Immunogenicity of variable regions of hepatitis C virus proteins: selection and modification of peptide epitopes to assess hepatitis C virus genotypes by ELISA

The immunogenicity of variable regions of hepatitis C virus (HCV) proteins was studied by ELISA by using 543 synthetic peptides from 120 variable regi ons and 90 sera from HCV-infected patients. Some regions from certain genot ypes were less immunogenic, or even non-immunogenic, compared with their eq uivalents in other genotypes, However, the mean recognition of all peptides from genotypes 1a, 1b and 3 by sera infected with genotypes la, Ib and 3, respectively, showed no significant differences, suggesting a similar overa ll immunogenicity of variable regions from these genotypes, Proteins NS4a, NS4b and NS5a were found to be the most immunogenic, Recognition of individ ual peptides by the sera of infected patients showed that the humoral respo nse against HCV is patient-dependent. The work shows that 15-mer peptides m ay encompass several B-cell epitopes, These epitopes may lie in slightly di fferent positions in different genotypes, Thirty-one percent of the 543 pep tides were recognized by some of the 35 healthy donors. This may be a refle ction of the large number of antigens to which they had been exposed, but i t may also reflect a strategy of HCV to respond to immune pressure. After s election and modification, a set of 40 peptides was used to assess genotype s 1a, 1b, 1, 2 and 3 in the sera of HCV-infected patients, with sensitiviti es of 34.1, 48.5, 68.8, 58.3 and 48.9% and specificities of 100, 99.1, 97.1 , 99.5 and 99%, respectively. The overall sensitivity and specificity for t he assessment of genotypes 1, 2 and 3 were 64 and 98%, respectively.