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Colorectal cancer (CRC) is among the most frequent forms of cancer, and new strategies for its prevention and therapy are urgently needed

Inflammatory bowel disease is the result of an inappropriate immune response to environmental factors in a genetically susceptible host. The intestinal microbiota has been considered one of the key environmental factors in this disease process, and early influences on the structure of the intestine’s bacterial communities may lead to a dysbiotic state. The complicated relationship between dysbiosis and the developing host immune system, including the innate and adaptive immune systems as well as the intestinal epithelial interface, can have profound effects on the health and disease of the host. Therapies targeted at the gut microbiota continue to be investigated as potential interventions for inflammatory bowel disease.

Background Children with inflammatory bowel disease [IBD] are disproportionally affected by recurrent Clostridioides difficile infection [rCDI]. Although faecal microbiota transplantation [FMT] has been used with good efficacy in adults with IBD, little is known about outcomes associated with FMT in paediatric IBD. Methods We performed a retrospective review of FMT at 20 paediatric centres in the USA from March 2012 to March 2020. Children with and without IBD were compared with determined differences in the efficacy of FMT for rCDI. In addition, children with IBD with and without a successful outcome were compared with determined predictors of success. Safety data and IBD-specific outcomes were obtained. Results A total of 396 paediatric patients, including 148 with IBD, were included. Children with IBD were no less likely to have a successful first FMT then the non-IBD affected cohort [76% vs 81%, p = 0.17]. Among children with IBD, patients were more likely to have a successful FMT if they received FMT with fresh stool [p = 0.03], were without diarrhoea prior to FMT [p = 0.03], or had a shorter time from rCDI diagnosis until FMT [p = 0.04]. Children with a failed FMT were more likely to have clinically active IBD post-FMT [p = 0.002] and 19 [13%] patients had an IBD-related hospitalisation in the 3-month follow-up. Conclusions Based on the findings from this large US multicentre cohort, the efficacy of FMT for the treatment of rCDI did not differ in children with IBD. Failed FMT among children with IBD was possibly related to the presence of clinically active IBD.

Clostridioides difficile infection (CDI) in children with inflammatory bowel disease (IBD) can present and manifest differently from the general population with CDI, and it can worsen the underlying disease course. Furthermore, current clinical assays used to test for CDI do not accurately distinguish between true CDI or colonization. This uncertainty leads to difficulty in identifying the etiology and therapy for symptomatic patients with IBD. Improved diagnostic tests, biomarkers, and safe and effective treatment options are greatly needed for this vulnerable population.

Objectives Very early-onset inflammatory bowel disease arises in children less than six years old, a critical time for immunologic development and maturation of the intestinal microbiome. Non-conventional lymphocytes, defined here as mucosal-associated invariant T cells and innate lymphocytes, require microbial products for either development or expansion, aspects that could be altered in very early-onset inflammatory bowel disease. Our objective was to define conventional leukocyte and non-conventional lymphocyte populations in controls and patients using multiparameter flow cytometry to test the hypothesis that their frequencies would be altered in a chronic inflammatory state associated with significant dysbiosis. Methods Multiparameter flow cytometry was used in a control cohort of 105 subjects to define age-effects, not previously comprehensively examined for these cell types in humans. Differences were defined between 263 unique age-matched patients with very early-onset inflammatory bowel disease and 105 controls using Student's t test. Subjects were divided into two age groups at the time of sampling to control for age-related changes in immune composition. Results Intermediate monocytes were consistently decreased in patients with VEO-IBD compared to controls. Mucosal-associated invariant T cells were significantly lower in patients with long-standing disease. Levels were less than half of those seen in the age-matched control cohort. The innate lymphoid cells type 2 population was expanded in the youngest patients. Conclusions Mucosal-associated invariant T cells are diminished years after presentation with inflammatory bowel disease. This durable effect of early life intestinal inflammation may have long term consequences. Diminished mucosal-associated invariant T cells could impact host defense of intestinal infections.

Background and Aims Dysbiosis of the gut microbiota is a well-known correlate of the pathogenesis of inflammatory bowel disease [IBD]. However, few studies have examined the microbiome in very early-onset [VEO] IBD, which is defined as onset of IBD before 6 years of age. Here we focus on the viral portion of the microbiome—the virome—to assess possible viral associations with disease processes, reasoning that any viruses potentially associated with IBD might grow more robustly in younger subjects, and so be more detectable. Methods Virus-like particles [VLPs] were purified from stool samples collected from patients with VEO-IBD [n = 54] and healthy controls [n = 23], and characterized by DNA and RNA sequencing and VLP particle counts. Results The total number of VLPs was not significantly different between VEO-IBD and healthy controls. For bacterial viruses, the VEO-IBD subjects were found to have a higher ratio of Caudovirales vs to Microviridae compared to healthy controls. An increase in Caudovirales was also associated with immunosuppressive therapy. For viruses infecting human cells, Anelloviridae showed higher prevalence in VEO-IBD compared to healthy controls. Within the VEO-IBD group, higher levels of Anelloviridae DNA were also positively associated with immunosuppressive treatment. To search for new viruses, short sequences enriched in VEO-IBD samples were identified, and some could be validated in an independent cohort, although none was clearly viral; this provides sequence tags to interrogate in future studies. Conclusions These data thus document perturbations to normal viral populations associated with VEO-IBD, and provide a biomarker—Anelloviridae DNA levels—potentially useful for reporting the effectiveness of immunosuppression.

