Selected loss of tolerance evidenced by Crohn's disease-associated immune responses to auto- and microbial antigens

Pancreatic autoantibodies in Crohn's disease: a feasible diagnostic tool?

Potential implications of antibody markers in Crohn's disease: Diagnostic markers, alone or in conjunction with other antibodies? Delineation of clinical phenotypes? Markers of disease behaviour? Markers of (genetic) susceptibility? Identification of genetically homogenous subgroups? Bridge between basic science and clinic? The exact role of serum antibodies in inflammatory bowel disease remains a matter of ongoing debate. Although a direct implication in the disease pathogenesis is unlikely, their diagnostic potential in cases of an undetermined colitis or in defining clinical phenotypes in Crohn's disease has been shown in several studies. Serum antibodies might also be helpful in predicting the disease behaviour and are thus valuable tools in the choice of medical or surgical therapy.

New insights into the pathogenesis of inflammatory bowel disease

Several important advances have been made over the past few years that have expanded our knowledge of the immunology of the gut and its complex interactions with commensal organisms. Critical developments in our understanding of the pathogenesis of inflammatory bowel diseases include the discovery of Toll-like receptors and the identification of not one but two susceptibility genes for Crohn's disease. We have furthered our understanding significantly concerning the role of dendritic cells in the development of gut inflammation. In addition, a novel hypothesis suggesting a protective role for helminthic infections is gaining experimental evidence and direct clinical applicability. In this review we summarize these key developments in the pathophysiology of inflammatory bowel disease and attempt to ascribe clinical relevance where applicable.

Relevance of serologic studies in inflammatory bowel disease

The serologic panel for inflammatory bowel disease (IBD) is rapidly expanding. Antineutrophil cytoplasmic antibodies (ANCA) and anti-Saccharomyces cerevisiae mannan antibodies (ASCA) have remained the most widely studied markers, but immune reactivity against a new group of bacterial antigens such as I2, OmpC (outer membrane porin C), and flagellin, has been described in Crohn's disease. Several clinical avenues have been explored, such as the usefulness of serologic markers as screening tools for IBD and in accelerating a diagnosis in patients with indeterminate colitis. Another area of interest is disease stratification. Emerging data suggest there is a diversity of qualitative and quantitative responses to environmental antigens that differs among groups of IBD patients and may be associated with different clinical behaviors. As a result, it may be possible to tailor therapy on the basis of serologic responses. Prospective studies are needed before translating this concept into clinical practice. Clustering of IBD patients into more homogeneous subgroups based on antibody responses may help to unravel the pathophysiology of subsets of IBD.

Sero-reactivity to microbial components in Crohn's disease is associated with disease severity and progression, but not NOD2/CARD15 genotype

BACKGROUND AND AIMS

Antibodies directed against the porin protein C of Escherichia coli (anti-OmpC) and Pseudomonas fluorescens (anti-I2) have recently been described in Crohn's disease (CD). Those directed against Saccharomyces cerevisiae (ASCA) and the perinuclear component of neutrophils (pANCA) have been more widely studied and may be of diagnostic importance. We aimed to assess the frequency of anti-OmpC, anti-I2, ASCA, and pANCA, in an independent Scottish CD cohort, establish phenotypic associations, and compare with a U.S. cohort.

METHODS

One hundred and forty-two well-characterized CD patients (76 females, median age 39 yr (17-88)) were studied. CD was classified by the Vienna classification. Sera were assayed for anti-OmpC, anti-I2, ASCA, and pANCA. Allele specific primers were used for NOD2/CARD15 genotyping.

RESULTS

Anti-OmpC, anti-I2, ASCA, and pANCA were present in sera from 37%, 52%, 39%, and 14% of CD patients, respectively. Multivariate analysis demonstrated independent associations of anti-OmpC to be progression of disease type (p= 0.005) and long disease duration (p= 0.002), and those of anti-I2 to be long disease duration (p= 0.002) and the need for surgery (p= 0.033). ASCA were associated with disease progression (p < 0.001). When the presence and magnitude of all antibody responses were considered, reactivity to microbial components was associated with long disease duration (p < 0.001), progression of disease type (p < 0.001), penetrating disease (p= 0.008), small bowel disease (p < 0.02), and the need for surgery (p < 0.001). There was no association of antibody status to NOD2/CARD15 genotype.

CONCLUSION

Reactivity to microbial components is associated with severe CD characterized by small bowel involvement, frequent disease progression, longer disease duration, and greater need for intestinal surgery.

Serologic testing with ANCA, ASCA, and anti-OmpC in children and young adults with Crohn's disease and ulcerative colitis: diagnostic value and correlation with disease phenotype

OBJECTIVES

Serologic testing is increasingly being utilized to evaluate children with suspected inflammatory bowel disease (IBD). The aim of this paper was to evaluate the sensitivity and specificity of a currently available panel involving four antibodies: deoxyribonuclease (DNase)-sensitive perinuclear antineutrophil cytoplasmic antibody (DNase-sensitive pANCA), IgA and IgG antibodies to Saccharomyces cerevisiae (IgA and IgG ASCA), and antibody to Escherichia coli outer membrane porin (anti-OmpC). We also wished to determine whether antibody levels correlated with disease activity, and whether a specific antibody pattern correlated with location and outcome of disease in children.

