• antigenic determinant;
  • HBcAg;
  • HBV carrier;
  • lymphocyte

Abstract: Residues 72–146 within hepatitis B core Ag (HBcAg) represent T-cell recognition site in HB-virus-infected man. This study was undertaken to define critical residues involved in the immunogenicity of dominant T-cell determinants of HBcAg. For this purpose, p120–131 and its analog (p120–131 [A] containing alanine substitutions at residues 122 and 125, which were identified as epitopic residues in mice, were synthesized. These peptides and recombinant HBcAg were analyzed for their ability to stimulate peripheral blood mononuclear cells (PBMC) from 25 patients with chronic HBV infection and three patients with acute hepatitis B. PBMC from 18 out of 28 patients showed significantly increased IFN-γ production and proliferative response in the presence of recombinant HBcAg. Eight patients responded to the two peptides, while 12 patients did not. Four patients responded only to p120–131, and four displayed a response only to p120–131 [A]. The responses to the two peptides were similar among HBeAg-positive and anti-HBe-positive patients, and did not depend on disease activity, except for HBeAg-positive asymptomatic carriers in whom there was no response to any additive. These results indicate that immune responses to p120–131 and its analog were similar in our patient groups. The dominant epitopic residues in this region of HBcAg may differ between man and mouse.