Since the emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), various vaccines are being developed, with most vaccine candidates focusing on the viral spike protein. Here, we developed a previously unknown subunit vaccine comprising the receptor binding domain (RBD) of the spike protein fused with the tetanus toxoid epitope P2 (RBD-P2) and tested its efficacy in rodents and nonhuman primates (NHPs). We also investigated whether the SARS-CoV-2 nucleocapsid protein (N) could increase vaccine efficacy. Immunization with N and RBD-P2 (RBDP2/N) + alum increased T cell responses in mice and neutralizing antibody levels in rats compared with those obtained using RBD-P2 + alum. Furthermore, in NHPs, RBD-P2/N + alum induced slightly faster SARS-CoV-2 clearance than that induced by RBD-P2 + alum, albeit without statistical significance. Our study supports further development of RBD-P2 as a vaccine candidate against SARS-CoV-2. Also, it provides insights regarding the use of N in protein-based vaccines against SARS-CoV-2.
Bibliographical noteFunding Information:
This work was supported by grants from RIGHT and SK Bioscience (grant nos. M-2020-D0731-0002 and M-2020-D0732-0003), as well as by the Ministry of Science and ICT and the Korea Research Institute of Bioscience (PRM1752011), Bio-industrial Core Technology Development Project from the Ministry of Trade, Industry, and Energy (20013101) and Biotechnology (KRIBB) Research Initiative Program (KGM4572013).
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