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

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.

Cross-Serotype Reactivity of ELISAs Used to Detect Antibodies to the Structural Proteins of Foot-and-Mouth Disease Virus

“…The integrity of capsids in the antigen preparations was measured with mAbs. One of these (5B2) recognizes an internal epitope on VP2 that is common to all serotypes [ 20 ] and can only be bound if capsids are dissociated. The other two are neutralizing and specific for epitopes on the external surface of the capsid that are available in both intact and dissociated particles.…”

Avidity of Polyclonal Antibodies to Foot-and-Mouth Disease Virus in Bovine Serum Measured Using Bio-Layer Interferometry

“…The GH loop is commonly recognised as one of the key immunodominant sites on the FMDV particle and often referred to as site 1 [24]. At least a further four sites have been characterised using monoclonal antibodies [4,6,17], with ongoing research into novel epitopes on the virus capsid revealing further sites within VP2 and VP3 [20,25,26].…”

“…Here, we used a biotinylated peptide representing amino acids 134-157 of the O1 Kaufbeuren VP1 protein encompassing the GH loop and Arg-Gly-Asp (RGD) motif responsible for interacting with the integrin receptor on target host cells (Table 1). Biotinylated peptides were synthesised commercially (Peptide Protein Research Ltd., Fareham, UK) as previously described [20].…”

Phage Display Screening of Bovine Antibodies to Foot-and-Mouth Disease Virus and Their Application in a Competitive ELISA for Serodiagnosis

“…Due to pan-serotype specificity, BvOA7 cannot be used to differentiate serotypes but can be developed as a general detection reagent for FMDV antibodies regardless of serotypes. Other than type-specific assay, there is also a need for a universal serological test as simplified frontline diagnostics as described recently [ 32 ].…”