Impact of Mycobacterium bovis-induced pathology on interpretation of QuantiFERON®-TB Gold assay results in African buffaloes (Syncerus caffer)

Cell-Mediated Immunological Biomarkers and Their Diagnostic Application in Livestock and Wildlife Infected With Mycobacterium bovis

“…The former, IL-1β, has demonstrated high Se for M. bovis detection in cattle, particularly when used in parallel with an IGRA (5,31). Although not explicitly pro-inflammatory, two biomarkers (IP-10 and IL-8) have been detected at higher concentrations than IFN-γ and have shown possible correlation with bTB progression in cattle and African buffaloes (5,72,84). Considering their robust response early after M. bovis infection, these biomarkers could be well-suited for detecting M. bovis infection in less studied species.…”

“…The same has been shown in African buffaloes using the same platform, and IP-10 has demonstrated high test Se in this species (30,40). Furthermore, higher levels of IP-10 in incubated samples without antigen stimulation have been correlated to the detection of M. bovis pathology in infected buffalo populations (72). Using the same assay as for buffaloes, Parsons et al (99) showed a strong correlation between IP-10 and IFN-γ release, and the robustness of IP-10 as a biomarker of M. bovis infection in cattle.…”

“…Furthermore, IGRAs demonstrate limited Se in early infection stages and in general, bTB diagnostic assays are unable to distinguish infection from disease (13,21,25,58,71). On the other hand, a recent study by Bernitz et al (72) observed that levels of IFN-γ and IP-10 in incubated unstimulated whole blood were elevated in infected buffaloes with observable pathological changes consistent with bTB in comparison to uninfected controls. Furthermore, increased IFNγ significantly correlated with increasing severity of pathological changes in the infected buffaloes, consistent with observations of associations between antigen-stimulated IFN-γ and bTB pathology in cattle and badgers, demonstrating the potential for these cytokines to be used as indicators of bTB disease (72)(73)(74).…”

“…The host immune response to mycobacteria is naturally linked to disease progression yet bTB generally presents with extended and advanced, poorly described disease stages, posing an additional challenge for the extension of IFN-γ-based diagnostics to distinguish infection from active disease (120,122). However, correlations between IFN-γ and M. bovis pathology have been preliminarily detected in badgers and buffaloes (72,74). Moreover, investigating the associations between cytokine responses at both a gene and protein level, alongside hostspecific pathological changes, can provide more insight on the diagnostic potential of IFN-γ and additional biomarkers (5,63,75,94,123,124).…”

Use of PrimeStore® Molecular Transport Medium and Xpert MTB/RIF Ultra for Rapid Detection of Mycobacterium Bovis in African buffaloes (Syncerus Caffer).

“…During the 2019 annual test-and-slaughter bTB control program, African buffaloes were captured, immobilised, sampled and tested for bTB, using the testing regime previously described 18 . Bovine TB test-positive buffaloes (n = 22) underwent post-mortem examination as previously described 18 . Various tissues with gross pathological lesions consistent with bTB 18 were dissected and swabbed during post-mortem examination using PrimeStore® swabs (Longhorn Vaccines and Diagnostics, San Antonio, Texas, USA) and stored in PrimeStore® MTM (Longhorn Vaccines and Diagnostics) at ambient temperature (which may reach temperatures up to 25°C during winter in HiP) until further processing.…”