towards the sterile organs. This could be explained by increased intestinal permeability inresponse to CPF exposure. This hypothesis is validated by measures of tight junction proteinsexpression and by histological observations.

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Emerging Role of Fecal Microbiota Therapy in the Treatment of RecurrentClostridium difficile Infection in ChildrenShashank Garg, W. F. Fricke, Mohit Girotra, Erik C. von Rosenvinge, Anand Dutta,Sudhir K. Dutta

Background: Recurrent Clostridium difficile infection (RCDI) is a growing problem in thepediatric population. Incidence of first and second relapse of CDI in children is reportedto be 20% and 40-50% respectively after treatment with antibiotics (J Clin Gastroenterol2011). Fecal microbiota therapy (FMT) for RCDI in children has not been studied in detail.We report a series of 3 cases of RCDI in children who were successfully treated with FMT.Fecalmicrobiota analysis of patient-donor samples using 16S rRNA gene amplicon sequencingwas performed in the first patient-donor pair. Aim: To describe the clinical outcome andchanges in the microbiota associated with FMT for RCDI in children. Methods: FMT wasperformed in 3 pediatric patients (age range 1.7-17 years) with RCDI, from July 2011 toAugust 2012. CDI duration was .2 months (range 2.5-7 months) with 3 or more recurrencesfollowing appropriate antibiotic therapy. The FMT was administered via colonic route (270-350 cc of filtrate) in all 3 patients. The fecal sample donor was the mother of the child ineach case. Fecal samples were collected from the first patient-FMT donor pair, before FMTand after FMT. Total metagenomic DNA was isolated from these fecal samples and used for16S rRNA gene-specific PCR amplification and pooled amplicon pyrosequencing. Microbiotacompositions were studied using standard 16S rRNA analysis tools (CloVR-16S). Results:All 3 children had complete resolution of symptoms after FMT and a negative stool C difficiletoxin assay 3 months after FMT [Table 1]. Symptom improvement was noted within 2-4days in all cases. Mean duration of follow up was 9 months (range:3 to 16 months). Thesecond child had a stunted growth due to RCDI with weight , 25th percentile and height, 3rd percentile for age. After FMT he showed remarkable recovery with weight increasingto the 50th percentile and height at the 3rd percentile for age. Microbiota analysis of thefecal samples from the first child prior to FMT demonstrated alterations in the stool microbiotaas compared to the healthy adult donor. Comparison of fecal microbiota (weighted UniFrac)showed that healthy donor and post-FT patient samples were different from each other at1 month. Discussion: These results suggest that FMT is as effective as in adults for treatingRCDI in the pediatric population. While dysbiosis is identified in the RCDI patient whounderwent microbiota analysis, the level of dysbiosis is not as dramatic as seen in adultpatients involved in a similar study at our institution. FMT appears to lead to a significantchange in the fecal microbiome in children with RCDI; however, the post-FMT microbiotain the child studied was different when compared to the adult donor. This finding suggeststhat children may respond to adult donor microbiota in a different way than adult patients.Course of RCDI in studies children, attempted antibiotic treatment and patient responseto FMT.

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IL-10-Producing Mucosal B Cells Attenuate T Cell-Mediated Colitis ThroughInduction of Tr-1 CellsYoshiyuki Mishima, Bo Liu, Christpher Karp, Ryan B. Sartor

Background: The role of IL-10-producing B cells in inflammatory bowel diseases (IBD) ispoorly understood. Several studies suggested that B cell depletion might lead to developinghuman colitis (IBD 2007, Gut 2008). We hypothesize that intestinal B cells contribute tomucosal homeostasis and protection against IBD through IL-10 secretion. Methods: Wild-type (WT) or IL-10-/- splenic CD4+ T cells were co-transferred with purified splenic B cellsfrom WT or IL-10-/- mice into Rag2-/-IL-10-/- (DKO) mice. 6 weeks after co-transfer, thesemice were evaluated for colitis severity by histology (0: normal, 12: severe inflammation),cytokine secretion by colonic tissue explant (gut culture) and mesenteric lymph nodes (MLN)(MLN culture), and Foxp3 expression in MLN CD4+ T cells. To investigate suppressivemechanisms of B cells on bacteria-activated differentiation of Naïve T cells in vitro, WT orIL-10-/- B cells were co-cultured with CD25-CD4+ T cells from IL-10+/EGFP reporter miceand IL-10-/- antigen-presenting cells (APC) stimulated by cecal bacterial lysates (CBL). IL-10, IFNγ and IL-17a supernatant levels were measured by ELISA and IFN γ, IL-17a, Foxp3and GFP expression were assessed by FACS. Results: In vivo, WT CD4+ T cell recipientDKO mice that received co-transferred WT B cells developed less severe colitis than thosereceiving either IL-10-/- B cells or no B cells (histology 4.3±1.0, 7.2±1.1 and 7.6±0.7,p,0.02). Gut and MLN culture demonstrated that either spontaneous or bacteria-inducedIFNγ and IL-17a secretion was significantly lower and IL-10 levels were higher in DKOmice that received WT B cells than those receiving IL-10-/- B cells or no B cells. MLN CD4+

