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

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 LNP-formulated dbDNA with nucleoside-modified mRNA vaccines revealed platform- and species-specific immune profiles. In mice, mRNA induced higher antibody titers, whereas T cell responses were broadly comparable, though dose response effects differed. In non-human primates (NHP), both vaccines (delivered as a 20μg 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 to mRNA.