2010 Annual Report
1a.Objectives (from AD-416)
Develop proteomic profiles of immune cells during the acute and chronic stages of mastitis and under different physiologic conditions known to be associated with immune suppression, such as parturition or nutritional imbalances. Identify proteins that are up- or down-regulated during these immunosuppressive states. Initiate studies into the function of these differentially regulated proteins.
Develop proteome profiles of mastitis-causing bacteria isolated from in vivo conditions and in bacteria grown in vitro or in lab counterparts that are not considered highly virulent. Identify proteins that are up- or down-regulated across bacteria studied in each ecological state and initiate studies into the role these differentially regulated proteins play in the establishment of chronic infection of the mammary gland.
Studies of immunomodulators to test their effectiveness at preventing disease by imposing them on a controlled reproducible mastitis challenge model. In the course of these studies we will discover and develop immunological reagents for the bovine and relevant wildlife animal species that will facilitate the discovery of innovative immunointervention strategies.
1b.Approach (from AD-416)
The approach to this research project is through experimentation discover new insights into the mechanisms of how the bovine dairy cow immune system fights diseases. Failure of the dairy cow immune system results in numerous diseases, of which mastitis is the predominate disease resulting in an economic burden to the industry. Our research will investigate the host immune system – pathogen interaction with the goal of enhancing immune function. To accomplish this goal we will study how immune system functions are affected by nutritional status. We will also study a newly described immune system function in the context of the dairy cow. In addition, we will investigate how pathogenic bacteria adapt to the in vivo environment and escape immune clearance. Finally, we will add to the large animal immunological reagent toolbox, to aid in study of immunological questions in dairy animals for the entire research community.
Mastitis is the most common disease that affects the dairy industry and is of prime economic impact to the producer. Our work is designed to better understand the basic mechanisms of the immune response to this disease and how we can help the dairy farmer better protect their herds. We have determined that vitamin D can affect bovine immune cell gene expression. However, unlike human immune cells, the affect of vitamin D on bovine immune cells may affect signaling mechanisms more than pathogen killing mechanisms. The first paper that links vitamin D to gene expression in bovine immune cells was published this year. In addition, we have submitted a second paper that demonstrates the up-regulation of the vitamin D pathway in immune cells isolated from milk from cows with clinical mastitis. We are also working on demonstrating the role of vitamin D in the adaptive immune system, elucidating the complex interaction between vitamin D usage by the innate immune system and the adaptive immune system.
Determination of the role of vitamin D in an infected mammary gland. ARS researchers at Ames, Iowa, have shown that vitamin D influences gene expression in bovine immune cells. We wanted to demonstrate the role of vitamin D in vivo during an infection, to determine vitamin D’s role in clearance of a pathogen. We have identified the specific immune cell type that expresses the enzyme that activates the precursor vitamin D. Cells of the monocyte lineage were shown to express ribonucleic acid for this important enzyme as well as having other genes with immunological functions upregulated. Determination of the proteins necessary for bacteria growth in milk could lead to rational therapeutics specific for environmental causes of mastitis in dairy cows.
Effect of vitamin D on bovine immune function. Human immune cells can convert vitamin D into a form that is able to alter gene expression and some of these genes are involved in antibacterial processes and can affect the ability of immune cells to kill bacteria. ARS researchers at Ames, Iowa, wished to determine if bovine immune cells could convert vitamin D into a form that will alter gene expression in bovine immune cells. The goal of this work is to determine the role of vitamin D in the health and well-being of a dairy cow and to determine that level of vitamin D necessary for full immune cell function. We have determined that bovine immune cells do convert vitamin D into a form that changes gene expression in the cells. This has been accomplished by using molecular biology techniques that allow us to determine that a number of genes that are affected by vitamin D and a number of genes that are not. In contrast to humans, none of the bovine genes that generate small antibacterial proteins are affected by vitamin D concentration, which may be an important difference between human and bovine innate immune function. This work has been published in the top dairy science journal. Better understanding of the basic functions of the immune system of the cow will help us to develop therapeutics to solve disease problems common to the dairy industry. This research may also give farmers information about how much supplementation of their animal feed is necessary for a fully functional immune system in cows.
Nelson, C.D., Reinhardt, T.A., Thacker, T.C., Beitz, D.C., Lippolis, J.D. 2010. Modulation of the Bovine Innate Immune Response by Production of 1alpha,25-Dihydroxyvitamin D3 in Bovine Monocytes. Journal of Dairy Science. 93(3):1041-1049.
Reinhardt, T.A., Lippolis, J.D., Mccluskey, B.J., Goff, J.P., Horst, R.L. 2011. Prevalence of Subclinical Hypocalcemia in Dairy Herds. The Veterinary Journal. 188:122-124.