An innovative study at the Research Institute of the MUHC has brought us closer to an explanation for Crohn’s disease

Montreal, July 9th 2009 – Twenty-five per cent of Crohn’s disease patients have a mutation in what is called the NOD2 gene, but it is not precisely known how this mutation influences the disease. The latest study by Dr. Marcel Behr, of the Research Institute of the MUHC and McGill University, has provided new insight into how this might occur. The study will be published on July 9th in the Journal of Experimental Medicine.

When the NOD2 gene functions normally, it codes for a receptor that will recognize invading bacteria and then trigger the immune response. This study demonstrates that the NOD2 receptor preferentially recognizes a peptide called N-glycolyl-MDP, which is only found in a specific family of bacteria called mycobacteria. When mycobacteria invade the human body, they cause an immediate and very strong immune response via the NOD2 receptor.

“Now that we have a better understanding of the normal role of NOD2, we think that a mutation in this gene prevents mycobacteria from being properly recognized by the immune system,” explained Dr. Behr. “If mycobacteria are not recognized, the body cannot effectively fight them off and then becomes persistently infected.”

Researchers were already aware of the relationship between mycobacteria and Crohn’s disease, but they did not know whether the presence of bacteria was a cause or a consequence of the disease. This new discovery associates the predisposition for Crohn’s disease with both the NOD2 mutation and the presence of mycobacteria, but researchers must still determine the precise combination of these factors to understand how the disease develops.

More research is required to establish a complete explanation. From this, it is expected that new therapeutic approaches that fight the cause of Crohn’s disease may be developed

They found that 68.1% of US Dairy Herds are infected with Mycobacterium avium subspecies paratuberculosis (MAP), an obligate pathogen which causes Inflammatory Bowel Disease (Johne’s Disease) in cattle, sheep, goats and other food animals. Paratuberculosis is present in milk from infected animals, and is known to survive commercial pasteurization. Live MAP has been cultured from US retail milk supplies.

Mycobacterum avium subspecies paratuberculosis is suspected of causing the human Inflammatory Bowel Disease known as Crohn’s Disease, and there is mounting scientific and medical evidence that at least some proportion of Crohn’s Disease is caused by MAP. If MAP does cause Crohn’s Disease, then it is certain that the primary route of transmission of MAP to humans is through contaminated dairy and meat products.

The NAHMS study also found evidence for MAP in 95% of large dairy herds, an unprecedented figure which shows that MAP is spreading rapidly and unchecked through US herds of food animals. Not only is the milk from these cattle infected with MAP, but their carcasses, which are used to make ground beef, contain billions of MAP organisms.

The testing method used to detect paratuberculosis is known to underestimate the true prevalence. To quote the NAHMS report: “Although environmental sampling is an effective method of detecting operations infected with MAP, it will not detect all infected operations. Thus, reported percentages will be less than the true prevalences.”

The full report is available from the USDA Animal and Plant Inspection Service (APHIS) website.

Johne’s Disease on U.S. Dairies, 1991–2007.

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Association between CARD15/NOD2 gene polymorphisms and paratuberculosis infection in cattle
Pinedo, P.J., Buergelt, C.D., Donovan, G.A., Melendez, P., Morel, L., Wud, R., Langaee, T.Y., Rae, D.O. (2009)
Veterinary Microbiology, 134, 346-352
http://www.ncbi.nlm.nih.gov/pubmed/18926647

