Evaluation of novel inactivated vaccine for type C foot-and-mouth disease in cattle and pigs.

Foot-and-mouth disease virus (FMDV) is the cause of an economically devastating disease in major cloven-hoofed livestock. Although type C foot-and-mouth disease (FMD) has not occurred anywhere worldwide since 2004, the antigen bank should be preserved in preparation for an unexpected outbreak. We therefore conducted experiments to develop inactivated vaccines that are safer and exhibit improved characteristics over existing vaccines. Our previous study showed that the replacement of the capsid-encoding gene (P1) from the vaccine strain O1 Manisa could be rescued successfully from the vaccine strains. In addition, novel point mutation in the 3C region in the virus genome, for induction of properties with low pathogenesis to create a safe vaccine, and 3B1B2 replacement, for differential diagnosis with the wild type virus, were performed. The modified FMD vaccine strain, C3 Resende-R, was shown to provide lower pathogenesis in young mice than the wild-type virus. To identify the immune responses after vaccination with 146S antigen (15 μg/mL/dose), we conducted a virus neutralization test using serum from pigs and cattle vaccinated with the inactivated vaccine. The neutralizing titers in the cattle were higher than those in the pigs and maintained mean antibody titers of around 1:100 until the end of the experiment. The vaccine showed protection capability of 16 PD50 against C3 Resende virus in the pigs. The replacement of the structural protein-coding gene for the new FMDV was a useful tool in the development of an effective vaccine candidate strain. This inactivated vaccine will be used for the establishment of a safe vaccine strain for the antigen bank.