Most existing vaccines, delivered by intramuscular injection (IM), are typically associated with stringent storage requirements under cold-chain distribution and professional administration by medical personnel and often result in the induction of weak mucosal immunity. In this context, we reported a microneedle (MN) patch to deliver chitosan oligosaccharide (COS)-encapsulated DNA vaccines (DNA@COS) encoding spike and nucleocapsid proteins of SARS-CoV-2 as a vaccination technology. Compared with IM immunization, intradermal administration via the MN-mediated DNA vaccine effectively induces a comparable level of neutralizing antibody against SARS-CoV-2 variants. Surprisingly, we found that MN-mediated intradermal immunization elicited superior systemic and mucosal T cell immunity with enhanced magnitude, polyfunctionality, and persistence. Importantly, the DNA@COS nanoparticle vaccine loaded in an MN patch can be stored at room temperature for at least 1 month without a significant decrease of its immunogenicity. Mechanically, our strategy enhanced dendritic cell maturation and antiviral immunity by activating the cGAS-STING-mediated IFN signaling pathway. In conclusion, this work provides valuable insights for the rapid development of an easy-to-administer and thermostable technology for mucosal vaccines.
Keywords: Chitosan oligosaccharide (COS); DNA vaccine; Microneedle; Mucosal immunity; SARS-CoV-2.