Agreement between assays of cell-mediated immunity utilizing Mycobacterium bovis-specific antigens for the diagnosis of tuberculosis in African buffaloes (Syncerus caffer)

Mycobacterium bovis in a Free-Ranging Black Rhinoceros, Kruger National Park, South Africa, 2016

“…We detected no antibodies to the M. bovis antigens MPB83 or ESAT6/CFP10 complex in serum samples tested with the Dual Path Platform VetTB assay (Chembio Diagnostic Systems, Inc., Medford, NY, USA) ( 6 ). PCR analyses confirmed M. bovis infection, both directly from the lung tissue and indirectly from mycobacteria culturing of lung tissue samples, as previously described ( 7 , 8 ). …”

IP-10 Is a Sensitive Biomarker of Antigen Recognition in Whole-Blood Stimulation Assays Used for the Diagnosis of Mycobacterium bovis Infection in African Buffaloes (Syncerus caffer)

“…In conclusion, while recent advancements have been made in increasing the specificity of tests for cell-mediated immunity for the diagnosis of M. bovis infection in African buffaloes (3,8), there remains a need for increased diagnostic sensitivity. This pilot study indicates that IP-10 shows promise as a diagnostic biomarker in this species and that its measurement in peptide-stimulated whole blood may increase the sensitivity of conventional IGRAs.…”

“…The latter detect the release of interferon gamma in whole blood or from isolated peripheral blood mononuclear cells (PBMCs) in response to M. bovis purified protein derivative (PPD) (5) or to more specific antigens such as the 6-kDa early secreted antigenic target (ESAT-6) and the 10-kDa culture filtrate protein (CFP-10) (6, 7). Recently, IGRAs utilizing the latter antigens, i.e., the modified QuantiFERON TBGold (mQFT) assay and the commercially available Bovigam PC-EC assay (PC-EC) and Bovigam PC-HP assay (PC-HP), have been described and evaluated for the diagnosis of BTB in buffaloes (3,8). Notably, the mQFT assay, which is highly practical for use under field conditions, and the highly specific PC-EC assay are both less sensitive than the less-specific PC-HP IGRA (8).…”

“…Recently, IGRAs utilizing the latter antigens, i.e., the modified QuantiFERON TBGold (mQFT) assay and the commercially available Bovigam PC-EC assay (PC-EC) and Bovigam PC-HP assay (PC-HP), have been described and evaluated for the diagnosis of BTB in buffaloes (3,8). Notably, the mQFT assay, which is highly practical for use under field conditions, and the highly specific PC-EC assay are both less sensitive than the less-specific PC-HP IGRA (8). As such, the utility of the mQFT and PC-EC assays would be increased by improving the detection of immune sensitization to ESAT-6/CFP-10.…”

“…Because the PC-EC and PC-HP assays have been shown to have greater sensitivity than the TST in this species (8) and because human studies have solely investigated IP-10 responses to peptide antigens (10), we used the PC-EC and PC-HP assays as reference tests. Moreover, since mycobacterial culture is considered to be an imperfect gold standard of M. bovis infection (12) and because these data were not available for Bovigam-negative animals in this study, an optimal diagnostic cutoff value for IP-10 could not be calculated.…”