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ObjectiveIn the management of patients with IBD, there is a need to identify prognostic markers and druggable biological pathways to improve mucosal repair and probe the efficacy of tumour necrosis factor alpha biologics. Vnn1 is a pantetheinase that degrades pantetheine to pantothenate (vitamin B5, a precursor of coenzyme A (CoA) biosynthesis) and cysteamine. Vnn1 is overexpressed by inflamed colonocytes. We investigated its contribution to the tolerance of the intestinal mucosa to colitis-induced injury.DesignWe performed an RNA sequencing study on colon biopsy samples from patients with IBD stratified according to clinical severity and modalities of treatment. We generated the VIVA mouse transgenic model, which specifically overexpresses Vnn1 on intestinal epithelial cells and explored its susceptibility to colitis. We developed a pharmacological mimicry of Vnn1 overexpression by administration of Vnn1 derivatives.ResultsVNN1 overexpression on colonocytes correlates with IBD severity. VIVA mice are resistant to experimentally induced colitis. The pantetheinase activity of Vnn1 is cytoprotective in colon: it enhances CoA regeneration and metabolic adaptation of colonocytes; it favours microbiota-dependent production of short chain fatty acids and mostly butyrate, shown to regulate mucosal energetics and to be reduced in patients with IBD. This prohealing phenotype is recapitulated by treating control mice with the substrate (pantethine) or the products of pantetheinase activity prior to induction of colitis. In severe IBD, the protection conferred by the high induction of VNN1 might be compromised because its enzymatic activity may be limited by lack of available substrates. In addition, we identify the elevation of indoxyl sulfate in urine as a biomarker of Vnn1 overexpression, also detected in patients with IBD.ConclusionThe induction of Vnn1/VNN1 during colitis in mouse and human is a compensatory mechanism to reinforce the mucosal barrier. Therefore, enhancement of vitamin B5-driven metabolism should improve mucosal healing and might increase the efficacy of anti-inflammatory therapy.

Background and Aims NOD2 has emerged as a critical player in the induction of both Th1 and Th2 responses for potentiation and polarisation of antigen-dependent immunity. Loss-of-function mutations in the NOD2-encoding gene and deregulation of its downstream signalling pathway have been linked to Crohn’s disease. Although it is well documented that NOD2 is capable of sensing bacterial muramyl dipeptide, it remains counter-intuitive to link development of overt intestinal inflammation to a loss of bacterial-induced inflammatory response. We hypothesised that a T helper bias could also contribute to an autoimmune-like colitis different from inflammation that is fully fledged by Th1 type cells. Methods An oedematous bowel wall with a mixed Th1/Th2 response was induced in mice by intrarectal instillation of the haptenating agent oxazolone. Survival and clinical scoring were evaluated. At several time points after instillation, colonic damage was assessed by macroscopic and microscopic observations. To evaluate the involvement of NOD2 in immunochemical phenomena, quantitative polymerase chain reaction [PCR] and flow cytometry analysis were performed. Bone marrow chimera experimentation allowed us to evaluate the role of haematopoietic/non-hematopoietic NOD2-expressing cells. Results Herein, we identified a key regulatory circuit whereby NOD2-mediated sensing of a muramyl dipeptide [MDP] by radio-resistant cells improves colitis with a mixed Th1/Th2 response that is induced by oxazolone. Genetic ablation of either Nod2 or Ripk2 precipitated oxazolone colitis that is predominantly linked to a lack of interferon-gamma. Bone marrow chimera experiments revealed that inactivation of Nod2 signalling in non-haematopoietic cells is causing a biased M1-M2 polarisation of macrophages and a decreased frequency of splenic regulatory T cells that correlates with an impaired activation of CD4 + T cells within mesenteric lymph nodes. Mechanistically, mice were protected from oxazolone-induced colitis upon administration of MDP in an interleukin-1- and interleukin-23-dependent manner. Conclusions These findings indicate that Nod2 signalling may prevent pathological conversion of T helper cells for maintenance of tissue homeostasis.

