Eosinophilic esophagitis (EoE) genetic susceptibility is mediated by synergistic interactions between EoE-specific and general atopic disease loci

[Eosinophilic esophagitis-an underestimated food allergy?]

Eosinophilic oesophagitis (EoE) is a chronic T2-inflammatory disease and can be figuratively referred to as atopic dermatitis of the oesophagus. It is an immune-mediated disease caused by food allergens and is histologically defined by eosinophilic infiltration and clinically characterised by symptoms of oesophageal dysfunction. In addition to reducing the currently still considerable diagnostic latency, the focus is on prioritising existing and new treatment options with the aim of ensuring effective patient care with improved quality of life in the long term.

Distinct roles for thymic stromal lymphopoietin (TSLP) and IL-33 in experimental eosinophilic esophagitis

Rationale

Thymic stromal lymphopoietin (TSLP) and IL-33 are alarmins implicated in EoE pathogenesis by activating multiple cells including mast cells (MCs). Whether TSLP or IL-33 have a role in EoE and whether their activities are distinct requires further investigation.

Methods

Experimental EoE was induced in wild type (WT) Il33 -/- and Crlf2 -/- mice. TSLP or IL-5 were neutralized using antibodies. Esophageal histopathology was determined by H&E, anti-Ki67, anti-CD31 and anti-MBP staining. Esophageal RNA was subjected to RNA sequencing. Bone marrow-derived MCs were activated with TSLP and IL-13 was determined (ELISA).

Results

TSLP and IL-33 were overexpressed in human and experimental EoE. Human and mouse esophageal MCs displayed the highest level of Crlf2 (TSLPR) compared to other immune cells. Crlf2 -/- mice were nearly-completely protected from EoE, and TSLP neutralization resulted in decreased basal cell proliferation, eosinophilia, lamina propria thickening and vascularization. Induction of experimental EoE in Il33 -/- mice resulted in reduced eosinophilia but no alterations in tissue remodeling were observed compared to WT mice. RNA sequencing revealed that TSLP regulates the expression of key genes associated with human EoE (e.g. eotaxins, Il19, Klk5, Flg, Il36rn, Il1r2) and suggest a role for TSLP in regulating IL-1 signaling, barrier integrity and epithelial cell differentiation. Experimental EoE was characterized by a MC-associated gene signature and elevated MCs. Activation of MCs with TSLP resulted in secretion of IL-13.

Conclusion

TSLP and IL-33 have non-redundant functions in experimental EoE. This study highlights TSLP as an upstream regulator of IL-13 and a potential therapeutic target for EoE.

Type 2 immunity in allergic diseases

Significant advancements have been made in understanding the cellular and molecular mechanisms of type 2 immunity in allergic diseases such as asthma, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis (EoE), food and drug allergies, and atopic dermatitis (AD). Type 2 immunity has evolved to protect against parasitic diseases and toxins, plays a role in the expulsion of parasites and larvae from inner tissues to the lumen and outside the body, maintains microbe-rich skin and mucosal epithelial barriers and counterbalances the type 1 immune response and its destructive effects. During the development of a type 2 immune response, an innate immune response initiates starting from epithelial cells and innate lymphoid cells (ILCs), including dendritic cells and macrophages, and translates to adaptive T and B-cell immunity, particularly IgE antibody production. Eosinophils, mast cells and basophils have effects on effector functions. Cytokines from ILC2s and CD4+ helper type 2 (Th2) cells, CD8 + T cells, and NK-T cells, along with myeloid cells, including IL-4, IL-5, IL-9, and IL-13, initiate and sustain allergic inflammation via T cell cells, eosinophils, and ILC2s; promote IgE class switching; and open the epithelial barrier. Epithelial cell activation, alarmin release and barrier dysfunction are key in the development of not only allergic diseases but also many other systemic diseases. Recent biologics targeting the pathways and effector functions of IL4/IL13, IL-5, and IgE have shown promising results for almost all ages, although some patients with severe allergic diseases do not respond to these therapies, highlighting the unmet need for a more detailed and personalized approach.

Dual Inhibition of Mast Cells and Thymic Stromal Lymphopoietin Using a Novel Bispecific Antibody, CDX-622

BACKGROUND

Mast cells (MCs) respond to an array of allergens that drive allergic and inflammatory diseases. Stem cell factor (SCF), the ligand for the receptor KIT, is required for MC survival and function. Thymic stromal lymphopoietin (TSLP) is an alarmin that promotes Type 2 inflammation in asthma and other inflammatory diseases. We describe CDX-622, a bispecific antibody (bsAb), that targets both SCF and TSLP to neutralize these distinct cytokines.

