Cross-genotype-reactivity of the immunodominant HCV CD8 T-cell epitope NS3-1073

The HCV-specific HLA-A2-restricted NS31073 epitope is one of the most frequently recognized epitopes in hepatitis C. NS31073-specific T-cell responses are associated with clearance of acute HCV-infection. Therefore this epitope is an interesting candidate for a HCV-peptide vaccine. However, heterogeneity between genotypes and mutations in the epitope has to be considered as an obstacle.We here identified 34 naturally occurring NS31073-variants, as compared with the wild type genotype-1 variants (CVNGVCWTV/CINGVCWTV) by sequencing sera of 251 Greek and German patients and searching for published HCV-genomes. The frequency of variants among genotype-1 patients was 10%. Importantly, HLA-A2 binding was reduced only in 3 genotype 1 mutants while all non-genotype 1 variants showed strong HLA-A2-binding. By screening 28 variants in ELISPOT assays from T cell lines we could demonstrate that HCV-NS31073-wild-type-specific T-cells displayed cross-genotype-reactivity, in particular against genotypes 4–6 variants. However, single aa changes within the TCR-binding domain completely abolished recognition even in case of conservative aa exchanges within genotype-1. NS31073-specific T-cell lines from recovered, chronically infected, and HCV-negative individuals showed no major difference in the pattern of cross-recognition although the proliferation of NS31073-specific T-cells differed significantly between the groups. Importantly, the recognition pattern against the 28 variants was also identical directly ex vivo in a patient with acute HCV infection and a healthy volunteer vaccinated with the peptide vaccine IC41 containing the NS31073-wild-type peptide.Thus, partial cross-genotype recognition of HCV NS31073-specific CD8 T cells is possible; however, even single aa exchanges can significantly limit the potential efficacy of vaccines containing the NS31073-wild-type peptide.