Direct ex vivo analysis of hepatitis B virus-specific CD8(+) T cells associated with the control of infection

Background & Aims: Cytotoxic T cells have been suggested to be responsible for lysis of hepatitis B virus (HBV)-infected hepatocytes and control of vi rus infection. The frequency, kinetics, phenotype, and capacity for clonal expansion of circulating HBV-specific CD8 cells were analyzed directly in p atients with acute HBV infection to clarify their pathogenetic role. Method s: Three HLA-A2 peptide tetramers able to visualize HBV core, envelope, and polymerase epitope-specific cytotoxic T lymphocytes were synthesized and u sed for flow cytometric analysis of antigen-specific populations. Results: Tetramer-positive cells specific for the core 18-27 epitope were found at a higher frequency than those specific for polymerase 575-583 and envelope 3 35-343 epitopes in most patients with acute HBV. The number of HBV-specific CD8 cells was highest during the clinically acute stage of infection and d ecreased after recovery. These cells expressed an activated phenotype and h ad an impaired capacity to expand in vitro and to display cytolytic activit y in response to peptide stimulation. Recovery of these functions was obser ved when the frequency of specific CD8 cells decreased, coincident with a p rogressive decrease in their expression of activation markers. Conclusions: This study provides the first ex vivo evidence that the highest frequency of circulating HBV-specific CD8 cells coincides with the clinically acute p hase of hepatitis B, These cells exhibit an activated phenotype with limite d further proliferative capacity that is restored during recovery.