Genetic deletion of the bacterial sensor NOD2 improves murine Crohn's disease-like ileitis independent of functional dysbiosis.

Although genetic polymorphisms in NOD2 (nucleotide-binding oligomerization domain-containing 2) have been associated with the pathogenesis of Crohn's disease (CD), little is known regarding the role of wild-type (WT) NOD2 in the gut. To date, most murine studies addressing the role of WT Nod2 have been conducted using healthy (ileitis/colitis-free) mouse strains. Here, we evaluated the effects of Nod2 deletion in a murine model of spontaneous ileitis, i.e., the SAMP1Yit/Fc (SAMP) strain, which closely resembles CD. Remarkably, Nod2 deletion improved both chronic cobblestone ileitis (by 50% assessed, as the % of abnormal mucosa at 24 wks of age), as well as acute dextran sodium sulfate (DSS) colitis. Mechanistically, Th2 cytokine production and Th2-transcription factor activation (i.e., STAT6 phosphorylation) were reduced. Microbiologically, the effects of Nod2 deletion appeared independent of fecal microbiota composition and function, assessed by 16S rRNA and metatranscriptomics. Our findings indicate that pharmacological blockade of NOD2 signaling in humans could improve health in Th2-driven chronic intestinal inflammation.

KLF6 contributes to myeloid cell plasticity in the pathogenesis of intestinal inflammation.

Inflammatory bowel disease (IBD) is associated with dysregulated macrophage responses, such that quiescent macrophages acquire a pro-inflammatory activation state and contribute to chronic intestinal inflammation. The transcriptional events governing macrophage activation and gene expression in the context of chronic inflammation such as IBD remain incompletely understood. Here, we identify Kruppel-like transcription factor-6 (KLF6) as a critical regulator of pathogenic myeloid cell activation in human and experimental IBD. We found that KLF6 was significantly upregulated in myeloid cells and intestinal tissue from IBD patients and experimental models of IBD, particularly in actively inflamed regions of the colon. Using complementary gain- and loss-of-function studies, we observed that KLF6 promotes pro-inflammatory gene expression through enhancement of nuclear factor κB (NFκB) signaling, while simultaneously suppressing anti-inflammatory gene expression through repression of signal transducer and activator of transcription 3 (STAT3) signaling. To study the in vivo role of myeloid KLF6, we treated myeloid-specific KLF6-knockout mice (Mac-KLF6-KO) with dextran sulfate sodium (DSS) and found that Mac-KLF6-KO mice were protected against chemically-induced colitis; this highlights the central role of myeloid KLF6 in promoting intestinal inflammation. Collectively, our results point to a novel gene regulatory program underlying pathogenic, pro-inflammatory macrophage activation in the setting of chronic intestinal inflammation.

Targeting leukocyte trafficking for the treatment of inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a chronic immune-mediated inflammatory disease of the intestine that includes both Crohn's disease and ulcerative colitis, and afflicts nearly 1 million people throughout North America. As our understanding of IBD pathogenesis grows, several new therapies have been developed that use monoclonal antibodies to specifically target key mediators and biological pathways implicated in IBD immune dysfunction. One important pathway involves leukocyte trafficking and infiltration into the affected intestinal tissues. This review provides a summary of the different therapies that have been developed to inhibit leukocyte trafficking to the inflamed gut, and evaluates the relative safety and efficacy of these novel drugs within the context of existing medical therapies for IBD.

Tregs are dysfunctional in vivo in a spontaneous murine model of Crohn's disease.

Although regulatory T cells (Tregs) have been implicated in inflammatory bowel disease, Tregs from Crohn's disease (CD) patients are increased in number and function normally in vitro. To clarify this disparity, we studied Treg function in vivo using a spontaneous model of CD-like ileitis. We first administered anti-CD25-depleting antibodies to SAMP1/YitFc (SAMP) mice to assess ileitis; mesenteric lymph node cells were then transferred into SCID (severe combined immunodeficient) recipients to induce colitis. CD25 depletion increased the severity of both spontaneous ileitis and adoptively transferred colitis. Interestingly, a second transfer of CD4(+)CD25(+) cells from untreated AKR control mice was able to ameliorate the induced colitis, whereas CD4(+)CD25(+) cells from untreated SAMP mice were not, suggesting a functional abnormality in SAMP Tregs. Anti-CD25 treatment in SAMP mice also induced proliferation of CD25(-)Foxp3(+) Tregs, which had a proinflammatory intestinal T helper type 1/ T helper type 2 (Th1/Th2) effector phenotype. These studies demonstrate Treg dysfunction in a spontaneous model of CD-like ileitis.

