Immunochemical structure of the hepatitis B surface antigen vaccine--II. Analysis of antibody responses in human sera against the envelope proteins.

Antibody responses to the three envelope (env) proteins of hepatitis B viral particles (HB-VP): the S-encoded P25 polypeptide; the pre-S(2)- and S-encoded GP33/GP36 polypeptide; and the large entire env gene (pre-S + S) product, P39/GP42, were investigated using a Western immunoblotting assay (WIBA). HB-VP proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and transferred to nitrocellulose by electroblotting were used as antigenic probes to determine the polypeptide specificity of these antibodies present in immune individuals. Antisera from human subjects either after a natural HBV infection or after active immunization with the hepatitis B vaccine licensed in France were selected on the basis of a positive serological RIA test for antibodies against hepatitis B surface antigen (HBsAg). In all studied cases, the lack of reactivity of the anti-HBs/P25 antibodies in blots from reduced SDS gels confirms that the S-related-determinants have a conformation sensitive to denaturing agents. In contrast, the anti-pre-S(2)/GP33-GP36 antibodies and the anti-pre-S(1)/P39-GP42 antibodies can be easily detected in WIBA, providing these antibodies recognize the disulfide-bond independent pre-S determinants on the denatured env proteins. However, antisera raised in guinea-pigs against individual HBsAg polypeptides contain antibodies reacting with denatured S-proteins, suggesting that the sequential S-determinants are lost during HBV morphogenesis. Antibody responses in HBV convalescing patients or vaccinated healthy donors are shown to be characterized by: an early transient polypeptide specific-antibody response to pre-S(2)-sequences (detected in WIBA); a persistent antibody response to conformation-dependent S-determinants (detected in RIA). This implies that effective long-term protection against HBV infection requires antibodies directed to native env proteins.