LNP-formulated dbDNA vaccines elicit durable humoral and cellular immunity with distinct kinetics to mRNA in...

Nucleic acid vaccines offer rapid and flexible platforms for addressing infectious diseases, but achieving durable and balanced immunity remains a challenge. We evaluated a closed linear synthetic Doggybone DNA vaccine (dbDNA) encoding influenza A/California/07/2009 hemagglutinin across delivery platforms and preclinical models. In minipigs, dbDNA elicited comparable or stronger antibody and T cell responses than plasmid DNA when delivered by needle-free intradermal injection or intramuscular electroporation. Direct comparison of lipid nanoparticle (LNP)-formulated dbDNA with nucleoside-modified mRNA vaccines revealed platform- and species-specific immune profiles. In mice, mRNA vaccines induced higher antibody titers, whereas T cell responses were broadly comparable, though dose-response effects differed. In non-human primates (NHPs), both vaccines (delivered as a 20 μg dose) elicited robust antibody titers with different kinetics: mRNA responses declined shortly after peak, whereas dbDNA titers persisted. Additionally, dbDNA induced a higher proportion of functional antibodies and enhanced CD4⁺ and CD8⁺ T cell responses, with an immunostimulatory cytokine profile. These results demonstrate that LNP-formulated dbDNA elicits durable humoral and cellular immunity at low dose in NHPs, with distinct kinetics and functional profiles compared with mRNA vaccines.