Mucus sialylation determines intestinal host-commensal homeostasis.

Intestinal mucus forms the first line of defense against bacterial invasion while providing nutrition to support microbial symbiosis. How the host controls mucus barrier integrity and commensalism is unclear. We show that terminal sialylation of glycans on intestinal mucus by ST6GALNAC1 (ST6), the dominant sialyltransferase specifically expressed in goblet cells and induced by microbial pathogen-associated molecular patterns, is essential for mucus integrity and protecting against excessive bacterial proteolytic degradation. Glycoproteomic profiling and biochemical analysis of ST6 mutations identified in patients show that decreased sialylation causes defective mucus proteins and congenital inflammatory bowel disease (IBD). Mice harboring a patient ST6 mutation have compromised mucus barriers, dysbiosis, and susceptibility to intestinal inflammation. Based on our understanding of the ST6 regulatory network, we show that treatment with sialylated mucin or a Foxo3 inhibitor can ameliorate IBD.

A Systematic Review of Monogenic Inflammatory Bowel Disease.

BACKGROUND & AIMS: Advances in genomic technologies have led to increasing reports of monogenic inflammatory bowel disease (IBD). Here, we systematically review the literature to determine the clinical features, genetic profile, and previously used treatment strategies in monogenic IBD. METHODS: A systematic review of MEDLINE articles published between January 2000 and December 2020 was conducted. A total of 750 individual monogenic IBD cases were identified from 303 eligible articles. RESULTS: The most frequently reported monogenic IBD genes were IL10RA/B, XIAP, CYBB, LRBA, and TTC7A. In total, 63.4% of patients developed IBD before 6 years of age, 17.4% developed IBD between ages 10 and 17.9 years, and 10.9% developed IBD after age 18. There was a substantial difference between these age groups and the underlying monogenic disorders. Only 31.7% had any history of extraintestinal comorbidity (EIC) before IBD onset, but 76.0% developed at least 1 EIC during their clinical course. The most common EICs were atypical infection (44.7%), dermatologic abnormality (38.4%), and autoimmunity (21.9%). Bowel surgery, biologic therapy, and hematopoietic stem cell transplantation were performed in 27.1%, 32.9%, and 23.1% of patients, respectively. CONCLUSIONS: Monogenic IBD cases, although rare, have varied extraintestinal comorbidities and limited treatment options including surgery and transplant. Early identification and improved understanding of the characteristics of the genes and underlying disease processes in monogenic IBD is important for effective management.

The Diverse Phenotype of Intestinal Dysmotility Secondary to ACTG2-related Disorders.

BACKGROUND AND AIMS: The initial description of a heterozygous dominant ACTG2 variant in familial visceral myopathy was followed by the identification of additional variants in other forms of intestinal dysmotility disorders. we aimed to describe the diverse phenotype of this newly reported and rare disease. METHODS: Report of 4 new patients, and a systematic review of ACTG2-related disorders. we analyzed the population frequency and used in silico gene damaging predictions. Genotype-phenotype correlations were explored. RESULTS: One hundred three patients (52% girls), from 14 publications, were included. Twenty-eight unique variants were analyzed, all exceedingly rare, and 27 predicted to be highly damaging. The median Combined Annotation Dependent Depletion (CADD) score was 29.2 (Interquartile range 26.3-29.4). Most patients underwent abdominal surgery (66%), about half required intermittent bladder catheterization (48.5%), and more than half were parenteral nutrition (PN)-dependent (53%). One-quarter of the patients died (25.7%), and 6 required transplant (5.8%). Girls had a higher rate of microcolon (P  = 0.009), PN dependency (P = 0.003), and death/transplant (P = 0.029) compared with boys, and early disease onset (<2 years of age) was associated with megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS) features. There was no statistical association between disease characteristics and CADD scores. CONCLUSIONS: Damaging ACTG2 variants are rare, often associated with MMIHS phenotype, and overall have a wide phenotypic variation. Symptoms usually present in the perinatal period but can also appear at a later age. The course of the disease is marked by frequent need for surgical interventions, PN support, and mortality. Poor outcomes are more common among girls with ACTG2 variants.

Distinct Patterns of Liver Chemistry Changes in Pediatric Acute Hepatitis of Unknown Origin and COVID-19 Patients: A Systematic Review.

