High-level serum antibodies to bacterial antigens are associated with antibiotic-induced clinical remission in Crohn's disease: a pilot study

Adherent-invasive E. coli - induced specific IgA limits pathobiont localization to the epithelial niche in the gut

BACKGROUND AND AIM

Adherent-invasive E. coli (AIEC) has been identified as a pathobiont associated with Crohn's disease (CD), that prefers to grow in inflammatory conditions. Although the colonization by AIEC is implicated in the progression of the disease and exacerbates inflammation in murine colitis models, the recognition and response of host immunity to AIEC remains elusive.

METHODS

Antibiotic treated female C57BL/6 mice were inoculated by commensal E. coli and LF82 AIEC strains. Luminal-IgA fractions were prepared from feces and their binding to AIEC and other strains was assessed to confirm specificity. IgA binding to isogenic mutant strains was performed to identify the functional molecules that are recognized by AIEC specific IgA. The effect of IgA on epithelial invasion of LF82 strain was confirmed using in vitro invasion assay and in vivo colonization of the colonic epithelium.

RESULTS

Persistent colonization by AIEC LF82 induced secretion of luminal IgA, while commensal E. coli strain did not. Induced anti-LF82 IgA showed specific binding to other AIEC strains but not to the commensal, non-AIEC E. coli strains. Induced IgA showed decreased binding to LF82 strains with mutated adhesin and outer membrane proteins which are involved in AIEC - epithelial cell interaction. Consistently, LF82-specific IgA limited the adhesion and invasion of LF82 in cultured epithelial cells, which seems to be required for the elimination in the colonic epithelium in mice.

CONCLUSION

These results demonstrate that host immunity selectively recognizes pathobiont E. coli, such as AIEC, and develop specific IgA. The induced IgA specific to pathobiont E. coli, in turn, contributes to preventing the pathobionts from accessing the epithelium.

Phylogrouping and characterization of Escherichia coli isolated from colonic biopsies and fecal samples of patients with flare of inflammatory bowel disease in Iran

BACKGROUND

Although the etiopathogenesis of inflammatory bowel disease (IBD) is still poorly understood, Escherichia coli has been described as a potential causative microorganism in IBD pathogenesis and also disease progression, offering a potential therapeutic target for disease management. Therefore, we conducted this study to investigate the pathotypes, phylogenetic groups, and antimicrobial resistance of E. coli isolates from patients with IBD in Iran.

METHODS

Fecal and biopsy colonic samples were collected from IBD patients experiencing flare-up episodes referred to Taleghani hospital in Tehran, Iran, between August 2020 and January 2021. Identification of E. coli strains was performed based on biochemical and molecular methods. Antibiotic susceptibility testing was performed as recommended by the Clinical and Laboratory Standards Institute. Phylogrouping and pathotyping of each isolate were carried out using polymerase chain reaction (PCR) and multilocus sequence typing (MLST) assays.

RESULTS

A total of 132 non-duplicate E. coli strains were isolated from 113 IBD patients, including 96 ulcerative colitis (UC), and 17 Crohn's disease (CD) patients. In our study, 55% of CD-related E. coli and 70.5% of UC-related isolates were non-susceptible to at least three or more unique antimicrobial classes, and were considered as multidrug-resistant (MDR) strains. E. coli strains exhibited a high level of resistance to cefazolin, ampicillin, tetracycline, ceftazidime, ciprofloxacin, and cefotaxime. Enterotoxigenic E. coli (ETEC) and diffusely adherent E. coli (DAEC) were the most prevalent pathotypes, and groups B2 and D were the predominant phylogroups.

CONCLUSION

In the present study, we found that E. coli strains that colonize the gut of Iranian patients with IBD most frequently belonged to phylogenetic groups B2 and D. We also conclude that E. coli isolates from IBD patients have been revealed to be resistant to commonly used antibiotics, in which most of them harbored strains that would be categorized as MDR.

The Role of Immunomodulators and Biologics in the Medical Management of Stricturing Crohn's Disease

Crohn's disease is a progressive and disabling inflammatory disease involving the gastrointestinal tract. It usually produces inflammatory lesions in the ileocolonic region, but up to half of patients will also develop complications such as strictures in the long term. Indeed, a proportion of patients have progression of the disease with the development of stricturing lesions because there are no drugs that effectively prevent or reverse established fibrosis, and hence these patients are usually treated with surgery or endoscopic balloon dilation. Fibrotic lesions are always associated with some degree of inflammatory changes, but there is little evidence supporting the use of medical therapy in this context. Here, we discuss the most important findings on the possible use of immunomodulators or biologics in the prevention and treatment of intestinal strictures in Crohn's disease patients. Recent evidence demonstrates that these drugs may also be effective in treating lesions with high levels of collagen deposition, and thus might, at least in some patients, reduce the progression of the disease and bowel damage, and further avoid the need for surgery and a disabling course in the long term.

Azithromycin and metronidazole versus metronidazole-based therapy for the induction of remission in mild to moderate paediatric Crohn's disease : a randomised controlled trial

OBJECTIVE

Crohn's disease (CD) pathogenesis associated with dysbiosis and presence of pathobionts in the lumen, intracellular compartments and epithelial biofilms. Azithromycin is active in all three compartments. Our goal was to evaluate if azithromycin-based therapy can improve response and induce remission compared with metronidazole alone in paediatric CD.

