An oral vaccine for SARS-CoV-2 RBD mRNA-bovine milk-derived exosomes induces a neutralizing antibody response in vivo

The severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) that causes the coronavirus disease 2019 (COVID-19) has presented numerous challenges to global health. The vaccines, including lipid-based nanoparticle mRNA, inactivated virus and recombined protein, have been used to prevent SARS-CoV-2 infections in clinics and are immensely helpful against the epidemic. Here, we first present an oral mRNA vaccine based on bovine milk-derived exosomes (milk-exos), which encodes the SARS-CoV-2 receptor binding domain (RBD) as an immunogen. The results indicated that RBD mRNA delivered by milk-derived exosomes can produce secreted RBD peptide in 293 cells in vitro and stimulated neutralizing antibodies against RBD in mice. These results indicated that bovine milk-derived exosome-based mRNA vaccine could serve as a new strategy for preventing SARS-CoV-2 infection. Meanwhile, it also can work as a new oral delivery system for mRNA. One Sentence Summary Oral SARS-CoV-2 mRNA vaccine based on bovine milk-derived exosomes can stimulate neutralizing antibodies in mice.