| Research Abstract |
The prevalence of anti-E2 antibody in patients chronically infected with hepatitis C virus (HCV) is reportedly high irrespective of viral genotype, and this cross-reactive antibody if thought to react with a conformational epitope. To investigate the characteristics of this anti-E2 antibody, we measured the immunoreactivity of sera from HCV-1b-infected patients against various modified forms of E2 glycoprotein derived from HCV-H (genotype 1a), using an immunofluorescence technique. Twelve patients of 18 (67%) were positive for anti-E2 antibody, and 10 of these 12 patients required a minimal amino acid region including amino acids (aa) 406 to 644 for strong reactivity, suggesting that the major anti-E2 antibody has a conformational epitope in this region. Subsequent analysis using mutant E2 glycoproteins designed to lose N-glycosylation potential at varying sites revealed seven important N-glycosylation sites in this region. In particular, four of them (aa423, aa430, aa448, and aa576) are indispensable for an antibody response.
Following investigation of the immunogenicity of HCV DNA vaccine was performed in a mouse model. Plasmid carrying the minimal immunogenic region determined above was used as DNA immunogen. Each mouse was injected of 100 ug plasmid DNA with phosphate buffer solution, and their blood was taken at several times with some intervals. Seroconversion of the mice could be detected in almost all the mice, indicating the super-immunogenicity of the DNA vaccine. This may be a candidate of HCV vaccine that is not yet established now.
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