The cellular heterogeneity within a variety of solid tumors is influenced by several type of tumor-associated bacteria through yet poorly understood mechanisms. Unbiased genomic analysis revealed that right-sided colorectal tumors with poorer prognosis are preferentially populated with species related toEscherichia coli, including strains that are producing colibactin. By applying metabolomic profilingin situ, the presence of colibactin-producingEscherichia coli(CoPEC) was identified to establish a high-glycerophospholipid microenvironment within right-sided colorectal tumors that are bearing mutations in either APC or KRAS. Using spatial approaches, we revealed that bacterial microniches are poorly infiltrated with CD8+T cells. The aforementioned alterations in lipid metabolism negatively correlated with immunomodulatory and neurotrophic factors among which the human regenerating family member 3 alpha gene (REG3A). Accordingly, the loss of its ortholog enhances growth at the proximal colon of tumors with a microenvironment that impedes immune surveillance and shares similarities to human right-sided colorectal tumors. This work clarifies how the presence of colibactin-producing bacteria may locally establish tumor heterogeneity for lipid metabolism to promote cancer progression and provide unique insights both for therapeutic intervention and enabling basic research into the mechanisms of microbiota-host interaction.STATEMENT OF SIGNIFICANCEApplyingin situmetabolic imaging to patients’ tumors revealed that the accumulation of colibactin-producing bacteria that locally creates a potential vulnerability to cancer treatments through lipid metabolic reprogramming of tumor cells.

The intestinal microbiota is known to influence postnatal growth. We previously found that a strain of Lactiplantibacillus plantarum (strain Lp WJL ) buffers the adverse effects of chronic undernutrition on the growth of juvenile germ-free mice. Here, we report that Lp WJL sustains the postnatal growth of malnourished conventional animals and supports both insulin-like growth factor–1 (IGF-1) and insulin production and activity. We have identified cell walls isolated from Lp WJL , as well as muramyl dipeptide and mifamurtide, as sufficient cues to stimulate animal growth despite undernutrition. Further, we found that NOD2 is necessary in intestinal epithelial cells for Lp WJL -mediated IGF-1 production and for postnatal growth promotion in malnourished conventional animals. These findings indicate that, coupled with renutrition, bacteria cell walls or purified NOD2 ligands have the potential to alleviate stunting.

International audience; Nonsense mutations are responsible for around 10% of cases of genetic diseases, including cystic fibrosis. 2,6-diaminopurine (DAP) has recently been shown to promote efficient readthrough of UGA premature stop codons. In this study, we show that DAP can correct a nonsense mutation in the Cftr gene in vivo in a new CF mouse model, in utero, and through breastfeeding, thanks, notably, to adequate pharmacokinetic properties. DAP turns out to be very stable in plasma and is distributed throughout the body. The ability of DAP to correct various endogenous UGA nonsense mutations in the CFTR gene and to restore its function in mice, in organoids derived from murine or patient cells, and in cells from patients with cystic fibrosis reveals the potential of such readthrough-stimulating molecules in developing a therapeutic approach. The fact that correction by DAP of certain nonsense mutations reaches a clinically relevant level, as judged from previous studies, makes the use of this compound all the more attractive.

ObjectiveIt is believed that intestinal recruitment of monocytes from Crohn’s Disease (CD) patients who carry NOD2 risk alleles may repeatedly give rise to recruitment of pathogenic macrophages. We investigated an alternative possibility that NOD2 may rather inhibit their differentiation from intravasating monocytes.DesignThe monocyte fate decision was examined by using germ-free mice, mixed bone marrow chimeras and a culture system yielding macrophages and monocyte-derived dendritic cells (mo-DCs). We next asked whether Nod2 in either monocytes or tissue macrophages have distinct resolving properties in colitis.ResultsDespite a similar abundance of monocytes, the intestinal frequency of mo-DCs from Nod2-deficient mice was lowered independently of the changes in the gut microbiota that are caused by Nod2 deficiency. Similarly, the pool of mo-DCs was poorly reconstituted with mobilized bone marrow Nod2-deficient cells. The use of pharmacological inhibitors revealed that activated NOD2 at an early stage of development dominantly inhibits mTOR-mediated macrophage differentiation in a TNFalpha-dependent manner. These observations were supported by the identification of a TNFalpha-dependent response to MDP that is specifically lost in CD14-expressing blood cells bearing the frameshift mutation in NOD2. Accordingly, loss of NOD2 in monocytes lowers glycolytic reserve, CD115 expression and pro-resolving features. Dietary intake of aryl hydrocarbon receptor (AHR) agonists that promotes mo-DCs generation improves colitis in Nod2-deficient mice to the same extent as what is observed upon macrophage ablation of Nod2.ConclusionNOD2 negatively regulates a macrophage developmental program through a feed-forward loop that could be exploited for overcoming resistance to anti-TNF therapy in CD.Significance of this studyWhat is already known about this subject?Loss of NOD2 function is predisposing to Crohn’s disease.Rapamycin, a serine/THR kinase inhibitor of mammalian target (mTOR) has been reported as potentially effective treatment in discrete subset of CD patients with refractory colitis.The NOD2 protein promotes the chemokine CCL2-dependent recruitment of inflammatory monocytes in response to tissue injury.An accumulation of CCR2-expressing monocytes and inflammatory macrophages is observed within the intestinal mucosa of CD patients including those resistant to anti-TNF therapy.Activated NOD2 enhances proinflammatory activity of CX3CR1intLy6Chi effector monocytes.The monocyte fate toward mo-DCs is orchestrated by the aryl hydrocarbon receptor.What are the new findings?NOD2 has a hierarchically dominant negative role on the mTORC-driven monocyte conversion to inflammatory macrophages independently of the changes in the gut microbiota that are caused by Nod2 deficiency.A defect in monocytes fate at the early stage allow the expansion of pathogenic macrophages in Nod2-deficient mice at the expense of mo-DC.Adoptive transfer of Nod2-deficient monocytes into wild-type mice was sufficient to exacerbate DSS-induced intestinal damage.The glycolytic reserve of monocytes and their ability to respond to M-CSF is lowered upon loss of NOD2 signalling.Deletion of NOD2 in macrophage improves colitis to the same extent as dietary supplementation of AHR agonist in mice.The recognition of the gut microbiota by NOD2 is required for de novo reconstitution of mo-DCs in the lamina propria of the murine intestine, while having minimal effect on the mobilization of their precursors to the intestinal mucosa.How might it impact on clinical practice in the foreseeable future?This study might contribute to the development of novel mTORC-based therapeutic strategies for improving the response to biologics by restoring the ability of circulating monocytes to reconstitute the pool of mo-DCs during homeostatic turnover and upon tissue injury. It may thereby prevent the accumulation of pathogenic macrophages in patients with loss-of-function NOD2 alleles, which fail to respond to anti-TNF and are at greater risk of developing stricturing disease.

