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Elucidation of antigenic epitopes on the rubella virus E1 glycoprotein Chaye, Helena H.

Abstract

Rubella virus (RV), a positive-stranded RNA virus, is the only member of the genus Rubivirus within the Togaviridae family. The virus consists of a host derived lipid bilayer membrane, membrane glycoprotein spikes, and the C protein which together with viral RNA forms the icosahedral nucleocapsid. Although clinical rubella is a relatively mild disease, RV remains an important human pathogen because of its teratogenic effects in utero which can result in new born infants with congenital rubella syndrome (CRS). Complications such as polyarticular arthralgia and arthritis following vaccination or infection are common and rare cases of progressive panencephalitis have been reported. To obtain a better understanding of the immunopathology of RV infection, the degree of antigenicity of the structural proteins in humans were examined for both cellular and humoral immune responses. It was found that of the structural proteins, El glycoprotein was the dominant antigen recognized by the study population sampled from normal individuals with no history of rubella associated conditions. It was also found that the CRS patients had immune responses distinct from that of the normal population. In CRS patients E2 was the dominant antigen to which both cellular and humoral immune responses were elicited. The implications of these observation with respect to proposed mechanisms of persistent infection are discussed. Twenty three synthetic peptides spanning the entire El sequence were screened with human peripheral blood lymphocytes and the corresponding sera to examine the distribution of antigenic domains. El glycoprotein was also the target of viral neutralizing (VN) and hemagglutinin (HA) epitope mapping studies. Deletion mutants of El were constructed from El cDNAs and expressed in in vitro, in COS cells and in E.coli. The mutants were screened with monoclonal antibodies with VN and HA inhibiting activities. The mutants containing the functional epitopes were further studied by using synthetic peptides. HA epitope was mapped to amino acid residues E1214 to E12„ while two VN epitopes mapped to amino acid residues E1214 to E12, and E1219 to E1232. The potential use of the defined epitopes in the development of subunit vaccine is discussed.

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