Development and application of ELISA test system for assessing humoral immunity against SAT2 topotype XIV foot-and-mouth disease virus

Introduction . Foot-and-mouth disease (FMD) is a highly contagious, economically significant disease of cloven-hoofed animals, characterized by vesicular symptoms. There are seven known foot-and-mouth disease virus (FMDV) serotypes (A, O, C, SAT 1, SAT 2, SAT 3 and Asia 1), which immunologically differ from each other. Special attention has been recently paid to FMDV of SAT2/XIV topotype (South African Territories 2) due to its rapid spread. One of the key methods of FMD control is vaccination and assessment of the susceptible animal immune status. Objective . Development and testing of an enzyme-linked immunosorbent assay (ELISA) system based on the indirect liquid-phase blocking ELISA for the determination of antibodies to structural proteins of SAT2/XIV FMDV in order to evaluate the effectiveness of an FMD vaccine based on SAT-2/XIV/2023 FMDV antigen in the process of its production and subsequent use. Materials and methods . The test material included experimental serum samples collected from cattle, pigs and white mice. The developed ELISA test system for assessing the level of post-vaccination antibodies against SAT2/XIV FMDV was validated through comparative testing with commercial test-kits: Test-kit for the determination of SAT 2 FMDV antibodies (Federal Centre for Animal Health, Russia) and “Solid-phase competitive ELISA for antibodies specific to FMDV serotype SAT 2”(IZSLER & The Pirbright Institute, Italy/Great Britain). Results . The effectiveness of the proposed test system in detecting the induction of antibodies against SAT2/XIV FMDV was higher than that of other ELISA systems with the pronounced topotype specificity to the SAT2/VII FMD agent. Specific antibodies were detected in individual cattle on day 7 post vaccination. High diagnostic sensitivity (90%), specificity (98%) and accuracy (95%) ensured high degree of the ELISA results consistency with the known diagnostic status of the tested animals (k-criterion – 0.896). Conclusion . Thus, the ELISA system for assessing humoral immunity against SAT2/XIV FMDV, which is 100% homologous with the vaccine strain and demonstrates high diagnostic parameters, is a reliable tool for assessing the quality of the SAT2/XIV FMD vaccine.