MAPPING OF SEROTYPE-SPECIFIC, IMMUNODOMINANT EPITOPES IN THE NS-4 REGION OF HEPATITIS-C VIRUS (HCV) - USE OF TYPE-SPECIFIC PEPTIDES TO SEROLOGICALLY DIFFERENTIATE INFECTIONS WITH HCV TYPE-1, TYPE-2, AND TYPE-3

The effect of sequence variability between different types of hepatiti s C virus (HCV) on the antigenicity of the NS-4 protein was investigat ed by epitope mapping and by enzyme-linked immunosorbent assay with br anched oligopeptides. Epitope mapping of the region between amino acid residues 1679 and 1768 in the HCV polyprotein revealed two major anti genic regions (1691 to 1708 and 1710 to 1728) that were recognized by antibody elicited upon natural infection of HCV. The antigenic regions were highly variable between variants of HCV, with only 50 to 60% ami no acid sequence similarity between types 1, 2, and 3. Although limite d serological cross-reactivity between HCV types was detected between peptides, particularly in the first antigenic region of NS-4, type-spe cific reactivity formed the principal component of the natural humoral immune response to NS-4. Type-specific antibody to particular HCV typ es was detected in 89% of the samples from anti-HCV-positive blood don ors and correlated almost exactly with genotypic analysis of HCV seque nces amplified from the samples by polymerase chain reaction. Whereas almost all blood donors appeared to be infected with a single virus ty pe (97%), a higher proportion of samples (47%) from hemophiliacs infec ted from transfusion of non-heat-inactivated clotting factor contained antibody to two or even all three HCV types, providing evidence that long-term exposure may lead to multiple infection with different varia nts of HCV.