Anti-flavivirus B cell response analysis to aid vaccine design

寨卡病毒 (ZIKV) 是黄病毒家族的一员，作为一种传染性病原体出现，可导致 最近流行病期间的全球健康危机。 ZIKV 感染可导致吉兰-巴利综合征 成人以及妊娠期间严重的胎儿神经畸形和胎儿死亡。寨卡病毒感染 主要通过蚊虫叮咬传播，性传播和垂直传播 孕妇感染胎儿也助长了近期的疫情。理想情况下，有效的 ZIKV 疫苗应提供杀菌免疫力，阻止最初的病毒传播，以预防 随后感染引起的发病。目前，尚无批准用于疾病的 ZIKV 疫苗 预防。以 prM-E 形式表达的膜 (M) 和包膜蛋白 (E) 是常见的 当前 ZIKV 候选疫苗的抗原选择，作为中和抗体 (nAb) 抗 prM-E 可以阻止病毒进入。然而，这种基于 PrM-E 的新生 ZIKV 疫苗可以 增加登革热病毒（DENV）的传染性，登革热病毒是另一种黄病毒，其流行地区 与 ZIKV 很大程度上重叠。由于E蛋白之间具有高度的序列同源性 对于 ZIKV 和 DENV，ZIKV prM-E 疫苗可能会刺激抗体的产生，这些抗体 非中和作用，但与 DENV E 蛋白发生交叉反应。如果随后发生登革热 病毒感染时，当抗病毒效果不佳时，可能会发生抗体依赖性增强（ADE） ZIKV 抗体与 DENV 病毒结合，从而增强 DENV 进入宿主细胞 并加剧登革热症状。预防产生 ADE 倾向抗体的策略 最近已经描述了修饰的 ZIKV 免疫原，不幸的是，它显示 对小动物的保护效果不佳。在这里，我们重点关注应用基于结构的 疫苗设计，开发新的候选疫苗，提高免疫原性并减少 DENV 感染的 ADE 潜力。在初步研究中，我们的主要候选疫苗配制于 优化的佐剂对 ZIKV 攻击的免疫小鼠显示出几乎完全的保护作用， 并废除了通过体外测定评估的 ADE 潜力。有效的单克隆 ZIKV nAb 靶向 主要的 ZIKV E 蛋白 nAb 决定簇，包括四元 E-二聚体依赖性表位 从免疫小鼠身上分离证实了设计原理。在此应用程序中，我们将扩展我们的 通过在 B 细胞/抗体反应分析和结构指导下进一步设计免疫原来努力 研究 ZIKV E 蛋白-抗体相互作用以改善我们的主要候选疫苗目标 实现灭菌免疫，在小动物模型中进行评估。如果成功的话，这项研究将 致力于 (i) 开发有效且安全的 ZIKV 疫苗，以及 (ii) 深化我们的研究 了解对黄病毒感染和免疫接种的免疫反应。

Zika virus (ZIKV) is a member of flavivirus family that emerged as an infectious agent causing global health crisis during recent epidemics. ZIKV infection can cause Guillain-Barré syndrome in adults, and severe fetal neuromalformations and fetal death during pregnancy. ZIKV infection is primarily transmitted by mosquito bite, while sexual transmission and vertical transmission from infected pregnant women to fetus also contribute to the recent epidemic. Ideally, an effective ZIKV vaccine should provide sterilizing immunity that blocks the initial viral dissemination to prevent subsequent infection-caused morbidity. Currently, there is no approved ZIKV vaccine for disease prevention. The membrane (M) and envelope protein (E) expressed as prM-E form is a common antigen choice for current vaccine candidates against ZIKV, as neutralizing antibodies (nAb) against prM-E can prevent viral entry. However, such nascent PrM-E based ZIKV vaccines can increase the infectiousness of the dengue virus (DENV), another flavivirus of which endemic area largely overlaps with ZIKV. Due to the high degree of sequence homology between the E proteins of ZIKV and DENV, the ZIKV prM-E vaccine may stimulate the production of antibodies that are non-neutralizing but cross-reactive with the DENV E protein. In the event of a subsequent dengue virus infection, antibody-dependent enhancement (ADE) can occur when the suboptimal anti- ZIKV antibodies bind to the DENV virus, which thereby enhance the entry of DENV into host cells and exacerbate dengue symptoms. Strategies to prevent the induction of ADE-prone antibodies have been described recently for modified ZIKV immunogens, which unfortunately display suboptimal protection efficacy in small animals. Here, we focus on applying structure-based vaccine design to develop novel vaccine candidates with improved immunogenicity and reduced ADE potential for DENV infection. In preliminary study, our lead vaccine candidate formulated in optimized adjuvant showed nearly complete protection in immune mice challenged with ZIKV, and abolished ADE potential assessed by in vitro assays. Potent monoclonal ZIKV nAbs targeting the major ZIKV E protein nAb determinants including the quaternary E-dimer dependent epitope isolated from immune mice confirmed the design rationale. In this application, we will extend our effort via further immunogen designs guided by B cell/antibody response analysis and structural investigation of ZIKV E protein-antibody interactions to improve our lead vaccine candidate aiming at achieving sterilizing immunity, to evaluate in small animal models. If succeeds, this study will contribute to (i) the development of an effective and safe ZIKV vaccine, and (ii) deepening our understanding of immune response to flavivirus infections and immunizations.