Bénédicte Pigneur

A decrease in the abundance and biodiversity of intestinal bacteria within the dominant phylum Firmicutes has been observed repeatedly in Crohn disease (CD) patients. In this study, we determined the composition of the mucosa-associated microbiota of CD patients at the time of surgical resection and 6 months later using FISH analysis. We found that a reduction of a major member of Firmicutes, Faecalibacterium prausnitzii, is associated with a higher risk of postoperative recurrence of ileal CD. A lower proportion of F. prausnitzii on resected ileal Crohn mucosa also was associated with endoscopic recurrence at 6 months. To evaluate the immunomodulatory properties of F. prausnitzii we analyzed the anti-inflammatory effects of F. prausnitzii in both in vitro (cellular models) and in vivo [2,4,6-trinitrobenzenesulphonic acid (TNBS)-induced] colitis in mice. In Caco-2 cells transfected with a reporter gene for NF-kappaB activity, F. prausnitzii had no effect on IL-1beta-induced NF-kappaB activity, whereas the supernatant abolished it. In vitro peripheral blood mononuclear cell stimulation by F. prausnitzii led to significantly lower IL-12 and IFN-gamma production levels and higher secretion of IL-10. Oral administration of either live F. prausnitzii or its supernatant markedly reduced the severity of TNBS colitis and tended to correct the dysbiosis associated with TNBS colitis, as demonstrated by real-time quantitative PCR (qPCR) analysis. F. prausnitzii exhibits anti-inflammatory effects on cellular and TNBS colitis models, partly due to secreted metabolites able to block NF-kappaB activation and IL-8 production. These results suggest that counterbalancing dysbiosis using F. prausnitzii as a probiotic is a promising strategy in CD treatment.

BACKGROUND: Crohn's disease (CD)-associated dysbiosis is characterised by a loss of Faecalibacterium prausnitzii, whose culture supernatant exerts an anti-inflammatory effect both in vitro and in vivo. However, the chemical nature of the anti-inflammatory compounds has not yet been determined. METHODS: Peptidomic analysis using mass spectrometry was applied to F. prausnitzii supernatant. Anti-inflammatory effects of identified peptides were tested in vitro directly on intestinal epithelial cell lines and on cell lines transfected with a plasmid construction coding for the candidate protein encompassing these peptides. In vivo, the cDNA of the candidate protein was delivered to the gut by recombinant lactic acid bacteria to prevent dinitrobenzene sulfonic acid (DNBS)-colitis in mice. RESULTS: The seven peptides, identified in the F. prausnitzii culture supernatants, derived from a single microbial anti-inflammatory molecule (MAM), a protein of 15 kDa, and comprising 53% of non-polar residues. This last feature prevented the direct characterisation of the putative anti-inflammatory activity of MAM-derived peptides. Transfection of MAM cDNA in epithelial cells led to a significant decrease in the activation of the nuclear factor (NF)-κB pathway with a dose-dependent effect. Finally, the use of a food-grade bacterium, Lactococcus lactis, delivering a plasmid encoding MAM was able to alleviate DNBS-induced colitis in mice. CONCLUSIONS: A 15 kDa protein with anti-inflammatory properties is produced by F. prausnitzii, a commensal bacterium involved in CD pathogenesis. This protein is able to inhibit the NF-κB pathway in intestinal epithelial cells and to prevent colitis in an animal model.

BACKGROUND: Childhood-onset Crohn's disease (CD) might reflect a more severe form of disease. To test this hypothesis we analyzed the long-term natural history of CD in an adult cohort of patients with childhood-onset compared to adult-onset CD. METHODS: We selected 206 childhood-onset CD patients among 2992 adult patients with a diagnosis of CD established before December 31, 2000. Disease characteristics were prospectively assessed during follow-up until December 2007 and compared to adult-onset CD patients matched 2 to 1 on gender, year of CD diagnosis, and disease location. RESULTS: Compared to adult-onset CD, patients with childhood-onset CD were more likely to have a severe disease, with an increased year-by-year disease activity index (37% of patient-years in childhood-onset group versus 31% in the adult-onset group, P < 0.001). Immunosuppressant requirement was also increased with a 10-year cumulative risk of 54 +/- 3% in childhood-onset CD group versus 45 +/- 2%, in the adult-onset CD group (P < 0.001). Cumulative risks of stricturing and penetrating complications and surgical resections were not statistically different between groups. Accordingly, these events occurred at a younger age in the childhood-onset CD group. At the age of 30 years the actuarial risk of having undergone an extensive intestinal resection was 48 +/- 5% in the childhood-onset group versus 14 +/- 2% in the adult-onset group (P < 0.001). CONCLUSIONS: Patients with childhood-onset CD exhibit a more active disease and require more immunosuppressive therapy. This feature is observed irrespective of the disease location, suggesting an intrinsic more severe phenotype.

