UBC Theses and Dissertations
Neutralizing antibodies and the biological response to interferon-beta therapy Lam, Sin Man
Interferon-beta (IFN-beta) was the first disease modifying drug to be approved for the treatment of multiple sclerosis (MS). IFN-beta reduces relapse rates, relapse severity as well as slows the progression of disease burden. However, neutralizing antibodies (NAbs) occur in a proportion of patients receiving IFN-beta treatment. NAbs bind to IFN-beta, reduce drug bioavailability and high levels of NAbs reduce drug efficiency. Our first objective was to develop and validate a sensitive and rapid method to measure NAbs. Existing methods to measure NAbs include the cytopathic effect assay (CPE) method and the myxovirus protein A (MxA) assay. However, these assays are time consuming and may be arduous to perform. We describe the optimization of a luciferase reporter gene assay to measure NAbs. To validate the assay, we assayed sera from IFN-beta treated MS patients with the optimized luciferase method and compared the results to those obtained with the reference CPE method. NAb status measured by the luciferase and the CPE method did not yield a significant difference. NAb titres obtained from the two methods correlated very well. The luciferase assay is reliable, appropriately sensitive and requires less time than the currently available NAb methods. In addition to measuring NAbs, the biological activity of IFN-beta can be measured by monitoring IFN-inducible biomarkers, specifically MxA mRNA. Bioavailability measurements become especially valuable in patients with low to moderate NAb titres, “the grey zone”, and have been identified as a possible alternative for NAb measurements. Nonetheless, there is still controversy about how long should one wait after an IFN injection to draw blood for MxA mRNA measurements. Our objective was to identify the optimal time for blood draws to measure MxA mRNA. MxA mRNA was the most robust at 4-12 hours after IFN-beta injection and peaked at 8h post IFN injection. NAbs were evidently associated with an attenuation of IFN-beta bioactivity. In conclusion, we characterized a technique to assess NAbs associated with IFN-beta therapy and a method to assess IFN-beta biological activity in treated patients. Altogether, this will help measure the effects of IFN-beta treatment and assist clinicians in tailoring therapy to the individual patient.
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