A novel hepatitis B virus mutant coexisting with wild type virus in a carrier with negative HBsAg yet positive HBeAg and anti-HBs

BackgroundOccult infection of hepatitis B virus (HBV) has important impacts on both public health and clinical medicine.ObjectivesTo characterize the sequences of HBV S region in a chronic carrier with occult HBV infection.Study designSerological markers for HBV were tested by commercial kits. Western blotting was performed to detect HBsAg. PCR was used to amplify HBV S region; the resultant products were sequenced directly and cloned and then sequenced.ResultsTests with commercial kits showed that the carrier was HBsAg negative yet HBeAg positive. HBsAg was positive in Western blotting analysis. Although anti-HBs titers were as high as 5356–11,578 mIU/ml, serum HBV DNA was positive, ranging from 370 to 491 copies/ml. Wild type and mutant HBV coexisted in circulation. The mutant virus had mutations in both preS2 and S genes: the preS2 ATG mutated to ATA, and the S gene had a 15-nucleotide repeat insertion in the a determinant. By Blast search in the GenBank, the mutant virus had not been identified before. Nevertheless, the carrier had no signs of liver dysfunction during follow-up period.ConclusionWe identified a novel mutant HBV coexisted with wild type virus in a carrier with negative HBsAg and positive HBeAg and high level of anti-HBs.