Cumulative exposure to immunomodulators increases risk of cervical neoplasia in women with inflammatory bowel disease.

BACKGROUND: Women with inflammatory bowel disease (IBD) are at increased risk of high-grade cervical intraepithelial neoplasia and cervical cancer (CIN2+). AIM: To assess the association between cumulative exposure to immunomodulators (IM) and biologic agents (BIO) for IBD and CIN2+ METHODS: Adult women diagnosed with IBD before December 31st 2016 in the Dutch IBD biobank with available cervical records in the nationwide cytopathology database were identified. CIN2+ incidence rates in IM- (i.e., thiopurines, methotrexate, tacrolimus and cyclosporine) and BIO- (anti-tumour necrosis factor, vedolizumab and ustekinumab) exposed patients were compared to unexposed patients and risk factors were assessed. Cumulative exposure to immunosuppressive drugs was evaluated in extended time-dependent Cox-regression models. RESULTS: The study cohort comprised 1981 women with IBD: 99 (5%) developed CIN2+ during median follow-up of 17.2 years [IQR 14.6]. In total, 1305 (66%) women were exposed to immunosuppressive drugs (IM 58%, BIO 40%, IM and BIO 33%). CIN2+ risk increased per year of exposure to IM (HR 1.16, 95% CI 1.08-1.25). No association was observed between cumulative exposure to BIO or both BIO and IM and CIN2+. In multivariate analysis, smoking (HR 2.73, 95%CI 1.77-4.37) and 5-yearly screening frequency (HR 1.74, 95% CI 1.33-2.27) were also risk factors for CIN2+ detection. CONCLUSION: Cumulative exposure to IM is associated with increased risk of CIN2+ in women with IBD. In addition to active counselling of women with IBD to participate in cervical screening programs, further assessment of the benefit of intensified screening of women with IBD on long-term IM exposure is warranted.

Platelet-Rich stroma from Crohn's disease patients for treatment of perianal fistula shows a higher myeloid cell profile compared to non-IBD controls.

BACKGROUND: New cell-based therapies are under investigation to improve perianal fistulizing Crohn's disease (pCD) healing. Autologous stromal vascular fraction combined with platelet-rich plasma (referred to as platelet-rich stroma [PRS]) is a new adipose-derived stromal therapy. The effect of Crohn's disease (CD) on adipose tissue, and adipose-derived therapies, is largely unknown. We characterized the cellular composition of subcutaneous lipoaspirate and PRS of pCD patients and non-Inflammatory Bowel Disease (IBD) controls. METHODS: Consecutive pCD patients (≥18 years) and non-IBD controls, who underwent liposuction for the purpose of autologous PRS therapy, were included (October 2020 and March 2021). Mechanically fractionated lipoaspirate and the combined PRS product were analyzed for cell surface marker expression using fluorescence-activated cell sorting analysis. RESULTS: Twenty-three patients (37.8 [IQR 30.7-45.0] years; 9 [39.1 %] male; 11CD patients) were included. Similar total number of cells were found in CD and non-IBD lipoaspirate (CD 8.23 ± 1.62*105 cells/mL versus non-IBD 12.20 ± 3.39*105). Presence of stromal cells, endothelial like cells, immune cells, T-cells, myeloid cells and M2/M1 macrophage ratio were similar in CD and non-IBD lipoaspirate. In PRS samples, more cells/mL were seen in CD patients (P = 0.030). Myeloid cells were more abundant in CD PRS samples (P = 0.007), and appeared to have a higher regulatory M2/M1 ratio. Interdonor variation was observed between lipoaspirate and PRS samples. CONCLUSIONS: The composition of CD and non-IBD lipoaspirate were found to be similar and interdonor variation was observed. However, PRS from CD patients showed more myeloid cells with a regulatory phenotype. Crohn's disease does not appear to alter the immunological composition of adipose-derived products.

Hepatitis E infection with a benign course during vedolizumab treatment for Crohn's disease: A case report.

