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

中和HIV-1的Fab二聚化糖链反应抗体的结构特征 多聚糖保护膜覆盖HIV-1包膜(Env)，限制抗体广泛中和 抗体(BNab)表位。长期以来，2G12一直是唯一一个HIV-1 bNab仅与 Env葡聚糖盾。其独特的VH域交换架构，交换了两个FAB臂，以创建 FAB二聚化的免疫球蛋白，允许2G12同时与4个糖链相互作用，从而支持通常较弱的 蛋白质-多聚糖通过亲和力结合。我们最近表征了结构多样化的FAB-二聚体， 针对HIV-1Env的葡聚糖反应性(FDG)抗体。与2G12不同，这些新发现的 FDG抗体不是结构域交换的；相反，Fab二聚化是通过包括相互作用在内的机制发生的 FAB二硫键、疏水和氢键相互作用。我们进一步表明，HIV-1环境病毒- 靶向FDG抗体识别SARS-CoV-2刺激物S2亚基中的糖聚糖簇。而我们的 结果揭示了抗体Fab二聚化识别糖链簇的不同方式，几个问题 关于Fab二聚化和葡聚糖识别的机制仍然存在。理解这些意志 提供对B细胞对多糖的反应的发展的见解。 本研究的总体目标是了解抗体Fab二聚化的结构决定因素。 导致高亲和力的葡聚糖识别。2G12和其他FDG bNAb特异性识别保守的 HIV-1包膜上的聚糖簇由独特的非自我呈现的自糖组成，为 寄主和入侵病原体上的多糖的免疫学鉴别。这其中的科学前提是 格兰特认为，确定Fab二聚化抗体识别多糖的结构机制将允许 针对不同糖基化病原体的特定靶点。这笔赠款的创新来自(I)扩大了 FDG抗体谱系，(Ii)FDG抗体普遍存在的证明，(Iii)发现 结构域交换的VH构象不是HIV-1中和所必需的。

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.