; 24.8% vs. 13.9%, P O . 0 0 1 ) . The median follow-up time beyond the index visit for individuals with clearance of viremia (n=152) was 5.2 years (IQR, 2.8-7.4) compared to 2.8 years (IQR, 1.4-5.0) for individuals without previous H C V infection (Table 2). The overall prevalence of H C V infection in this cohort was 63.6% (1315/2069), including in 172 previously uninfected individuals. The occurrence of H C V infection was lower in individuals with previous infection (14/152, 9.2%) than in those without previous infection (172/926, 18.6%). After accounting for duration of follow-up, the incidence of H C V infection was 5 times lower in those previously infected with H C V (1.8 cases/100 person-years; 95% Confidence Interval [CI], 0.9-3.0 cases/100 person-years) than those without previous infection (8.1 cases/100 person-years; 95% CI, 6.9-9.4 cases/100 person-years). This occurred despite those with previous H C V infection being at increased risk for H C V acquisition because of higher rates o f H I V co-infection, il l icit drug use and injection drug use. The observed difference could not be explained by a lack of follow-up in previously infected individuals, as the median documented time that those in this group were without viremia was 5.4 years (range, 0-13.5 years). In a 73 logistic regression of individuals with and without incident H C V infection, with previous H C V infection assessed as a covariate along with other potential confounders (age, sex, ethnicity, H I V infection, housing status and il l ici t and injection drug use), individuals with previous H C V infection and viral clearance were still 4 times less likely to develop incident infection than those infected for the first time [adjusted odds ratio, 0.23; 95% CI, 0.10-0.51, P O . 0 0 1 ] . We also evaluated the occurrence o f recurrent H C V viremia in individuals with and without H I V infection and previous viral clearance (Table 3). H C V infection occurred 8 of 117 H I V negative individuals with previous H C V infection (6.8%o) as compared to in 6 of 35 H I V co-infected individuals (17.1%>). After accounting for follow-up, the incidence of H C V infection in H I V negative individuals with previous H C V clearance (1.4 cases/100 person-years; 95%> CI , 0.7-2.9 cases/100 person-years) remained 2 times below that in H I V co-infected individuals (2.8 cases/100 person-years; 95%> CI, 1.0-6.1 cases/100 person-years). O f the 14 subjects with H C V re-infection, 13 had ongoing cocaine use, 9 by injection (Table 4), and 6 were H I V positive. H C V viremia was cleared a second time in 4 subjects (29%), despite ongoing cocaine use by all 4. None of the 4 subjects that cleared H C V a second time were co-infected with H I V at the time they cleared H C V . 3.4 DISCUSSION In this study of a large community-based cohort of inner-city residents of Vancouver, we have demonstrated that individuals who successfully clear H C V infection have a lower risk of acquiring H C V infection than individuals without previous H C V infection, despite the former group appearing to be at higher risk o f exposure. This protection was tracked over a median of 5 years. The overall rate o f clearance of H C V viremia was 23.1%, which is consistent with published data for non-IDUs (20). H C V re-infection with viremia occurred in only 10 of 152 subjects (6.6%), despite 90% of them continuing to engage in il l icit drug use, including 50%> who reported injection drug use. These findings are not surprising, given that re-infection with H C V after spontaneous clearance is well described in IDUs with ongoing risk behaviors (10, 11). 74 After adjusting for potential confounding variables, individuals with previous clearance o f H C V infection were four times less likely to be re-infected with H C V than were individuals infected for the first time. Therefore, we believe these different rates were not associated with epidemiological differences in the two populations. In fact, these data are consistent with results from another cohort of IDUs in Baltimore, which showed that over a 2 year period IDUs with H C V clearance had an incidence of infection of 6.0 cases/100 person-years in IDUs compared to that of previously uninfected IDUs of 10.5 cases/100 person-years (19). Although our patient population may have differed in important ways from that cohort in race and ethnicity, H I V infection and injection drug use, we observed a similar protection in subjects with previous H C V infection. H I V infected subjects with previous H C V clearance were 2 times more likely to demonstrate recurrence of H C V viremia (2.8 cases/100 person-years) than those without H I V (1.4 cases/100 person-years). Although it was not possible to definitively establish the order of H I V and H C V infections for some participants in this study, data suggest that 90-95% of H I V infections in IDUs occur after H C V infection (3). A s such, this suggests that H I V may be affecting the persistence of H C V rather than its initial clearance. H I V infection may decrease circulating HCV-specif ic C D 4 and C D 8 T cells, higher levels of which are generally found in individuals with H C V clearance, leading to either re-infection with H C V or the re-emergence of low-level viremia that may have been undetectable by conventional assays for a period (21). Our data lend support to the hypothesis that previous exposure to H C V may be protective, possibly on an immunologic basis, despite repeated exposure to H C V . In chimpanzees, re-infection with H C V leads to an attenuated course of infection, with the level and duration of viremia markedly reduced and no evidence of liver disease (15-17). The level of viremia has been linked to the nature of the cellular C D 4 and C D 8 T-cell responses. The in vivo depletion o f memory C D 4 T-cells prior to re-infection results in persistent viremia with a failure to resolve H C V infection (22), despite functional memory CD8 T-cell responses in the liver. Similarly, in vivo depletion of C D 8 T-cell responses results in prolonged H C V viremia that is not controlled until HCV-specif ic C D 8 T-cells recover in the liver (17). Importantly, it seems that with a rapid, multiantigen T-cell proliferative response, chimpanzees can develop protective immunity that prevents re-infection with both the same and different genotypes of H C V (16, 23). This may also be the case in humans. In one study that considered 3 IDUs with clinical evidence of H C V re-75 infection and subsequent clearance, it was demonstrated that clearance was associated with more vigorous CD4+ T-cell responses when compared to patients with acute and chronic H C V infection (24). Further data evaluating viral sequence evolution in IDUs showed that despite ongoing injection drug use during the year of observation, subjects with H C V clearance and H C V persistence demonstrated protection against both re-infection with H C V and superinfection with a different viral genotype, respectively (25). There are at least two other potential explanations for these results. It has been demonstrated that genetic polymorphisms in some H L A class I and II molecules (26, 27) and genes encoding interactions between H L A class I molecules and N K cells (28) are associated with clearance o f H C V infection. Thus, it is possible that those with H C V clearance are a selected group with genetic characteristics protecting against initial H C V infection and subsequent re-infection. Alternatively, given that this study was originally designed to evaluate health utilization, it lacks detailed information on needle sharing, equipment sharing and historical drug use. This is important, as individuals previously exposed to H C V may be more experienced and have safer injection routines and thus may be less l ikely to share injection equipment with others. Such a behavioral difference (which would protect against H C V re-infection) would not be detected in this study. However, given the higher rate of H I V infection in those with previous clearance, it is more l ikely that those with H C V clearance remain at higher risk o f acquiring H C V infection over time. This report has a number of limitations inherent to large retrospective studies. Virologic test results were obtained from a historical database that included antibody assays that changed and improved over time. This is particularly relevant to the H C V antibody tests, which may have been less sensitive prior to 1996. In addition, testing was not systematically done, only on physician request, so that subjects who cleared H C V viremia and were later re-infected may have been misclassified as having persistent infection. In some cases, virologic clearance was confirmed by a single negative test, which may have represented fluctuating low level viremia rather than true clearance. This may have overestimated the re-infection rate. Also , some individuals with H C V clearance may have had low-level viremia that was below the limit o f detection of the assay (50 IU/mL) and may never have truly cleared their H C V infection. If this were true of some individuals, it would make our analysis a minimum estimate of the difference between the two groups. In addition, not all patients received H C V R N A testing, introducing a 76 potential selection bias. However, the similar demographics and H I V status between the two groups would indicate similar testing patterns. Further, the incidence o f primary H C V infection in individuals without previous infection may also be underestimated because o f nonsystematic testing for viremia, once again making our analysis a minimum estimate of the difference between the two groups. A l l of the limitations we have raised are best addressed within the context o f a prospective cohort study with systematic laboratory testing for H C V . Treatment for H C V infection is often withheld from IDUs because o f the perceived high risk o f subsequent H C V re-infection after treatment, reducing the impact o f treatment on the evolution of the H C V epidemic. However, our data suggest that spontaneous clearance may confer some protection against re-infection. If protection against H C V infection extends to those who have cleared their viremia following antiviral therapy, it could provide a stronger rationale for expanding treatment programs for IDUs, including those who continue to be at risk for H C V exposure. Although preliminary data suggest that lower rates of re-infection are observed after the treatment-induced clearance of H C V infection in IDUs compared to the incidence of H C V infection in uninfected individuals (29, 30), this must be confirmed in prospective cohorts. Given that re-infection can occur, it is critical to educate patients about the risk of H C V re-infection associated with needle and equipment sharing. In conclusion, further research is required to investigate the mechanism of the effect we have described in order to define its magnitude and establish how it applies to treated individuals. A s IDUs continue to drive the H C V epidemic in developed countries, it is quite clear that any efforts at its control must include a comprehensive strategy to address the disease in this target population. The results of this study provide some assurance that such strategies could be successfully implemented to limit the impact of H C V in IDUs and in the general population. 77 Table 3.1. Characteristics of participants without previous infection versus those with HCV clearance. Characteristic Previously Uninfected HCV Clearance P* HCV Ab- HCV Ab+/HCV RNA-(n=926), n (%) (n=152), n (%) Age (years, mean [SD]) 41.2 [11.3] 43.7 [7.7] <0.001 Male Sex 628 (67.4) 93 (60.8) 0.41 Ethnicity White 541 (58.4) 69 (45.1) -Aboriginal 269 (29.0) 77 (50.3) <0.001 Other 116 (12.6) 7 (4.6) 0.089 HIV-infected 68 (7.3) 35 (23.0) <0.001 Previous HBV infection 12 (1.3) 9 (5.9) <0.001 Unstable Housing 646 (69.8) 105 (68.6) 0.84 Illicit Drug Use Any 801 (86.5) 135 (88.9) 0.50 Frequent 511 (55.2) 104 (68.0) 0.004 Injection Drug Use Any 241 (26.0) 73 (48.0) <0.001 Frequent 129 (13.9) 38 (24.8) <0.001 *Student's Two Sample T-Test for Age, % 2 or Fisher's exact test as appropriate for all other comparisons of associations. 