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Updated: Aug 13, 2026
Application of Long-term cultured Interferon-γ Enzyme-linked Immunospot Assay for Assessing Effector and Memory T Cell Responses in Cattle
Published on: July 11, 2015
In vitro immunodiagnostic assays for bovine tuberculosis
1CSIRO, Division of Animal Health, Parkville, Vic, Australia.
Insights
The bovine interferon gamma (IFN-gamma) assay offers a more sensitive diagnostic tool for bovine tuberculosis than traditional skin tests. Comparing responses to bovine and avian PPD antigens minimizes false positives in cattle.
Area of Science:
- Veterinary Immunology
- Infectious Disease Diagnostics
- Mycobacterial Research
Background:
- Bovine tuberculosis (TB) diagnosis relies on cellular immune responses to Mycobacterium bovis (M. bovis).
- Current serological tests for bovine TB exhibit low sensitivity, necessitating complementary diagnostic approaches.
- Cellular assays, like the intradermal tuberculin test, are standard but have limitations.
Purpose of the Study:
- To evaluate the diagnostic performance of a novel bovine interferon gamma (IFN-gamma) assay for bovine TB.
- To assess the sensitivity and specificity of the IFN-gamma assay compared to existing diagnostic methods.
- To address challenges of cross-reactivity in TB diagnostics through comparative antigen testing.
Main Methods:
- A whole blood in vitro assay measuring IFN-gamma production in cattle.
- Field trials in Australia comparing the IFN-gamma assay with the intradermal tuberculin test.
- Utilized a comparative assay design comparing bovine PPD and avian PPD antigen responses.
Main Results:
- The bovine IFN-gamma assay demonstrated significantly higher sensitivity than the intradermal tuberculin test in field trials.
- A comparative assay using bovine PPD and avian PPD effectively mitigated false-positive reactions.
- Identified M. bovis specific proteins, but their diagnostic utility is limited by immune response diversity.
Conclusions:
- The bovine IFN-gamma assay is a promising, sensitive diagnostic tool for bovine tuberculosis.
- Comparative IFN-gamma testing enhances specificity by controlling for cross-reactivity.
- Further research into host-pathogen interactions is needed to overcome genetic diversity challenges in diagnostics.
Abstract:
The immune response to mycobacterial infections in cattle is predominantly cellular in nature and current diagnostic tests for M. bovis are based on the measurement of T cell responses. The low sensitivity of serological assays for tuberculosis is therefore not surprising and serological tests will at best be used to complement rather than replace cellular assays. The recently developed bovine interferon gamma (IFN-gamma) assay is a rapid (24 hour) and simple whole blood in vitro assay, which in Australian field trials was found to be significantly more sensitive than the intradermal tuberculin test for the diagnosis of bovine tuberculosis. The problem of false-positive reactions, due to the cross-reactive nature of the antigen preparations used, can largely be overcome by using a comparative assay in which an animal's IFN-gamma response to bovine PPD and avian PPD are compared. Although reasonably M. bovis specific proteins have been identified and characterised, their use in either serological or cellular diagnostic assays is likely to be restricted due to the genetic diversity of the bovine immune response to M. bovis infection.
