Validation of a competitive enzyme-linked immunosorbent assay to improve the serological diagnosis of swine vesicular disease

Swine vesicular disease (SVD) is an infectious viral disease of pigs. The clinical symptoms of SVD are indistinguishable from other vesicular diseases. In countries free of vesicular diseases, rapid SVD diagnosis and differentiation from other vesicular diseases are essential. In this report, a competitive enzyme-linked immunosorbent assay (cELISA) was developed and validated to improve the current SVD serological diagnosis. In this cELISA, an anti-SVD monoclonal antibody (mAb) captures the recombinant SVD virus-like particle (SVD-VLP) antigen, and 5B7 mAb is used as a competitor to compete with polyclonal antibodies in SVD-positive sera. The cut-off value of the SVD-VLP based cELISA (SVD-VLP cELISA) is >= 65% inhibition (%). The determined diagnostic specificity was 99.2%. SVD-VLP cELISA successfully detected SVD antibodies in the sera of SVD-infected animals and produced a diagnostic sensitivity of 100%. A panel of SVD positive sere including outbreak samples (n = 11) and samples (n = 5) from experimentally inoculated pigs, were correctly identified as positive by the SVD-VLP cELISA. In terms of reducing false positives detected by the currently used cELISA (5B7 cELISA), the performance of SVD-VLP cELISA is comparable to the gold standard virus neutralization test.