Role of interleukin 6 in a murine model of Crohn's ileitis: are cytokine/anticytokine strategies the future for IBD therapies?

Although the precise causes of inflammatory bowel disease (IBD) have yet to be discovered, important therapeutic advances have resulted from the manipulation of cytokine function(s) using anticytokine/cytokine therapies, such as targeting of tumor necrosis factor. We discuss the future of this area of investigation in the context of preclinical experimentation using animal models of IBD. In particular, we pinpoint the roles played by interleukin 6 and its intracellular signalling pathways in the SAMP1/Yit murine model of Crohn's-like ileitis.

Probiotics in experimental and human inflammatory bowel disease: discussion points.

In recent years, novel insights have been made into the role of bacterial microflora in health and disease. Commensal flora manipulation by probiotic bacteria has been investigated in human and experimental inflammatory bowel disease (IBD). In particular, animal models of IBD offer the opportunity to address important issues regarding indication, therapeutic efficacy and mechanism of action of the probiotic bacteria. Despite the appealing results of many published studies, fundamental questions still remain unanswered. Further studies on appropriate animal models are needed in order to better clarify our knowledge about probiotic bacteria and their potential application as a valid therapeutic option in IBD patients.

A randomized, double-blind, placebo-controlled trial of CDP571, a humanized monoclonal antibody to tumour necrosis factor-alpha, in patients with corticosteroid-dependent Crohn's disease.

AIM: To evaluate CDP571, a humanized monoclonal antibody to tumour necrosis factor-alpha, for the treatment of corticosteroid-dependent Crohn's disease. METHODS: Patients with corticosteroid-dependent Crohn's disease (use of prednisolone 15-40 mg/day or budesonide 9 mg/day for at least 8 weeks, a previous failed attempt to discontinue corticosteroids within 8 weeks, and Crohn's Disease Activity Index score 150 points or less) were enrolled in a 16-week, randomized, double-blind, placebo-controlled trial. The patients received intravenous CDP571 (20 mg/kg at week 0 and 10 mg/kg at week 8) or placebo. Corticosteroid therapy was decreased following a predefined schedule. The primary efficacy end-point was the percentage of patients with corticosteroid-sparing [i.e. no disease flare (Crohn's Disease Activity Index score > or =220 points) and no longer requiring corticosteroid therapy] at week 10. The major secondary efficacy end-point was corticosteroid-sparing at week 16. RESULTS: Seventy-one patients received treatment. Corticosteroid-sparing was achieved by 19 of 39 (48.7%) CDP571 patients and 13 of 42 (40.6%) placebo patients (P = 0.452) at week 10, and by 18 of 39 (46.2%) CDP571 patients and seven of 32 (21.9%) placebo patients (P = 0.032) at week 16. CDP571 therapy was well-tolerated and the incidence of serious adverse events was similar to placebo. CONCLUSIONS: The CDP571 was effective for corticosteroid-sparing at week 16 but not week 10, and was well-tolerated in patients with corticosteroid-dependent Crohn's disease.

Antibody blockade of ICAM-1 and VCAM-1 ameliorates inflammation in the SAMP-1/Yit adoptive transfer model of Crohn's disease in mice.

BACKGROUND & AIMS: Integrins (alpha(4) and beta(2)) and their endothelial ligands vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) play key roles in leukocyte recruitment to areas of inflammation. ICAM-1 and VCAM-1 are expressed in inflamed intestinal tissues. This study investigates a possible causative role of adhesion molecules ICAM-1, VCAM-1, and alpha(4) integrins in mediating the inflammatory response in a murine model of Crohn's disease (CD). METHODS: CD4+ mesenteric lymph node cells from SAMP-1/Yit donor mice were adoptively transferred into major histocompatibility complex-matched severe combined immunodeficiency disease mice. Six weeks later, these mice were left untreated or treated for 3 days with monoclonal antibodies (mAbs) to ICAM-1, VCAM-1, or both, and alpha(4), or both ICAM-1 and alpha(4), dexamethasone, or nonblocking isotype control antibodies. On day 4 after treatment, tissues were investigated for expression of ICAM-1, VCAM-1, and for severity of inflammation using a semiquantitative inflammatory score. Dexamethasone treatment resolved all measures of intestinal inflammation. RESULTS: Blocking either ICAM-1, VCAM-1, or alpha(4) integrins had no significant beneficial effect. However, blocking ICAM-1 and alpha(4), or blocking ICAM-1 and VCAM-1, showed a 70% resolution of the active inflammation, but not chronic inflammation. CONCLUSIONS: These findings suggest that blocking ICAM-1 and VCAM-1 may have therapeutic benefit for the acute inflammatory component of Crohn's disease.

