The role of the fecal stream in Crohn's disease: an historical and analytic review

Parenteral Nutrition, Inflammatory Bowel Disease, and Gut Barrier: An Intricate Plot

Malnutrition poses a critical challenge in inflammatory bowel disease, with the potential to detrimentally impact medical treatment, surgical outcomes, and general well-being. Parenteral nutrition is crucial in certain clinical scenarios, such as with patients suffering from short bowel syndrome, intestinal insufficiency, high-yielding gastrointestinal fistula, or complete small bowel obstruction, to effectively manage malnutrition. Nevertheless, research over the years has attempted to define the potential effects of parenteral nutrition on the intestinal barrier and the composition of the gut microbiota. In this narrative review, we have gathered and analyzed findings from both preclinical and clinical studies on this topic. Based on existing evidence, there is a clear correlation between short- and long-term parenteral nutrition and negative effects on the intestinal system. These include mucosal atrophic damage and immunological and neuroendocrine dysregulation, as well as alterations in gut barrier permeability and microbiota composition. However, the mechanistic role of these changes in inflammatory bowel disease remains unclear. Therefore, further research is necessary to effectively address the numerous gaps and unanswered questions pertaining to these issues.

Elemental Diet as a Therapeutic Modality: A Comprehensive Review

Elemental diets have been employed for the management of various diseases for over 50 years, with several mechanisms mediating their beneficial effects. Yet, they are underutilized due to poor palatability, access, cost, and lack of awareness regarding their clinical efficacy. Therefore, in this review, we aimed to systematically search and review the literature to summarize the formulation variability, mechanisms of action, clinical applications, and tolerability of the elemental diets in gastrointestinal diseases. While large prospective trials are lacking, elemental diets appear to exhibit objective and subjective clinical benefit in several diseases, including eosinophilic esophagitis, eosinophilic gastroenteritis, inflammatory bowel diseases, small intestinal bacterial overgrowth, intestinal methanogen overgrowth, chemoradiotherapy-associated mucositis, and celiac disease. Although some data support the long-term use of elemental diets as an add-on supplement for chronic pancreatitis and Crohn's disease, most of the literature on exclusive elemental diets focuses on inducing remission. Therefore, subsequent treatment strategies for maintaining remission need to be adopted in chronic/relapsing diseases. Several mechanistic pathways were identified to mediate the effects of elemental diets, including food additive and allergen-free content, high passive absorption rate, and anti-inflammatory properties. High rates of intolerance up to 40% are seen in the trials where exclusive elemental diets were administered orally due to poor organoleptic acceptability; however, when tolerated, adverse events were rare. Other limitations of elemental diets are cost, access, and lifestyle/social restrictions. Moreover, judicious use is advised in presence of a concomitant restrictive food intake disorders. Elemental diets offer a potentially highly efficacious dietary intervention with minor side effects. Palatability, cost, access, and social restrictions are common barriers of use. Prospective clinical trials are needed to elucidate the role of elemental formulas in the management of individual diseases.

Postoperative Crohn's Disease Recurrence Risk and Optimal Biologic Timing After Temporary Diversion Following Ileocolic Resection

BACKGROUND

Postoperative recurrence of Crohn's disease (CD) is common. While most patients undergo resection with undiverted anastomosis (UA), some individuals also have creation of an intended temporary diversion (ITD) with an ileostomy followed by ostomy takedown (OT) due to increased risk of anastomotic complications. We assessed the association of diversion with subsequent CD recurrence risk and the influence of biologic prophylaxis timing to prevent recurrence in this population.

METHODS

This was a retrospective cohort study of CD patients who underwent ileocolic resection between 2009 and 2020 at a large quaternary health system. Patients were grouped by continuity status after index resection (primary anastomosis or ITD). The outcomes of the study were radiographic, endoscopic, and surgical recurrence as well as composite recurrence postoperatively (after OT in the ITD group). Propensity score-weighted matching was performed based on risk factors for diversion and recurrence. Multivariable regression and a Cox proportional hazards model adjusting for recurrence risk factors were used to assess association with outcomes. Subgroup analysis in the ITD group was performed to assess the impact of biologic timing relative to OT (no biologic, biologic before OT, after OT) on composite recurrence.

RESULTS

A total of 793 CD patients were included (mean age 38 years, body mass index 23.7 kg/m2, 52% female, 23% active smoker, 50% penetrating disease). Primary anastomosis was performed in 67.5% (n = 535) and ITD in 32.5% (n = 258; 79% loop, 21% end) of patients. Diverted patients were more likely to have been males and to have had penetrating and perianal disease, prior biologic use, lower body mass index, and lower preoperative hemoglobin and albumin (all P < .01). After a median follow-up of 44 months, postoperative recurrence was identified in 83.3% patients (radiographic 40.4%, endoscopic 39.5%, surgical 13.3%). After propensity score matching and adjusting for recurrence risk factors, no significant differences were seen between continuity groups in radiographic (adjusted hazard ratio [aHR], 1.32; 95% confidence interval [CI], 0.91-1.91) or endoscopic recurrence (aHR, 1.196; 95% CI, 0.84-1.73), but an increased risk of surgical recurrence was noted in the ITD group (aHR, 1.61; 95% CI, 1.02-2.54). Most (56.1%) ITD patients started biologic prophylaxis after OT, 11.4% before OT, and 32.4% had no postoperative biologic prophylaxis. Biologic prophylaxis in ITD was associated with younger age (P < .001), perianal disease (P = .04), and prior biologic use (P < .001) but not in recurrence (P = .12). Despite higher rates of objective disease activity identified before OT, biologic exposure before OT was not associated with a significant reduction in composite post-OT recurrence compared with starting a biologic after OT (52% vs 70.7%; P = 0.09).

CONCLUSIONS

Diversion of an ileocolic resection is not consistently associated with a risk of postoperative recurrence and should be performed when clinically appropriate. Patients requiring diversion at time of ileocolic resection are at high risk for recurrence, and biologic initiation prior to stoma reversal may be considered.

Transcriptome-wide association studies associated with Crohn's disease: challenges and perspectives

Crohn's disease (CD) is regarded as a lifelong progressive disease affecting all segments of the intestinal tract and multiple organs. Based on genome-wide association studies (GWAS) and gene expression data, transcriptome-wide association studies (TWAS) can help identify susceptibility genes associated with pathogenesis and disease behavior. In this review, we overview seven reported TWASs of CD, summarize their study designs, and discuss the key methods and steps used in TWAS, which affect the prioritization of susceptibility genes. This article summarized the screening of tissue-specific susceptibility genes for CD, and discussed the reported potential pathological mechanisms of overlapping susceptibility genes related to CD in a certain tissue type. We observed that ileal lipid-related metabolism and colonic extracellular vesicles may be involved in the pathogenesis of CD by performing GO pathway enrichment analysis for susceptibility genes. We further pointed the low reproducibility of TWAS associated with CD and discussed the reasons for these issues, strategies for solving them. In the future, more TWAS are needed to be designed into large-scale, unified cohorts, unified analysis pipelines, and fully classified databases of expression trait loci.

