Sequence diversity analysis of CagA gene and corresponding protein in Helicobacter pylori

Prevalence of basal core promoter and precore mutations in Chinese chronic hepatitis B patients and correlation with serum HBeAG titers

The A1762T and G1764A mutations in the basal core promoter (BCP) region and the G1896A mutation in the precore (PC) region of hepatitis B virus (HBV) genome are found commonly in HBeAg-negative patients. Experiments in vitro suggest that BCP and PC mutation reduce and abolish HBeAg expression, respectively. In the present study, the prevalence of the BCP and PC mutations were determined in 207 patients with HBeAg positive chronic hepatitis B from China and correlated with the titers of serum HBeAg. None of the patients received antiviral therapy. The HBV genotype was determined by direct sequencing of the HBsAg gene. The BCP and PC mutations were detected by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and confirmed by DNA sequencing. The HBeAg titer was measured by the microparticle enzyme immunoassay. Fifty-one of the 207 patients (24.6%) were infected with genotype B and the remainder with genotype C. The BCP mutations were detected in 103 patients (50%) while the PC mutation was present in 43 (20.8%). Thirteen patients (6.3%) harbored both BCP and PC mutations. No significant difference in the titers of HBeAg was found between patients infected with the two HBV genotypes, but the presence of either the BCP or PC mutation was associated with reduced HBeAg titer (P < 0.05). The presence of both the BCP and PC mutations was accompanied by even lower HBeAg titer (P < 0.05). These findings confirm that in patients with HBeAg, the BCP and PC mutations reduced the expression of HBeAg.