Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/11/2007
Publication Date: 3/17/2008
Citation: Karcher, E.L., Beitz, D.C., Stabel, J.R. 2008. Parturition and Mycobacterium avium subsp. paratuberculosis: A Potential Interface for the Pathogenesis of Johne's Disease [abstract]. American Dairy Science Association.
Technical Abstract: Mycobacterium avium subsp. paratuberculosis (MAP), the causative agent of Johne’s disease (JD), is estimated to infect more than 22% of US dairy herds and cost the industry $250 million annually. One major period of stress for dairy cows is the periparturient period, and field observations suggest that MAP-infected cows may advance to the clinical stage of the disease during the early post-partum period. Research on what prompts the progression of disease during this time period is lacking. Therefore, our overall objective was to gain a better understanding of the host immune response to MAP infection during the periparturient period. In the first study, we characterized cytokine gene expression and secretion in periparturient dairy cows naturally infected with MAP. Peripheral blood lymphocyte percentages were also analyzed with flow cytometry and cell populations were further delineated by staining for CD5. Cytokine gene expression was not significantly altered in cows naturally infected with MAP compared to controls. The periparturient period mediated gene expression of IFN-gamma, IL-4, and IL-10 regardless of cow infection status. The percentages of lymphocyte subsets were modulated by MAP infection and by the periparturient period. These factors also influenced the expression of CD5 on T-cell subpopulations and B-cells. The second study was designed to determine the role of osteopontin (Opn) on disease progression in periparturient MAP-infected cows. Investigation of the role of Opn in JD is of interest since Opn can influence cytokine expression and improve host defense against mycobacterial infections. Results revealed that Opn expression and protein abundance in PBMCs isolated from periparturient cows are modulated by both MAP infection status and parturition. We present here the first known data investigating Opn gene and protein expression in MAP-infected cows. The results of our various studies contribute to a very small body of literature focusing on the progression of JD during the early post-parturient time period. Key Words: cytokines, periparturient, M. avium subsp. paratuberculosis