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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
Interferon gamma responses to proteome-determined specific recombinant proteins: potential as diagnostic markers for
Valerie Hughes1, Susan Denham, John P Bannantine
1Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik EH26 0PZ, United Kingdom. Val.Hughes@moredun.ac.uk
Abstract:
Johne's disease (JD), or paratuberculosis is a fatal enteritis of animals caused by infection with Mycobacterium avium subspecies paratuberculosis (Map). There may be a long subclinical phase with no signs of clinical disease. Diagnosis of JD is problematic and no test can reliably detect sub-clinical disease. Th1 responses to Map are believed to be activated first with a later switch to Th2 responses and progression to clinical disease. Detection of a cell-mediated response, indicated by interferon gamma (IFN-γ) produced in response to mycobacterial antigens, may give an early indication of infection. Crude extracts of Map (PPDj) have been used to detect the cell-mediated response, but more specific, quantifiable antigens would improve the test. Thirty Map-specific proteins were screened for their ability to raise a cell-mediated response in subclinically infected sheep. Four proteins were selected and tested using blood from subclinical animals and controls from a JD-free flock. Three proteins elicited IFN-γ levels which were higher in the subclinical group than in the control group, two were statistically significant. Thus these proteins have the ability to discriminate groups of infected and uninfected animals and may have use in diagnosis of JD.
Insights
Diagnosing Johne
Area of Science:
- Veterinary Immunology
- Infectious Diseases
- Animal Health
Background:
- Johne's disease (paratuberculosis) is a fatal enteritis in animals caused by Mycobacterium avium subspecies paratuberculosis (Map).
- Diagnosis is challenging due to a long subclinical phase and limitations of current tests.
- Cell-mediated immunity, indicated by interferon gamma (IFN-γ) production, may offer early infection detection.
Purpose of the Study:
- To identify specific Mycobacterium avium subspecies paratuberculosis (Map) proteins for improved diagnosis of Johne's disease (JD).
- To evaluate the ability of these proteins to elicit a cell-mediated immune response in subclinically infected sheep.
Main Methods:
- Screening of thirty Map-specific proteins for their ability to induce cell-mediated responses.
- Testing selected proteins using blood samples from subclinically JD-infected sheep and control animals from a JD-free flock.
- Measuring interferon gamma (IFN-γ) levels as an indicator of cell-mediated immunity.
Main Results:
- Three of the four selected Map proteins induced higher IFN-γ levels in subclinically infected sheep compared to controls.
- Two of these proteins showed statistically significant differences between the infected and control groups.
- These proteins demonstrate potential for discriminating between infected and uninfected animals.
Conclusions:
- Specific Map proteins can elicit a detectable cell-mediated immune response in subclinically infected sheep.
- These identified proteins show promise as diagnostic markers for early Johne's disease detection.
- Further development of these antigens could lead to improved diagnostic tests for JD.
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