METHODS

The bsAb CDX-622 was developed from novel antagonist monoclonal antibodies (mAbs) to SCF (SCF-12) and TSLP (1D10). CDX-622 encodes the full-length 1D10 mAb and the single-chain variable fragment of SCF-12, linked to the C-terminus of the 1D10 heavy chain. CDX-622 was modified to prevent Fcγ receptor interactions and enhance FcRn binding. CDX-622 was tested using in vitro assays of MC and dendritic cell (DC) activation, an ex vivo human skin model, and in vivo studies in nonhuman primates.

RESULTS

Novel SCF and TSLP mAbs with neutralizing activity were generated. The bsAb CDX-622 potently inhibited SCF-driven MC degranulation and TSLP-mediated CCL17 release by DCs. In human skin samples treated with SCF and TSLP, CDX-622 markedly reduced proinflammatory, MC, and DC-related RNA signatures. Additionally, CDX-622 and SCF-12 mAb administered to cynomolgus macaques (Macaca fascicularis) had a profound effect on MCs without any observed toxicity.

CONCLUSIONS

CDX-622 is a potent inhibitor of MCs through the neutralization of SCF and effectively blocks Type 2 inflammatory responses driven by TSLP. Dual inhibition of these cytokines may lead to improved clinical outcomes in certain inflammatory disorders.

Persistent desmoglein-1 downregulation and periostin accumulation in histologic remission of eosinophilic esophagitis

BACKGROUND

Patients with eosinophilic esophagitis (EoE) require long-lasting resolution of inflammation to prevent fibrostenosis and dysphagia. However, the dissociation between symptoms and histologic improvement suggests persistent molecular drivers despite histologic remission.

OBJECTIVE

We characterized persisting molecular alterations in pediatric patients with EoE using tissue transcriptomics and proteomics.

METHODS

Esophageal biopsy samples (n = 247) collected prospectively during 189 endoscopies from pediatric patients with EoE (n = 36, up to 11 follow-up endoscopies) and pediatric controls (n = 44, single endoscopies) were subjected to bulk transcriptomics (n = 96) and proteomics (n = 151). Intercellular junctions (desmoglein-1/3, desmoplakin, E-cadherin) and epithelial-to-mesenchymal transition (vimentin:E-cadherin ratio) were assessed by immunofluorescence staining.

RESULTS

Active EoE (≥15 eosinophils per high-power field [eos/hpf]), inactive EoE (<15 eos/hpf), and deep-remission EoE (0 eos/hpf) were diagnosed in 107 of 185, 78 of 185, and 41 of 185 biopsy samples, respectively. Among the dysregulated genes (up-/downregulated 310/112) and proteins (up-/downregulated 68/16) between active EoE and controls, 17 genes, and 6 proteins remained dysregulated in inactive EoE. Using persistently upregulated genes (n = 9) and proteins (n = 3) only, such as ALOX15, CXCL1, CXCL6, CTSG, CDH26, PRRX1, CLC, EPX, and periostin (POSTN), was sufficient to separate inactive EoE and deep-remission biopsy samples from control tissue. While 32 differentially expressed genes persisted in deep-remission EoE compared to controls, the proteome normalized except for persistently upregulated POSTN. Epithelial-to-mesenchymal transition normalized in inactive EoE, whereas desmosome recovery remained impaired as a result of desmoglein-1 downregulation.

CONCLUSION

The analysis of molecular changes shows persistent EoE-associated esophageal dysregulation despite histologic remission. These data expand our understanding of inflammatory processes and possible mechanisms that underlie tissue remodeling in EoE.

[Eosinophilic esophagitis]

Eosinophilic esophagitis (EoE) was first described in the early 1990s. Initially a rarity, it is now the most common cause of dysphagia for solid foods in young adults. Its prevalence is estimated to be 1:2000. Mechanistically, EoE is characterized by a chronic type‑2 T‑helper cell (Th2) inflammation of the esophagus which is triggered by food allergens. It often occurs in association with other Th2-mediated diseases, such as asthma, atopic dermatitis, and chronic rhinosinusitis with nasal polyps. EoE is diagnosed based on an esophagogastroduodenoscopy with biopsies of the esophageal epithelium. The diagnosis can be established when both symptoms of esophageal dysfunction (usually dysphagia) and an eosinophilic infiltration of at least 15 eosinophils per high-power field (HPF) are present. EoE can be treated with drugs, diet, and endoscopic dilatation. In terms of diet, milk elimination appears most reasonable, particularly as first choice. Drug treatment includes proton pump inhibitors (PPI), topical steroids, and the biologic agent dupilumab. Endoscopic dilatation is effective but does not treat the underlying inflammation. Therefore, it should never be used alone, but rather as an add-on therapy. In cases where clinical suspicion of EoE is strong but no or only few eosinophils are detected in esophageal biopsies, the diagnosis of an EoE variant should be considered. This review article provides a detailed discussion of the epidemiology, clinical features, diagnosis, treatment, and variants of EoE.

