An enzyme-linked immunosorbent assay, using an EDTA-extracted antigen for the serology of Haemophilus pleuropneumoniae

Abstract

An enzyme-linked immunosorbent assay (ELISA) was proposed as an alternative to the complement-fixation test (CF) for the detection of antibodies of Haemophilus pleuropneumoniae, agent of the pleuropneumonia in pigs. In tests done with different antigen-extraction procedures (including Tween 20, sodium dodecyl sulfate, aqueous phenol, sonification, and heat treatment at 120 C), ethylenediaminetetraacetic acid (EDTA) provided a satisfactorily reactive antigen. Chromatography purification on Sephacryl S200 improved the specificity of this antigen. Using hyperimmune rabbit sera, we investigated the specificity and the sensitivity of the ELISA with the EDTA-purified antigen of the different serotypes of H pleuropneumoniae on selected swine sera in herds with confirmed H pleuropneumoniae infection, from specific-pathogen-free animals showing doubtful CF reactions. The ELISA proved to be highly specific and more sensitive than the CF test. Furthermore, evidence of cross-reactions with H parasuis, a common bacteria isolated in swine populations, was not found.