We present a 49 year old female patient with Crohn's disease (CD) in remission on vedolizumab therapy who experienced a symptomatic, though benign, course of acute hepatitis E. Routine blood tests showed substantial elevation of liver enzymes and polymerase chain reaction (PCR) testing confirmed hepatitis E virus (HEV) infection. Vedolizumab therapy was paused, liver enzymes improved three weeks after infection and normalized after six months. The patient recovered completely from mild symptoms. This case shows that hepatitis E is a potential cause of acute hepatitis during vedolizumab therapy, and in this case the infection has run a benign course.

The diagnosis and management of CMV colitis in IBD patients shows high practice variation: a national survey among gastroenterologists.

BACKGROUND: Clinical guidelines on cytomegalovirus (CMV) colitis in inflammatory bowel disease (IBD) are hampered by the low quality of evidence. In this study, we aim to explore the attitude and management of CMV colitis in IBD among gastroenterologists. METHODS: A web-based survey was distributed to adult and pediatric gastroenterologists and trainees in academic and general hospitals in the Netherlands. The survey comprised data collection on respondents' demographics, attitudes towards the importance of CMV infection in IBD on a visual analogue scale (from 0 to 100), and diagnostic and therapeutic strategies. RESULTS: A total of 73/131 invited respondents from 32 hospitals completed the survey (response rate of 56%). The importance of CMV infection was scored at a median 74/100. Respondents indicated CMV testing as appropriate in the clinical setting of steroid-refractory colitis (69% of respondents), hospitalized patients with active colitis (64%), immunomodulator or biological refractory colitis (55%) and active colitis irrespective of medication use (14%). CMV diagnostics include histology of colonic biopsies (88% of respondents), tissue CMV PCR (43%), serum CMV PCR (60%), CMV serology (25%) and fecal CMV PCR (4%). 82% of respondents start antiviral therapy after a positive CMV test on colonic biopsies (histology or PCR). CONCLUSIONS: Most Dutch gastroenterologists acknowledge the importance of CMV colitis in IBD. Strategies vary greatly with regard to the indication for testing and diagnostic method, as well as indication for the start of antiviral therapy. These findings underline the need for pragmatic clinical studies on different management strategies, in order to reduce practice variation and improve the quality of care. Summary of the established knowledge on this subject:The clinical significance of CMV-associated colitis in IBD remains a matter of debateRecommendations regarding CMV colitis in current international guidelines are based on low to moderate evidence levels and different diagnostic strategies are proposed What are the significant and/or new findings of this study?We show that there is a high practice variation of diagnosis and management of CMV colitis in IBD amongst adult and pediatric gastroenterologistsThis study underlined the need for pragmatic studies and guidelines on different management strategies including cut-off values to start therapy.

Efficacy and safety of autologous adipose-derived stromal vascular fraction enriched with platelet-rich plasma in flap repair of transsphincteric cryptoglandular fistulas.

