Evaluation of Antigen Productivity and Inactivation Kinetics of a Recombinant Foot-and-Mouth Disease SAT1 Vaccine Strain.

The Republic of Korea has implemented routine vaccination against foot-and-mouth disease virus (FMDV) in livestock using a bivalent vaccine comprising serotypes O and A following the massive FMD outbreak in 2010, while antigens for the remaining serotypes are maintained in overseas antigen banks. The recent geographic expansion of FMDV Southern African Territories 1 (SAT1) beyond Africa underscores the need for enhanced preparedness in previously unaffected regions. In this study, we evaluated the SAT1 BOT-R strain as a candidate vaccine seed for potential domestic vaccine production by optimizing antigen production conditions, assessing scalability, determining virus inactivation parameters, and examining immunogenicity in pigs. Optimal antigen yield was achieved at 20 h-24 h post infection with a multiplicity of infection of 0.005-0.01, with production remaining stable under mildly alkaline conditions. Antigen productivity was consistently maintained during scale-up from shake flasks to a bioreactor, yielding up to 9.5 μg/mL. Complete virus inactivation was achieved using binary ethylenimine at 2 mM for 24 h at 26 °C. Vaccines formulated from both flask- and bioreactor-derived antigens elicited comparable neutralizing antibody responses in pigs, reaching a median titer of 1:500 following booster immunization. Collectively, these findings demonstrate that the SAT1 BOT-R strain is a viable and scalable candidate for SAT1 antigen banking and future domestic vaccine production, providing a practical framework for strengthening national preparedness against potential incursions of FMDV SAT1.