Surgical Planning in Penetrating Abdominal Crohn's Disease

Crohn's disease (CD) is increasing globally, and the disease location and behavior are changing toward more colonic as well as inflammatory behavior. Surgery was previously mainly performed due to ileal/ileocaecal location and stricturing behavior, why many anticipate the surgical load to decrease. There are, however, the same time data showing an increasing complexity among patients at the time of surgery with an increasing number of patients with the abdominal perforating disease, induced by the disease itself, at the time of surgery and thus a more complex surgery as well as the post-operative outcome. The other major cause of abdominal penetrating CD is secondary to surgical complications, e.g., anastomotic dehiscence or inadvertent enterotomies. To improve the care for patients with penetrating abdominal CD in general, and in the peri-operative phase in particular, the use of multidisciplinary team discussions is essential. In this study, we will try to give an overview of penetrating abdominal CD today and how this situation may be handled. Proper surgical planning will decrease the risk of surgically induced penetrating disease and improve the outcome when penetrating disease is already established. It is important to evaluate patients prior to surgery and optimize them with enteral nutrition (or parenteral if enteral nutrition is ineffective) and treat abdominal sepsis with drainage and antibiotics.

Nutritional Therapies and Their Influence on the Intestinal Microbiome in Pediatric Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic, autoimmune disorder of the gastrointestinal tract with numerous genetic and environmental risk factors. Patients with Crohn’s disease (CD) or ulcerative colitis (UC) often demonstrate marked disruptions of their gut microbiome. The intestinal microbiota is strongly influenced by diet. The association between the increasing incidence of IBD worldwide and increased consumption of a westernized diet suggests host nutrition may influence the progression or treatment of IBD via the microbiome. Several nutritional therapies have been studied for the treatment of CD and UC. While their mechanisms of action are only partially understood, existing studies do suggest that diet-driven changes in microbial composition and function underlie the diverse mechanisms of nutritional therapy. Despite existing therapies for IBD focusing heavily on immune suppression, nutrition is an important treatment option due to its superior safety profile, potentially low cost, and benefits for growth and development. These benefits are increasingly important to patients. In this review, we will describe the clinical efficacy of the different nutritional therapies that have been described for the treatment of CD and UC. We will also describe the effects of each nutritional therapy on the gut microbiome and summarize the strength of the literature with recommendations for the practicing clinician.

Fiber and Prebiotic Interventions in Pediatric Inflammatory Bowel Disease: What Role Does the Gut Microbiome Play?

The etiology of inflammatory bowel disease (IBD) is complex but is thought to be linked to an intricate interaction between the host’s immune system, resident gut microbiome and environment, i.e., diet. One dietary component that has a major impact on IBD risk and disease management is fiber. Fiber intakes in pediatric IBD patients are suboptimal and often lower than in children without IBD. Fiber also has a significant impact on beneficially shaping gut microbiota composition and functional capacity. The impact is likely to be particularly important in IBD patients, where various studies have demonstrated that an imbalance in the gut microbiome, referred to as dysbiosis, occurs. Microbiome-targeted therapeutics, such as fiber and prebiotics, have the potential to restore the balance in the gut microbiome and enhance host gut health and clinical outcomes. Indeed, studies in adult IBD patients demonstrate that fiber and prebiotics positively alter the microbiome and improve disease course. To date, no studies have been conducted to evaluate the therapeutic potential of fiber and prebiotics in pediatric IBD patients. Consequently, pediatric IBD specific studies that focus on the benefits of fiber and prebiotics on gut microbiome composition and functional capacity and disease outcomes are required.

The microbiome and inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic immune-mediated disease affecting the gastrointestinal tract. IBD consists of 2 subtypes: ulcerative colitis and Crohn disease. IBD is thought to develop as a result of interactions between environmental, microbial, and immune-mediated factors in a genetically susceptible host. Of late, the potential role of the microbiome in the development, progression, and treatment of IBD has been a subject of considerable interest and enquiry. Indeed, studies in human subjects have shown that the gut microbiome is different in patients with IBD compared with that in healthy control subjects. Other evidence in support of a fundamental role for the microbiome in patients with IBD includes identification of mutations in genes involved in microbiome-immune interactions among patients with IBD and epidemiologic observations implicating such microbiota-modulating risk factors as antibiotic use, cigarette smoking, levels of sanitation, and diet in the pathogenesis of IBD. Consequently, there has been much interest in the possible benefits of microbiome-modulating interventions, such as probiotics, prebiotics, antibiotics, fecal microbiota transplantation, and gene manipulation in the treatment of IBD. In this review we will discuss the role of the gut microbiome in patients with IBD; our focus will be on human studies.

Inflammatory bowel diseases: interrelationships between dietary vitamin D, exposure to UV radiation and the fecal microbiome

Introduction: Environmental factors and an altered fecal microbiome are believed to be central to the pathogenesis of inflammatory bowel diseases (IBD). Vitamin D and ultraviolet radiation (UVR) are environmental factors that are associated by several pathways, including changes to the gastrointestinal microbiome, with the development and course of IBD.Area covered: This review explores the interaction of vitamin D, and UVR, with the intestinal innate and adaptive immune systems, and how they may influence the gut microbiome and the subsequent development, and progression, of IBD.Expert opinion: Vitamin D and UVR both regulate innate and adaptive immunity through a combination of common and independent mechanisms, with the overall effect being the promotion of immune tolerance. Vitamin D, and to a lesser extent UVR, can modify the gastrointestinal microbiome either directly, or through immune-mediated mechanisms and this may explain the effect on intestinal inflammation in animal models of IBD and some clinical studies. Thus, both vitamin D and UVR exposure can be considered potential 'master regulators' of gastrointestinal immunity, fine-tuning the complex interaction between genetics, host immunity and the gut microbiome. Further research and increased understanding of environment-host interactions is essential to achieving the ultimate goal of preventing and curing IBD.

Difference in Pathomechanism Between Crohn's Disease and Ulcerative Colitis Revealed by Colon Transcriptome

BACKGROUND

We aim to identify the differences in colonic mucosal transcriptome between Crohn's disease (CD) and ulcerative colitis (UC) for a better understanding of the molecular pathology.

METHODS

Differentially expressed genes (DEG) in the colonic mucosa of CD and UC were identified with a global gene expression microarray dataset generated from the colon biopsies of CD and UC patients and normal controls. The DEGs were then processed to identify altered pathways and modularized DEGs and pathways. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis with an independent cohort of samples was performed to validate the microarray data.

RESULTS

At the pathway level, virus infection and autoimmune pathways were upregulated in CD but not in UC when compared with controls. Some of the relevant DEGs (such as TAP1 and TAP2) were elevated in both CD and UC, with CD exhibiting more pronounced elevations. Gene expression levels in viral infection pathways were correlated with those of autoimmune pathways. In contrast, pattern recognition-mediated innate immune pathways (TLR4 and TLR2) were significantly elevated in UC but not in CD. Similar results were observed with an independent cohort by qRT-PCR.

