H7N9诱导记忆B细胞产生交叉反应性H3杆部抗体的研究

针对流感病毒HA杆部表位的抗体具有广泛交叉反应性，能够与多种不同亚型病毒交叉结合。但是杆部抗体的诱导需要完整的HA空间构型，且通常情况下处于劣势。研究证实H1N1抗原性变异导致头部特异的记忆B细胞缺乏抗原刺激，处于劣势的杆部记忆B细胞被激活，产生交叉反应性抗体。我们在前期研究中证实部分健康人和流感疫苗接种者体内存在H3杆部记忆B细胞，可被诱导产生低水平的杆部抗体。但H7N9是否能诱导H3记忆B细胞产生具有免疫保护作用的杆部抗体尚未见报道。本研究拟采集遵义地区健康人及流感疫苗接种者外周血，用高通量mPlex-Flu法和ELISpot法筛选H3杆部抗体和H3记忆B细胞阳性个体,分离外周血B细胞，经灭活H7N9病毒刺激后，分析H7N9诱导的H3杆部抗体水平及其交叉反应，分析B细胞BCRCDR3组库变化，并在小鼠体内观察H7N9诱导的H3杆部抗体及其免疫保护作用，为流感的预防提供新的思路和策略。

Antibodies that target highly conserved epitopes on the stalk region of influenza HA display broad reactivity with group 1 and/or group 2 viruses. However, complete HA configuration is required to induce the stalk-reactive antibodies, and there is minimal chance of activating the rare memory B cells that recognize conserved and subdominant epitopes in the HA stalk in the presence of dominant epitopes in the global head. It is reported that memory B cells recognizing conserved epitopes are induced and produce cross-reactive antibodies because the shifted HA of pandemic H1N1viruses is missing many of the dominant and variable epitopes recognized by the majority of preexisting influenza-specific memory B cells. Our previous study showed that some of adults exposed to influenza viruses or immunized with vaccines possess stalk-reactive memory B cells which secreted low levels of cross-reactive antibodies. It is unclear that H7N9 viruses induce immuno-protecting IgG by memory B cells recognizing conserved epitopes in HA stalk. In this study, peripheral blood will be collected from health controls and donors immunized with influenza vaccines to analyze the HA stalk-reactive IgG and H3-specific memory B cells. B cells will be isolated from those subjects who possess stalk-reactive IgG and memory B cells recognizing H3 HA. Six days after B cells are stimulated with inactivated H7N9 virus, HA stalk-reactive antibodies and BCR CDR3 repertoire will be detected. The immune-protection of stalk-reactive antibodies will be assessed through attacking mice with H7N9 viruses. Our results will put forward a novel strategy for influenza prevention.