A recombinant spike protein subunit vaccine confers protective immunity against SARS-CoV-2 infection and transmission in hamsters

Multiple safe and effective vaccines that elicit immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are necessary to respond to the ongoing coronavirus disease 2019 (COVID-19) pandemic. Here, we developed a protein subunit vaccine composed of spike ectodomain protein (StriFK) plus a nitrogen bisphosphonate-modified zinc-aluminum hybrid adjuvant (FH002C). StriFK-FH002C generated substantially higher neutralizing antibody titers in mice, hamsters, and cynomolgus monkeys than those observed in plasma isolated from COVID-19 convalescent individuals. StriFK-FH002C also induced both T(H)1- and T(H)2-polarized helper T cell responses in mice. In hamsters, StriFK-FH002C immunization protected animals against SARS-CoV-2 challenge, as shown by the absence of virus-induced weight loss, fewer symptoms of disease, and reduced lung pathology. Vaccination of hamsters with StriFK-FH002C also reduced within-cage virus transmission to unvaccinated, cohoused hamsters. In summary, StriFK-FH002C represents an effective, protein subunit-based SARS-CoV-2 vaccine candidate.

Automated summary

This study developed a protein subunit vaccine consisting of spike ectodomain protein and a nitrogen bisphosphonate-modified zinc-aluminum hybrid adjuvant, which showed higher neutralizing antibody titers in animal models and induced T cell responses. The vaccine provided protection against SARS-CoV-2 challenge and reduced virus transmission among vaccinated and unvaccinated animals.