A Translatable Subunit Nanovaccine for COVID-19

In order to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in the world, we formulate S1 subunit of the virus with two types of adjuvants, amphiphilic adjuvant monophosphoryl lipid A (MPLA) for Toll-like receptor 4 (TLR4) and CpG ODN for TLR9, into cationic multifunctional liposomes to produce a potent, safer, and translatable nanovaccine. The results show that the nanovaccine can efficiently elicit humoral immune response in mice. The sera from the vaccinated mice significantly inhibit SARS-CoV-2 to infect Vero cells. Moreover, relatively to the free S1 with traditional Alum adjuvant, the nanovaccine can elicit strong T cell immunity by activating both CD4+ and CD8+ cells, which may play critical roles in eliminating viral load in patients. Most importantly, the nanovaccine can elicit strong IgA antibody, providing potential mucosal protection to host. Altogether, this study offers a translatable design for a potent subunit SARS-CoV-2 nanovaccine.