CONCLUSIONS

Our data support the hypothesis that viral infection induced autoimmunity may represent a pathomechanism for IBD, especially CD. However, pattern recognition-mediated innate immunity targeting microbiome may play a more important role in UC compared with CD. Our findings identified different intervention targets for CD and UC, which may lead to more effective treatments for IBD patients.

The Microbiome in Patients With Inflammatory Diseases

Microbial dysbiosis characterized by alterations in the structure and function of the gut microbiome has long been implicated in the pathogenesis of inflammatory bowel disease (IBD). To date, most human IBD microbiome studies are focused on microbial composition rather than function, however, with the latest technical advancements complemented by the rapidly dropping costs, studies focusing on the functional aspects of microbial dysbiosis are on the rise. Several compelling and complimentary pieces of evidence support the notion that the gut microbiome and their metabolites play an important role in the development of IBD. Data from preclinical studies overwhelmingly support the notion that changes in the gut microbiome causally underlie IBD pathogenesis. Hence, there is considerable interest in modulating the state and function of the gut microbiome to achieve therapeutic benefits. While the causal potential of the gut microbiome remains an active area of current research in the clinical setting, accumulating correlative evidence support the view that microbial dysbiosis parallels increased incidence of IBD. In this review, we intend to provide a brief overview of the current human IBD microbiome findings, describe the cause-effect relationships between the gut microbiome and IBD, and discuss the possibility of using microbiome-based approaches in the diagnosis, therapy, and management of disease. In addition, the potential role of microbiome-based interventions in the treatment of human IBD is also discussed.

Gut microbiota and IBD: causation or correlation?

A general consensus exists that IBD is associated with compositional and metabolic changes in the intestinal microbiota (dysbiosis). However, a direct causal relationship between dysbiosis and IBD has not been definitively established in humans. Findings from animal models have revealed diverse and context-specific roles of the gut microbiota in health and disease, ranging from protective to pro-inflammatory actions. Moreover, evidence from these experimental models suggest that although gut bacteria often drive immune activation, chronic inflammation in turn shapes the gut microbiota and contributes to dysbiosis. The purpose of this Review is to summarize current associations between IBD and dysbiosis, describe the role of the gut microbiota in the context of specific animal models of colitis, and discuss the potential role of microbiota-focused interventions in the treatment of human IBD. Ultimately, more studies will be needed to define host-microbial relationships relevant to human disease and amenable to therapeutic interventions.

Sequential Crohn's Ileitis, Ileosigmoidal Fistula, Segmental Sigmoid Polyposis, and Sigmoid Stricture: The Natural History

BACKGROUND

We have previously recognized segmental sigmoid polyps as an indicator of a fistula from Crohn's ileitis to the sigmoid or the proximal rectum. In the course of this study, we realized that many patients with this fistula had no sigmoid polyps, but the sigmoid was the site of marked inflammation and early or late stricture formation. Furthermore, in some patients with a stricture, the fistula was not recognized until the surgeon (or the pathologist) dissected an inflammatory peri-ileal and/or a perisigmoidal mass.In this study, we have sought to clarify the sequence of events by focusing on the segmental inflammation and the stricturing of the sigmoid so that its significance can be recognized as a local complication of the ileitis and the progression of its severity as opposed to arising sui generis.

MATERIALS AND METHODS

From our database of >3000 patients with inflammatory bowel disease at Lenox Hill Hospital, we identified 45 patients with Crohn's ileitis and ileosigmoid fistula (ISF): 24 had segmental sigmoid polyps and 18 had segmental inflammatory sigmoid strictures. The fistula was first seen by imaging in 36 patients, but not until resection by the surgeon or dissection by the pathologist in 7 patients.

RESULTS

The method of diagnosis for the initial recognition of the ISF and the sigmoid stricture is presented in Table 1. In 36 of the 45 cases, the ISF was recognized by radiologic imaging. In total, 31 of the 36 cases required surgical intervention, not because of the fistula, but because of small-bowel obstruction due to the ileitis. In 7 of the 31 (22%) cases, the fistula was recognized only by dissection of the inflammatory ileosigmoid mass by the surgeon or examination of the surgical specimen by the pathologist. The sequence of events from the originating ileitis to the ISF to the segmental sigmoid polyposis and stricture, with the resulting sigmoid obstruction, is shown in Figures 1A-E.

CONCLUSIONS

We emphasize the natural history of the ISF so that its recognition will lead to earlier medical management of the originating ileitis. Furthermore, it adds evidence of the recognition that the causative agent of Crohn's disease is carried by the fecal stream.

TLR signaling at the intestinal epithelial interface

The intestinal epithelium provides a critical interface between lumenal bacteria and the mucosal immune system. Whereas normal commensal flora do not trigger acute inflammation, pathogenic bacteria trigger a potent inflammatory response. Our studies emanate from the hypothesis that the intestinal epithelium is normally hyporesponsive to commensal pathogen-associated molecular patterns (PAMPs) such as LPS. Our data demonstrate that normal human colonic epithelial cells and lamina propria cells express low levels of TLR4 and its co-receptor MD-2. This expression pattern is mirrored by intestinal epithelial cell (IEC) lines. Co-expression of TLR4 and MD-2 is necessary and sufficient for LPS responsiveness in IEC. Moreover, LPS sensing occurs along the basolateral membrane of polarized IEC in culture. Expression of MD-2 is regulated by IFN-γ. Cloning of the MD-2 promoter demonstrates that promoter activity is increased by IFN-γ and blocked by the STAT inhibitor SOCS3. We conclude from our studies that the intestinal epithelium down-regulates expression of TLR4 and MD-2 and is LPS unresponsive. The Th1 cytokine IFN-γ up-regulates expression of MD-2 in a STAT-dependent fashion. The results of our studies have important implications for understanding human inflammatory bowel diseases.

Probiotics and prebiotics in ulcerative colitis

The intestinal microbiota is one of the key players in the etiology of ulcerative colitis. Manipulation of this microflora with probiotics and prebiotics is an attractive strategy in the management of ulcerative colitis. Several intervention studies for both the induction and maintenance of remission in ulcerative colitis patients have been performed. Most of these studies evaluated VSL#3 or E. Coli Nissle 1917 and in general there is evidence for efficacy of these agents for induction and maintenance of remission. However, studies are frequently underpowered, lack a control group, and are very heterogeneous investigating different probiotic strains in different study populations. The absence of well-powered robust randomized placebo-controlled trials impedes the widespread use of probiotics and prebiotics in ulcerative colitis. However, given the promising results that are currently available, probiotics and prebiotics may find their way to the treatment algorithm for ulcerative colitis in the near future.

