Detection of Bovine Antibodies against a Conserved Capsid Epitope as the Basis of a Novel Universal Serological Test for Foot-and-Mouth Disease.

A Ludi,K Parekh,D P King,S Grazioli,A S Asfor,G Wilsden,S Parida,E Brocchi,Brad Fenwick,N Howe,T J Tuthill,S Berryman

doi:10.1128/jcm.01527-19

Abstract

Diagnostic tests for foot-and-mouth disease (FMD) include the detection of antibodies against either the viral nonstructural proteins or the capsid. The detection of antibodies against the structural proteins (SP) of the capsid can be used to monitor seroconversion in both infected and vaccinated animals. However, SP tests need to be tailored to the individual FMD virus (FMDV) serotype and their sensitivity may be affected by antigenic variability within each serotype and mismatching between test reagents. As a consequence, FMD reference laboratories are required to maintain multiple type-specific SP assays and reagents. A universal SP test would simplify frontline diagnostics and facilitate large-scale serological surveillance and postvaccination monitoring. In this study, a highly conserved region in the N terminus of FMDV capsid protein VP2 (VP2N) was characterized using a panel of intertype-reactive monoclonal antibodies. This revealed a universal epitope in VP2N which could be used as a peptide antigen to detect FMDV-specific antibodies against all types of the virus. A VP2-peptide enzyme-linked immunosorbent assay (VP2-ELISA) was optimized using experimental and reference antisera from immunized, convalescent, and naïve animals (n = 172). The VP2-ELISA is universal and simple and provided sensitive (99%) and specific (93%) detection of antibodies to all FMDV strains used in this study. We anticipate that this SP test could have utility for serosurveillance during virus incursions in FMD-free countries and as an additional screening tool to assess FMD virus circulation in countries where the disease is endemic.

Highlights

Foot-and-mouth disease (FMD) is an economically devastating viral disease of cloven-hoofed animals with a global distribution
monoclonal antibodies (MAbs) 4A3 recognized virus-infected cells when used as the primary antibody in indirect immunofluorescence microscopy of IBRS-2 cell cultures infected with type O FMD virus (FMDV) (Fig. 1e)
The benefits of this assay are that FMDV-specific structural proteins (SP) antibodies from all seven serotypes can be detected without the requirement for individual specific antigen or antibody reagents such as are required for existing tests such as virus neutralization test (VNT), liquid-phase blocking ELISA (LPBE), and solid-phase competition ELISA (SPCE)

Summary

Introduction

Foot-and-mouth disease (FMD) is an economically devastating viral disease of cloven-hoofed animals with a global distribution. The specificity of these tests is less than 100% [9], and testing algorithms that are designed to confirm absence of FMDV circulation in large populations usually adopt screening and confirmatory serological assays with covariant rates of false positivity [7,8,9]. In this context, enzyme-linked immunosorbent assays (ELISAs) that measure levels of FMDV-specific antibodies directed at capsid structural proteins (SP) are widely used to augment NSP tests for serosurveillance activities [10,11,12,13].

Methods

Results

Conclusion