A 'minimal' approach in design of flavivirus infectious DNA.

The 'infectious DNA' approach, which is based on in vivo transcription of (+)RNA virus genome cDNA cassettes from eukaryotic promoters in transfected cells, became a popular alternative to the classical scheme in the infectious clone methodology. Its use, however, is often limited by the instability of plasmids due to a transcriptional activity of eukaryotic promoters in Escherichia coli resulting in synthesis of products toxic for the bacterial host. Using a highly unstable representative infectious clone of Japanese encephalitis (JE) flavivirus, we tested a new approach in design of such problematic 'infectious DNA' constructs, which is based on minimizing unwanted transcription in the bacterial host. A plasmid containing full genome size JE cDNA under control of the minimal cytomegalovirus (CMV) promoter can be propagated in E. coli with growth and stability characteristics similar to that of constructs controlled by the T7 promoter. Transfection of this plasmid into susceptible cells leads to the establishment of a productive infectious cycle. Reinsertion of the CMV enhancer at the 3'-end of the JE cassette substantially increased the specific infectivity without affecting the stability and growth characteristics of the construct. This approach can be useful when stabilization of infectious clones by modification of a viral cDNA cassette is not the feasible or suitable alternative.

The incidence of lymphoid and myeloid malignancies among hospitalized Crohn's disease patients.

An association may exist between Crohn's disease (CD) and lymphoid/myeloid malignancies. We aimed to evaluate the 2-year cumulative incidence rate of lymphoid/myeloid malignancy among hospitalized CD patients. This is a retrospective cohort study using hospital discharge data from California and Virginia. Cohorts were defined by the presence or absence of a CD diagnosis in all patients discharged during a single calendar year (Year-2). The presence or absence of lymphoid/myeloid malignancy was determined for all hospitalizations during a 4-year period (Year-1 to Year-4) for each member of both cohorts. To obtain a 2-year cumulative incidence rate, patients with lymphoid/myeloid malignancy prior to or at the time of their first admission in Year-2 were excluded. Patients were followed for 8 quarters after this admission for the incidence of lymphoid/myeloid malignancy. Cumulative incidence rates and odds ratios were calculated. The crude 2-year incidence rate of lymphoid/myeloid malignancy among hospitalized CD patients was 3.87/1.000 CD patients (21/5,426; 95% CI = 2.40-5.92). The odds ratio adjusted for age, gender, and race was 2.04 (95% CI = 1.33-3.14, p < 0.001). The 2-year cumulative incidence of lymphoid/myeloid malignancies among hospitalized CD patients is greater than that seen in hospitalized patients without CD. This finding supports the need for further prospective population-based studies.

Cost-utility of initial medical management for Crohn's disease perianal fistulae.

BACKGROUND & AIMS: The cost-utility of infliximab is unknown. The aim of this study was to determine the incremental cost-utility (CU(inc)) of medical therapy for Crohn's disease (CD) perianal fistula. METHODS: A Markov model was used to simulate a 1-year treatment period with the following: 6-mercaptopurine and metronidazole [6MP/met] (comparator), 3 infliximab infusions + 6MP/met as second-line therapy (intervention I), infliximab with episodic reinfusion (intervention II), and 6MP/met + infliximab as second-line therapy (intervention III). Utilities were elicited from patients with CD and healthy individuals by standard gamble, and costs were obtained from hospital billing data. Uncertainty was assessed by sensitivity analysis. RESULTS: All strategies had similar effectiveness. Interventions I, II, and III were slightly more effective, but also more costly than 6MP/met (Intervention I: CU(inc) = $355,450/quality-adjusted life-years [QALY]; Intervention II: CU(inc) = $360,900/QALY; Intervention III: CU(inc) = $377,000/QALY). If the cost of infliximab were reduced to $304 per infusion, the CU(inc) for intervention II would be $54,050/QALY. CONCLUSIONS: Based on available data, all strategies had similar effectiveness in our model, but infliximab was much more expensive than 6MP/met. The incremental benefit of infliximab for treating CD perianal fistulae over a 1-year period may not justify the higher cost. Prospective studies directly comparing 6MP/met and infliximab are warranted.

