抚州市免疫儿童感染的HBV “a”抗原决定簇变异分析

Study on “a” deteminant mutation of HBV in viral carrier children following universal HB vaccination in Fuzhou city

(1)目的研究抚州地区乙型肝炎免疫的儿童乙型肝炎患者HBV表面抗原区"a"抗原决定簇变异特征。(2)方法将抚州地区按照免疫规划程序按时按质接受乙肝疫苗接种的儿童设定为研究对象,收集多中心获得性乙肝免疫儿童血清标本8618份,采用ELISA法筛选HBV表面抗原(HBsAg)阳性样本,提取阳性标本中的HBV DNA,应用聚合酶链反应(PCR)体外酶促扩增HBV S基因片段,将扩增所得到的目的片段进行序列检测,并与参考序列对比,分析儿童感染的HBV血清亚型,确定变异株"a"抗原决定簇的变异位点。(3)结果从8618份血清样品中,检测出158份HBsAg阳性标本(阳性率1.83%)。PCR成功扩增HBV S基因并测序135份,112份属于B基因型,23份属于C基因型。B基因型中105份为adw血清型,7份为ayw血清型;C基因型均为adr血清型。分析发现16份标本存在"a"抗原决定簇变异(变异率11.85%);16份标本的"a"抗原决定簇24个氨基酸位点中,有7个位点发生突变(突变率29.17%);"a"抗原决定簇两茎环间的变异率、基因型间的变异率无显著性差异(P>0.05)。(4)结论在江西抚州地区乙肝疫苗免疫儿童人群中检测出HBV"a"抗原决定簇变异株,但未见特异位点突变的免疫优势变异株。

Objective The study was to analyze the variaiton of＂a＂antigen determinant in the S antigen of HBV infecting the vaccinated children in Fuzhou area.Methods 8618 serum from the children vaccinated with hepatitis B vaccine were collected.HBV-M was tested using ELISA.HBV DNA was extracted from the positive HBsAg serum for S gene amplification by PCR.The PCR products were sequenced and aligned with the reference sequences to analyze the mutation sites in HBV＂a＂antigen determinant.Genotype was determined using on-line genotyping software.Results 158 samples were tested to be HBsAg positive out of 8618 serum with the positive rate of 1.83%.The S gene of 135 samples from 158 HBsAg positive serum were amplified and sequenced.112 cases were determmined to be HBV genotype B,among which 105 cases belong to serotype adw and 7 of serotype ayw were found.The another 23 cases belonged to HBV genotype C and were serotype adr.16 of 135 samples were found to carry site mutation in ＂a＂determinant with the variation rate of 11.85%.Seven sites within the 24 amino acids spanning the ＂a＂antigen region were mutated with the variation rate of29.17%.The difference of mutation between two loops of＂a＂determinant,HBV genotype B and genotype C and male and female children were not different statistically（P 0.05）.Conclusion The HBV strains with mutations in ＂a＂antigen determinant were detected in the infected children immunized with HBV vaccine.But immune dominant HBV strain of the mutation in a specific site was not found.