Submitted to: Infection and Immunity
Publication Type: Trade journal
Publication Acceptance Date: 6/21/2005
Publication Date: 10/1/2005
Citation: Maue, A., Waters, W.R., Davis, W.C., Palmer, M.V., Minion, F.C., Estes, D.M. 2005. Analysis of Immune Responses Directed toward a Recombinant Early Secretory Antigenic Target Six-Kilodalton Protein-Culture Filtrate Protein 10 Fusion Protein in Mycobacterium bovis-Infected Cattle. Infection and Immunity. 73(10):6659-67. 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, California, Texas, and New Mexico demonstrate that the disease is far from eliminated from the United States. Improved techniques are needed for detection of infected cattle. To develop improved tests, it is beneficial to first understand the immune response to infection. In this study, specific host responses by cattle to tuberculosis infection were determined. Specifically, surface molecules associated with activation of white blood cells upon encounter with the pathogen (i.e., Mycobacterium bovis) were defined. Knowledge obtained from this study will assist in the development of new reagents and methods for the detection of tuberculosis of cattle.
Technical Abstract: ABSTRACT Cell-mediated immune responses are critical for protective immunity to mycobacterial infections. Recent progress in defining mycobacterial antigens has determined that region of difference-1 (RD1) gene products induce strong T cell responses, particularly the early secretory antigenic target 6-kDa (ESAT-6) protein and culture filtrate protein 10 (CFP10). However, comprehensive analysis of the immune response towards these antigens is incompletely characterized. To evaluate recall responses to ESAT-6 and CFP10, peripheral blood mononuclear cells (PBMC) from M. bovis-infected cattle were stimulated in vitro with a recombinant ESAT-6:CFP10 (rESAT-6:CFP10) fusion protein and compared to responses induced by M. bovis-derived purified protein derivative. Following antigenic stimulation, activation marker expression was evaluated. Significant proliferative responses (p < 0.05) were evident in CD4+, CD8+, IgM+ and CD172a+ cell subsets after six day culture. Expression of CD25 and CD26 was increased (p < 0.05) on CD4+, CD8+ and '' TCR+ cells. CD4+ and CD8+ cells also exhibited significant changes (p < 0.05) in expression of CD45 isoforms. Using a flow cytometry-based proliferation assay, it was determined that CD45R expression is downregulated (p < 0.05) and that CD45RO expression is upregulated (p < 0.05) on proliferating (i.e. activated) CD4+ cells. Collectively, data indicate that recall immune responses directed toward rESAT-6:CFP10 fusion protein or PPD are comparable and that recall to mycobacterial antigens correlates with a CD45RO+ phenotype.