Molecular Basis of Flavivirus Cross-Neutralization by Human Antibodies

摘要 寨卡病毒（ZIKV）和四种登革热病毒（DENV）血清型是新出现的蚊媒黄病毒， 严重威胁人类健康。暴露于原发性登革病毒感染的人会形成长期血清型- 特异性中和和保护性抗体（Abs）。暴露于继发性DENV感染的个体 新的血清型开发了一种新型的交叉中和和保护性抗体， 个体以前未遇到的血清型。虽然特定类型的人类的分子特性 中和抗体已经被很好地定义，关于DENV交叉的起源和性质知之甚少， 二次感染后诱导产生中和抗体。在这个项目中，我们将使用一个既定的人类挑战， 继发性DENV感染模型，以检验继发性感染激活和扩展记忆的假设 从初次感染中分离B细胞以产生体细胞突变的Ab， 在DENV血清型之间是保守的（特异性目的1）。我们还将定义分子特异性， 在具有实验室确认的ZIKV感染的美国旅行者中诱导的中和Ab的功能特性。 基于我们对DENV的原发性Ab反应的发现，我们提出暴露于ZIKV的人， 原发性黄病毒感染产生靶向四级结构包膜的型特异性中和Ab（E） 在病毒表面上展示的蛋白质表位（特异性目标2）。当重复感染不同的登革病毒时， 血清型诱导持久的交叉DENV中和抗体，但不清楚这种应答是否可以扩大到中和 ZIKV。通过分析暴露于二次DENV感染和DENV免疫的人中的Ab应答， 感染ZIKV的个体，我们将确定促进ZIKV的分子机制和结构特征。 或限制DENV血清复合物和ZIKV之间Ab交叉中和的宽度（特异性目标3）。 我们的研究的重要性是强调了令人失望的结果，最近报道的四价活 减毒DENV疫苗以诱导对4种DENV血清型的平衡交叉保护性免疫。我们的研究 与成功设计和评估下一代安全有效的疫苗有关， 新兴黄病毒此外，登革热和登革热之间的交叉中和和保护性免疫模式 寨卡病毒可能解释了与亚洲相比，拉丁美洲ZIKV的爆炸性传播。

Abstract Zika virus (ZIKV) and the four-dengue virus (DENV) serotypes are emerging mosquito-borne flaviviruses that pose serious threats to human health. People exposed to primary DENV infections develop long-term serotype- specific neutralizing and protective antibodies (Abs). Individuals exposed to secondary DENV infections with a new serotype develop a novel class of cross neutralizing and protective Abs that are even effective against serotypes not previously encountered by the individual. While the molecular properties of type-specific human neutralizing Abs have been well-defined, little is known about the origin and properties of DENV cross- neutralizing Abs induced after secondary infection. In this project, we will use an established human challenge model of secondary DENV infection to test the hypothesis that secondary infections activate and expand memory B cells from primary infections to generate somatically mutated Abs that bind with high affinity to epitopes that are conserved between DENV serotypes (Specific Aim 1). We will also define the molecular specificity and functional properties of neutralizing Abs induced in US travelers with laboratory confirmed ZIKV infections. Building on our discoveries about primary Ab responses to DENVs, we propose that people exposed to ZIKV as a primary flavivirus infection develop type-specific neutralizing Abs that target quaternary structure envelope (E) protein epitopes displayed on the viral surface (Specific Aim 2). While repeat infections with different DENV serotypes induce durable cross DENV neutralizing Abs, it is unclear if this response can expand to neutralize ZIKV. By analyzing Ab responses in people exposed to secondary DENV infections and DENV immune individuals infected with ZIKV, we will determine the molecular mechanisms and structural features that promote or restrict the breadth of Ab cross-neutralization between the DENV sero-complex and ZIKV (Specific Aim 3). The importance of our studies is underscored by the disappointing results recently reported with tetravalent live attenuated DENV vaccines to induce balanced cross-protective immunity to the 4 DENV serotypes. Our studies are relevant to the successful design and evaluation of the next generation of safe and effective vaccines against emerging flaviviruses. Moreover, patterns of cross-neutralizing and protective immunity between dengue and Zika viruses may explain the explosive spread of ZIKVs in Latin America compared to Asia.