DESIGN

This blinded randomised controlled trial allocated children 5-18 years with 10<Pediatric Crohn's Disease Activity Index (PCDAI)≤40 to azithromycin 7.5 mg/kg, 5 days/week for 4 weeks and 3 days/week for another 4 weeks with metronidazole 20 mg/kg/day (group 1) or metronidazole alone (group 2), daily for 8 weeks. Failures from group 2 were offered azithromycin as open label. The primary end point was response defined by a decrease in PCDAI>12.5 or remission using intention to treat analysis.

RESULTS

73 patients (mean age 13.8±3.1 years) were enrolled, 35 to group 1 and 38 to group 2. Response and remission rates at week 8 were identical 23/35 (66%) in group 1 and 17/38 (45%) and 15/38 (39%) in group 2 (P=0.07 and P=0.025, respectively). The needed to treat for remission was 3.7. Faecal calprotectin declined significantly in group 1 (P=0.003) but not in group 2 (p=0.33), and was lower at week 8 (P=0.052). Additional therapy was required in 6/35(17%) from group 1 versus 16/38(42%) in group 2 (P=0.027) by week 8. Among 12 failures in group 2, open-label azithromycin led to remission in 10/12 (83%).

CONCLUSIONS

The combination of azithromycin and metronidazole failed to improve response but was superior for induction of remission and reduction in calprotectin.

TRIAL REGISTRATION NUMBER

NCT01596894.

Serum anti-glycan-antibodies in relatives of patients with inflammatory bowel disease

BACKGROUND

Serum anti-glycan antibodies are a promising tool for differential diagnosis, disease stratification and prediction of Crohn's disease (CD). To investigate possible heritability of the markers we assessed the presence of serum anti-glycan antibodies in affected and unaffected relatives of patients with CD.

METHODS

Serum samples of 169 IBD patients of the German inflammatory bowel disease (IBD) network (140 CD & 29 Ulcerative colitis (UC)), 349 relatives of CD patients, 63 relatives of UC patients and 46 healthy controls were tested for the presence of anti-glycan antibodies by ELISA in a blinded fashion. Clinical data of the IBD patients and controls were available.

RESULTS

A higher proportion of non-affected CD relatives was positive for anti-glycan antibodies compared to healthy subjects. No inheritance of a specific pattern of anti-glycan antibodies could be detected. No difference in marker expression depending on the degree of relationship in the non-affected relatives was noted and the presence of family history did not lead to a difference in marker levels in the affected CD subjects.

CONCLUSIONS

Non-affected CD relatives had a higher frequency of anti-glycan antibodies compared to healthy subjects. This difference was mild and was found to be true for the overall reactivity to glycan antigens, but not for specific patterns. This may indicate an inherited mechanism resulting in a non-specific increased reactivity to microbial antigens in IBD.

IBD Serology and Disease Outcomes in African Americans With Crohn's Disease

BACKGROUNDS

Recent studies have identified the role of serologic markers in characterizing disease phenotype, location, complications, and severity among Northern Europeans (NE) with Crohn's disease (CD). However, very little is known about the role of serology in CD among African Americans (AA). Our study explored the relationship between serology and disease phenotype in AA with CD, while controlling for genetic ancestry.

METHODS

AAs with CD were enrolled as participants through multicenter collaborative efforts. Serological levels of IgA anti-Saccharomyces cervisiae antibody (ASCA), IgG ASCA, E. coli outermembrane porin C, anti-CBir1, and ANCA were measured using enzyme-linked immunosorbent assays. Genotyping was performed using Illumina immunochip technology; an admixture rate was calculated for each subject. Multiple imputation by chained equations was performed to account for data missing at random. Logistic regression was used to calculate adjusted odds ratio (OR) for associations between serological markers and both complicated disease and disease requiring surgery.

RESULTS

A total of 358 patients were included in the analysis. The majority of our patients had inflammatory, noncomplicated disease (58.4%), perianal disease (55.7%), and documented colonic inflammation (86.8%). On multivariable analysis, both IgG ASCA and OmpC were associated with complicated disease (OR, 2.67; 95% CI, 1.67-4.28; OR, 2.23; 95% CI, 1.41-3.53, respectively) and disease requiring surgery (OR, 2.51; 95% CI, 1.49-4.22; OR, 3.57; 95% CI, 2.12-6.00). NE admixture to the African genome did not have any associations or interactions in relation to clinical outcome.

CONCLUSIONS

Our study comprises the largest cohort of AAs with CD. The utility of serological markers for the prognosis of CD in NE applies equally to AA populations.

Mechanisms, Management, and Treatment of Fibrosis in Patients With Inflammatory Bowel Diseases

In the last 10 years, we have learned much about the pathogenesis, diagnosis, and management of intestinal fibrosis in patients with inflammatory bowel diseases. Just a decade ago, intestinal strictures were considered to be an inevitable consequence of long-term inflammation in patients who did not respond to anti-inflammatory therapies. Inflammatory bowel diseases-associated fibrosis was seen as an irreversible process that frequently led to intestinal obstructions requiring surgical intervention. This paradigm has changed rapidly, due to the antifibrotic approaches that may become available. We review the mechanisms and diagnosis of this serious complication of inflammatory bowel diseases, as well as factors that predict its progression and management strategies.

European Crohn's and Colitis Organisation Topical Review on Prediction, Diagnosis and Management of Fibrostenosing Crohn's Disease

This ECCO topical review of the European Crohn's and Colitis Organisation [ECCO] focused on prediction, diagnosis, and management of fibrostenosing Crohn's disease [CD]. The objective was to achieve evidence-supported, expert consensus that provides guidance for clinical practice.

