Chitosan-based systems for intranasal immunization against foot-and-mouth disease

Inactivated conventional vaccines against foot-and-mouth disease (FMD) are used routinely in endemic countries and are effective against clinical disease. Increased systemic IgG levels can be obtained with these vaccines whereas local response at the mucosal sites where the virus primarily enters the organism and replicates remains very limited. The aim of this study was to develop a safe, non-invasive and antigen compatible system for mucosal delivery of the FMD antigen which induces both the systemic and local immunity. Gel formulations were prepared using different types of chitosan at different concentrations and were incorporated with the whole inactivated FMD virion. The immune responses in guinea pigs were determined following intranasal administration. Chitosan-based FMD vaccine formulations have been shown to induce FMD antigen-specific serum IgG and nasal IgA levels, the latter response being significantly stronger as compared to that obtained following subcutaneous administration of the FMD antigen in Freund's incomplete adjuvant. Our results suggest that intranasal immunization with inactivated FMD virion delivered in the presence of chitosan is very promising, inducing both systemic and local immune responses.