Recombinant SARS-CoV-2 spike S1-Fc fusion protein induced high levels of neutralizing responses in nonhuman primates
Wenlin Ren, Hunter Sun, George F. Gao, Mantang Chen, Sean X. Sun, Rongqing Zhao, Guang Gao, Yalin Hu, Gan Zhao, Yuxin Chen, Xia Jin, Fang Feng, Jinggong Chen, Qi Wang, Sitao Gong, Wen Gao, Yufei Sun, Junchi Su, Ailiang He, Xin Cheng, Min Li, Chenxi Xia, Maohua Li, Le Sun
Abstract
The COVID-19 outbreak has become a global pandemic responsible for over 2,000,000 confirmed cases and over 126,000 deaths worldwide. In this study, we examined the immunogenicity of CHO-expressed recombinant SARS-CoV-2 S1-Fc fusion protein in mice, rabbits, and monkeys as a potential candidate for a COVID-19 vaccine. We demonstrate that the S1-Fc fusion protein is extremely immunogenic, as evidenced by strong antibody titers observed by day 7. Strong virus neutralizing activity was observed on day 14 in rabbits immunized with the S1-Fc fusion protein using a pseudovirus neutralization assay. Most importantly, in <20 days and three injections of the S1-Fc fusion protein, two monkeys developed higher virus neutralizing titers than a recovered COVID-19 patient in a live SARS-CoV-2 infection assay. Our data strongly suggests that the CHO-expressed SARS-CoV-2 S1-Fc recombinant protein could be a strong candidate for vaccine development against COVID-19.