Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
Division of Virology, Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
Nat Commun. 2020 Sep 4;11(1):4420. doi: 10.1038/s41467-020-18174-5.
SARS-CoV-2 enters host cells through an interaction between the spike glycoprotein and the angiotensin converting enzyme 2 (ACE2) receptor. Directly preventing this interaction presents an attractive possibility for suppressing SARS-CoV-2 replication. Here, we report the isolation and characterization of an alpaca-derived single domain antibody fragment, Ty1, that specifically targets the receptor binding domain (RBD) of the SARS-CoV-2 spike, directly preventing ACE2 engagement. Ty1 binds the RBD with high affinity, occluding ACE2. A cryo-electron microscopy structure of the bound complex at 2.9 Å resolution reveals that Ty1 binds to an epitope on the RBD accessible in both the 'up' and 'down' conformations, sterically hindering RBD-ACE2 binding. While fusion to an Fc domain renders Ty1 extremely potent, Ty1 neutralizes SARS-CoV-2 spike pseudovirus as a 12.8 kDa nanobody, which can be expressed in high quantities in bacteria, presenting opportunities for manufacturing at scale. Ty1 is therefore an excellent candidate as an intervention against COVID-19.
SARS-CoV-2 通过刺突糖蛋白与血管紧张素转换酶 2（ACE2）受体之间的相互作用进入宿主细胞。直接阻止这种相互作用为抑制 SARS-CoV-2 复制提供了一个有吸引力的可能性。在这里，我们报告了一种从羊驼中分离出来的单域抗体片段 Ty1 的分离和特性，该片段专门针对 SARS-CoV-2 刺突的受体结合域（RBD），直接阻止 ACE2 的结合。Ty1 以高亲和力结合 RBD，阻断 ACE2 的结合。在 2.9Å分辨率下结合复合物的低温电子显微镜结构揭示了 Ty1 结合到 RBD 上的一个表位，该表位在“向上”和“向下”构象中都可及，从而阻碍 RBD-ACE2 结合。虽然与 Fc 结构域融合使 Ty1 具有极高的效力，但 Ty1 作为 12.8 kDa 的纳米抗体中和 SARS-CoV-2 刺突假病毒，该纳米抗体可以在细菌中大量表达，为大规模生产提供了机会。因此，Ty1 是对抗 COVID-19 的理想候选药物。
