SARS⁃CoV⁃2免疫逃逸NTD中和抗体的分子机制  

Molecular basis of SARS⁃CoV⁃2 immune evasion to NTD neutralizing antibodies

作　　者：洪琴 徐诗奇 王艳兴 张超[3] 黄忠 丛尧 HONG Qin;XU Shiqi;WANG Yanxing;ZHANG Chao;HUANG Zhong;CONG Yao(Shanghai Institute of Biochemistry and Cell Biology,Center for Excellence in Molecular Cell Science,Chinese Academy of Sciences,Shanghai 200031;University of Chinese Academy of Sciences,Beijing 100049;Shanghai Institute of Immunity and Infection,Chinese Academy of Sciences,Shanghai 200031,China)

机构地区：[1]中国科学院分子细胞科学卓越创新中心(生物化学与细胞生物学研究所),上海200031 [2]中国科学院大学,北京100049 [3]中国科学院上海免疫与感染研究所,上海200031

出　　处：《电子显微学报》2024年第3期329-338,共10页Journal of Chinese Electron Microscopy Society

基　　金：中国科学院战略性先导科技专项(Nos.XDB37040103,XDB29040300);国家重点研发计划(2020YFC0845900);国家自然科学基金资助项目(Nos.32130056,31872714);上海学术带头人计划(20XD1404200);欧盟“地平线2020”计划(No.101003589);中国科学院青年创新促进会与上海“启明星”计划(21QA1410000)[张超]。

摘　　要：针对严重急性呼吸综合征冠状病毒2(Severe acute respiratory syndrome coronavirus 2,SARS-CoV-2)中和抗体的开发,主要针对SARS-CoV-2表面的刺突(Spike,S)蛋白。大多数中和SARS-CoV-2的单克隆抗体(MAbs)可结合S蛋白的受体结合结构域(receptor-binding domain,RBD),从而阻断病毒与血管紧张素转化酶2(Angiotensin-converting enzyme 2,ACE2)的相互作用。作者早期通过SARS-CoV-2原型株S蛋白免疫小鼠,筛选得到S2G4,S2H5,S4D4,S5B84株与S蛋白氮末端结构域(N-terminal domain,NTD)不同表位结合的单克隆抗体,其中S2H5活病毒中和能力最强。本研究利用冷冻电镜技术解析了S2H5的抗原结合片段(Fab)结合SARS-CoV-2原型株S蛋白复合体的结构,共获得六种构象,其中S2H5 Fab结合在S蛋白的NTD上,结构模拟完整S2H5抗体结合S蛋白可以空间上阻碍S蛋白与ACE2相互作用,揭示了S2H5中和SARS-CoV-2原型株的结构基础。此外,作者应用假病毒中和实验,分析了上述四种抗体对SARS-CoV-2多种突变株的中和能力,显示了其突变株对NTD抗体的免疫逃逸,并从结构生物学角度对各突变株表现出的免疫逃逸提供了可能的解释。Neutralizing antibodies play an important role in the immunity against severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).The spike(S)protein on the surface of SARS-CoV-2 is the main target for neutralizing antibody development.Most monoclonal antibodies(MAbs)capable of neutralizing SARS-CoV-2 bind to the receptor-binding domain(RBD)of the S protein and thus are able to block binding of the virus to its host receptor,angiotensin-converting enzyme 2(ACE2).We earlyimmunized mice with the S protein of the SARS-CoV-2 wildtype strain and identified four neutralizing MAbs,namely S2G4,S2H5,S4D4 and S5B8,targeting different epitopes of N-terminal domain(NTD),among which S2H5 has the strongest neutralization ability against live WT SARS-COV-2.In this study,Cryo-EM was used to analyze the structure of SARS-CoV-2 S trimer in complex with the Fab of S2H5,and obtain six Cryo-EM maps,in which the S2H5 Fab was bound to the NTD of the S protein,and the structure was simulated binding of the intact S2H5 antibody to the S protein can sterically hinder the interaction of the S protein with ACE2,revealing the structural basis for S2H5 neutralization of the wildtype SARS-CoV-2.Moreover,by performing pseudovirus neutralization assays,we show that major SARS-CoV-2 variants significantly evade neutralization by the four NTD antibodies,in particular S2H5.Our work thus reveals the extensive immune evasion from NTD antibodies by SARS-CoV-2 variants and also provides a structural explanation for this phenomenon.

关 键 词：新型冠状病毒 刺突蛋白 中和抗体 冷冻电镜 

分 类 号：Q7[生物学—分子生物学] Q51Q336