Eosinophilic esophagitis in the "atopic march": dupilumab as an "umbrella" strategy for multiple coexisting atopic diseases

Dupilumab is a monoclonal antibody targeting interleukin-4 and interleukin-13, approved for the treatment of multiple T2 diseases and more recently for Eosinophilic Esophagitis (EoE). EoE is a chronic T2 inflammatory disease, believed to be a member of the "atopic march", due to multiple similarities with other atopic diseases, ranging from epidemiology to genetics and pathophysiology. Although often co-existing in the same patient, these diseases are still treated as separated entities by different specialists, resulting in polypharmacy and chronic use of steroids. Thus, a shared-decision approach by a multidisciplinary team composed of different specialists might improve clinical management and outcomes. Yet, prospective data on the effectiveness of dupilumab as a single agent for multiple T2 inflammatory diseases are lacking, since only few case reports and small studies have been published so far reporting outcomes in patients affected by multiple T2 diseases. The purpose of this review is to illustrate the rationale and clinical evidence supporting the possibility of using dupilumab as a single therapeutic agent in those patients affected by multiple T2 diseases in addition to EoE.

The Dynamic Evolution of Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is a chronic, immune-mediated inflammatory condition of the esophagus characterized by eosinophilic infiltration, and hallmark symptoms of esophageal dysfunction such as dysphagia and food impaction. Over the past three decades, EoE has been recognized as a distinct clinical entity, distinguished from gastroesophageal reflux disease (GERD) through advancements in diagnostic techniques, particularly endoscopy with biopsy. The rising global prevalence of EoE reflects enhanced diagnostic awareness, evolving criteria, and environmental along with lifestyle changes. The etiology of EoE is multifactorial, involving genetic predispositions, immune dysregulation, the gut microbiome, and environmental triggers, including dietary allergens and aeroallergens. Key mechanisms include a type 2 helper T-cell (Th2)-driven immune response, epithelial barrier dysfunction, and genetic variants such as CAPN14 and TSLP. Chronic inflammation leads to tissue remodeling, fibrosis, and esophageal narrowing, contributing to disease progression and complications. Management strategies have evolved to include dietary elimination, proton pump inhibitors, topical corticosteroids, biologics, and endoscopic interventions for fibrostenotic complications. Emerging therapies targeting cytokines such as interleukin (IL)-4, IL-5, and IL-13, alongside novel diagnostic tools like the esophageal string test and Cytosponge, offer promising avenues for improved disease control and non-invasive monitoring. Long-term surveillance combining endoscopic and histological evaluations with biomarkers and non-invasive tools is critical to optimizing outcomes and preventing complications. Future research should address gaps in understanding the role of the esophageal microbiome, refine therapeutic approaches, and develop personalized strategies to improve disease management and patient quality of life.

Food Allergy Genetics and Epigenetics: A Review of Genome-Wide Association Studies

In this review, we provide an overview of food allergy genetics and epigenetics aimed at clinicians and researchers. This includes a brief review of the current understanding of genetic and epigenetic mechanisms, inheritance of food allergy, as well as a discussion of advantages and limitations of the different types of studies in genetic research. We specifically focus on the results of genome-wide association studies in food allergy, which have identified 16 genetic variants that reach genome-wide significance, many of which overlap with other allergic diseases, including asthma, atopic dermatitis, and allergic rhinitis. Identified genes for food allergy are mainly involved in epithelial barrier function (e.g., FLG, SERPINB7) and immune function (e.g., HLA, IL4). Epigenome-wide significant findings at 32 loci are also summarized as well as 14 additional loci with significance at a false discovery of < 1 × 10-4. Integration of epigenetic and genetic data is discussed in the context of disease mechanisms, many of which are shared with other allergic diseases. The potential utility of genetic and epigenetic discoveries is deliberated. In the future, genetic and epigenetic markers may offer ways to predict the presence or absence of clinical IgE-mediated food allergy among sensitized individuals, likelihood of development of natural tolerance, and response to immunotherapy.

