Identification of immunodominant T cell epitopes of the hepatitis B virus nucleocapsid antigen.

Abstract

Several lines of experimental evidence suggest that inclusion of core sequences in the hepatitis B vaccine may represent a feasible strategy to increase the efficacy of the vaccination. In order to identify immunodominant core epitopes, peripheral blood T cells purified from 23 patients with acute hepatitis B and different HLA haplotypes were tested with a panel of 18 short synthetic peptides (15 to 20 amino acids [AA]) covering the entire core region. All patients except one showed a strong T cell proliferative response to a single immunodominant 20 amino acid sequence located within the aminoterminal half of the core molecule. Two additional important sequences were also identified at the aminoterminal end and within the carboxyterminal half of the core molecule. These sequences were able to induce significant levels of T cell proliferation in 69 and 73% of the patients studied, respectively. T cell response to these epitopes was HLA class II restricted. The observations that (a) polyclonal T cell lines produced by PBMC stimulation with native HBcAg were specifically reactive with the relevant peptides and that (b) polyclonal T cell lines produced with synthetic peptides could be restimulated with native HBcAg, provide evidence that AA sequences contained within the synthetic peptides represent real products of the intracellular processing of the native core molecule. In conclusion, the identification of immunodominant T cell epitopes within the core molecule provides the molecular basis for the design of alternative and hopefully more immunogenic vaccines. (J. Clin. Invest. 1991.

High rate of mutations in the hepatitis B core gene during the immune clearance phase of chronic hepatitis B virus infection

“…Four of these codons are located in known trated in five codons which comprise only 2.7% of the entire immune recognition sites: codons 5, 60, and 130 in T-helper core gene. Four of these codons were located in known epiepitopes (1-20, 50-69, and 117-131, codon 130 also overlaps topes suggesting that these mutations may have been sewith a B-cell epitope); 20 codon 130 in B-cell epitope (130-138) 21 ; and codon 27 in HLA-A2 restricted CTL epitope (18-27). 22 Twelve codons had amino acid substitutions in two or more patients, 15 (18%) of the substitutions in these codons were unique (Table 3).…”

Predominant T-helper 1 cytokine profile of hepatitis B virus nucleocapsid-specific T cells in acute self-limited hepatitis B

“…and 1 1 10 6 . 4 Allogeneic irradiated antigen presenting cells were incubated for Selected antigen-specific T-cell lines were cloned by limiting dilu-2 hours at 37ЊC in medium alone or with different concentrations of tion at 1 cell per well in round-bottom 96-well plates, in RPMI me-synthetic peptides, washed extensively and then cocultured (1 1 10 5 dium containing 10% fetal calf serum, 3% human serum, and IL-2 (20 cells per well) for 3 days with responder T cells. 3 H-Thymidine was U/mL), in the presence of allogeneic-irradiated (6,000 rads) PBMC as added to the cultures 6 hours before harvesting.…”

“…Ten selected for cloning by limiting dilution. A total of 71 HBV of the 15 T-cell lines derived from the acute phase of infection nucleocapsid-specific CD4 / T-cell clones were obtained: 10 (67%) secreted significant amounts of IFN-g, but neither ILproliferated to HBV nucleocapsid antigens, but no peptide 4 nor IL-5 (Th1 profile), whereas the remaining 5 lines (33%) specificity could be defined; 1 was specific for HBc [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] (Table 1). …”

Dynamics of hepatitis B virus clearance in chimpanzees

“…Although it is generally agreed that viral clearance and disease pathogenesis during HBV infection are mediated by the immune response (2)(3)(4)(5)(6), the extent to which cytopathic and noncytopathic CD8ϩ T cell antiviral functions contribute to these events is a matter of some debate (7)(8)(9)(10)(11). On the one hand, it has been amply demonstrated that termination of acute hepadnavirus infections in the woodchuck (7,12) and chimpanzee (9)(10)(11) systems is associated with the destruction of infected cells and hepatocellular regeneration (7)(8)(9)(10)(12)(13)(14)(15).…”