SummaryRecently, an intestinal dysbiotic microbiota with enrichment in oral cavity bacteria has been described in colorectal cancer (CRC) patients. Here we characterized and investigated one of these oral pathobionts, the Gram-positive anaerobic coccusParvimonas micra.We identified two phylotypes (A and B) exhibiting different phenotypes and adhesion capabilities. We observed a strong association of phylotype A with CRC, with its higher abundance in feces and in tumoral tissue compared with the normal homologous colonic mucosa, which was associated with a distinct methylation status of patients. By developing anin vitrohypoxic co-culture system of human primary colonic cells with anaerobic bacteria, we showed thatP. micraphylotype A alters the DNA methylation profile promoters of key tumor-suppressor genes, oncogenes, and genes involved in epithelial-mesenchymal transition. In colonic mucosa of CRC patients carryingP. micraphylotype A, we found similar DNA methylations alterations, together with significant enrichment of differentially expressed genes in pathways involved in inflammation, cell adhesion, and regulation of actin cytoskeleton, providing evidence ofP. micrapossible role in the carcinogenic process.

ObjectiveTo assess whether gut microbiota composition is associated with patient characteristics and may have predictive value on the response to TNF inhibitor (TNFi) treatment in axial spondyloarthritis (AxSpA).MethodsThe study involved 61 patients fulfilling the Assessment of SpondyloArthritis International Society classification criteria for AxSpA. All patients had active disease despite non-steroidal anti-inflammatory drugs intake and were eligible for treatment with a TNFi. At baseline, the mean Ankylosing Spondylitis Disease Activity Score was 2.9±1 and mean C reactive protein (CRP) level 9.7±11.4 mg/L. Bacterial 16S ribosomal RNA gene sequencing was performed on stool samples collected at baseline (month 0 (M0)) and 3 months after TNFi initiation (month 3 (M3)). Alpha and beta diversity metrics were calculated on the relative abundance of core operational taxonomic units (OTUs).ResultsThe HLA-B27 status affected at least in part the global composition of faecal microbiota at M0 as well as the abundance/prevalence of several anaerobic bacteria in the familiesOscillospiraceae,LachnospiraceaeandBifidobacteriaceae. In contrast, smoking affected the global composition of faecal microbiota at both M0 and M3. The prevalence/abundance of seven bacterial OTUs at M0 was associated with response to TNFi treatment. One of the candidates, present only in non-responders, is the genusSutterella, and the other six candidates are in the classClostridia.ConclusionsSeveral SpA patients’ characteristics modulate the composition of gut microbiota as did TNFi treatment. Moreover, the abundance/prevalence of seven OTUs at baseline may be used as a novel non-invasive index that predicts the response to TNFi with greater accuracy than HLA-B27 status, CRP level and measures of disease activity.