METHODS

We studied sera from 81 children with Crohn's disease (CD), 54 with ulcerative colitis (UC), and 63 controls. Clinical data, disease activity, and disease diagnosis were gathered at the time of serum sampling, and charts were re-reviewed at time of the study to determine long-term outcome. Enzyme-linked immunosorbent assay was utilized to determine titers of antibodies to ASCA, DNase-sensitive pANCA, and anti-OmpC; the presence of perinuclear staining for ANCA was confirmed by immunofluorescence.

RESULTS

We identified ASCA antibodies in 44% of CD patients, 0% of UC patients, and 1 control patient. DNase-sensitive pANCA antibodies were found in 70% of patients with UC, 18% of CD patients (predominantly Crohn's colitis), and 3% of controls. Anti-OmpC as an isolated assay had low sensitivity for both CD (24%) and UC (11%), and displayed a 5% false-positive rate. However, anti-OmpC did identify a small number of IBD patients not detected by the other assays. If any one or more of the four antibodies was positive, the overall sensitivity of the four antibody panel was 65% for CD and 76% for UC, with a specificity of 94%. Patients who were ASCA-positive were more likely to have disease of the ileum or ileum and right colon than patients who were ASCA-negative (58%vs 18%, p < 0.001). Patients with ASCA-positive were also more likely to require ileocecal resection (36%vs 13%, p < 0.05).

CONCLUSIONS

A currently available commercial antibody panel has good sensitivity and excellent specificity for CD and UC. The ASCA antibodies, while highly specific for CD, identify predominantly the subset of children with disease of the ileum and ascending colon who may be at increased risk of surgery.

Update on the etiology, pathogenesis and diagnosis of ulcerative colitis

Evidence is accumulating that both genetic and environmental factors contribute to ulcerative colitis. The most consistent genetic associations have been shown for the MHC locus HLA Class II alleles, but the interleukin-1 family of genes and the multidrug resistance gene MDR1 have also been implicated as genetic susceptibility factors for the development of disease. In addition, there is a relationship between ulcerative colitis and bacterial flora, with an increased number of adherent Bacteroides spp. and Enterobacteriaceae spp. present in inflamed bowel segments. Conversely, cigarette smoking and appendectomy have both been shown to protect against the development of ulcerative colitis. Despite our improved understanding of the genetics and inflammatory mechanisms that underpin this disease, however, the etiology and pathogenesis of ulcerative colitis remain undefined. The diagnosis of ulcerative colitis is being aided by recent advances in diagnostic strategies, including the detection of fecal and serologic markers and the use of wireless capsule endoscopy, but, in the absence of a pathognomonic marker, the definition of this disease remains based on well-established clinical, endoscopic and histologic criteria. In particular, it is difficult to discriminate ulcerative colitis from other forms of colitis, including Crohn's disease, and there seems to be a growing overlap of pathophysiologic processes between ulcerative colitis and post-infectious irritable bowel syndrome. Patients who remain indeterminate between ulcerative colitis and Crohn's disease also continue to be a diagnostic challenge.

Toll-like receptor 4 and CD14 expression in human ciliary body and TLR-4 in human iris endothelial cells

We investigated the expression of the functional endotoxin receptor proteins Toll-like receptor-4 and CD14 in human eyes. Toll-like receptor-4 and CD14 proteins were detected by immunohistochemical analysis of sections of whole human eyes embedded in paraffin with monoclonal antibodies against human toll-like receptor-4 (HTA-125), human CD14 (RPA-M1), or as a control, an irrelevant mouse IgG1k (MOPC-21). Incubation of explants with a neutralizing anti-toll-like receptor-4 monoclonal antibody was used to determine if lipopolysaccharide stimulation of tumor necrosis factor or interleukin-6 secretion was dependent on Toll-like receptor-4 activity. Reverse transcription-polymerase chain reaction was used to detect mRNAs for toll-like receptor-4, tumor necrosis factor-alpha, interleukin-1beta, interleukin-6 and interleukin-8, 3 hr after stimulation of cultured iris microvascular endothelial cells. By immunohistochemistry, human ciliary body non-pigmented epithelial cells showed strong expression of the endotoxin receptor proteins, toll-like receptor-4 and CD14. Toll-like receptor-4 antibodies significantly inhibited lipopolysaccharide-stimulated tumor necrosis factor secretion by the ciliary body. Toll-like receptor-4 mRNA was constitutively expressed in iris endothelial cells and slightly down-regulated by endotoxin. mRNA levels for tumor necrosis factor-alpha, interleukin-1beta, interleukin-6 and interleukin-8 were all increased by endotoxin treatment. This is the first report that shows intraocular (ciliary body and iris) expression of toll-like receptor-4, other than in cornea. Our results show that the ciliary body also expresses CD14, which is anatomically colocalized with toll-like receptor-4. This suggests a potential interaction between both molecules during endotoxin activation of ciliary body cells. The juxtaposition of toll-like receptor-4 and CD14 in the anterior uveal tract helps to explain the sensitivity of the iris/ciliary body to bacterial endotoxin as seen in the standard animal model of endotoxin-induced uveitis.

