No significant differences in the breadth of the foot-and-mouth disease serotype A vaccine induced antibody responses in cattle, using different adjuvants, mixed antigens and different routes of administration

Inactivated whole virus foot-and-mouth disease (FMD) vaccines are used worldwide for protection against FMD, but not all vaccines induce protection against all genetic variants of the same FMD virus serotype. The aim of this study is to investigate whether the "breadth" of the antibody response against different strains of the same FMD virus serotype in cattle could be improved by using a different adjuvant, a mix of antigens and/or different routes of administration. To this end, six groups of five cattle were vaccinated with different FMD virus serotype A strain vaccines formulated with Montanide ISA 206 VG adjuvant. Antibody responses for homologous and heterologous cross-reactivity against a panel of 10 different FMD virus serotype A strains were tested by a liquid-phase blocking ELISA. Results of cattle vaccinated with ISA 206 VG adjuvanted vaccine were compared with results obtained in a previous study using aluminium hydroxide-saponin adjuvant. No significant effect of adjuvant on the breadth of the antibody response was observed, neither for mixing of antigens nor for the route of administration (subcutaneous vs. intradermal). Comparison of antigen payload, however, increased both homologous and heterologous titres; a 10-fold higher antigen dose resulted in approximately four times higher titres against all tested strains. Our study shows that breadth of the antibody response depends mainly on the vaccine strain; we therefore propose that, for vaccine preparation, only FMD virus strains are selected that, among other important characteristics, will induce a wide antibody response to different field strains.