title: Dose-dependent interferon-gamma release in dairy calves experimentally infected with Mycobacterium avium subspecies paratuberculosis.
abstract: The interferon-gamma (IFN-γ) release assay is considered useful for diagnosis of subclinical paratuberculosis. However, interpretation can be subjective and complex; therefore, additional information regarding the course of the cellular immune response and effects of age and dose at infection would be helpful. Thirty-three calves were randomly allocated to 10 challenge groups and a negative control group. Calves were inoculated orally at 2 weeks or at 3, 6, 9, or 12 months of age. Within each age group, calves received either a high or low dose of Mycobacterium avium subspecies paratuberculosis (MAP). Monthly blood samples were collected, stimulated with Purified Protein Derivative (PPD) Johnin in vitro, and the subsequent release of IFN-γ measured. Calves inoculated with a high dose had earlier and stronger IFN-γ responses than low-dose calves. Furthermore, calves inoculated at 2 weeks of age produced less IFN-γ compared to those inoculated later in life. The IFN-γ response peaked (on average) 4 months after exposure; therefore, this would be an optimal interval to test cattle for MAP-infection (although the timing of field-based infections is unknown and clearance of infection a possibility). To conclude, the IFN-γ release assay could be a valuable diagnostic test on herd-level to indicate exposure to MAP.
authors.affiliation: Department of Production Animal Health, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1.
authors.forename: Rienske A R
authors.initials: RA
authors.lastname: Mortier
authors.affiliation: Department of Production Animal Health, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1.
authors.forename: Herman W
authors.initials: HW
authors.lastname: Barkema
authors.affiliation: Department of Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, Canada T2N 4Z6.
authors.forename: Todd A
authors.initials: TA
authors.lastname: Wilson
authors.affiliation: Department of Community Health Sciences, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, Canada T2N 4Z6.
authors.forename: Tolulope T
authors.initials: TT
authors.lastname: Sajobi
authors.affiliation: Department of Production Animal Health, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1.
authors.forename: Robert
authors.initials: R
authors.lastname: Wolf
authors.affiliation: Department of Production Animal Health, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, Canada T2N 4N1. Electronic address: jdebuck@ucalgary.ca.
authors.forename: Jeroen
authors.initials: J
authors.lastname: De Buck
mesh_terms: D000818:Animals; D015415:Biomarkers; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D004306:Dose-Response Relationship, Immunologic; D015964:Gene Expression Regulation, Bacterial / Q000276:immunology; D007371:Interferon-gamma / Q000097:blood / Q000378:metabolism*; D008297:Male; D016927:Mycobacterium avium subsp. paratuberculosis; D010283:Paratuberculosis / Q000175:diagnosis / Q000276:immunology / Q000378:metabolism*; D011897:Random Allocation; D013997:Time Factors
chemical_list: D015415:Biomarkers; D007371:Interferon-gamma
keywords: Age; Cellular immune response; Dose; Interferon; PPD Johnin; Paratuberculosis