乙型肝炎表面抗原阳性孕妇所生新生儿免疫阻断后隐匿性乙型肝炎病毒感染状况及相关机制的前瞻性队列研究

It was discovered in recent years that some infants born to HBsAg-positive mothers could develop occult HBV infection (OBI) despite immuno-prophylaxis. Though the detection of HBV DNA in liver tissue is regarded as golden standard for the diagnosis of OBI, serial serum HBV DNA assays with high sensitivity and specificity are crucial in the case of infants for the unavailability of liver biopsy samples and the highly dynamic HBV DNA profiles showing phases of absent viremia alternating with phases of very low but detectable viral load in OBI individuals. Existing studies are almost exclusively retrospective and cross-sectional, with incomplete viral information of included mothers and ambiguous vaccination procedures. And also the assays used in those studies varied greatly in sensitivity and specificity, most of which did not approach the optimal lower limit of detection for HBV DNA. The present project aims to conduct a longitudinal study in prospective cohorts of HBV carrier mothers and their infants to observe the real prevalence of OBI in infants after standard vaccination by quantitative serum HBV DNA evaluation utilizing Abbott m2000 system and determine the effects of different immune strategies on the occurrence of OBI. For revealing the possible virological factors associated with OBI, our group intends to analyze and compare maternal HBV quasi-species diversity and complexity in serum samples collected before delivery between OBI group and non-OBI group, by means of HBV whole genome amplification, cloning and sequencing. Host immuno-genetic polymorphisms may also explain variations among different individuals in terms of OBI. We propose to find the potential role that APOBEC3B, 3G gene polymorphisms play in the set of OBI by PCR-RFLP. This project would hopefully provide new insights into improvement of current immuno-prophylaxis against HBV vertical transmission.

近年发现HBsAg阳性母亲所生新生儿免疫阻断成功后，部分婴儿存在隐匿性HBV感染（OBI）状况。肝组织中HBV DNA阳性是OBI诊断金标准，但婴儿无法进行肝活检；OBI患者血清病毒载量很低，可测与不可测交替，故应采用高灵敏度和特异度方法连续随访检测血清HBV DNA。现有婴儿免疫后OBI研究均为回顾性、横断面研究。且纳入研究的婴儿免疫策略不清楚、母亲资料不完整、检测方法不统一且陈旧。因此，本研究拟利用已建立的母婴配对、前瞻性随访队列，采用Abbott m2000系统定量检测血清HBV DNA，明确免疫后婴儿OBI发生率及不同免疫策略对OBI的影响；并采用HBV全基因组扩增克隆测序技术从母亲产前血清HBV准种多样性及复杂度揭示OBI可能的病毒学因素；采用PCR-RFLP等方法分析APOBEC3B、3G基因多态性，揭示OBI发生相关的宿主免疫遗传机制，为完善乙肝母婴传播阻断新策略提供依据。

近年发现HBsAg阳性母亲所生新生儿免疫阻断成功后，部分婴儿存在隐匿性HBV感染（OBI）状况，但OBI的确切发生率及可能的发生机制尚不清楚。本研究利用课题组建立的慢性乙型肝炎（乙肝）病毒（HBV）感染的母亲及其婴儿母婴配对前瞻性队列研究，发现对于HBsAg和HBeAg双阳性且HBV DNA高载量（>6log10 IU/mL）母亲所生婴儿，增加乙肝疫苗（HepB）剂量可显著提高婴儿抗-HBs水平并降低婴儿隐匿性HBV感染（OBI）发生率；进一步，通过前瞻性巢氏病例对照研究，发现HBV“a”决定簇的准种特征是HBV C2亚型母婴传播免疫阻断失败风险的潜在预测指标，并揭示了HBV准种特征在母婴传播后及其在婴儿体内的动态变化，这些研究结果为完善HBsAg阳性母亲所生婴儿免疫预防策略提供了重要的理论依据，并为慢性HBV感染的婴幼儿抗病毒治疗策略提供了病毒学证据。另外，本研究还对HBeAg阳性慢性HBV感染孕妇血清HBV DNA水平与HBsAg滴度的相关性及HBV PreS/S区基因变异对二者相关性的影响进行了研究，并对发生OBI婴儿体内参与先天性免疫的APOBEC3家族中的APOBEC3A（A3A）基因进行了全基因组测序分析，发现APOBEC基因多态性分析可能不适用揭示OBI发生相关的宿主免疫遗传机制。