A panel of 16 type-specific synthetic peptides corresponding to variable antigenic regions within the hepatitis C virus (HCV) core, nonstruc-tural4 (NS4), and NS5 proteins was synthesised. The peptide panel was used to develop an enzyme immunoassay (EIA) for the detection of antibodies directed to HCV type 1 (genotypes 1/1a and 11/ 1 b), type 2 (genotypes 1W2a and IV/2b), and type 3 (genotype V/3). The peptides corresponded to residues 68-81 of the HCV core (types 1,2, and 3), residues 1692-1705 and 1710-1728 of HCV NS4 (types l a , 1 b, 2a, 2b, and 31, and residues 2303-231 9 of HCV NS5 (types 1 a, 1 b, 2a, and 2b). The 16-peptide panel was evaluated us- ing human sera from 46 carriers of HCV, which were genotyped in parallel by the polymerase chain reaction (PCR) using primers specific for types I, II, Ill, IV, and V of HCV core. Of the 46 carriers, 14 (30%) were infected by HCV genotype I, 7 (15%) by genotype II, 16 (35%) by HCV genotype IV, and 6 (13%) by HCV of genotype V.
Two carriers had double infections of types I and II, and the HCV strain of one carrier could not be genotyped. Using the serotyping system, 40 (89%) out of the 45 genotyped carriers were found to contain type-specific antibodies corresponding to the genotypes identified by PCR. In 5 of the 23 carriers infected by genotypes I and/or II, antibodies specific for HCV type 1 could not be detected, whereas all 16 carriers infected by genotype IV were serologically typed as type 2. Out of the six carriers infected by HCV of genotype V, all were found to have antibodies of serotype 3, but in most cases together with antibodies to NS5 type 1, indicating sequence homologies between types 1 and 3 of this NS5 region. In the one patient serum where the HCV strain could not be genotyped, a mixture of types 1, 2, and 3 antibodies were found. In conclusion, a serotyping system with a sensitivity and specificity of 89% was developed. It is confirmed that at least three distinct serotypes of antibodies to HCV exist. The major advantage of using four different anti-
genic regions is that we often obtain high absorbance values which are easily interpreted, or multiple reactions which confirm each other.