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, JESSE - Iowa State University; Shircliff, Adrienne; Bannantine, John; Stabel, Judith

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/5/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Johne’s disease is an enteric disease caused by the intracellular pathogen Mycobacterium avium subsp. paratuberculosis (MAP). Upon ingestion of MAP, it is translocated across the intestinal epithelium and taken up by intestinal macrophages. Once ingested, MAP may be killed by macrophages, or depending upon the bacterial burden and immunological status of the animal, MAP may 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. The number 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, and the lamina propria around the crypts and in the villus tips, with progressively fewer macrophages in subclinical and control cows. Clinical cows also demonstrated significantly higher numbers of MAP and numbers of macrophages with intracellular MAP, when compared to subclinical cows. The IF labeling was present within the submucosa and lamina propria around the crypts, progressing into the villus tips in some clinical cows. Clinical cows demonstrated significantly higher MAP mean intensity, however, there was no difference in macrophage mean intensity in regards to stage of infection. Our findings indicate that number of macrophages increases with progression of disease, however, a significant number of the macrophages present in the mid-ileum 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.