Hepatitis B virus (HBV) infection is strongly associated with hepatocellular carcinoma. The sequence of HBeAg in sera of hepatitis patients and the sequence of the entire core antigen in liver-derived HBVs of hepatoma patients reveal elevated mutation frequencies in the highly evolutionarily conserved regions. There may be a relationship between the regions of antigenic determinants of HBeAg and the regions of elevated mutation frequencies of the liver-derived and naturally occurring HBVs. The antigenic epitopes of HBeAg were studied to explain how HBeAg variants accomplish immunoevasion via escape mutation along the antigenic determinants of HBeAg recognized by T-cell and B-cell. Attempts were made to map antigenic determinants of HBeAg using a monoclonal antibody (MAb 8425). Seven potential epitopes of HBeAg were analysed by hydrophilicity and synthesized as peptides. HBeAg recombinant protein, SV, was tested for specific antigenicity with monoclonal antibody and sera from patients with hepatoma and used as a target protein for binding with monoclonal antibody. The blocking activity of each peptide in the binding of monoclonal antibody to the target protein was measured by Western blot immunodetection and ELISA. No blocking effect, by any of the peptides, was identified by either assay. We conclude that the recombinant HBeAg protein expressed in this study was able to compete with MAb for the binding to the HBeAg but the epitope mapping of HBeAg specific for MAb was not successful.
