[Genotyping study of hepatitis B virus in its intrauterine transmission]

To study the characteristics of intrauterine transmission of hepatitis B virus (HBV) of different genotypes from mother to the newborn babies.

One hundred and thirty-five HBsAg-positive pregnant women from 3 hospitals in Guangzhou municipality and their 139 newborn babies were enrolled in this study. Peripheral blood samples were collected from both the mothers before delivery and the neonates within 3 d after birth, and during the follow-up survey, sampling was also performed in some of the newborn babies. Nested-PCR was employed for the amplification of the S region of HBV genome, the product of which was subjected to digestion with restriction endonuclease to compare the restriction fragments length polymorphism (RFLP) to determine the HBV genotype. Direct sequence analysis was conducted and the results compared with the sequences available in Genebank.

HBV infection occurred in 7 (5.0%) neonates through intrauterine transmission, among whom 3 were identified as being infected with C genotype, 3 with B genotype and 1 with D genotype, all identical to the genotypes afflicting their mothers. All of the 7 mothers and the babies were asymptomatic.

C and B genotypes are predominant in intrauterine transmission of HBV in Guangzhou, and base mutation, rather than mutation at the endonuclease digestion site, may take place during intrauterine transmission due to impact of the immune system. The genotyping results, however, can not help make prognostic assessment of the infected babies.