BACKGROUND: Transanal advancement flap repair of transsphincteric fistulas is a sphincter-preserving procedure, which frequently fails, probably due to ongoing inflammation in the remaining fistula tract. Adipose-derived stromal vascular fraction (SVF) has immunomodulatory properties promoting wound healing and suppressing inflammation. Platelet-rich plasma (PRP) reinforces this biological effect. The aim of this study was to evaluate the efficacy and safety of autologous adipose-derived SVF enriched with PRP in flap repair of transsphincteric cryptoglandular fistulas. METHODS: A prospective cohort study was conducted including consecutive patients with transsphincteric cryptoglandular fistula in a tertiary referral center. During flap repair, SVF was obtained by lipoharvesting and mechanical fractionation of adipose tissue and combined with PRP was injected around the internal opening and into the fistulous wall. Endpoints were fistula healing at clinical examination and fistula closure on postoperative magnetic resonance imaging (MRI). Adverse events were documented. RESULTS: Forty-five patients with transsphincteric cryptoglandular fistula were included (29 males, median age 44 years [range 36-53 years]). In the total study population, primary fistula healing was observed in 38 patients (84%). Among the 42 patients with intestinal continuity at time of surgery, primary fistula healing was observed in 35 patients (84%). In one patient, the fistula recurred, resulting in a long-term healing rate of 82%. MRI, performed in 37 patients, revealed complete closure of the fistula tract in 33 (89.2%). In the other patients, the tract was almost completely obliterated by scar tissue. During follow-up, none of these patients showed clinical signs of recurrence. The postoperative course was uneventful, except for three cases; venous thromboembolism in one patient and bleeding under the flap, necessitating intervention in two patients. CONCLUSIONS: Addition of autologous SVF enriched with PRP during flap repair is feasible, safe and might improve outcomes in patients with a transsphincteric cryptoglandular fistula. TRIAL REGISTRATION: Dutch Trial Register, Trial Number: NL8416, https://www.trialregister.nl/.

A first pregnancy seems associated with a positive effect on the course of inflammatory bowel disease: data from a prospective pregnancy cohort.

Objectives: The effect of pregnaSSncy on the course of inflammatory bowel disease (IBD) remains controversial. We aimed to describe the disease course before and after a first pregnancy in IBD patients.Methods: We analyzed data from a prospectively followed-up pregnancy cohort (minimal follow-up of 7 years), with clinical, biochemical and endoscopic characteristics obtained pre-pregnancy, during pregnancy and post-pregnancy. Possible factors associated with relapse (disease activity during pregnancy, maternal age, smoking, alcohol use, pre-pregnancy BMI, mode of delivery, thiopurine use during pregnancy, biological use during pregnancy, combination of thiopurine and biological use during pregnancy, breastfeeding, IBD diagnosis, endoscopic scores) were scored.Results: One hundred twenty six patients (95 Crohn's Disease [CD; 75%] and 31 Ulcerative Colitis/IBD unclassified [UC/IBD-U; 25%]) were enrolled, with one hundred pregnancies occurring in 100 primigravida patients. All pregnancies resulted in live birth. Twenty patients (20%) had a relapse during pregnancy. The median number of relapses/patient/year was 0.25 (IQR 0.5) and 0 (IQR 0.43) respectively before and after pregnancy (p = .00). For CD patients the median relapses/person/year was 0.25 (IQR 0.5) before and 0 (IQR 0.25) after delivery (p = .00), for UC/IBD-U patients there was no significant difference. In the post-partum period more UC patients relapsed compared to CD patients (68% vs 30.7%, p = .01). Seven-year IBD-course was unchanged in the 26 women who did not become pregnant.Conclusion: In this prospective observational cohort study, we found a lower rate of relapses in the 4 years after delivery compared to the 3 years prior to a first pregnancy. Post-partum, more UC patients experienced a relapse compared to CD patients.

Increased Risk of High-grade Cervical Neoplasia in Women with Inflammatory Bowel Disease: A Case-controlled Cohort Study.