The rate of pediatric inflammatory bowel disease (IBD) has been increasing over the last decade and this increase has occurred most rapidly in the youngest children diagnosed

Very early-onset inflammatory bowel disease (VEO-IBD), IBD diagnosed in children younger than 6 years old, is phenotypically and genetically distinct from older onset IBD. Monogenic and digenic causative defects, particularly in primary immunodeficiency and intestinal epithelial barrier genes, have been identified in a subset of patients with VEO-IBD allowing for targeted therapies and improved outcomes. However, these findings are the minority, thus strategies to correctly diagnose patients, including identification of specific histopathologic findings with correlating clinical and laboratory features may provide critical and necessary insight into mechanisms of disease pathogenesis and subsequent therapeutic options. In this article, we review the pathologic findings seen in patients with VEO-IBD and outline a pattern-based approach to diagnosis using examples from primary immunodeficiencies with gastrointestinal manifestations.

Inflammatory bowel disease (IBD) is characterized by inappropriate immune responses to the microbiota in genetically susceptible hosts, but little is known about the pathways that link individual g...

Introduction The impact of the 2019 US Food and Drug Administration safety alert involving transmission of multidrug resistant organisms through fecal microbiota transplantation (FMT), and the COVID-19 pandemic on the use of FMT in children, is unknown. Methods A survey of pediatric gastroenterologists performing FMT for Clostridioides difficile infection was conducted. Results Of 36 respondents, 17 (47%) and 30 (83%) changed their FMT practices related to the US Food and Drug Administration safety alert and COVID-19 pandemic, respectively, with 22 (61%) of programs halted. Discussion The US Food and Drug Administration safety alert and COVID-19 pandemic have substantially influenced the availability and access of FMT for children.

Very early onset inflammatory bowel disease (VEO-IBD) represents a diagnostic and treatment challenge. Here we present a case of VEO-IBD secondary to a mutation in BIRC4 gene, which encodes X-linked inhibitor of apoptosis protein (XIAP), in a 17-month-old boy with severe failure to thrive, intractable diarrhea, and hepatosplenomegaly. Endoscopy and histology identified only mild duodenitis and ileitis, but severe pancolitis with crypt abscesses and epithelium apoptosis. Minimal improvement in symptoms was achieved with total parenteral nutrition (TPN), intravenous (IV) corticosteroids, and tacrolimus, whereas induction and maintenance therapy with adalimumab led to complete remission. After 6 months, the patient developed hemophagocytic lymphohistiocytosis and eventually died due to multisystem organ failure. A review of the literature revealed that some patients with VEO-IBD secondary to XIAP deficiency develop symptoms that are refractory to medical and surgical management, while initial reports suggest that allogeneic hematopoietic stem cell transplantation (HSCT), with reduced intensity conditioning, can successfully induce long-lasting remission and may even be curative. We propose that in patients with XIAP deficiency a constellation of symptoms including colitis at an early age, severe failure to thrive, and splenomegaly/hepatosplenomegaly can identify a subgroup of patients at high risk of experiencing medically refractory IBD phenotype and increased mortality. Hematopoietic stem cell transplant should be considered early in these high-risk patients, as it may resolve both their intestinal inflammation and a risk of developing life threatening hemophagocytic lymphohistiocytosis .

The pleiotropic actions of interleukin-2 (IL-2) are essential for regulation of immune responses and maintenance of immune tolerance. The IL-2 receptor (IL-2R) is composed of IL-2Rα, IL-2Rβ, and IL-2Rγ subunits, with defects in IL-2Rα and IL-2Rγ and their downstream signaling effectors resulting in known primary immunodeficiency disorders. Here, we report the first human defect in IL-2Rβ, occurring in two infant siblings with a homozygous IL2RB mutation in the WSXWS motif, manifesting as multisystem autoimmunity and susceptibility to CMV infection. The hypomorphic mutation results in diminished IL-2Rβ surface expression and dysregulated IL-2/15 signaling, with an anticipated reduction in regulatory T cells. However, in contrast to the IL-2Rβ−/− animal model, which lacks NK cells, these siblings demonstrate an expansion of NK cells, particularly the CD56bright subset, and a lack of terminally differentiated NK cells. Thus, the early-onset autoimmunity and immunodeficiency are linked to functional deficits arising from altered IL-2Rβ expression and signaling in T and NK cells.