78 Table 3.2. Occurrence of HCV viremia in all participants without previous infection versus those with HCV clearance. Characteristic Previously Uninfected HCV Clearance HCV Ab- HCV Ab+/ HCV RNA-(n=926), n (%) (n=152), n (%) Person-years of follow-up 2127 Median Follow-up (years) 2.8 Occurrence of Viremia 172/926(18.6%) Incidence (/100 person-years, 95% CI) 8.1 (6.9-9.4) 793 5.2 14/152 (9.2%) 1.8 (0.9-3.0) 79 Table 3.3. Occurrence of HCV viremia in HIV negative and HIV positive previously infected individuals with HCV clearance (n=152). Characteristic HCV Clearance HCV Ab+/ HCV RNA-HIV negative (n=117) HCV Clearance HCV Ab+/ HCV RNA-HIV positive (n=35) Person-years of follow-up 581 Median Follow-up (years) 5.0 Occurrence of Viremia 8/117 (6.8%) Incidence (/100 person-years, 95% CI) 1.4 (0.7-2.9) 212 5.4 6/35 (17.1%) 2.8 (1.0-6.1) 80 Table 3.4. Characteristics of participants with HCV re-infection. ID 1995-97 1998 1999 2000 2001 2002 2003 2004 2005 HIV Drugs 1 Ab+/RNA- RNA+ RNA+ RNA+ RNA+ Y Crack 2 Ab+ RNA- RNA-/RNA+ RNA- Y ID Coc 3 Ab+ RNA- RNA+/RNA+ Y Crack 4 Ab+ RNA- RNA+ RNA-/RNA- N ID Coc/Crack 5 Ab+ RNA+/RNA- RNA+/RNA+ N ID Coc 6 Ab+ RNA- RNA+ Y ID Coc 7 Ab+ RNA+ RNA+ RNA- RNA-/RNA+ N ID Coc/Crack 8 Ab+/RNA-/RNA+ RNA- RNA- N ID Coc/Crack 9 Ab+ RNA- RNA+ RNA- Y Crack 10 Ab+ RNAVRNA- RNA- RNA+/RNA- RNA+ N ID Coc 11 Ab+ RNA- RNA+ N Crack 12 Ab+ RNA-/RNA+ N ID Coc 13 Ab+ RNA- RNA+ N None 14 Ab+ RNA- RNA+ Y ID Coc/Crack Figure 3.1. Subject Disposition 3,553 Subjects with Questionnaire Data I 2,117 Subjects Received H C V Ab 1,143 (54.0%) H C V Ab+ Subjects I 658 (57.6%) Subjects with H C V R N A Testing Available H C V Persistence (n=506, 76.9%) • [Ab+/RNA+] H C V Clearance (n=152, 23.1%) [Ab+/RNA-] 48 Subjects Excluded (Received H C V Treatment) 926 (43.7%) H C V Ab-Subjects T h i s figure is derived from the same population of individuals discussed in Figure 2.1 (p.65) of Chapter II. The initial cohort of 3,553 subjects, 2,117 of whom received H C V antibody testing and 48 of whom were exclude for having previously received H C V treatment are identical. The 1,143 H C V Ab+ subjects in Table 3.1 are a subset of the 1,315 subjects in Figure 2.1 after having excluded 172 individuals that were initially H C V uninfected (HCV Ab-, n=926) and subsequently became infected during follow-up. The numbers of subjects in the other boxes in this figure were then adjusted as appropriate. 82 REFERENCES 1. Shepard CW, Finelli L , Alter M J . Global epidemiology of hepatitis C virus infection. Lancet Infect Dis 2005;5:558-567. 2. van Ameijden EJ, Coutinho R A . Maximum impact of HIV prevention measures targeted at injecting drug users. Aids 1998;12:625-633. 3. Thomas DL, Vlahov D, Solomon L, Cohn S, Taylor E, Garfein R, Nelson K E . Correlates of hepatitis C virus infections among injection drug users. Medicine (Baltimore) 1995;74:212-220. 4. Patrick D M , Tyndall M W , Cornelisse PG, L i K , Sherlock C H , Rekart M L , Strathdee SA, et al. Incidence of hepatitis C virus infection among injection drug users during an outbreak of HIV infection. Cmaj 2001;165:889-895. 5. Thomas DL, Seeff L B . Natural history of hepatitis C. Clin Liver Dis 2005;9:383-398, vi. 6. Manns MP, McHutchison JG, Gordon SC, Rustgi V K , Shiffman M , Reindollar R, Goodman ZD, et al. Peginterferon alfa-2b plus ribavirin compared with interferon alfa-2b plus ribavirin for initial treatment of chronic hepatitis C: a randomised trial. Lancet 2001;358:958-965. 7. Fried M W , Shiffman M L , Reddy K R , Smith C, Marinos G, Goncales FL, Jr., Haussinger D, et al. Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection. N Engl J Med 2002;347:975-982. 8. Dore GJ, Thomas DL. Management and treatment of injection drug users with hepatitis C virus (HCV) infection and HCV/human immunodeficiency virus coinfection. Semin Liver Dis 2005;25:18-32. 9. Grebely J, Raffa J, Meagher C, Duncan F, Viljoen M , Khara M , Mead A, et al. Treatment of hepatitis C virus infection in previous and current injection drug users. In: In Programs and Abstracts of the 17th International Conference on the Reduction of Drug Related Harm; 2006; Vancouver, Canada.; 2006. 10. Proust B, Dubois F, Bacq Y , Le Pogam S, Rogez S, Levillain R, Goudeau A . Two successive hepatitis C virus infections in an intravenous drug user. J Clin Microbiol 2000;38:3125-3127. 11. Micallef JM, Jauncey M , Amin J, Rawlinson W, Gilmour S, van Beek I, Kaldor JM, et al. Hepatitis C virus re-infection within a cohort of injecting drug users [Abstract 229]. Hepatology 2003;38:266A. 12. Lai M E , Mazzoleni AP, Argiolu F, De Virgilis S, Balestrieri A , Purcell R H , Cao A , et al. Hepatitis C virus in multiple episodes of acute hepatitis in polytransfused thalassaemic children. Lancet 1994;343:388-390. 13. Tisone G, Baiocchi L , Orlando G, Palmieri GP, Pisani F, Rapicetta M , Strati F, et al. Hepatitis C reinfection after liver transplantation in relation to virus genotype. Transplant Proc 1999;31:490-491. 14. Farci P, Alter HJ, Govindarajan S, Wong DC, Engle R, Lesniewski RR, Mushahwar DC, et al. Lack of protective immunity against reinfection with hepatitis C virus. Science 1992;258:135-140. 83 15. Nascimbeni M , Mizukoshi E, Bosmann M , Major M E , Mihalik K , Rice C M , Feinstone SM, et al. Kinetics of CD4+ and CD8+ memory T-cell responses during hepatitis C virus rechallenge of previously recovered chimpanzees. J Virol 2003;77:4781-4793. 16. Lanford RE, Guerra B, Chavez D, Bigger C, Brasky K M , Wang X H , Ray SC, et al. Cross-genotype immunity to hepatitis C virus. J Virol 2004;78:1575-1581. 17. Shoukry N H , Grakoui A , Houghton M , Chien D Y , Ghrayeb J, Reimann K A , Walker C M . Memory CD8+ T cells are required for protection from persistent hepatitis C virus infection. J Exp Med 2003;197:1645-1655. 18. Wyatt CA, Andrus L , Brotman B, Huang F, Lee D H , Prince A M . Immunity in chimpanzees chronically infected with hepatitis C virus: role of minor quasispecies in reinfection. J Virol 1998;72:1725-1730. 19. Mehta SH, Cox A , Hoover DR, Wang X H , Mao Q, Ray S, Strathdee SA, et al. Protection against persistence of hepatitis C. Lancet 2002;359:1478-1483. 20. Seeff L B . Natural history of chronic hepatitis C. Hepatology 2002;36:S35-46. 21. K im A , Schulze Zur Wiesch J, Allen T, Gandhi R, Davis B, Jones A, Robbins G, et al. Virus-specific T-cell Responses and Loss of Spontaneous Control of H C V in HIV+ Individuals. 13th Conference on Retroviruses and Opportunistic Infections 2006:Abstract_84. 22. Grakoui A , Shoukry N H , Woollard DJ, Han JH, Hanson H L , Ghrayeb J, Murthy K K , et al. H C V persistence and immune evasion in the absence of memory T cell help. Science 2003;302:659-662. 23. Bassett SE, Guerra B , Brasky K , Miskovsky E, Houghton M , Klimpel GR, Lanford RE. Protective immune response to hepatitis C virus in chimpanzees rechallenged following clearance of primary infection. Hepatology 2001;33:1479-1487. 24. Weseslindtner L, Aberle JH, Gurguta C, Steindl-Munda P, Popow-Kraupp T, Ferenci P, Holzmann H . Reinfection with the hepatitis C virus: kinetics of viral clearance and multi-parameter analysis of CD4+ T-cell response [Abstract 447]. J Hepatol 2006;44:S167. 25. Dove L, Phung Y , Bzowej N , Kim M , Monto A , Wright TL . Viral evolution of hepatitis C in injection drug users. J Viral Hepat 2005;12:574-583. 26. Thio C L , Thomas D L , Goedert JJ, Vlahov D, Nelson K E , Hilgartner M W , O'Brien SJ, et al. Racial differences in H L A class II associations with hepatitis C virus outcomes. J Infect Dis 2001;184:16-21. 27. Thio C L , Gao X , Goedert JJ, Vlahov D, Nelson K E , Hilgartner M W , O'Brien SJ, et al. HLA-Cw*04 and hepatitis C virus persistence. J Virol 2002;76:4792-4797. 28. Khakoo SI, Thio C L , Martin MP, Brooks CR, Gao X , Astemborski J, Cheng J, et al. H L A and N K cell inhibitory receptor genes in resolving hepatitis C virus infection. Science 2004;305:872-874. 29. Backmund M , Meyer K , Edlin BR. Infrequent reinfection after successful treatment for hepatitis C virus infection in injection drug users. Clin Infect Dis 2004;39:1540-1543. 84 30. Dalgard O. Follow-up studies of treatment for hepatitis C virus infection among injection drug users. Clin Infect Dis 2005;40 Suppl 5:S336-338. 31. Fischer B, Vasdev S, Haydon E, Baliunas D, Rehm J. [Willing to undergo hepatitis C treatment in a sample of injection drug users in Toronto, Canada]. Presse Med 2005;34:1209-1212. 85 CHAPTER IV Directly Observed Therapy for the Treatment of Hepatitis C Virus Infection in Current and Former Injection Drug Users1 4.1 INTRODUCTION Hepatitis C virus ( H C V ) infection remains a significant global health burden, with over 170 mil l ion individuals infected worldwide (1). Only ~25% w i l l spontaneously clear H C V viremia, with the remainder progressing to chronic disease (2). Injection drug use (IDU) remains the primary mode of H C V acquisition, with >50% of prevalent cases and >75% of incident cases associated with this risk behavior (1). The high transmissibility of H C V via needlestick and the presence of a large reservoir o f chronic H C V carriers in this population results in H C V prevalence rates ranging between 60 and 90% (1). However, despite this growing epidemic in many urban centres, very few IDUs have received treatment for H C V infection. Response rates of 50-55% are generally observed in patients receiving pegylated interferon alfa-2a or alfa-2b in combination with twice daily ribavirin for 24-48 weeks (dependant on genotype), a figure is ~80% in a subgroup of individuals carrying H C V genotype 2 or 3 infection (3-6). Current treatment guidelines advocate for treatment of H C V infection in current and former IDUs on an individual basis under specific circumstances (7-9). Despite these recommendations, very few IDUs have actually received treatment to date. This is based on concerns about patient motivation and adherence, medical and psychiatric co-morbidity, re-infection due to recurrent risk behaviors and the lack o f infrastructure to ensure access to care during treatment. However, preliminary reports from some centres have confirmed that many IDUs are motivated to receive treatment (10-12), and may be more likely to do so i f this is coupled with a comprehensive approach to their medical and psychiatric needs (including a systematic addiction treatment program) within existing infrastructures, perhaps with directly observed therapy (DOT). However, to date, no study has evaluated D O T for the treatment of 1 A version of this chapter has been submitted for publication. Grebely, J., Raffa, J.D., Meagher, C., Duncan, F., Genoway, K . A . , Khara, M . , McLean, M . , Mead, A. , Viljoen, M . , deVlaming, S., Fraser, C. and Conway, B. (2007) Directly Observed Therapy for the Treatment of Hepatitis C Virus Infection in Current and Former Injection Drug Users. Journal of Gastroenterology and Hepatology. "Reproduced with permission, Blackwell Publishing, J Gastro Hepatol 2007:In Press." 86 H C V infection. With this in mind, the present study evaluates the safety and efficacy of treatment of H C V infection in current and former IDUs enrolled in a structured D O T program. 4.2 PATIENTS AND METHODS A l l patients were HCV-infected IDUs attending one o f two multidisciplinary health clinics located in the inner city of Vancouver (the Pender Community Health Centre) or Victoria (the Cool A i d Community Health Centre) in British Columbia, Canada. The clinics offer addiction services such as methadone maintenance therapy, needle exchange, counseling and prevention. In addition to this, other available services included primary care, nursing, addiction counseling, and on-site consultation with infectious diseases specialists. M e n and women >19 years of age, with detectable H C V R N A by polymerase chain reaction (PCR), non-cirrhotic, with alanine aminotransferase ( A L T ) levels >1.5 times the upper limit of normal ( U L N ) and in whom there was a reasonable expectation of adherence to therapy were eligible for inclusion in this prospective, observational study. Patients with any cause for chronic liver disease other than H C V , pregnant or breastfeeding women, those with active H B V infection and those with active suicidal ideation, psychosis or mania were excluded from study participation. Patients were also excluded i f judged inappropriate for immediate treatment by their primary care physician, based on their medical or psychiatric condition, or their current addiction status. Active (drug abstinence < 6 months) or former (drug abstinence >6 months) injection drug use was not a contraindication for receiving treatment. Physicians who are addiction specialists at the clinic completed the initial medical evaluation. At baseline, all patients underwent a complete medical history and physical examination. Nursing staff also provides risk behavior education and provides education about the treatment and potential side effects. Patients were required to see an addictions counselor to assess psychiatric status (specifically depression and suicide risk), social stability and current or former i l l ici t drug use behaviors. Once therapy was initiated, patients attended the clinic weekly to be formally evaluated by the nurse and to receive their weekly injections. During these visits, the nurses specifically documented adherence to ribavirin, assessed medication-associated toxicity and ensured appropriate longitudinal monitoring was conducted. Illicit drug use was documented and 87 blood tests were performed according to the standard o f care. Patients maintained frequent contact with physicians for biweekly prescription of methadone and medications needed to address treatment-associated toxicities. Addiction counselors were available on site to provide additional individual support, as required, with particular attention to exacerbation of depression. For the majority of subjects attending our clinics, H C V medication is provided free o f charge through government programs. Patients received combination therapy with ribavirin ( R B V , 800-1200 mg/day, based on weight) along with interferon-a2b (IFN-cc2b, 3 mil l ion international units thrice-weekly) replaced by pegylated interferon-a2b (PEG-IFN-a2b, 1.5 ug/kg once weekly), as it became available. Patients initiating therapy prior to July 2003 received interferon and ribavirin, while those who received therapy after July 2003 received pegylated interferon and ribavirin. Treatment duration was 48 weeks in subjects infected with H C V genotype 1 received and 24 weeks in those infected with H C V genotypes 2/3. Staff administered all I F N (thrice-weekly) and P E G - I F N (weekly) injections under direct observation and ribavirin was self-administered. Subjects experiencing moderate anemia (<10 g/dL) received a ribavirin dose reduction of 200 mg/day, while subjects experiencing more severe anemia (<8.5 g/dL) were discontinued from therapy. Subjects experiencing moderate hematologic toxicity associated with reductions in white blood cells (<1.5 x 10 9 /L), neutrophils (0.75 x 10 9/L) or platelets (80 x 10 9/L) received a 50% reduction in interferon dose, while those with more significant reductions in white blood cells (<1.0 x 10 9 /L), neutrophils (0.50 x 10 9 /L) or platelets (50 x 10 9 /L) were discontinued from therapy. The primary end point for this prospective, observational trial was sustained virologic response ( S V R ) to interferon-based therapy, defined as an H C V R N A <50 IU/mL at 24 weeks post-treatment ( C O B A S A M P L I C O R H C V Test v2.0, Roche Diagnostic Systems, Mississauga, Canada). Chi-Squared or Fisher's Exact test were used, as appropriate, for all statistical comparisons, which were completed on an intention-to-treat basis. Statistically significant differences were assessed at a significance level of 0.05 and all reported p-values are two-sided. A l l experimental procedures were followed in accordance with the Helsinki Declaration o f 1975. The University of British Columbia Clinical Research Ethics Board approved this study. 