Microbiology, genomics, and clinical significance of the Pseudomonas fluorescens species complex, an unappreciated colonizer of humans

Pseudomonas fluorescens is not generally considered a bacterial pathogen in humans; however, multiple culture-based and culture-independent studies have identified it at low levels in the indigenous microbiota of various body sites. With recent advances in comparative genomics, many isolates originally identified as the "species" P. fluorescens are now being reclassified as novel Pseudomonas species within the P. fluorescens "species complex." Although most widely studied for its role in the soil and the rhizosphere, P. fluorescens possesses a number of functional traits that provide it with the capability to grow and thrive in mammalian hosts. While significantly less virulent than P. aeruginosa, P. fluorescens can cause bacteremia in humans, with most reported cases being attributable either to transfusion of contaminated blood products or to use of contaminated equipment associated with intravenous infusions. Although not suspected of being an etiologic agent of pulmonary disease, there are a number of reports identifying it in respiratory samples. There is also an intriguing association between P. fluorescens and human disease, in that approximately 50% of Crohn's disease patients develop serum antibodies to P. fluorescens. Altogether, these reports are beginning to highlight a far more common, intriguing, and potentially complex association between humans and P. fluorescens during health and disease.

Multidrug resistance is common in Escherichia coli associated with ileal Crohn's disease

BACKGROUND

Escherichia coli is increasingly implicated in the pathogenesis of ileal Crohn's disease (ICD), offering a potential therapeutic target for disease management. Empirical antimicrobial targeting of ileal E. coli has advantages of economy and speed of implementation, but relies on uniform susceptibility of E. coli to routinely selected antimicrobials to avoid apparent treatment failure. Therefore, we examined the susceptibility of ileal E. coli to such antimicrobials.

METHODS

E. coli from 32 patients with ICD and 28 with normal ileum (NI) were characterized by phylogroup, pathotype, antimicrobial susceptibility, and presence of antimicrobial resistance genes.

RESULTS

In all, 17/32 ICD and 12/28 NI patients harbored ≥ 1 E. coli strain; 10/24 E. coli strains from ICD and 2/14 from NI were nonsuscepti-ble to ≥ 1 antimicrobial in ≥ 3 categories (multidrug-resistant). Resistance to amoxicillin/clavulanic-acid, cefoxitin, chloramphenicol, ciprofloxa-cin, gentamicin, and rifaximin was restricted to ICD, with 10/24 strains from 8/17 patients resistant to ciprofloxacin or rifaximin (P < 0.01). Adherent-invasive E. coli (AIEC) were isolated from 8/32 ICD and 5/28 NI, and accounted for 54% and 43% of E. coli strains in these groups. In all, 8/13 AIEC strains from ICD (6/8 patients) versus 2/6 NI (2/5 patients) showed resistance to the macrophage-penetrating antimicrobials ciprofloxacin, clarithromycin, rifampicin, tetracycline, and trimethoprim/sulfamethoxazole. Resistance was associated with tetA, tetB, tetC, bla-(TEM), bla(oxa)-1, sulI, sulII, dhfrI, dhfrVII, ant(3″)-Ia, and catI genes and prior use of rifaximin (P < 0.01).

CONCLUSIONS

ICD-associated E. coli frequently manifest resistance to commonly used antimicrobials. Clinical trials of antimicrobials against E. coli in ICD that are informed by susceptibility testing, rather than empirical selection, are more likely to demonstrate valid outcomes of such therapy.

Serological antibodies in inflammatory bowel disease: a systematic review

The diagnosis of inflammatory bowel disease (IBD) is traditionally based on a combination of clinical, endoscopic, histological, and radiological criteria. However, further testing is needed in cases of diagnostic uncertainty and in predicting disease course. This systematic review focuses on the potential for 10 serological antibodies to fill these roles: pANCA, ASCA, anti-OmpC, anti-CBir1, anti-I2, ALCA, ACCA, AMCA, anti-L, and anti-C. We discuss their prevalence in IBD and health; their role in disease diagnosis and risk stratification; their stability over time; their presence in unaffected relatives; their association with genetic variants; and differences across ethnic groups. Serological antibodies have some role in primary diagnosis and in differentiating between Crohn's disease and ulcerative colitis. In indeterminate colitis, preoperative measurement of serological antibodies can help to predict the likelihood of complications among patients undergoing pouch surgery. The combined presence and magnitude of a large panel of antibodies appear to be of value in predicting disease progression. There is currently insufficient evidence to recommend the use of antibody testing to predict responses to treatment or surgery in patients with IBD.

The promise and pitfalls of serologic testing in inflammatory bowel disease

The role of IBD serologies is still evolving. However, as that evolution progresses, it will continue to provide important insights into the etiology of IBD and help define individualized treatment strategies for patients. The presence of multiple IBD antimicrobial antibodies and increased reactivity form a useful heuristic model to understand the evolution of CD. The role of ANCAs and autoantibodies in pathogenesis of UC is an area that requires further investigation. Although IBD serologies exhibit considerable diagnostic accuracy, it is unclear whether they will supplant simpler and more direct evaluations in making an initial diagnosis of UC or Crohn (Table 3). The utility of panels of IBD serologies to stratify and predict the course of CD has been an arena of fertile investigation. Developing individual treatment strategies based on the probability of developing complicated aggressive disease would be a significant advance in medical management of CD. However, if major clinical decisions are to be made based on these serologies, we will need more prospective critical studies from the time of diagnosis to define their clinical applicability and to demonstrate a true difference in outcomes.

IBD-what role do Proteobacteria play?