Th1-type responses mediate spontaneous ileitis in a novel murine model of Crohn's disease.

We describe here the immunologic characterization of a new mouse strain, SAMP1/Yit, which spontaneously develops a chronic intestinal inflammation localized to the terminal ileum. The resulting ileitis bears a remarkable resemblance to human Crohn's disease. This strain of mice develops discontinuous, transmural inflammatory lesions in the terminal ileum with 100% penetrance by 30 weeks of age. The intestinal inflammation is characterized by massive infiltration of activated CD4+ and CD8alpha(+)TCRalphabeta(+) T cells into the lamina propria and is accompanied by a dramatic decrease in the intraepithelial lymphocyte CD8alpha(+)TCRgammadelta(+)/CD8alpha(+)TCRalphabeta(+) ratio. The results of adoptive transfer experiments strongly suggest that CD4+ T cells that produce a Th1-like profile of cytokines, e.g., IFN-gamma and TNF, mediate the intestinal inflammation found in SAMP1/Yit mice. In addition, pretreatment of adoptive transfer recipients with a neutralizing anti-TNF antibody prevents the development of intestinal inflammation, suggesting that TNF plays an important role in the pathogenesis of intestinal inflammation in this model. To our knowledge, these data provide the first direct evidence that Th1-producing T cells mediate intestinal inflammation in a spontaneous animal model of human Crohn's disease.

A new strategy in design of +RNA virus infectious clones enabling their stable propagation in E. coli.

Infectious clone methodology is a valuable tool of modern experimental virology. However, its use is often constrained by the instability of infectious clone constructs during propagation in E. coli. To circumvent this problem, we have devised a strategy that could be suitable for design of +RNA virus molecular clones in general. An infectious clone is assembled as "infectious DNA," and expression of problem regions present in the viral cDNA is prevented during propagation in E. coli by insertion of short introns. To demonstrate the feasibility of this approach, a highly unstable Japanese encephalitis flavivirus infectious clone has been successfully converted into a remarkably stable infectious DNA construct with the specific infectivity of 10(6) pfu/microg in cell culture. The proposed strategy may be useful in the design of self-amplifying gene therapy vectors and development of new immunization methodologies, and could facilitate creation of molecular repositories of existing viral vaccines.

Lessons from genetically engineered animal models XI. Novel mouse models to study pathogenic mechanisms of Crohn's disease.

Crohn's Disease (CD) affects more than 500,000 individuals in the United States and represents the second most common chronic inflammatory disorder after rheumatoid arthritis. Although major advances have been made in defining the basic mechanisms underlying chronic intestinal inflammation, the precise etiopathogenesis of CD remains unknown. We have recently characterized two novel mouse models of enteritis that express a CD-like phenotype, namely the TNF DeltaARE model of tumor necrosis factor (TNF) overexpression and the SAMP1/Yit model of spontaneous ileitis. The unique feature of these models is that they closely resemble CD for location and histopathology. These genetically manipulated new models of intestinal inflammation offer a powerful tool to investigate potential causes of human disease and may allow the development of novel disease-modifying therapeutic modalities for the treatment of CD.

Discovering the cause of inflammatory bowel disease: lessons from animal models.

The precise cause of inflammatory bowel disease remains unclear. Relevant animal models are important tools for studying the underlying mechanisms of inflammation and disease pathogenesis. The purpose of this review is to summarize the various types of animal models available for use in inflammatory bowel disease research and to illustrate how these models have contributed to a better understanding of the etiopathogenesis of inflammatory bowel disease, particularly focusing on papers published during calendar year 1999. Studies using appropriate animal models have provided important discoveries in this field of investigation. These include determination of the key role that pathogenic and regulatory T cells, proinflammatory and immunoregulatory cytokines, indigenous bacterial flora, and putative predisposing genes play in the disease process. The availability of new animal models that closely resemble the human disease is expected to allow further characterization of the initiating event(s) in inflammatory bowel disease and lead to a possible cure for this devastating disease.

