Surface gene mutations of hepatitis B virus among high-risk patients with occult hepatitis B virus infection.

Surface gene mutants of hepatitis B virus (HBV) have been reported in a variety of patient groups. Because of limited data regarding these mutations in patients with occult HBV infections; we aimed to determine these mutations among high-risk patients with occult HBV infection. The presence of HBV-DNA was determined in patients with isolated anti-HBc by real-time polymerase chain reaction (PCR). Then, surface gene region was amplified by nested PCR and mutations were analyzed after sequencing. The mutations that resulted in nonfunctional hepatitis B surface antigen (HBsAg) were insertion of single nucleotide in 2 cases, which causes frameshift and single-nucleotide replacement, and premature stop codons at Leu15 and Gly10 in the other 2 cases. Amino acid substitution at amino acid position 207(S207N) was found in the other isolates. Our study suggested that "a" region mutations did not play a major role in HBsAg detection, and other genetic and nongenetic factors may be responsible for failure to detect HBsAg by routine laboratory tests.