A protein A/G indirect enzyme-linked immunosorbent assay for the detection of anti-Brucella antibodies in Arctic wildlife

Abstract

A species-independent indirect enzyme-linked immunosorbent assay (iELISA) based on chimeric protein A/G was established for the detection of anti- Brucella antibodies in Arctic wildlife species and compared to previously established brucellosis serological tests for hooded seals ( Cystophora cristata), minke whales ( Balaenoptera acutorostrata), sei whales ( Balaenoptera borealis), fin whales ( Balaenoptera physalus), and polar bears ( Ursus maritimus), as well as bacteriology results for reindeer and caribou ( Rangifer tarandus sp.). The protein A/G iELISA results were consistent with the other serological tests with Cohen kappa values between 0.47 and 0.92, and the protein A/G iELISA can thus offer a technically simple method for these species yielding results consistent with established brucellosis serological tests. Receiver operator characteristics analysis proved that the reindeer and caribou protein A/G iELISA results were consistent with the bacteriological gold standard with an area under the curve of 0.99, and the protein A/G iELISA was thus validated as a sensitive and specific serological method for the detection of anti- Brucella antibodies in reindeer and caribou. The binding of the antibodies from the respective species to protein A and G were also evaluated in the iELISA. The antibodies from hooded seals and polar bears reacted stronger to protein A than to G. The sei whale, fin whale, reindeer, and caribou antibodies reacted stronger to protein G than to A. The minke whale antibodies reacted to both protein A and G. There was a strong correlation ( rs = 0.88–0.98) between the optical density results obtained with the iELISA with protein A/G and protein A or G, showing that protein A/G is as well suited as protein A or G for the detection of anti- Brucella antibodies in these species with the iELISA.