Characterization and mapping of a B-cell immunogenic domain in hepatitis C virus E2 glycoprotein using a yeast peptide library.

To identify conserved humoral antigenic determinants within the hepatitis C virus (HCV) envelope protein E2, we expressed a peptide library containing random short fragments of the HCV envelope in yeast. Clones were identified using a monospecific rabbit antibody to a region downstream of the E2 hypervariable region. The clones define the limits of two original antigenic domains: a major one (aa 493-576) and a minor one (aa 535-606). The major antigenic domain maps in a region that displays a high degree of homology within a (HCV) subtype (92-97.6% identity). Yeast-encoded determinants were characterized by Western blot analysis, N-glycosidase F digestion, and using a panel of synthetic peptides. The data suggest that the major antigenic domain contains at least two determinants, one of them mimicked by an 18-mer peptide (aa 514-531). ELISA and competitive inhibition assays demonstrated that: (1) the determinants appear subtype 1a-specific, (2) seroprevalence of antibody to the determinants is rather low (20.6%), and (3) donors show a heterologous response to the different determinants. Antibody response to the E2 determinants was studied in HCV-infected chimpanzees and post-transfusion-associated NANB hepatitis cases. The antibody response was found during chronic infection and may not be effective for virus clearance.