Purpose of Review Inflammatory bowel disease (IBD) is a multifactorial disease caused by dysregulated immune responses to commensal or pathogenic intestinal microbes, resulting in chronic intestinal inflammation. However, a subset of patients with IBD diagnosed Recent Findings VEO-IBD is increasing in incidence and is associated with more severe disease, aggressive progression, and poor response to most conventional therapies. This article will review some of the genetic findings in this population and the subsequent impact on therapy, with targeted approaches. Summary Children with VEO-IBD may present with a different phenotype and more severe disease than older children and adults. An integrated approach combining genetics, immunology, and traditional IBD evaluations can lead to the identification of causal defects that directly impact management. These strategies can also be employed in older onset refractory IBD.

Objective Children with very early-onset inflammatory bowel disease (VEO-IBD) represent a distinct group of patients with IBD with unique phenotypic and genetic characteristics; however, they are frequently omitted from psychosocial research. This study used a novel, brief measure of pediatric global health to assess (1) overall health-related quality of life (HRQOL) in children with VEO-IBD, (2) HRQOL compared to healthy children, and (3) whether gastrointestinal symptoms account for the differences in HRQOL between these groups. Methods Caregivers of 51 children with VEO-IBD (Mage = 4.26 years, 75% male) and 54 healthy children (Mage = 3.50 years, 54% male) completed the PROMIS Pediatric Global Health Scale (PGH-7) parent-proxy form to assess HRQOL and a questionnaire assessing gastrointestinal symptoms. Descriptive statistics, analysis of variance with covariates (ANCOVA), and meditation analyses with bootstrapping were conducted. Results Caregivers of children with VEO-IBD rated their HRQOL as relatively positive, although children with greater disease yielded lower ratings on some PGH-7 items (e.g., fun with friends, physical health, sadness). Compared to healthy youth, children with VEO-IBD scored lower on the PGH-7, with significantly lower item-level scores on overall health, physical health, mental health, and quality of life. Gastrointestinal symptoms mediated the association between health status (i.e., VEO-IBD vs. healthy) and HRQOL, αβ = −2.84, 95% CI = −5.70, −0.34. Conclusions While some children with VEO-IBD are at risk for deficits in HRQOL, many are quite resilient. Psychosocial screening is necessary for providing appropriate referrals to behavioral health services and learning more about psychosocial adjustment in children with VEO-IBD.

Very early onset inflammatory bowel disease (VEO-IBD), diagnosed

Background Mutations in ITCH, which encodes an E3 ubiquitin-protein ligase, can result in systemic autoimmunity and immunodeficiency. The clinical phenotype and mechanism of disease have not been fully characterized, resulting in a paucity of therapeutic options for this potentially fatal disease. Objective We aimed to (1) expand the understanding about the phenotype of human ITCH deficiency (2) further characterize the associated immune dysregulation, and (3) report the first successful hematopoietic cell transplant (HCT) in a patient with ITCH deficiency. Methods Disease profiling was performed in a patient with multisystem immune dysregulation. Whole exome sequencing with trio analysis and functional validation of candidate disease variants were performed, including mRNA and protein expression. Analyses to further delineate the immunophenotype included quantitative evaluation of lymphoid and myeloid subsets with flow cytometry and mass cytometry. Results A patient with multisystem immune dysregulation presenting with growth failure, very-early-onset inflammatory bowel disease, arthritis, uveitis, psoriasis, and type 1 diabetes mellitus underwent whole exome sequencing, which identified novel compound heterozygous mutations in ITCH. Reduced expression of ITCH mRNA and absent ITCH protein were found. Abnormalities in both lymphoid and myeloid lineages were identified. The patient underwent HCT. He demonstrated excellent immune reconstitution and resolution of many manifestations of his systemic disease. Conclusions Here we report ITCH deficiency with unique clinical features of colonic very-early-onset inflammatory bowel disease, arthritis, and uveitis in the setting of immune dysregulation and further characterize the underlying immune dysregulation. We demonstrate that HCT can be an effective, and potentially curative, therapy for ITCH deficiency.

A) PURPOSE OF REVIEW: Biologics for the treatment of inflammatory bowel disease (IBD) have been transformative to the therapeutic goals in the pediatric population. We review the biologics used to treat IBD, highlighting the importance of patient selection, dosing considerations, and therapeutic drug monitoring in children. B) RECENT FINDINGS: Infliximab is well-established as a safe and efficacious therapy for Crohn disease and ulcerative colitis. Both dose escalation strategies and therapeutic drug monitoring increase the likelihood of response to anti-TNFα therapies. Early real-world experience of vedolizumab and ustekinumab in pediatric IBD shows promising results, including clinical response rates comparable to what is seen in adults, but there are limited data using them as first-line therapies. C) SUMMARY: Biologic therapies have improved outcomes in pediatric IBD, including achieving mucosal healing as well as improved growth and pubertal development. Therapeutic drug monitoring improves likelihood of response to anti-TNFα therapies, but further studies for vedolizumab and ustekinumab are necessary.

