Association between Mycobacterium avium subsp. paratuberculosis DNA in blood and cellular and humoral immune response in inflammatory bowel disease patients and controls.

Background: Similarities between human inflammatory bowel disease (IBD) and ruminant paratuberculosis have fueled a heated discussion on the role of Mycobacterium avium subsp. paratuberculosis (MAP) in the etiology of IBD.
Methods: In order to determine microbiological and immunological evidence of an association between MAP and IBD, blood from 222 inflammatory bowel disease patients and 80 healthy donors from the Basque Country (Spain) were subjected to nested PCR for MAP-specific insertion sequence IS900, interferon-gamma (IFN-gamma) release test with PPA-3 MAP antigen (IFNMAP) or phosphate-buffered saline (IFNPBS), and antibody ELISA with PPA-3 MAP antigen (ABMAP).
Results: Highly significant differences in the proportion of PCR-positive IBD patients (17%) and healthy controls (43%) as well as lower IFNMAP and higher ABMAP and IFNPBS responses were observed. Treatment was associated with decreases in IFNMAP and PCR-positive frequency.
Conclusions: These results indicate the existence of immune responses and treatment interactions with MAP that strongly support an etiological role of this agent in IBD.