BACKGROUND AND AIMS: Women with inflammatory bowel disease [IBD] may be at higher risk for cervical intraepithelial neoplasia [CIN]. However, data are conflicting. The aim of this study was to assess the risk of high-grade dysplasia and cancer [CIN2+] in IBD women and identify risk factors. METHODS: Clinical data from adult IBD women in a multicentre Dutch IBD prospective cohort [PSI] from 2007 onwards were linked to cervical cytology and histology records from the Dutch nationwide cytology and pathology database [PALGA], from 2000 to 2016. Patients were frequency-matched 1:4 to a general population cohort. Standardised detection rates [SDR] were calculated for CIN2+. Longitudinal data were assessed to calculate CIN2+ risk during follow-up using incidence rate ratios [IRR] and risk factors were identified in multivariable analysis. RESULTS: Cervical records were available from 2098 IBD women [77%] and 8379 in the matched cohort; median follow-up was 13 years. CIN2+ detection rate was higher in the IBD cohort than in the matched cohort (SDR 1.27, 95% confidence interval [CI] 1.05-1.52). Women with IBD had an increased risk of CIN2+ [IRR 1.66, 95% CI 1.21-2.25] and persistent or recurrent CIN during follow-up (odds ratio [OR] 1.89, 95% CI 1.06-3.38). Risk factors for CIN2+ in IBD women were smoking and disease location (ileocolonic [L3] or upper gastrointestinal [GI] [L4]). CIN2+ risk was not associated with exposure to immunosuppressants. CONCLUSIONS: Women with IBD are at increased risk for CIN2+ lesions. These results underline the importance of human papillomavirus [HPV] vaccination and adherence to cervical cancer screening guidelines in IBD women, regardless of exposure to immunosuppressants.

Genetic Risk Scores Identify Genetic Aetiology of Inflammatory Bowel Disease Phenotypes.

BACKGROUND AND AIMS: Inflammatory bowel disease [IBD] phenotypes are very heterogeneous between patients, and current clinical and molecular classifications do not accurately predict the course that IBD will take over time. Genetic determinants of disease phenotypes remain largely unknown but could aid drug development and allow for personalised management. We used genetic risk scores [GRS] to disentangle the genetic contributions to IBD phenotypes. METHODS: Clinical characteristics and imputed genome-wide genetic array data of patients with IBD were obtained from two independent cohorts [cohort A, n = 1097; cohort B, n = 2156]. Genetic risk scoring [GRS] was used to assess genetic aetiology shared across traits and IBD phenotypes. Significant GRS-phenotype (false-discovery rate [FDR] corrected p <0.05) associations identified in cohort A were put forward for replication in cohort B. RESULTS: Crohn's disease [CD] GRS were associated with fibrostenotic CD [R2 = 7.4%, FDR = 0.02] and ileocaecal resection [R2 = 4.1%, FDR = 1.6E-03], and this remained significant after correcting for previously identified clinical and genetic risk factors. Ulcerative colitis [UC] GRS [R2 = 7.1%, FDR = 0.02] and primary sclerosing cholangitis [PSC] GRS [R2 = 3.6%, FDR = 0.03] were associated with colonic CD, and these two associations were largely driven by genetic variation in MHC. We also observed pleiotropy between PSC genetic risk and smoking behaviour [R2 = 1.7%, FDR = 0.04]. CONCLUSIONS: Patients with a higher genetic burden of CD are more likely to develop fibrostenotic disease and undergo ileocaecal resection, whereas colonic CD shares genetic aetiology with PSC and UC that is largely driven by variation in MHC. These results further our understanding of specific IBD phenotypes.

Management of Pregnant Inflammatory Bowel Disease Patients During the COVID-19 Pandemic.

The rapid emergence of the novel coronavirus [SARS-CoV2] and the coronavirus disease 2019 [COVID-19] has caused significant global morbidity and mortality. This is particularly concerning for vulnerable groups such as pregnant women with inflammatory bowel disease [IBD]. Care for pregnant IBD patients in itself is a complex issue because of the delicate balance between controlling maternal IBD as well as promoting the health of the unborn child. This often requires continued immunosuppressive maintenance medication or the introduction of new IBD medication during pregnancy. The current global COVID-19 pandemic creates an additional challenge in the management of pregnant IBD patients. In this paper we aimed to answer relevant questions that can be encountered in daily clinical practice when caring for pregnant women with IBD during the current COVID-19 pandemic. PODCAST: This article has an associated podcast which can be accessed at https://academic.oup.com/ecco-jcc/pages/podcast.

Inflammatory Bowel Disease Management During the COVID-19 Outbreak: The Ten Do's and Don'ts from the ECCO-COVID Taskforce.