Microbial Population Differentials between Mucosal and Submucosal Intestinal Tissues in Advanced Crohn's Disease of the Ileum

Since Crohn's disease is a transmural disease, we hypothesized that examination of deep submucosal tissues directly involved in the inflammatory disease process may provide unique insights into bacterial populations transgressing intestinal barriers and bacterial populations more representative of the causes and agents of the disease. We performed deep 16s microbiota sequencing on isolated ilea mucosal and submucosal tissues on 20 patients with Crohn's disease and 15 non-inflammatory bowel disease controls with a depth of coverage averaging 81,500 sequences in each of the 70 DNA samples yielding an overall resolution down to 0.0001% of the bacterial population. Of the 4,802,328 total sequences generated, 98.9% or 4,749,183 sequences aligned with the Kingdom Bacteria that clustered into 8545 unique sequences with <3% divergence or operational taxonomic units enabling the identification of 401 genera and 698 tentative bacterial species. There were significant differences in all taxonomic levels between the submucosal microbiota in Crohn's disease compared to controls, including organisms of the Order Desulfovibrionales that were present within the submucosal tissues of most Crohn's disease patients but absent in the control group. A variety of organisms of the Phylum Firmicutes were increased in the subjacent submucosa as compared to the parallel mucosal tissue including Ruminococcus spp., Oscillospira spp., Pseudobutyrivibrio spp., and Tumebacillus spp. In addition, Propionibacterium spp. and Cloacibacterium spp. were increased as well as large increases in Proteobacteria including Parasutterella spp. and Methylobacterium spp. This is the first study to examine the microbial populations within submucosal tissues of patients with Crohn's disease and to compare microbial communities found deep within the submucosal tissues with those present on mucosal surfaces. Our data demonstrate the existence of a distinct submucosal microbiome and ecosystem that is not well reflected in the mucosa and/or downstream fecal material.

The involvement of gut microbiota in inflammatory bowel disease pathogenesis: potential for therapy

Over the past recent years, a great number of studies have been directed toward the evaluation of the human host-gut microbiota interaction, with the goal to progress the understanding of the etiology of several complex diseases. Alterations in the intestinal microbiota associated with inflammatory bowel disease are well supported by literature data and have been widely accepted by the research community. The concomitant implementation of high-throughput sequencing techniques to analyze and characterize the composition of the intestinal microbiota has reinforced the view that inflammatory bowel disease results from altered interactions between gut microbes and the mucosal immune system and has raised the possibility that some form of modulation of the intestinal microbiota may constitute a potential therapeutic basis for the disease. The aim of this review is to describe the changes of gut microbiota in inflammatory bowel disease, focusing the attention on its involvement in the pathogenesis of the disease, and to review and discuss the therapeutic potential to modify the intestinal microbial population with antibiotics, probiotics, prebiotics, synbiotics and fecal microbiota transplantation.

Ciprofloxacin and probiotic Escherichia coli Nissle add-on treatment in active ulcerative colitis: a double-blind randomized placebo controlled clinical trial

BACKGROUND AND AIM

Ulcerative colitis (UC) is a chronic inflammatory bowel disease. The probiotic bacterium Escherichia coli Nissle 1917 (EcN) has been used to maintain and induce clinical remission in UC. Our aim was to test the effect of Ciprofloxacin and/or orally administered EcN as add-on to conventional therapies in patients with active UC.

PATIENTS AND METHODS

Our single center double-blinded randomized placebo controlled study included patients with a Colitis Activity Index (CAI) score of at least 6. Patients were randomized to Ciprofloxacin or placebo for 1week followed by EcN or placebo for 7weeks. All 4 treatments were given as add-on treatments.

RESULTS

One hundred subjects with active UC were recruited. In the per-protocol analysis we, surprisingly, found that in the group receiving placebo/EcN fewer patients, 54%, reached remission compared to the group receiving placebo/placebo, 89%, p<0.05. Among patients treated with Cipro/placebo and Cipro/EcN, 78% and 66% reached remission, respectively. Furthermore, the group receiving placebo/EcN had the largest number of withdrawals, 11 of 25 (44%), compared to 15 of 75 (20%) in any of the other groups, p<0.05. Indication of lack of mucosal healing was found in the group treated with placebo/Nissle, since only 4 (29%) of the 14 patients, who completed the study, reported no blood in stools at week 12 (p<0.02), compared to 63%, 67% and 65% in groups treated with Cipro/Nissle, Cipro/placebo and placebo/placebo, respectively.

CONCLUSIONS

Our data suggest that there is no benefit in the use of E. coli Nissle as an add-on treatment to conventional therapies for active ulcerative colitis. Furthermore, treatment with E. coli Nissle without a previous antibiotic cure resulted in fewer patients reaching clinical remission.

Increased frequency of intestinal CD4+ T cells reactive with mycobacteria in patients with Crohn's disease

OBJECTIVE

The aim of this study was to assess the frequency of mycobacteria and Escherichia coli reactive T cells in intestinal biopsies from patients with Crohn's disease (CD) and ulcerative colitis (UC).

MATERIALS AND METHODS

The biopsies were obtained by colonoscopy from adult patients with active CD (n = 5) and active UC (n = 4). The number of CD4+ T cell clones expanded and screened from each patient varied from 383 to 3972 giving a total of 16639 individual clones. The T cell clones were tested for responses to Mycobacterium avium subspecies paratuberculosis (MAP) and E. coli. The cytokine profile of 42 individual T cell clones from four CD patients was assessed.

RESULTS

The frequency of mycobacteria reactive T cell clones in CD patients ranged from 0.17 to 1.63% and was higher (p = 0.038) than the frequency of E. coli reactive T cells ranging from 0 to 0.18%. No or very low numbers of mycobacteria reactive clones were detected in three UC patients while the fourth UC patient had a frequency similar to what was observed in CD patients. The frequencies of E. coli reactive T cell clones in UC patients ranged from 0 to 0.52%. T cell clones (n = 42) from CD patients all produced IL-17 and/or IFN-γ. Several clones were also able to produce IL-10.

CONCLUSIONS

The high frequency of intestinal tissue resident T cells reactive to mycobacteria suggests that an adaptive immune response have taken place and argues that these bacteria may contribute to the chronic inflammation in CD.

Intestinal alkaline phosphatase inhibits the proinflammatory nucleotide uridine diphosphate

Uridine diphosphate (UDP) is a proinflammatory nucleotide implicated in inflammatory bowel disease. Intestinal alkaline phosphatase (IAP) is a gut mucosal defense factor capable of inhibiting intestinal inflammation. We used the malachite green assay to show that IAP dephosphorylates UDP. To study the anti-inflammatory effect of IAP, UDP or other proinflammatory ligands (LPS, flagellin, Pam3Cys, or TNF-α) in the presence or absence of IAP were applied to cell cultures, and IL-8 was measured. UDP caused dose-dependent increase in IL-8 release by immune cells and two gut epithelial cell lines, and IAP treatment abrogated IL-8 release. Costimulation with UDP and other inflammatory ligands resulted in a synergistic increase in IL-8 release, which was prevented by IAP treatment. In vivo, UDP in the presence or absence of IAP was instilled into a small intestinal loop model in wild-type and IAP-knockout mice. Luminal contents were applied to cell culture, and cytokine levels were measured in culture supernatant and intestinal tissue. UDP-treated luminal contents induced more inflammation on target cells, with a greater inflammatory response to contents from IAP-KO mice treated with UDP than from WT mice. Additionally, UDP treatment increased TNF-α levels in intestinal tissue of IAP-KO mice, and cotreatment with IAP reduced inflammation to control levels. Taken together, these studies show that IAP prevents inflammation caused by UDP alone and in combination with other ligands, and the anti-inflammatory effect of IAP against UDP persists in mouse small intestine. The benefits of IAP in intestinal disease may be partly due to inhibition of the proinflammatory activity of UDP.

