CD8 + T-Cell Differentiation in Chronic HCV Infection

HCV has the tendency to persist in the majority of infected patients despite the presence of virus-specific CD8+ T-cell responses. The HCV-specific CD8+ T-cell pool consists of heterogenous subsets that can be elegantly distinguished by CD127 expression. Indeed, HCV-specific CD8+ T cells with high levels of CD127 expression are characterized by features consistent with memory differentiation, while HCV-specific CD8+ T cells with low levels of CD127 expression display an exhausted phenotype characterized by the coexpression of PD-1 and other inhibitory receptors. In this article, the current knowledge about the phenotypes and differentiation profiles of HCV-specific CD8+ T cells is summarized. Clearly, the differentiation of HCV-specific CD8+ T cells in chronic HCV infection results from complex virus–host interactions, and both viral and immunological factors shape the HCV-specific CD8+ T-cell pool.