Development and dysfunction of structural cells in eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a disorder characterized by dysfunction and chronic local inflammation of the esophagus. The incidence and prevalence of EoE are increasing worldwide. The mechanisms responsible are poorly understood, and effective treatment options are limited. From the lumen outward, the esophagus comprises stratified squamous epithelium, lamina propria, and muscle. The tissue-specific nature of EoE strongly suggests that structural cells in the esophagus are involved in the EoE diathesis. Epithelial basal cell hyperplasia and dilated intercellular spaces are cardinal features of EoE. Some patients with EoE develop lamina propria fibrosis, strictures, or esophageal muscle dysmotility. Clinical symptoms of EoE are only weakly correlated with peak eosinophil count, implying that other cell types contribute to EoE pathogenesis. Epithelial, endothelial, muscle, and fibroblast cells can each initiate inflammation and repair, regulate tissue resident immune cells, recruit peripheral leukocytes, and tailor adaptive immune cell responses. A better understanding of how structural cells maintain tissue homeostasis, respond to cell-intrinsic and cell-extrinsic stressors, and exacerbate and/or resolve inflammatory responses in the esophagus is needed. This knowledge will facilitate the development of more efficacious treatment strategies for EoE that can restore homeostasis of both hematopoietic and structural elements in the esophagus.

Pathophysiology of Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is a chronic, progressive immune-mediated disease associated with antigen-driven type 2 inflammation and symptoms of esophageal dysfunction. Research over the last 2 decades has dramatically furthered our understanding of the complex interplay between genetics, environmental exposures, and cellular and molecular interactions involved in EoE. This review provides an overview of our current understanding of EoE pathogenesis.

Eosinophilic Esophagitis: What the Otolaryngologist Needs to Know

Eosinophilic esophagitis is a male-predominant disease with presentations ranging from nonspecific feeding issues to dysphagia and food impaction. The currently proposed pathophysiology is a combination of genetics, allergens, and epithelial barrier impairment. Diagnosis is reliant on history, endoscopic examination, and biopsy. Recent guidelines recognize the role of concurrent gastroesophageal reflux disease. Treatment is based on 3 paradigms: diet, drugs, and dilation. Drug therapy has historically focused on topical corticosteroids; as of 2022, dupilumab was approved for targeted biologic therapy. Dilation is reserved for symptomatic and anatomic management. As this clinical entity is better understood, additional therapies will hopefully be developed.

Gastrointestinal Comorbidities Associated with Atopic Dermatitis-A Narrative Review

The current understanding of atopic dermatitis (AD) seems to be extending beyond a skin-confined condition frequently associated with allergic comorbidities, as in a number of epidemiological studies, the prevalence rate of a range of illnesses has been determined to be greater in patients with AD, or inversely. In most cases, the reasons for this are vague. A subset of these conditions are gastrointestinal disorders, including food sensitization (FS) and food allergy (FA), eosinophilic esophagitis (EoE) (it is of mixed background, both IgE-dependent and independent), food protein-induced enterocolitis syndrome (FPIES) (it exemplifies an IgE-independent food allergy), Crohn's disease (CD), colitis ulcerosa (CU), celiac disease, irritable bowel syndrome (IBS), and gastroesophageal reflux disease (GERD). In this review, we performed a comprehensive search of the literature using the PubMed database. We addressed the epidemiology of the increased co-occurrence of these diseases with AD and discussed potential causes for this subject. Multiple gastroenterological comorbidities appear to be more common in patients with AD, according to our review. The mechanisms that underlie this phenomenon are largely unknown, highlighting the need for further study in this field.

Barrier Dysfunction in Eosinophilic Esophagitis

PURPOSE OF REVIEW

Compelling evidence over the past decade supports the central role of epithelial barrier dysfunction in the pathophysiology of eosinophilic esophagitis (EoE). The purpose of this review is to summarize the genetic, environmental, and immunologic factors driving epithelial barrier dysfunction, and how this impaired barrier can further promote the inflammatory response in EoE.

RECENT FINDINGS

Common environmental exposures, such as detergents, may have a direct impact on the esophageal epithelial barrier. In addition, the effects of IL-13 on barrier dysfunction may be reduced by 17β-estradiol, Vitamin D, and the short chain fatty acids butyrate and propionate, suggesting novel therapeutic targets. There are many genetic, environmental, and immunologic factors that contribute to epithelial barrier dysfunction in EoE. This leads to further skewing of the immune response to a "Th2" phenotype, alterations in the esophageal microbiome, and penetration of relevant antigens into the esophageal mucosa, which are central to the pathophysiology of EoE.