OBJECTIVES: Early onset inflammatory bowel diseases (EO-IBD) developing during the first year of life are likely to reflect inherited defects in key mechanism(s) controlling intestinal homeostasis, as recently suggested for interleukin 10 (IL10). Thus, we aimed to further elaborate the hypothesis of defective anti-inflammatory responses in patients with IBD. METHODS: The capacities of transforming growth factor β (TGFβ) and IL10 to inhibit proinflammatory cytokine production by monocyte-derived dendritic cells (MoDC) or peripheral blood cells (PBMC) was analyzed in 75 children with IBD, including 13 infants with EO-IBD (in whom autoimmune diseases or classical immunodeficiencies were ruled out). IL10 receptor-A/-B expression, STAT3 activation in response to IL6, IL10, IL21, IL22 were analyzed by FACS and western blotting. IL10RA and B genes were sequenced. The response to IL22 was tested in ileal/colonic tissue cultures. Tissue gene expression was analyzed by Taqman real-time polymerase chain reaction. RESULTS: Production of IL10 in response to bacterial motifs was normal in all IBD patients. In contrast to our original hypothesis, no defect of the anti-inflammatory potential of TGFβ and IL10 was observed in children with IBD or EO-IBD except two infants who presented with granuloma-positive colitis at 3 months of life: no response to IL10 was observed secondary to mutations in the α (p.R262C) or β (p.E141X) chain of IL10R, respectively, although a fully functional Jak-STAT3 pathway was present in both patients. When analyzing the regulation of intestinal bacterial clearance, we detected a defect in the patient with absent IL10 RB to upregulate protective transcripts in response to IL22, whereas all other EO-IBD patients, including the patient with an abnormal α chain, responded normally. CONCLUSIONS: Impaired IL10 signaling characterizes a subgroup of IBD patients, whereas the majority of children with severe IBD including EO forms normally produces and responds to IL10. Defective IL22 signaling may additionally impair intestinal epithelial clearance. Our data point out the complexity of IBD, which represent a group of distinct diseases with several pathogenetic abnormalities.

BACKGROUND: Nutritional therapy has an established role as induction therapy in paediatric Crohn's disease. However, compliance is the main difficulty and may be greatly influenced by the administration route. AIM: To analyse the efficiency of exclusive nutrition to induce remission in children with Crohn's disease comparing fractionated oral vs. continuous enteral feeding. METHODS: The medical records of 106 patients treated by exclusive nutritional therapy [Modulen IBD (R)] by either oral or continuous enteral route were reviewed retrospectively. Comparative analyses of remission rates, changes in anthropometry, Paediatric Crohn's disease Activity Index (PCDAI), laboratory indices and compliance rates were performed. RESULTS: On exclusive enteral nutrition, at 8 weeks, 34/45 patients achieved remission in the oral group (75% on intention-to-treat analysis) and 52/61 (85%) in the enteral nutrition group (P = 0.157). All patients showed a significant decrease in disease severity assessed by PCDAI (P < 0.0001) and significant improvements in anthropometric measures and inflammatory indices. No difference was observed whether Modulen IBD was administered orally or by continuous enteral feeding, apart from weight gain, which was greater in the enteral group (P = 0.041). In a subgroup of patients, mucosal healing was evidenced on follow-up endoscopies showing a clear correlation to remission. Compliance rates (87% and 90%) were similar. Nevertheless, noncompliant patients had lower mucosal healing and remission rates. CONCLUSIONS: These retrospective data suggest that the use of fractionated oral nutritional therapy might be as efficacious as continuous enteral administration to induce remission and mucosal healing in children with Crohn's disease. However, appropriate prospective clinical trials are needed to confirm these findings.