Hepatitis C virus (HCV) can persist in the liver, lymphoid cells, and serum of individuals with apparently complete spontaneous or therapy-induced resolution of hepatitis C and can replicate in vivo and in vitro in human T cells. The current study was aimed at assessing the infectivity of HCV persisting at very low levels using the previously established HCV infection system in human T cells. Naive lymphoid cells were exposed to plasma and/or supernatants from cultured peripheral blood mononuclear cells from nine individuals with apparent sustained virological response after completion of antiviral therapy. Exposed cells were analyzed for HCV RNA-positive and HCV RNA-negative strands and, in selected cases, for HCV nonstructural protein 5a (NS5a), the appearance of HCV variants, and the release of virions by immunoelectron microscopy (IEM). The results showed that 11 of the 12 established cultures became HCV RNA-positive strand-reactive, whereas 4 also expressed the virus replicative strand. NS5a protein was detected in the de novo infected cells, and clonal sequencing revealed HCV variants not found in inocula. IEM demonstrated enveloped HCV particles in plasma used as inocula and in culture supernatant from T cells exposed to that plasma. Overall, HCV carried in three of the nine individuals studied elicited productive infection in vitro.
Conclusion: HCV persisting at very low levels long after therapy-induced resolution of chronic hepatitis C can remain infectious. The retained biological competence of the virus might have implications with respect to the mechanisms of its persistence and the epidemiology of HCV infection.