Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2009
Publication Date: 7/30/2009
Citation: Waters, W.R., Palmer, M.V., Nonnecke, B.J., Thacker, T.C., Estes, D.M., Larsen, M.H., Jacobs, W.R., Andersen, P., Mcnair, J., Minion, F.C., Lyashchenko, K.P., Hewinson, R.G., Vordermeier, H.M., Sacco, R.E. 2009. Signal Regulatory Protein alpha (SIRPalpha)+ Cells in the Adaptive Response to ESAT-6/CFP-10 Protein of Tuberculous Mycobacteria. PLoS One [serial online]. 4(7):e6414. Available: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0006414.
Interpretive Summary: Despite highly successful eradication efforts in several countries, tuberculosis of cattle remains a serious health concern worldwide. In addition, recent outbreaks of tuberculosis in Michigan, Minnesota, California, and New Mexico demonstrate that the disease is far from eliminated from the United States. Improved techniques are needed for detection of infected cattle as well as improved control strategies (e.g., vaccines). To develop improved tests and vaccines, it is beneficial to first understand the nature of bovine immune responses to tuberculosis infection. In this study, the immune response of cattle to a key diagnostic reagent (i.e., used in tuberculosis specific tests) was characterized. This basic information will be useful for development of improved tests and vaccines for cattle.
Technical Abstract: Early secretory antigenic target-6 (ESAT-6) and culture filtrate protein-10(CFP-10) are co-secreted proteins of Mycobacterium tuberculosis complex mycobacteria (includes M. bovis, the zoonotic agent of bovine tuberculosis) involved in phagolysosome escape of the bacillus and, potentially, in the efficient induction of granulomas. Upon tuberculosis infection, multi-nucleate giant cells are elicited, likely as a response aimed at containing mycobacteria. In tissue culture models, signal regulatory protein (SIRP)a (also referred to as macrophage fusion receptor or CD172a) is essential for multi-nucleate giant cell formation. In the present study, ESAT-6/CFP-10 complex and SIRPa interactions were evaluated with samples obtained from calves experimentally infected with M. bovis. Peripheral blood CD172a+ (SIRPa-expressing) cells from M. bovis-infected calves expanded CD172a+ upon in vitro stimulation with ESAT-6/CFP-10 (either as a fusion protein or a peptide cocktail), but not with cells from animals receiving M. bovis strains lacking ESAT-6/CFP-10 (i.e, M. bovis BCG or M. bovis DRD1). Sorted CD172a+ cells from these cultures had a dendritic cell / macrophage morphology, bound fluorescently-tagged rESAT-6:CFP-10, bound and phagocytosed live M. bovis BCG, and co-expressed CD11c, DEC-205, CD44, MHC II, CD80/86 (a subset also co-expressed CD11b or CD8a). Intradermal administration of rESAT-6:CFP-10 into tuberculous calves elicited a delayed type hypersensitive response consisting of CD11c+, CD172a+, and CD3+ cells, including CD172a-expressing multi-nucleated giant cells. These findings demonstrate the ability of ESAT-6/CFP-10 to specifically expand CD172a+ cells, bind to CD172a+ cells, and induce multi-nucleated giant cells expressing CD172a; thereby, supporting granuloma formation.