Background & Aims Loss-of-function variants in nucleotide-binding oligomerization domain-containing protein 2 (NOD2) impair the recognition of the bacterial cell wall component muramyl-dipeptide and are associated with an increased risk for developing Crohn’s disease. Likewise, exposure to antibiotics increases the individual risk for developing inflammatory bowel disease. Here, we studied the long-term impact of NOD2 on the ability of the gut bacterial and fungal microbiota to recover after antibiotic treatment. Methods Two cohorts of 20-week-old and 52-week-old wild-type (WT) C57BL/6J and NOD2 knockout (Nod2-KO) mice were treated with broad-spectrum antibiotics and fecal samples were collected to investigate temporal dynamics of the intestinal microbiota (bacteria and fungi) using 16S ribosomal RNA and internal transcribed spacer 1 sequencing. In addition, 2 sets of germ-free WT mice were colonized with either WT or Nod2-KO after antibiotic donor microbiota and the severity of intestinal inflammation was monitored in the colonized mice. Results Antibiotic exposure caused long-term shifts in the bacterial and fungal community composition. Genetic ablation of NOD2 was associated with delayed body weight gain after antibiotic treatment and an impaired recovery of the bacterial gut microbiota. Transfer of the postantibiotic fecal microbiota of Nod2-KO mice induced an intestinal inflammatory response in the colons of germ-free recipient mice compared with respective microbiota from WT controls based on histopathology and gene expression analyses. Conclusions Our data show that the bacterial sensor NOD2 contributes to intestinal microbial community composition after antibiotic treatment and may add to the explanation of how defects in the NOD2 signaling pathway are involved in the etiology of Crohn’s disease., Graphical abstract

Live biotherapeutic products constitute an emerging therapeutic approach to prevent or treat inflammatory bowel diseases. Lactobacillus acidophilus is a constituent of the human microbiota with probiotic potential, that are illustrated by direct and indirect antimicrobial activity against several pathogens and improvement of intestinal inflammation. In this study, we evaluated the anti-inflammatory properties of the L. acidophilus strain BIO5768 and assessed the underlying mechanisms of action. BIO5768 was able to counteract the acute colitis that is induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS). When administered alone or in combination with Bifidobacterium animalis spp. lactis BIO5764 and Limosilactobacillus reuteri, BIO5768 was also able to alleviate intestinal inflammation induced by Citrobacter rodentium infection. Supplementation of naïve mice with either strain BIO5768 alone or as mixture, increased the gene expression of several target genes involved in immune signaling, including c-type lectin Reg3 gamma. Consistently, the ability of innate lymphoid cells to secrete IL-22 was enhanced in response to BIO5768. Interestingly, the aforementioned responses were shown to be independent of NOD2 and Th17 signaling in mice that were mono-colonized with BIO5768. In conclusion, we identify a new potential probiotic strain with the ability for the management of inflammatory bowel diseases, and provide some insights into its mode of action.

Type I interferon signaling contributes to the development of innate and adaptive immune responses to either viruses, fungi, or bacteria. However, amplitude and timing of the interferon response is of utmost importance for preventing an underwhelming outcome, or tissue damage. While several pathogens evolved strategies for disturbing the quality of interferon signaling, there is growing evidence that this pathway can be regulated by several members of the Nod-like receptor (NLR) family, although the precise mechanism for most of these remains elusive. NLRs consist of a family of about 20 proteins in mammals, which are capable of sensing microbial products as well as endogenous signals related to tissue injury. Here we provide an overview of our current understanding of the function of those NLRs in type I interferon responses with a focus on viral infections. We discuss how NLR-mediated type I interferon regulation can influence the development of auto-immunity and the immune response to infection.

Radiation therapy (RT) is an essential component of therapy either curative or palliative armamentarium in oncology, but its efficacy varies considerably among patients through many extrinsic and intrinsic mechanisms of the tumour, which are beginning to be better understood. Recent studies have shown that the gut microbiome represents a key factor in the modulation of the systemic immune response and consequently on patients' outcome. Moreover, the emergence of biomarkers that are derived from the gut microbiota has fuelled the development of adjuvant strategies for patients treated with immunotherapy in combination or not with RT. Despite progress in development of more precise radiotherapy techniques, almost all patients undergoing RT to the abdomen, pelvis, or rectum develop acute adverse events as a consequence of several dose-limiting parameters such as the location of irradiation that may subsequently damage normal tissue including the intestinal epithelium. Several lines of evidence in preclinical models identified that vancomycin improves RT-induced gastrointestinal toxicities such as diarrhea and oral mucositis. In order to gain further insight into this rapidly evolving field, we have systematically reviewed the studies that have described how the gut microbiome may directly or indirectly modulate RT efficacy and its gastro-intestinal toxicities. Lastly, we outline current knowledge gaps and discuss potentially more satisfactory therapeutic options to restore the functionality of the gut microbiome of patients treated with RT.

