Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, CA, USA.
Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA, USA.
Science. 2020 Dec 18;370(6523):1473-1479. doi: 10.1126/science.abe3255. Epub 2020 Nov 5.
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus enters host cells via an interaction between its Spike protein and the host cell receptor angiotensin-converting enzyme 2 (ACE2). By screening a yeast surface-displayed library of synthetic nanobody sequences, we developed nanobodies that disrupt the interaction between Spike and ACE2. Cryo-electron microscopy (cryo-EM) revealed that one nanobody, Nb6, binds Spike in a fully inactive conformation with its receptor binding domains locked into their inaccessible down state, incapable of binding ACE2. Affinity maturation and structure-guided design of multivalency yielded a trivalent nanobody, mNb6-tri, with femtomolar affinity for Spike and picomolar neutralization of SARS-CoV-2 infection. mNb6-tri retains function after aerosolization, lyophilization, and heat treatment, which enables aerosol-mediated delivery of this potent neutralizer directly to the airway epithelia.
严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）病毒通过其刺突蛋白与宿主细胞受体血管紧张素转换酶 2（ACE2）之间的相互作用进入宿主细胞。通过筛选酵母表面展示的合成纳米抗体文库，我们开发了能够破坏刺突蛋白和 ACE2 之间相互作用的纳米抗体。低温电子显微镜（cryo-EM）显示，一种纳米抗体 Nb6 以完全无活性的构象结合 Spike，其受体结合域锁定在不可接近的向下状态，无法结合 ACE2。亲和力成熟和结构导向设计的多价性产生了一种三价纳米抗体 mNb6-tri，对 Spike 的亲和力为飞摩尔级，对 SARS-CoV-2 感染的中和作用为皮摩尔级。mNb6-tri 在雾化、冻干和热处理后仍保持功能，这使得这种有效的中和剂能够通过气溶胶直接输送到气道上皮。
