Díaz-Salinas Marco A, Chatterjee Debashree, Nayrac Manon, Medjahed Halima, Prévost Jérémie, Pazgier Marzena, Finzi Andrés, Munro James B
Department of Microbiology, University of Massachusetts Chan Medical School, Worcester, MA, USA.
Centre de Recherche du CHUM, Montréal, Québec, Canada.
bioRxiv. 2024 Aug 22:2024.08.22.609179. doi: 10.1101/2024.08.22.609179.
The HIV-1 envelope glycoprotein (Env) is expressed at the surface of infected cells and as such can be targeted by non-neutralizing antibodies (nnAbs) that mediate antibody-dependent cellular cytotoxicity (ADCC). Previous single-molecule Förster resonance energy transfer (smFRET) studies demonstrated that Env from clinical isolates predominantly adopt a "closed" conformation (State 1), which is resistant to nnAbs. After interacting with the cellular receptor CD4, the conformational equilibrium of Env shifts toward States 2 and 3, exposing the coreceptor binding site (CoRBS) and permitting binding of antibodies targeting this site. We showed that the binding of anti-CoRBS Abs enables the engagement of other nnAbs that target the cluster A epitopes on Env. Anti-cluster A nnAbs stabilize an asymmetric Env conformation, State 2A, and have potent ADCC activity. CRF01_AE strains were suggested to be intrinsically susceptible to ADCC mediated by nnAbs. This may be due to the presence of a histidine at position 375, known to shift Env towards more "open" conformations. In this work, through adaptation of an established smFRET imaging approach, we report that the conformational dynamics of native, unliganded HIV-1 Env indicates frequent sampling of the State 2A conformation. This is in striking contrast with Envs from clades A and B, for example HIV-1, which do not transition to State 2A in the absence of ligands. These findings inform on the conformational dynamics of HIV-1 Env, which are relevant for structure-based design of both synthetic inhibitors of receptor binding, and enhancers of ADCC as therapeutic alternatives.
HIV-1包膜糖蛋白（Env）在受感染细胞表面表达，因此可被介导抗体依赖性细胞毒性（ADCC）的非中和抗体（nnAbs）靶向。先前的单分子荧光共振能量转移（smFRET）研究表明，临床分离株中的Env主要采用“封闭”构象（状态1），该构象对nnAbs具有抗性。与细胞受体CD4相互作用后，Env的构象平衡向状态2和状态3转变，暴露共受体结合位点（CoRBS），并允许靶向该位点的抗体结合。我们发现，抗CoRBS抗体的结合能够使其他靶向Env上A簇表位的nnAbs参与进来。抗A簇nnAbs稳定一种不对称的Env构象，即状态2A，并具有强大的ADCC活性。有研究表明，CRF01_AE毒株对nnAbs介导的ADCC具有内在敏感性。这可能是由于其375位存在组氨酸，已知该组氨酸会使Env向更“开放”的构象转变。在这项工作中，通过改进一种已建立的smFRET成像方法，我们报告天然的、未结合配体的HIV-1 Env的构象动力学表明其频繁采样状态2A构象。这与A和B亚型的Env形成鲜明对比，例如HIV-1，其在没有配体的情况下不会转变为状态2A。这些发现为HIV-1 Env的构象动力学提供了信息，这对于基于结构设计受体结合的合成抑制剂以及作为治疗选择的ADCC增强剂都具有重要意义。
