Concurrent HBsAg and anti-HBs induced by a preS deletion mutant in a chronic hepatitis B patient.

This study analyzed the origins of concurrent hepatitis B surface antigen (HBsAg) and HBsAg antibodies (anti-HBs) in a patient with chronic hepatitis B virus (HBV) infection. The levels of serological markers of HBV infection were determined by enzyme-linked immunosorbent assay (ELISA). The preS/S gene was analyzed by gene amplification and sequencing. The tests revealed that HBsAg and anti-HBs coexisted in this patient with mixed infections of the full-length preS/S virus strain and preS1 183 bp deletion mutant, and both the mutant and the anti-HBs were no longer present after one year, which means that the mutant strain was cleared by the detected antibodies. Thus, it is speculated that anti-HBs antibodies targeted specifically to the preS1 deletion mutant strain instead of the strain with the full-length large S protein were produced. This mechanism is quite different from other immunopathogenic mechanisms for concurrent HBsAg and anti-HBs.