Recombinant subunits of SARS-CoV-2 spike protein as vaccine candidates to elicit neutralizing antibodies

Objectives The spike protein has been reported as one of the most critical targets for vaccine design strategies against the SARS-CoV-2 infection. Hence, we have designed, produced, and evaluated the potential use of three truncated recombinant proteins derived from spike protein as vaccine candidates capable of neutralizing SARS-CoV-2 virus. Methods In silico tools were used to design spike-based subunit recombinant proteins (RBD (P-1), fusion peptide (P-2), and S1/S2 cleavage site (P-3)). These proteins were checked for their ability to be identified by the anti-SARS-CoV-2 antibodies by exposing them to COVID-19 serum samples. The proteins were also injected into mice and rabbit, and the antibody titers were measured for 390 days to assess their neutralization efficiency. Results The antibodies that existed in the serum of COVID-19 patients were identified by designed proteins. The anti-spike antibody titer was increased in the animals injected with recombinant proteins. The VNT results revealed that the produced antibodies could neutralize the cultured live virus. Conclusion Truncated subunit vaccines could also be considered as robust tools for effective vaccination against COVID-19. Using a combination of in silico, in vitro, and in vivo experiments, it was shown that the injection of spike-based truncated recombinant proteins could stimulate long-lasting and neutralizing antibody responses.