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

Abstract

The objective of this study was to develop an intestinal model of Mycobacterium avium subspecies paratuberculosis (Map) infection in the calf for evaluation of mucosal pathology and local and systemic immunologic responses. Map was inoculated into Peyer's patches of young calves using a right flank surgical approach in standing calves to exteriorize the ileocecal junction. Inoculum doses ranging from 10 3 to 10 9 colony-forming units of strain K10 Map were injected through the serosal surface into Peyer's patches of the distal ileum near the ileocecal valve. Fecal samples were collected for culture from each calf weekly until termination of the study. Calves were necropsied at 7, 30, 60, and 90 days after infection, when inoculation sites, lymph nodes, spleen, and peripheral blood were collected for evaluation. Ileocecal lymph nodes were consistently colonized by Map in the 10 5 to 10 9 groups. The ileocecal valve was also colonized in 10 7 and 10 9 groups. This correlated with fecal culture results as infected calves intermittently shed Map in their feces throughout the study. Granulomatous lesions with giant cells and acid-fast bacilli at the ileocecal junction, ileocecal lymph nodes, and lamina propria of high-dose animals (10 7 and 10 9 ) were identified from each time point. Flow cytometry was used to detect antigen-specific production of interferon-g and interleukin-4 locally (ileocecal lymph node) and systemically (peripheral blood mononuclear cells), which defined distinct immunologic profiles in low-dose and high-dose calves. This study demonstrates intestinal Map infection via Peyer's patch inoculation, a novel model with many shared features of natural Map infection.

Metabolomic Profiling in Cattle Experimentally Infected with Mycobacterium avium subsp. paratuberculosis

“…Although the same metabolites discriminated LD and HD infected cattle from negative controls; therefore, dose did not affect metabolomic changes, it is noteworthy that immune-related outcomes are typically influenced by dose in parasitic [31], viral [32] and bacterial [33] infections. Moreover, whereas all treatment groups of this trial were purposely allocated into 2 independent runs, differentiation of infected and non-infected animals was still possible despite added seasonal variation to the metabolite profiles.…”

Host Responses to Persistent Mycobacterium avium Subspecies paratuberculosis Infection in Surgically Isolated Bovine Ileal Segments

“…Furthermore, dissemination of M. avium subsp. paratuberculosis to mesenteric lymph nodes is a common feature of natural Johne's disease (39) and has been reported following experimental infection by either the oral route (40,41) or injection into the intestinal wall (42). Thus, the absence of detectable M. avium subsp.…”

Systems Biology Analysis of Gene Expression during In Vivo Mycobacterium avium paratuberculosis Enteric Colonization Reveals Role for Immune Tolerance

“…A key role of intestinal mucosal epithelia is barrier function, which prevents colonization or invasion by foreign microorganisms. However, in Johne's disease, MAP invade M cells, enterocytes, dendritic cells and macrophages, and are capable of resisting host defenses and multiply to reach very high intracellular numbers leading to chronic granulomatous lesions [31], [32]. In infected subclinical and clinically affected animals, systemic immune response is achieved.…”