In 2021 and 2022, there were noted to be clusters of pediatric acute hepatitis of unknown origin (AHUO) occurring across the globe. While there was not necessarily a global increase in cases, understanding the pattern of liver injury in AHUO is crucial to properly identify cases of this unexplained phenomenon, especially since it occurred simultaneously with a global resurgence of COVID-19. The objective of this study was to contrast the patterns in liver-relevant biochemical data from COVID-19 patients and AHUO. Studies reporting liver chemistries for cases of AHUO and COVID-19 were identified by a systematic review and search of the literature. For each case, alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, direct bilirubin, and international normalized ratio (INR) levels were extracted as available. These were normalized to multiples of the upper limit of normal by patient age. There were statistically significant greater elevations of ALT and AST in patients with AHUO than in those with COVID-19. Only a subset of patients with COVID-19 had an AST or ALT greater than the normal range. INR elevation could be substantial for both conditions but was also statistically higher in the AHUO group. Liver chemistry changes were not statistically correlated with age. The pattern of liver chemistry changes between AHUO and COVID-19 have some distinctions, which suggests that AHUO is not a phenomenon driven primarily by SARS-CoV-2 infection alone. Differentiating AHUO and COVID-19 would be challenging based on patterns of liver chemistry changes alone.

Clinical features distinguish eosinophilic and reflux-induced esophagitis.

BACKGROUND AND OBJECTIVES: Diagnosing eosinophilic esophagitis (EoE) depends on intraepithelial eosinophil count of ≥15 eosinophils per high-power field (HPF); however, differentiating EoE from gastroesophageal reflux disease (GERD) continues to be a challenge because no true "criterion standard" criteria exist. Identifying clinical and endoscopic characteristics that distinguish EoE could provide a more comprehensive diagnostic strategy than the present criteria. The aim of the study was to determine symptoms and signs that can be used to distinguish EoE from reflux esophagitis. METHODS: Adult and pediatric patients with EoE were identified by present diagnostic guidelines including an esophageal biopsy finding of ≥15 eosinophils/HPF. Patients with GERD were age-matched one to one with patients with EoE. Clinical, endoscopic, and histologic information at the time of diagnosis was obtained from the medical record and compared between pairs by McNemar test. A conditional logistic regression model was created using 6 distinguishing disease characteristics. This model was used to create a nomogram to differentiate EoE from reflux-induced esophagitis. RESULTS: Patients with EoE were 75% men and 68% had a history of atopy. Many aspects of EoE were statistically distinct from GERD when controlling for age. Male sex, dysphagia, history of food impaction, absence of pain/heartburn, linear furrowing, and white papules were the distinguishing variables used to create the logistic regression model and scoring system based on odds ratios. The area under the curve of the receiver-operator characteristic curve for this model was 0.858. CONCLUSIONS: EoE can be distinguished from GERD using a scoring system of clinical and endoscopic features. Prospective studies will be needed to validate this model.

A systematic review of the proposed etiologies of the 2021-2022 outbreaks of pediatric acute hepatitis of unknown etiology.

In April 2022, the World Health Organization (WHO) declared a global outbreak of acute hepatitis of unknown etiology (AHUE) with a high risk of severe outcomes, for which various etiologies have been proposed by the literature. This study examines primary reports of pediatric AHUE cases and summarizes the proposed etiologies. This systematic review collected and evaluated published peer-reviewed articles, official data, and clinical reports of AHUE cases that met the WHO working case definition. 19 hypothesized etiologies for AHUE were identified from 36 sources, which fell into eight categories. While human adenovirus (HAdV) infection, viral infection, and immune-mediated responses were commonly suspected as causes of AHUE, no definitive etiology or epidemiological link has been established. However, recent evidence implicates adeno-associated virus-2 (AAV2) as a likely significant contributor. Conducting a comprehensive literature review following outbreaks is necessary for developing responsive strategies and protocols.

Antigen presentation and MHC class II expression by human esophageal epithelial cells: role in eosinophilic esophagitis.