88 4.3 RESULTS A total of 40 HCV-infected participants were enrolled in the study (of whom 33 were male and 7 were female). O f these, 12 began treatment before July 2003 and received interferon injections thrice weekly, while the remaining 28 were given pegylated interferon once weekly. The demographics and clinical characteristics of subjects enrolled in this study are shown in Table 1. A l l patients had injection drug use as a risk factor for H C V infection. Fifty three percent of patients were enrolled in a methadone maintenance program, receiving a median dose o f 67 mg/day. Overall, 23 patients (58%) self-reported a previous history of depression and 14 (35%) were receiving antidepressants prior to initiating therapy for H C V infection. Eighteen patients (45%>) had H C V genotype 1, 6 (15%) had genotype 2 and 16 (40%) had genotype 3. Three patients were co-infected with H I V . The disposition of the 40 study subjects is shown in Figure 1. In total, 26 subjects completed the full course of therapy. O f the 14 subjects who did not, 5 subjects experienced treatment-limiting adverse events (1 - nausea/vomiting, 1 - tinnitus, 1 - neutropenia, 1 - depression and 1 - anemia). Three subjects infected with genotype 1 were discontinued from therapy due to lack of an early virologic response ( E V R ) , defined as an undetectable viremia or a 2 logio decrease in H C V R N A by week 12. Six subjects were discontinued from treatment due to non-adherence associated with ongoing ill icit drug use, four of these reporting concomitant depression. In total, 12/14 (86%) discontinuations occurred within the first four months of therapy (Figure 2). A t the beginning of H C V treatment, 14/40 subjects were on antidepressants, with 4/14 (28%) not completing therapy, 2/3 due to depression and/or il l icit drug use and non-adherence. O f the remainder of the population (9/26 reporting a previous history of depression), 4 started on antidepressants during H C V therapy, and 10/26 (38%) did not complete therapy, 4/10 due to depression and/or il l icit drug use and non-adherence. In this population, prior use of antidepressants was not predictive o f successful treatment completion (p = 0.75). A s shown in Figure 3, at the end o f treatment, the proportion of patients responding to H C V therapy was 28 of 40 (70%). However, due to viral relapse in 6 subjects receiving IFN-ct2b (3 subjects) and PEG-IFN-a2b (3 subjects), S V R was observed in only 22 o f 40 subjects (55%). In total, 8/18 (44%) and 14/22 individuals (64%) infected with H C V genotype 1 and H C V 89 genotypes 2/3 had an S V R (Figure 4, P=0.34). Five of twelve individuals (42%) receiving interferon-based therapy achieved an S V R as compared to 17 o f 28 (61%) individuals receiving pegylated interferon-based therapy (Figure 4, P=0.31). Among subjects weighing <75 kg achieved, an S V R was achieved in 60% (9/15) as compared to 52% (13/25) in subjects weighing >75 (P=0.75). Among patients enrolled in a methadone maintenance program, the S V R rate was 52% (11/21) as compared to 58% (11/19) among subjects not receiving methadone (^=0.76). In total, 37% (7/19) and 57% (12/21) of subjects receiving and not receiving methadone used il l ici t drugs during treatment. The median duration of drug abstinence among all patients was 11.5 months. A s shown in Figure 5, there was no difference in S V R among patients that had admitted to drug use in the 6 months preceding therapy (9/14, 64%) and individuals that had not used drugs in the 6 months prior to initiating therapy for H C V infection (13/26, 50%, P=0.5\). Overall, 19/40 patients (48%) used il l ici t drugs at least once during treatment for H C V infection, with 18 subjects (45%) admitting the use of cocaine or heroin. O f these, 9 used cocaine only, 4 used heroin only and 5 used multiple substances. O f the 19 subjects that used drugs, 10 used them occasionally (monthly/two or fewer times) and 9 used them frequently (everyday/every other day). Four of the nine regular users used injection cocaine, one used injection heroin, one used both injection heroin and cocaine and 2 used crack cocaine. The association between drug use during treatment and sustained virologic response is shown in Figure 5. Overall, there was no difference in response rates between subjects that did (12/21, 57%) and did not (10/19, 53%) use ill icit drugs during treatment (P=0.99). However, the sustained virologic response was 57% in individuals without drug use during treatment, 80% among occasional users and 22% among frequent users. However, these differences did not achieve statistical significance (P=0.12). 4.4 DISCUSSION This prospective, observational trial is among the first studies evaluating the antiviral efficacy of I F N a-2b or P E G - I F N a-2b in combination with ribavirin among current and former injection drug users enrolled in a directly observed therapy (DOT) program. Overall, we have demonstrated that 55% of subjects achieved an S V R , despite the fact that many individuals continued to use ill icit drugs throughout their course of treatment. These results are comparable to response rates (54-56%) observed to date in large, randomized controlled trials using P E G -I F N a-2b in combination with ribavirin for the treatment o f H C V infection (3, 5). Our results 90 were achieved despite the fact that 35% of subjects had used il l ici t drugs in the 6 months preceding therapy and that 48%> o f patients used ill icit drugs at least once during their course o f treatment. Pretreatment drug abstinence <6months was not associated with poorer outcomes. This is consistent with data from one study o f 76 current and former IDUs receiving self-administered I F N a-2b plus ribavirin in a community-based setting (13, 14). They observed that a shorter duration o f pre-treatment drug abstinence was not associated with a significant reduction in virologic outcomes (22%> vs. 30%, P=0.1S). Wi th this in mind, the decision to initiate treatment for H C V infection in current and former injection drug users should not be arbitrarily based on a pre-defined period of drug abstinence and must be an individualized decision based on the willingness o f the patient to initiate treatment, social conditions which may impact the stability o f the patient and other medical co-morbidities which may preclude treatment. There are data available to suggest that adherence to pre-treatment appointments may provide a good proxy o f adherence to treatment for H C V infection in i l l ici t drug users (15). Illicit drug use of any kind during treatment for H C V infection was not associated with reduced response rates, unless it exceeds a specific frequency threshold, largely confirming data generated in other evaluations of similar subjects (13, 15-22). In one study of 50 patients offered self-administered treatment with I F N a-2a (n=34) and I F N a-2a plus weight-based ribavirin (n=16), 36%o of patients achieved an S V R , despite the fact that 80% of patients relapsed to il l ici t drug use during treatment (15). O f the 76 subjects receiving I F N a-2b plus ribavirin in a study by Sylvestre et al., 28%> of subjects achieved a sustained virologic response, despite the fact that 59%o used ill icit drugs during treatment (13). Intercurrent drug use was not associated with poorer outcomes (P=0.09). However, 0/8 individuals with drug use every 1-2 days responded to treatment. Data from 12 active IDUs receiving treatment with either I F N or P E G - I F N with or without R B V in a hospital-based setting in Australia demonstrated S V R rates of 50%> (16). In most cases (11/12), drug use occurred at least every week. Based on these data, historical or ongoing il l ici t drug use should not necessarily be considered a contraindication for H C V therapy. However, further prospective studies appropriately powered to address the impact of both i l l ici t drug use prior to and during treatment are needed. 91 There were several limitations to this study. First, this study is a prospective, observational trial. Although a randomized trial comparing D O T to self-administered therapy would be ideal, this was not possible in this setting given that D O T is the standard of care at these sites. Second, it would have been useful to have a comparison group of subjects that did not initiate treatment to understand the factors that are associated with the uptake of H C V treatment in this population. Such a study is currently ongoing in our centre. Lastly, the sample size was relatively small with only 40 patients having initiated treatment. However, these results provide important data supporting the proof-of-concept o f D O T H C V treatment, providing the foundation for future prospective trials with the appropriate comparison groups. A t our centres, a study is underway comparing response rates, costs and patient quality of life after treatment for H C V infection among current and former IDUs receiving care within either a high or low multidisciplinary program. Given the paucity o f data evaluating the treatment of H C V infection in current and former injection drug users, the results from this study provide further evidence to suggest that the treatment of H C V infection in this group can be successful, even despite ongoing substance use during therapy. Our model utilizes the pre-existing infrastructure for the treatment of primary care and addiction within an inner city community health clinic to provide treatment for H C V . Important components of this model include a comprehensive multidisciplinary team and directly observed therapy (DOT). This includes the integration o f administrative staff, nurses, counselors, physicians and researchers (providing the necessary expertise to evaluate the program in an objective manner). Nursing support is an absolutely essential component of the program. Nurses provide patient education prior to and during treatment, assess medication-associated toxicity, and ensure appropriate longitudinal monitoring is conducted as they administer weekly interferon injections. Directly observed monitoring of interferon injections may provide an important means o f engaging subjects and maintaining a continuity of care during treatment. This also allows the multidisciplinary team to immediately address any side effects, ongoing il l ici t drug use, psychiatric issues and adherence issues which may arise. Some have suggested that the use o f antidepressants as a prophylactic measure at the time o f initiation of H C V treatment may help reduce the occurrence of drug-associated depression and reduce the rate of premature treatment discontinuation. In our observational cohort, the patients that started therapy on antidepressants were no more likely to complete it. A number of small 92 studies suggest that prophylactic treatment with antidepressants may be effective in reducing discontinuations associated with IFN-mediated depression (23, 24). However, this issue may be best resolved in a single prospective, randomized controlled study of adequate power. Such a study is already underway in Canada, C T N 194. Given that the future burden of H C V infection w i l l be largely among IDUs, programs for the treatment of H C V in this population must be expanded. Successful pilot programs have been described in a number of centres in North America (13, 21, 25, 26), Europe (15, 17, 19, 20, 22) and Australia (16). Our data add to this body of knowledge, in an era where more convenient formulations of interferon are available, allowing for more cost-effective D O T programs (requiring a single injection every week) to be set up. However, there still exists a considerable knowledge gap in this area. There are no data to recommend the best treatment program for IDUs, including the type and cost o f infrastructure that must be put in place. Strategies for managing the neuropsychiatric side effects of interferon are also needed. Data evaluating H C V re-infection is also sparse. Although there are some data suggesting that prior spontaneous clearance of H C V infection is protective with respect to H C V re-infection (27, 28), it is not clear whether protection against H C V infection extends to those who have cleared their viremia following antiviral therapy. Preliminary data suggests that lower rates of re-infection are observed after the treatment-induced clearance of H C V infection in IDUs when compared to the incidence of H C V infection in uninfected individuals (17, 29), however, this must be confirmed in prospective cohorts. Moreover, given that re-infection w i l l still occur (although perhaps at a lower rate), it is critical to educate patients about the potential risks for H C V re-infection associated with needle and equipment sharing. A s IDUs continue to drive the H C V epidemic throughout the world, it is obvious that any attempt at its control must include systematic programs for the treatment of H C V infection in this population. Ultimately, the components of an effective program may be best evaluated in prospective trials, to allow for the identification of the essential elements of a successful program. Information derived from such trials w i l l lead to the design of guidelines for the approach to HCV-infected IDUs in any situation in which they may be encountered. 