THE CYTOTOXIC T-LYMPHOCYTE RESPONSE TO MULTIPLE HEPATITIS-B VIRUS POLYMERASE EPITOPES DURING AND AFTER ACUTE VIRAL-HEPATITIS

Cytotoxic T lymphocytes (CTL) are thought to contribute to viral clear ance and liver cell injury during hepatitis B virus (HBV) infection. U sing a strategy involving the in vitro stimulation of peripheral blood mononuclear cells (PBMC) with HBV-derived synthetic peptides containi ng HLA-A2.1, -A31, and -Aw68 binding motifs, we have previously descri bed CTL responses to several epitopes within the HBV nucleocapsid and envelope antigens in patients with acute hepatitis. In this study we d efine six HLA-A2-restricted CTL epitopes located in the highly conserv ed reverse transcriptase and RNase H domains of the viral polymerase p rotein, and we show that the CTL response to polymerase is polyclonal, multispecific, and mediated by CD8(+) T cells in patients with acute viral hepatitis, but that it is not detectable in patients with chroni c HBV infection or uninfected healthy blood donors. Importantly, the p eptide-activated CTL recognize target cells that express endogenously synthesized polymerase protein, suggesting that these peptides represe nt naturally processed viral epitopes. DNA sequence analysis of the vi ruses in patients who did not respond to peptide stimulation indicated that CTL nonresponsiveness was not due to infection by viral variants that differed in sequences from the synthetic peptides. CTL specific for one of the epitopes were unable to recognize several naturally occ urring viral variants, except at high peptide concentration, underlini ng the HBV subtype specificity of this response. Furthermore, CTL resp onses against polymerase, core, and envelope epitopes were detectable for more than a year after complete clinical recovery and seroconversi on, reflecting either the persistence of trace amounts of virus or the presence of long lived memory CTL in the absence of viral antigen. Fi nally, we demonstrated that wild type viral DNA and RNA can persist in definitely, in trace quantities, in the serum and PBMC after complete clinical and serological recovery, despite a concomitant, vigorous, an d sustained polyclonal CTL response. Since viral persistence is not du e to escape from CTL recognition under these conditions, the data sugg est that HBV may retreat into immunologically privileged sites from wh ich it can seed the circulation and reach CTL-inaccessible tissues, th ereby maintaining the CTL response in apparently cured individuals and , perhaps, prolonging the liver disease in patients with chronic hepat itis.