Background Recent studies have shown that oral combination antibiotics may improve disease course in refractory inflammatory bowel disease (IBD). Here, we describe the use of combination oral antibiotics as salvage therapy in refractory ulcerative colitis (UC), Crohn’s colitis, and IBD-unclassified (IBD-U) at a large pediatric IBD center. Methods Clinical response, disease activity indices, adverse events, and clinical outcomes were measured up to 1 year after antibiotic treatment in this retrospective cohort study of children with medically refractory IBD colitis. Results Sixty-three patients with refractory UC, Crohn’s colitis, and IBD-U (median age [interquartile range {IQR}], 15.3 [11.2–16.5] years; median disease duration [IQR], 1.2 [0.41–4.6] years) received a combination of 3 or 4 oral antibiotics (most commonly amoxicillin, metronidazole, and either doxycycline or ciprofloxacin) for a median (IQR) of 29 (21–58) days. Thirty-four patients (54%) were deemed corticosteroid-refractory or -dependent, with the majority (62/63) having a previous or present loss of response or primary nonresponse to anti–tumor necrosis factor alpha (anti-TNFα) therapy. Use of combination antibiotics led to a significant decrease in median Pediatric Ulcerative Colitis Activity Index (PUCAI) score (IQR) from 55 (40–65) to 10 (0–40; P < 0.0001) over 3 ± 1 weeks, with 25/63 (39.7%) patients achieving clinical remission (PUCAI Conclusions Oral combination antibiotics appears to be an effective rescue and steroid-sparing therapy to induce remission in the short term in patients failing a biologic.

Background The incidence of very early onset inflammatory bowel disease (VEOIBD) is increasing, yet the phenotype and natural history of VEOIBD are not well described. Methods We performed a retrospective cohort study of patients diagnosed with VEOIBD (6 years of age and younger) between 2008 and 2013 at 25 North American centers. Eligible patients at each center were randomly selected for chart review. We abstracted data at diagnosis and at 1, 3, and 5 years after diagnosis. We compared the clinical features and outcomes with VEOIBD diagnosed younger than 3 years of age with children diagnosed with VEOIBD at age 3 to 6 years. Results The study population included 269 children (105 [39%] Crohn’s disease, 106 [39%] ulcerative colitis, and 58 [22%] IBD unclassified). The median age of diagnosis was 4.2 years (interquartile range 2.9–5.2). Most (94%) Crohn’s disease patients had inflammatory disease behavior (B1). Isolated colitis (L2) was the most common disease location (70% of children diagnosed younger than 3 years vs 43% of children diagnosed 3 years and older; P = 0.10). By the end of follow-up, stricturing/penetrating occurred in 7 (6.6%) children. The risk of any bowel surgery in Crohn’s disease was 3% by 1 year, 12% by 3 years, and 15% by 5 years and did not differ by age at diagnosis. Most ulcerative colitis patients had pancolitis (57% of children diagnosed younger than 3 years vs 45% of children diagnosed 3 years and older; P = 0.18). The risk of colectomy in ulcerative colitis/IBD unclassified was 0% by 1 year, 3% by 3 years, and 14% by 5 years and did not differ by age of diagnosis. Conclusions Very early onset inflammatory bowel disease has a distinct phenotype with predominantly colonic involvement and infrequent stricturing/penetrating disease. The cumulative risk of bowel surgery in children with VEOIBD was approximately 14%–15% by 5 years. These data can be used to provide anticipatory guidance in this emerging patient population.

In these studies, we evaluated the contribution of the NLRP3 inflammasome to Crohn's disease (CD) in a kindred containing individuals having a missense mutation in CARD8, a protein known to inhibit this inflammasome. Whole exome sequencing and PCR studies identified the affected individuals as having a V44I mutation in a single allele of the T60 isoform of CARD8. The serum levels of IL-1β in the affected individuals were increased compared with those in healthy controls, and their peripheral monocytes produced increased amounts of IL-1β when stimulated by NLRP3 activators. Immunoblot studies probing the basis of these findings showed that mutated T60 CARD8 failed to downregulate the NLRP3 inflammasome because it did not bind to NLRP3 and inhibit its oligomerization. In addition, these studies showed that mutated T60 CARD8 exerted a dominant-negative effect by its capacity to bind to and form oligomers with unmutated T60 or T48 CARD8 that impeded their binding to NLRP3. Finally, inflammasome activation studies revealed that intact but not mutated CARD8 prevented NLRP3 deubiquitination and serine dephosphorylation. CD due to a CARD8 mutation was not effectively treated by anti-TNF-α, but did respond to IL-1β inhibitors. Thus, patients with anti-TNF-α-resistant CD may respond to this treatment option.

Inflammatory bowel disease (IBD) is a multifactorial disease caused by dysregulated immune responses to commensal or pathogenic intestinal microbes, resulting in chronic intestinal inflammation. Patients diagnosed with IBD occurring before the age of 5 are a unique population, known as very early onset (VEO)-IBD and can be phenotypically and genetically distinct from older-onset IBD. We aim to review the clinical presentation of children with VEO-IBD and recent discoveries that point to genomic drivers of disease that may impact our therapeutic decisions.VEO-IBD is increasing in incidence and is associated with more severe disease, aggressive progression and poor response to most conventional therapies. This article will review the advances in sequencing technology that have led to identification of novel gene variants associated with disease and potentially new targeted therapeutic options.Children with VEO-IBD may present with a different phenotype and more severe disease than older children and adults. Identification of the causal gene or pathways, these children may allow for true precision medicine with targeted therapy and improved disease course.