93 Table 4.1. Baseline Characteristics Characteristic N=40 Mean Age - years (SD) 42.7 (8.6) Male sex - n (%) 33 (82.5) Body weight - kg Mean (SD) 82.8 (16.8) >75kg-n(%) 25(62.5) Mean Estimated Duration of Infection - years (SD) 13.2 (10.0) Drug Abstinence < 6 months - n (%) 14 (35.0) Median Time - months (IQR) 11.5 (4.8-30.0) On Methadone Maintenance Therapy - n (%) 21 (52.5) Median Methadone Dose - milligrams/day (SD) 67 (36) History of Depression - n (%) 23 (58.0) Pre-treatment with antidepressants - n (%) 14 (35.0) HCV Genotype - n (%) 1 18 (45.0) 2 6 (15.0) 3 16 (40.0) Alanine aminotransferase - U/liter Median (IQR) 139 (87-216) Median Alanine aminotransferase Quotient (IQR) 2.53 (1.58-3.93) Median AST - U/liter (IQR) 93 (60-144) HIV infection - n (%) 3 (7.5) *SD, Standard Deviation; IQR, Interquartile range; U/liter, Units/liter. Figure 4.1. Subject Disposition. AEs, Adverse Events; EVR, early virologic response 40 patients initiated treatment IFN a-2b + RBV (n=12) 0 discontinued due to AEs 1 discontinued due to drug relapse 2 non-responder (Genotype 1 inadequate EVR) Completed Treatment (n=9) 1 PEG-IFN a-2b + RBV (n=28) 5 discontinued due to AEs 5 discontinued due to drug relapse 1 non-responder (Genotype 1 inadequate EVR) Completed Treatment (n=17) 95 Figure 4.2. Number of patients discontinuing interferon-based therapy early. Duration of HCV Therapy (months) Figure 4.3. Virological response to treatment in all patients as measured by H C V RNA. E O T , End of treatment; SVR, sustained virologic response. 100n 80H 60 H 4J a 40 20-0 70% 55% ETR SVR 97 Figure 4.4. Virological response to treatment according to genotype and regimen received as measured by SVR, sustained virologic response. 1001 80-X 60 > ^ 40 20 0 -64% 61% 44% 42% -n=18 n=22 n=12 n=28 G l G2/3 IFN a - 2 b PEG-IFN a-2b Genotype Regimen 98 Figure 4.5. Virological response to treatment according to duration of drug abstinence and intercurrent drug use as measured by SVR, sustained virologic response. 100 -i >6 mos <6 mos None Any Occ Freq Drug Abstinence Illicit Drug Use During Treatment 99 4.5 REFERENCES 1. Shepard CW, Finelli L , Alter M J . Global epidemiology of hepatitis C virus infection. Lancet Infect Dis 2005;5:558-567. 2. Seeff L B . Natural history of chronic hepatitis C. Hepatology 2002;36:S35-46. 3. Fried M W , Shiffman M L , Reddy KR, Smith C, Marinos G, Goncales FL, Jr., Haussinger D, et al. Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection. N Engl J Med 2002;347:975-982. 4. Hadziyannis SJ, Sette H , Jr., Morgan TR, Balan V , Diago M , Marcellin P, Ramadori G, et al. Peginterferon-alpha2a and ribavirin combination therapy in chronic hepatitis C: a randomized study of treatment duration and ribavirin dose. Ann Intern Med 2004;140:346-355. 5. Manns MP, McHutchison JG, Gordon SC, Rustgi V K , Shiffman M , Reindollar R, Goodman ZD, et al. Peginterferon alfa-2b plus ribavirin compared with interferon alfa-2b plus ribavirin for initial treatment of chronic hepatitis C: a randomised trial. Lancet 2001;358:958-965. 6. McHutchison JG, Gordon SC, Schiff ER, Shiffman M L , Lee W M , Rustgi V K , Goodman ZD, et al. Interferon alfa-2b alone or in combination with ribavirin as initial treatment for chronic hepatitis C. Hepatitis Interventional Therapy Group. N Engl J Med 1998;339:1485-1492. 7. Seeff L B , Hoofnagle JH. Appendix: The National Institutes of Health Consensus Development Conference Management of Hepatitis C 2002. Clin Liver Dis 2003;7:261-287. 8. Sherman M , Bain V , Villeneuve JP, Myers RP, Cooper C, Martin S, Lowe C. The management of chronic viral hepatitis: a Canadian consensus conference 2004. Can J Gastroenterol 2004;18:715-728. 9. Reimer J, Schulte B , Castells X , Schafer I, Polywka S, Hedrich D, Wiessing L , et al. Guidelines for the treatment of hepatitis C virus infection in injection drug users: status quo in the European union countries. Clin Infect Dis 2005;40 Suppl 5:S373-378. 10. Doab A , Treloar C, Dore GJ. Knowledge and attitudes about treatment for hepatitis C virus infection and barriers to treatment among current injection drug users in Australia. Clin Infect Dis 2005 ;40 Suppl 5:S313-320. 11. Strathdee SA, Latka M , Campbell J, O'Driscoll PT, Golub ET, Kapadia F, Pollini R A , et al. Factors associated with interest in initiating treatment for hepatitis C Virus (HCV) infection among young H C V -infected injection drug users. Clin Infect Dis 2005;40 Suppl 5:S304-312. 12. Genoway K , Grebely J, Raffa J, Duncan F, Viljoen M , deVlaming S, Khara M , et al. Initiation of Hepatitis C Virus (HCV) Treatment among Injection Drug Users (EDUs) [Abstract We.l42P]. In: Program and Abstracts of the 17th International Conference on the Reduction of Drug Related Harm; 2006 April 30-May 4; Vancouver, Canada; 2006. 13. Sylvestre DL, Litwin A H , Clements BJ, Gourevitch M N . The impact of barriers to hepatitis C virus treatment in recovering heroin users maintained on methadone. J Subst Abuse Treat 2005;29:159-165. 100 14. Sylvestre DL. Treating hepatitis C virus infection in active substance users. Clin Infect Dis 2005;40 Suppl5:S321-324. 15. Backmund M , Meyer K, Von Zielonka M , Eichenlaub D. Treatment of hepatitis C infection in injection drug users. Hepatology 2001;34:188-193. 16. Matthews G, Kronborg IJ, Dore GJ. Treatment for hepatitis C virus infection among current injection drug users in Australia. Clin Infect Dis 2005;40 Suppl 5:S325-329. 17. Dalgard O. Follow-up studies of treatment for hepatitis C virus infection among injection drug users. Clin Infect Dis 2005;40 Suppl 5:S336-338. 18. Dalgard O, Bjoro K , Helium K , Myrvang B, Skaug K , Gutigard B , Bell H . Treatment of chronic hepatitis C in injecting drug users: 5 years' follow-up. Eur Addict Res 2002;8:45-49. 19. Neri S, Bruno C M , Abate G, Ierna D, Mauceri B, Cilio D, Bordonaro F, et al. Controlled clinical trial to assess the response of recent heroin abusers with chronic hepatitis C virus infection to treatment with interferon alpha-n2b. Clin Ther 2002;24:1627-1635. 20. Schaefer M , Schmidt F, Folwaczny C, Lorenz R, Martin G, Schindlbeck N , Heldwein W, et al. Adherence and mental side effects during hepatitis C treatment with interferon alfa and ribavirin in psychiatric risk groups. Hepatology 2003;37:443-451. 21. Van Thiel D H , Anantharaju A , Creech S. Response to treatment of hepatitis C in individuals with a recent history of intravenous drug abuse. Am J Gastroenterol 2003;98:2281-2288. 22. Mauss S, Berger F, Goelz J, Jacob B , Schmutz G. A prospective controlled study of interferon-based therapy of chronic hepatitis C in patients on methadone maintenance. Hepatology 2004;40:120-124. 23. Schaefer M , Schwaiger M , Garkisch AS, Pich M , Hinzpeter A , Uebelhack R, Heinz A , et al. Prevention of interferon-alpha associated depression in psychiatric risk patients with chronic hepatitis C. J Hepatol 2005;42:793-798. 24. Musselman DL, Lawson DH, Gumnick JF, Manatunga A K , Penna S, Goodkin RS, Greiner K , et al. Paroxetine for the prevention of depression induced by high-dose interferon alfa. N Engl J Med 2001;344:961-966. 25. Litwin A H , Soloway I, Gourevitch M N . Integrating services for injection drug users infected with hepatitis C virus with methadone maintenance treatment: challenges and opportunities. Clin Infect Dis 2005;40 Suppl 5:S339-345. 26. Taylor L E . Delivering care to injection drug users coinfected with HIV and hepatitis C virus. Clin Infect Dis 2005;40 Suppl 5:S355-361. 27. Mehta SH, Cox A , Hoover DR, Wang X H , Mao Q, Ray S, Strathdee SA, et al. Protection against persistence of hepatitis C. Lancet 2002;359:1478-1483. 28. Grebely J, Conway B , Raffa J, Lai C, Krajden M , Kerr T, Tyndall M . Natural history of hepatitis C virus infection among injection drug users in Vancouver, Canada [Abstract 86]. Hepatology 2005;42:230A. 101 29. Backmund M , Meyer K , Edlin BR. Infrequent reinfection after successful treatment for hepatitis C virus infection in injection drug users. Clin Infect Dis 2004;39:1540-1543. 102 CHAPTER V Treatment Uptake and Outcomes Among Current and Former Injection Drug Users Receiving Directly Observed Therapy Within a Multidisciplinary Group Model for the Treatment of Hepatitis C Virus Infection1 5.1 INTRODUCTION Hepatitis C virus ( H C V ) is a significant global health burden, with over 170 mil l ion people infected worldwide (1). Injection drug use (IDU) remains the primary mode of H C V acquisition in the developed world (1). However, H C V treatment programs for i l l ici t drug users have not been part o f the response to this explosive epidemic. Reports from Australia and Canada demonstrated that in 2003 and 2004, respectively, only 3-4% o f these individuals had received treatment for H C V infection (2, 3). This low uptake o f H C V treatment is associated with barriers including lack of follow-up with appointments, issues of medical or psychiatric co-morbidity and ongoing substance abuse (4-7). Response rates of - 5 5 % are observed in patients receiving pegylated interferon and ribavirin, a figure that exceeds 80% in individuals carrying H C V genotype 2 or 3 infection (8-11). In the past, guidelines had excluded il l ici t drug users from being considered for therapy unless they had abstained from risk behaviors for H C V transmission for at least 6 months. However, data from our centre (12) and others (13-22) suggest that il l icit drug users can be successfully treated for H C V infection. Programs with the highest success rates tend to use an existing infrastructure for the treatment of addiction into which H C V therapy can be integrated. The key is to ensure engagement in care before, during and after a decision to initiate treatment has been made. However, there are very little data investigating the specific components of various programs that are important for successful treatment of H C V infection in il l icit drug users. 1 A version of this chapter has been accepted for publication. Grebely, J., Genoway, K . A . , Khara, M . , Duncan, F., Viljoen, M . , Elliott, D., Raffa, J.D., deVlaming, S., Fraser, C. and Conway, B . (2007) Treatment Uptake and Outcomes Among Current and Former Injection Drug Users Receiving Directly Observed Therapy Within a Multidisciplinary Group Model for the Treatment of Hepatitis C Virus Infection. International Journal of Drug Policy. "Reproduced with permission, Elsevier, Int J Drug Pol 2007:In Press." 