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

Abstract

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 (P1), fusion peptide (P2), and S1/S2 cleavage site (P3)). 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.