Disease location, anti-Saccharomyces cerevisiae antibody, and NOD2/CARD15 genotype influence the progression of disease behavior in Crohn's disease

BACKGROUND

Crohn's disease (CD) is characterized by heterogeneity of phenotype. The Vienna classification can be used to classify CD, and recent data illustrate that behavior evolves over the course of the disease. Clinical and biological influences on disease progression remain unclear. We examined the associations of CD disease progression at diagnosis and for up to 20 years of follow-up.

METHODS

Two hundred thirty-one well-characterized CD patients were studied. Demographic, clinical, and NOD2/CARD15 data were collected. Disease behavior according to the Vienna classification was assessed at diagnosis and for up to 20 years following diagnosis.

RESULTS

At diagnosis, 70% of patients had inflammatory disease, 9% stricturing, and 21% penetrating. Early age at diagnosis was associated with ileocolonic and upper GI disease (p = 0.015), and positive anti-Saccharomyces cerevisiae antibody (ASCA) was associated with ileal involvement (p = 0.008). Smoking was relatively protective against colonic, rather than ileal involvement at diagnosis (p < 0.02). At 20 years, 92% had progressed to a more severe disease type. Patients who progress to a more severe disease type require more frequent surgery (p < 0.00001). Multivariate analysis found disease progression to be associated with ileal disease location (p = 0.001) and positive ASCA (p = 0.003). Variant NOD2/CARD15 alleles were protective against rapid progression of disease phenotype (p = 0.04). The presence of perianal disease was independent of intestinal penetrating disease.

CONCLUSIONS

The progression of disease type in CD is associated with the need for more frequent surgery. Rapid progression is associated with ileal disease and positive ASCA, and delayed progression is associated with variant NOD2/CARD15 alleles. Consideration should be given to a separate Vienna classification for perianal disease.

Characterization and distribution of colonic dendritic cells in Crohn's disease

Dendritic cells (DCs) are thought to play an important role in the pathogenesis of autoimmune inflammation, including Crohn's disease (CD). We investigated the distribution and state of maturation of DCs in the colon in relation to the severity of inflammation and therapy. Using archival specimens from colonic resections in 19 pediatric patients with CD and 14 controls, we identified and characterized the DCs within the lamina propria, submucosa, and muscularis compartments using morphologic and quantitative immunohistochemical methods. The distribution of CD11c+CD83+CD68+DC-SIGN+ and immature CD11c+CD83-CD68-DC-SIGN+ DCs within the different compartments varied according to the presence or absence of CD as well as to the severity of inflammation and systemic corticoid treatment. Immature DCs were only found in non-inflamed control colonic tissue. Marked reductions (60% and 30%) in total CD11c and CD83 DC numbers were observed in CD tissue samples compared with controls (P < 0.05). CD samples from patients on corticosteroid therapy were significantly more depleted than in tissue from untreated patients or those on other drugs. Colonic tissue with severe inflammation had reduced numbers of CD11c+ and CD83+ DCs in the lamina propria and submucosal compartments (80% and 76% for CD11c; 75% and 76% for CD83, respectively, P < 0.05), with a concomitant increase (525% for CD11c and 700% for CD83 P < 0.05) of DCs in the muscularis compartment, compared to moderately inflamed and non-inflamed CD tissue. Our data suggest that an imbalance in intestinal DC subpopulations may play a role in the initiation and/or the maintenance of chronic inflammation in CD. Corticosteroid therapy is associated with colonic DC depletion.

Expanded B cell population blocks regulatory T cells and exacerbates ileitis in a murine model of Crohn disease

SAMP1/YitFc mice develop discontinuous, transmural inflammatory lesions in the terminal ileum, similar to what is found in human Crohn disease. Compared with the mesenteric lymph nodes (MLNs) of AKR control mice, SAMP1/YitFc MLNs contain a 4.3-fold expansion in total B cell number and a 2.5-fold increased percentage of CD4(+) T cells expressing the alpha(E)beta(7) integrin. Although alpha(E)beta(7)(+)CD4(+) T cells possess a regulatory phenotype (CD25(+), L-selectin(lo), and CD45RB(lo)), express IL-10, and suppress effector T cell proliferation in vitro, they cannot prevent ileitis development in SCID mice adoptively transferred with effector CD4(+) T cells, although the CD4(+)CD25(+) subset, which overlaps with the alpha(E)beta(7)(+)CD4(+) subset, prevents colitis. The alpha(E)beta(7)(+)CD4(+) T cells express high levels of ICOS, a costimulatory molecule that augments B cell function, suggesting their involvement in the increase in B cells, IgA(+) cells, and soluble IgA found within the MLNs and ileum of SAMP1/YitFc mice. MLN B cell numbers correlate with ileitis severity in SAMP1/YitFc mice, and cotransfer of SAMP1/YitFc MLN B cells along with CD4(+) T cells increases ileitis severity in SCID mice compared with transfer of CD4(+) T cells alone. SAMP1/YitFc B cells prevent alpha(E)beta(7)(+)CD4(+) T cells from suppressing effector T cell proliferation. We conclude that SAMP1/YitFc MLN B cells contribute to the development of SAMP1/YitFc ileitis.

