Molecular analysis of hepatitis B virus DNA in serum and peripheral blood mononuclear cells from hepatitis B surface antigen-negative cases

We have analyzed the molecular bases of the persistence of hepatitis B viru s (HBV) DNA in serum and peripheral blood mononuclear cells (PBMC) in the a bsence of detectable hepatitis B surface antigen (HBsAg) in hemodialysis pa tients and dialysis-unit staff members who had suffered acute hepatitis B t hat resolved previously. HBV DNA was found in both compartments by polymera se chain reaction (PCR) using primers of the pre-S/S region. Viral DNA was transcriptionally active in PBMC, because the covalently closed circular (c cc) HBV DNA, the template for the viral RNA transcription, was detected in 47% of the samples. Furthermore, all PBMC had HBV RNA. HBsAg-negative cases had statistically lower levels of HBV DNA in serum and PBMC than a control group of chronic HBsAg carriers. We have also studied the presence of immu ne complexes and the existence of mutations in the pre-S/S gene to explain the lack of detection of HBsAg in these cases. No serum HBsAg/hepatitis B s urface antigen antibody (anti-HBs) immune complexes or mutations in the "a" determinant of the S gene were found. However, we have observed that all H BsAg-negative cases were infected by a mixture of the wild-type virus and a deletion mutant in the pre-S1 region, This deletion (amino acids 58-118) a ffects the S gene promoter, and previous in vitro studies have shown that i t produces a reduction of the HBsAg synthesis. In conclusion, this work sho ws that the lack of detection of HBsAg in the presence of low viral levels of replication may be caused by the existence of viral genomes harboring de letions in the pre-S1 region that affect the S promoter.