Host-cell entry of the highly pathogenic rabies virus (RABV) is mediated by glycoprotein (G) spikes, which also comprise the primary target for the humoral immune response. RABV glycoprotein (RABV-G) displays several antigenic sites that are targeted by neutralizing monoclonal antibodies (mAbs). In this study, we determined the epitope of a potently neutralizing human mAb, CR57, which we engineered into a diabody format to facilitate crystallization. We report the crystal structure of the CR57 diabody alone at 2.38 Å resolution, and in complex with RABV-G domain III at 2.70 Å resolution. The CR57−RABV-G structure reveals critical interactions at the antigen interface, which target the conserved “KLCGVL” peptide and residues proximal to it on RABV-G. Structural analysis combined with a cell-cell fusion assay demonstrates that CR57 effectively inhibits RABV-G-mediated fusion by obstructing the fusogenic transitions of the spike protein. Altogether, this investigation provides a structural perspective on RABV inhibition by a potently neutralizing human antibody.

中文翻译：

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通过工程抗体支架揭示狂犬病病毒中和的结构见解


高致病性狂犬病病毒 （RABV） 的宿主细胞进入是由糖蛋白 （G） 刺突介导的，糖蛋白 （G） 刺突也构成了体液免疫反应的主要靶标。RABV 糖蛋白 （RABV-G） 显示几个抗原位点，这些位点被中和单克隆抗体 （mAb） 靶向。在这项研究中，我们确定了一种有效中和人 mAb CR57 的表位，并将其设计成 diabody 形式以促进结晶。我们以 2.38 Å 的分辨率单独报道了 CR57 双体的晶体结构，并以 2.70 Å 的分辨率报道了与 RABV-G 结构域 III 的复合物的晶体结构。CR57−RABV-G 结构揭示了抗原界面的关键相互作用，这些相互作用靶向 RABV-G 上保守的“KLCGVL”肽及其近端的残基。结构分析结合细胞间融合测定表明，CR57 通过阻断刺突蛋白的融合转变，有效抑制 RABV-G 介导的融合。总而言之，这项研究为有效中和人类抗体抑制 RABV 提供了结构视角。