Introduction NOD1 is an innate pattern-recognition sensor for Gram-negative peptidoglycan (PG) that is involved in the development of allergic asthma and signals through the kinase RIPK2. The aim of this study was to investigate the role of NOD1 in HDM-induced asthma. Methods Nod1-/-, Ripk2-/− and WT mice were subjected to a protocol of HDM-induced asthma. Faecal microbiota transplantation from Nod1-/− and WT was performed in germ free (GF) mice before HDM asthma protocol. HDM content was analysed by mass spectrometry. A NOD1 reporter cell model and the human bronchial epithelial cell line Beas2B were stimulated with HDM. Results Nod1-/− and Ripk2-/− mice exhibited reduced asthma features, including decreased airway hyperresponsiveness (AHR), less pulmonary inflammation and lower levels of Th2-related cytokines and chemokines. However, no differences in any asthma parameters were found between GF mice transplanted with either Nod1-/− or WT microbiota. HDM mass spectrometry analysis evidenced the presence of PG-derived NOD1 ligands, and a PG-dependent activation was found in the NOD1 reporter model. Furthermore, the HDM stimulation of human epithelial Beas2B cells led to NOD1 activation and RIPK2 signalling. Accordingly, when WT mice were subjected to the asthma protocol with PG-depleted HDM, but not to LPS-reduced HDM, asthma features were notably reduced. Conclusions HDM-derived microbiota promotes allergic airway disease through NOD1 sensing, suggesting that this pathway may provide attractive therapeutic targets.

Resume A partir de la naissance, chaque etre humain etablit une symbiose avec son microbiote qui joue un role clef dans le maintien de sa sante et de son bien-etre. Cette co-existence symbiotique individuelle est le resultat d’une succession d’enrichissements de la diversite des microorganismes commensaux par des apports exterieurs. Cette diversite se trouve neanmoins menacee depuis peu par des changements drastiques dans nos habitudes de vie comme la prise en charge des naissances, l’environnement exterieur, l’alimentation et les pratiques medicales. Les deux dernieres generations ont ete le cadre de modifications importantes des modes de vies et d’alimentation, avec une augmentation de la sedentarite, une suralimentation et une exposition importante aux medicaments et aux polluants. Nous sommes maintenant en mesure d’evaluer l’impact de ces changements sur la diversite du microbiote intestinal. Parallelement a ces modifications du mode de vie, on a pu observer une explosion de l’incidence de maladies liees a un dysfonctionnement du systeme immunitaire comme les maladies metaboliques, les allergies et les maladies inflammatoires et plus etonnamment des maladies neurodegeneratives et des desordres psychiatriques. Le microbiote est devenu un sujet d’actualite dans la communaute scientifique ainsi que dans les medias grand public. Le nombre de publications scientifiques a augmente d’un facteur trois sur les cinq dernieres annees, les domaines des maladies gastro-intestinales et liees aux dysfonctionnements metaboliques etant les plus etudies. D’un point de vue de la propriete intellectuelle, les familles de brevets traitant du microbiote ont plus que double sur la meme periode. En parallele, les financements provenant soit des organisations etatiques (par exemple du National Institute of Health [NIH] qui finance les recherches essentiellement dans le domaine des allergies, des anti-infectieux, du cancer et des maladies cardio-vasculaires, ou de la Maison Blanche qui a lance l’initiative nationale sur le microbiome) soit des entreprises pharmaceutiques ont suivi la meme tendance et refletent une poussee des investissements et un soutien important de ce domaine de la recherche sur le microbiote. Tous les acteurs majeurs de la sante investissent actuellement dans la recherche sur le microbiome ce qui se traduit par le grand nombre de contrats et de financements signes en 2015. La table ronde des Ateliers de Giens s’est interessee a envisager comment la medecine de demain, en considerant l’homme comme un supra-organisme symbiotique homme–microbes, pourra beneficier du savoir acquis sur les fonctions du microbiote et sur le microbiome en tant qu’outil therapeutique. La reflexion de notre groupe de travail a ete structuree autour de quatre domaines d’innovation qui pourraient beneficier des efforts realises actuellement afin de dechiffrer les interactions entre cellules humaines et le microbiome intestinal, en tant qu’element central de la sante humaine, c’est-a-dire : 1) le developpement d’outils de stratification et de monitorage ; 2) l’identification de cibles originales et de nouvelles drogues a partir du microbiome en tant que partie de notre supra-genome ; 3) l’exploitation du microbiote en tant que cible therapeutique qui peut etre modulable ; et enfin, 4) comme source de biotherapeutiques vivants ou d’adjuvants. Ces quatre chapitres vont permettre de montrer comment le microbiote a modifie notre facon de considerer un grand nombre de maladies chroniques et incurables comme les consequences d’une dysbiose etablie et durable. L’analyse en profondeur du microbiote est le point de depart d’un des plus vastes chantiers de recherches qui permettra l’amelioration de la sante humaine et animale et qui deviendra la source d’innovations medicales pour couvrir les gaps therapeutiques d’aujourd’hui. Nous proposons donc une serie de recommandations que nous adressons aux chercheurs academiques, aux cliniciens ainsi qu’aux autorites de sante, afin que les analyses du microbiote gagnent en fiabilite et solidite. Ceci permettra d’accelerer le processus de decouvertes et ainsi que leurs applications afin que tous puissent en beneficier.