Paratuberculosis represents a major problem in farmed ruminants and at the present is considered a potential zoonosis. The disease is caused by Mycobacterium avium subsp. paratuberculosis, and susceptibility to infection is suspected to have a genetic component. Caspase recruitment domain 15 (CARD15) gene encodes for a cytosolic protein implicated in bacterial recognition during innate immunity. Crohn’s disease (CD) is an idiopathic inflammatory bowel disease in humans comparable in many features to bovine paratuberculosis involving an abnormal mucosal immune response. The association between mutations in the CARD15 gene and increased risk of Crohn’s disease has been described. The objective of this candidate gene case-control study was to characterize the distribution of three polymorphisms in the bovine CARD15 gene and test their association with paratuberculosis infection in cattle. Three previously reported single nucleotide polymorphisms (E2[-32] intron 1; 2197/C733R and 3020/Q1007L) were screened for the study population (431 adult cows). The statistical analysis resulted in significant differences in allelic frequencies between cases and controls for SNP2197/C733R (P < 0.001), indicating a significant association between infection and variant allele. In the analysis of genotypes, a significant association was also found between SNP2197/ C733R and infection status (P < 0.0001); cows with the heterozygous genotype were 3.35 times more likely to be infected than cows with the reference genotype (P = 0.01). Results suggest a role for CARD 15 gene in the susceptibility of cattle to paratuberculosis infection. These data contribute to the understanding of paratuberculosis, suggest new similarities with Crohn’s disease and provide new information for the control of bovine paratuberculosis.

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Abnormalities in the handling of intracellular bacteria in Crohn’s disease: a link between infectious etiology and host genetic susceptibility.
Glasser AL, Darfeuille-Michaud A.
Arch Immunol Ther Exp (Warsz). 2008 Jul-Aug;56(4):237-44.
http://www.ncbi.nlm.nih.gov/pubmed/18726145

The etiology of Crohn’s disease (CD) is still poorly understood, but recent advances have highlighted the importance of the innate immune system and the critical relationship between the gut flora and the intestinal mucosa. Several combinations of genetic factors predisposing to CD have been described, with the most significant replicable associations including genes for intracellular receptors of bacterial cell walls (NOD2/CARD15) and for bacterial clearance and antigen processing via autophagy (ATG16L1 and IRGM). One theoretical link between susceptibility genes NOD2/CARD15, ATG16L1, and IRGM is that CD is primarily induced by the presence of a dysfunctional immunological response to persistent infection by intracellular bacterial pathogens such as Mycobacterium avium subspecies paratuberculosis or adherent-invasive Escherichia coli, both first- rank candidates on the basis of host genetic susceptibility, which concerns impaired functions in the defense against intracellular bacteria.

Fecal Transfusion – a treatment for UC?

http://aem.asm.org/cgi/content/abstract/AEM.00981-08v1
http://www.ncbi.nlm.nih.gov/pubmed/18676709

Antibacterial activities of 18 naturally-occurring compounds (including essential oils and some of their isolated constituents, apple and green tea polyphenols and other plant extracts) against three strains of Mycobacterium avium subspecies paratuberculosis (Map), a bovine isolate NCTC 8578, a raw milk isolate 806R and a human isolate ATCC 43015, were evaluated using a macrobroth susceptibility testing method. Map was grown in 4 ml Middlebrook 7H9 broth containing 10% OADC, 0.05% Tween 80 (or 0.2% glycerol) and 2 microg/ml mycobactin J supplemented with five concentrations of each test compound. The changes in optical density (OD) of the cultures at 600 nm as a measure of CFUs was recorded at intervals over an incubation period of 42 days at 37 degrees C. Six of the compounds were found to inhibit the growth of Map. The most effective compound was trans-cinnamaldehyde with a minimum inhibitory concentration (MIC) of 25.9 microg/ml, then cinnamon oil (26.2 microg/ml), oregano (68.2 microg/ml), carvacrol (72.2 microg/ml), 2,5-dihydroxybenzaldehyde (74 microg/ml), and 2- hydroxy-5-methoxybenzaldehyde (90.4 microg/ml). With the exception of carvacrol, a phenolic compound, three of the four most active compounds are aldehydes, suggesting that the structure of the phenolic group or aldehyde group may be important to the antibacterial activity. No difference in compound activity was observed between the three Map strains studied. Possible mechanisms of the antimicrobial effects are discussed.