Our knowledge of COVID-19 is changing and evolving rapidly, with novel insights and recommendations, almost on a daily basis. It behooves the medical community to provide updated information on a regular basis, on best practice to facilitate optimal care of infected patients and on appropriate advice for the general population. This is particularly important in the case of patients with chronic conditions, such as inflammatory bowel disease [IBD]. In this review, we have compiled existing evidence on the impact of COVID-19 in IBD patients and provide guidance on the most appropriate care to adopt during the pandemic. Our review highlights that IBD, per se, is not a risk factor for COVID-19. However, all IBD patients with symptoms should be tested for SARS-CoV-2 and the procedures for disease management should be carefully adapted: [i] in SARS-CoV-2-positive IBD patients, medical treatments should be re-evaluated [with a particular focus on corticosteroids] always with the purpose of treating active disease and maintaining remission; [ii] non-urgent surgeries and endoscopic procedures should be postponed for all patients; [iii] online consultancy should be implemented; and [iv] hospitalization and surgery should be limited to life-threatening situations.

Effect of biologicals and JAK inhibitors during pregnancy on health-related outcomes in children of women with inflammatory bowel disease.

Current guidelines advise to maintain immunomodulators and biologicals in pregnant patients because relapse of inflammatory bowel is associated with unfavourable pregnancy outcome. With the exception of Methotrexate, IBD therapy seems not to be related to an increase of congenital malformations or infections requiring hospitalisation of the babies, although the effect the on the developing immune system of the exposed infants remains unknown. In this review we will focus on the effect of IBD drugs on health-related outcomes in children taking into account possible long-term effects of biologicals and immunomodulators, which are transferred across the placenta.

Lengthening adalimumab dosing interval in quiescent Crohn's disease patients: protocol for the pragmatic randomised non-inferiority LADI study.

INTRODUCTION: Adalimumab is effective for maintenance of remission in patients with Crohn's disease (CD) at a dose of 40 mg subcutaneously every 2 weeks. However, adalimumab is associated with (long-term) adverse events and is costly. The aim of this study is to demonstrate non-inferiority and cost-effectiveness of disease activity guided adalimumab interval lengthening compared to standard dosing of every other week (EOW). METHODS AND ANALYSIS: The Lengthening Adalimumab Dosing Interval (LADI) study is a pragmatic, multicentre, open label, randomised controlled non-inferiority trial. Non-inferiority is reached if the difference in cumulative incidence of persistent (>8 weeks) flares does not exceed the non-inferiority margin of 15%. 174 CD patients on adalimumab maintenance therapy in long-term (>9 months) clinical and biochemical remission will be included (C-reactive protein (CRP) <10 mg/L, faecal calprotectin (FC) <150 µg/g, Harvey-Bradshaw Index (HBI) <5). Patients will be randomised 2:1 into the intervention (adalimumab interval lengthening) or control group (adalimumab EOW). The intervention group will lengthen the adalimumab administration interval to every 3 weeks, and after 24 weeks to every 4 weeks. Clinical and biochemical disease activity will be monitored every 12 weeks by physician global assessment, HBI, CRP and FC. In case of disease flare, dosing will be increased. A flare is defined as two of three of the following criteria; FC>250 µg/g, CRP≥10 mg/l, HBI≥5. Secondary outcomes include cumulative incidence of transient flares, adverse events, predictors for successful dose reduction and cost-effectiveness. ETHICS AND DISSEMINATION: The study is approved by the Medical Ethics Committee Arnhem-Nijmegen, the Netherlands (registration number NL58948.091.16). Results will be published in peer-reviewed journals and presented at international conferences. TRIAL REGISTRATION NUMBERS: EudraCT registry (2016-003321-42); Clinicaltrials.gov registry (NCT03172377); Dutch trial registry (NTRID6417).

The pre- and post-authorisation data published by the European medicines agency on the use of biologics during pregnancy and lactation.

