Cross-protection Study Of COVID-19 Antibodies And Vaccine Against Pangolin-origin Coronavirus GX/P2V/2017

Emerging and re-emerging infectious diseases pose a serious threat to global human health,economy and security.In 2019,severe acute respiratory syndrome coronavirus 2(SARS-Co V-2)was first identified and isolated in Wuhan,China,and coronavirus disease 2019(COVID-19)has been pandemic for two years.As of March 25,2022,the World Health Organization(WHO)has reported approximately 476 million confirmed cases of COVID-19,with approximately 6.1 million deaths.COVID-19 is still spreading and mutating globally,and the emergence of mutant strains and complex pathogenic mechanisms make the development of vaccines and related drugs challenging.The natural and intermediate hosts of SARS-Co V-2 are currently unknown.Since the COVID-19 outbreak,a research team has identified and isolated two types of viruses highly homologous to SARS-Co V-2 in smuggled pangolins: GX/P2V/2017 and GD/1/2019,both of which recognize the human angiotensinconverting enzyme 2(ACE2)receptor.It has been shown that their pseudoviruses can infect cell lines stably transduced with human ACE2,suggesting that GX/P2V/2017 is at risk of infecting humans as well as other animals,and thus requires not only continuous monitoring of GX/P2V/2017 in the population and animals,but also rapid screening for antibodies and vaccines that are cross-protective against a possible pandemic of GX/P2V/2017 in the population or in animals.Subsequently,we carried out a cross-protection study on GX/P2V/2017 with 50 monoclonal antibodies targeting the receptor-binding domain(RBD)of SARS-Co V-2,and screened several monoclonal antibodies(such as S309,S2E12 and COVA1-16)with potent neutralizing ability against GX/P2V/2017.We also resolved the crystal structures of GX/P2V/2017 RBD complexed with monoclonal antibodies P2C-1F11(2.8?)and S309(3.3?),and elucidated the specific molecular mechanisms.We further evaluated the neutralization effect of the sera of the SARS-Co V-2recovered patients and the subunit vaccine ZF2001? vaccinated against SARS-Co V-2 and GX/P2V/2017 pseudovirus,and the results showed that the sera of the SARS-Co V-2 recovered patients and the subunit vaccine ZF2001? vaccinee can inhibit the entry of SARS-Co V-2 and GX/P2V/2017 pseudoviruses into cells,but the neutralization effect against GX/P2V/2017 was weaker compared with that of SARS-Co V-2.In conclusion,some monoclonal antibodies were identified as holding the better cross-protection ability against GX/P2V/2017 and triple-immunization vaccine recipients produced higher titers of cross-neutralizing antibodies than the second-exempt vaccine recipients.SARS-Co V-2 seriously threatens the health of humans and other mammals with a wide range of potential hosts,including humans,fur animals,and many wild animals.GX/P2V/2017 is highly homologous to SARS-Co V-2,and the Q498 H mutation in the SARS-Co V-2 spike protein(S)induces the binding of SARS-Co V-2 RBD to mouse ACE2,GX/P2V/2017 can bind to mouse ACE2,so mice may be potential hosts of GX/P2V/2017.Since rodents represented by mice live closely with humans,this may increase the spread of the virus risk and scope.Our study further found that GX/P2V/2017 can infect cell lines expressing ACE2 in macaque and mouse,and established a model of GX/P2V/2017 infection in mice,the results showed that the mice could be infected by GX/P2V/2017 with the effective virus replication and pathological damage in the lungs,and we also evaluated the protective effect of the subunit vaccine ZF2001? on the prevention of GX/P2V/2017 infection in mice,and the results showed that it could effectively prevent BALB/ c mouse from GX/P2V/2017 with infection in the lung tissue.This study also laid the foundation for the establishment of animal models for pan-coronavirus and the development of vaccines.Since the SARS-Co V-2 pandemic,its many mutant strains have emerged.WHO classified the mutant strains into Variant of concern(VOC)and Variant of interest(VOI)based on their degree of mutation,infectivity,virulence,and their impact on vaccine.Our study showed that the three VOC and their mutant pseudoviruses have enhanced infectivity to most of 293 T cells expressing ACE2 receptors of different species,especially A520 S mutation.We explained their enhanced infectivity by SPR as well as by the crystal structure of the Gamma-A520 S RBD and human ACE2 complex,where the S protein mutated at the A520 S locus has more standing(up)RBDs and interacts more readily with the receptor to trigger infection.Therefore,we should always pay attention to the mutation of the currently prevalent SARS-Co V-2 variants and to the infectious and antigenic changes brought about by possible high-frequency RBD mutations,and the results shed light on the prevention and control of the outbreaks of other coronaviruses in future.