A functional genomics predictive network model identifies regulators of inflammatory bowel disease.

A major challenge in inflammatory bowel disease (IBD) is the integration of diverse IBD data sets to construct predictive models of IBD. We present a predictive model of the immune component of IBD that informs causal relationships among loci previously linked to IBD through genome-wide association studies (GWAS) using functional and regulatory annotations that relate to the cells, tissues, and pathophysiology of IBD. Our model consists of individual networks constructed using molecular data generated from intestinal samples isolated from three populations of patients with IBD at different stages of disease. We performed key driver analysis to identify genes predicted to modulate network regulatory states associated with IBD, prioritizing and prospectively validating 12 of the top key drivers experimentally. This validated key driver set not only introduces new regulators of processes central to IBD but also provides the integrated circuits of genetic, molecular, and clinical traits that can be directly queried to interrogate and refine the regulatory framework defining IBD.

Enteroendocrine cells express functional Toll-like receptors.

Intestinal epithelial cells (IECs) provide a physical and immunological barrier against enteric microbial flora. Toll-like receptors (TLRs), through interactions with conserved microbial patterns, activate inflammatory gene expression in cells of the innate immune system. Previous studies of the expression and function of TLRs in IECs have reported varying results. Therefore, TLR expression was characterized in human and murine intestinal sections, and TLR function was tested in an IEC line. TLR1, TLR2, and TLR4 are coexpressed on a subpopulation of human and murine IECs that reside predominantly in the intestinal crypt and belong to the enteroendocrine lineage. An enteroendocrine cell (EEC) line demonstrated a similar expression pattern of TLRs as primary cells. The murine EEC line STC-1 was activated with specific TLR ligands: LPS or synthetic bacterial lipoprotein. In STC-1 cells stimulated with bacterial ligands, NF-kappaB and MAPK activation was demonstrated. Furthermore, the expression of TNF and macrophage inhibitory protein-2 were induced. Additionally, bacterial ligands induced the expression of the anti-inflammatory gene transforming growth factor-beta. LPS triggered a calcium flux in STC-1 cells, resulting in a rapid increase in CCK secretion. Finally, conditioned media from STC-1 cells inhibited the production of nitric oxide and IL-12 p40 by activated macrophages. In conclusion, human and murine IECs that express TLRs belong to the enteroendocrine lineage. Using a murine EEC model, a broad range of functional effects of TLR activation was demonstrated. This study suggests a potential role for EECs in innate immune responses.

CCFA microbial-host interactions workshop: highlights and key observations.

This article provides a summary of the proceedings of the CCFA Microbial-Host Interactions Workshop that was held in St. Petersburg, Florida, on March 16-19, 2006. Approximately 75 senior and junior investigators from around the world shared their most current research findings through oral presentations, poster sessions, and active discussion. Because intestinal microbiota are significant contributors in the development of inflammatory bowel diseases (IBD), understanding the body's responses to and interactions with microbes, especially in the colon and distal small intestine, is critical to elucidating the etiology and pathogenesis of IBD and developing effective therapeutic interventions. Major advances have occurred recently in molecular detection of luminal bacterial species, identifying dominant microbial antigens that drive intestinal inflammation, the mechanisms of innate immune and epithelial responses to bacteria, and regulation of inflammation by innate and acquired immune cells.

Comparison of scheduled and episodic treatment strategies of infliximab in Crohn's disease.

BACKGROUND & AIMS: This analysis of Crohn's disease patients treated with infliximab in ACCENT I compared episodic and scheduled treatment strategies under conditions that simulate clinical practice. METHODS: After 5 mg/kg infliximab at week 0, 573 patients were randomized to infusions at weeks 2 and 6 and every 8 weeks until week 46 of placebo (episodic), infliximab 5 mg/kg at weeks 2 and 6 followed by 5 mg/kg (5 mg/kg scheduled) every 8 weeks, or infliximab 5 mg/kg at weeks 2 and 6 followed by 10 mg/kg (10 mg/kg scheduled) every 8 weeks. At or after week 14, treatment could be given with a dose of infliximab 5 mg/kg higher upon loss of response. RESULTS: The efficacy of scheduled infliximab therapy was better than episodic treatment. Crohn's Disease Activity Index (CDAI) scores were consistently significantly better in the 10 mg/kg scheduled maintenance group from weeks 10 to 54, and response and remission rates (combined scheduled) were significantly higher from weeks 10 to 30. A greater proportion of patients achieved complete mucosal healing at week 54 (P = 0.041). A lower proportion developed antibodies to infliximab in the scheduled groups than in the episodic group (9% [5 mg/kg], 6% [10 mg/kg], 28% [episodic], respectively). Scheduled strategy patients had fewer Crohn's disease-related hospitalizations (P = 0.014) and surgeries (P = 0.01) than episodic strategy patients. CONCLUSIONS: The scheduled infliximab groups, particularly the 10 mg/kg group, had better CDAI and Inflammatory Bowel Disease Questionnaire (IBDQ) responses than those in the episodic group. Both scheduled groups had fewer hospitalizations, higher rates of mucosal healing, and fewer developed antibodies than those in the episodic group, with no increase in side effects.