AIMS: The effects of biologics on reproduction/lactation are mostly unknown although many patients that receive biologics are women of reproductive age. The first objective of this study was to investigate the publicly available data on pregnancy/lactation before and after marketing authorization in Europe of biologics for the indications of rheumatologic inflammatory autoimmune diseases and inflammatory bowel disease. Secondary objectives included the assessment of the clinical relevance of the provided data and comparison of initial and post-authorization data. METHODS: Initial and post-authorization data were extracted from the European Public Assessment Reports and the latest versions of Summary of Product Characteristics using publicly available documents on the European Medicines Agency's website. Four sections were categorized regarding pregnancy outcomes: pre-clinical/animal studies, human female fertility, pregnancy-related outcomes and congenital malformations in the human fetus. Three sections were categorized regarding lactation outcomes: pre-clinical/animal studies, excretion in human breast milk and absorption in children through breastfeeding. The clinical applicability of each category was scored by specified criteria, based on scientific literature, and further as defined by the authors. RESULTS: For the 16 included biologics, post-authorization data were delivered only for adalimumab, certolizumab pegol, etanercept and infliximab. For the 12 remaining biologics limited data on pregnancy and lactation during the post-marketing period of 2-21 years were available. CONCLUSIONS: In this article several suggestions are provided for improving a multidisciplinary approach to these issues. The initiation of suitable registries by marketing authorization holders and data transparency for clinicians and academics are highly endorsed.

Clinical and endoscopic complications of Epstein-Barr virus in inflammatory bowel disease: an illustrative case series.

BACKGROUND AND AIM: Epstein-Barr virus (EBV) is a proposed trigger in the etiopathogenesis of inflammatory bowel disease (IBD) and is associated with lymphoproliferative diseases. Nevertheless, testing for EBV DNA in the intestinal mucosa and screening for EBV infection before initiation of a drug therapy are not routinely performed. The aim of this article is to increase awareness of the relevance of EBV infection in specific clinical situations. METHODS: In this short communication, we describe the disease course of three IBD patients with EBV infection, varying from EBV reactivation during disease flare up to a trigger of EBV-related mucocutaneous ulcer (EBV-MCU) and haemophagocytic lymphohistiocytosis (HLH). RESULTS: Our first patient was diagnosed with EBV reactivation-associated severe colitis and showed a rapid clinical improvement after induction therapy with infliximab and azathioprine. Without antiviral treatment, the patient remained in complete remission and no complications of EBV were seen. After diagnosing EBV-MCU in the second patient, immunosuppressive medication was discontinued and four infusions of rituximab resulted in a rapid clinical recovery and eventually complete response. After discontinuation of the immunosuppression in our last patient with haemophagocytic lymphohistiocytosis, treatment with a combination of corticosteroid and antiviral therapy resulted in a complete recovery over a time span of several weeks. CONCLUSION: EBV infection has a wide variety of potentially life-threatening clinical manifestations in IBD patients. Testing for EBV in case of a flare up and screening for EBV before the start of immunosuppressive therapy will create awareness for EBV-related symptoms or complications during follow-up.

Genetic polymorphism in ATG16L1 gene is associated with adalimumab use in inflammatory bowel disease.

BACKGROUND: The role of single nucleotide polymorphisms (SNPs) associated with inflammatory bowel disease (IBD) is gaining interest. With the advent of novel therapies, personalized treatment in IBD is a future goal. We wondered whether IBD-associated SNPs are able to predict response to anti-TNFα treatment. METHODS: Data on treatment use and primary response, loss of response and side effects to anti-TNFα treatments were retrieved for 570 IBD patients. rs13361189 (IRGM), rs10210302 (ATG16L1), rs2066844, rs2066845, rs2066847 (NOD2), rs35873774 (XBP1), rs11175593 (LRRK2), rs11465804 (IL23R), rs2301436 (CCR6), rs744166 (STAT3) and rs4821544 (NCF4) SNP status were determined. RESULTS: No associations were found between genetic variants of the LRRK2, CCR6, IL23R and NCF4 genes and response to anti-TNFα. For NOD2 and XBP1 associations were found, however, these associations were not strong enough to survive multiple testing corrections. Strikingly, patients carrying the ATG16L1 T300A variant were more likely to be treated with adalimumab, even after correction for disease phenotype, disease behavior and age (p = 0.004, OR 2.8, CI 1.6-5.0). CONCLUSIONS: Genetic polymorphisms in the known IBD-associated gene ATG16L1 correlate with requirement of treatment, suggesting a different IBD disease phenotype in these patients. Further investigation will need to elucidate the implications of these findings and identify the underlying disease characteristics.

