儿童感染的乙型肝炎病毒S基因的分子特征

Characteristics of S Gene of Hepatitis B Virus in Infected Children

目的初步调查儿童感染的乙型肝炎病毒表面抗原的基因特征。方法收集10名HBV感染的儿童血清标本,抽提血清中的HBV DNA,采用PCR扩增HBV S基因并测序,利用Genotyping软件对PCR产物序列进行分型,并分析HBV S基因的突变情况。结果 10份血清标本中,扩增出HBV S基因并成功测序6份,其余4份扩增阴性不满足测序要求。6份PCR产物所测序列标本经Genotyping比对后,均属于B型,与NCBI收录的参考序列AF100309同源性最高;5例是adw,1例是ayw。HBV S基因中编码"a"抗原决定簇的核苷酸序列突变点分别为G529A、T531C、C534A、T562A、T581A、A589C。编码"a"抗原决定簇的氨基酸序列突变点分别为I126T、P127T、S143T、G145A。核苷酸突变点G529A、T562A不引起编码"a"抗原决定簇的氨基酸序列突变,为无义突变。而其他4点突变均可引起编码"a"抗原决定簇相应氨基酸序列发生改变。结论所调查儿童主要感染B基因型HBV;其感染的HBV S抗原"a"决定簇的氨基酸序列出现I126T、P127T、S143T、G145A的突变,可能是逃避乙肝疫苗诱导的免疫保护的一种机制。

Objective To investigate the gene characteristics of hepatitis B virus surface antigen（HBsAg） in infected children.Methods Serum samples were collected from 10 children infected with hepatitis B virus（HBV）,and HBV DNA was extracted for S gene amplification by PCR.The PCR products were sequenced and compared with standard sequence,and the genotype was analyzed using on-line genotyping.Results Among the 10 serum samples,S gene was amplified and sequenced in 6 samples,and the other 4 samples did not meet sequencing requirements.Six sequenced products belonged to type B after sequence alignment with genotyping and had the highest homology with NCBI＇s reference sequence AF100309.Five cases were infected with serotype adw and 1 case with serotype ayw.In the ＂a＂ determinant of hepatitis B surface antigen,6 mutation sites（G529A,T531C,C534A,T562A,T581A and A589C） were found in the nucleotide sequence.Four mutation sites（I126T,P127T,S143T and G145A） were found in amino acid sequence.Mutations of T531C,C534A,T581A and A589C（except G529A and T562A） could cause an alteration in the corresponding amino-acid sequence.Conclusion Children are mainly infected with HBV genotype B.Mutations of I126T,P127T,S143T and G145A in amino acid sequence of ＂a＂ determinant of HBV S region may be a mechanism for evading the immune response induced by HBV vaccine.