Occurrence of pre-S1 antigen in viremic and nonviremic carriers of hepatitis B surface antigen.

The proteins of viral envelope, encoded by the pre-S1 region of HBV-DNA, were measured quantitatively with enzyme immunoassay using monoclonal antibodies directed to pre-S1 epitope and correlated with the expression of pre-S2 region encoded epitope and other HBV markers. In acute HBV infection, both pre-S encoded proteins were detected in sera along with markers of viral replication and disappeared shortly before complete virus clearance while high HBsAg titers were still present. Pre-S1 antigen was present in most (95.5%) symptomatic and asymptomatic chronic HBsAg carriers. There was no correlation between the presence of pre-S1 and HBeAg or HBV-DNA in serum: 73% of sera with pre-S1 determinants were anti-HBe positive, and only 25.4% were positive for HBV-DNA. Most pre-S1 activity in sera of viremic carriers was detected in fractions of sucrose gradient containing subviral 22-nm particles, and much less in those containing infectious virions. In asymptomatic, nonviremic HBsAg carriers, pre-S1 was located only on subviral 22-nm forms. Pre-S1 positive particles had no accessible pre-S2 epitope, which is recognized specifically by monoclonal anti-pre-S2 (F124) antibody. These results show that the synthesis of the large protein of HBV envelope may occur also in the absence of active viral replication, and in these cases pre-S1 encoded sequences are on subviral particles of HBsAg. Therefore, pre-S1 is not a serologic marker of infectious virus. Disappearance of pre-S1 epitopes on HBsAg occurs only before complete clearance of the virus, and this may have potential prognostic relevance.