The gastrointestinal microbiota has come to the fore in the search for the causes of IBD. This shift has largely been driven by the finding of genetic polymorphisms involved in gastrointestinal innate immunity (particularly polymorphisms in NOD2 and genes involved in autophagy) and alterations in the composition of the microbiota that might result in inflammation (so-called dysbiosis). Microbial diversity studies have continually demonstrated an expansion of the Proteobacteria phylum in patients with IBD. Individual Proteobacteria, in particular (adherent-invasive) Escherichia coli, Campylobacter concisus and enterohepatic Helicobacter, have all been associated with the pathogenesis of IBD. In this Review, we comprehensively describe the various associations of Proteobacteria and IBD. We also examine the importance of pattern recognition in the extracellular innate immune response of the host with particular reference to Proteobacteria, and postulate that Proteobacteria with adherent and invasive properties might exploit host defenses, drive proinflammatory change, alter the intestinal microbiota in favor of dysbiosis and ultimately lead to the development of IBD.

IBD-what role do Proteobacteria play?

The gastrointestinal microbiota has come to the fore in the search for the causes of IBD. This shift has largely been driven by the finding of genetic polymorphisms involved in gastrointestinal innate immunity (particularly polymorphisms in NOD2 and genes involved in autophagy) and alterations in the composition of the microbiota that might result in inflammation (so-called dysbiosis). Microbial diversity studies have continually demonstrated an expansion of the Proteobacteria phylum in patients with IBD. Individual Proteobacteria, in particular (adherent-invasive) Escherichia coli, Campylobacter concisus and enterohepatic Helicobacter, have all been associated with the pathogenesis of IBD. In this Review, we comprehensively describe the various associations of Proteobacteria and IBD. We also examine the importance of pattern recognition in the extracellular innate immune response of the host with particular reference to Proteobacteria, and postulate that Proteobacteria with adherent and invasive properties might exploit host defenses, drive proinflammatory change, alter the intestinal microbiota in favor of dysbiosis and ultimately lead to the development of IBD.

Seroreactivity to E. coli outer membrane protein C antibodies in active inflammatory bowel disease; diagnostic value and correlation with phylogroup B2 E. coli infection

BACKGROUND

Several serologic tests, including anti-outer membrane porin C antibody (Omp C), are used for screening and as marker of disease course in inflammatory bowel diseases (IBD). Our aim was to investigate possible differences in Omp C level in patients with active and inactive IBD compared to controls.

METHODS

All blood samples were tested for Omp C. Disease activity was evaluated by Harvey Bradshaw Index, Simple Clinical Activity Index and Modified Pouchitis Disease Activity Index.

RESULTS

Blood samples were collected from 113 patients and 60 controls. Patients with active IBD did not have a higher level of Omp C than patients in remission. Surprisingly, in patients with active Crohn's disease a significantly lower level of Omp C was found compared with patients with inactive Crohn's disease (p < 0.05). All other groups among patients with IBD did have a significantly higher level of Omp C, compared with controls, including patients with acute gastroenteritis (p < 0.05). Although IBD patients with phylogroup B2 E. coli cultured from their fecal samples, were more likely to have a positive Omp C test (p < 0.05), this could not explain the low Omp C level in the subgroup of patients with active Crohn's disease.

CONCLUSIONS

Omp C titer was not raised in patients with active IBD compared with patients in remission. In addition, there was no difference in Omp C level in patients with active Crohn's disease compared with controls. These observations do not support the use of Omp C serology testing, either in disease activity assessment, or in screening for active Crohn's disease.

Current and future role of biomarkers in Crohn's disease risk assessment and treatment

BACKGROUND

Crohn's disease (CD), a chronic inflammatory bowel disease (IBD), occurs in genetically susceptible individuals who develop aberrant immune responses to endoluminal bacteria. Recurrent inflammation increases the risk of several complications. Despite use of a traditional "step-up" therapy with corticosteroids and immunomodulators, most CD patients eventually require surgery at some time in their disease course. Newer biologic agents have been remarkably effective in controlling severe disease. Thus, "top-down," early aggressive therapy has been proposed to yield better outcomes, especially in complicated disease. However, safety and cost issues mandate the need for careful patient selection. Identification of high-risk candidates who may benefit from aggressive therapy is becoming increasingly relevant. Serologic and genetic markers of CD have great potential in this regard. The aim of this review is to highlight the clinical relevance of these markers for diagnostics and prognostication.

METHODS

A current PubMed literature search identified articles regarding the role of biomarkers in IBD diagnosis, severity prediction, and stratification. Studies were also reviewed on the presence of IBD markers in non-IBD diseases.

RESULTS

Several IBD seromarkers and genetic markers appear to be associated with complex CD phenotypes. Qualitative and quantitative serum immune reactivity to microbial antigens may be predictive of disease progression and complications.

CONCLUSION

The cumulative evidence provided by serologic and genetic testing has the potential to enhance clinical decision-making when formulating individualized IBD therapeutic plans.

Combined azithromycin and metronidazole therapy is effective in inducing remission in pediatric Crohn's disease

BACKGROUND

Crohn's disease (CD) is characterized by an aberrant response to the gut microbiota. We aimed to assess whether azithromycin based therapy is effective in inducing remission in CD, due to its effect in inducing apoptosis and efficacy against biofilms and intracellular bacteria.

METHODS

Retrospective analysis of patients treated with an 8 week course of combined azithromycin and metronidazole. Patients were included if they had active CD defined as pediatric CD activity index (PCDAI) ≥ 10, and were not receiving any other medication for inducing remission in active disease. PCDAI score and CRP were recorded at baseline and 8 weeks thereafter.

