Structural characterization of Fab-dimerized glycan-reactive antibodies that neutralize HIV-1

中和HIV-1的Fab-二聚聚糖反应性抗体的结构表征 聚糖盾覆盖HIV-1包膜（Env），限制抗体进入广泛中和 抗体（bnAb）表位。长期以来，2G 12一直是唯一一种仅与HIV-1相互作用的HIV-1 bnAb。 Env聚糖屏障。其独特的VH结构域交换架构，两个Fab臂交换以创建一个 Fab-二聚化IgG允许2G 12同时与4个聚糖相互作用，从而支持通常较弱的 蛋白质-聚糖通过亲合力结合。我们最近表征了结构多样的Fab二聚化， 靶向HIV-1 Env聚糖屏障的聚糖反应性（FDG）抗体。与2G 12不同，这些新发现的 FDG抗体不是结构域交换的;相反，Fab二聚化通过包括相互作用的机制发生。 Fab二硫键、疏水键和氢键相互作用。我们进一步表明，HIV-1 Env- 靶向FDG抗体识别SARS-CoV-2刺突的S2亚基中的聚糖簇。虽然我们的 结果揭示了抗体可以通过多种方式Fab二聚化来识别聚糖簇， 关于Fab二聚化和聚糖识别的机制仍然存在争议。了解这些将 提供了对B细胞对聚糖反应的发展的见解。 本研究的总体目标是了解抗体Fab二聚化的结构决定因素 导致高亲和力聚糖识别。2G 12和其他FDG bnAb特异性识别保守的 HIV-1 Env上的聚糖簇由独特的非自我呈现的自我糖组成，为以下方面提供了基础： 宿主和入侵病原体上的聚糖的免疫区分。科学的前提是 格兰特认为，定义Fab二聚抗体识别聚糖的结构机制将使 特异性靶向不同的糖基化病原体。该补助金的创新来自（一）扩大 FDG抗体库，（ii）FDG抗体普遍存在的证明，（iii） 结构域交换的VH构象对于HIV-1中和不是必需的。

Structural characterization of Fab-dimerized glycan-reactive antibodies that neutralize HIV-1 A glycan shield covers the HIV-1 envelope (Env) limiting antibody access to broadly neutralizing antibody (bnAb) epitopes. 2G12 had for long been the only example of a HIV-1 bnAb that interacts solely with the Env glycan shield. Its unique VH domain-swapped architecture, with two Fab arms swapped to create a Fab-dimerized IgG, allows 2G12 to simultaneously interact with 4 glycans, thus bolstering typically weak protein-glycan binding through avidity. We have recently characterized structurally diverse Fab-dimerized, glycan-reactive (FDG) antibodies that target the HIV-1 Env glycan shield. Unlike 2G12, these newly identified FDG antibodies are not domain-swapped; instead, Fab dimerization occurred by mechanisms including inter- Fab disulfide linkage, hydrophobic and hydrogen bond interactions. We further showed that the HIV-1 Env- targeting FDG antibodies recognized a glycan cluster in the S2 subunit of the SARS-CoV-2 spike. While our results reveal diverse ways antibodies can Fab dimerize to recognize glycans clusters, several questions remain regarding the mechanisms of Fab dimerization and glycan recognition. Understanding these will provide insights into the development of B cell responses to glycans. The overall goals of this study are to understand structural determinants of antibody Fab dimerization leading to high affinity glycan recognition. That 2G12 and other FDG bnAbs specifically recognize a conserved glycan cluster on HIV-1 Envs that consists of self-sugars in a unique non-self presentation provides basis for immunological discrimination between glycans on host and invading pathogens. The scientific premise of this grant is that defining structural mechanisms for glycan recognition by Fab dimerized antibodies will allow specific targeting of diverse glycosylated pathogens. The innovations in this grant derive from (i) an expanded repertoire of FDG antibodies, (ii) the demonstration that FDG antibodies are prevalent, (iii) the finding that domain-swapped VH conformation is not necessary for HIV-1 neutralization.