Professional antigen-presenting cells (APCs) play a crucial role in initiating immune responses. Under pathological conditions, epithelial cells at mucosal surfaces act as nonprofessional APCs, thereby regulating immune responses at the site of exposure. Epithelial cells in the esophagus may contribute to the pathogenesis of eosinophilic esophagitis (EoE) by presenting antigens on the major histocompatibility complex (MHC) class II. Our goal was to demonstrate the ability of esophageal epithelial cells to process and present antigens on the MHC class II system and to investigate the contribution of epithelial cell antigen presentation to EoE. Immunohistochemistry detected HLA-DR, CD80, and CD86 expression and enzyme-linked immunosorbent assay detected interferon-γ (IFNγ) in esophageal biopsies. Antigen presentation was studied using the human esophageal epithelial cell line HET-1A by reverse transcriptase-PCR, flow cytometry, and confocal microscopy. T helper cell lymphocyte proliferation was assessed by flow cytometry and IL-2 secretion. IFNγ and MHC class II were increased in mucosa of patients with EoE. IFNγ increased mRNA of HLA-DP, HLA-DQ, HLA-DR, and CIITA in HET-1A cells. HET-1A engulfed cell debris and processed ovalbumin. HET-1A cells expressed HLA-DR after IFNγ treatment. HET-1A stimulated T helper cell activation. In this study, we demonstrated the ability of esophageal epithelial cells to act as nonprofessional APCs in the presence of IFNγ. Esophageal epithelial cell antigen presentation may contribute to the pathophysiology of eosinophilic esophagitis.

Atopic and non-atopic eosinophilic oesophagitis are distinguished by immunoglobulin E-bearing intraepithelial mast cells.

AIMS: Eosinophilic oesophagitis (EoE) occurs in atopic individuals and features eosinophils and mast cells, but differences in the inflammatory cell density between the epithelium and lamina propria (LP) are not fully understood. The aim of this study was to determine if numbers of eosinophils, B lymphocytes and immunoglobulin E (IgE)-bearing mast cells are increased in the mucosa of EoE patients with and without concurrent atopy. METHODS AND RESULTS: Oesophageal biopsies containing ≥ 4 high-power fields (HPF) of epithelium and LP were identified for normal (n = 9), gastroesophageal reflux disease (GERD) (n = 5) and EoE (n = 25) patients. Patients were classified as atopic or not by clinical history. Immunohistochemistry identified mast cells, B lymphocytes and eosinophils. Eosinophil density was increased in the LP in EoE. Intraepithelial eosinophil density correlated with eosinophils/HPF, CD20(+) B lymphocyte density and tryptase(+) IgE(+) mast cell density. Increased intraepithelial IgE(+) cell density in EoE was associated with mast cells and not B lymphocytes. Intraepithelial IgE(+) mast cell densities were significantly higher in biopsies from the subgroup of EoE patients with atopy. CONCLUSIONS: EoE diagnosis using maximal eosinophil count/HPF correlates with average counts/mm(2), and intraepithelial eosinophil densities are higher in children than adults with EoE. In EoE, numbers of eosinophils and mast cells are increased in the LP. IgE-bearing mast cells are increased in atopic EoE patients but not in non-atopic EoE patients.

Expression of toll-like receptors 2 and 3 on esophageal epithelial cell lines and on eosinophils during esophagitis.

BACKGROUND: The chronic disease eosinophilic esophagitis may be mediated by the innate immune system. Activation of toll-like receptors (TLRs) in other tissues is known to initiate eosinophil infiltration, thus TLRs may be a potential mediator of esophageal eosinophilia. Little is known about TLRs in the esophagus. AIMS: The purpose of this study was to identify the presence and activation of TLR2 and TLR3 on esophageal epithelial cell lines, primary epithelial cells and mucosal esophageal biopsies. METHODS: TLR2 and TLR3 were identified by immunocytochemistry and immunoblot. PCR assessed alterations to gene expression by activation of TLR2 and TLR3. Immunohistochemistry co-localized eosinophils and TLR2/TLR3 on esophageal biopsies. RESULTS: TLR2 and TLR3 were expressed on the esophageal adenocarcinoma cell lines TE-1 and TE-7, but only TLR3 was present on the esophageal epithelial cell line HET-1A. Thymic stromal lymphopoietin gene expression was altered in response to ligands zymosan and polyI:C, demonstrating activation. Primary esophageal epithelial cells did not express TLR2 or TLR3. In esophageal biopsies, TLR2 and TLR3 expression was limited to eosinophils and other immune cells during esophagitis. CONCLUSIONS: TLR2 and TLR3 expression on cultured esophageal epithelial cells differs from TLR2 and TLR3 expression in esophageal biopsies, which is limited to immune cells during esophagitis.

Clinical and Laboratory Characteristics Are Associated With Biologic Therapy Use in Pediatric Inflammatory Bowel Disease: A Retrospective Cohort Study.

