Identification And Characterization Of Broad Neutralizing Antibodies Against SARS-CoV-2 Omicron Variants

Background:Novel coronavirus pneumonia(COVID-19)is caused by a novel coronavirus(SARS-CoV-2),SARS-CoV-2 is the third highly pathogenic human coronavirus since the twentieth century,which is highly infectious and has spread widely worldwide.Currently causing more than 700 million confirmed infections and over 6.6 million deaths,with serious impact for human health,socio-economic and national security.Development of neutralizing antibodies against SARS-CoV-2 are an important tool for the treatment and prevention of COVID-19,however,with the emergence of multiple SARS-CoV-2 variants,the neutralizing efficacy of most neutralizing antibodies has significantly decreased.The development of a "broad-spectrum"neutralizing antibodies or COVID-19 vaccine that avoids virus escape is an important issue that needs to be addressed.Objective:On the basis of the monoclonal antibodies(mAbs)constructed from COVID-19 convalescents and vaccine recipients earlier,77 mAbs with neutralizing activity against the prototype SARS-CoV-2 were screened,and analyzed for antiviral activity with the aim of identifying mAbs with broad-spectrum neutralizing activity against the Omicron subvariants,which is expected to provide candidates for antibody therapy against COVID-19 and future vaccine design.Methods:The subject of this study is seventy-seven prototype SARS-CoV-2 neutralizing antibodies constructed from COVID-19 convalescents and vaccine recipients earlier.These antibodies were reacted with Omicron variants antigens or pseudotyped viruses,and their binding capacity,epitope distribution,ACE2 competition,binding affinity and neutralizing activity were measured by ELISA,BLI and pseudovirus neutralization assays to identify antibodies with broad-spectrum neutralizing activity against Omicron subvariants and the major four Variants of Concern(VOCs).Results:1.29.5%(77/261)of the monoclonal antibodies we constructed had neutralizing activity against prototype SARS-C oV-2.Of this,96.1%(74/77)of the antibodies bound to RBD and 72.7%(56/77)competed for ACE2 binding.2.Only a proportion of prototype SARS-CoV-2 neutralizing antibodies were able to cross-neutralize the Omicron subvariants,of which 27 for BA.1(35.1%),35 for BA.2(45.5%),22 for BA.3(28.6%),23 for BA.4/5(29.9%),32 for BA.2.75(41.6%),16 for BF.7(20.8%),and 7 for BQ.1(9.1%).3.Candidate neutralizing antibodies showed strong binding activity against all Omicron subvariants,which showed relatively weak binding activity against BA.1.4.Candidate neutralizing antibodies showed strong binding affinity for SARS-CoV-2 and BA.2,which showed relatively weak binding affinity against BA.1,with SCM11-12 showing the best binding affinity.5.In combination with antibody neutralization profile analysis,we identified two neutralizing antibodies(VSM12-37 and SCM15-45)of candidate neutralizing antibodies,they showed broad neutralizing activity against the Omicron variants pseudo virus tested in this study,as well as against representative variants B.1.1.7,B.1.351,P.1,and B.1.617.2.Conclusions:1.We found that Omicron BA.1,BA.2,BA.3,BA.4/5,BA.2.75,BF.7 and BQ.1 subvariants showed different escapes profiles against mAbs induced by prototype SARS-CoV-2 infection and vaccination,especially BF.7 and BQ.1,which have the strongest neutralizing resistance.2.The candidate neutralizing antibodies have the ability to broadly neutralize the Omicron variants,they both target the SARS-CoV-2 S RBD and compete for ACE2 binding,suggesting that the conserved ACE2 binding site on the RBD could be used as targets for SARS-CoV-2 vaccine development and therapy.