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

Florencia Celeste Mansilla,Myrian Vanesa Trotta,Alejandra Victoria Capozzo,Sergio Gastón Caspe,Mariano Pérez-Filgueira,Juan Manuel Sala

doi:10.1080/09712119.2017.1335641

Abstract

ABSTRACTBuffaloes 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 high-throughput 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.

Highlights

Foot-and-mouth disease (FMD) is an acute, highly contagious viral disease that affects a wide range of hosts, including buffaloes (Grubman & Baxt 2004; Organization for Animal Health (OIE) 2012), and is distributed worldwide
An accurate assessment of herd immunity to estimate the expected protection against foot-and-mouth disease virus (FMDV) is paramount for countries undergoing compulsory vaccination programmes
Serology studies measuring antibodies to structural proteins induced by vaccines are not available for buffaloes; there is no information about the protective virus neutralization test (VNT) titres in this species, and there is only one paper published in the 1990s (Araujo et al 1996) analysing if Liquid-phase blocking ELISA (LPBE) titres match with those measured by the VNT

Summary

Introduction

Foot-and-mouth disease (FMD) is an acute, highly contagious viral disease that affects a wide range of hosts, including buffaloes (Grubman & Baxt 2004; OIE 2012), and is distributed worldwide. The current vaccine in Argentina is oil-adjuvanted and contains four foot-and-mouth disease virus (FMDV) strains. Water buffalo (Bubalus bubalis) population in Argentina is exceeding 100,000 heads, which is the third largest population in America, after Brazil and Venezuela. Buffaloes are located in the north-east of the country within the FMD vaccination territories (Crudeli 2014) and in neighbouring areas close to the border with Paraguay, where the latest regional FMDV-type O outbreak occurred in 2011 (Maradei et al 2013; Brito et al 2015). FMDV transmission between cattle and water buffaloes has been observed in natural outbreaks (Dutta et al 1983; Samara & Pinto 1983)

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