Triggers and drivers of autoimmunity: lessons from coeliac disease

Coeliac disease, an inflammatory disease of the small intestine, shares key features with autoimmune disorders, such as susceptibility genes, presence of autoantibodies and T cell-mediated destruction of specific cells. Strikingly, however, continuous exposure to the exogenous dietary antigen gluten and gluten-specific adaptive immunity are required to maintain immunopathology. These observations challenge the notion that autoimmunity requires adaptive immune activation towards self antigens. Using coeliac disease as an example, we propose that other exogenous factors might be identified as drivers of autoimmune processes, in particular when evidence for T cells with specificity for self antigens driving the disease is lacking.

The colitis-associated transcriptional profile of commensal Bacteroides thetaiotaomicron enhances adaptive immune responses to a bacterial antigen

Background

Inflammatory bowel diseases (IBD) may be caused in part by aberrant immune responses to commensal intestinal microbes including the well-characterized anaerobic gut commensal Bacteroides thetaiotaomicron (B. theta). Healthy, germ-free HLA-B27 transgenic (Tg) rats develop chronic colitis when colonized with complex gut commensal bacteria whereas non-transgenic (nTg) rats remain disease-free. However, the role of B. theta in causing disease in Tg rats is unknown nor is much known about how gut microbes respond to host inflammation.

Methods

Tg and nTg rats were monoassociated with a human isolate of B. theta. Colonic inflammation was assessed by histologic scoring and tissue pro-inflammatory cytokine measurement. Whole genome transcriptional profiling of B. theta recovered from ceca was performed using custom GeneChips and data analyzed using dChip, Significance Analysis of Microarrays, and Gene Set Enrichment Analysis (GSEA) software. Western Blots were used to determine adaptive immune responses to a differentially expressed B. theta gene.

Results

B. theta monoassociated Tg rats, but not nTg or germ-free controls, developed chronic colitis. Transcriptional profiles of cecal B. theta were significantly different in Tg vs. nTg rats. GSEA revealed that genes in KEGG canonical pathways involved in bacterial growth and metabolism were downregulated in B. theta from Tg rats with colitis though luminal bacterial concentrations were unaffected. Bacterial genes in the Gene Ontology molecular function “receptor activity”, most of which encode nutrient binding proteins, were significantly upregulated in B. theta from Tg rats and include a SusC homolog that induces adaptive immune responses in Tg rats.

Conclusions

B. theta induces colitis in HLA-B27 Tg rats, which is associated with regulation of bacterial genes in metabolic and nutrient binding pathways that may affect host immune responses. These studies of the host-microbial dialogue may lead to the identification of novel microbial targets for IBD therapies.

Probiotics in the management of inflammatory bowel disease: a systematic review of intervention studies in adult patients

INTRODUCTION

Mounting evidence suggests an important role for the intestinal microbiota in the chronic mucosal inflammation that occurs in inflammatory bowel disease (IBD), and novel molecular approaches have further identified a dysbiosis in these patients. Several mechanisms of action of probiotic products that may interfere with possible aetiological factors in IBD have been postulated.

OBJECTIVE

Our objective was to discuss the rationale for probiotics in IBD and to systematically review clinical intervention studies with probiotics in the management of IBD in adults.

METHODS

A systematic search was performed in PubMed up to 1 October 2011, using defined keywords. Only full-text papers in the English language addressing clinical outcomes in adult patients were included. The 41 eligible studies were categorized on disease type (ulcerative colitis [UC] with/without an ileo-anal pouch and Crohn's disease [CD]) and disease activity. Pooled odds ratios were only calculated per probiotic for a specific patient group when more than one randomized controlled trial was available.

RESULTS

Well designed randomized controlled trials supporting the application of probiotics in the management of IBD are still limited. Meta-analyses could only be performed for a limited number of studies revealing overall risk ratios of 2.70 (95% CI 0.47, 15.33) for inducing remission in active UC with Bifido-fermented milk versus placebo or no additive treatment (n = 2); 1.88 (95% CI 0.96, 3.67) for inducing remission in active UC with VSL#3 versus placebo (n = 2); 1.08 (95% CI 0.86, 1.37) for preventing relapses in inactive UC with Escherichia coli Nissle 1917 versus standard treatment (n = 3); 0.17 (95% CI 0.09, 0.33) for preventing relapses in inactive UC/ileo-anal pouch anastomosis (IPAA) patients with VSL#3 versus placebo; 1.21 (95% CI 0.57, 2.57) for preventing endoscopic recurrences in inactive CD with Lactobacillus rhamnosus GG versus placebo (n = 2); and 0.93 (95% CI 0.63, 1.38) for preventing endoscopic recurrences in inactive CD with Lactobacillus johnsonii versus placebo (n = 2).

CONCLUSION

Further well designed studies based on intention-to-treat analyses by several independent research groups are still warranted to support the promising results for E. coli Nissle in inactive UC and the multispecies product VSL#3 in active UC and inactive pouch patients. So far, no evidence is available to support the use of probiotics in CD. Future studies should focus on specific disease subtypes and disease location. Further insight into the aetiology of IBD and the mechanisms of probiotic strains will aid in selecting probiotic strains for specific disease entities and disease locations.

Commensal Bacteroides species induce colitis in host-genotype-specific fashion in a mouse model of inflammatory bowel disease

The intestinal microbiota is important for induction of inflammatory bowel disease (IBD). IBD is associated with complex shifts in microbiota composition, but it is unclear whether specific bacterial subsets induce IBD and, if so, whether their proportions in the microbiota are altered during disease. Here, we fulfilled Koch's postulates in host-genotype-specific fashion using a mouse model of IBD with human-relevant disease-susceptibility mutations. From screening experiments we isolated common commensal Bacteroides species, introduced them into antibiotic-pretreated mice, and quantitatively reisolated them in culture. The bacteria colonized IBD-susceptible and -nonsusceptible mice equivalently, but induced disease exclusively in susceptible animals. Conversely, commensal Enterobacteriaceae were >100-fold enriched during spontaneous disease, but an Enterobacteriaceae isolate failed to induce disease in antibiotic-pretreated mice despite robust colonization. We thus demonstrate that IBD-associated microbiota alterations do not necessarily reflect underlying disease etiology. These findings establish important experimental criteria and a conceptual framework for understanding microbial contributions to IBD.