Biomarkers in inflammatory bowel disease

PURPOSE OF REVIEW

Inflammatory bowel disease is characterized by chronic intestinal inflammation in the absence of a recognized pathogen. In its classic description, there are two principal forms of inflammatory bowel disease: Crohn disease and ulcerative colitis. The clinical heterogeneity of these disorders alludes to the possibility of diverse pathogenetic mechanisms underlying inflammatory bowel diseases. The purpose of this review is to summarize the latest information on biomarkers of Crohn disease and ulcerative colitis.

RECENT FINDINGS

The authors have focused on serologic markers for which emerging data support their use as predictors of disease evolution. Serologic markers such as perinuclear antineutrophil cytoplasmic antibody, anti-Saccharomyces cerevisiae antibody, anti-OmpC, and anti-I2 may be useful in distinguishing inflammatory bowel diseases from functional disorders and ulcerative colitis from Crohn disease and predicting complications of disease. Genetic markers such as CARD15/NOD2 may be useful in the future when combined with other markers to predict disease course. Biochemical markers of inflammation such as C-reactive protein are useful to stratify patients likely to respond to biologic therapies and to follow response to treatment. In the future, functional genomics and proteomics will be used to rapidly screen patients for subclinical characteristics that can predict disease course and response to therapy.

SUMMARY

A variety of biomarkers can be used to stratify patients with inflammatory bowel disease into more homogeneous subgroups with respect to response to therapy and disease progression.

Choosing Therapy on the Basis of Disease Classifications in Inflammatory Bowel Disease

Crohn's disease and ulcerative colitis (UC) are heterogeneous disorders, and as such, the response to therapy is likewise heterogeneous. Therefore, stratification of patients into distinct phenotypes and potentially genotypes will lead to more definitive answers with respect to evaluation of novel and established therapies.

Management of refractory inflammatory bowel disease

One of the most challenging aspects of the management of inflammatory bowel disease is the high frequency of incomplete or absent response to medical therapy. Although many patients may be truly refractory to medical therapy, a lack of response may indicate several possibilities, including incorrect diagnosis, progression of disease extent, intestinal complication, superinfection, underdosing of therapy, monotherapy instead of combination therapy, or medication intolerance. This article provides a practical general approach to refractory inflammatory bowel disease patients encountered in clinical practice.

Bacterial flagellin is a dominant antigen in Crohn disease

Chronic intestinal inflammation, as seen in inflammatory bowel disease (IBD), results from an aberrant and poorly understood mucosal immune response to the microbiota of the gastrointestinal tract in genetically susceptible individuals. Here we used serological expression cloning to identify commensal bacterial proteins that could contribute to the pathogenesis of IBD. The dominant antigens identified were flagellins, molecules known to activate innate immunity via Toll-like receptor 5 (TLR5), and critical targets of the acquired immune system in host defense. Multiple strains of colitic mice had elevated serum anti-flagellin IgG2a responses and Th1 T cell responses to flagellin. In addition, flagellin-specific CD4(+) T cells induced severe colitis when adoptively transferred into naive SCID mice. Serum IgG to these flagellins, but not to the dissimilar Salmonella muenchen flagellin, was elevated in patients with Crohn disease, but not in patients with ulcerative colitis or in controls. These results identify flagellins as a class of immunodominant antigens that stimulate pathogenic intestinal immune reactions in genetically diverse hosts and suggest new avenues for the diagnosis and antigen-directed therapy of patients with IBD.

Do serological markers and cytokines determine the indeterminate?

There is a general sense that indeterminate colitis (IC) runs an aggressive clinical course, is medically refractory, and is associated with higher pouch failure rates following restorative proctocolectomy. The question has been raised whether IC can be assigned to a diagnosis of Crohn's disease or ulcerative colitis through the characterization of immunogenetic similarities, or whether IC may represent a distinct subgroup within these heterogeneous disorders. In this article, the use of serologic markers, genetics, and immune responses to understand the pathogenesis of inflammatory bowel disease (IBD) and define clinically important subgroups of patients will be discussed. Then, how these scientific advances have been applied to the entity of IC will be reviewed. Importantly, a recent prospective study suggests that the absence of IBD-associated serologic markers defines the majority of IC as a separate entity within the spectrum of IBD. The development of serologic, genetic, and immune response markers will allow for rational description of clinically important subgroups, redefine natural history, and predict responses to therapy in IBD.

