The effect of the HLA B27 allele on the immune response to acute HCV in HIV infected patients

In mono-infected individuals, the HLA-B27 allele is strongly associated with spontaneous clearance of HCV in association with a strong CD8+ response targeted against a single epitope within the HCV RNA-dependent RNA polymerase (NS5B). We studied variation across the whole HCV genome and T cell responses over time in a rare cohort of HLA-B27+ patients with acute HCV and HIV co-infection, the majority of whom progressed to chronicity. We used next generation sequencing to detect changes within and outwith the immuno-dominant HLA-B27 restricted HCV-specific CD8+ T cell epitope NS5B2841-2849 (ARMILMTHF) during evolving progression of early HCV infection. Within the Acute HCV UK cohort, 10 patients carried the HLA B27 allele. Of these, 3/8 patients (37.5%) with HIV infection and 2/2 (100%) without HIV spontaneously cleared HCV (p=0.44). Sequential samples from nine HLA-B27+ patients (2 with monoinfection and 7 with HIV co-infection) were available for analysis (four spontaneous clearers and five evolving progressors). Mutations identified using NGS were assessed using a replicon genotype 1a system to evaluate viral fitness. Multiple mutations within the HLA-B27 restricted NS5B2841-2849 epitope were associated with progression to chroncity whereas patients who cleared the HCV infection spontaneously had no or only one mutation at this site (p=0.03). A triple NS5B2841-2849 mutant observed during progression to chronicity was associated with restored replication when compared to wild-type virus while single or double mutants were significantly associated with impaired replication (p=0.0495). T cell responses measured in these patients using ELISpot and flow cytometry. HLA-B27+ patients had significantly higher IFN-γ responses than patients who were HLA-B27- (p=0.0014). Those who progressed to chronicity had lower IFN-γ responses than those who cleared HCV (p=0.0011). Mono-infected patients had higher IFN-γ responses compared to co-infected patients (p=0.0015). HIV co-infection is associated with a lower likelihood of spontaneous clearance of HCV in HLA B27+ patients and this is associated with impaired T cell function in this group.