Immunoreactivity to putative B-cell epitopes of hepatitis G virus polyprotein in viremic and nonviremic subjects.

The hepatitis G virus (HGV) polyprotein was scanned by computer-aided prediction of antigenicity to search for B-cell epitopes. Four polypeptide sequences, V37D (amino acids [aa] 1685 to 1721), V36S (aa 2102 to 2137), P37R (aa 2156 to 2192), and C40P (aa 2280 to 2319), were identified and synthesized for use in immunoassays. Antibodies to these peptides were searched for in a panel of 239 serum samples, which were also tested for anti-E2 antibodies and HGV RNA. Furthermore, the course of HGV markers was studied prospectively in four patients who had been transfused with HGV RNA-positive blood. There was a negative association between immunoreactivity to V37D and P37R and presence of HGV RNA (2 of 53 and 1 of 53, respectively; P < 0.05); none of the subjects with dual antibody positivity was HGV RNA positive. Anti-V37D and anti-P37R antibodies compared favorably with anti-E2 antibodies as markers of recovery from HGV infection. These results might be useful for the development of new, more sensitive diagnostic assays.