Antibiotics should be used as first-line therapy for Crohn's disease

The etiology of Crohn's disease remains uncertain, and to date no therapy is curative. Recent experimental evidence suggests that an altered immune response to commensal enteric flora in a genetically susceptible host plays a key role in both the development and perpetuation of the intestinal inflammation of Crohn's disease. Thus, incorporation of antibiotics into the therapeutic armamentarium for Crohn's disease, either as first-line therapy or combined with immunomodulatory drugs, would seem to be a rational strategy. Indeed, most IBD clinicians would attest to the marked benefit of antibiotic therapy in individual patients. Skepticism surrounding this approach arises because evidenced-based analyses' show that the few clinical trials evaluating the efficacy of antibiotics for Crohn's disease have produced equivocal or negative results or have methodological deficiencies, including small number of patients and absence of a placebo group. However, by undertaking an analysis that integrates information from both basic and clinical spheres of study, the dichotomy between experimental and clinical observations tends to merge. This approach underscores certain key factors that determine an optimal response to antibiotics, emphasizes the requirement for assessment in well-defined subsets of patients, and leads to the conclusion that antibiotics do provide benefit for Crohn's disease.

Anti-Saccharomyces cerevisiae antibodies (ASCA) in Crohn's disease are associated with disease severity but not NOD2/CARD15 mutations

Anti-Saccharomyces cerevisiae antibodies (ASCAs) have been proposed as serological markers, which may differentiate Crohn's disease (CD) from ulcerative colitis (UC) and predict disease phenotype. Their importance in pathogenesis is unproven. We investigated the relationship between ASCAs, disease phenotype and NOD2/CARD15 genotype in CD and whether ASCAs were related to antibodies to other fungal proteins. Serum from 228 patients [143 CD, 75 UC, 10 with indeterminate colitis (IC)] and 78 healthy controls (HC) were assayed for ASCA. Antibodies (IgA, IgG) to other fungal proteins (Fusarium species ATC20334, Mycoprotein) were measured in the same samples using an in-house enzyme-linked immunosorbent assay (ELISA) assay. ASCAs were present in 57% of CD, 19% of UC, 30% of IC and 8% of HCs. ASCA-positive status was a predictor for CD with sensitivity of 57%, specificity of 87%, positive predictive value of 78% and negative predictive value of 68%. ASCA was associated with proximal (gastroduodenal and small bowel involvement) rather than purely colonic disease (P < 0.001) and with a more severe disease phenotype and requirement for surgery over a median follow-up time of 9 years (P < 0.0001). No associations with NOD2/CARD15 mutations were seen. There was no association between ASCA and antibodies to MP (IgA or IgG). These data implicate ASCA as a specific marker of disease location and progression in CD, emphasizing the heterogeneity within IBD.

No significant association between mutations in exons 6 and 8 of the autoimmune regulator (AIRE) gene and inflammatory bowel disease

Various autoantibodies have been described in patients with inflammatory bowel disease. The autoimmune regulator (AIRE) functions as a transcription factor in cells responsible for the induction and maintenance of immunological tolerance. In contrast to classic autoimmune disorders, polymorphisms of the AIRE gene are not associated with inflammatory bowel disease, despite the presence of disease-specific autoantibodies.

Recent advances in the diagnosis and classification of inflammatory bowel disease

The availability of an increasing number of inflammatory bowel disease (IBD)-specific serologic antibodies, the discovery of disease-susceptibility genes, the introduction of pharmacogenetic markers, and the recent application of wireless capsule enteroscopy to the evaluation of patients with IBD are providing new types of information that must be integrated with more traditional IBD paradigms. The challenge facing researchers and clinicians is to determine how to incorporate these potentially clinically relevant insights into our understanding of disease pathogenesis and to define the spectrum of potential applications to the management of patients with IBD. The ultimate diagnostic and predictive value of these tests will likely be optimized when they are applied in combination, rather than individually. As the clinical relevance of this expanding diagnostic armamentarium is defined, it is hoped that these tests will enable clinicians not only to diagnose IBD accurately but also to determine disease patterns prospectively, suggest prognoses, and allow for individualization of therapeutic regimens.

IL-10 and its related cytokines for treatment of inflammatory bowel disease

Inflammatory bowel diseases (IBDs), including Crohn’s disease and ulcerative colitis are chronic inflammatory disorders of gastrointestinal tract. Although the etiology is incompletely understood, initiation and aggravation of the inflammatory process seem to be due to a massive local mucosal immune response. Interleukin-10 (IL-10) is a regulatory cytokine which inhibits both antigen presentation and subsequent pro-inflammatory cytokine release, and it is proposed as a potent anti-inflammatory biological therapy in chronic IBD. Many methods of IL-10 as a treatment for IBD have been published. The new strategies of IL-10 treatment, including recombinant IL-10, the use of genetically modified bacteria, gelatine microsphere containing IL-10, adenoviral vectors encoding IL-10 and combining regulatory T cells are discussed in this review. The advantages and disadvantages of these IL-10 therapies are summarized. Although most results of recombinant IL-10 therapies are disappointing in clinical testing because of lacking efficacy or side effects, therapeutic strategies utilizing gene therapy may enhance mucosal delivery and increase therapeutic response. Novel IL-10-related cytokines, including IL-19, IL-20, IL-22, IL-24, IL-26, IL-28 and IL-29, are involved in regulation of inflammatory and immune responses. The use of IL-10 and IL-10-related cytokines will provide new insights into cell-based and gene-based treatment against IBD in near future.