RESULTS

Thirty two patients (mean age 13.1 ± 3.9, mean duration of disease 0.65 years) were included, of whom 21 (66%) entered clinical remission (PCDAI<10) after 8 weeks of treatment. The mean age at treatment and duration of disease did not differ between patients entering remission and those unresponsive to therapy. CRP, normalized in 54% of patients with elevated CRP at baseline. Factors associated with lack of response were a more severe disease (reflected by higher PCDAI and CRP values at baseline), presence of arthritis and extensive disease (ileocolonic, or prominent upper intestinal disease).

CONCLUSIONS

An 8 week course of azithromycin and metronidazole therapy may be effective in inducing clinical remission in mild-moderate luminal CD in children and young adults.

Distinct IFNG methylation in a subset of ulcerative colitis patients based on reactivity to microbial antigens

BACKGROUND

High antibody reactivity toward microbial antigens in Crohn's disease (CD) patients is predictive of a more aggressive disease course. However, few ulcerative colitis (UC) patients exhibit serologic reactivity toward microbial antigens. Mucosal expression of IFN-γ plays a pivotal role in inflammatory bowel disease (IBD) pathogenesis. Recent genome-wide association studies (GWAS) surprisingly link UC, but not CD, risk loci to IFNG. We recently demonstrated that mucosal T cells from IBD patients exhibit distinct patterns of IFNG methylation compared to controls. This study evaluated the relationship between IFNG methylation and serologic and clinical profiles in peripheral T cells from IBD patients.

METHODS

DNA from peripheral T cells of 163 IBD patients (91 CD and 64 UC) and 42 controls was analyzed for methylation of eight IFNG sites. Serum markers ASCA, OmpC, I2, CBir, and pANCA were measured by enzyme-linked immunosorbent assay (ELISA). IFN-γ secretion was measured by ELISA.

RESULTS

IBD patients requiring surgery exhibited reduced IFNG methylation compared to nonsurgical patients (P < 0.02). Enhancement of IFN-γ secretion (P < 0.003), along with high antibody responses toward multiple microbial antigens (P < 0.017) in UC, but not CD, patients was correlated with decreased IFNG methylation. pANCA levels were not correlated with IFNG methylation.

CONCLUSIONS

Levels of IFNG methylation were correlated with immune response to microbial components and expression of IFN-γ in UC patients. Serological and epigenetic markers identify a subset of UC patients with an expression profile of a key TH1 pathogenic cytokine. These data may provide a useful tool to classify a more homogeneous subset of UC patients, allowing for improved diagnostics and targeted therapeutics.

Body traffic: ecology, genetics, and immunity in inflammatory bowel disease

The abundant bacteria and other microbial residents of the human intestine play important roles in nutrient absorption, energy metabolism, and defense against microbial pathogens. The mutually beneficial relationship of host and commensal microbiota represents an ancient and major coevolution in composition and mutual regulation of the human mucosa and the resident microbial community. Inflammatory bowel disease (IBD) is a set of chronic, relapsing inflammatory intestinal diseases in which rules of normal host-microbial interaction have been violated. This review considers the components of this host-microbial mutualism and the ways in which it is undermined by pathogenic microbial traits and by host immune and epithelial functions that confer to them susceptibility in patients with IBD. Recent advances in understanding the genetics of IBD and the immunology of host-microbial interaction are opening new strategies for treatments that target host susceptibility, candidate microbial pathogens, and intestinal ecology.

Microbial host interactions in IBD: implications for pathogenesis and therapy

Crohn's disease (CD), ulcerative colitis (UC), and pouchitis appear to be caused by pathogenic T-cell responses to discrete antigens from the complex luminal microbiota, with susceptibility conferred by genetic polymorphisms that regulate bacterial killing, mucosal barrier function, or immune responses. Environmental triggers initiate or reactivate inflammation and modulate genetic susceptibility. New pathogenesis concepts include defective bacterial killing by innate immune cells in CD, colonization of the ileum in CD with functionally abnormal Escherichia coli that adhere to and invade epithelial cells and resist bacterial killing, and alterations in enteric microbiota composition in CD, UC, and pouchitis detected by molecular probes. The considerable therapeutic potential of manipulating the enteric microbiota in inflammatory bowel disease patients has not been realized, probably due to failure to recognize heterogenic disease mechanisms that require individualized use of antibiotics, probiotics, prebiotics, combination therapies, and genetically engineered bacteria to restore mucosal homeostasis.

Microbial influences in inflammatory bowel diseases

The predominantly anaerobic microbiota of the distal ileum and colon contain an extraordinarily complex variety of metabolically active bacteria and fungi that intimately interact with the host's epithelial cells and mucosal immune system. Crohn's disease, ulcerative colitis, and pouchitis are the result of continuous microbial antigenic stimulation of pathogenic immune responses as a consequence of host genetic defects in mucosal barrier function, innate bacterial killing, or immunoregulation. Altered microbial composition and function in inflammatory bowel diseases result in increased immune stimulation, epithelial dysfunction, or enhanced mucosal permeability. Although traditional pathogens probably are not responsible for these disorders, increased virulence of commensal bacterial species, particularly Escherichia coli, enhance their mucosal attachment, invasion, and intracellular persistence, thereby stimulating pathogenic immune responses. Host genetic polymorphisms most likely interact with functional bacterial changes to stimulate aggressive immune responses that lead to chronic tissue injury. Identification of these host and microbial alterations in individual patients should lead to selective targeted interventions that correct underlying abnormalities and induce sustained and predictable therapeutic responses.

