T‐cell immunity and hepatitis C virus reinfection after cure of chronic hepatitis C with an interferon‐free antiviral regimen in a chimpanzee

Memory CD8 + T cells generated by spontaneous resolution of hepatitis C virus (HCV) infection rapidly control secondary infections and reduce the risk of virus persistence. Here, CD8 + T‐cell immunity and response to reinfection were assessed in a chimpanzee cured of an earlier chronic infection with an interferon (IFN)‐free antiviral regimen. CD8 + T cells expanded from liver immediately before and 2 years after cure of chronic infection with two direct‐acting antivirals (DAAs) targeted epitopes in the E2, nonstructural (NS)5a, and NS5b proteins. A second infection to assess CD8 + T‐cell responsiveness resulted in rapid suppression of HCV replication by week 2, but viremia rebounded 3 weeks later and the infection persisted. The E2, NS5a, and NS5b proteins remained dominant CD8 + T‐cell targets after reinfection. Resurgent HCV replication was temporally associated with mutational escape of NS5a and NS5b class I epitopes that had also mutated during the first chronic infection. Two epitopes in E2 remained intact throughout both persistent infections. Intrahepatic CD8 + T cells targeting intact and escape‐prone epitopes differed in expression of phenotypic markers of functional exhaustion 2 years after successful DAA therapy and in the capacity to expand in liver upon reinfection. Conclusions : The intrahepatic HCV‐specific CD8 + T‐cell repertoire established during chronic infection was narrowly focused, but very stable, after cure with DAA. Existing intrahepatic CD8 + T cells targeting dominant epitopes of the challenge virus failed to prevent persistence. Vaccination after DAA cure may be necessary to broaden T‐cell responses and reduce the risk of a second persistent infection. (H epatology 2014;60:1531–1540)