Diverting ileostomy is used as a temporizing therapy in patients with perianal Crohn disease; however, little data exist regarding its use for colonic disease. The primary aim of the present study was to determine the role of diversion in severe refractory colonic inflammatory bowel disease (IBD) in a pediatric population.Retrospective study of patients who underwent diverting ileostomy at The Children's Hospital of Philadelphia from 2000 to 2014 for the management of severe, refractory colonic IBD. Clinical variables were compared in the 1 year before ileostomy and 1 year after diversion. Surgical and disease outcomes including changes in diagnosis were reviewed through 2015.Twenty-four patients underwent diverting ileostomy for refractory colonic disease. Initial diagnoses were Crohn disease in 10 (42%), ulcerative colitis in 1 (4%), and IBD-unclassified in 13 patients (54%). Comparing data before and after surgery, there were statistically significant improvements in height and weight velocities, height velocity z score, blood transfusion requirement, hemoglobin, and hospitalization rates. Chronic steroid use decreased from 71% to 22%. At the conclusion of the study, 10 patients had undergone subsequent colectomy, 7 had successful bowel reanastomosis, and 7 remain diverted. Seven patients (29%) had a change in diagnosis. There were 13 surgical complications in 7 subjects, including prolapse reduction, stoma revision, and resection of ischemic bowel.In pediatric patients with refractory colonic IBD, diverting ileostomy can be a successful intervention to induce clinical stability. Importantly, diversion is a steroid-sparing therapy and allows additional time to clarify the diagnosis.

SummaryInflammatory bowel disease (IBD) is characterized by inappropriate immune responses to the microbiota in genetically susceptible hosts, but pathways that link individual genetic alterations to microbiota-dependent inflammation remain to be identified. Here, we show that loss of X-linked inhibitor of apoptosis protein (XIAP), a gene associated with Mendelian IBD, renders Paneth cells sensitive to microbiota-, tumor-necrosis factor (TNF)- and receptor-interacting protein kinase 3 (RIPK3)-dependent cell death. This is associated with deficiency in Paneth cell-derived antimicrobial peptides and alterations in the stratification and composition of the microbiota. Loss of XIAP is not sufficient to elicit intestinal inflammation, but provides susceptibility to pathobionts able to promote granulomatous ileitis in hosts deficient in XIAP, which can be prevented by administration of a Paneth cell-derived antimicrobial peptide. These data reveal a pathway critical for host-microbial cross-talk, which is required for intestinal homeostasis and the prevention of inflammation, and which is amenable to therapeutic targeting.

BackgroundInsight into the pathogenesis of very early onset-inflammatory bowel disease (VEO-IBD) has expanded through the identification of causative monogenic defects detected in a subset of patients. However, the clinical course of this population remains uncertain. The study objective is to determine whether VEO-IBD is associated with more severe disease, defined as increased surgical intervention and growth failure, than older pediatric IBD. Secondary outcomes included therapeutic response and hospitalizations.MethodsSubjects with IBD diagnosed younger than 6 years old (VEO-IBD) were compared with children diagnosed 6 to 10 (intermediate-onset) and older than 10 years of age (older-onset IBD). Metadata obtained from the medical record included age of onset, disease phenotype and location, surgeries, medical therapy, and comorbid conditions. Length of follow-up was at least 1 year from diagnosis.ResultsThere were 229, 221, and 521 subjects with VEO, intermediate-onset, and older-onset IBD, respectively. Very early onset-inflammatory bowel disease subjects underwent more diverting ileostomies (P < 0.001) and colectomies (P < 0.001) than the older children. There was less improvement in weight- and height-for-age Z scores during the follow-up period in subjects with VEO-IBD. Additionally, subjects with VEO-IBD had higher rates of medication failure at 1 year and were more frequently readmitted to the hospital. Targeted therapy was successfully used almost exclusively in VEO-IBD.ConclusionPatients with VEO-IBD can have a more severe disease course with increased surgical interventions and poor growth as compared with older-onset IBD patients. Further, VEO-IBD patients are more likely to be refractory to conventional therapies. Strategies using targeted therapy in these children can improve outcome and, in some cases, be curative.

