DEVELOPMENT AND EVALUATION OF A NOVEL ANTIGEN CAPTURE ASSAY FOR THE DETECTION OF CLASSICAL SWINE FEVER VIRUS-ANTIGENS

An antigen-capture enzyme immunoassay (EIA) was developed to detect cl assical swine fever virus (CSFV) antigen directly from 10% w/v tissue suspension. The assay, based on the sandwich principle, uses a biotiny lated monoclonal antibody bound to streptavidin-coated microplates as the capture system and a swine anti-CSFV antibody and rabbit anti-swin e HRPO-conjugate as the detector system. The antigen-capture EIA was c ompared with conventional virus isolation and polymerase chain reactio n (PCR) for detection of CSFV in tissues. The ability of the antigen-c apture EIA to discriminate classical swine fever (CSF) from bovine vir al diarrhea and African swine fever viruses was also tested. The assay was shown to detect 21 different strains of CSFV and was unreactive w ith tissues from uninfected animals. Signal to noise (S/N) ratios were calculated from the EIA absorbance values. Readings from samples posi tive by virus isolation (n = 47) averaged a S/N ratio of 5.34. in cont rast, samples negative by virus isolation (n =96) demonstrated a mean S/N ratio of 0.16. At S/N cut-off value of 1.0, all samples that yield virus isolation and PCR negative result were negative in the antigen- capture EIA. Compared with virus propagation in tissue culture using P K15 cells (followed by indirect peroxidase assay detection) and PCR, t he EIA had a specificity of 98.7% and a sensitivity of 91.4%. The EIA is simple, can be performed in 4 h and lends itself to automation for screening of tissues sample from pigs suspected of CSFV infection. (C) 1998 Elsevier Science B.V.