诱导乙肝疫苗抗原特异性滤泡辅助性T细胞分化及记忆状态的探讨

Neutralizing antibodies against hepatitis B surface antigens (HBsAg) conferred by neonatal hepatitis B vaccination wane after 10-15 years. Some of the vaccinees, mainly those born to HBsAg-positive mothers, occurred overt or occult HBV infection during adolescence. Currently, no convincing evidences demonstrated that HBsAg-specific memory cells were generated and these cells were long-lasted after the vaccination in the infants who were born to HBsAg-positive mothers. Follicular T helper (Tfh) cells have been demonstrated as the critical cells in regulating humoral immune responses. The T cells with high-affinity TCR but not the cells with low-affinity TCR in the neonates born to the HBsAg-positive mothers might be impaired/deleted as negative selection. In this proposal, we aim to investigate the mechanisms regulating the Tfh cell differentiation after the activation of the T cells with low affinity with HBsAg, and the factors that affect generation and maintaining of the memory Tfh. To explore the potentials to promote the Tfh generation and maintaining after enhancing the monocyte-derived dendritic cell activity, and blocking the inhibitory functions of PD1 and CTLA4. It will be helpful to develop better vaccination stratifies for preventing hepatitis B infection and the related diseases when these questions are answered.

乙肝疫苗激发的体液免疫是预防慢性乙肝病毒(HBV)感染的基础，但新生儿接种疫苗后产生的保护性抗体在10-15年后消退，部分出生于乙肝表面抗原(HBsAg) 携带母亲的接种者，在青春期发生慢性HBV感染，表明疫苗抗原诱导的免疫保护作用难以在这些人群中长期存在。滤泡辅助性T细胞(Tfh)在体液免疫，即B淋巴细胞活化、分化及记忆细胞产生中发挥关键作用。HBsAg携带母亲新生儿体内识别HBsAg的高亲和力型T细胞在胚胎发育过程中可能被清除，但存在低亲和力型抗原识别细胞。由低亲和力型T细胞分化产生的HBsAg特异性Tfh细胞的功能特征是什么？能否在机体内长期存在？本研究中我们将探讨与HBsAg具有不同亲和力的T细胞活化后，所产生的特异性Tfh特征与功能特性，影响HBsAg特异性Tfh记忆细胞产生及维持的因素。解决上述问题将有助于通过疫苗接种策略，更好地预防慢性HBV感染及其所导致的相关性疾病。

乙肝疫苗诱导的抗HBs是预防慢性HBV感染的基础，通过人群和实验分析，本研究获得如下结果：.1.新生儿乙肝疫苗接种后慢性HBV再感染：新生儿按0-1-6标准程序完成疫苗免疫，并在儿童期(10-11岁)获得保护后，部分个体成年后(23-28岁)发生慢性HBV再感染，与疫苗诱导的抗HBs中和抗原表位本身突变关系不大。.2.成年后(23-28岁)发生慢性HBV再感染的高危儿童特征：出生于HBsAg阳性母亲，其血清抗HBs滴度低于10mIU/ml。.3.对10-11岁儿童进行一剂乙肝疫苗加强免疫预防23-28岁慢性HBV感染效果：高危儿童在10-14岁期间注射一剂乙肝疫苗加强免疫，可显著降低其成年后慢性HBV再感染风险；出生于HBsAg阴性母亲，按0-1-6标准程序完成疫苗全程免疫后，无论其血清抗HBs是否低于10mIU/ml，成年后(23-28岁)维持预防慢性HBV再感染能力。.4.通过脐带血的短暂暴露途径，存在HBsAg应答的特异性T细胞，但产生IFN-γ, IL-4, IL-21的T细胞数量显著减少；发生感染导致HBsAg持续暴露后，抗原特异性Tfh难以产生,可能与HBsAg特异性T细胞抗原识别受体形成有关。.5.转录因子BCL-6和GATA-3双重控制HBsAg特异性Tfh产生和记忆维持，其主要介导的细胞因子是IL6，IL21。.基本完成预定主要目标，已在专业领域发表部分研究结果。其中研究结果【Vaccine 35 (2017) 1064–1070】发表后，该领域专家Ellie Carmody, New York University School of Medicine, USA在International Journal of Infectious Diseases 60 (2017) 88–90发表专家述评：Time to re-evaluate the effect of the adolescent booster of hepatitis B vaccine，评价了研究的重要意义。研究结果也作为证据之一被国内首版“中国肝癌一级预防专家共识（2018）”采纳。作为代表性论著之一，获2018 年度高等学校科学研究优秀成果奖科技进步二等奖(2018-267，我国农村地区原发性肝癌一级预防模式的建立和推广应用)。但仍有部分研究尚未完全成文发表，争取2020年完成