Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/22/2008
Publication Date: 7/7/2008
Citation: Karcher, E.L., Johnson, C.S., Bannantine, J.P., Beitz, D.C., Stabel, J.R. 2008. Osteopontin Immunoreactivity in Peripheral Blood Mononuclear Cells, Ileum, and Ileocecal Lymph Node of Dairy Cows Naturally Infected with Mycobacterium avium subsp. paratuberculosis [abstract]. American Dairy Science Association.
Technical Abstract: Osteopontin (Opn), a highly acidic glycoprotein, plays an early role in initiating the innate immune response to mycobacterial infections by promoting cellular adhesion and recruitment of inflammatory cells from the peripheral blood. The formation of granulomas at the site of Mycobacterium avium subsp. paratuberculosis (MAP) infection is critical for the early control of infection. The objective of this experiment was to identify Opn in peripheral blood mononuclear cells (PBMCs), 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. For analysis of peripheral blood, PBMCs were isolated weekly from naturally infected periparturient dairy cows 3 weeks prior to calving through 4 weeks postpartum. Immunoblotting detected Opn protein bands at 24, 37, 50, and 62-kDa in the PBMC lysates of all animals. The densities of the 24, 37, and 62-kDa proteins varied extensively between cows and the variation did not appear to be related to infection group. In order to determine the localization of Opn in the ileum and ICN, sections from these three groups 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 the 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. Osteopontin expression in the ICN was not affected by MAP infection. Results of this study confirm for the first time Opn localization in the peripheral blood and in the intestinal tract of MAP-infected cows and differences in Opn expression at the site of infection.