Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/10/2010
Publication Date: 7/11/2010
Citation: Abdellrazeq, G.S., Rihan, H.M., Hamilton, M.J., Allen, A.J., Park, K.T., Bannantine, J.P., Stabel, J.R., Davis, W.C. 2010. Analysis of the Immune Response to a Major Membrane Protein of Mycobacterium avium subsp. paratuberculosis in Experimentally and Naturally Infected Cattle [abstract}. American Association of Dairy Science. Journal of Dairy Science. 93(E-Supplement 1):32. Interpretive Summary:
Technical Abstract: The 35 kDa major membrane protein (MMP) of Mycobacterium avium subsp. paratuberculosis (Map) is implicated in the pathogenesis of paratuberculosis (Ptb) in cattle. Understanding the immune response to MMP could reveal how Map evades immune elimination and provide information needed for developing a subunit vaccine. Flow cytometric (FC) analysis of the immune response to MMP in experimentally and naturally infected cattle revealed the immune response is slow to develop in comparison to the response to purified protein derivative (PPD) and soluble antigen (SAg). At 3 months post infection (PI), the CD4 proliferative response was low to all 3 antigens. At 12 months PI, the response was much higher to PPD and SAg. The CD8 proliferative response was similar but less than the CD4 response. In contrast, the CD4 and CD8 proliferative response in naturally infected cattle, at the preclinical and clinical stage of disease was vigorous to MMP, PPD, and SAg. The findings show the cell mediated immune response to Map develops slowly, as detected by FC, and is not diminished at any stage of infection. The underlying mechanisms of immune evasion remain to be elucidated. Studies in human tuberculosis suggest that regulatory T cells (Tr) interfere with T cell effector activity at the site of lesions thus accounting for the presence of a strong but ineffective immune response in patients with active tuberculosis. Further studies are needed to determine if Tr cells play a role in pathogenesis of Ptb and the response to MMP. Preliminary studies show Tr cells may comprise a large proportion of the CD4 cells in antigen stimulated cultures from animals at the clinical stage of infection.