The relationship between infliximab treatment and lymphoma in Crohn's disease.

The relationship between chronic inflammatory conditions and malignancy is complex. We describe the clinical course of 2 patients with Crohn's disease (CD) in whom lymphoma was diagnosed after treatment with infliximab. The first patient was a 61-year-old man with a 30-year history of fistulizing CD in whom B-cell non-Hodgkin's lymphoma was diagnosed 9 months after treatment with infliximab. The second is a 29-year-old man with CD in whom nodular sclerosing Hodgkin's lymphoma was diagnosed 3 weeks after infusion with infliximab. The lymphoma presented with pleural effusions, mediastinal and cervical adenopathy, and no gastrointestinal lesion. We describe the implications of these cases for the use of immunomodulatory therapy in CD and the questionable association between CD and lymphoma.

Functional and ethnic association of allele 2 of the interleukin-1 receptor antagonist gene in ulcerative colitis.

BACKGROUND & AIMS: The role of the interleukin (IL)-1 receptor antagonist (IL-1ra) in predisposing an individual to inflammatory bowel disease (IBD) is controversial. This study aimed to determine the association between intron 2 IL-1ra polymorphism and IBD by performing a multiethnic case-control study and to assess its functional significance. METHODS: A total of 236 patients with ulcerative colitis (UC), 196 patients with Crohn's disease (CD), and 338 ethnically matched control patients treated at LAC-USC and Cedars-Sinai Medical Centers and the University of Milan Medical Center were genotyped for a variable length polymorphism in intron 2 of the IL-1ra gene (IL-1RN). Total IL-1ra protein production rates in peripheral blood mononuclear cells (PBMCs) were correlated with carriage of allele 2 of the IL-1RN gene (IL-1RN*2). RESULTS: In the LAC-USC group, UC patients (n = 60) had an increased frequency of at least 1 copy of IL-1RN*2 compared with controls (n = 129) (70% vs. 33%; P < 0.01; odds ratio [OR], 4.7). The frequency of IL-1RN*2 carriage in the Cedars-Sinai group was 59% in UC, 45% in CD, and 42% in controls (P < 0.01; OR, 2.0). A significant difference was observed only in the Jewish subgroup (P = 0.003; OR, 5.0). The association was not detected in UC or CD patients treated at the University of Milan. The ORs of 4.7 and 5.0 appear to be the highest reported in any UC population for any genetic markers. Further, carriage of IL-1RN*2 was associated with decreased production of total IL-1ra protein in cultured PBMCs from both UC patients and controls. CONCLUSIONS: These results provide further evidence that IL-1ra is important in the predisposition to UC, there may be genetic or pathogenetic heterogeneity between different ethnic groups, and UC and CD are genetically distinct diseases.

IL-18, a novel immunoregulatory cytokine, is up-regulated in Crohn's disease: expression and localization in intestinal mucosal cells.

IL-18, a novel immunoregulatory cytokine with potent IFN-gamma-inducing activities, may play an important role in Th1-mediated chronic inflammatory disorders. The aim of the present study was to characterize the expression and localization of IL-18 in colonic specimens and isolated mucosal cell populations from patients with Crohn's disease (CD), a prototypic Th1-mediated disorder. Using a semiquantitative RT-PCR protocol, IL-18 mRNA transcripts were found to be increased in freshly isolated intestinal epithelial cells (IEC) and lamina propria mononuclear cells (LPMC) from CD compared with ulcerative colitis (UC) and noninflamed control (cont) patients, and were more abundant in IEC compared with LPMC. Immunohistochemical analysis of surgically resected colonic tissues localized IL-18 to both LPMC (specifically, macrophages and dendritic cells) as well as IEC. Staining was more intense in CD compared with UC and cont, and in involved (inv) vs noninvolved (n inv) areas. Western blot analysis revealed that an 18. 3-kDa band, consistent with both recombinant and mature human IL-18 protein, was found predominantly in CD vs UC intestinal mucosal biopsies; a second band of 24 kDa, consistent with the inactive IL-18 precursor, was detected in n inv areas from both CD and UC biopsies and was the sole form found in noninflamed cont. To our knowledge, this report is the first describing increased expression of IL-18 in a human Th1-mediated chronic inflammatory disease. In addition, our studies further support the concept that IEC and dendritic cells may possess important immunoregulatory functions in both normal, as well as pathological, mucosal immunity.