You can watch the program online here (but unfortunately in very poor video quality, although the audio is fine). On the first page below, click the link “Watch the last show”.

http://www.bbc.co.uk/wales/programmes/sites/weekinweekout/index.shtml
http://www.bbc.co.uk/wales/programmes/sites/weekinweekout/updates/080325_crohns_disease.shtml

http://www.paratuberculosis.org/pubs/proc9/abst185f_o4.htm

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BACKGROUND:

We have shown that the “immuno-modulators” methotrexate and 6-MP and the “anti-inflammatory” 5-ASA inhibit MAP growth (www.PLoSONE.org) and concluded that their most plausible mechanism of action in several idiopathic diseases is as antiMAP antibiotics. Thalidomide is an “immunomodulator” used in multiple “auto-immune” and “inflammatory” diseases and the mycobacterial diseases leprosy and tuberculosis. We now test the hypothesis that thalidomide inhibits MAP growth.

METHODS

Thalidomide (+-) and (+) and (-) and its two components, phthalimide and 1-hydroxy 2,6 piperidine dione (HPD) were evaluated in culture of two strains each of MAP (ATCC 19698 [bovine] & Dominic [human]) and M. avium subspecies avium (ATCC 25291 & 101.) We used a radiometric (14CO2 Bactec(R)) detection system. Inhibition is indicated by “percent decrease in cumulative Growth Index” (%-DcGI) from control.

RESULTS:

Phthalimide has no dose dependent inhibition on any strain. There was no dose dependent inhibition on either M. avium strain with thalidomide or its components. With the two MAP strains, there is dose dependent inhibition with thalidomide (+1); Dominic (31%-DcGI) and ATCC 19698 (26%-DcGI) at 64microg/ml. Thalidomide (+) is more inhibitory than (-). HPD is, on a weight for weight basis, the most inhibitory agent evaluated; Dominic (46%-DcGI) and ATCC 19698 (44%-DcGI at 64microg/ml)

CONCLUSIONS:

We show in vitro heretofore-undescribed inhibition of MAP growth by racaemic thalidomide. Thalidomide (+) is more potent than (-). Of thalidomide’s two moieties, phthalimide has no antiMAP activity and HPD is the active component in inhibiting MAP growth. We suggest that since 1942, initially with 5-ASA, the medical profession has unknowingly been treating MAP infections. These data are compatible with our concern that MAP is zoonotic. We conclude that all idiopathic “autoimmune” and “inflammatory” diseases, empirically treated with medications that we show are active against MAP, should now be evaluated for MAP as the etiological agent.

As with previous ICP, the number of papers presented on the relationship between Crohn’s Disease and Mycobacterium Paratuberculosis has grown, as knowledge of this complex organism and its potential to cause disease in humans, has grown.

The list of 9ICP presentations in the “Public Health” segment of the Colloquium are listed here

http://www.paratuberculosis.org/pubs/proc9/section6.htm

As acceptance of the relationship between MAP and CD grows, related papers are now being presented outside of the dedicated “Public Health” segment. The following paper discusses how the pathogenetic mechanisms of paratuberculosis in Johnes Disease and Crohn’s Disease can be compared in order to increase understanding of both; it was presented in the “Pathogenesis and Immunology” segment.

Role of Mycobacterium avium subsp. paratuberculosis in the pathogenesis of Crohn’s disease
http://www.paratuberculosis.org/pubs/proc9/abst4a.htm

Also of interest is the growing evidence that Mycobacterium avium subsp paratuberculosis may be a cause of Type-1 diabetes.

