住院孕妇显性和隐匿性HBV感染及分子进化特征分析

Overt and occult hepatitis B virus infection among hospitalized pregnant women: proportion and phylogenetic analysis

目的了解住院孕妇显性和隐匿性乙型肝炎病毒感染(OBI)及其病毒株S基因分子进化特征。方法采用以医院为基础的住院孕妇队列研究,招募2012年6月1日—2013年3月15日医院产科孕妇1 130人,收集人口学资料和血清,并采用罗氏电化学发光法检测乙型肝炎病毒表面抗原(HBsA g)及巢式PCR进行HBV S片段的扩增并测序,分析并比较住院孕妇显性乙型肝炎病毒(HBV)感染与OBI的人口学分布特征及S区序列变异。结果在1 130名孕妇中,HBV感染比例为16.55%,其中显性HBV感染和OBI的比例分别为8.4%和8.1%。共获得136株HBV S基因序列,其中基因C型17株,基因B型119株。与基因B型显性HBV株相比,OBI株出现更高的核苷酸和氨基酸替换率,8个核苷酸位点出现统计学显著的次要等位基因频率,并导致HBV S基因和对应的HBV P基因出现非同义氨基酸替换,分别为5个(G44E、T126A、R129Q、W156L和Y200F)和4个(I438L、K478N/D、N481S/D和L511F)。此外,3例OBI出现W35终止码替换,1例OBI出现第123位和第124位点的插入替换。结论住院孕妇存在较高的HBV感染比例,OBI与显性HBV感染比例大致相当;B基因型OBI株出现统计显著的核苷酸和/或氨基酸位点替换,可能与OBI的发病机制有关。

Objective To examine the proportion and phylogeny of overt and occult hepatitis B virus （HBV） infec- tion （OBI） among hospitalized pregnant women. Methods We performed a prospective study which continuously re- cruited hospitalized pregnant women from June 1 st, 2012 to March 15th, 2013. Demographic data were collected. Blood samples of the pregnant women were collected for the detection of HBV surface antigen （HBsAg） by using Roche quantitative electrochemiluminescence immunoassay and HBV S gene by using nested polymerase chain reaction and the gene was sequenced then. The differences in demographics and variation of HBV sequences between the pregnant women with overt and occult HBV infection were analyzed. Results Among the 1 130 pregnant women recruited,the propor- tions of overall,overt and occult （or HBsAg-negative） HBV infection were 16. 6% （ 187/1 130） ,8.4% and 8. 1% re- spectively. Totally 136 HBV strains were identified, of which 119 were classified as genotype B and available for further analysis ;comoared with the overt strains, the occult strains showed higher substitution rates and exhibited statisticallv sig-nificant minor allellic frequencies among eight nucleotide sites,leading to non-synonymous substitutions-five amino acid sites （G44E,T126A,Q129R,W156L and F200Y） in HBV S gene and four （I438L.K478N/D.N481S/D and L511F） in HBV P gene. In addition, we found three occult strains with stop codon mutation at the 35th amino acid and one occult strains with an insert mutation between the 123th and 124th amino acid. Conclusion For hospitalized pregnant women, the proportion of with occult HBV infection, routinely screened as non-HBV cases, is roughly the same as that of with overt HBV infection, which may pose a potential risk for mother-to-infant transmission. Several OBl-specific nucleotide substitutions were identified and may be linked with the occurrence of OBL