乙型肝炎病毒宫内传播的分型

Genotyping study of hepatitis B virus in its intrauterine transmission

目的研究乙型肝炎(乙肝)病毒(HBV)分型在乙肝病毒宫内传播的特点。方法对广州市三家医院的135例HBsAg孕产妇及其139例新生儿外周血及部分婴儿随访标本,巢式PCR扩增HBVS区基因部分片段,限制性核酸内切酶酶切PCR产物,比较酶切片段长度多态性(RFLP),以确定HBV基因型。直接测序并与Genebank相应序列比较。结果7例新生儿发生HBV的宫内传播,阳性率为7/139(5.0%),PCR-RFLP方法检测到B、C型各3/7例,D基因型1/7例。宫内传播过程中母婴HBV的基因型保持一致。S基因直接分型与上述结果一致。该7组母婴均无乙肝临床症状与体征。结论广州地区母婴宫内传播HBV以C、B基因型为主,宫内传播过程中及免疫压力下HBV-DNA发生碱基突变,但未发生在限制性内切酶的酶切位点上,尚不能由HBV基因分型对HBV感染儿的预后进行推测。

Objective To study the characteristics of intrauterine transmission of hepatitis B virus (HBV) of different geno-types from mother to the newborn babies. Methods 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, sam-pling 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 frag-ments length polymorphism (RFLP) to determine the HBV genotype. Direct sequence analysis was conducted and the results compared with the sequences available in Genebank. Results HBV infection occurred in 7 (5.0%) neonates through intrauter-ine transmission, among whom 3 were identified as being infected with C genotype, 3 with B genotype and 1with D genotype, all identical to the genotypes afflicting their mothers. All of the 7 mothers and the babies were asymptomatic. Conclusion 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.