A novel homozygous mutation in human IL2RB results in decreased IL-2Rβ protein expression and dysregulated IL-2/15 signaling. This hypomorphic mutation leads to decreased regulatory T cell frequency and an abnormal NK cell compartment, with clinical manifestations of autoimmunity and susceptibility to CMV., The pleiotropic actions of interleukin-2 (IL-2) are essential for regulation of immune responses and maintenance of immune tolerance. The IL-2 receptor (IL-2R) is composed of IL-2Rα, IL-2Rβ, and IL-2Rγ subunits, with defects in IL-2Rα and IL-2Rγ and their downstream signaling effectors resulting in known primary immunodeficiency disorders. Here, we report the first human defect in IL-2Rβ, occurring in two infant siblings with a homozygous IL2RB mutation in the WSXWS motif, manifesting as multisystem autoimmunity and susceptibility to CMV infection. The hypomorphic mutation results in diminished IL-2Rβ surface expression and dysregulated IL-2/15 signaling, with an anticipated reduction in regulatory T cells. However, in contrast to the IL-2Rβ−/− animal model, which lacks NK cells, these siblings demonstrate an expansion of NK cells, particularly the CD56bright subset, and a lack of terminally differentiated NK cells. Thus, the early-onset autoimmunity and immunodeficiency are linked to functional deficits arising from altered IL-2Rβ expression and signaling in T and NK cells., Graphical Abstract

International audience; Interleukin (IL)-2 is a pleiotropic cytokine that is necessary to prevent chronic inflammation in the gastrointestinal tract 1-4. The protective effects of IL-2 involve the generation, maintenance and function of regulatory T (T reg) cells 4-8 , and the use of low doses of IL-2 has emerged as a potential therapeutic strategy for patients with inflammatory bowel disease 9. However, the cellular and molecular pathways that control the production of IL-2 in the context of intestinal health are undefined. Here we show, in a mouse model, that IL-2 is acutely required to maintain T reg cells and immunological homeostasis throughout the gastrointestinal tract. Notably, lineage-specific deletion of IL-2 in T cells did not reduce T reg cells in the small intestine. Unbiased analyses revealed that, in the small intestine, group-3 innate lymphoid cells (ILC3s) are the dominant cellular source of IL-2, which is induced selectively by IL-1β. Macrophages in the small intestine produce IL-1β, and activation of this pathway involves MYD88-and NOD2-dependent sensing of the microbiota. Our loss-of-function studies show that ILC3-derived IL-2 is essential for maintaining T reg cells, immunological homeostasis and oral tolerance to dietary antigens in the small intestine. Furthermore, production of IL-2 by ILC3s was significantly reduced in the small intestine of patients with Crohn's disease, and this correlated with lower frequencies of T reg cells. Our results reveal a previously unappreciated pathway in which a microbiota-and IL-1β-dependent axis promotes the production of IL-2 by ILC3s to orchestrate immune regulation in the intestine. To determine whether IL-2 is constitutively required for the maintenance of T reg cells and immunological homeostasis in the intestine, we administered isotype-control or anti-IL-2 neutralizing antibodies every other day to adult mice for two weeks. Within this short time period, the neutralization of IL-2 promoted an enlargement of the spleen and mesenteric lymph nodes, and caused significant reductions of T reg cells and significant increases in the proliferation of CD4 + T cells throughout the gastrointestinal tract and associated lymphoid tissues, including the mesenteric lymph nodes, large intestine and small intestine (Extended Data Fig. 1a-g). Blockade of IL-2 resulted in significantly enhanced IFNγ production by CD4 + T cells in both the small and large intestine, as well as increased IL-17A production in the large intestine (Extended Data Fig. 1h-k). Previous studies have suggested that CD4 + T cells are the dominant cellular source of IL-2 1,2. Therefore, we generated mice with a lineage-specific deletion of IL-2 in T cells by crossing IL-2-floxed mice 10 with Lck cre mice. Lck cre Il2 f/f mice exhibited a complete loss of IL-2 protein staining in T cells, and we observed a significant reduction in the number of T reg cells, and an increase in CD4 + T cell proliferation and effector function in the mesenteric lymph nodes and large intestine (Extended Data Fig. 2a-g). By contrast, deletion of

Rationale: Infantile inflammatory bowel disease (IBD) is an extremely rare subgroup of IBD that includes patients whose age of onset is younger than 2 years old. These patients can have more surgical interventions, and a severe and refractory disease course with higher rates of conventional treatment failure. Monogenic defects play an important role in this subgroup of IBD, and identification of the underlying defect can guide the therapeutic approach. Patient concerns: In 2007, a 4-month-old girl from a nonconsanguineous family presenting with anal fistula, chronic diarrhea, and failure to thrive. She underwent multiple surgical repairs but continued to have persistent colitis and perianal fistulas. Diagnosis: Crohn's disease was confirmed by endoscopic and histologic finding. Intervention: Conventional pediatric IBD therapy including multiple surgical interventions and antitumor necrosis factor alpha agents were applied. Outcomes: The patient did not respond to conventional pediatric IBD therapy. Interleukin-10 (IL-10) receptor mutation was discovered by whole-exome sequencing and defective IL-10 signaling was proved by functional test of IL-10 signaling pathway by the age of 12. The patient is currently awaiting hematopoietic stem cell transplantation. Lessons: Early detection of underlying genetic causes of patients with infantile-IBD is crucial, since it may prevent patients from undergoing unnecessary surgeries and adverse effects from ineffective medical therapies. Moreover, infantile-IBD patients with complex perianal disease, intractable early onset enterocolitis and extraintestinal manifestations including oral ulcers and skin folliculitis, should undergo genetic and functional testing for IL-10 pathway defect.

