Internalization-dependent recognition ofMycobacterium aviumssp.paratuberculosisby intestinal epithelial cells

Abstract

SummaryMycobacterium avium ssp. paratuberculosis (MAP) is the causative agent of Johne's disease, a highly prevalent chronic intestinal infection in domestic and wildlife ruminants. The microbial pathogenesis of MAP infection has attracted additional attention due to an association with the human enteric inflammatory Crohn's disease. MAP is acquired by the faecal-oral route prompting us to study the interaction with differentiated intestinal epithelial cells. MAP was rapidly internalized and accumulated in a late endosomal compartment. In contrast to other opportunistic mycobacteria or M. bovis, MAP induced significant epithelial activation as indicated by a NF-kBindependent but Erk-dependent chemokine secretion. Surprisingly, MAP-induced chemokine production was completely internalizationdependent as inhibition of Rac-dependent bacterial uptake abolished epithelial activation. In accordance, innate immune recognition of MAP by differentiated intestinal epithelial cells occurred through the intracellularly localized pattern recognition receptors toll-like receptor 9 and NOD1 with signal transduction via the adaptor molecules MyD88 and RIP2. The internalization-dependent innate immune activation of intestinal epithelial cells is in contrast to the stimulation of professional phagocytes by extracellular bacterial constituents and might significantly contribute to the histopathological changes observed during enteric MAP infection.

Direct Inoculation of Mycobacteriumavium Subspecies Paratuberculosis Into Ileocecal Peyer’s Patches Results in Colonization of the Intestine in a Calf Model

“…Regardless, a clear advantage of intestinal loop, ileal cannulation, and oral infection models is the ability to potentially investigate interactions of live Map with intestinal epithelia and/or M cells, which are proposed to play a significant but incompletely explored role in the pathogenesis of natural infection. 15 A unique and significant advantage of the experimental system reported here is that we have described a method to accelerate the pathogenesis of intestinal Map infection via direct delivery of a known infectious dose to the ileocecal valve, the proposed natural infection site in young calves. An objective of the current study was to develop a model resulting in consistent intestinal Map infection, and although this was successfully achieved, we did not observe classic lesions or clinical signs of naturally occurring disease in cattle such as diffuse granulomatous enteritis leading to chronic diarrhea and emaciation.…”

Peyer's Patch-Deficient Mice Demonstrate ThatMycobacterium aviumsubsp.paratuberculosisTranslocates across the Mucosal Barrier via both M Cells and Enterocytes but Has Inefficient Dissemination

“…However, a recent study with goat kids suggested that M. avium subsp. paratuberculosis enters the intestinal mucosa, translocating through enterocytes (20). By using B-cell knockout mice deficient in Peyer's patches, it was observed that M. avium subsp.…”

“…In addition, work in vitro showed that M. avium subsp. paratuberculosis can invade bovine kidney epithelial (17) and murine intestinal epithelial (20) cells efficiently. Mycobacterium avium subsp.…”

No Holes Barred: Invasion of the Intestinal Mucosa by Mycobacterium avium subsp. paratuberculosis

“…M. avium subsp. paratuberculosis shows a strong affinity for the apical surface of enterocytes and is efficiently internalized (16). Furthermore, the uptake of M. avium subsp.…”

“…paratuberculosis invades the host (15)(16)(17). It is possible that Peyer's patches and M cells are not well developed in the neonatal calf, because of a lack of maturation and antigen exposure (18).…”