A hybrid cell line producing monoclonal antibodies recognizing an epitope encoded by the pre-(S)2 region of hepatitis B virus (HBV) genome was obtained by fusion of mouse myeloma cells with lymphocytes from mice immunized with HBV. The monoclonal antibody Mo-Fl24 secreted from the hybrid line reacted with the pre-S(2) epitope expressed on the surface of both viral and recombinant HBsAg particles-pre-S(2) and S gene product-localised on 34 kD glycoprotein of the viral envelope. The pre-S(2) epitope was sensitive to digestion with V8 protease from Staphylucoccus uureus. The enzyme abolished reactivity with Mo-F124 and polymerized human serum albumin (pHSA) binding activity of recombinant particles. Mo-F 124 antibody was used to develop highly sensitive radioimmunoassays for determination of pre-S(2) epitope and anti-pre-S(2) antibody in sera of hepatitis B patients.
Detection of a pre-S(2) epitope by the monoclonal antibody-based assay in the early phase of acute HBV infection correlated well with the presence of markers of active viral replication (HBeAg, HBV DNA). The appearance of anti-pre-S(2) antibody, usually in the third month after onset of symptoms, was followed by elimination of circulating HBsAg and seroconversion to anti-HBs in all tested cases of uncomplicated acute hepatitis followed by recovery. Anti-pre-S(2) response wa5 not observed in patients with chronic hepatitis B or acute HBV infection progressing to chronic disease. The observed correlation of anti-pre-S(2) response with recovery suggests that the pre-S(2) epitope may represent one of the epitopes inducing antibodies that neutralize the hepatitis B virus.