EVALUATION OF AN ENZYME-LINKED-IMMUNOSORBENT-ASSAY THAT USES THE 41-KD FLAGELLIN AS THE ANTIGEN FOR DETECTION OF ANTIBODIES TO BORRELIA-BURGDORFERI IN CATTLE

An ELISA was developed to detect antibodies to the 41-kd flagellin (P4 1) of Borrelia burgdorferi in senum obtained from cattle. Absorption s tudies, immunoblot analysis, immunoelectron microscopy, and correlatio n of results of the P41-ELISA and the P39-ELISA as well as measurement of the antibody to P41 in calves challenge-exposed with Borrelia thei leri were used to assess the specificity of the P41-ELISA. Antigens de rived from Escherichia coli, Leptospira interrogans serovar hardjo, an d B burgdorferi were used for absorption studies and immunoblot analys is. Antibodies to P41 of B burgdorferi cross-reacted with antigens of E coli, but were not cross-reactive with L hardjo. A value 3 SD higher than the mean of the negative-control population of cattle was define d as the minimum value (cutoff value) for a positive result by the P41 -ELISA. Use of this value for classification of test results reduced t he predicted rate of false-positive results attributable to E coli cro ss-reactivity to 1%. Immunoblot analysis revealed that test-positive s erum from cattle reacted mainly with 41-, 39-, 34-, and 31-kd proteins of B burgdorferi, as well as several smaller proteins. Immunoelectron microscopy revealed that serum from cattle that was test-positive by the P41-ELISA bound to the flagellin and outer membrane of B burgdorfe ri. Results of absorption studies, immunoblot analysis, and immunoelec tron microscopy were correlated and indicated that serum from cattle t hat was test-positive by P41-ELISA had stronger reactivity to B burgdo rferi antigens than to antigens of E coli or L hardjo. The concentrati ons of antibodies measured by P41-ELISA and P39-ELISA testing were hig hly correlated (R(2) = 0.78). Calves challenge-exposed with B theileri also had test-positive results by the P41-ELISA as early as 2 weeks a fter exposure, but serum antibody concentrations decreased to prechall enge-exposure concentrations by 9 weeks after exposure. We concluded t hat the P41-ELISA was useful as a screening method to detect B burgdor feri infections in cattle.