103 One potential strategy for improving outcomes is the development and implementation of support groups for patients leading up to treatment for H C V infection. This provides a mechanism for regularly scheduled follow-up, patient education and peer support that may even be continued during the course of H C V therapy. Wi th this in mind, we sought to evaluate the uptake and response to treatment among current and former IDUs infected with H C V enrolled in a weekly support group designed to enhance long-term engagement in medical care. 5.2 PATIENTS AND METHODS A l l patients were HCV-infected ill icit drug users attending an inner city multidisciplinary health clinic (the Pender Community Health Centre, P C H C ) located in Vancouver, Canada. The P C H C has a mandate to provide primary care for residents o f this area and offers addiction services including methadone maintenance therapy, needle exchange, and counseling. There are up to seven physicians, four registered nurses, six drug and alcohol counselors and on-site consultation with infectious diseases specialists. For this study, we sought to evaluate the rate of H C V treatment initiation and outcomes among individuals attending a weekly support group for H C V infection. Starting in March 2005, subjects with detectable H C V R N A and an interest in receiving H C V treatment were referred by clinic physicians and addiction counselors to the group. The model for support was based on the O.A.S.I.S model developed in Oakland, C A (13). Attendance to the once-weekly group was not mandatory, but was recorded from the first day that the patient attended the group and monitored at subsequent weekly meetings. Addictions counselors moderated the group, with nurses and research staff supporting its conduct. This group provided an opportunity for treatment candidates to interact directly with those that were receiving or had completed treatment and to gain insight into the evaluation of liver disease and what to expect during treatment. Patients who qualified for H C V treatment on medical grounds would then be seen by clinic physicians for H C V evaluation and to plan for the initiation o f therapy. Funding for H C V treatment in British Columbia is provided through government programs and is either partially or fully reimbursed (based on patient income level). The clinical criteria for government reimbursement are: documented viremia, along with either elevated alanine aminotransferase ( A L T ) enzyme levels (1.5 times the upper limit o f normal on 2 occasions at least 3 months apart) or liver biopsy demonstrating at least Knodell stage 2 fibrosis with no 104 evidence of decompensated cirrhosis. M e n and women >19 years o f age who fulfilled government criteria for subsidized treatment and in whom there was a reasonable expectation of adherence to therapy were eligible to receive it. Patients with any cause of chronic liver disease other than H C V , pregnant or breastfeeding women, those with active suicidal ideation, psychosis or mania or those judged inappropriate for treatment by their physician, based on their medical or psychiatric condition, or their current addiction status (daily injection drug use in the setting o f unstable housing) were not offered treatment for H C V infection. Once a patient was judged to be a candidate for treatment (based on attendance to pre-treatment medical evaluations, social stability and absence of medical or psychiatric co-morbidities), a clinic physician completed a medical history and physical examination. Patients underwent testing for H I V , H C V and hepatitis B virus as well as baseline hematology and biochemistry testing. Nursing staff provided education about treatment and side effects. Patients were required to see an addiction counselor to assess psychiatric status (depression and suicide risk), social stability and il l ici t drug use, with an emphasis on ongoing risk for H C V transmission. Once therapy was initiated, patients attended the clinic weekly to be evaluated by a nurse and to receive P E G - I F N injections administered by clinic staff ( R B V was self-administered). During these visits, the nurse specifically documented adherence, i l l ici t drug use, side effects and ensured appropriate longitudinal monitoring was conducted. Interferon adherence was assessed by direct observation and ribavirin adherence was self-reported weekly. Addiction counselors provided additional individual support, with particular attention to symptoms of depression. Subjects initiating therapy were entered into a prospective, observational efficacy trial. Patients received combination therapy with ribavirin (800-1200 mg/day) along with either pegylated interferon-cc2b (PEG-IFN-a2b, 1.5 pg/kg once-weekly) or pegylated interferon-a2a ( P E G - I F N -a2a, 180 pg once-weekly). Treatment duration was 48 weeks ( H C V genotype 1) or 24 weeks ( H C V genotypes 2/3). Staff administered all P E G - I F N injections under direct observation and R B V was self-administered. The primary end point for this trial was end of treatment response (ETR) , defined as having H C V R N A <50 IU/mL at the end o f treatment ( C O B A S A M P L I C O R H C V Test v2.0, Roche Diagnostic Systems, Mississauga, Canada). The Mann-Whitney test was used to assess differences in median attendance between groups of patients, while Fisher's exact test was used to assess differences in proportions. A l l two-sided p-values<0.05 were considered 105 statistically significant. A l l experimental procedures were implemented in accordance with the Helsinki Declaration of 1975. The University of British Columbia Clinical Research Ethics Board approved this study. 5.3 RESULTS Overall, 80 subjects were referred to the group over a period of 80 weeks, with the mean attendance being 12 subjects per week (range 3-20). The disposition of the 80 subjects referred into the program is shown in Figure 1. Among the 8 (10%) in whom it was decided that treatment would not be initiated, 6 did not require treatment, while 2 had contraindications for immediate treatment (1 - diabetes/malnutrition/depression, 1 - severe depression). In total, 23 (29%) were lost to follow-up. Ten percent (8/80) of subjects had completed or initiated treatment for H C V infection prior to attending the group. Twenty-five percent of subjects (20/80) were currently under evaluation for treatment of H C V and 26% (21/80) had initiated or completed treatment for H C V infection. In a comparison of subjects that had initiated or completed treatment for H C V infection (21/80) and those lost to follow up (23/80), those having received treatment for H C V infection had a higher median attendance [22.7 meetings (Interquartile range, IQR = 13-32) vs. 3.4 meetings (IQR=l-5, P<0.001)] and were more likely to attend >3 clinic visits (100% vs. 35%, PO.001) than those lost to follow up. Of the 21 subjects who initiated treatment for H C V infection, 18 received care at this site and were enrolled into a prospective observational study of H C V therapy. The other three received treatment elsewhere. Subjects received either PEG-IFN-a-2a (n=14) or PEG-IFN-a-2b (n=4) in combination with RBV. The demographics and clinical characteristics of the 18 subjects enrolled in this study to date are shown in Tables 1 and 2. A l l patients had IDU as a risk factor for H C V infection. The mean attendance to the weekly group prior to initiating therapy was 79%, while the mean time to treatment initiation after presenting to the group was 9.5 weeks. Of the 18 subjects treated at PCHC, 56% (n=10) had reported illicit drug use in 6 months preceding therapy, while the median time of drug abstinence was 4 months. Seven subjects (39%) were actively using illicit drugs at the time of therapy initiation. A high proportion of treated subjects were infected with H C V genotype 2 (22%) and genotype 3 (56%). Eight subjects (44%) were receiving methadone maintenance therapy. 106 The disposition of the 18 study subjects is shown in Figure 1. Treatment is still ongoing in 6 patients, while 12 have completed or discontinued therapy. O f the 12 that have completed treatment, early discontinuation was required in 8/12 (67%) o f subjects, with 5 experiencing treatment-limiting adverse events (4 - depression and 1 - anemia). Two of the four subjects who discontinued due to depression chose not to receive antidepressants prior to or during treatment for H C V . One subject remained viremic after 24 weeks o f therapy (HIV co-infected). Two subjects were discontinued from treatment due to non-adherence associated with ongoing il l ici t drug use. In total, 12 patients completed or discontinued treatment. A t baseline, 9/12 subjects were receiving prophylactic treatment with antidepressants (7 - citalopram, 1 - venlafaxine, 1 -amitriptyline), while no patient started antidepressants during treatment. The median duration of non-injection and injection drug abstinence among all 12 patients completing therapy was 5 and 8 months, respectively. Nine subjects (75%) used ill icit drugs and four subjects (33%) used injection drugs at least once during treatment (all four injectors used heroin). O f these, 1 used cocaine alone (non-injection), 3 used cocaine (non-injection) and heroin (injection), 2 used heroin alone (1 - non-injection and injection, 1 - injection) and 1 used methamphetamine alone (non-injection). Five of the nine subjects also used marijuana during treatment (with 3 also having used heroin, cocaine or methamphetamine). The mean number of days of drug use during treatment was 2, 3, 11 and 54 per individual for cocaine, heroin, methamphetamine and marijuana respectively. A s shown in Figure 2, the proportion o f patients responding to H C V therapy in those having completed or discontinued treatment was 8/12 (67%>). In total, 2/3 (67%) and 6/9 individuals (67%) infected with H C V genotype 1 and H C V genotypes 2/3 had an E T R . In all patients having completed or discontinued therapy for H C V infection (n=12), 57.8% o f medication doses were administered over a median of 14 (genotypes 2/3) or 28 (genotype 1) weeks. The on-treatment mean directly observed adherence to interferon was 99.1%, while the mean self-reported adherence to ribavirin was 91.1%. Adverse events were mild to moderate in severity and typical of treatment with pegylated interferon and ribavirin. The most commonly reported adverse events were fatigue (100%), nausea (92%), anorexia (83%>), headache (67%) and depression (67%). Only 2 patients required dose-reductions in R B V , while no patient required a dose-reduction o f P E G - I F N . 107 5.4 DISCUSSION Historically, the uptake of H C V treatment has been low among IDUs, despite this group being at highest risk for H C V (1). A number of studies have demonstrated that IDUs can be successfully treated for H C V infection (13-21). However, there are little data evaluating programs for successfully engaging these individuals in H C V care and the specific programmatic components that are important for success. One potential strategy for improving patient engagement in care would be increased reliance on peer-support as a tool, coupled with directly observed therapy for the delivery of the medications in those requiring treatment. Overall, we observed a high uptake o f H C V treatment among IDUs attending a weekly H C V peer support group. Among attendees, we were first able to identify a proportion of infected subjects that did not require treatment for H C V infection based on disease severity and develop a plan for continued follow-up, which is enhanced by their participation in the group. Only 29% were lost to follow-up. Individuals lost to follow-up tended to exhibit a lower weekly attendance and were less likely to attend >3 clinic visits when compared to subjects initiating treatment for H C V . This suggests that initial attendance provides a strong indication of future attendance and that individualized approaches need to be developed to better engage some individuals in care. However, for the vast majority of HCV-infected IDUs in our clinic, the group provides an important means of identifying individuals with a demonstrated interest in addressing their H C V infection. We observed a high uptake o f H C V treatment among attendees, with 51%> either receiving or about to receive therapy. This figure is impressive considering the numerous barriers associated with treatment in this population, speaking to the success of our model. Our preliminary results are quite encouraging, given that 67% of subjects receiving directly observed therapy with P E G - I F N and R B V achieved an E T R . This response to treatment is no doubt increased by the fact that there was a selection bias of individuals with H C V genotypes 2/3 (78%>), which is higher than the prevalence of these genotypes reported in IDUs in Vancouver (41%>) (23). This being said, our results are comparable to those reported in large, randomized controlled trials of P E G - I F N and R B V for the treatment o f H C V infection (8-10) and were achieved despite the fact that 56%> of subjects had used i l l ici t drugs in the 6 months preceding therapy and that 75% of patients used ill icit drugs at least once during their course of treatment. This is similar to results from a previous study at our centre among 40 current and former drug 108 users. Overall, 55% achieved a sustained virologic response (SVR) , despite the fact that many individuals continued to use il l ici t drugs during treatment (12). A s we move forward, it w i l l be important to further document S V R rates, as the ultimate measure o f treatment efficacy. This w i l l be particularly relevant as data now suggest that shorter durations o f H C V treatment (such as those received by a number of our subjects) may be efficacious in subjects infected with H C V genotypes 2/3 (24, 25). Wi th this in mind, there is confidence that a large majority w i l l go on to achieve S V R , especially given that the on-treatment adherence to pegylated-interferon and ribavirin was extremely high in this study (95-100%). It is also important to understand that 75% of subjects required early treatment discontinuation and only 58% received a full course of treatment according to published therapeutic guidelines. Discontinuations were often related to depression, and we need to develop specific strategies for addressing this question Given that three-quarters of new cases of H C V infection occur in IDUs, it is clear that any comprehensive approach to control this epidemic must include a systematic strategy to address this group. Our study demonstrates that relatively simple programs can be established to engage IDUs in care. A t our center, this is accomplished by incorporating an H C V peer-support group into our established multidisciplinary model addressing addiction and other medical conditions simultaneously and includes directly observed therapy for the delivery of medication. Although the specific components required for a successful approach w i l l vary in other centres, appropriate patient selection within a multi-disciplinary model for the delivery o f care to this inner city w i l l be required. Such programs w i l l be a valuable approach in the war against H C V infection in the risk group in which it is most prevalent. 