Evaluation of an In-House Developed Foot-and-Mouth Disease Virus SAT 3 Vaccine Strain Based on Antigen Productivity and Inactivation Kinetics for Commercial Feasibility

Background: In the Republic of Korea, a bivalent foot-and-mouth disease (FMD) vaccine covering serotypes O and A is administered to livestock, while antigens for the other serotypes are stockpiled in overseas antigen banks. To achieve self-reliance in FMD vaccine production, various vaccine strains have been developed using in-house technology. Although SAT 3 has historically been confined largely to Africa, preparedness against this serotype remains necessary, as the possibility of its introduction into Korea cannot be completely excluded. Methods: In this regard, we evaluated the commercial potential of the SAT 3 ZIM-R vaccine strain by assessing antigen productivity, scalability, inactivation kinetics, and immunogenicity. Results: Supplementation with 3 mM Ca2+ markedly increased antigen yield compared with that obtained in the absence of calcium. Further optimization showed that antigen yield was highest at pH 8.0–8.5. During scale-up, antigen yield was maintained at 9.2–9.8 μg/mL in flask cultures and remained high at approximately 7.8 μg/mL in a bioreactor, demonstrating robust scalability. Treatment with 2 mM binary ethylenimine at 26 °C achieved complete inactivation within 24 h. Vaccines formulated with the SAT 3 ZIM-R antigen produced either in flasks or in a bioreactor induced comparable neutralizing antibody responses in pigs following both the primary and booster immunizations. Conclusions: Collectively, these findings indicate that SAT 3 ZIM-R is a promising vaccine candidate for large-scale vaccine antigen production and the future establishment of a domestic FMD antigen bank in Korea.