Serologic markers in inflammatory bowel disease: tools for better diagnosis and disease stratification

In the last decade, new serologic markers have been identified, and attempts to delineate their potential roles in inflammatory bowel disease diagnosis, determination of prognosis and identification of apparently healthy subjects at risk have significantly increased our knowledge. In this review, the major serologic markers will be described, focusing on their common features as a group. It is predicted that within the next 5 years, panels of antibodies will prove to have a significant impact on disease diagnosis and stratification, as well as on the identification of populations at risk and the prediction of response to treatment. Thus, it is expected that they will become useful clinical tools that will enable an improved, 'tailored' approach to inflammatory bowel disease patients.

Dual-association of gnotobiotic IL-10-/- mice with 2 nonpathogenic commensal bacteria induces aggressive pancolitis

BACKGROUND

Monoassociating gnotobiotic IL-10-deficient (-/-) mice with either nonpathogenic Enterococcus faecalis or a nonpathogenic Escherichia coli strain induces T-cell-mediated colitis with different kinetics and anatomical location (E. faecalis: late onset, distal colonic; E. coli: early onset, cecal).

HYPOTHESIS

E. faecalis and E. coli act in an additive manner to induce more aggressive colitis than disease induced by each bacterial species independently.

METHODS

Germ-free (GF) inbred 129S6/SvEv IL-10-/- and wildtype (WT) mice inoculated with nonpathogenic E. faecalis and/or E. coli were killed 3-7 weeks later. Colonic segments were scored histologically for inflammation (0 to 4) or incubated in media overnight to measure spontaneous IL-12/IL-23p40 secretion. Bacterial species were quantified by serial dilution and plated on culture media. Mesenteric lymph node (MLN) CD4(+) cells were stimulated with antigen-presenting cells pulsed with bacterial lysate (E. faecalis, E. coli, Bacteroides vulgatus) or KLH (unrelated antigen control). IFN-gamma and IL-17 levels were measured in the supernatants.

RESULTS

Dual-associated IL-10-/- (but not WT) mice developed mild-to-moderate pancolitis by 3 weeks that progressed to severe distal colonic-predominant pancolitis with reactive atypia and duodenal inflammation by 7 weeks. NF-kappaB was activated in the duodenum and colon in dual-associated IL-10-/- x NF-kappaB(EGFP) mice. The aggressiveness of intestinal inflammation and the degree of antigen-specific CD4(+) cell activation were greater in dual- versus monoassociated IL-10-/- mice.

CONCLUSION

Two commensal bacteria that individually induce phenotypically distinct colitis in gnotobiotic IL-10-/- mice act additively to induce aggressive pancolitis and duodenal inflammation.

Adherent-invasive Escherichia coli in inflammatory bowel disease

Increased numbers of mucosa-associated Escherichia coli are observed in both major inflammatory bowel diseases, Crohn's disease (CD) and ulcerative colitis (UC). With the identification of mutations in the NOD2-encoding gene in patients with CD and given the intracellular location of NOD2, the presence of pathogenic invasive bacteria could be the link between innate immune response to invasive bacteria and the development of the inflammation. Adherent-invasive E. coli (AIEC) are isolated from ileal biopsies of 36.4% of patients with ileal involvement of CD. These pathogenic E. coli colonize the intestinal mucosa by adhering to intestinal epithelial cells and are also true invasive pathogens, able to invade intestinal epithelial cells and to replicate intracellularly. AIEC strains also survive and replicate extensively within macrophages without inducing host cell death, and their high replication rates induce the secretion of large amounts of tumor necrosis factor alpha (TNF-alpha). There is also evidence suggesting that AIEC is involved in the formation of granulomas. The presence of AIEC is restricted to CD patients. Mucosa-associated E. coli in patients with UC can adhere to intestinal epithelial cells and induce the secretion of IL-8, but there is no evidence that these E. coli strains are invasive.

The immune response in inflammatory bowel disease

Ulcerative colitis (UC) and Crohn's disease (CD), collectively referred to as inflammatory bowel disease (IBD), present with differing histologic and cytokine profiles. While the precise mechanisms underlying the development of IBD are not known, sufficient data have been collected to suggest that it results from a complex interplay of genetic, environmental, and immunologic factors. Animal models of colitis, along with a more detailed understanding of the immune response in the normal bowel, have led to unifying hypotheses regarding the pathogenesis. An inappropriate mucosal immune response to normal intestinal constituents is a key feature, leading to an imbalance in local pro- and anti-inflammatory cytokines. Neutrophil and monocyte influx occurs with subsequent secretion of oxygen radicals and enzymes, leading to tissue damage. Therapy of IBD has improved and expanded as the understanding of disease mechanisms has evolved. Pharmacologic agents such as aminosalicylates, azathioprine/6-mercaptopurine, or steroids are the mainstays of therapy. Newer agents including monoclonal antibodies targeted to specific proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), have emerged and provide great clinical benefit, but unknown long-term toxicity and immunogenicity may limit their use.

