Induction of immunity using oral DNA vaccines expressing the measles virus nucleocapsid protein

In this study, we have examined the feasibility of immunisation against measles with plasmid DNA administered by the oral route. After the oral administration, in two 50 microg doses, of poly(DL-lactide-co-glycolide) (PLGA)-encapsulated DNA expressing measles virus nucleoprotein, increasing titres of N-specific serum IgG antibodies were observed in three of ten C3H/He mice over a period of three months. In comparison, oral vaccination of mice with a replication-defective recombinant adenovirus expressing the same transgene induced serum IgG in all animals tested. We also obtained preliminary indication of adjuvant-like activity of PLGA particles when coadministered intraperitoneally (i.p.) with naked plasmid DNA. These experiments demonstrate that oral delivery of either PLGA-encapsulated plasmid DNA or viral vectored DNA is capable of eliciting strong immune responses in mice. We propose that oral administration of biodegradable microparticles offers a novel strategy for future vaccine design for the safe delivery of DNA to mucosal surfaces.