CD4 and hepatitis C virus infection: Thus attractive hypotheses for the loss of viral control in acute hepatitis C could either be exhaustion of HCV specific T cells or a failure to establish stable memory CD4+ T cells during the phase of viral control which would explain why these cells do not expand when viremia returns and which is supported by the observation that in all three cases with evolving chronic hepatitis C CD4+ T cell function was lost before viral recrudescence.