S394 Thursday, 11 September 2014

explore changes during treatment in EEN using sequencingtechnologies.Methods: Stool samples were collected at five time pointsfrom 16 children with active CD undergoing 8-weeks of EEN(Modulen®, Nestle) and from 21 unrelated healthy controls.The V4 region of the bacterial 16S rDNA genes were sequenced(Illumina MiSeq®) and functional analysis of the microbiomewas studied through sequencing of whole-genome shotgunmetagenome libraries (Illumina HiSeq® 2500).Results: Taxonomic profiles distinguish CD patients receivingEEN from healthy controls (p = 0.001). There was a significantreduction in diversity (Shannon’s entropy) in patients comparedwith healthy children at start of therapy (p = 7.031×10 5).Healthy patients were associated with increased relativefrequency of Coprococcus, Pseudobutyrivibrio and Ruminococ-cus sp., whereas CD patients were associated with increasedfrequency of Ruminococcus gnavus and Peptostreptococcus.EEN treatment was significantly associated with a furtherreduction in microbial diversity and communities diversitymoved away from that of controls during EEN. Metagenomicanalysis demonstrated enrichment for pathways involved inphosphorous, lipid, pyruvate and propanoate metabolismduring EEN and depletion of genes associated with sulphurmetabolism.Conclusions: EEN changes the taxonomic and functionalpathway composition of the gut microbiome. Reprogrammingof the microbiome may be important in the efficacy of EEN,but the precise basis for this therapeutic effect still requiresfurther study.

O-06Epigenetic regulation of immune tolerance in intestinalepitheliumM. Mokry*, S. Prelic, C.R.E. Hilvering, E.E.S. Nieuwenhuis.Wilhelmina Children’s Hospital, University Medical CenterUtrecht, Utrecht, The Netherlands

Background: The intestinal epithelium is an importantimmunological organ, which serves as a physical barrierto prevent microbes from entering the body’s interior. Inpatients suffering from Inflammatory Bowel Disease (IBD) thepathology manifests itself by aberrant responses of leukocytesand Intestinal Epithelial Cells (IEC) to luminal antigens.Dysregulated interactions between IEC and luminal microbeshave been implicated in the IBD pathogenesis. We have recentlydemonstrated (Mokry et al. 2014 Gastroenterology) that thenumerous SNPs associated with IBD, which were identifiedin GWASs, co-localize with active DNA regulatory elementsin immune and intestinal epithelial cells. This supports thepossible involvement of epigenetic mechanisms in the IBDpathogenesis.Methods: To better understand the epigenetic mechanismbehind the tolerance of IEC to repetitive microbial exposure,we used ChIP-seq and RNA-seq methods in the epithelialtolerance model system.Results: Using the integrative analysis we show that bothdifferentiation as well as microbial tolerance by IEC areunder the control of shared epigenetic mechanisms. Next weidentified the chromatin remodelers that are involved in themaintenance of the tolerance.Conclusion: Our data identify epigenetic processes involved inimmune tolerance, which can be used as possible targets forthe therapeutic interference.

Poster presentations 10:15 10:45

P1. Poster session: Innate/Adaptive Immunity,Microbiome and Genetics, how does it allconnect?

P-001Characteristics of specific microRNA expression in colonicmucosa in pediatric patients with Crohn’s diseaseN.J. Beres *, D. Szabo, A. Arato, A. Kiss, G. Lendvai, G. Veres.Semmelweis University, Budapest, Hungary

Introduction: The pathomechanism of Crohn’s disease (CD) isunknown. In recent years, there is an increased interest inepigenetic factors, such as a specific group of small, non-codingRNAs, called microRNAs. The altered microRNA expressionhas been linked to several cell function, furthermore, it isestimated that microRNAs play an important role in manydiseases, but only a small number of studies have been done inchildren with CD.Aim: To analyze the miR-146a, miR-155, miR-122 expressionsin the colonic mucosa of pediatric patients with CD.Methods: We analyzed three types of intestinal biopsies:intestinal biopsy with CD (n = 22), with macroscopically intact(uninflamed) (n = 11) and inflamed (n = 11) colonic mucosa, andhealthy controls (n = 16). MicroRNAs expressions were measuredby Real-time PCR.Results: The expressions of miR-146a and miR-155 weresignificantly higher in the intestinal mucosa of children with CDcompared to the control group. This increment was observedin macroscopically inflamed intestinal biopsies in comparisonto controls. MiR-122 expression was significantly higher inmacroscopically intact mucosal biopsies.Conclusions: These results suggest, microRNAs play animportant role in pathogenesis of CD. Further studies arerequired to explore the function of these microRNAs regardingtheir role in illnesses and possible usage as therapeutic targetsand in differential diagnosis.

P-002Butyrate producing microbes at the luminal mucosalinterface are reduced in children newly diagnosed withCrohn’s diseaseD.R. Mack1 *, T. Abujamel2, W. Mottawea2, A. Stintzi2.1Children’s Hospital of Eastern Ontario, Ottawa, Canada,2Department of Biochemistry, Microbiology and Immunology,University of Ottawa, Ottawa, Canada

Introduction: An increase in hydrogen sulphide (H2S) producingmicrobes at the luminal mucosal interface (LMI) is an emergingpicture in the pathogenesis of Crohn’s disease (CD). Butyrateis important in various protective mechanisms includingactivation of genes encoding host H2S detoxification. Disablingthis defense mechanism would increase susceptibility to furtherH2S damage and inflammation. Intestinal microbes generatebutyrate through two pathways: the butyryl-CoA:acetate CoA-transferase (BCoAT) and butyrate kinase (BUK) pathways.Aim: To evaluate if there is a depletion of butyrate-producingbacteria in the intestinal microbiota of CD children.Methods: LMI samples were obtained from proximal colon byflushing sterile water onto mucosa and aspirating the washingsat the time of colonoscopy in an inception CD cohort andhealthy controls. CD severity was determined by the PCDAI.Microbes were identified through 454 pyrosequencing andvalidated using 16S rRNA Illumina sequencing and qPCR analysesfor BCoAT and BUK genes.Results: Most butyrate-producing microbes utilize the BCoATpathway but about 20% use the BUK pathway. No difference wasdetermined in relative quantification of BUK butyrate producers(controls vs. IBD, P> 0.05) regardless of disease severity. In