開發新冠病毒中和性抗體雞尾酒療法

Abstract

已肆虐全球兩年的SARS-CoV-2病毒，其表面的棘蛋白在病毒入侵宿主細胞上扮演重要角色，尤其是棘蛋白上的受體結合區域 (receptor-binding domain, RBD) 是病毒與人類細胞的血管收縮素轉化酶2 (angiotensin-converting enzyme 2, ACE2) 結合的位置，因此RBD成為中和性抗體的主要標的。但因為RBD為病毒的高度變異區，這類抗體遇到新的突變株時，容易發生免疫逃脫的現象。故本研究以RBD作為標的，開發出六個對於RBD以及棘蛋白都具有高度辨識力的抗體，分別是2A11、2D5、2F9、3B3、3D10和3F4。針對病毒各個變異株進行中和性測試，2F9和3B3對於SARS-CoV-2武漢株具有中和能力；2F9、3B3、3D10和3F4對於Alpha變異株具有中和能力；2A11、2D5、2F9、3B3和3D10則對於Delta變異株具有中和能力；3F4則是唯一對於Omicron BA.1突變株具有中和能力的抗體。本研究使用丙胺酸定點突變的方式，鑑定出單株抗體對RBD的確切結合位。由3F4或2A11以及S2-4A或S2-8D所組成的抗體雞尾酒，對於Omicron BA.2突變株具有加乘成的中和能力。本研究顯示搭配使用RBD抗體與S2 抗體的抗體雞尾酒療法，具有潛力開發成對付新冠病毒感染之預防與治療藥物。

The spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARA-CoV-2) is an important viral surface protein for receptor binding and virus-host cell membrane fusion. The receptor-binding domain (RBD) of the S1 subunit of S protein mediates viral binding to human angiotensin-converting enzyme 2 (ACE2). Thus, RBD is considered as the main target of the neutralizing antibodies. Recently, many SARS-CoV-2 variants appear sequence mutations at RBD. Therefore, antibody cocktail is believed to be a better therapeutics for preventing the SARS-CoV-2 immune escape. In the study, monoclonal antibodies (mAbs) 2A11, 2D5, 2F9, 3B3, 3D10 and 3F4 show great specificity to SARS-CoV-2 RBD and S protein. 2F9 and 3B3 exhibit neutralizing activities against SARS-CoV-2 Wuhan strain. 2F9, 3B3, 3D10, and 3F4 exhibit neutralizing activities against SARS-CoV-2 Alpha variant. 2A11, 2D5, 2F9, 3B3, and 3D10 exhibit neutralizing activities against SARS-CoV-2 Delta variant. Only 3F4 exhibits neutralizing activities against SARS-CoV-2 Omicron sublineage BA.1. The binding epitopes of these RBD-specific mAbs were determined by using the alanine-scanning mutagenesis. The antibody cocktail, composed of the RBD-specific mAb 3F4 or 2A11 and the S2-specific mAb S2-4A or S2-8D, exhibits synergistic neutralizing activities against SARS-CoV-2 Omicron sublineage BA.2. The results suggest that the combination of the RBD-specific mAb and the S2-specific mAb are potential candidates for development as prophylactic or therapeutic agents against SARS-CoV-2 infection.