Study on interferon-gamma ELISA for tuberculosis in bison

Introduction
Researchers at the Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, Canada set out to improve diagnostic tools for managing endemic Mycobacterium bovis infections in wood bison. In their recent study, Chileshe et al. 2025 evaluated the cross-reactivity of commercially available ELISA kits for use on bison samples. Interferon-gamma release assays (IGRA) are widely used to evaluate the cellular immune responses in veterinary tuberculosis. Early detection is crucial not only to safeguard this threatened species but also to prevent potential spillover. 

Tools used
Five commercially available ELISA were selected based on their broad cross-reactivity across species. Among them were three kits from Mabtech: the Bovine IFN-γ ELISA in both Flex and Pro formats, and the Llama IFN-γ ELISA. Additional kits included a Bovine IFN-γ ELISA from Bio-Rad and the Bovigam 2G TB kit from ThermoFisher. These kits were evaluated for their ability to detect IFN-γ in bison blood samples.

Findings
The ELISA-based IGRA relies on measuring interferon-gamma (IFN-γ), a key cytokine produced in response to mycobacterial antigens. In this study, samples from healthy, bTB-free cattle and bison were used. To simulate a positive response, whole blood was stimulated with pokeweed mitogen (PWM), a potent activator of B and T cells that induces cytokine secretion, including IFN-γ. Unstimulated samples served as negative controls.

The strongest IFN-γ signal in PWM-stimulated samples was detected using Mabtech’s bovine IFN-γ ELISA kits. Both Flex and Pro formats showed high sensitivity and were further assessed for performance. The results confirmed good recovery after serial dilution, along with acceptable intra- and inter-assay precision.

Outlook
This study demonstrates that early detection of Mycobacterium bovis in bison is possible using commercially available ELISA kits. The findings build on previous research where Mabtech’s IFN-γ antibodies were successfully validated in other wildlife species, including rhinoceroses, African wild dogs, and African buffalo. Compared to traditional skin tuberculin tests, ELISA-based diagnostics offer a less invasive and potentially more accurate alternative. This approach could significantly enhance wildlife health monitoring and support better disease management strategies.