In a recently published letter,1 Dr Beaulieu questions our recent publication suggesting that α6 integrin acts as a tumour suppressor gene in colorectal cancer (CRC),2 given the apparent antagonistic role of α6A and α6B integrin isoforms in the intestine. We thank him for raising this important issue and welcome the opportunity of clarifying the topic. We showed that mice failing to express the α6 integrin (both α6A and α6B isoforms) specifically in intestinal epithelial cells (α6ΔIEC) spontaneously develop fully penetrant colitis and adenocarcinoma afterwards.2 These mice display epithelium detachment from the basement membrane, followed …

Summary The activator and composition of the NLRP6 inflammasome remain poorly understood. We find that lipoteichoic acid (LTA), a molecule produced by Gram-positive bacteria, binds and activates NLRP6. In response to cytosolic LTA or infection with Listeria monocytogenes, NLRP6 recruited caspase-11 and caspase-1 via the adaptor ASC. NLRP6 activation by LTA induced processing of caspase-11, which promoted caspase-1 activation and interleukin-1β (IL-1β)/IL-18 maturation in macrophages. Nlrp6−/− and Casp11−/− mice were less susceptible to L. monocytogenes infection, which was associated with reduced pathogen loads and impaired IL-18 production. Administration of IL-18 to Nlrp6−/− or Casp11−/− mice restored the susceptibility of mutant mice to L. monocytogenes infection. These results reveal a previously unrecognized innate immunity pathway triggered by cytosolic LTA that is sensed by NLRP6 and exacerbates systemic Gram-positive pathogen infection via the production of IL-18.

International audience; Prominent changes in the gut microbiota (referred to as "dysbiosis") play a key role in the development of allergic disorders, but the underlying mechanisms remain unknown. Study of the delayed-type hypersensitivity (DTH) response in mice contributed to our knowledge of the pathophysiology of human allergic contact dermatitis. Here we report a negative regulatory role of the RIG-I-like receptor adaptor mitochondrial antiviral signaling (MAVS) on DTH by modulating gut bacterial ecology. Cohousing and fecal transplantation experiments revealed that the dysbiotic microbiota of Mavs -/- mice conferred a proallergic phenotype that is communicable to wild-type mice. DTH sensitization coincided with increased intestinal permeability and bacterial translocation within lymphoid organs that enhanced DTH severity. Collectively, we unveiled an unexpected impact of RIG-I-like signaling on the gut microbiota with consequences on allergic skin disease outcome. Primarily, these data indicate that manipulating the gut microbiota may help in the development of therapeutic strategies for the treatment of human allergic skin pathologies.

International audience; Background. Postoperative complications are relatively frequent in Crohn's disease (CD) and several risk factors have been identified. The influence of genetic factors, however is unknown.Methods. CD patients who underwent CD-related bowel resection were identified from the "Nancy IBD cohort." Postoperative complications were defined as intraabdominal infectious complications and non intraabdominal infectious complications occurring within 90 days after operation. The influence of 203 single nucleotide polymorphisms on postoperative complication rates was analyzed.Results. Of the 137 patients who had undergone a CD-related bowel resection in our cohort, postoperative complications occurred in 34 cases (24.8 %). Postoperative intraabdominal infections occurred in 18 cases (13. 1%): 12 had anastomotic leakage and 6 had intraabdominal abscesses. In multivariate analysis, current smoker status (odds ratio [OR], 2.71; 95% CI, 1.18-6.21; P =.02) and homozygosity for the risk allele (T) Nucleotide-binding Oligomerization Domain-containing protein 2 (rs5743289; NOD2; OR, 2.07 [95% CI 1.15-3.72]; P =.01) were independent risk factors of postoperative intraabdominal infectious complications. Current smoker status NOD2 homozygosity for the risk allele (T) were not associated with non intraabdominal infectious complications.Conclusion. Current smoker status was associated with increased risk of postoperative intraabdominal infectious complications. A novel association between the NOD2 allele and an increased risk of postoperative intraabdominal infectious, complications was observed in this study.

