We investigated the influence of antigen entrapment in PLA nanoparticles on the immune responses obtained after transcutaneous immunization. OVA-loaded PLA nanoparticles were prepared using a double emulsion process. Following application onto bare skin of mice in vivo, fluorescence-labeled nanoparticles were detected in the duct of the hair follicles indicating that the nanoparticles can penetrate the skin barrier through the hair follicles. Although the OVA-loaded nanoparticles elicited lower antibody responses than those induced by OVA in aqueous solution they were more efficient in inducing cytokine responses. In vitro re-stimulation of cultured splenocytes with OVA elicited a little higher levels of IFN-gamma (difference statistically insignificant, p>0.05) and significantly higher levels of IL-2 (p<0.001) in mice immunized with OVA-loaded nanoparticles compared to those immunized with OVA in solution. In the presence of CT, the OVA-loaded nanoparticles induced significantly higher IFN-gamma and IL-2 than all other formulations. Transcutaneous administration of OVA encapsulated in the PLA nanoparticles exhibited priming efficacy to a challenging dose of OVA given via different route. These findings indicate the potential of nanoparticles to deliver antigens via the transcutaneous route and prime for antibody and strong cellular responses. The co-administration of an adjuvant such as CT had the added advantage of modulating the immune response, a desirable characteristic within the context of vaccination against intracellular versus extracellular pathogens.
2009 Elsevier B.V. All rights reserved.