109 Figure 5.1. Patient Disposition REFERRED TO H C V R X G R O U P (N=80) TREATMENT NOT MEDICALLY INDICATED ( N = 8 , 1 0 % ) COMPLETED/INITIATED TREATMENT PRIOR TO GROUP ( N = 8 , 1 0 % ) 5 DISCONTINUED DUE TO A E S (4 -DEPRESSION, 1 - A N E M I A ) RECEIVED/RECEIVING TREATMENT (N=21 , 2 6 % ) INITIATED TREATMENT WITH P E G - I F N + R B V (N=18) 1 NON-RESPONDER (GENOTYPE 1 INADEQUATE E V R 4 COMPLETED THE FULL TREATMENT DURATION LOST TO FOLLOW-UP (N=23, 2 9 % ) UNDER EVALUATION FOR H C V TREATMENT (N=20, 2 5 % ) RECEIVED CARE AT ANOTHER CENTRE (N=3) >J 2 DISCONTINUED D U E TO RELAPSE TREATMENT IS ONGOING IN 6 SUBJECTS 110 Table 5.1. Baseline characteristics among the 18 subjects in whom treatment for HCV infection was initiated. Characteristic N=18 Mean Age - years (SD) 42.8 (6.6) Male sex - n (%) 17 (94%) Body weight - kg Mean (SD) 80.3 (10.9) >75 kg-n(%) 12 (67%) Mean Estimated Duration of Infection - years (SD) 17.1 (6.6) Drug Abstinence < 6 months - n (%) 10 (56%) Median Time - months (IQR) 4(0-60) On Methadone Maintenance Therapy - n (%) 8 (44%) Median Methadone Dose - milligrams/day (IQR) 123 (75-143) Mean Beck Depression Index (SD) 9.8 (1-23) Pre-treatment with antidepressants - n (%) 14 (78%) HCV Genotype - n (%) 1 4 (22%) 2 3 (17%) 3 11 (61%) Median ALT - U/liter (IQR) 141 (85-256) Median AST - U/liter (IQR) 91 (61-139) HIV infection - n (%) 4 (22%) *SD, standard deviation; IQR, Interquartile range 111 Table 5.2. Treatment for hepatitis C virus (HCV) infection among the 18 current and former injection drug users initiating therapy at the Pender Community Health Centre in Vancouver, Canada. Patient Age in years/sex HIV Status HCV Genotype Drug Abstinence Prior to Treatment (months) Major Drug(s) Used Frequency at Time of Last Use Treatment for Drug Dependenc y Type of P E G - I F N + R B V (planned duration) Status Outcome 1 39/M Negative 3a 8 Heroin/Cocaine Daily No a2a (24 wks) Completed SVR 2 41/M Negative 2b 0 Heroin Daily Methadone a2a (24 wks) Ceased week 15 SVR 3 37/M Negative 3a 3 Heroin Monthly Methadone ola (24 wks) Completed SVR 4 36/M Negative la 7 Heroin/Cocaine Daily No a2a (48 wks) Ceased week 22 SVR 5 37/M Positive lutsf 0 Methamphetamine Daily Methadone a2a (48 wks) Ceased week 27 NR 6 46/M Negative lutsf 0 Marijuana Daily No a2a (48 wks) Completed ETR 7 46/M Negative 3a 5 Heroin/Crack Daily No a2a (24 wks) Ceased week 14 E T R 8 43/M Positive 3a 20 Heroin Weekly Methadone 0.2b (24 wks) Ceased week 4 NR 9 40/M Negative 3utsf 8 Cocaine Other day No a2b(24wks) Completed ETR 10 48/F Positive 3a 12 Heroin Daily Methadone o2b (24 wks) Ceased week 5 NR 11 42/M Negative 2b 60 Heroin Daily Methadone o2b (24 wks) Ceased week 5 ETR 12 48/M Negative lb 0 Cocaine/Crack Daily No a2a (48 wks) Ongoing week 22 -13 38/M Negative 3a 0 Heroin/Crack Other day No a2a (24 wks) Ceased week 3 NR 14 45/M Negative 3a 0 Cocaine Daily No a2a (24 wks) Ongoing week 12 -15 48/M Positive 3a 3 Cocaine Daily Methadone a2a (24 wks) Ongoing week 15 -16 52/M Negative 2utsf 0 Cocaine Monthly No u2a (24 wks) Ongoing week 14 -17 28/M Negative 3a 12 Heroin Daily Methadone a2a (24 wks) Ongoing week 16 -18 56/M Negative 3a 6 Heroin Daily No a2a (24 wks) Ongoing week 19 -*utsf, unable to subtype further, E T R , end of treatment response; S V R , sustained virological response. Figure 5.2. Virological response to treatment according to genotype in the 12 patients having completed therapy as measured by HCV RNA at the end of treatment; ETR. 113 5.5 REFERENCES 1. Shepard CW, Finelli L , Alter MJ . Global epidemiology of hepatitis C virus infection. Lancet Infect Dis 2005;5:558-567. 2. Grebely J, Conway B, Raffa J, Lai C, Krajden M , Tyndall M . Uptake of hepatitis C virus treatment among injection drug users in Vancouver, Canada [Abstract 578]. J Hepatol 2006;44:S214. 3. NCHECR. HIV/AIDS, viral hepatitis and sexually transmissible infections in Australia Annual Surveillance Report 2003. Sydney: National Centre in HIV Epidemiology and Clinical Research (NCHECR), The University of New South Wales; 2003. 4. Fleming C A , Craven DE, Thornton D, Tumilty S, Nunes D. Hepatitis C virus and human immunodeficiency virus coinfection in an urban population: low eligibility for interferon treatment. Clin Infect Dis 2003;36:97-100. 5. Fishbein D A , Lo Y , Reinus JF, Gourevitch M N , Klein RS. Factors associated with successful referral for clinical care of drug users with chronic hepatitis C who have or are at risk for HIV infection. J Acquir Immune Defic Syndr 2004;37:1367-1375. 6. Restrepo A , Johnson TC, Widjaja D, Yarmus L , Meyer K , Clain DJ, Bodenheimer HC, Jr., et al. The rate of treatment of chronic hepatitis C in patients co-infected with HIV in an urban medical centre. J Viral Hepat 2005;12:86-90. 7. Falck-Ytter Y , Kale H , Mullen K D , Sarbah SA, Sorescu L, McCullough A J . Surprisingly small effect of antiviral treatment in patients with hepatitis C. Ann Intern Med 2002;136:288-292. 8. Fried M W , Shiffman M L , Reddy K R , Smith C, Marinos G, Goncales FL, Jr., Haussinger D, et al. Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection. N Engl J Med 2002;347:975-982. 9. Hadziyannis SJ, Sette H, Jr., Morgan TR, Balan V , Diago M , Marcellin P, Ramadori G, et al. Peginterferon-alpha2a and ribavirin combination therapy in chronic hepatitis C: a randomized study of treatment duration and ribavirin dose. Ann Intern Med 2004;140:346-355. 10. Manns MP, McHutchison JG, Gordon SC, Rustgi V K , Shiffman M , Reindollar R, Goodman ZD, et al. Peginterferon alfa-2b plus ribavirin compared with interferon alfa-2b plus ribavirin for initial treatment of chronic hepatitis C: a randomised trial. Lancet 2001;358:958-965. 11. McHutchison JG, Gordon SC, Schiff ER, Shiffman M L , Lee W M , Rustgi V K , Goodman ZD, et al. Interferon alfa-2b alone or in combination with ribavirin as initial treatment for chronic hepatitis C. Hepatitis Interventional Therapy Group. N Engl J Med 1998;339:1485-1492. 12. Grebely J, Raffa J, Meagher C, Duncan F, Viljoen M , Khara M , Mead A, et al. Treatment of hepatitis C virus infection in previous and current injection drug users. In: In Programs and Abstracts of the 17th International Conference on the Reduction of Drug Related Harm; 2006; Vancouver, Canada.; 2006. 114 13. Sylvestre DL , Litwin A H , Clements BJ, Gourevitch M N . The impact of barriers to hepatitis C virus treatment in recovering heroin users maintained on methadone. J Subst Abuse Treat 2005;29:159-165. 14. Van Thiel D H , Anantharaju A , Creech S. Response to treatment of hepatitis C in individuals with a recent history of intravenous drug abuse. Am J Gastroenterol 2003;98:2281-2288. 15. Litwin A H , Soloway I, Gourevitch M N . Integrating services for injection drug users infected with hepatitis C virus with methadone maintenance treatment: challenges and opportunities. Clin Infect Dis 2005;40 Suppl 5:S339-345. 16. Taylor L E . Delivering care to injection drug users coinfected with HIV and hepatitis C virus. Clin Infect Dis 2005;40 Suppl 5:S355-361. 17. Backmund M , Meyer K, Von Zielonka M , Eichenlaub D. Treatment of hepatitis C infection in injection drug users. Hepatology 2001;34:188-193. 18. Neri S, Bruno C M , Abate G, Ierna D, Mauceri B , Cilio D, Bordonaro F, et al. Controlled clinical trial to assess the response of recent heroin abusers with chronic hepatitis C virus infection to treatment with interferon alpha-n2b. Clin Ther 2002;24:1627-1635. 19. Mauss S, Berger F, Goelz J, Jacob B, Schmutz G. A prospective controlled study of interferon-based therapy of chronic hepatitis C in patients on methadone maintenance. Hepatology 2004;40:120-124. 20. Schaefer M , Schmidt F, Folwaczny C, Lorenz R, Martin G, Schindlbeck N , Heldwein W, et al. Adherence and mental side effects during hepatitis C treatment with interferon alfa and ribavirin in psychiatric risk groups. Hepatology 2003;37:443-451. 21. Dalgard O. Follow-up studies of treatment for hepatitis C virus infection among injection drug users. Clin infect Dis 2005;40 Suppl 5:S336-338. 22. Matthews G, Kronborg IJ, Dore GJ. Treatment for hepatitis C virus infection among current injection drug users in Australia. Clin Infect Dis 2005;40 Suppl 5:S325-329. 23. Grebely J, Conway B, Raffa J, Lai C, Krajden M , Tyndall M . High prevalence of hepatitis C virus (HCV) genotype 3 infection among injection drug users in Vancouver, Canada [Abstract 35]. Can J Gastroenterol 2006;20:200. 24. Mangia A , Santoro R, Minerva N , Ricci G L , Carretta V , Persico M , Vinelli F, et al. Peginterferon alfa-2b and ribavirin for 12 vs. 24 weeks in H C V genotype 2 or 3. N Engl J Med 2005;352:2609-2617. 25. Dalgard O, Bjoro K , Helium K B , Myrvang B, Ritland S, Skaug K, Raknerud N , et al. Treatment with pegylated interferon and ribavarin in H C V infection with genotype 2 or 3 for 14 weeks: a pilot study. Hepatology 2004;40:1260-1265. 115 CHAPTER VI General Conclusions & Recommendations for Future Work Injection drug users (IDUs) represent the core o f the H C V epidemic. Although clearance of H C V wi l l occur in a minority of infected subjects, most w i l l develop chronic infection. Without antiviral therapy, chronic H C V infection wi l l lead to long-term liver-associated morbidity and mortality. However, it is not clear whether treatment can be effective among current and former IDUs, given a number of barriers to therapy. Understanding the natural history o f H C V infection among IDUs and how they respond to effective treatment in a controlled setting wi l l be absolutely essential in reducing the future global burden o f H C V disease, given that this group represents the majority o f infected individuals. This thesis focuses on understanding components of the natural history and treatment of H C V infection in IDUs. Specifically, it focuses on identifying factors associated with spontaneous clearance of H C V infection in this population and understanding whether spontaneous clearance o f H C V provides protection against re-infection. This thesis also evaluates novel models for improving uptake and response rates for treatment of H C V among current and former IDUs with chronic H C V infection. Taken together, these data add significantly to the body of knowledge of H C V infection in IDUs. 6.1 General Conclusions 6.1.1 Natural History of HCV in IDUs First, within a large community-based cohort o f i l l ici t drug users, we have demonstrated that Aboriginal ethnicity and female sex were associated with an enhanced likelihood of clearing H C V infection spontaneously, while H I V co-infection and ill icit drug use were associated with increased persistence of H C V infection. Our findings with respect to the impact o f Aboriginal ethnicity on clearance of H C V confirm preliminary data from other centres suggesting a higher rate of clearance in this group (1-3) and add to the body of knowledge demonstrating that ethnicity impacts clearance of H C V (4-6). Similarly, the finding that females demonstrated higher rates of clearance also confirm a number o f reports in the literature in I D U and non-IDU populations (7) (8-12). A number of potential mechanisms explaining the impact of gender and ethnicity on spontaneous H C V clearance have been proposed (9, 13-21). A n emerging common theme implicates a central role of host genetics. Specifically, it is postulated that certain 116 genetically encoded proteins are important in the innate and adaptive immune responses against H C V infection. Also consistent with previous findings, we demonstrated that H I V infection was associated with decreased clearance o f H C V infection. However, given that the order of H I V and H C V infections are often not known in IDUs, it is not certain whether H I V is impacting clearance or persistence of H C V . W e demonstrated that H C V infections generally arose several years before H I V infections did. Given that spontaneous clearance of H C V generally occurs within the first year of infection, this provides evidence to suggest that H I V is impacting the persistence of H C V rather than