Differences in the source sequence of two HCV genotype 1b outbreaks within immunodominant CD8 epitopes are associated with differential outcome

Aims: Distinct HLA-class I alleles have a differential impact on the outcome of HCV infection. In the Irish Anti-D cohort HLA-B27 was associated with spontaneous control and HLA-B8 with viral persistence. Although the protective effect of HLA-B27 was confirmed in other cohorts, discrepant results have been obtained for HLA-B8. The aim of this study is to determine the role of sequence differences in the source virus for the differential outcome associated with these alleles.

Methods: Women from the East-German Anti-D outbreak were recruited 30 years after infection and the immunodominant B8-epitope (NS3-HSKKKCDEL) and B27-epitope (NS5B-ARMILMTHF) were sequenced. The impact of sequence differences on T cell recognition was determined.

Results: 220 samples have been HLA-typed (146 chronics and 74 resolvers). In contrast to the Irish cohort, no impact of HLA-B8 and -B27 on disease outcome is observed in the East-German cohort (resolvers vs. chronics B8: 17.6% vs. 19.8%; B27: 9.4% vs.11.6%). Interestingly, the source sequence in the immunodominant epitopes differs between both outbreaks. The B8-epitope in the Irish source harbors a substitution (K1397R; Ray JEM 2005) that is stable in B8(+) but reverts in 50% of B8(-). The East-German source carries the prototype that subsequently escapes in 50% of B8(+). In turn, the Irish source carries prototype in the B27-epitope, however, the East-German source harbors one substitution (I2844V) that is stable in B27(+) patients and that reverts in 32.7% of B27(-) patients. Of note, additional mutations in the epitope region only develop in B27(+). Although substantial cross-recognition of prototype-specific T cells is observed, reactive T cells are preferentially expanded upon stimulation with prototype.

Conclusion: Differences in the source sequence in immunodominant CD8 epitopes potentially have an impact on the ability of distinct HLA-alleles to contribute to control of HCV infection.