Epithelia under metabolic stress perceive commensal bacteria as a threat

The normal gut flora has been implicated in the pathophysiology of inflammatory bowel disease and there is increased interest in the role that stress can play in gut disease. The chemical stressor dinitrophenol (DNP, uncouples oxidative phosphorylation) was injected into the ileum of laparotomized rats and mitochondria structure, epithelial permeability, and inflammatory cell infiltrate were examined 6 and 24 hours later. Monolayers of human colonic epithelial cells (T84, HT-29) were treated with DNP +/- commensal Escherichia coli, followed by assessment of epithelial permeability, bacterial translocation, and chemokine (ie, interleukin-8) synthesis. Delivery of DNP into rat distal ileum resulted in disruption of epithelial mitochondria; similar changes were noted in mildly inflamed ileal resections from patients with Crohn's disease. Also, DNP-treated ileum displayed increased gut permeability and immune cell recruitment. Subsequent studies revealed deceased barrier function, increased bacterial translocation, increased production of interleukin-8, and enhanced mobilization of the transcription factor AP-1 in the model epithelial cell lines exposed to commensal bacteria (E. coli strains HB101 or C25), but only when the monolayers were pretreated with DNP (0.1 mmol/L). These data suggest that enteric epithelia under metabolic stress perceive a normally innocuous bacterium as threatening, resulting in loss of barrier function, increased penetration of bacteria into the mucosa, and increased chemokine synthesis. Such responses could precipitate an inflammatory episode and contribute to existing enteric inflammatory disorders.

Association of antibody responses to microbial antigens and complications of small bowel Crohn's disease

BACKGROUND & AIMS

Crohn's disease patients can be characterized by antibody responses against Crohn's disease-related bacterial sequence, Escherichia coli outer membrane porin C, Saccharomyces cerevisiae (oligomannan), and neutrophil nuclear antigens. Our aim was to determine whether expression of antibodies against Crohn's disease-related bacterial sequence and Escherichia coli outer membrane porin C is associated with distinct phenotypic manifestations.

METHODS

Sera from 303 patients were tested for antibodies to the Crohn's disease-related bacterial sequence (I2), anti-Escherichia coli outer membrane porin C, anti-Saccharomyces cerevisiae, and perinuclear antineutrophil cytoplasmic antibodies and for 3 Crohn's disease-associated variants of the NOD2 gene (R702W, G908R, and 1007fs) and compared with clinical data.

RESULTS

Patients expressing I2 were more likely to have fibrostenosing Crohn's disease (64.4% vs. 40.7%; P < 0.001) and to require small bowel surgery (62.2% vs. 37.4%; P < 0.001). Patients with anti-Escherichia coli outer membrane porin C were more likely to have internal perforating disease (50.0% vs. 30.7%; P = 0.001) and to require small bowel surgery (61.4% vs. 44.2%; P = 0.003). Anti-Crohn's disease-related bacterial sequence was independently associated with fibrostenosis (P = 0.027) and small bowel surgery (P = 0.01), whereas anti-Escherichia coli outer membrane porin C was independently associated with internal perforations (P < 0.006). Patients positive for I2, anti-Escherichia coli outer membrane porin C, and anti-Saccharomyces cerevisiae were the most likely to have undergone small bowel surgery (72.0%; odds ratio, 8.6; P < 0.001) compared with patients without reactivity (23.0%). When the presence and magnitude of antibody responses were considered, 90% of patients with small bowel disease who required surgery had high levels of I2, Escherichia coli outer membrane porin C, and oligomannan antibodies, compared with only 18.2% with low-titer responses (P < 0.001).

CONCLUSIONS

I2 and anti-Escherichia coli outer membrane porin C are associated with Crohn's disease phenotypes, and patients with the highest level of serum reactivity toward an increasing number of microbiota have the greatest frequency of strictures, internal perforations, and small bowel surgery.

Utility of serum antibodies in determining clinical course in pediatric Crohn's disease

BACKGROUND AND AIMS

The utility of serial measurements of anti-Saccharomyces cerevisiae (ASCA) and perinuclear antineutrophil cytoplasmic (p-ANCA) antibodies in Crohn's disease (CD) evolution is unknown. We aimed to study the pattern of antibody change and the prognosis of selected outcomes by baseline (at time of diagnosis) and serial antibody measurements in pediatric CD patients.

METHODS

Serum ASCA and p-ANCA antibodies were measured at baseline (n = 154) and repeated during follow-up (n = 61) using standard techniques in a cohort of patients identified at Hôpital Sainte-Justine between 1996 and 1998. Clinical information was abstracted from medical charts. Antibody patterns were examined using mixed modeling techniques. The prognostic ability of antibodies for selected outcomes was evaluated using logistic regression.

RESULTS

Fifteen (24.5%), 18 (29.5%), and 11 (18%) patients with serial antibody measurements changed their ASCA-IgA, ASCA-IgG, and p-ANCA status (positivity), respectively. No distinct patterns in the evolution of antibody titers were noted. Baseline ASCA-IgA positivity significantly predicted relapses during disease course (IgA: odds ratio [OR], 2.9; 95% confidence interval [CI], 1.33-6.35). Serial antibody measurements did not predict the occurrence of clinical outcomes.

