Zika virus (ZIKV) is a major human pathogen and member of the Flavivirus genus. Previous studies have identified neutralizing antibodies from Zika patients that bind to quaternary epitopes across neighboring envelope (E) proteins, called E dimer epitopes (EDE). An asparagine-linked glycan on the “glycan loop” (GL) of the ZIKV envelope protein protects the functionally important “fusion loop” on the opposite E subunit in the dimer, and EDE antibodies have been shown to bind to both of these loops. Human EDE antibodies have been divided into two subclasses based on how they bind to the glycan loop region: EDE1 antibodies do not require glycosylation for binding, while EDE2 antibodies strongly rely on the glycan for binding. ZIKV GL was expressed on tobacco mosaic virus nanoparticles. Mice were immunized with GL or full-length monomeric E and the immune response was analyzed by testing the ability of sera and monoclonal antibodies to bind to GL and to neutralize ZIKV in in vitro cellular assay. We report here the existence of ZIKV moderately neutralizing antibodies that bind to E monomers through epitopes that include the glycan loop. We show that sera from human Zika patients contain antibodies capable of binding to the unglycosylated glycan loop in the absence of the rest of the envelope protein. Furthermore, mice were inoculated with recombinant E monomers and produced neutralizing antibodies that either recognize unglycosylated glycan loop or require glycan for their binding to monomeric E. We demonstrate that both types of antibodies neutralize ZIKV to some extent in a cellular virus neutralization assay. Analogous to the existing EDE antibody nomenclature, we propose a new classification for antibodies that bind to E monomer epitopes (EME): EME1 and EME2 for those that do not require and those that do require glycan for binding to E, respectively.

中文翻译：

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Zika聚糖环的免疫原性研究。

寨卡病毒（ZIKV）是主要的人类病原体，是黄病毒属的成员。先前的研究已经确定了来自Zika患者的中和抗体，该中和抗体与跨邻近包膜（E）蛋白的四级表位结合，称为E二聚体表位（EDE）。ZIKV包膜蛋白的“聚糖环”（GL）上的天冬酰胺连接的聚糖可保护二聚体中相对的E亚基上功能上重要的“融合环”，并且EDE抗体已显示与这两个环结合。基于人类EDE抗体与聚糖环区域的结合方式，它们已分为两个亚类：EDE1抗体不需要糖基化来结合，而EDE2抗体强烈依赖于聚糖来结合。ZIKV GL在烟草花叶病毒纳米颗粒上表达。用GL或全长单体E免疫小鼠，并通过在体外细胞测定中测试血清和单克隆抗体结合GL并中和ZIKV的能力来分析免疫应答。我们在这里报告ZIKV中度中和抗体的存在，该抗体通过包括聚糖环在内的表位与E单体结合。我们显示，来自人类寨卡病毒患者的血清中含有能够与未包膜蛋白其余部分结合的未糖基化聚糖环的抗体。此外，小鼠用重组E单体接种，并产生中和抗体，该中和抗体识别未糖基化的聚糖环或需要聚糖才能与单体E结合。我们证明，两种类型的抗体在细胞病毒中和测定中均能中和ZIKV。