Use of blood matrices and alternative biological fluids for antibody detection in animal tuberculosis.

Bovine tuberculosis (bTB) control programs can be improved by implementation of advanced ante-mortem testing algorithms. Serodiagnostic methods using traditional blood or blood-derived specimens may benefit from the use of less invasive alternative biological fluids, provided those mirror systemic antibody responses. In the present study, we used Dual Path Platform (DPP) and Multiantigen Print Immunoassay (MAPIA) to compare antibody levels in ten sample types including whole blood (fresh and hemolyzed), plasma (fresh and leftover from Bovigam testing), serum, saliva, broncho-alveolar lavage, urine, diaphragm extract, and bile collected from cattle aerosol-infected with Mycobacterium bovis. High correlation (r = 0.97-0.99) in measurements of IgG antibodies to MPB70/MPB83 fusion antigen by DPP assay was found between all blood-derived specimens, supporting matrix equivalency. Broncho-alveolar lavage and diaphragm extract yielded positive results in all the infected animals tested, showing high correlation with matching serum data (r = 0.94 and r = 0.95, respectively) and suggesting their potential use in antibody assays. Characterized by MAPIA, the antigen reactivity patterns obtained with paired sera and alternative specimens were nearly identical, with slight differences in intensity. Antibodies were also found by DPP assay in saliva, urine, and bile from some of the infected animals, but the titers were relatively low, thus reducing the diagnostic value of such specimens. The proposed approach was evaluated in a pilot field study on warthogs diagnosed with M. bovis infection. Relative levels of antibody in tissue fluid obtained from lymph nodes or lungs were consistent with those detected in sera and detectable in all infected warthogs. The findings support the diagnostic utility of non-traditional biological fluids and tissue samples when used as alternative test specimens in serologic assays for bTB.