[Relevance of serologic studies in inflammatory bowel diseases]

The panel of serologic markers for inflammatory bowel diseases (IBDs) is rapidly expanding. Although anti- Saccharomyces cerevisiae antibodies (ASCA) and atypical perinuclear antineutrophil cytoplasmic antibodies (atypical P-ANCA) remain the most widely investigated, an increasing amount of experimental data is available on newly discovered antibodies directed against various microbial antigens. Such antibodies include anti-OmpC (outer membrane porin C), anti- Pseudomonas fluorescens (anti-I2) and antiglycan antibodies (anti-laminaribioside carbohydrate antibody [ALCA]), anti-chitobioside carbohydrate antibody [ACCA]), anti-mannobioside carbohydrate antibody [AMCA]) and anti-CBir1; this latter is the first bacterial antigen to induce colitis in animal models of IBD and also leads to a pathological immune response in IBD patients (anti-flagellin antibody). The role of assessment of various antibodies in the current diagnostic algorithm of IBD is rather questionable due to their limited sensitivity. In contrast, the association of serologic markers with disease behavior and phenotype is getting more into the focus of interest. An increasing number of observations confirm that patients with Crohn's disease expressing multiple serologic markers at high titers are more likely to have complicated small bowel disease (e.g. stricture and/or perforation) and are at higher risk for surgery than those without, or with low titer of antibodies. Creating homogenous disease sub-groups based on serologic response may help develop more standardized therapeutic approaches and may help in a better understanding of the pathomechanism of IBD. Further prospective clinical studies are needed to establish the clinical role of serologic tests in IBD.

Utility of serological markers in inflammatory bowel diseases: gadget or magic?

The panel of serologic markers for inflammatory bowel diseases (IBD) is rapidly expanding. Although anti-Saccharomyces cerevisiae antibodies (ASCA) and atypical perinuclear antineutrophil cytoplasmic antibodies (P-ANCA) remain the most widely investigated, an increasing amount of experimental data is available on newly discovered antibodies directed against various microbial antigens. The role of the assessment of various antibodies in the current IBD diagnostic algorithm is often questionable due to their limited sensitivity. In contrast, the association of serologic markers with disease behavior and phenotype is becoming increasingly well-established. An increasing number of observations confirms that patients with Crohn's disease expressing multiple serologic markers at high titers are more likely to have complicated small bowel disease (e.g. stricture and/or perforation) and are at higher risk for surgery than those without, or with low titers of antibodies. Creating homogenous disease sub-groups based on serologic response may help develop more standardized therapeutic approaches and may help in a better understanding of the pathomechanism of IBD. Further prospective clinical studies are needed to establish the clinical role of serologic tests in IBD.

NOD2 variants and antibody response to microbial antigens in Crohn's disease patients and their unaffected relatives

BACKGROUND & AIMS

The Cdcs1 locus of the C3Bir mouse confers severe colitis associated with a decrease in innate immune function and an increase in adaptive T-cell responses to commensal bacterial products. The aim of our study was to determine if defects in innate immunity are similarly associated with increased adaptive immune responses to microbial antigens in Crohn's disease patients.

METHODS

Sera from 732 patients, 220 unaffected relatives, and 200 healthy controls were tested for antibodies to oligomannan, the Pseudomonas fluorescens-related protein, Escherichia coli outer membrane porin C, CBir1 flagellin, and DNA from the same subjects was tested for 3 Crohn's disease-associated variants of the NOD2 gene, and 5 toll-like receptor (TLR) 2, 2 TLR4, and 2 TLR9 variants. The magnitude of responses to microbial antigens was examined according to variant status.

RESULTS

NOD2 variant carriage increased in frequency with increasing number of positive antibodies and increasing cumulative quantitative response as measured by quartile sum (P for trend, .0008 and .0003, respectively). Mean antibody and quartile sums were higher for patients carrying any NOD2 variant versus those carrying none (2.24 vs 1.92 and 10.60 vs 9.72; P = .0008 and P = 0.0003, respectively). The mean quartile sum was higher for unaffected relatives carrying any NOD2 variant versus those carrying none (10.67 vs 9.75, respectively; P = .02). No association was found between any TLR variant and the magnitude of response.

CONCLUSIONS

Patients with Crohn's disease and unaffected relatives carrying variants of the NOD2 gene have increased adaptive immune responses to microbial antigens.

Commensal bacteria exacerbate intestinal inflammation but are not essential for the development of murine ileitis

The pathogenesis of Crohn's disease has been associated with a dysregulated response of the mucosal immune system against intraluminal Ags of bacterial origin. In this study, we have investigated the effects of germfree (GF) conditions in the SAMP1/YitFc murine model of Crohn's disease-like ileitis. We show that the bacterial flora is not essential for ileitis induction, because GF SAMP1/YitFc mice develop chronic ileitis. However, compared with disease in specific pathogen-free (SPF) mice, ileitis in GF mice is significantly attenuated, and is associated with delayed lymphocytic infiltration and defective mucosal expression of Th2 cytokines. In addition, we demonstrate that stimulation with purified fecal Ags from SPF, but not GF mice leads to the generation of IL-4-secreting effector lymphocytes. This result suggests that commensal bacteria drive Th2 responses characteristic of the chronic phase of SAMP1/YitFc ileitis. Finally, adoptive transfer of CD4-positive cells from GF, but not SPF mice induces severe colitis in SCID recipients. These effects were associated with a decreased frequency of CD4(+)CD25(+)Foxp3(+) T cells in the mesenteric lymph nodes of GF mice compared with SPF mice, as well as lower relative gene expression of Foxp3 in CD4(+)CD25(+) T cells in GF mice. It is therefore apparent that, in the absence of live intraluminal bacteria, the regulatory component of the mucosal immune system is compromised. All together, our results indicate that in SAMP1/YitFc mice, bacterial flora exacerbates intestinal inflammation, but is not essential for the generation of the chronic ileitis that is characteristic of these mice.

