CD8+ T lymphocyte responses are induced during acute hepatitis C virus infection but are not sustained.

Cellular immune responses are likely to play a key role in determining the clinical outcome in acute infection with hepatitis C virus (HCV), but the dynamics of such responses and their relationship to viral clearance are poorly understood. In a previous study we have shown highly activated, multispecific cytotoxic T lymphocyte responses arising early and persisting in an individual who subsequently cleared the virus. In this study the HCV-specific CD8+ lymphocytes response has been similarly analyzed, using peptide-HLA class I tetramers, in a further nine individuals with documented acute HCV infection, six of whom failed to clear the virus. Significant populations of virus-specific CD8+ lymphocytes were detected at the peak of acute hepatic illness (maximally 3.5% of CD8+ lymphocytes). Frequencies were commonly lower than those seen previously and were generally not sustained. Early HCV-specific CD8+ lymphocytes showed an activated phenotype in all patients (CD38+ and HLA class II+), but this activation was short-lived. Failure to sustain sufficient numbers of activated virus-specific CD8+ lymphocytes may contribute to persistence of HCV.