Alternatives for the serological assessment of foot-and-mouth disease vaccine immunity in buffaloes (Bubalus bubalis)

Abstract

Buffaloes are compulsory vaccinated against foot-and-mouth disease virus (FMDV) in many countries as part of the official control programmes. Serological testing aimed to indirectly assess herd immunity is currently performed using the same Enzyme-linked immunosorbent assays (ELISAs) applied for bovine sera, assuming an agreement between the ELISA's diagnostic results and those obtained using the virus neutralization test (VNT). Here we evaluated the accuracy of different ELISA tests to assess vaccine-induced antibodies against FMDV in buffalo's sera classified according to their VNT titres. Currently used liquid-phase blocking ELISA yielded very low specificity, producing high titres for many samples with low VNT titres. To increase specificity, we developed an indirect ELISA using purified 140S viral particles and an avidity single-dilution ELISA, which includes a urea washing step after the incubation of the diluted serum sample, to detach weak binders. Combining these two highthroughput single-dilution tests, an excellent concordance with VNT was achieved. This is the first study analysing the diagnostic agreement of traditional and novel serological tests with VNT for the indirect assessment of antibodies against FMDV capsid proteins in buffalo serum samples. ARTICLE HISTORY

Kinetics of foot-and-mouth disease vaccine-induced antibody responses in buffaloes (Bubalus bubalis): avidity ELISA as an alternative to the virus neutralization test

“…Results were analyzed by multivariate two-way ANOVA, followed by Bonferroni correction to compare between different time points. Sensitivity and specificity were estimated using ROC curves for the best-fit values for each individual assay as described before (18). Tables were built to identify the frequency of true positive and negative results, as well as false positive and negative results according to the VNT titers used as reference assay ("gold standard").…”

“…However, the difficulties inherent to the VNT, such as the need for cultured cells, live FMDV and dedicated facilities prevent this low-throughput assay from being suitable for the field assessment of vaccine-induced antibodies, being ELISAs preferred for this purpose. We have demonstrated before that the currently used liquid-phase blocking ELISA (LPBE) yielded very low specificity with buffalos' serum samples, probably due to the presence of high levels of "sticky" natural antibodies that over-estimate antigen-specific antibody levels, among other issues related to the assay itself (18). Alternatively, aiming to improve the specificity of the antibody assessment, we developed an indirect ELISA (IE) using purified 140S viral particles, which proved to detect IgG mainly directed against capsid-exposed epitopes (15); and an avidity singledilution ELISA (AE) based on the same indirect design (15), which includes an additional urea washing step to detach weak binders (18,19).…”

“…We have demonstrated before that the currently used liquid-phase blocking ELISA (LPBE) yielded very low specificity with buffalos' serum samples, probably due to the presence of high levels of "sticky" natural antibodies that over-estimate antigen-specific antibody levels, among other issues related to the assay itself (18). Alternatively, aiming to improve the specificity of the antibody assessment, we developed an indirect ELISA (IE) using purified 140S viral particles, which proved to detect IgG mainly directed against capsid-exposed epitopes (15); and an avidity singledilution ELISA (AE) based on the same indirect design (15), which includes an additional urea washing step to detach weak binders (18,19). The improved performance of avidity ELISA compared to LPBE was demonstrated by our group (18) and further verified in a recent study using field serum samples from 40 multi-vaccinated buffalos (20).…”

“…Alternatively, aiming to improve the specificity of the antibody assessment, we developed an indirect ELISA (IE) using purified 140S viral particles, which proved to detect IgG mainly directed against capsid-exposed epitopes (15); and an avidity singledilution ELISA (AE) based on the same indirect design (15), which includes an additional urea washing step to detach weak binders (18,19). The improved performance of avidity ELISA compared to LPBE was demonstrated by our group (18) and further verified in a recent study using field serum samples from 40 multi-vaccinated buffalos (20).…”

Şap virüsü şuşlarına karşı poliklonal antikor üretimi

“…It is necessary to produce Abs (polyclonal and/or monoclonal) for FMDV SP ELISA tests against each of newly emerged, genotypically crucial, exotic strains of FMDV just like the effort of a new primer-probe design for the molecular differentiation of novel FMDV with PCR. However, the period for the production of polyclonal Abs for FMDV serology takes a long time and laborious work (Parida 2009;Lavoria et al 2012;Sala et al 2018;Salem et al 2019).…”