Disease state influences the presence of macrophages and Mycobacterium avium subsp. paratuberculosis in bovine intestinal tissue

Authors: JENVEY, CAITLIN - US Department Of Agriculture (USDA); HOSTETTER, J - Iowa State University; Bannantine, John; Stabel, Judith

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/1/2017
Publication Date: 12/3/2017
Citation: Jenvey, C.J., Hostetter, J.M., Bannantine, J.P., Stabel, J.R. 2017. Disease state influences the presence of macrophages and Mycobacterium avium subsp. paratuberculosis in bovine intestinal tissue. Meeting Abstract. 193/109.

Interpretive Summary: Confocal microscopy is a widely used method utilizing fluorescence to identify the presence of cell types within tissues and/or bacterial or viral pathogens. This method has been used successfully to detect the presence of bacterial pathogens such as mycobacteria and to correlate that presence with the pathogenesis of disease. Understanding the pathogenesis of the disease and the host immune response to infection will allow us to develop improved diagnostic tools and vaccines. In the present study, mid-ileal tissue from naturally infected cattle was stained for macrophage and Mycobacterium avium subsp. paratuberculosis (MAP) and visualized by confocal microscopy. The number of macrophages and MAP present, as well as where they were located within the tissue was assessed for naturally infected cows as well as control uninfected cows and compared. The number of macrophages and MAP associated with macrophages increased with progression of disease from subclinical to clinical status. These results provide critical information on the biology of MAP infection within the target tissue.

Technical Abstract: Johne’s disease is an enteric disease caused by the intracellular pathogen Mycobacterium avium subsp. paratuberculosis (MAP). Upon translocation from the lumen of the small intestine, mycobacteria have the ability to thwart innate defense mechanisms and persist within the macrophage. This study aimed to correlate the presence of macrophages and MAP in bovine mid-ileal tissue with stage of infection. Immunofluorescent (IF) labeling was performed on frozen bovine mid-ileal intestinal tissue collected from 28 Holstein dairy cows. Macrophages were labeled using a monoclonal anti-macrophage surface antigen (AM-3K) and MAP was labeled using a polyclonal rabbit heat-killed MAP antigen, with IF labeling visualized using a confocal microscope. Imaging software was used to quantify the surface area and intensity of IF labeling. The presence of macrophages within the mid-ileal tissue sections was higher for clinical cows, followed by subclinical cows and then uninfected control cows. Macrophages were present throughout the intestinal tissue in clinical cows, including the inner muscle layer, submucosa, crypt and villi ends, while presence of macrophages in both subclinical and control cows were limited to the submucosa and inner muscle layer. Clinical cows also demonstrated significantly higher MAP SA and macrophage and MAP co-localization SA, when compared to subclinical cows, and was present within the submucosa and crypt lamina propria, progressing into the villi ends in some clinical cows. Our findings indicate that number of macrophages increases with progression of disease, however, a significant number of the macrophages present are not associated with MAP. This suggests that although the bovine innate immune system is sufficiently stimulated to recruit macrophages in response to MAP invasion, the macrophages of clinically infected cows are ultimately unable to clear MAP, resulting in disease progression and clinical presentation.