Intestinal heat shock protein 110 regulates expression of CD1d on intestinal epithelial cells.

CD1d is expressed on the surface of professional and nonprofessional APCs, including intestinal epithelial cells (IECs), for a role in the presentation of glycolipid-based antigens to subsets of T cells. The mechanisms that regulate CD1d expression in any cell type are unknown. To investigate the possibility that expression of CD1d is influenced by exogenous factors present within the intestinal lumen, CD1d expression was analyzed in several IEC lines after culturing in the presence of lumenal contents (LC) of the normal human intestine. Exposure of the colon-derived cell lines T84, HT-29, and Caco-2 to soluble LC resulted in a marked induction of CD1d expression as determined by RT-PCR, confocal microscopy, cell surface ELISA, and Western blot analysis. Similarly, exposure of human IECs to LC isolated from mice bred in both specific pathogen-free and germfree conditions also resulted in the induction of CD1d expression, with the maximum CD1d-inducing activity observed in the small intestine. Biochemical and biophysical characterization of the human CD1d-inducing activity identified heat shock protein 110 (Hsp110) as a major functional component of the LC that contributes to CD1d surface regulation, and immunolocalization studies revealed Hsp110 expression in subsets of human IECs in vivo. These data support the presence of a novel autocrine pathway of CD1d regulation by Hsp110.

Delineation of a CD1d-restricted antigen presentation pathway associated with human and mouse intestinal epithelial cells.

BACKGROUND & AIMS: CD1d, a major histocompatibility complex (MHC) class I-related molecule that is responsible for the presentation of glycolipid antigens to subsets of natural killer T (NK-T) cells, is expressed by intestinal epithelial cells (IECs). However, CD1d-restricted antigen presentation has not yet been examined on IECs. METHODS: A mouse intestinal epithelial cell line (MODE-K), a human epithelial cell line (T84), T84 cells transfected with CD1d and/or MHC class II, and freshly isolated human IECs were examined for their ability to present model glycolipid antigens to NK-T cells as defined by interleukin (IL)-2 or IL-4 secretion. RESULTS: MODE-K and freshly isolated human IECs exhibited dose-dependent, CD1d-restricted presentation of the functional glycolipid antigen, alpha-galactosylceramide (alpha GalCer), to the mouse NK-T cell hybridoma, DN32.D3. The human IEC line, T84, mainly presented alpha GalCer when transfected with human CD1d. Presentation of alpha GalCer by CD1d-transfected T84 cells (T84d) to DN32.D3 cells was greater along the basal surface in comparison with the apical surface. Induction of the MHC class II antigen presentation machinery by cotransfecting T84d with the MHC class I transactivator (CIITA) did not alter this polarity of presentation. Neither MODE-K nor T84 cells transfected with CD1d, CD1d plus CIITA, or CD1d plus HLA-DR were able to present glycolipid antigens requiring intracellular processing. The MODE-K cell line could also present alpha GalCer to primary mouse NK-T cells. CONCLUSIONS: CD1d is expressed functionally on IECs with a polarity of presentation (basal > apical) predicting a role in presentation of mucosal glycolipid antigens to local CD1d-restricted T cells.

Maintenance infliximab for Crohn's disease: the ACCENT I randomised trial.

BACKGROUND: We did a randomised controlled trial to assess the benefit of maintenance infliximab therapy in patients with active Crohn's disease who respond to a single infusion of infliximab. METHODS: 573 patients with a score of at least 220 on the Crohn's disease activity index (CDAI) received a 5 mg/kg intravenous infusion of infliximab at week 0. After assessment of response at week 2, patients were randomly assigned repeat infusions of placebo at weeks 2 and 6 and then every 8 weeks thereafter until week 46 (group I), repeat infusions of 5 mg/kg infliximab at the same timepoints (group II), or 5 mg/kg infliximab at weeks 2 and 6 followed by 10 mg/kg (group III). The prespecified co-primary endpoints were the proportion of patients who responded at week 2 and were in remission (CDAI <150) at week 30 and the time to loss of response up to week 54 in patients who responded. Analyses of the co-primary endpoints were by intention to treat. FINDINGS: 335 (58%) patients responded to a single infusion of infliximab within 2 weeks. At week 30, 23 of 110 (21%) group I patients were in remission, compared with 44 of 113 (39%) group II (p=0.003) and 50 of 112 (45%) group III (p=0.0002) patients. Thus, patients in groups II and III combined were more likely to sustain clinical remission than patients in group I (odds ratio 2.7, 95% CI 1.6-4.6). Throughout the 54-week trial, the median time to loss of response was 38 weeks (IQR 15 to >54) and more than 54 weeks (21 to >54) for groups II and III, respectively, compared with 19 weeks (10-45) for group I (p=0.002 and p=0.0002, respectively). Infliximab safety was consistent with that seen in other trials of infliximab in Crohn's disease and rheumatoid arthritis. In particular, the incidence of serious infections was similar across treatment groups. INTERPRETATION: Patients with Crohn's disease who respond to an initial dose of infliximab are more likely to be in remission at weeks 30 and 54, to discontinue corticosteroids, and to maintain their response for a longer period of time, if infliximab treatment is maintained every 8 weeks.