its initial clearance. H I V infection may decrease circulating HCV-specif ic C D 4 and C D 8 T cells that are generally present in higher levels in individuals with H C V clearance leading to either re-infection with H C V or the re-emergence of low-level viremia that may have been undetectable by conventional assays for a period o f time (22). We also demonstrated that i l l ici t drug use was associated with increased persistence of H C V . This may be related to an increased susceptibility towards re-infection with H C V . However, one study demonstrated that H C V re-infection after H C V clearance occurs less frequently than in individuals with primary infection (23). This suggests that H C V clearance may be protective with respect to H C V re-infection and that IDUs may actually be getting re-infected prior to clearance having had a chance to occur, making it appear as i f they are more susceptible to viral persistence. The observation that i l l ici t drug use had a marginal impact on clearance of H C V led to the hypothesis that previous H C V clearance is protective against H C V re-infection. W e investigated this by comparing the rate of H C V re-infection among individuals who had spontaneous H C V clearance with the rate of primary H C V infection among participants enrolled in the same cohort as we evaluated in the previous study. After adjusting for potential confounding variables, we observed that individuals with successful clearance of H C V were four times less susceptible to H C V re-infection when compared to individuals becoming infected for the first time. This represents the largest study of H C V re-infection to date and confirms previous findings demonstrating a lower rate of H C V re-infection among individuals with documented virologic clearance (23). In addition, individuals with H I V / H C V co-infection were two times more likely to demonstrate recurrence of H C V viremia than those with H C V alone. Whether this is a result 117 of an increased risk o f becoming re-infected with H C V or the recrudescence o f low-level H C V viremia after the acquisition of H I V infection remains to be determined. Overall, the absence o f chronic re-infection over a long duration o f follow-up (5.2 years) in this large study indicates that some IDUs may be protected from H C V re-infection either through reduced risk behaviours for its acquisition, host factors responsible for the resolution of primary viremia or a partial protective immunity leading to enhanced clearance after re-infection. In chimpanzees re-infected with H C V , there is rapid control o f viral replication, short-lived viremia and universal spontaneous resolution of secondary infection (24). Additionally, in humans and chimpanzees, re-infection generally leads to an attenuated course of infection, with the level and duration of viremia being markedly reduced (25-28). If a similar protection against H C V re-infection can be demonstrated among IDUs having cleared H C V successfully following treatment, it could have significant implications for the expansion of programs for the therapy of H C V infected IDUs. 6.1.2 Treatment of HCV in IDUs To date, no study has investigated directly observed therapy (DOT) for the treatment of H C V infection in IDUs. Wi th this in mind, we sought to evaluate the efficacy of treatment o f H C V infection in current and former IDUs enrolled in a prospective, multidisciplinary, directly observed therapy (DOT) program. The overall response rates observed in this study parallels results from large, randomized controlled trials using peginterferon and ribavirin, which have generally excluded subjects with ongoing ill icit drug use behaviours. In this study, this response was achieved despite the fact that many individuals continued to use il l ici t drugs during treatment. Although some guidelines exclude subjects with i l l ici t drug use in the six months preceding therapy for H C V , similar response rates were achieved in subjects with <6 or >6 months of drug abstinence. Illicit drug use of any kind during treatment for H C V infection was not associated with reduced response rates, unless it exceeded a specific threshold. These results confirm data from other groups among current and former IDUs for the treatment of H C V (29-38). This suggests that the decision to treat H C V in current and former IDUs must be individualized based on medical indications and contra-indications to treatment, the willingness of the patient to initiate therapy and our ability to deliver treatment in a setting to maximize the likelihood of success. In particular, the decision to treat should not be based solely on a pre-118 defined period of drug abstinence. Taken together, these data demonstrate that IDUs can be safely and successfully treated for H C V infection within a multidisciplinary program integrating H C V , addiction and primary care. However, it is important to note that the responses achieved in this study may exceed those observed among a less selected population of HCV-infected IDUs. A s we move forward, it w i l l be important to develop novel strategies for engaging IDUs in care for H C V and otherwise creating the winning conditions to maximize response rates. Although uptake of H C V treatment has been low among IDUs, one strategy for improving engagement in H C V care may include the development and implementation of support groups for subjects considering treatment. We evaluated the uptake and response to therapy among current and former IDUs infected with H C V attending a weekly support group developed to enhance long-term engagement in medical care for H C V . Among current and former IDUs referred to this group, the overall uptake o f H C V treatment was high, with one half of the patients either receiving or about to receive therapy for H C V . Although almost a quarter of subjects were subsequently lost to follow-up and these individuals could be identified by a lower weekly attendance and lower likelihood to attend >3 clinic visits. Similar to the data presented in chapter IV, we observed high response rates to therapy, which may have been associated with the higher proportion o f subjects with genotype 2 and 3 enrolled in this study. However, individuals enrolled in this study may have also been a higher risk group of patients, given that over half of subjects had used ill icit drugs in the six months preceding therapy and almost three-quarters engaged in il l ici t drug use at least once during treatment for H C V . Regardless, these data demonstrate that a novel model integrating an H C V support group, multidisciplinary care and D O T can lead to high rates of uptake and response to H C V treatment among current and former IDUs. 6.2 Limitations There are a number o f additional limitations that should be addressed from the study evaluating H C V re-infection in IDUs. First, the demographic and behavioural characteristics differ among those with H C V clearance and those previously uninfected with H C V . Individuals with clearance are often older and may have reduced risk behaviour following a diagnosis of H C V infection. However, although older, they were using i l l ici t drugs more often than subjects previously uninfected with H C V suggesting that the risk o f H C V acquisition actually remained 119 high, making any demonstration of reduced rates of infection even more significant. This being said, longitudinal reporting of injection drug use behaviour was not available and it was not possible to delineate the specific nature of risks associated with drug use (including injection equipment sharing) that would more accurately define H C V transmission risks. However, the extent of the protection we observed makes us confident that there was a protective effect, although measuring the magnitude of this effect would require more reliable risk behaviour data and more systematic H C V R N A testing. Lastly, given that the H C V R N A testing is heterogeneous and broad, it is possible that cases of transient H C V re-infection were missed among those with clearance who resolved a secondary case of re-infection. Irrespective of these limitations, the absence of chronic re-infection over a long duration of follow-up among those with spontaneous clearance of H C V indicates that some IDUs are protected against re-infection with H C V . There are also limitations associated with our work evaluating the treatment of H C V infection among IDUs. First, it is likely that there is a significant selection bias associated with the studies of treatment and participation in support groups. It is likely that a selection bias may have resulted in the treatment of more stable patients with a higher likelihood of success. Similarly, individuals with a demonstrated interest in receiving treatment for H C V infection may have been more likely referred to the H C V support group, resulting in a referral bias. Thus, these results may not be generalizable to the overall population of HCV-infected IDUs. It would be useful to have a comparison group of those not having received treatment to understand the factors associated with H C V treatment uptake in this setting. Both observational studies are also limited by their small sample sizes, making it difficult to identify statistically significant factors associated with treatment outcome. However, these results provide important data supporting the proof-of-concept of DOT for H C V treatment, providing the foundation for future randomized controlled trials with the appropriate comparison groups to overcome the limitations of our observational work. 6.3 Overall Significance of Results and Future Directions The research presented in this thesis has significant implications for the field of H C V infection. Little is known about the natural history of H C V in IDUs, including factors associated with H C V clearance and the risk of H C V re-infection following successful clearance. The findings that 120 Aboriginal ethnicity is associated with increased H C V clearance and that HIV infection is associated with increased H C V persistence are important. These data provide the basis for the design and development of the appropriate studies to prospectively evaluate the impact of Aboriginal ethnicity and HIV on H C V clearance and persistence, incorporating the investigation of the appropriate genetic and immunologic parameters that may explain the mechanisms behind these observations. Further trans-disciplinary studies evaluating the epidemiology, genetics and immunology of H C V clearance in Aboriginals and those infected with HIV are needed. This may uncover important aspects of HCV-specific immunity that could aid in the development of novel vaccines and treatments for H C V infection. The finding that previous clearance of H C V is protective against H C V re-infection also has important implications for the field. Although data in chimpanzees suggest that protective immunity can be achieved among individuals with H C V clearance, there have been little human data in this regard. Our study provides convincing evidence that some IDUs may be protected from H C V re-infection after successful clearance. Also, it is apparent that HIV infection may lead to increased persistence of HCV. For the field of H C V , further investigation into this observation may provide insight into how the immune system controls H C V infection. Also, i f a similar protection is observed among individuals clearing H C V infection as a result of treatment for H C V , it would provide a stronger rationale for the development of treatment programs for HCV-infected IDUs. However, given the limitations of our retrospective study, we are not able to determine whether this protection occurs through reduced risk behaviours for acquisition, host factors responsible for the resolution of primary viremia, a partial protective immunity leading to enhanced clearance after re-infection or a combination of the above factors. These issues will be addressed within a prospective study planned in our centre. Future prospective, interdisciplinary studies integrating epidemiology and basic science are needed to evaluate the natural history of H C V re-infection in IDUs (including the impact of HIV infection on persistence of HCV) and should include a detailed assessment of risk behaviours and more frequent and systematic H C V R N A testing. Also, as a greater number of IDUs are treated for H C V infection, it will be important to document risk behaviours following successful clearance and evaluate whether a similar protection against re-infection is observed in the setting of treatment-induced clearance. This type of information is necessary to better understand the 121 immunopathogenesis and natural history of H C V in IDUs, thereby helping to define public health H C V control measures and treatment recommendations. Lastly, we have demonstrated that the treatment of H C V is both safe and effective when incorporated into a multidisciplinary model including directly observed (DOT) therapy. The virologic response rates we have documented are similar to those observed in non-IDU populations.. This provides further impetus to support the expansion of H C V treatment within models which incorporate the treatment of addiction and H C V infection. Directly observed therapy and peer-group support represent two important strategies that may enhance the engagement of IDUs into treatment for H C V and improve adherence during therapy. However, there are still gaps in understanding the specific programmatic components that are required for the successful engagement of IDUs in care for H C V and improving outcomes while receiving therapy. Among active users, there needs to be further research into novel methods of using drug dependence treatment for engaging IDUs in treatment for H C V , including investigations into the impact o f various drug dependency treatments (i.e. methadone, buprenorphine) on response to treatment. Young IDUs constitute the majority o f new infections and research is urgently needed to understand their acceptance and response to treatment. Given that acute H C V infection can be cured in 85-95% of subjects, the identification, prevention and treatment of young IDUs could have enormous public health impact. Lastly, further randomized, controlled trials evaluating various strategies for the treatment o f H C V in IDUs are urgently needed. This w i l l require the development of international collaborative projects to ensure that recruitment of these studies is possible and that the results are more widely generalizable. Given that IDUs are at the core o f the current and future H C V epidemic, future research investigating strategies for addressing H C V infection in IDUs wi l l have important implications for the reduction of the global burden of H C V . 