Stable Immune Response Induced by Intradermal DNA Vaccination by a Novel Needleless Pyro-Drive Jet Injector

DNA vaccination can be applied to the treatment of various infectious diseases and cancers; however, technical difficulties have hindered the development of an effective delivery method. The efficacy of a DNA vaccine depends on optimal antigen expression by the injected plasmid DNA. The pyro-drive jet injector (PJI) is a novel system that allows for adjustment of injection depth and may, thus, provide a targeted delivery approach for various therapeutic or preventative compounds. Herein, we investigated its potential for use in delivering DNA vaccines. This study evaluated the optimal ignition powder dosage, as well as its delivery effectiveness in both rat and mouse models, while comparing the results of the PJI with that of a needle syringe delivery system. We found that the PJI effectively delivered plasmid DNA to intradermal regions in both rats and mice. Further, it efficiently transfected plasmid DNA directly into the nuclei, resulting in higher protein expression than that achieved via needle syringe injection. Moreover, results from animal ovalbumin (OVA) antigen induction models revealed that animals receiving OVA expression plasmids (pOVA) via PJI exhibited dose-dependent (10 μg, 60 μg, and 120 μg) production of anti-OVA antibodies; while only low titers (< 1/100) of OVA antibodies were detected when 120 μg of pOVA was injected via needle syringe. Thus, PJI is an effective, novel method for delivery of plasmid DNA into epidermal and dermal cells suggesting its promise as a tool for DNA vaccination.