Immunoglobulin fragment F(ab’)2 against RBD potently neutralizes SARS-CoV-2 in vitro

Pan, Xiaoyan; Zhou, Pengfei; Fan, Tiejiong; Wu, Yan; Zhang, Jing; Shi, Xiaoyue; Shang, Weijuan; Fang, Lijuan; Jiang, Xiaming; Shi, Jian; Sun, Yuan; Zhao, Shaojuan; Gong, Rui; Chen, Ze; Xiao, Gengfu

COVID-19 caused by the emerging human coronavirus, SARS-CoV-2, has become a global pandemic, leading a serious threat to human health. So far, there is none vaccines or specific antiviral drugs approved for that. Therapeutic antibodies for SARS-CoV-2, was obtained from hyper immune equine plasma in this study. Herein, SARS-CoV-2 RBD with gram level were obtained through Chinese hamster ovary cells high-density fermentation. The binding of RBD to SARS-CoV-2 receptor, human ACE2, was verified and the efficacy of RBD in vivo was tested on mice and then on horses. As a result, RBD triggered high-titer neutralizing antibodies in vivo, and immunoglobulin fragment F(ab’)2 was prepared from horse antisera through removing Fc. Neutralization test demonstrated that RBD-specific F(ab’)2 inhibited SARS-CoV-2 with EC50 at 0.07 μg/ml, showing a potent inhibitory effect on SARS-CoV-2. These results highlights as RBD-specific F(ab’)2 as therapeutic candidate for SARS-CoV-2.