6.4 Closing Remarks Health care practitioners have often avoided caring for IDUs, citing concerns that certain approaches or programs are actually contraindicated on medical grounds. This is often a convenient means of rationalizing a lack of comfort in dealing with such a population, not to mention a perception of addiction as a personal choice rather than a disease. It has been my 122 observation that i f the right structure is put in place, many IDUs wi l l seek to engage in care in a productive manner. In the work I have presented in this thesis, I have demonstrated that, at least for H C V infection, the response to complex treatment may be as good as reported in a population o f rigorously selected clinical trial participants. A society is evaluated based on how it treats its less fortunate. Western society in particular w i l l be evaluated on how it deals with its inner city populations, including many IDUs. A s part o f these interventions, a systematic approach to H C V infection w i l l be required, as many o f the inhabitants of these inner cities are already living with this chronic disease. Insomuch as I have generated rigorous data to help inform the development o f such an approach, I have not only contributed to the advancement o f science, but also to the advancement of society as a whole. For having been afforded this opportunity, I am eternally grateful. 123 6.5 References 1. Minuk G Y , Zhang M , Wong SG, Uhanova J, Bernstein C N , Martin B, Dawood MR, et al. Viral hepatitis in a Canadian First Nations community. Can J Gastroenterol 2003;17:593-596. 2. Minuk G Y , Uhanova J. Viral hepatitis in the Canadian Inuit and First Nations populations. Can J Gastroenterol 2003;17:707-712. 3. Scott JD, McMahon BJ, Bruden D, Sullivan D, Homan C, Christensen C, Gretch DR. High rate of spontaneous negativity for hepatitis C virus R N A after establishment of chronic infection in Alaska Natives. Clin Infect Dis 2006;42:945-952. 4. Piasecki B A , Lewis JD, Reddy K R , Bellamy SL, Porter SB, Weinrieb R M , Stieritz DD, et al. Influence of alcohol use, race, and viral coinfections on spontaneous H C V clearance in a US veteran population. Hepatology 2004;40:892-899. 5. Thomas DL, Astemborski J, Rai R M , Anania FA, Schaeffer M , Galai N , Nolt K , et al. The natural history of hepatitis C virus infection: host, viral, and environmental factors. J A M A 2000;284:450-456. 6. Villano SA, Vlahov D, Nelson K E , Cohn S, Thomas DL. Persistence of viremia and the importance of long-term follow-up after acute hepatitis C infection. Hepatology 1999;29:908-914. 7. Micallef J M , Kaldor JM, Dore GJ. Spontaneous viral clearance following acute hepatitis C infection: a systematic review of longitudinal studies. J Viral Hepat 2006;13:34-41. 8. Kenny-Walsh E. Clinical outcomes after hepatitis C infection from contaminated anti-D immune globulin. Irish Hepatology Research Group. N Engl J Med 1999;340:1228-1233. 9. Alric L , Fort M , Izopet J, Vinel JP, Bureau C, Sandre K , Charlet JP, et al. Study of host- and virus-related factors associated with spontaneous hepatitis C virus clearance. Tissue Antigens 2000;56:154-158. 10. Inoue G, Horiike N , Michitaka K , Onji M . Hepatitis C virus clearance is prominent in women in an endemic area. J Gastroenterol Hepatol 2000; 15:1054-1058. 11. Yamakawa Y , Sata M , Suzuki H , Noguchi S, Tanikawa K . Higher elimination rate of hepatitis C virus among women. J Viral Hepat 1996;3:317-321. 12. Bakr I, Rekacewicz C, E l Hosseiny M , Ismail S, E l Daly M , El-Kafrawy S, Esmat G, et al. Higher clearance of H C V infection in females compared to males. Gut 2006. 13. Hayashi J, Kishihara Y , Ueno K , Yamaji K , Kawakami Y , Furusyo N , Sawayama Y , et al. Age-related response to interferon alfa treatment in women vs men with chronic hepatitis C virus infection. Arch Intern Med 1998;158:177-181. 14. Thio C L , Goedert JJ, Mosbruger T, Vlahov D, Strathdee SA, O'Brien SJ, Astemborski J, et al. An analysis of tumor necrosis factor alpha gene polymorphisms and haplotypes with natural clearance of hepatitis C virus infection. Genes Immun 2004;5:294-300. 15. Thio C L , Gao X , Goedert JJ, Vlahov D, Nelson K E , Hilgartner M W , O'Brien SJ, et al. HLA-Cw*04 and hepatitis C virus persistence. J Virol 2002;76:4792-4797. 124 16. Thio C L , Thomas DL, Goedert JJ, Vlahov D, Nelson K E , Hilgartner M W , O'Brien SJ, et al. Racial differences in H L A class II associations with hepatitis C virus outcomes. J Infect Dis 2001;184:16-21. 17. Barrett S, Ryan E, Crowe J. Association of the HLA-DRB1*01 allele with spontaneous viral clearance in an Irish cohort infected with hepatitis C virus via contaminated anti-D immunoglobulin. J Hepatol 1999;30:979-983. 18. Thursz M , Yallop R, Goldin R, Trepo C, Thomas HC. Influence of M H C class II genotype on outcome of infection with hepatitis C virus. The HENCORE group. Hepatitis C European Network for Cooperative Research. Lancet 1999;354:2119-2124. 19. Oleksyk T K , Thio CL, Truelove A L , Goedert JJ, Donfield S M , Kirk GD, Thomas DL, et al. Single nucleotide polymorphisms and haplotypes in the IL10 region associated with H C V clearance. Genes Immun 2005;6:347-357. 20. Khatkar S A K , Kaita K and Rempel JD. The impact of H C V core and NS3 proteins on Aboriginal and Caucasian P B M C IL-10 production in response to IFN-a. In: 18th Annual Spring meeting of Canadian Society for Immunology; 2005; Whistler, Canada.; 2005. 21. Khakoo SI, Thio CL, Martin MP, Brooks CR, Gao X , Astemborski J, Cheng J, et al. H L A and N K cell inhibitory receptor genes in resolving hepatitis C virus infection. Science 2004;305:872-874. 22. K i m A , Schulze Zur Wiesch J, Allen T, Gandhi R, Davis B, Jones A , Robbins G, et al. Virus-specific T-cell Responses and Loss of Spontaneous Control of H C V in HIV+ individuals. 13th Conference on Retroviruses and Opportunistic Infections 2006:Abstract_84. 23. Mehta SH, Cox A, Hoover DR, Wang X H , Mao Q, Ray S, Strathdee SA, et al. Protection against persistence of hepatitis C. Lancet 2002;359:1478-1483. 24. Major M E , Dahari H , Mihalik K , Puig M , Rice C M , Neumann A U , Feinstone SM. Hepatitis C virus kinetics and host responses associated with disease and outcome of infection in chimpanzees. Hepatology 2004;39:1709-1720. 25. Nascimbeni M , Mizukoshi E, Bosmann M , Major M E , Mihalik K , Rice C M , Feinstone SM, et al. Kinetics of CD4+ and CD8+ memory T-cell responses during hepatitis C virus rechallenge of previously recovered chimpanzees. J Virol 2003;77:4781-4793. 26. Lanford RE, Guerra B, Chavez D, Bigger C, Brasky K M , Wang X H , Ray SC, et al. Cross-genotype immunity to hepatitis C virus. J Virol 2004;78:1575-1581. 27. Shoukry N H , Grakoui A , Houghton M , Chien D Y , Ghrayeb J, Reimann K A , Walker C M . Memory CD8+ T cells are required for protection from persistent hepatitis C virus infection. J Exp Med 2003;197:1645-1655. 28. Gerlach JT, Diepolder H M , Zachoval R, Gruener N H , Jung M C , Ulsenheimer A, Schraut WW, et al. Acute hepatitis C: high rate of both spontaneous and treatment-induced viral clearance. Gastroenterology 2003;125:80-88. 125 29. Sylvestre D L , Litwin A H , Clements BJ, Gourevitch M N . The impact of barriers to hepatitis C virus treatment in recovering heroin users maintained on methadone. J Subst Abuse Treat 2005;29:159-165. 30. Van Thiel D H , Anantharaju A , Creech S. Response to treatment of hepatitis C in individuals with a recent history of intravenous drug abuse. A m J Gastroenterol 2003;98:2281-2288. 31. Litwin A H , Soloway I, Gourevitch M N . Integrating services for injection drug users infected with hepatitis C virus with methadone maintenance treatment: challenges and opportunities. Clin Infect Dis 2005;40 Suppl 5:S339-345. 32. Taylor L E . Delivering care to injection drug users coinfected with HIV and hepatitis C virus. Clin Infect Dis 2005;40 Suppl 5:S355-361. 33. Backmund M , Meyer K, Von Zielonka M , Eichenlaub D. Treatment of hepatitis C infection in injection drug users. Hepatology 2001;34:188-193. 34. Neri S, Bruno C M , Abate G, Ierna D, Mauceri B, Cilio D, Bordonaro F, et al. Controlled clinical trial to assess the response of recent heroin abusers with chronic hepatitis C virus infection to treatment with interferon alpha-n2b. Clin Ther 2002;24:1627-1635. 35. Mauss S, Berger F, Goelz J, Jacob B, Schmutz G. A prospective controlled study of interferon-based therapy of chronic hepatitis C in patients on methadone maintenance. Hepatology 2004;40:120-124. 36. Schaefer M , Schmidt F, Folwaczny C, Lorenz R, Martin G, Schindlbeck N , Heldwein W, et al. Adherence and mental side effects during hepatitis C treatment with interferon alfa and ribavirin in psychiatric risk groups. Hepatology 2003;37:443-451. 37. Dalgard O. Follow-up studies of treatment for hepatitis C virus infection among injection drug users. Clin Infect Dis 2005;40 Suppl 5:S336-338. 38. Matthews G, Kronborg IJ, Dore GJ. Treatment for hepatitis C virus infection among current injection drug users in Australia. Clin Infect Dis 2005;40 Suppl 5:S325-329. 126 APPENDIX 127 U B C / P r o v i d e n c e Hea l th Ca re OFFICE OF RESEARCH SERVICES 1 1 t h F loor Hornby S i te - S P H c /o 1081 Bur ra rd S t , V a n c o u v e r , BC V 6 Z 1Y6 P h o n e : (604) 8 0 6 - 8 5 6 7 F a x : (604) 8 0 6 - 8 5 6 8 Certificate of Research Ethics Board Approval Amendment Princ ipal Inves t iga to r : Depar tmen t : Reference N u m b e r : Dr. Mark Tynda l l Infect ious D iseases P 0 2 - 0 2 6 3 Ins t i tu t ion(s) Where Resea rch Wi l l be Carr ied Ou t : C o m m u n i t y Based Organ i za t i ons in the V a n c o u v e r Downtown Easts ide , S ing le R o o m Occupancy Un i ts , V C H A C o m m u n i t y Heal th C l in ics C o - i n v e s t i g a t o r s : T. Ker r , C . Lai Sponso r i ng A g e n c i e s : V a n c o u v e r Coas ta l Hea l th Author i ty Project T i t l e : C o m m u n i t y Heal th a n d Safe ty Eva lua t ion ( C H A S E ) Project Date of Ini t ia l A p p r o v a l T e r m of Init ial Approva l A m e n d m e n t A p p r o v e d : D e c e m b e r 9 , 2 0 0 2 1 Year JUN 1 5 2006 D o c u m e n t s Inc luded in th is A p p r o v a l : Consen t F o r m V e r s i o n 1.2 (dated May 2 0 0 6 ) ; Su rvey The C h a i r / A s s o c i a t e C h a i r of the U B C / P H C REB has rev iewed the a m e n d m e n t ( s ) for the a b o v e - n a m e d pro ject and the a c c o m p a n y i n g documenta t i on was found to be accep tab le on eth ica l g rounds for research invo lv ing h u m a n sub jec ts . The REB approval period for this amendment expires on the one-year anniversary date of the REB approval for the entire study. CERTIFICATION In r e s p e c t o f c l in ica l t r i a l s : 1. The membership of this Research Ethics Board complies with the membership requirements for Research Ethics Boards as defined in part C Division 5 of the Food and Drug Regulations. 2. This Research Ethics Board carries out its functions in a manner consistent with Good Clinical Practices and 3. This Research Ethics Board has reviewed and approved the clinical trial protocol and informed consent form for the trial, which is to be conducted by the qualified investigator named above at the specified clinical trial site. This approval and the views of this Research Ethics Board have been documented in writing. y * *1 P R O V I D E N C E H E A L T H CARE R e s e a r c h Institute A p p r o v a l of the Cl in ica l Research Ethics Board by one of: Dr. I, Fedoroff , Cha i r Dr . A . M c L e o d , Assoc ia te Cha i r Da te : JUN 1 5 2006 132 

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