Commensal Bacteroides species induce colitis in host-genotype-specific fashion in a mouse model of inflammatory bowel disease

The intestinal microbiota is important for induction of inflammatory bowel disease (IBD). IBD is associated with complex shifts in microbiota composition, but it is unclear whether specific bacterial subsets induce IBD and, if so, whether their proportions in the microbiota are altered during disease. Here, we fulfilled Koch's postulates in host-genotype-specific fashion using a mouse model of IBD with human-relevant disease-susceptibility mutations. From screening experiments we isolated common commensal Bacteroides species, introduced them into antibiotic-pretreated mice, and quantitatively reisolated them in culture. The bacteria colonized IBD-susceptible and -nonsusceptible mice equivalently, but induced disease exclusively in susceptible animals. Conversely, commensal Enterobacteriaceae were >100-fold enriched during spontaneous disease, but an Enterobacteriaceae isolate failed to induce disease in antibiotic-pretreated mice despite robust colonization. We thus demonstrate that IBD-associated microbiota alterations do not necessarily reflect underlying disease etiology. These findings establish important experimental criteria and a conceptual framework for understanding microbial contributions to IBD.

Treatment of inflammatory bowel disease associated E. coli with ciprofloxacin and E. coli Nissle in the streptomycin-treated mouse intestine

Background

E. coli belonging to the phylogenetic group B2 are linked to Inflammatory Bowel Disease (IBD). Studies have shown that antimicrobials have some effect in the treatment of IBD, and it has been demonstrated that E. coli Nissle has prophylactic abilities comparable to 5-aminosalicylic acid (5-ASA) therapy in ulcerative colitis. The objective of this study was to test if ciprofloxacin and/or E. coli Nissle could eradicate IBD associated E. coli in the streptomycin-treated mouse intestine.

Results

After successful colonization with the IBD associated E. coli strains in mice the introduction of E. coli Nissle did not result in eradication of either IBD associated strains or an E. coli from a healthy control, instead, co-colonization at high levels were obtained. Treatment of mice, precolonized with IBD associated E. coli, with ciprofloxacin for three days alone apparently resulted in effective eradication of tested E. coli. However, treatment of precolonized mice with a combination of ciprofloxacin for 3 days followed by E. coli Nissle surprisingly allowed one IBD associated E. coli to re-colonize the mouse intestine, but at a level 3 logs under E. coli Nissle. A prolonged treatment with ciprofloxacin for 7 days did not change this outcome.

Conclusions

In the mouse model E. coli Nissle can not be used alone to eradicate IBD associated E. coli; rather, 3 days of ciprofloxacin are apparently efficient in eradicating these strains, but surprisingly, after ciprofloxacin treatment (3 or 7 days), the introduction of E. coli Nissle may support re-colonization with IBD associated E. coli.

Viruses, autophagy genes, and Crohn's disease

The etiology of the intestinal disease Crohn's disease involves genetic factors as well as ill-defined environmental agents. Several genetic variants linked to this disease are associated with autophagy, a process that is critical for proper responses to viral infections. While a role for viruses in this disease remains speculative, accumulating evidence indicate that this possibility requires serious consideration. In this review, we will examine the three-way relationship between viruses, autophagy genes, and Crohn's disease and discuss how host-pathogen interactions can mediate complex inflammatory disorders.

Etiology of perianal Crohn's disease: role of genetic, microbiological, and immunological factors

Perianal fistulation is a common complication of Crohn's disease (CD). Fistulating perianal CD appears to represent a distinct phenotype of CD, separate from luminal fistulating disease, with differing disease behavior and which often requires different therapeutic strategies. The etiology of Crohn's perianal fistulae appears to have genetic, microbiological, and immunological components. Relationships with IBD5, which codes for the organic/cation transporter and IRGM, important in the autophagy pathway, have been identified but further genetic associations remain elusive. The partially efficacious use of antibiotics and fecal diversion imply a microbiological component and, similarly, the partial efficacy of immunosuppressants and anti-tumor necrosis factor alpha (TNFalpha) treatments suggest not only that an immunological process is taking place, but also that microbiota alone cannot account for the pathogenesis. Recent work implicates failures in the tissue injury/repair process with myofibroblasts, matrix metalloproteinases, and an epithelial-to-mesenchymal transition being possible culprits. We examine these areas in a review of the current understanding of the etiology of Crohn's perianal fistulae.

A phylogenetic group of Escherichia coli associated with active left-sided inflammatory bowel disease

Background

Escherichia coli have been found in increased numbers in tissues from patients with Inflammatory Bowel Disease (IBD) and adherent-invasive E. coli have been found in resected ileum from patients with Crohn's disesae. This study aimed to characterize possible differences in phylogenetic group (triplex PCR), extraintestinal pathogenic E. coli (ExPEC) genes and multilocus sequence type (MLST) between E. coli strains isolated from IBD patients with past or present involvement of the left side of the colon and from controls.

Results

Fecal samples were collected from 18 patients and from 10 healthy controls. Disease activity was evaluated by sigmoidoscopy. Interestingly, E. coli strains of the phylogenetic group B2 were cultured from 60% of patients with IBD compared to 11% of healthy controls (p < 0.05). Furthermore, when comparing the number of E. coli B2 strains with at least one positive ExPEC gene among different groups, 86% were found positive among active IBD patients, significantly more than 13% among inactive IBD patients (p < 0.05), and 11% among healthy controls (p < 0.05). The B2 phylogenetic group was found in a specific cluster based on MLST, but no further separation between E. coli strains associated with active compared to inactive IBD was achieved.

Conclusion

In conclusion, E. coli of the phylogenetic group B2 were isolated more frequently from IBD patients with past or present involvement of the left side of the colon compared to healthy controls, and B2 strains with ExPEC genes were found more frequently among IBD patients with active disease compared to patients with inactive disease.

Negative interactions with the microbiota: IBD

Mucosal surfaces are colonized by a complex microbiota that provides beneficial functions under normal physiological conditions, but is capable of contributing to chronic inflammatory disease in susceptible individuals. Of the mucosal tissues, the mammalian intestine harbors an especially high number of microbes with a remarkable diversity. Inflammatory bowel disease (IBD) is a group of chronic relapsinginflammatory disorders of the intestinal mucosa. Evidence from human studies and animal models provides compelling support that intestinal microbes play a key role in disease pathogenesis. While the existence a specific causative pathogen is possible, it appears more likely that intestinal microbes normally present as commensal microbiota may trigger inflammation and perpetuate disease in genetically susceptible individuals. There may be also a shift in the makeup of the commensal flora to a nonphysiologic composition that is more prone to disease (termed dysbiosis). Evidence supports that genetic susceptibility stems from one or more defects in mucosal immune functions, including microbe recognition, barrier function, intercellular communication and antimicrobial effector mechanisms. It is quite plausible to imagine that the chronic inflammation of IBD may in some cases be a normal immune response to an abnormal adherent invasive microbiota and in other cases an over exuberant immune response to an otherwise normal commensal microbiota.