CONCLUSIONS

Baseline serum antibodies were predictive of a more relapsing disease course in pediatric CD. However, the limited variability in the antibodies over time and the inability of serial measurements to predict clinical outcomes may limit their use in the establishment of intervention strategies.

Colonic bacterial superantigens evoke an inflammatory response and exaggerate disease in mice recovering from colitis

BACKGROUND & AIMS

There is renewed interest in commensal bacteria as triggers of idiopathic disease, a concept that is prominent in inflammatory bowel disease (IBD). Here the effect of intracolonic instillation of Staphylococcus aureus enterotoxin B (SEB), a model superantigen (SAgs: potent T-cell stimuli), into mice was examined.

METHODS

Mice (Balb/c, severe combined immunodeficient [SCID], V beta 8(+) ovalbumin transgenic [OVA-Tg], interleukin 10 [IL-10] knockout [KO]) received a single intrarectal (IR) dose of SAg and colonic form (histology, myeloperoxidase [MPO] activity) and function (ion transport) were assessed 12-72 hours later. In subsequent studies the potential for SEB to reactivate disease in mice recovering from dextran sodium sulfate (DSS)-induced colitis (5 days at 4% [wt/vol] followed by 14 days normal water) was examined.

RESULTS

SEB-treated Balb/c mice displayed a time- and dose-dependent colonic inflammation (increased MPO, histologic damage score, and macrophage number). Similar events occurred in response to other SAgs, namely S. aureus enterotoxin A (SEA) and Yersinia pseudotuberculosis mitogen. Ion transport, the driving force for water movement, was unaffected by SEB treatment. SCID mice developed no inflammation after IR SEB delivery, whereas OVA Tg mice displayed enhanced responsiveness. Although SEB treatment of IL-10 KO mice did elicit a response, the inflammation was transitory and did not hasten the spontaneous colitis seen in these mice. Finally, mice recovering from DSS-induced colitis showed a worsening of the disease when challenged with SEB; IR SEB evoked significant increases in MPO, macrophage infiltration, T-cell activation (i.e., CD25 expression), and perturbed epithelial ion transport.

CONCLUSIONS

Lumen-derived bacterial SAgs can elicit a local inflammation and aggravate enteric inflammatory disorders in which they were not the causative agent.

Infliximab in the treatment of medically refractory indeterminate colitis

AIM

To examine the outcome of infliximab intervention in refractory indeterminate colitis.

METHODS

Twenty patients with severe, medically refractory indeterminate colitis were treated with infliximab. All patients initially received infliximab, 5 mg/kg, intravenously and, in some patients, the dose was subsequently increased to 10 mg/kg. The number of infusions ranged from one to 16 per patient. Indeterminate colitis was defined as colitis that could not be classified with certainty as Crohn's disease or ulcerative colitis based on traditional clinical, endoscopic and histopathological criteria. The clinical response to infliximab was classified as complete response, partial response or non-response.

RESULTS

Fourteen of the 20 patients (70%) showed a complete response to infliximab treatment, two showed a partial response and four showed no response. The four non-responders underwent colectomy with ileal pouch-anal anastomosis. The resected colon specimen was consistent with ulcerative colitis in all four cases, although two were subsequently re-classified as Crohn's disease. Eight additional patients were subsequently re-classified as having Crohn's disease on longer follow-up evaluation, whilst eight continued to have features of indeterminate colitis. The response rate to infliximab treatment was similar in both groups.

CONCLUSIONS

Infliximab is effective in approximately two-thirds of patients with indeterminate colitis, and thus may be considered for patients with refractory disease prior to colectomy. The follow-up time afforded by infliximab treatment may allow for more accurate classification of the disease in a significant proportion of patients whose colitis has indeterminate features at initial presentation.

Advances in clinical laboratory tests for inflammatory bowel disease

Inflammatory bowel disease (IBD) is a generic term that refers to Crohn's disease and chronic ulcerative colitis (UC). The CD and UC are considered to be distinct forms of IBD; but there is a subgroup of CD with a UC-like presentation. The genetic factors play a significant role in IBD. IBD is associated with a strong familial pattern. Recent studies support the hypothesis that IBD patients have a dysregulated immune response to endogenous bacteria in the gastrointestinal tract. The serologic responses seen in Crohn's disease include antibodies to Saccharomyces cerevisiae, mycobacteria, bacteroides and E. coli. The pANCA antibody seen in UC and CD has been demonstrated to react with epitopes of H1 histone, Bacteroides caccae (Ton-B linked outer membrane protein), Pseudomonas fluorescens-associated bacterial protein I-2, mycobacterial histone 1 homologue called Hup B. In recent years, several serologic markers have been found to be useful for the diagnosis and differentiation of CD and UC. These markers include the following antibodies: (a) pANCA, (b) ASCA, (c) anti-pancreatic antibody, (d) OmpC antibody and (e) I-2 antibody and antibodies to anaerobic coccoid rods. The application of a panel of markers with the use of an algorithm (i.e. IBD First Step) can identify specific subtypes of IBD that have different clinical courses and progression of the diseases. The serologic markers are useful for the diagnosis and management of CD and UC patients.

