Human monoclonal antibodies block the binding of SARS-CoV-2 spike protein to angiotensin converting enzyme 2 receptor

Lilin Ye; Xiangyu Chen; Ren Li; Zhiwei Pan; Chunfeng Qian; Yang Yang; Renrong You; Jing Zhao; Leiqong Gao; Zhirong Li; Qizhao Huang; Lifan Xu; Jianfang Tang; Qin Tian; Wei Yao; Li Hu; Xiaofeng Yan; Xinyuan Zhou; Pinghuang Liu; Yuzhang Wu; Kai Deng; Zheng Zhang; Yaokai Chen; Zhaohui Qian

The copyright holder for this preprint (which was not peer-reviewed) is . https://doi. org/10.1101 org/10. /2020 human! angiotensin^converting! enzyme! 2! (hACE2),! shared! by! both! SARS^CoV! and! SARS^CoV^2,! S! protein! undergoes! dramatic! conformational! changes! to! expose! the! RBD! and! key! residues! for! receptor! binding.! S! protein! is! metastable,! and! binding! of! RBD! to! hACE2! receptor! likely! leads! to! the! shedding! of! S1! protein! from! S2! protein,! thus! promoting! S2^mediated! virus^host! membrane! fusion! and! virus! entry 16^18 .! Given! the! critical! role! of! the! RBD! in! initiating! invasion! of! SARS^CoV^2! into! host! cells,! it! becomes! a! vulnerable! target! for! neutralizing! antibodies.! Thus! far,! the! human! mAbs! specifically!target!the!SARS^CoV^2!RBD^hACE2!interaction!have!not!been!reported,! and! a! monoclonal! antibody! targeting! S1! made! from! immunized! transgenic! mice! expressing! human! Ig! variable! heavy! and! light! chains! has! been! recently! shown! to! neutralize! both! SARS^CoV^2! and! SARS^CoV! infection,! but! by! an! unknown! mechanism!that!is!independent!of!the!blockade!of!RBD^hACE2!interaction 19 .! Prior!to!cloning!SARS^CoV^2!RBD!specific!human!mAbs,!we!first!examined!whether! patients! recently! recovered! from! COVID^19! had! mounted! anti^SARS^CoV^2! S1! protein! IgG! antibodies! in! sera.! Among! 26! recovered! COVID^19! patients,! we! found! that! the! majority! of! these! recruited! patients! were! able! to! produce! high! titers! of! SARS^CoV^2!S1^specific!IgG!antibodies!and!only!3!patients!mounted!relatively!lower! anti^S1! IgG! responses,! by! enzyme^linked! immunosorbent! assay! (ELISA)! ( Fig.! 1a) .! Consistently,! we! also! found! that! SARS^CoV^2! RBD! specific! IgG! antibodies! were! present! in! sera! of! all! patients! by! ELISA! (Fig.! 1b) .! Next,! we! sought! to! investigate! whether! RBD^specific! antibodies! in! patient! serum! can! block! the! binding! of! SARS^CoV^2!RBD!to!hACE2.!To!this!end,!we!set!up!an!ELISA^based!inhibition!assay! to!examine!the!blocking!function!of!these!antibodies.!We!noted!that!there!were!only!3! out!of!26!patients!showed!effective!blockade!of!SARS^CoV^2!RBD!binding!to!hACE2! ( Fig.!1c) .!Taken!together,!these!results!suggested!that!while!all!recovered!COVID^19! patients! can! generate! anti^S1! and! anti^RBD! antibodies,! there! were! only! a! small! fraction! of! these! antibodies! can! block! the! binding! of! RBD! to! hACE2! receptor.! This! observation! may! be! explained! by! transient! and! dynamic! perfusion! conformational! All rights reserved. No reuse allowed without permission. the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.