Modulation of the antigen presentation activity in foot and mouth disease virus (FMDV) vaccines by two adjuvants: avridine and a water soluble fraction of Mycobacterium sp.

We have previously demonstrated that the presence of the antigen presenting cells (APC) is critical in the induction and maintenance of the immune response in animals infected or immunized with inactivated FMDV. The use of immunological adjuvants has been repeatedly shown to be essential for the improvement of the immunogenicity in FMDV vaccines. Specifically, we have previously shown that the addition of the synthetic lipoamide Avridine (AVR) or a water soluble fraction of Mycobacterium sp. (WSF) significantly increased the immune response and protection against FMDV challenge. Here, we study the effect of these adjuvants on the induction of APC activity in mice immunized with inactivated FMDV. Both adjuvants were able to induce a long lasting antibody response which correlates with an efficient APC activity. Experiments using sequential cell transfers showed that the presence of the APC activity is not related with the efficiency of keeping free antigen in the vaccinated host. Interestingly, APC from animals immunized with AVR as adjuvant elicited virus neutralizing antibodies, while those APC obtained from donors vaccinated using WSF as adjuvant (or just an oil emulsion) induced anti-FMDV detectable only by ELISA. The analysis of the antibody response to a well studied synthetic peptide raised evidences that indicate that this difference could be explained by a differential presentation of viral B epitopes when different adjuvants were used. These results suggest that the induction of APC should be considered as one of the critical factors in the process of improving the immunogenicity of experimental FMDV vaccines.