Further studies on the early protective responses of pigs following immunisation with high potency foot and mouth disease vaccine.

ABSTRACT

The ability of an emergency oil adjuvanted foot-and-mouth disease (FMD) vaccine to elicit early protective immunity in pigs against direct contact homologous challenge was examined. All vaccinates showed reduced viraemia and shedding of FMDV, and certain animals were protected, showing no clinical signs. IL-6, IL-8 and IL-12 were consistently detected in challenged animals that had been vaccinated. Other cytokines--IL-1, IL-2, TNF, TGF and interferons--were not detected. This demonstrates that the vaccine did not induce a systemic inflammatory response, nor a systemic elevation of T lymphocyte activity. Although the IL-6 and IL-8 did not relate to protection, IL-12 production was highest in the protected vaccinated pigs. Thus, the induction of monocytic cell activity, demonstrable by the production of IL-6, IL-8 and IL-12, appears to play a critical role in FMDV emergency vaccine induction of the innate immune defences which relate to early protection against FMD. The possible modes of defence in which such cytokine activity would be involved are discussed.