The Impact of Ethnicity and Country of Birth on Inflammatory Bowel Disease Phenotype: a Prospective Cohort Study.

BACKGROUND AND AIMS: The number of patients with inflammatory bowel disease [IBD], of non-Caucasian descent in Western Europe, is increasing. We aimed to explore the impact of ethnicity and country of birth on IBD phenotype. METHODS: IBD patients treated in the eight University Medical Centers in The Netherlands [Dutch IBD Biobank] were divided into two groups according to their ethnicity: 1] Caucasian patients of Western and Central European descent [CEU]; and 2] patients of non-Caucasian descent [non-CEU]. The non-CEU group was subdivided according to country of birth, into: born in The Netherlands or Western Europe [non-CEU European born]; or born outside Western-Europe who migrated to The Netherlands [non-CEU non-European born]. Both comparisons were analysed for phenotype differences [by chi-square test]. RESULTS: The Dutch IBD Biobank included 2921 CEU patients and 233 non-CEU patients. Non-CEU Crohn's disease [CD] patients more often had upper gastro-intestinal disease [16% vs 8%, p = 0.001] and anal stenosis [10% vs 4%, p = 0.002] than CEU CD patients. The use of anti-tumour necrosis factor [TNF] agents and immunomodulators was higher in non-CEU IBD patients than in CEU IBD patients [45% vs 38%, p = 0.042] and [77% vs 66%, p = 0.001], respectively. Non-CEU IBD patients born in Europe [n = 116] were diagnosed at a lower age than non-CEU IBD patients born outside Europe [n = 115] [at 22.7 vs 28.9 years old, p < 0.001]. CONCLUSION: Non-Caucasians had more severe disease behaviour than Caucasians. Non-CEU patients born in Europe were diagnosed at a lower age with IBD than those born outside Europe who migrated to The Netherlands.

The ATG16L1 risk allele associated with Crohn's disease results in a Rac1-dependent defect in dendritic cell migration that is corrected by thiopurines.

Thiopurines are commonly used drugs in the therapy of Crohn's disease, but unfortunately only show a 30% response rate. The biological basis for the thiopurine response is unclear, thus hampering patient selection prior to treatment. A genetic risk factor associated specifically with Crohn's disease is a variant in ATG16L1 that reduces autophagy. We have previously shown that autophagy is involved in dendritic cell (DC)-T-cell interactions and cytoskeletal regulation. Here we further investigated the role of autophagy in DC cytoskeletal modulation and cellular trafficking. Autophagy-deficient DC displayed loss of filopodia, altered podosome distribution, and increased membrane ruffling, all consistent with increased cellular adhesion. Consequently, autophagy-deficient DC showed reduced migration. The cytoskeletal aberrations were mediated through hyperactivation of Rac1, a known thiopurine target. Indeed thiopurines restored the migratory defects in autophagy-deficient DC. Clinically, the ATG16L1 risk variant associated with increased response to thiopurine treatment in patients with Crohn's disease but not ulcerative colitis. These results suggest that the association between ATG16L1 and Crohn's disease is mediated at least in part through Rac1 hyperactivation and subsequent defective DC migration. As this phenotype can be corrected using thiopurines, ATG16L1 genotyping may be useful in the identification of patients that will benefit most from thiopurine treatment.