BACKGROUND Vedolizumab is effective for inducing and maintaining remission in adults with inflammatory bowel disease (IBD); however, there is limited pediatric data. This study aimed to describe the adverse events and clinical response to vedolizumab in refractory pediatric IBD. METHODS Disease activity indices, clinical response, concomitant medication use, and adverse events were measured over 22 weeks in an observational prospective cohort study of children with refractory IBD who had failed anti-tumor necrosis factor therapy and subsequently initiated vedolizumab therapy. RESULTS Twenty-one subjects, 16 with Crohn disease, received vedolizumab. Clinical response was observed in 6/19 (31.6%) of the evaluable subjects at week 6 and in 11/19 (57.9%) by week 22. Before induction, 15/21 (71.4%) participants were treated with systemic corticosteroids, as compared with 7/21 (33.3%) subjects at 22 weeks. Steroid-free remission was seen in 1/20 (5.0%) subjects at 6 weeks, 3/20 (15.0%) at 14 weeks, and 4/20 (20.0%) at 22 weeks. There was statistically significant improvement in serum albumin and hematocrit; however, C-reactive protein increased by week 22 (P < 0.05). There were no infusion reactions. Vedolizumab was discontinued in 2 patients because of severe colitis, requiring surgical intervention. CONCLUSIONS There is limited experience with vedolizumab therapy in pediatric IBD. There seems to be a marked number of subjects with clinical response in the first 6 weeks that increases further by week 22 despite the severity of disease in this cohort. Adverse events may not be directly related to vedolizumab. This study is limited by small sample size, and larger prospective studies are warranted.

Summary Children with inflammatory bowel diseases (IBD) are particularly vulnerable to infection with Clostridioides difficile (CDI). IBD and IBD + CDI have overlapping symptoms but respond to distinctive treatments, highlighting the need for diagnostic biomarkers. Here, we studied pediatric patients with IBD and IBD + CDI, comparing longitudinal data on the gut microbiome, metabolome, and other measures. The microbiome is dysbiotic and heterogeneous in both disease states, but the metabolome reveals disease-specific patterns. The IBD group shows increased concentrations of markers of inflammation and tissue damage compared with healthy controls, and metabolic changes associate with susceptibility to CDI. In IBD + CDI, we detect both metabolites associated with inflammation/tissue damage and fermentation products produced by C. difficile. The most discriminating metabolite found is isocaproyltaurine, a covalent conjugate of a distinctive C. difficile fermentation product (isocaproate) and an amino acid associated with tissue damage (taurine), which may be useful as a joint marker of the two disease processes.

The evaluation and diagnosis of food protein-induced enterocolitis syndrome (FPIES) is frequently performed through a multidisciplinary approach that includes pediatric gastroenterology and allergy/immunology among other specialties. This chapter focuses on the gastroenterology component of the differential diagnosis and evaluation of this condition. The classic presentation of acute FPIES, including profuse, repetitive vomiting, and dehydration can also be consistent with a variety of other conditions that often occur in a similar age group. The more chronic presentation of FPIES with intermittent vomiting and/or diarrhea leading to failure to thrive has an even broader differential diagnosis and can often be hard to distinguish without extensive workup. The differential diagnosis of each of these presentations, as well as the relevant laboratory and imaging studies that should be considered, is discussed in further detail here.

Background & Aims Fecal microbiota transplantation (FMT) is commonly used to treat Clostridium difficile infection (CDI). CDI is an increasing cause of diarrheal illness in pediatric patients, but the effects of FMT have not been well studied in children. We performed a multi-center retrospective cohort study of pediatric and young adult patients to evaluate the efficacy, safety, and factors associated with a successful FMT for the treatment of CDI. Methods We performed a retrospective study of 372 patients, 11 months to 23 years old, who underwent FMT at 18 pediatric centers, from February 1, 2004, to February 28, 2017; 2-month outcome data were available from 335 patients. Successful FMT was defined as no recurrence of CDI in the 2 months following FMT. We performed stepwise logistic regression to identify factors associated with successful FMT. Results Of 335 patients who underwent FMT and were followed for 2 months or more, 271 (81%) had a successful outcome following a single FMT and 86.6% had a successful outcome following a first or repeated FMT. Patients who received FMT with fresh donor stool (odds ratio [OR], 2.66; 95% CI, 1.39–5.08), underwent FMT via colonoscopy (OR, 2.41; 95% CI, 1.26–4.61), did not have a feeding tube (OR, 2.08; 95% CI, 1.05–4.11), or had 1 less episode of CDI before FMT (OR, 1.20; 95% CI, 1.04–1.39) had increased odds for successful FMT. Seventeen patients (4.7%) had a severe adverse event during the 3-month follow-up period, including 10 hospitalizations. Conclusions Based on the findings from a large multi-center retrospective cohort, FMT is effective and safe for the treatment of CDI in children and young adults. Further studies are required to optimize the timing and method of FMT for pediatric patients—factors associated with success differ from those of adult patients.