T cell Foxp3 expression was induced by co-transferring either WT B cells (10.9±1.0%,p,0.05) or IL-10-/- B cells (11.6±0.8%, p,0.05), compared to animals without B cells(7.4±1.2%). In contrast, all DKO mice with transferred IL-10-/-CD4+ T cells developed severecolitis with no evidence of suppression by WT or IL-10-/- B cells. In vitro, WT but not IL-10-/- B cells suppressed IFNγ and IL-17a production by CBL-stimulated CD4+ T cells. FACSdemonstrated that% of either CBL-stimulated IL-17a+ or IFNγ+ CD4+ T cells were significantlylower when co-cultured with WT but not IL-10-/- B cells. Interestingly, although both WT

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and IL-10-/- B cells induced Foxp3+CD4+ T cells, only WT B cells could induce GFP+IL-10-producing T regulatory cells (Tr-1 cells) (3.7±0.3% with WT B cells, 2.2±0.2% with IL-10-/- B cells, and 2.0±0.3% without B cells, p,0.01). Summary: WT but not IL-10-/- B cellsameliorate T cell-mediated colitis despite B cell induction of Foxp3+CD4+ cells being IL-10independent. IL-10-producing B cells may contribute to intestinal homeostasis by suppressingeffector T cells directly (by IL-10 secretion) and indirectly (by inducing IL-10-producingTr-1 cells).

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The UK Flexible Sigmoidoscopy Screening Trial: Uptake and Outcomes ofFirst Round Faecal Occult Blood Testing in the English NHS Bowel CancerScreening ProgrammeInes Kralj-Hans, Kate Wooldrage, Sue Moss, Julietta Patnick, Stephen W. Duffy, Wendy S.Atkin

Background: Flexible sigmoidoscopy (FS) screening is the only modality proven in randomi-sed controlled trials to reduce colorectal cancer incidence (Atkin et al., 2010; Segnan et al.,2011; Schoen et al., 2012). It is soon to be included in the NHS Bowel Cancer ScreeningProgramme (BCSP), which started in 2006 and currently offers biennial guaiac faecal occultblood test (FOBt) to all 60-74 year olds. A single FS will be offered at age 55 with FOBtscreening to continue from age 60 to 74. The outcomes of FOBt screening are used tomonitor the programme's performance as well as plan endoscopy and other resource usage.It is not known how prior FS exposure will impact on the uptake and outcomes of FOBtscreening. The UK Flexible Sigmoidoscopy Screening Trial (UKFSST) cohort comprised170000 individuals, one third of whom were randomly invited for a single FS at age 55-64 between 1994-8; the remainder had usual care. The trial cohort is a unique resourcewhich may provide valuable insights into what could be expected in subsequent FOBtscreening following exposure to FS. Methods: At the start of the BCSP in 2006, 119986trial participants in England were alive and in the eligible age range for bowel cancer screening.These participants were matched with the NHS BCSP database to identify individuals whowere offered FOBt between August 2006 and June 2011. The primary outcomes werecompletion of the test after the first invitation, FOBt positivity and positive predictive values(PPVs) in people completing their first FOBt. Results: 60917 UKFSST participants (40697in control and 20220 in intervention groups; 48% men in both groups) were invited tocomplete an FOBt at least once. The median age at first FOBt invitation was 69 years (IQR67-71). The median time since FS exposure to completion of the first FOBt was 11 years(IQR 10-12). FOBt uptake rates in the UKFSST cohort were high, positivity rates were low,and PPVs at diagnostic colonoscopy after a positive test were high (see Table). Comparedwith the usual care group, uptake and positivity rates were lower in the intervention group(71.78 vs. 70.28: p ,0.001 and 2.33 vs. 1.89: p=0.003, RR=0.81 (0.71-0.93) respectively)).PPVs were lower for cancer (12.18 vs. 10.84: p = 0.58) and advanced adenomas (33.23 vs.23.29; p = 0.004) after prior FS. Conclusions: This study provides the first comparison ofFOBt uptake and outcomes following prior FS. Participation in a FOBt screening programmeis high. Prior FS reduces FOBt uptake, positivity rates, and PPV for cancers and advancedadenomas, but the FOBt retains its high specificity. A limitation of our study is the longtime interval between FS and FOB testing.

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A Computational Method to Significantly Increase Early Detection Rate ofColorectal CancerYaron Kinar, Nir Kalkstein, Inbal Goldshtein, Gabriel Chodick, Varda Shalev

Background: Colorectal cancer (CRC) is among the most commonly diagnosed cancersworldwide. Although screening programs reduce incidence and mortality from CRC, compli-ance rates are sub-optimal. Thus, the vast majority of the population is not screened, with~60% of CRC cases detected only after regional or distal spread. Aim: To devise a computa-tional method that significantly increases early detection rate of CRC based solely on readilyavailable data, specifically, complete blood counts (CBC). Given the wide availability of CBCdata, such a method could dramatically increase screening rates. Method: We devised amachine learning method for predicting CRC status using only age, gender, and currentand past CBC values. Specifically, the method was developed using CBC data collected over9 years from more than 700,000 individuals (men and women) older than 40Y in theMaccabi Healthcare Services, Israel. Of these, over 3000 were diagnosed with CRC. Toevaluate performance, we used a blinded hold-out validation scheme, whereby we developedour method on a randomly selected 80% of the data, and then tested its ability to predict

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