Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/20/2007
Publication Date: 7/8/2007
Citation: Karcher, E., Beitz, D.C., Stabel, J.R. 2007. Osteopontin Expression During the Periparturient Period in Dairy Cows Naturally Infected with Mycobacterium avium subsp. paratuberculosis Infection [abstract]. American Dairy Science Association.
Technical Abstract: Investigation of the role of osteopontin (Opn) in Johne’s disease is of interest based upon its ability to influence cytokine expression and to improve host defense against mycobacterial infections. The objective of this study was to characterize Opn expression and secretion by peripheral blood mononuclear cells (PBMCs) isolated from periparturient dairy cows naturally infected with Mycobacterium avium subsp. paratuberculosis (MAP). Twenty-five multiparous Holstein cows were assigned to 3 groups based upon their infection status: 1) noninfected healthy cows (n = 8), subclinically infected cows (n = 10), and clinically infected cows (n = 7). Blood was collected from the jugular vein from 3 wks pre- through 5 wks post-calving. PBMCs were isolated from the buffy coat fractions of whole blood from 3 wks pre- through 5 wks post-calving. PBMC were cultured for 24 h with and without MAP whole cell sonicate (MPS), RNA was extracted from cells, and converted to first-strand cDNA. Real-time PCR was performed on each sample to evaluate the expression of Opn. RT-PCR data was evaluated using 2-(Delta Delta Ct) with samples calibrated within treatment to mean Delta Delta Ct value at one day after calving. Immunoblot analysis was performed for detection of Opn protein from cultured PBMCs. PBMC's isolated from subclinical cows expressed greater amounts of Opn mRNA compared with control (P<0.06) and clinical (P<0.05) cows. Expression was higher prepartum, followed by a decline at calving that was consistent until 21 days postpartum. MPS-stimulated PBMCs from subclinical cows expressed less Opn mRNA than control and clinical cows (P<0.05). There was no effect of parturition on expression from stimulated cells, regardless of treatment group. Immunoblot analysis of Opn detected a predominant band at 50 kDa and three minor bands at 62, 37, and 24 kDa. The data indicate an ability of MAP infection and parturition to modulate Opn expression. Key Words: periparturient, Osteopontin, Mycobacterium avium subsp. paratuberculosis