Background and aims Children with very early onset inflammatory bowel disease [VEO-IBD] represent a unique cohort, often with a severe phenotype that is refractory to conventional medications, and some cases have underlying primary immunodeficiencies. Previous work has identified distinct histopathological patterns in the gastrointestinal tract in patients with primary immunodeficiencies. The aim of this study is to characterise the diagnostic histological findings in patients with VEO-IBD as compared with older onset paediatric IBD, and determine if there are unique pathological changes that can shed light on the driving forces of the disease, particularly immunodeficiencies. Methods Clinical retrospective chart review, including disease characteristics and endoscopic findings, was performed on all included subjects. Two paediatric pathologists reviewed biopsies from diagnostic upper endoscopies and colonoscopies of subjects with very early onset inflammatory bowel disease and older onset inflammatory bowel disease, to evaluate for the presence of 11 histological features previously associated with inflammatory bowel disease and primary immunodeficiencies. Results The diagnostic gastrointestinal biopsies of subjects with very early onset inflammatory bowel disease differed from those in older onset paediatric IBD, demonstrated by increased frequency of apoptosis, severe chronic architectural changes, small intestine villous blunting, and eosinophils in the crypts, lamina propria, and surface epithelium. Conclusions The diagnostic biopsies of children with very early onset inflammatory bowel disease can identify characteristic features that may be important in guiding the diagnostic work-up in this population.

The epidemiology of inflammatory bowel disease has changed over the past 4 decades. The incidence is rising dramatically and the age of onset has become younger. This changing landscape of inflammatory bowel disease reflects the new recognition that the youngest children with inflammatory bowel disease are enriched in cases with underlying primary immunodeficiency and monogenic causes. The management of these cases can be quite different, with specific genetic etiologies supporting unique interventions and some requiring hematopoietic cell transplantation for effective treatment.

The pleiotropic actions of interleukin-2 (IL-2) are essential for regulation of immune responses and maintenance of immune tolerance. The IL-2 receptor (IL-2R) is composed of IL-2Rα, IL-2Rβ, and IL-2Rγ subunits, with defects in IL-2Rα and IL-2Rγ and their downstream signaling effectors resulting in known primary immunodeficiency disorders. Here, we report the first human defect in IL-2Rβ, occurring in two infant siblings with a homozygous

PURPOSE OF THE REVIEW: Immune dysregulation disorders are among the most rapidly growing set of inborn errors of immunity. One particular subset is the category where early-onset inflammatory bowel disease is the most common manifestation. These disorders are being increasingly appreciated although there has been minimal effort to articulate a unified approach to their diagnosis and management. This review will cover current thinking and strategies related to diagnosis and management of very early-onset inflammatory bowel disease. RECENT FINDINGS: There is an expanding set of monogenic causes of early-onset inflammatory bowel disease. In many cases, the precise genetic cause dictates management. Lessons learned from the management of these monogenic conditions can sometimes be extrapolated to other refractory cases of inflammatory bowel disease. SUMMARY: An integrated approach to diagnosis, risk analysis and management can include diagnostic approaches not often utilized for traditional inflammatory bowel disease such as whole exome sequencing. Management can also include non-traditional approaches such as targeted biologics or hematopoietic cell transplantation.

Background Mutation of the IL2RG gene results in a form of severe combined immune deficiency (SCID-X1), which has been treated successfully with hematopoietic stem cell gene therapy. SCID-X1 gene therapy results in reconstitution of the previously lacking T cell compartment, allowing analysis of the roles of T cell immunity in humans by comparing before and after gene correction. Methods Here we interrogate T cell reconstitution using four forms of high throughput analysis. (1) Estimation of the numbers of transduced progenitor cells by monitoring unique positions of integration of the therapeutic gene transfer vector. (2) Estimation of T cell population structure by sequencing of the recombined T cell receptor (TCR) beta locus. (3) Metagenomic analysis of microbial populations in oropharyngeal, nasopharyngeal, and gut samples. (4) Metagenomic analysis of viral populations in gut samples. Results Comparison of progenitor and mature T cell populations allowed estimation of a minimum number of cell divisions needed to generate the observed populations. Analysis of microbial populations showed the effects of immune reconstitution, including normalization of gut microbiota and clearance of viral infections. Metagenomic analysis revealed enrichment of genes for antibiotic resistance in gene-corrected subjects relative to healthy controls, likely a result of higher healthcare exposure. Conclusions This multi-omic approach enables the characterization of multiple effects of SCID-X1 gene therapy, including T cell repertoire reconstitution, estimation of numbers of cell divisions between progenitors and daughter T cells, normalization of the microbiome, clearance of microbial pathogens, and modulations in antibiotic resistance gene levels. Together, these results quantify several aspects of the long-term efficacy of gene therapy for SCID-X1. This study includes data from ClinicalTrials.gov numbers NCT01410019, NCT01175239, and NCT01129544. Electronic supplementary material The online version of this article (10.1186/s13073-018-0580-z) contains supplementary material, which is available to authorized users.

Interleukin (IL)-2 is a pleiotropic cytokine that is necessary to prevent chronic inflammation in the gastrointestinal tract