Immunological characterization of two major secreted forms of recombinant hepatitis B virus e antigens

Plasmids containing PCR-amplified hepatitis B virus e antigen (HBeAg) genes (HBeAg-MV and HBeAg-SV) were constructed and expressed in E. coli strain D H5 alpha. The induced intracellular glutathione S-transferase (GST) fusion proteins of HBeAg-MV and HBeAg-SV were recovered and purified from bacteria l lysates by affinity chromatography with glutathione-sepharose beads. The HBeAg-MV protein contained an additional 19 amino acids at its amino termin us. These two proteins were specifically cleaved from GST by the protease f actor Xa and recognized by a monoclonal antibody against HBeAg. HBeAg-MV an d HBeAg-SV were found to be the two major components of the post-modified H BcAg during viral infection. The antigenic specificities of the fusion and purified HBeAgs (factor Xa-digested) were confirmed by the Abbott HBe enzym e immunoassay (EIA) detection system. Sera from patients with confirmed hep atocellular carcinoma (HCC) specifically reacted only with HBeAg moiety of fusion proteins. HCC sera bound more strongly to the HBeAg-SV protein than to the HBeAg-MV one. This indicates that HBeAg-SV is either more antigenic than -MV or is the major target protein for the elicitation of antibody pro duction after HBV infection. Thus, the two recombinant HBeAgs expressed and obtained in this study are appropriate immunological agents for the diagno stic detection of hepatitis B virus infection in humans. (C) 1999 Elsevier Science B.V. All rights reserved.