Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2009
Publication Date: 9/15/2009
Publication URL: http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6TD5-4W15KNM-1-C&_cdi=5189&_user=4250360&_orig=search&_coverDate=04%2F07%2F2009&_sk=999999999&view=c&wchp=dGLbVlW-zSkzk&md5=821cf5ff875bbbd1f01679703661d60f&ie=/sdarticle.pdf
Citation: Khalifeh, M., Al-Majali, A.M., Stabel, J.R. 2009. Role of Nitric Oxide Production in Dairy Cows Naturally Infected with Mycobacterium avium subsp. paratuberculosis. Veterinary Immunology and Immunopathology. 131(1-2):97-104. 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. During this time the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced milk production by these animals, they also present a potential infective threat to the rest of the herd. Johne’s disease is difficult to manage and control on-farm. This study evaluates the measurement of a compound in the blood of infected and noninfected animals as a means of detecting infection in the early stages of disease. Understanding the host immune response to this pathogen will help us develop new diagnostic tools and vaccines to prevent the spread of disease.
Technical Abstract: Nitric oxide (NO) is a crucial mediator in host defense and is one of the major killing mechanisms within macrophages. Its induction is highly affected by the types of cytokines and the infectious agents present. In the current study, NO production was evaluated after in vitro infection of unfractionated peripheral blood mononuclear cells (PBMCs) with Mycobacterium avium subsp. paratuberculosis (M. avium subsp. paratuberculosis) after 8 hr, 3 and 6 days of culture for cows in different stages of disease. In addition, the effects of in vitro exposure to inhibitory cytokines such as interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) as well as the pro-inflammatory cytokine IFN-gamma were correlated with the level of NO production. Nitric oxide production was consistently higher in cell cultures from subclinically infected animals at all time points. An upregulation of NO production was demonstrated in unfractionated cell cultures from healthy control cows after exposure to M. avium subsp. paratuberculosis infection as compared to noninfected cell cultures. A similar increase in NO due to the addition of M. avium subsp. paratuberculosis to cell cultures was also noted for clinically infected cows, with further increases noted when in vitro infection was accompanied by the addition of exogenous IFN-gamma. In contrast, increased NO was observed in cultures from subclinically infected cows only in the presence of both M. avium subsp. paratuberculosis and IFN-gamma. Alternatively, nonspecific stimulation with LPS from E. coli O11:B4-W resulted in an upregulation of NO production in all infected groups at different time points. Finally, the in vitro exposure to inhibitory cytokines such as IL-10 and TGF-beta prior to M. avium subsp. paratuberculosis infection or LPS stimulation resulted in the downregulation of this inflammatory mediator (NO) in mediator (NO) in all experimental groups at all time points. In summary, NO production was higher in cells isolated from subclinically infected cows compared to clinically infected or healthy controls, and this effect was augmented when M. avium subsp. paratuberculosis infection was accompanied by the presence of exogenous IFN-gamma.