Association of Mycobacterium avium subsp. paratuberculosis with Type-1 diabetes, a possible trigger
http://www.paratuberculosis.org/pubs/proc9/abst181f_o3.htm

Paratuberculosis and Type I Diabetes -Mapping the TRIGR-
http://www.paratuberculosis.org/pubs/proc8/abst3b_o20.htm

http://www.paratuberculosis.org/pubs/proc9/abst182f_o6.htm

As noted by the authors, “These data may partially explain the paradoxical response of Crohn’s disease patients infected with M. paratuberculosis to treatment with immunosuppressive thiopurine drugs i.e. they do not worsen with anti-inflammatory treatment as would be expected with a microbial etiologic pathogen.”
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The in vitro susceptibility of human and bovine-origin Mycobacterium paratuberculosis to the thiopurine drugs 6-mercaptopurine (6-MP) and azathioprine (AZA) were established using conventional plate counting methods and the MGIT 960 ParaTB culture system. Both 6-MP and AZA had antibacterial activity against M. paratuberculosis; isolates from Crohn’s disease patients tended to be more susceptible than were bovine-origin isolates. Isolates of Mycobacterium avium, used as controls, were generally resistant to both AZA and 6-MP even at high concentrations (>=64.0 microg/mL). Among rapidly growing mycobacteria, M. phlei was susceptible to 6-MP and AZA whereas M. smegmatis strains were not. AZA and 6-MP limited the growth of, but did not kill, M. paratuberculosis in a dose-dependent manner. Anti-inflammatory drugs in the sulfonamide family (sulfapyridine, sulfasalazine, and 5-amino- salycilic acid (mesalamine)) had little or no antibacterial activity against M. paratuberculosis. The conventional antibiotics azithromycin and ciprofloxacin (CPX) used as control drugs were bactericidal for M. paratuberculosis, exerting their killing effects on the organism relatively quickly. Simultaneous exposure of M. paratuberculosis to 6- MP and CPX resulted in significantly higher CFUs as compared to use of CPX alone. These data may partially explain the paradoxical response of Crohn’s disease patients infected with M. paratuberculosis to treatment with immunosuppressive thiopurine drugs i.e. they do not worsen with anti-inflammatory treatment as would be expected with a microbial etiologic pathogen. These findings also should influence the design of therapeutic trials to evaluate antibiotic treatments of Crohn’s disease: azathioprine drugs may confound interpretation of data on therapeutic responses both antibiotic-treated and control groups.

http://www.liv.ac.uk/newsroom/press_releases/2007/12/crohns-disease.htm

Crohn’s is a condition that affects one in 800 people in the UK and causes chronic intestinal inflammation, leading to pain, bleeding and diarrhoea.

The team found that a bacterium called Mycobacterium paratuberculosis releases a molecule that prevents a type of white blood cell from killing E.coli bacteria found in the body. E.coli is known to be present within Crohn’s disease tissue in increased numbers.

It is thought that the Mycobacteria make their way into the body’s system via cows’ milk and other dairy products. In cattle it can cause an illness called Johne’s disease – a wasting, diarrhoeal condition. Until now, however, it has been unclear how this bacterium could trigger intestinal inflammation in humans.

Professor Jon Rhodes, from the University’s School of Clinical Sciences, explains: “Mycobacterium paratuberculosis has been found within Crohn’s disease tissue but there has been much controversy concerning its role in the disease. We have now shown that these Mycobacteria release a complex molecule containing a sugar, called mannose. This molecule prevents a type of white blood cells, called macrophages, from killing internalised E.Coli.”

Scientists have previously shown that people with Crohn’s disease have increased numbers of a ‘sticky’ type of E.coli and weakened ability to fight off intestinal bacteria. The suppressive effect of the Mycobacterial molecule on this type of white blood cell suggests it is a likely mechanism for weakening the body’s defence against the bacteria.

Professor Rhodes added: “We also found that this bacterium is a likely trigger for a circulating antibody protein (ASCA) that is found in about two thirds of patients with Crohn’s disease, suggesting that these people may have been infected by the Mycobacterium.”

The team is beginning clinical trials to assess whether an antibiotic combination can be used to target the bacteria contained in white blood cells as a possible treatment for Crohn’s disease.

The research was funded by Core and the Medical Research Council and is published in Gastroenterology.