TLR4, IL10RA, and NOD2 mutation in paediatric Crohn’s disease patients: an association with Mycobacterium avium subspecies paratuberculosis and TLR4 and IL10RA expression

Abstract

Mycobacterium avium subspecies paratuberculosis (MAP) has been implicated in the pathogenesis of Crohn's disease (CD). The role of CD susceptibility genes in association with these microbes is not known. Sixty-two early onset paediatric CD patients and 46 controls with known MAP status were analysed for an association with 34 single nucleotide polymorphisms (SNPs) from 18 CD susceptibility genes. Functional studies on peripheral blood mononuclear cells (PBMCs) were conducted on 17 CD patients with known CD mutations to assess IL-6, IL-10, and TNF-α expression upon stimulation with MAP precipitated protein derivative (PPD) and lipopolysaccharide (LPS). In addition, surface expression of IL10R and TLR4 on resting B cells, NK cells, T cells, and monocytes was assessed. A mutation in TLR4 (rs4986790) and IL10RA (rs22291130) was significantly associated with MAP-positive CD patients compared to MAP-negative CD patients (27.6 vs. 6.1 %, p = 0.021, and 62.1 vs. 33.3 %, p = 0.024, respectively). PPD and LPS significantly increased IL-6, IL-10, and TNF-α production in PBMCs. IL-10 and TNF-α production were significantly lower in a subgroup of CD patients (5/12) with a known NOD2 mutation. Receptor for IL-10 was significantly higher expressed on NK cells (CD56low) and on NK T cells harbouring a NOD2 mutations compared to wildtype cells (p = 0.031 and 0.005, respectively). TLR4 was significantly higher expressed on NK cells (CD56high) harbouring a NOD2 mutations compared to wildtype cells (p = 0.038).

Impact of Ethnicity, Geography, and Disease on the Microbiota in Health and Inflammatory Bowel Disease

“…39 Our group has previously shown that different microbes are associated with different genetic determinants, suggesting that CD may result from a combination of specific microbial and genetic factors. 40,41 Furthermore, genetic abnormalities that predispose individuals to IBD have been shown to differ substantially between the West and the East. 42 More studies that link specific microbial patterns with ethnicity and genetic abnormalities are now required.…”

Genetic variants associated with Crohn's disease

“…A comprehensive list of the main genetic variants in CD is summarized in Table 1. In summary, the mutational variants in CD further describe a defect in bacterial sensing, as mentioned by Wagner et al,9 and an exaggerated response of the intestinal immune system.…”

“…Currently, our genetic knowledge of CD is applied to understanding the natural history of the disease, describing racial predominance, predicting early onset stricturing and fistulizing, and determining location and overall severity of disease. Wagner et al recently described an association between mutations in toll-like receptor (TLR) 4 (rs4986790) and interleukin 10 receptor, alpha subunit (rs22291130) with Mycobacterium avium subspecies paratuberculosis positive CD patients,9 further implicating the role of microbial triggers and aberrant genetic responses in the immune system. This genetic data is helpful information that will possibly lead to the ultimate discovery of etiologies for the disease.…”

Crohn's disease and sarcoidosis in siblings: follow-up of a published report with a new case and brief review of the literature

“…The fact that both were recognised as ‘new’ entities by their distinction from tuberculosis has focused on sarcoidosis22–24 and Crohn's disease25 26 alike a search for mycobacteria as precipitants: a search which has been rewarded with findings that have identified an association without the evidence to prove it causative. From Japan, it has been reported that Propionibacterium acnes is the only microorganism to have been cultured from sarcoid lesions, persisting (like the AIEC in Crohn's disease) in a cell-wall-deficient form, which here too was found to provoke a granulomatous inflammatory reaction 27…”