Nucleotide sequence analysis of the hepatitis B virus X-precore region in chronic hepatitis B

In chronic hepatitis B virus (HBV) infection, hepatitis B e antigen (HBeAg) is seroconverted from positive to negative. HBeAg is associated with active replication of the HBV and a high disease activity. To elucidate the relation between HBV X-precore region mutation and HBeAg status, HBV replication and liver function were surveyed in chronic hepatitis B patients. HBV DNA was isolated from fifteen serum samples of seven patients with chronic hepatitis B, and the X-precore region was amplified by PCR and sequenced. Each sequence was compared with the consensus sequence of each patient. The most frequently observed mutations were A to T at nt. 1762 and G to A at nt. 1764 in the core promoter region and G to A at nt. 1896 in the precore region. These mutations were more commonly found in HBeAg-negative serum samples than in HBeAg-positive (p < 0.001, respectively). Of 7 serum samples with the wild type or wild/mutant mixed type in the precore region, 6 were HBeAg-positive and had a high HBV DNA polymerase (DNA-p) activity and serum alanine aminotransferase (ALT) elevation. On the other hand, 6 serum samples with the mutant type only were HBeAg-negative and had a low DNA-p activity and normal ALT level. Interestingly, 2 serum samples with the mutant type only had a high DNA-p activity and serum ALT elevation, despite being HBeAg-negative. Core promoter region mutation was not associated with HBV markers or serum ALT level. In conclusion, mutation at nt. 1896 in the precore region causes seroconversion from HBeAg-positive to -negative and is accompanied by reductions of viral replication and hepatitis activity.