Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2008
Publication Date: 11/15/2008
Citation: Karcher, E.L., Johnson, C.S., Beitz, D.C., Stabel, J.R. 2008. Osteopontin Immunoreactivity in the Ileum and Ileoceccal Lymph Node of Dairy Cows Naturally Infected with Mycobacterium avium subsp. paratuberculosis. Veterinary Immunology and Immunopathology. 126(1-2):142-148.
Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle characterized by diarrhea, reduced feed intake, weight loss and death. Cattle usually become infected as young calves by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. Clinical signs of disease may be precipitated by stressors such as parturition, heavy lactation, concomitant viral or bacterial infections, and malnutrition. Many changes occur in the host immune system during the different stages of infection. The present study was designed to evaluate the effects of the infection status of the host on the expression of a specific protein, osteopontin, involved in host immunity. Tissues from cows with paratuberculosis and healthy control cows were stained for the presence of this protein. The frequency of staining was higher in infected cows in the clinical stage of disease. These results suggest that the host immune response changes as animals progress from one stage of disease to another and that this is associated with changes in the expression of the osteopontin protein. This information is useful in determining avenues for modifying host immune responses to prevent or alleviate clinical disease.
Technical Abstract: Osteopontin (Opn), a highly acidic glycoprotein, promotes cellular adhesion and recruitment and has been shown to be upregulated in the granulomas of mycobacterial infections. Johne’s disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is associated with granulomatous enteritis. The objective of this experiment was to identify Opn in the ileum and ileocecal lymph node (ICN) of dairy cows naturally infected with MAP and to compare the frequency and intensity of staining between noninfected healthy controls, subclinical and clinical cows. Sections from these three groups of animals were selected from a tissue archive. Immunohistochemical analysis was used to determine the location and expression of Opn. The frequency and intensity of staining was also reported. Confirmation of acid-fast bacilli in the tissue sections was achieved by the Ziehl-Neelsen method. Within the ileal tissue, macrophages, lymphocytes, and plasma cells stained positive for Opn. Clinical cows expressed Opn at a greater frequency in the lamina propria. Control and subclinical cows did not have areas of granulomatous inflammation but cells staining for Opn were equally intense for the three groups. The frequency of staining for Opn in the ICN was not affected by MAP infection. Results of this study confirm for the first time, the expression of Opn in the ileum and ICN of MAP-infected cattle.