SIGNIFICANCE OF SPECIFIC ANTIBODY-ASSAY FOR GENOTYPING OF HEPATITIS-C VIRUS

Group I and II hepatitis C virus genotypes were determined by a newly developed serological genotyping assay. This assay detected antibodies against group-specific recombinant proteins in the putative NS4 protein region (amino acid no. 1676-1760) by an enzyme-linked immunosorbent assay. This region of the hepatitis C virus peptide has many group-specific amino acids; fewer than 50% of these amino acids are identical between groups I and II. Genotypes determined by the serological genotyping assay were compared with those determined by a method in which the polymerase chain reaction was used in 91 chronic hepatitis patients. The group specific polymerase chain reaction was performed within the genome region corresponding to the putative NS5 protein, where the group II hepatitis C virus genome is 57 nucleotides longer than that of group I. Among 91 chronic hepatitis C patients who had positive results in the second-generation hepatitis C virus antibody (core and NS3 region) assay, hepatitis C virus RNA was detected in 80 patients by polymerase chain reaction in the 5' untranslated region and in 78 patients by this group-specific polymerase chain reaction. As a result, in 76 of 91 patients (84%) genotypes determined by the serological genotyping assay showed complete agreement with those determined by the group-specific polymerase chain reaction, and none of the patients revealed a group opposite to that of hepatitis C virus genotype. The detection rate of the serological genotyping assay (89 of 91; 98%) was even higher than that of the polymerase chain reaction assay (78 of 91; 86%). Thus, serological genotyping assay is specific and sensitive for the determination of hepatitis C virus genotypes, and this enzyme-linked immunosorbent assay may be useful for epidemiological studies of hepatitis C virus genotypes.