Avidity ELISA as an alternative to the Virus Neutralization Test to assess FootAnd-Mouth Disease vaccine-induced antibody responses in buffaloes (Bubalus Bubalis)

SALA, JUAN MANUEL; MANSILLA, FLORENCIA C.; MIRAGLIA, M. CRUZ; PEREZ-FILGUEIRA, DANIEL MARIANO; CAPOZZO, ALEJANDRA V.

Kruger Park

Simposio; IVIS 2023 - 13th International veterinary immunology symposium; 2023

Buffaloes are considered a reservoir of foot and mouth disease virus (FMDV) in the carrier state with the potential to spread the virus in the field. They are compulsorily vaccinated in many countries as part of official control programs. Vaccine-induced antibodies in buffaloes are currently evaluated using either the virus neutralization test (VNT) or by liquid-phase blocking ELISA (LPBE). Both assays present flaws. The VNT gives information on the biological activity of antibodies but is cumbersome and has low throughput. On the other hand, the LPBE measures total FDMV-specific antibodies and have not been validated for buffaloes´ samples. Previous data from our laboratory demonstrated that the vaccine- induced antibodies assessed by the LPBE yielded low specificity with buffaloes’ samples. In contrast, a single-dilution avidity ELISA (AE) aimed to detect high-avidity antibodies against exposed epitopes, combined with an indirect ELISA (IE) to assess IgG levels, produced more reliable results. Here we analysed for the first time the kinetics of the antibodies induced by vaccination in two different buffalo herds (n=91) over 120 days using AE, IE, LPBE, and the VNT. Kinetics were similar in the different assays, with an increase of antibodies between 0- and 14-days post-vaccination (dpv) which were maintained thereafter. VNT and AE results were concordant (Kappa value: 0.76), and both assays revealed a decay in the antibody response in calves with maternal antibodies at 90 and 120 dpv, which was not evidenced by the LPBE. These results show that kinetics of antibody responses to FMD vaccination are similar in buffalo and cattle, and support the use of indirect ELISA assays, in particular Avidity ELISA, as alternatives to the VNT for vaccine-immunity monitoring irrespectively of the animal´s passive or active immune status.