A. Palotie on työryhmän Int IBD Genetics Consortium jäsen. One goal of human genetics is to understand the genetic basis of disease, a challenge for diseases of complex inheritance because risk alleles are few relative to the vast set of benign variants. Risk variants are often sought by association studies in which allele frequencies in case subjects are contrasted with those from population-based samples used as control subjects. In an ideal world we would know population-level allele frequencies, releasing researchers to focus on case subjects. We argue this ideal is possible, at least theoretically, and we outline a path to achieving it in reality. If such a resource were to exist, it would yield ample savings and would facilitate the effective use of data repositories by removing administrative and technical barriers. We call this concept the Universal Control Repository Network (UNICORN), a means to perform association analyses without necessitating direct access to individual-level control data. Our approach to UNICORN uses existing genetic resources and various statistical tools to analyze these data, including hierarchical clustering with spectral analysis of ancestry; and empirical Bayesian analysis along with Gaussian spatial processes to estimate ancestry-specific allele frequencies. We demonstrate our approach using tens of thousands of control subjects from studies of Crohn disease, showing how it controls false positives, provides power similar to that achieved when all control data are directly accessible, and enhances power when control data are limiting or even imperfectly matched ancestrally. These results highlight how UNICORN can enable reliable, powerful, and convenient genetic association analyses without access to the individual-level data.

Background and aims Post-operative recurrence is frequent in Crohn's disease. Genetic factors associated with post-operative recurrence remain poorly understood. Identification of genetic variants associated with repeat surgery would allow risk stratification of patients who may benefit from early aggressive therapy and/or post-operative prophylactic treatment. Methods Crohn's disease patients who had at least one bowel resection were retrospectively identified from the “Nancy IBD cohort”. Covariates and potential interactions were assessed using the Cox proportional hazard model. Kaplan–Meier curves for time to surgical recurrence were developed for 200 genetic variants and analyzed with the log-rank test. Results 137 patients had at least 1 resection in our cohort: 38 had a surgical recurrence (28%). In multivariate analysis, current smoker status (OR 6.97, 95% CI 1.85–26.22, p = 0.004), post-operative complications after prior surgery (OR 2.72, 95% CI 1.02–7.22, p = 0.044), and Caspase recruitment domain-containing protein 8 (CARD8) homozygosity for the risk allele (OR 7.56, 95% CI 1.13–50.37, p = 0.036) remained significantly and independently associated with surgical recurrence. Conclusion Current smoker status was associated with increased risk of surgical recurrence. A novel association between CARD8 and increased risk of surgical recurrence in Crohn's disease was observed. CARD8 could be a new marker for risk stratification and prevention of recurrent surgery.

Introduction: While there is increasing evidence that it exists a link between asthma development, early life exposure to allergens like house dust mite (HDM) and the microbiome composition, the underlying mechanisms remain elusive. While Nucleotide-binding oligomerization domain 1 (NOD1) has been shown to regulate the gut microbiota composition, our previous findings showed that a Nod1 agonist used as a systemic adjuvant exacerbates ovalbumin-induced Th2-mediated allergic asthma and more recently that HDM-induced asthma is improved in Nod1-deficient mice. Aims and objectives: The aim of his study was to evaluate if the intestinal dysbiosis present in Nod1 deficient mice may modify HDM-induced pulmonary inflammation. Methods: The role of NOD1 was investigated in the HDM-induced asthma model, using Wild-Type, NOD1 deficient mice and Ripk2 deficient mice. Fecal transplantation of Nod1 deficient or WT mice into germfree (GF) mice was performed and HDM-induced asthma evaluated. We measured airway hyperreactivity, total and differential cell counts in bronchoalveolar lavage (BAL), Th2 cytokines and chemokines in lung protein extracts and total IgE levels in the serum. Results: Our results show that HDM-sensitized/challenged NOD1 and Ripk2 deficient mice exhibited less pulmonary inflammation when compared to the wild-type mice. However there was no difference between GF mice transplanted with either Nod1 deficient or WT microbiota. Conclusion: Our results suggest that NOD1-deficient dysbiosis is not responsible for decreasing allergic inflammation parameters and suggest that the allergen may directly activate NOD1 receptor.