Managing medical complications and recurrence after surgery for Crohn's disease

Each of the medical and surgical therapies for Crohn's disease has inherent advantages and disadvantages that must be balanced for patients with moderate to severe disease. Most patients with Crohn's disease require surgery at some point during the lifelong illness, but surgical therapy is not curative for most patients, as postoperative recurrence of Crohn's disease is common and can pose diagnostic and therapeutic challenges. Disease monitoring and appropriate prophylaxis are necessary in patients at high risk.

NOD2/CARD15 gene variants are linked to failure of antibiotic treatment in perianal fistulating Crohn's disease

OBJECTIVES

The Crohn's disease (CD) susceptibility gene, nucleotide-binding oligomerizetion domain 2 (NOD2)/caspase recruitment domain 15 (CARD15), is linked to the innate immune response associated with altered epithelial bacterial defense. Its relevance in antibiotic therapy of perianal fistulating CD remains elusive. The aim of the study was to explore systematically the association between NOD2/CARD15 variants and clinical response of perianal fistulas in patients using antibiotic therapy.

METHODS

Fifty-two patients (median age 36 yr) with draining perianal fistulas were treated with ciprofloxacin (N = 49) or metronidazole (N = 3) for a median duration of 7 wk. Complete response was defined as the absence of any draining fistula despite gentle finger compression. Genotyping for NOD2/CARD15 variants and human beta (beta)-defensin 2 (HBD-2) copies was performed by 5' nuclease assays (Applied Biosystems, Foster City, CA). The examiners and laboratory investigators were blinded. The Fisher exact test and Wilcoxon signed rank test were used for statistical analysis.

RESULTS

Ciprofloxacin was discontinued in one patient due to diarrhea after 2 wk. Complete fistula response was observed in 13 of 39 patients with NOD2/CARD15 wild-type (33.3%) compared with none in patients carrying NOD2/CARD15 variants (0%, P= 0.02). The median number of HBD-2 gene copies between responders and partial/nonresponders was similar.

CONCLUSIONS

The study result suggests a substantial contribution of NOD2/CARD15 to the antibiotic treatment outcome of perianal fistulating CD. NOD2/CARD15 variants may predispose to an altered intestinal microflora in perianal fistulas that is less responsive to antibiotic treatment.

Review article: Probiotics in gastrointestinal and liver diseases

BACKGROUND

Probiotics, defined as live micro-organisms with beneficial effects for the host, are widely applied in gastrointestinal and liver diseases.

AIM AND METHOD

To review the available evidence of clinical trials on probiotics in gastrointestinal and liver diseases, with a major focus on irritable bowel syndrome, inflammatory bowel disease, pancreatitis and chronic liver diseases.

RESULTS

Evidence for the therapeutic or preventive application of particular probiotic strains is available for antibiotic-associated diarrhoea, rota-virus-associated diarrhoea and pouchitis. Results are encouraging for irritable bowel syndrome, ulcerative colitis and for reducing side effects by Helicobacter pylori eradication therapies, but are less clear for Crohn's disease, lactose intolerance and constipation. In general, for most of these patient groups, more placebo-controlled methodologically well-designed studies that pay attention to both clinical outcome and mechanistic aspects are required. The application in liver disease and pancreatitis is promising, but more human trials have to be awaited. Possible mechanisms of probiotics include modulation of the intestinal microbiota and the immune system, but different bacterial may have different effects.

CONCLUSION

Further insight into disease entities and the functioning of probiotic strains is required to be able to select disease-specific strains, which have to be tested in well-designed placebo-controlled studies.

Lactobacilli, bifidobacteria and E. coli nissle induce pro- and anti-inflammatory cytokines in peripheral blood mononuclear cells

AIM: To investigate whether the stimulation of peripheral blood mononuclear cells (PBMNC) with the cell debris and cell extraction of different probiotic strains is similar or species specific.

METHODS: Three strains of bifidobacteria, 4 strains of lactobacilli, and E. coli nissle were sonicated and centrifuged in order to divide them into cell extract and cell debris. PBMNC were separated by density gradient and incubated for 36 h with either the cell debris or the cell extract of single strains of probiotic bacteria in doses from 10² to 10⁸ CFU/mL. Cell supernatants were taken and interleukin (IL)-10, IL-1β, and tumor necosis factor (TNF)-α were determined by ELISA.

RESULTS: Depending on the species super-family, the strains had different stimulation patterns. Except for both L. casei strains, the cell extract of bifidobacteria and lactobacilli had less stimulating capacity than cell debris, whereas the cell extract of E. coli nissle had similar stimulating properties to that of the cell debris of the strain and significantly more stimulating capacity than that of bifidobacteria and lactobacilli. The cell debris of bifidobacteria stimulated more cytokine release than the cell debris of lactobacilli. The cell debris of lactobacilli did not have a stimulating capacity when lower concentrations were used. Neither cell extraction nor cell debris had an inhibitory effect on the production of the tested cytokines by stimulated PBMNC.

CONCLUSION: The incubation of probiotic strains, which have been used in clinical trials for inflammatory diseases, with immunocompetent cells leads to different species specific reactions. High IL-10 response to cell debris of bifidobacteria and E. coli nissle can be found. This corresponds to positive effects of bifidobacteria and E. coli nissle in clinical trials for inflammatory bowel disease compared to negative outcomes obtained with lactobacilli.

Do probiotics have a therapeutic role in gastroenterology?

Several hundred species of bacteria inhabit the gut, and affect its cell biology, morphology and homeostasis. Many bacteria are however potential pathogens, especially if the integrity of the epithelial barrier is physically or functionally breached. Conversely, the interaction between host and commensal microbes can confer important health benefits. This has led to commercial and public interest in 'probiotics', live microbes principally taken as food supplements. Might probiotics also be used in disease therapy Experimental evidence that probiotics modulate gut physiology, particularly barrier integrity and immunological function, underpins exciting new gastroenterological research. We discuss below the scientific basis for probiotic effects and present a critical perspective for their use in relation to gastrointestinal disease.

Toll-like receptor-4 is required for intestinal response to epithelial injury and limiting bacterial translocation in a murine model of acute colitis

Inflammatory bowel disease (IBD) arises from a dysregulated mucosal immune response to luminal bacteria. Toll-like receptor (TLR)4 recognizes LPS and transduces a proinflammatory signal through the adapter molecule myeloid differentiation marker 88 (MyD88). We hypothesized that TLR4 participates in the innate immune response to luminal bacteria and the development of colitis. TLR4-/- and MyD88-/- mice and littermate controls were given 2.5% dextran sodium sulfate (DSS) for 5 or 7 days followed by a 7-day recovery. Colitis was assessed by weight loss, rectal bleeding, and histopathology. Immunostaining was performed for macrophage markers, chemokine expression, and cell proliferation markers. DSS treatment of TLR4-/- mice was associated with striking reduction in acute inflammatory cells compared with wild-type mice despite similar degrees of epithelial injury. TLR4-/- mice experienced earlier and more severe bleeding than control mice. Similar results were seen with MyD88-/- mice, suggesting that this is the dominant downstream pathway. Mesenteric lymph nodes from TLR4-/- and MyD88-/- mice more frequently grew gram-negative bacteria. Altered neutrophil recruitment was due to diminished macrophage inflammatory protein-2 expression by lamina propria macrophages in TLR4-/- and MyD88-/- mice. The similarity in crypt epithelial damage between TLR4-/- or MyD88-/- and wild-type mice was seen despite decreased epithelial proliferation in knockout mice. TLR4 through the adapter molecule MyD88 is important in intestinal response to injury and in limiting bacterial translocation. Despite the diversity of luminal bacteria, other TLRs do not substitute for the role of TLR4 in this acute colitis model. A defective innate immune response may result in diminished bacterial clearance and ultimately dysregulated response to normal flora.

