Recombinant Fc-fusion vaccine of RBD induced protection against SARS-CoV-2 in non-human primate and mice

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) continues to infect people globally. The increased COVID-19 cases and no licensed vaccines highlight the need to develop safe and effective vaccines against SARS-CoV-2 infection. Multiple vaccines candidates are under pre-clinical or clinical trails with different strengths and weaknesses. Here we developed a pilot scale production of a recombinant subunit vaccine (RBD-Fc Vacc) with the Receptor Binding Domain of SARS-CoV-2 S protein fused with the Fc domain of human IgG1. RBD-Fc Vacc induced SARS-CoV-2 specific neutralizing antibodies in non-human primates and mice, and the antibodies induced in macaca fascicularis neutralized three divergent SARS-CoV2 strains, supporting broader neutralizing ability. Three times immunizations protected Macaca fascicularis (20ug or 40ug per dose) and mice (10ug or 20ug per dose) from SARS-CoV-2 infection respectively, including the protection against SARS-CoV-2 adapted virus MASCp6 which contains N501Y mutation, a key residue increasing binding affinity to human and murine ACE2. These data support clinical development of SARS-CoV-2 vaccines and provide a promising strategy to prevent different stains of SARS-CoV-2 infection. RBD-Fc Vacc is currently being assessed in randomized controlled phase 1/II human clinical trails