International audience; Upon oral infection with Toxoplasma gondii cysts (76 K strain) tachyzoites are released into the intestinal lumen and cross the epithelial barrier causing damage and acute intestinal inflammation in C57BL/6 (B6) mice. Here we investigated the role of microbiota and IL-22 in T.gondii-induced small intestinal inflammation. Oral T.gondii infection in B6 mice causes inflammation with IFNγ and IL-22 production. In IL-22-deficient mice, T.gondii infection augments the Th1 driven inflammation. Deficiency in either IL-22bp, the soluble IL-22 receptor or Reg3γ, an IL-22-dependent antimicrobial lectin/peptide, did not reduce inflammation. Under germ-free conditions, T.gondii-induced inflammation was reduced in correlation with parasite load. But intestinal inflammation is still present in germ-free mice, at low level, in the lamina propria, independently of IL-22 expression. Exacerbated intestinal inflammation driven by absence of IL-22 appears to be independent of IL-22 deficiency associated-dysbiosis as similar inflammation was observed after fecal transplantation of IL-22-/- or WT microbiota to germ-free-WT mice. Our results suggest cooperation between parasite and intestinal microbiota in small intestine inflammation development and endogenous IL-22 seems to exert a protective role independently of its effect on the microbiota. In conclusion, IL-22 participates in T.gondii induced acute small intestinal inflammation independently of microbiota and Reg3γ.

ObjectiveLoss of the Crohn’s disease predisposing NOD2 gene results in an intestinal microenvironment conducive for colonisation by attaching-and-effacing enteropathogens. However, it remains elusive whether it relies on the intracellular recruitment of the serine-threonine kinase RIPK2 by NOD2, a step that is required for its activation of the transcription factor NF-κB.DesignColonisation resistance was evaluated in wild type and mutant mice, as well as in ex-germ-free (ex-GF) mice which were colonised either with faeces from Ripk2-deficient mice or with bacteria with similar preferences for carbohydrates to those acquired by the pathogen. The severity of the mucosal pathology was quantified at several time points postinfection by using a previously established scoring. The community resilience in response to infection was evaluated by 16S ribosomal RNA gene sequence analysis. The control of pathogen virulence was evaluated by monitoring the secretion of Citrobacter-specific antibody response in the faeces.ResultsPrimary infection was similarly outcompeted in ex-GF Ripk2-deficient and control mice, demonstrating that the susceptibility to infection resulting from RIPK2 deficiency cannot be solely attributed to specific microbiota community structures. In contrast, delayed clearance of Citrobacter rodentium and exacerbated histopathology were preceded by a weakened propensity of intestinal macrophages to afford innate lymphoid cell activation. This tissue protection unexpectedly required the regenerating family member 3β by instigating interleukin (IL) 17A-mediated neutrophil recruitment to the intestine and subsequent phosphorylation of signal transducer and activator of transcription 3.ConclusionsThese results unveil a previously unrecognised mechanism that efficiently protects from colonisation by diarrhoeagenic bacteria early in infection.

Emergency monocytopoiesis is an inflammation-driven hematological process that supplies the periphery with monocytes and subsequently with macrophages and monocyte-derived dendritic cells. Yet, the regulatory mechanisms by which early bone marrow myeloid progenitors commit to monocyte-derived phagocytes during endotoxemia remains elusive. Herein, we show that type I interferons signaling promotes the differentiation of monocyte-derived phagocytes at the level of their progenitors during a mouse model of endotoxemia. In this model, we characterized early changes in the numbers of conventional dendritic cells, monocyte-derived antigen-presenting cells and their respective precursors. While loss of caspase-1/11 failed to impair a shift toward monocytopoiesis, we observed sustained type-I-IFN-dependent monocyte progenitors differentiation in the bone marrow correlated to an accumulation of Mo-APCs in the spleen. Importantly, IFN-alpha and -beta were found to efficiently generate the development of monocyte-derived antigen-presenting cells while having no impact on the precursor activity of conventional dendritic cells. Consistently, the LPS-driven decrease of conventional dendritic cells and their direct precursor occurred independently of type-I-IFN signaling in vivo. Our characterization of early changes in mononuclear phagocytes and their dependency on type I IFN signaling during sepsis opens the way to the development of treatments for limiting the immunosuppressive state associated with sepsis.

International audience