Nucleotide sequence of the precore/core gene and X gene of hepatitis B virus DNA in asymptomatic hepatitis B virus carriers who are negative for serum hepatitis B core antibody

A hepatitis B virus (HBV) carrier who is positive for hepatitis B surface (HBs) antigen but negative for hepatitis B core (HBc) antibody despite persistent HBV infection, is designated has having hepatitis B virus 2 (HBV2). HBV2 is reported to be induced by mild-grade hepatitis. Patients with HBV2 have been reported in Taiwan and Senegal. In the present study, we determined the nucleotide (nt) sequence of the precore/core gene coding region and X gene region of the HBV DNA sequence in 7 subjects who were positive for HBs antigen and negative for HBc antibody. HBV DNA was detected by nested polymerase chain reaction (PCR). Nested PCR was carried out to amplify the precore/core and X open reading frames (ORFs) of HBV DNA. The second PCR products were sequenced, followed by investigation of nt homology. There were no deletions nor insertions in the nt sequence of the precore/core and X ORFs in the HBV DNA of these 7 patients, and mutations were found only sporadically in the 7 patients. Also, there were no common amino acid substitutions in the examined regions of the amino acid sequence of HBV in the 7 patients, and we could not find a common mutation in the examined regions of HBV DNA that could potentially contribute to the development of negativity for HBc antibody. Thus, it is suggested that negativity for HBc antibody in patients with HBV2 is due to an immune response abnormality in the host.