Full Protection in Pigs against FMDV Challenge following Single Dose of Synthetic Emergency FMD Vaccine

Introduction: The UBITh ® -VP1 synthetic peptide-based vaccine for FMDV O, formulated as a water-in-oil emulsion, was evaluated in an emergency application single dose efficacy trial by the National Institute of Animal Health in Taiwan. Two groups having six 8-12 week old pigs each were given single injections of either 2.0 ml or 1.0 ml of the UBITh ® -VP1 vaccine, by intramuscular injection. The animals were then challenged 28 days later according to the pig vaccine potency protocol described in the OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animals (2004), by injecting 10 5.0 TCID50 of FMDV O/TAW/97 into the heel bulb. Vaccine performance from an earlier 2 dose protocol was also characterized. Results: Following virus inoculation, none of the vaccinated pigs showed clinical signs over the 14-day observation period. In contrast, the 2 unvaccinated control animals developed signs of generalized FMD. No adverse effects were recorded among the pigs following vaccination throughout the pre-challenge period. Protection was not correlated to neutralizing antibodies. The 2 dose protocol indicated cellular immunity mediated by T lymphocytes secreting IFN-gamma as a correlate of immunity. Discussion: A safe and convenient-to-manufacture high potency emergency FMD vaccine demonstrating full protection against FMDVO1Taiwan in pigs has been developed. Given that the target antigen component for the vaccine was the G-H neutralizing epitope of VP1, the pigs were immunized by a marker vaccine. Vaccinates are therefore readily distinguished serologically from virus-infected counterparts.