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 聚糖屏蔽覆盖 HIV-1 包膜 (Env)，限制抗体获得广泛中和作用 抗体 (bnAb) 表位。 2G12 长期以来一直是 HIV-1 bnAb 仅与 Env 聚糖屏蔽。其独特的 VH 域交换架构，两个 Fab 臂交换以创建 Fab 二聚化 IgG，允许 2G12 同时与 4 个聚糖相互作用，从而增强通常较弱的作用 蛋白质-聚糖通过亲合力结合。我们最近表征了结构多样化的 Fab-二聚化， 针对 HIV-1 Env 聚糖屏蔽的聚糖反应 (FDG) 抗体。与2G12不同的是，这些新确定的 FDG 抗体未进行结构域交换；相反，Fab 二聚化是通过以下机制发生的： Fab 二硫键、疏水键和氢键相互作用。我们进一步表明，HIV-1 环境 靶向 FDG 的抗体识别了 SARS-CoV-2 刺突 S2 亚基中的聚糖簇。虽然我们的 结果揭示了抗体 Fab 二聚化以识别聚糖簇的多种方式，几个问题 关于 Fab 二聚化和聚糖识别的机制仍然存在。了解这些将 提供有关 B 细胞对聚糖反应发展的见解。 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。 2G12 和其他 FDG bnAb 特别识别保守的 HIV-1 包膜上的聚糖簇由独特的非自身呈现的自身糖组成，为 宿主聚糖和入侵病原体之间的免疫学区别。这样做的科学前提 授予的是，定义 Fab 二聚化抗体识别聚糖的结构机制将允许 特异性靶向多种糖基化病原体。本次资助的创新源自 (i) 扩大 FDG 抗体库，(ii) FDG 抗体普遍存在的证明，(iii) 发现 结构域交换的 VH 构象对于 HIV-1 中和来说不是必需的。

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.