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， 对人类健康构成严重威胁。接触初级DENV感染的人会发展成长期的血清型- 特异性中和和保护性抗体(Abs)。接触到继发性登革热病毒感染的个人 新的血清型发展了一类新的交叉中和和保护性抗体，甚至对 个体以前从未遇到过的血清型。而特定类型的人类的分子特性 中和抗体已经被很好地定义，对DENV杂交的起源和性质知之甚少 继发感染后诱导的中和抗体。在这个项目中，我们将使用一个既定的人类挑战 二次感染DENV模型验证二次感染激活和扩大记忆的假说 来自原发感染的B细胞产生体细胞突变的抗体，该抗体与 在DENV血清型之间保守(特异性目标1)。我们还将定义分子特异性和 实验室证实感染ZIKV的美国旅行者诱导的中和抗体的功能特性。 基于我们对DENV的初级抗体反应的发现，我们认为接触ZIKV的人作为 一种原发黄病毒感染可产生针对四元结构膜(E)的类型特异性中和抗体 显示在病毒表面的蛋白质表位(特异靶2)。而不同DENV的重复感染 血清型诱导持久的交叉DENV中和抗体，目前尚不清楚这种反应是否可以扩大到中和 齐科夫。通过分析接触二次DENV感染和免疫的人群的抗体反应 感染ZIKV的个体，我们将确定其促进分子机制和结构特征 或限制DENV血清复合体和ZIKV之间抗体交叉中和的广度(具体目标3)。 最近报道的四价LIVE令人失望的结果突显了我们研究的重要性 减毒的DENV疫苗可诱导对4种DENV血清型的平衡交叉保护免疫。我们的研究 关系到下一代安全有效的疫苗的成功设计和评估 新出现的黄病毒。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，ZIKV在拉丁美洲的爆炸性传播。

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.