Human intestinal epithelial cells are broadly unresponsive to Toll-like receptor 2-dependent bacterial ligands: implications for host-microbial interactions in the gut

Intestinal epithelial cells (IEC) interact with a high density of Gram-positive bacteria and are active participants in mucosal immune responses. Recognition of Gram-positive organisms by Toll-like receptor (TLR)2 induces proinflammatory gene expression by diverse cells. We hypothesized that IEC are unresponsive to Gram-positive pathogen-associated molecular patterns and sought to characterize the functional responses of IEC to TLR2-specific ligands. Human colonic epithelial cells isolated by laser capture microscopy and IEC lines (Caco-2, T84, HT-29) were analyzed for expression of TLR2, TLR6, TLR1, and Toll inhibitory protein (Tollip) mRNA by RT-PCR and quantitative real-time PCR. Response to Gram-positive bacterial ligands was measured by NF-kappa B reporter gene activation and IL-8 secretion. TLR2 protein expression was analyzed by immunofluorescence and flow cytometry. Colonic epithelial cells and lamina propria cells from both uninflamed and inflamed tissue demonstrate low expression of TLR2 mRNA compared with THP-1 monocytes. IECs were unresponsive to TLR2 ligands including the staphylococcal-derived Ags phenol soluble modulin, peptidoglycan, and lipotechoic acid and the mycobacterial-derived Ag soluble tuberculosis factor. Transgenic expression of TLR2 and TLR6 restored responsiveness to phenol soluble modulin and peptidoglycan in IEC. In addition to low levels of TLR2 protein expression, IEC also express high levels of the inhibitory molecule Tollip. We conclude that IEC are broadly unresponsive to TLR2 ligands secondary to deficient expression of TLR2 and TLR6. The relative absence of TLR2 protein expression by IEC and high level of Tollip expression may be important in preventing chronic proinflammatory cytokine secretion in response to commensal Gram-positive bacteria in the gut.

Pseudomonas fluorescens encodes the Crohn's disease-associated I2 sequence and T-cell superantigen

Commensal bacteria have emerged as an important disease factor in human Crohn's disease (CD) and murine inflammatory bowel disease (IBD) models. We recently isolated I2, a novel gene segment of microbial origin that is associated with human CD and that encodes a T-cell superantigen. To identify the I2 microorganism, BLAST analysis was used to identify a microbial homologue, PA2885, a novel open reading frame (ORF) in the Pseudomonas aeruginosa genome. PCR and Southern analysis identified Pseudomonas fluorescens as the originating species of I2, with homologues detectable in 3 of 13 other Pseudomonas species. Genomic cloning disclosed a locus containing the full-length I2 gene (pfiT) and three other orthologous genes, including a homologue of the pbrA/pvdS iron response gene. CD4(+) T-cell responses to recombinant proteins were potent for I2 and pfiT, but modest for PA2885. pfiT has several features of a virulence factor: association with an iron-response locus, restricted species distribution, and T-cell superantigen bioactivity. These findings suggest roles for pfiT and P. fluorescens in the pathogenesis of Crohn's disease.

Intestinal microflora as a therapeutic target in inflammatory bowel disease

Although the causes of inflammatory bowel disease (IBD) remain incompletely understood, increasing evidence implicates intestinal microflora in the pathogenesis of these disorders. Alteration of intestinal flora therefore may offer a plausible therapeutic approach. Although recent data support a potential therapeutic role for probiotics and prebiotics in patients with IBD, such treatments need to be further assessed by large, double-blind controlled trials. A better understanding of the intestinal microflora and the mechanisms of their action may help us to develop more effective treatment for IBD.

The role of the gut flora in health and disease, and its modification as therapy

The gut flora is a vast interior ecosystem whose nature is only beginning to be unravelled, due to the emergence of sophisticated molecular tools. Techniques such as 16S ribosomal RNA analysis, polymerase chain reaction amplification and the use of DNA microarrays now facilitate rapid identification and characterization of species resistant to conventional culture and possibly unknown species. Life-long cross-talk between the host and the gut flora determines whether health is maintained or disease intervenes. An understanding of these bacteria-bacteria and bacteria-host immune and epithelial cell interactions is likely to lead to a greater insight into disease pathogenesis. Studies of single organism-epithelial interactions have revealed the large range of metabolic processes that gut bacteria may influence. In inflammatory bowel diseases, bacteria drive the inflammatory process, and genetic predisposition to disease identified to date, such as the recently described NOD2/CARD15 gene variants, may relate to altered bacterial recognition. Extra-intestinal disorders, such as atopy and arthritis, may also have an altered gut milieu as their basis. Clinical evidence is emerging that the modification of this internal environment, using either antibiotics or probiotic bacteria, is beneficial in preventing and treating disease. This natural and apparently safe approach holds great appeal.

Medical management of postoperative complications of inflammatory bowel disease: pouchitis and Crohn's disease recurrence

Surgical intervention is often required for patients with inflammatory bowel disease. Total proctocolectomy with ileal pouch-anal anastomosis is the surgical treatment of choice for patients with ulcerative colitis. The main long-term complication of this surgery is pouchitis, with 10-year cumulative incidence rates between 24% and 46%. For patients with Crohn's disease, postoperative recurrence is a significant problem, with clinical recurrence rates as high as 55% at 5 years and 76% at 15 years. Increasing evidence suggests that postoperative medical therapy has the potential to decrease the risk of postoperative Crohn's disease recurrence.

The Crohn's disease-associated bacterial protein I2 is a novel enteric t cell superantigen

An aberrant T cell response to enteric bacteria is important in inflammatory bowel disease. However, the identity of relevant microbial antigens is unknown. Here, we report the presence of I2, a Crohn's disease-associated microbial gene, in the murine intestine. The I2 protein induced a proliferative and IL-10 response by CD4(+) T cells from unimmunized mice. The I2 response was dependent on MHC class II-mediated recognition but did not require antigen processing. Selective activation was observed for the TCR-Vbeta5 subpopulation. These findings indicate that the I2 protein is a new class of T cell superantigen and suggest that colonization by the I2 microorganism in susceptible hosts may provide a superantigenic stimulus pertinent to Crohn's disease pathogenesis.