A new cage-like particle adjuvant enhances protection of Foot and Mouth Disease vaccine

Foot and Mouth Disease (FMD) is an acute viral disease that causes important economy losses. Vaccines with new low-cost adjuvants that stimulate protective immune responses are needed and can be assayed in a mouse model to predict their effectiveness in cattle. The Immunostimulant Particle Adjuvant -ISPA, also known as cage-like particles, consisting of lipid boxes of dipalmitoyl-phosphatidylcholine, cholesterol, sterylamine, alpha-tocopherol and QuilA saponin, was shown to enhance protection of a recombinant vaccine against Trypanosoma cruzi in a mouse model. Thus, in the present study, we examined the effects on the magnitude and type of immunity elicited in mice and cattle in response to a vaccine based on inactivated FMD virus (iFMDV) formulated with ISPA. It was demonstrated that iFMDV-ISPA induced protection in mice against challenge and elicited a specific antibody response in sera, characterized by a balanced Th1/Th2 profile. In cattle, the antibody titers reached corresponded to an Expected Percentage of Protection (EPP) higher than 80% The EPP estimates the likelihood that cattle would be protected against a challenge of 10.000 bovine infective doses after vaccination. Moreover, in comparison with the non-adjuvanted iFMDV vaccine, iFMDV-ISPA elicited an increased specific T response against the virus, including higher IFNγ+/CD8+ lymphocyte production in cattle. In this work, we report for first time that an inactivated FMDV serotype A vaccine adjuvanted with ISPA is capable of inducing protection against challenge in a murine model and of improving the specific immune responses against the virus in cattle.