Ethanol-induced colitis prevents oral tolerance induction in mice

The gut mucosa is a major site of contact with antigens from food and microbiota. Usually, these daily contacts with natural antigens do not result in inflammatory reactions; instead they result in a state of systemic hyporesponsiveness named oral tolerance. Inflammatory bowel diseases (IBD) are associated with the breakdown of the immunoregulatory mechanisms that maintain oral tolerance. Several animal models of IBD/colitis are available. In mice, these include targeted disruptions of the genes encoding cytokines, T cell subsets or signaling proteins. Colitis can also be induced by intrarectal administration of chemical substances such as 2,4,6-trinitrobenzene sulfonic acid in 50% ethanol. We report here a novel model of colitis induced by intrarectal administration of 50% ethanol alone. Ethanol-treated mice develop an inflammatory reaction in the colon characterized by an intense inflammatory infiltrate in the mucosa and submucosa of the large intestine. They also present up-regulation of both interferon gamma (IFN-gamma) and interleukin-4 (IL-4) production by cecal lymph node and splenic cells. These results suggest a mixed type of inflammation as the substrate of the colitis. Interestingly, cells from mesenteric lymph nodes of ethanol-treated mice present an increase in IFN-gamma production and a decrease in IL-4 production indicating that the cytokine balance is altered throughout the gut mucosa. Moreover, induction of oral tolerance to ovalbumin is abolished in these animals, strongly suggesting that ethanol-induced colitis interferes with immunoregulatory mechanisms in the intestinal mucosa. This novel model of colitis resembles human IBD. It is easy to reproduce and may help us to understand the mechanisms involved in IBD pathogenesis.

Targeting enteric bacteria in treatment of inflammatory bowel diseases: why, how, and when

PURPOSE

This review discusses the role of bacterial adjuvants and antigens in induction and reactivation of chronic intestinal inflammation in susceptible hosts; discusses the results of recent therapeutic trials of antibiotics, probiotics, and prebiotics; and suggests future treatment strategies.

RECENT FINDINGS

Bacterial adjuvants, including peptidoglycan, lipopolysaccharide, and DNA (CpG) bind to membrane-bound toll-like receptors (TLR-2, 4, and 9. respectively) or cytoplasmic (NOD1 and NOD2) receptors (pattern recognition receptors) that activate nuclear factor-kappaB and transcription of many proinflammatory cytokines and adhesion, costimulatory, and major histocompatibility complex class II molecules. Experimental enterocolitis does not occur in a sterile (germ-free) environment and is prevented and treated by broad-spectrum antibiotics. Individual nonpathogenic intestinal bacterial species selectively induce experimental colitis, with host specificity. Crohn disease and ulcerative colitis patients exhibit pathogenic immune responses (loss of immunologic tolerance) to multiple normal enteric bacterial species and serologic responses to Mycobacterium paratuberculosis. Metronidazole and ciprofloxacin selectively treat colonic Crohn disease, but not ulcerative colitis or ileal Crohn disease, and may prevent recurrence of postoperative Crohn disease. Certain probiotic species decrease relapse of ulcerative colitis and chronic pouchitis and delay onset of pouchitis.

SUMMARY

Normal, nonpathogenic enteric bacteria induce and perpetuate chronic intestinal inflammation in genetically susceptible hosts with defective immunoregulation, bacterial clearance, or mucosal barrier function. Altering the composition and decreasing mucosal adherence/invasion of commensal bacteria with antibiotics, probiotics, and prebiotics can potentially prevent and treat Crohn disease, pouchitis, and possibly ulcerative colitis, but optimal treatments have not yet been identified.

Crohn's disease: a defensin deficiency syndrome?

This comprehensive review promotes the novel concept that a defensin deficiency, i.e. lack of mucosal peptide antibiotics, may play a pivotal role in the aetiopathogenesis of Crohn's disease. Such an impaired function of this chemical barrier is consistent with the epidemiological relationship of good domestic hygiene with the incidence of inflammatory bowel diseases. The disregulated adaptive immune system, formerly believed to be the major cause in the development of Crohn's disease, may reflect only the primary break of the mucosal defence since the immune response is mostly directed against lumenal bacteria. Recent work has identified five different defensins expressed in colonic mucosa. In contrast to ulcerative colitis, Crohn's disease is characterised by an impaired induction of human beta defensins 2 and 3. This deficient induction may be due to changes in the intracellular transcription by NFkappaB and the intracellular peptidoglycan receptor NOD2, mutated in Crohn's disease. These findings are consistent with the mucosal attachment of lumenal bacteria in inflammatory bowel diseases and the frequent occurrence of other infectious agents. The hypothesis of an impaired mucosal antibacterial activity is also consistent with the benefit from antibiotic or probiotic treatment in certain inflammatory bowel disease states.