Murin Charles D, Julien Jean-Philippe, Sok Devin, Stanfield Robyn L, Khayat Reza, Cupo Albert, Moore John P, Burton Dennis R, Wilson Ian A, Ward Andrew B
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, USA International AIDS Vaccine Initiative Neutralizing Antibody Center and Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, California, USA Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, USA.
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, USA International AIDS Vaccine Initiative Neutralizing Antibody Center and Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, California, USA.
J Virol. 2014 Sep 1;88(17):10177-88. doi: 10.1128/JVI.01229-14. Epub 2014 Jun 25.
The neutralizing anti-HIV-1 antibody 2G12 is of particular interest due to the sterilizing protection it provides from viral challenge in animal models. 2G12 is a unique, domain-exchanged antibody that binds exclusively to conserved N-linked glycans that form the high-mannose patch on the gp120 outer domain centered on a glycan at position N332. Several glycans in and around the 2G12 epitope have been shown to interact with other potent, broadly neutralizing antibodies; therefore, this region constitutes a supersite of vulnerability on gp120. While crystal structures of 2G12 and 2G12 bound to high-mannose glycans have been solved, no structural information that describes the interaction of 2G12 with gp120 or the Env trimer is available. Here, we present a negative-stain single-particle electron microscopy reconstruction of 2G12 Fab2 in complex with a soluble, trimeric Env at ∼17-Å resolution that reveals the antibody's interaction with its native and fully glycosylated epitope. We also mapped relevant glycans in this epitope by fitting high-resolution crystal structures and by performing neutralization assays of glycan knockouts. In addition, a reconstruction at ∼26 Å of the ternary complex formed by 2G12 Fab2, soluble CD4, and Env indicates that 2G12 may block membrane fusion by induced steric hindrance upon primary receptor binding, thereby abrogating Env's interaction with coreceptor(s). These structures provide a basis for understanding 2G12 binding and neutralization, and our low-resolution model and glycan assignments provide a basis for higher-resolution studies to determine the molecular nature of the 2G12 epitope.
HIV-1 is a human virus that results in the deaths of millions of people around the world each year. While there are several effective therapeutics available to prolong life, a vaccine is the best long-term solution for curbing this global epidemic. Here, we present structural data that reveal the viral binding site of one of the first HIV-1-neutralizing antibodies isolated, 2G12, and provide a rationale for its effectiveness. These structures provide a basis for higher-resolution studies to determine the molecular nature of the 2G12 epitope, which will aid in vaccine design and antibody-based therapies.
中和性抗HIV-1抗体2G12因其在动物模型中能提供针对病毒攻击的绝育保护而备受关注。2G12是一种独特的、结构域交换抗体，它专门结合保守的N-连接聚糖，这些聚糖在以N332位聚糖为中心的gp120外结构域上形成高甘露糖斑块。2G12表位及其周围的几种聚糖已被证明与其他强效、广泛中和抗体相互作用；因此，该区域构成了gp120上的一个超级易损位点。虽然已解析出2G12与高甘露糖聚糖结合的晶体结构，但尚无描述2G12与gp120或Env三聚体相互作用的结构信息。在此，我们展示了2G12 Fab2与可溶性三聚体Env复合物的负染单颗粒电子显微镜重建结果，分辨率约为17 Å，揭示了该抗体与其天然且完全糖基化表位的相互作用。我们还通过拟合高分辨率晶体结构和进行聚糖敲除的中和试验，绘制了该表位中的相关聚糖。此外，2G12 Fab2、可溶性CD4和Env形成的三元复合物在约26 Å分辨率下的重建表明，2G12可能在主要受体结合时通过诱导空间位阻来阻断膜融合，从而消除Env与共受体的相互作用。这些结构为理解2G12的结合和中和作用提供了基础，我们的低分辨率模型和聚糖归属为更高分辨率研究确定2G12表位的分子性质提供了基础。
HIV-1是一种人类病毒，每年导致全球数百万人死亡。虽然有几种有效的治疗方法可延长生命，但疫苗是遏制这一全球流行病的最佳长期解决方案。在此，我们展示的结构数据揭示了最早分离出的HIV-1中和抗体之一2G12的病毒结合位点，并为其有效性提供了理论依据。这些结构为更高分辨率研究确定2G12表位的分子性质提供了基础，这将有助于疫苗设计和基于抗体的治疗。