Antibiotic therapy for Crohn's disease: a review

Increasing evidence suggests that gut bacteria play a pathogenic role in Crohn's disease (CD), providing a rationale for the use of antibiotics in the primary treatment of the disease. While there are data to suggest that antibiotics may be effective in treating active luminal, particularly colonic, and/or perianal CD, evidence for their use in these settings is hampered by the lack of well-designed, adequately powered, placebo-controlled trials. Furthermore, although nitroimidazole antibiotics have been shown to reduce postoperative recurrence following ileocolonic resection, their use is limited by side effects. There is a current need for rigorous multicentre studies looking into the role of antibiotics in treating perianal and luminal CD, as well as a need for the large-scale assessment of novel antibiotics, with low systemic absorption, which may improve patient tolerance.

Adherent-invasive Escherichia coli and Crohn's disease

PURPOSE OF REVIEW

The identification of mutations in the nucleotide oligomerization domain 2-encoding gene in patients with Crohn's disease suggests a link between the innate immune response to invasive bacteria and the development of Crohn's disease. Herein, we review reports concerning the association of pathogenic Escherichia coli with the intestinal mucosa of Crohn's disease patients.

RECENT FINDINGS

Adherent-invasive E. coli were isolated from ileal biopsies of 36.4% of patients with ileal Crohn's disease. Adherent-invasive E. coli colonize the intestinal mucosa by adhering to intestinal epithelial cells. They are also true invasive pathogens, able to invade intestinal epithelial cells and to replicate intracellularly. Adherent-invasive E. coli strains replicate extensively into macrophages inducing the secretion of very large amounts of tumor necrosis factor-alpha. Similar pathogenic E. coli strains were recently associated with granulomatous colitis of Boxer dogs. Interestingly, high levels of E. coli outer membrane protein C antibodies are present in 37-55% of Crohn's disease patients and reactivity to outer membrane protein C is associated with increased severity of Crohn's disease.

SUMMARY

As the infection cycle of adherent-invasive E. coli could depend upon the ability of these pathogenic bacteria to colonize the gastrointestinal tract of genetically predisposed Crohn's disease patients, antibiotics which could eradicate the bacteria, or probiotics which could substitute them in the gastrointestinal tract, could be of therapeutic value in ileal Crohn's disease.

Antibodies against laminaribioside and chitobioside are novel serologic markers in Crohn's disease

BACKGROUND & AIMS

New serologic markers of inflammatory bowel disease may be useful for differentiating between Crohn's disease and ulcerative colitis and for disease stratification. We profiled sugar-binding antibodies to identify novel antiglycan antibodies that may be associated with inflammatory bowel disease.

METHODS

Serum samples were obtained from patients with diagnosed Crohn's disease or ulcerative colitis and from control patients. The presence of antiglycan antibodies was evaluated using either a glycan array (GlycoChip; Glycominds, Ltd, Lod, Israel) in patients with Crohn's disease (n = 72) or ulcerative colitis (n = 56) and in healthy controls (n = 41) or using an enzyme-linked immunosorbent assay in patients with Crohn's disease (n = 124), ulcerative colitis (n = 106), and in control patients (n = 101).

RESULTS

Inaddition to antibodies against mannan, antibodies to laminaribioside (Glc[beta1,3]Glc[beta]) and chitobioside (GlcNAc[beta1,4]GlcNAc[beta]) had the highest discriminative capability between Crohn's disease and ulcerative colitis (P < .001 and P < .05, respectively). Importantly, 44% (12/27) of anti-Saccharomyces cerevisiae antibody-negative Crohn's disease patients were positive for antilaminaribioside or antichitobioside. In patients with inflammatory bowel disease positive for antibodies against either laminaribioside, chitobioside, or mannan, the diagnosis of Crohn's disease was suggested with a sensitivity of 77.4% and specificity of 90.6%. Having at least 2 of these antibodies increased the specificity to 99.1%. In Crohn's disease, higher levels of antibodies against laminaribioside or mannan were significantly associated with small intestinal disease (P = .03 and P < .0001, respectively).

CONCLUSIONS

Antilaminaribioside and antichitobioside carbohydrate antibodies are novel serologic markers associated with Crohn's disease. These antibodies may contribute to the diagnosis and improved stratification of Crohn's disease.

Familial expression of anti-Escherichia coli outer membrane porin C in relatives of patients with Crohn's disease

BACKGROUND & AIMS

Crohn's disease (CD) is a genetically complex disorder with strong familial aggregation. Pathogenesis appears to involve dysregulation of the immune response to endogenous bacteria. Anti-Escherichia coli outer membrane porin C (anti-OmpC) expression reflects an exaggerated response to commensal bacteria and occurs with higher frequency in CD. The aim of this study was to determine whether there is familial aggregation and genetic determination of anti-OmpC expression in CD families.

METHODS

Study groups consisted of 787 CD patients, 389 ulcerative colitis (UC) patients, 619 unaffected relatives, and 216 healthy controls. Serum anti-OmpC was detected by enzyme-linked immunosorbent assay.

RESULTS

CD patients had a greater percentage of anti-OmpC than UC patients and healthy controls. Anti-OmpC expression was more frequent in unaffected relatives from CD-only or mixed families, compared with healthy controls (P = .002 and .0001, respectively), and it was more frequent in UC patients from mixed families than those from UC-only families (P = .02). There was a significant familiality in anti-OmpC expression: P = .02 for qualitative concordance and P < .0001 for quantitative intraclass correlation. The heritability estimate for anti-OmpC level was .39 (P < .0001).

CONCLUSIONS

Anti-OmpC is a heritable immunophenotype. Increased anti-OmpC expression in the unaffected family members of CD patients suggests that anti-OmpC may be an immunologic risk marker for CD. That UC patients in mixed families had a higher response to OmpC than those in UC-only families indicates pathophysiologic heterogeneity within UC.