High conservation of hepatitis B virus surface genes during maternal vertical transmission despite active and passive vaccination.

OBJECTIVE Our purpose was to explore the relationship between hepatitis B virus (HBV) gene heterogeneity and maternal vertical transmission. METHODS HBsAg-positive mothers and their neonates were selected and classified into a vertical infection neonate group (group N), a vertical infection mother group (group M) and a control group (group C). Serum HBsAg and HBeAg were examined. HBV gene fragments, including the pre-S1, and pre-S2 and S coding regions, were amplified and sequenced, and the genotype and serotype of the sequences were identified. Mutation sites and frequency of mutations were then compared between group N and group C. RESULTS A total of 104 HBV clone sequences were obtained. All obtained sequences belonged to genotype C and serotype adr. Upon comparing sequences between group N and group C, 4 nonsynonymous mutations were found with significant difference in mutation frequency (p < 0.05). When the mothers were both HBsAg and HBeAg positive, 10 nonsynonymous mutations were found. The frequencies of these mutations were significantly lower in group N than in group C (p < 0.05). CONCLUSION The 10 HBV mutations were negatively associated with vertical transmission when maternal HBeAg was positive. Furthermore, the species that were vertically transmitted to the fetus were mainly wild-type.