Bilayer Films for Mucosal (Genetic) Immunization via the Buccal Route in Rabbits

Purpose. The oral buccal mucosa may be an ideal site for mucosal immunization, allowing for the needle-free administration of cost-effective vaccines. A novel mucoadhesive bilayer film was developed to test the feasibility of this route of immunization in rabbits. Methods. Bilayer films were developed using different ratios of Noveon and Eudragit S-100 as the mucoadhesive layer and a pharmaceutical wax as the impermeable backing layer. Optimal 3/8-inch films were post-loaded with 100 μg of plasmid DNA (CMV-β-gal) or β-galactosidase protein. The in vitro release rates and stability of the postloaded antigens were determined. The films were applied to the buccal pouch of rabbits on days 0, 7, and 14, and the humoral and splenocyte proliferative immune responses to β-gal were determined through day 28 and compared to those responses after conventional subcutaneous injection of adjuvanted protein. Results. The weight ratio of Noveon and Eudragit S-100 had a significant effect on adhesion time of bilayer films. Postloaded plasmid DNA and β-gal remained stable after being released from bilayer films (release of ∼60-80% in 2 h for both). Buccal immunization using novel bilayer films (109 ± 6-μm thickness) containing plasmid DNA led to comparable antigen-specific IgG titer to that of subcutaneous protein injection. All rabbits immunized with plasmid DNA via the buccal route but none by the subcutaneous route with protein antigen demonstrated splenocyte proliferative immune responses. Conclusion. The feasibility of buccal (genetic) immunization with these novel bilayer films was demonstrated.