BACKGROUND: Biologic agents are a highly useful class of medications for treating inflammatory bowel disease (IBD). Limited evidence exists to guide initiation of biologic therapy, especially in pediatric patients. It is unclear if disease severity is connected to biologic response. We hypothesized that the clinical, biochemical and radiographic characteristics of pediatric IBD at diagnosis were associated with subsequent initiation of biologic therapy. METHODS: We performed a retrospective analysis of the charts of all pediatric patients diagnosed with IBD at our centre over 14 years. Kaplan-Meier curves evaluated patient characteristics at diagnosis with time to initiation of biologic therapy. A Cox proportional hazards model was used for multivariate characteristic analysis. RESULTS: A total of 198 patients were included, 57.6% had Crohn's disease, 27.8% had ulcerative colitis and 14.6% had IBD type unclassified. Mean follow-up time was 47.8 months. About 55.5% of the patients received a biologic medication, the mean time to biologic initiation was 21.5 months. Earlier initiation of biologic therapy was frequently associated with older age, higher disease activity index and lower serum albumin. CONCLUSIONS: Older pediatric patients with more severely active disease and lower serum albumin levels at the time of IBD diagnosis were more likely to initiate biologic therapy when considering biologic initiation, even many years after diagnosis. Identification of these characteristics may help inform decisions to initiate biologic therapy earlier in the IBD disease course.

ARPC1B binds WASP to control actin polymerization and curtail tonic signaling in B cells.

Immune cells exhibit low-level, constitutive signaling at rest (tonic signaling). Such tonic signals are required for fundamental processes, including the survival of B lymphocytes, but when they are elevated by genetic or environmental causes, they can lead to autoimmunity. Events that control ongoing signal transduction are, therefore, tightly regulated by submembrane cytoskeletal polymers like F-actin. The actin-binding proteins that underpin the process, however, are poorly described. By investigating patients with ARPC1B deficiency, we report that ARPC1B-containing ARP2/3 complexes are stimulated by Wiskott Aldrich Syndrome protein (WASP) to nucleate the branched actin networks that control tonic signaling from the B cell receptor (BCR). Despite an upregulation of ARPC1A, ARPC1B-deficient cells were not capable of WASP-mediated nucleation by ARP2/3, and this caused the loss of WASP-dependent structures, including podosomes in macrophages and lamellipodia in B cells. In the B cell compartment, ARPC1B deficiency also led to weakening of the cortical F-actin cytoskeleton that normally curtails the diffusion of BCRs and ultimately resulted in increased tonic lipid signaling, oscillatory calcium release from the endoplasmic reticulum (ER), and phosphorylated Akt. These events contributed to skewing the threshold for B cell activation in response to microbial-associated molecular patterns (MAMPs). Thus, ARPC1B is critical for ARP2/3 complexes to control steady-state signaling of immune cells.

Gain-of-function variants in SYK cause immune dysregulation and systemic inflammation in humans and mice.

Spleen tyrosine kinase (SYK) is a critical immune signaling molecule and therapeutic target. We identified damaging monoallelic SYK variants in six patients with immune deficiency, multi-organ inflammatory disease such as colitis, arthritis and dermatitis, and diffuse large B cell lymphomas. The SYK variants increased phosphorylation and enhanced downstream signaling, indicating gain of function. A knock-in (SYK-Ser544Tyr) mouse model of a patient variant (p.Ser550Tyr) recapitulated aspects of the human disease that could be partially treated with a SYK inhibitor or transplantation of bone marrow from wild-type mice. Our studies demonstrate that SYK gain-of-function variants result in a potentially treatable form of inflammatory disease.

Recurrent abdominal pain and weight loss in an adolescent: celiac artery compression syndrome.

Celiac artery compression syndrome is a rare cause of abdominal pain and weight loss, likely caused by compression of the celiac artery or plexus by the median arcuate ligament. A case of celiac artery compression syndrome in a 17-year-old male patient with severe postprandial pain and weight loss is described. Imaging techniques such as computed tomography, angiography and Doppler ultrasound identified the abnormality, which was corrected by laparoscopic surgery.

Utilization of Whole Exome Sequencing Data to Identify Clinically Relevant Pharmacogenomic Variants in Pediatric Inflammatory Bowel Disease.

INTRODUCTION: We hypothesized that variants within clinically relevant pharmacogenes could be identified using a whole exome sequencing data set derived from a cohort of more than 1,000 patients with inflammatory bowel disease (IBD). METHODS: Pediatric patients diagnosed with IBD underwent whole exome sequencing. We selected 18 genes with supporting literature where specific exonic variants would influence clinical care. RESULTS: We identified actionable pharmacogenomic variants in 63% of patients. Importantly, 5% of patients with IBD were at risk for serious adverse effects from anesthesia and 3% were at increased risk for thrombosis. DISCUSSION: We identified exonic variants in most of our patients with IBD that directly impact clinical care.