Mutational escape from cellular immunity in viral hepatitis: variations on a theme

Abstract

Approx. 320 million individuals worldwide are chronically infected with hepatitis viruses, contributing to viral hepatitis being one of the 10 leading causes of death. Cellular adaptive immunity, namely CD4+ and CD8+ T cells, plays an important role in viral clearance and control. Two main mechanisms, however, may lead to failure of the virus-specific T-cell response: T-cell exhaustion and mutational viral escape. Viral escape has been studied in detail in hepatitis C virus (HCV) infection, where it is thought to affect approx. 50% of virus-specific CD8+ T-cell responses in persistent infection, to influence natural infection outcome and to contribute to failure of preventive vaccination strategies. In hepatitis B virus (HBV) as well as HBV/hepatitis D virus (HDV) co-infection, the impact of viral escape has been studied in detail only recently.