Thymic stromal lymphopoietin (TSLP) is a substrate for tryptase in patients with mastocytosis

Mastocytosis is a heterogeneous disease associated to uncontrolled proliferation and increased density of mast cells in different organs. This clonal disorder is related to gain-of-function pathogenic variants of the c-kit gene that encodes for KIT (CD117) expressed on mast cell membrane. Thymic stromal lymphopoietin (TSLP) is a pleiotropic cytokine, which plays a key role in allergic disorders and several cancers. TSLP is a survival and activating factor for human mast cells through the engagement of the TSLP receptor. Activated human mast cells release several preformed mediators, including tryptase. Increased mast cell-derived tryptase is a diagnostic biomarker of mastocytosis. In this study, we found that in these patients serum concentrations of TSLP were lower than healthy donors. There was an inverse correlation between TSLP and tryptase concentrations in mastocytosis. Incubation of human recombinant TSLP with sera from patients with mastocytosis, containing increasing concentrations of tryptase, concentration-dependently decreased TSLP immunoreactivity. Similarly, recombinant β-tryptase reduced the immunoreactivity of recombinant TSLP, inducing the formation of a cleavage product of approximately 10 kDa. Collectively, these results indicate that TSLP is a substrate for human mast cell tryptase and highlight a novel loop involving these mediators in mastocytosis.

TSLP shapes the pathogenic responses of memory CD4+ T cells in eosinophilic esophagitis

The cytokine thymic stromal lymphopoietin (TSLP) mediates type 2 immune responses, and treatments that interfere with TSLP activity are in clinical use for asthma. Here, we investigated whether TSLP contributes to allergic inflammation by directly stimulating human CD4+ T cells and whether this process is operational in eosinophilic esophagitis (EoE), a disease linked to variants in TSLP. We showed that about 10% of esophageal-derived memory CD4+ T cells from individuals with EoE and less than 3% of cells from control individuals expressed the receptor for TSLP and directly responded to TSLP, as determined by measuring the phosphorylation of STAT5, a transcription factor activated downstream of TSLP stimulation. Accordingly, increased numbers of TSLP-responsive memory CD4+ T cells were present in the circulation of individuals with EoE. TSLP increased the proliferation of CD4+ T cells, enhanced type 2 cytokine production, induced the increased abundance of its own receptor, and modified the expression of 212 genes. The epigenetic response to TSLP was associated with an enrichment in BATF and IRF4 chromatin-binding sites, and these transcription factors were induced by TSLP, providing a feed-forward loop. The numbers of circulating and esophageal CD4+ T cells responsive to TSLP correlated with the numbers of esophageal eosinophils, supporting a potential functional role for TSLP in driving the pathogenesis of EoE and providing the basis for a blood-based diagnostic test based on the extent of TSLP-induced STAT5 phosphorylation in circulating CD4+ T cells. These findings highlight the potential therapeutic value of TSLP inhibitors for the treatment of EoE.

Food Allergy Characteristics Associated With Coexisting Eosinophilic Esophagitis in FARE Registry Participants

BACKGROUND

Eosinophilic esophagitis (EoE) can coexist in individuals with food allergy.

OBJECTIVE

To evaluate the characteristics of food-allergic patients with and without coexisting EoE using a large food allergy patient registry.

METHODS

Data were derived from 2 Food Allergy Research & Education, Inc, Patient Registry surveys. A series of multivariable regression models were used to evaluate associations between demographic, comorbidity, and food allergy characteristics and the likelihood of reporting EoE.

RESULTS

Five percent (n = 309) of registry participants (n = 6074; ages <1 year->80 years, mean, 20.20 ± 15.37 years) reported having EoE. The odds of having EoE were significantly greater in male participants (adjusted odds ratio [aOR], 1.3; 95% CI, 1.04-1.72) and those with comorbid asthma (aOR, 2.0; 95% CI, 1.55-2.49), allergic rhinitis (aOR, 1.8; 95% CI, 1.37-2.22), oral allergy syndrome (aOR, 2.8; 95% CI, 2.09-3.70), food protein-induced enterocolitis syndrome (aOR, 2.5; 95% CI, 1.34-4.84), and hyper-IgE syndrome (aOR, 7.6; 95% CI, 2.93-19.92), though not atopic dermatitis (aOR, 1.3; 95% CI, 0.99-1.59), when adjusting for demographics (sex, age, race, ethnicity, and geographic location). Those with a greater number of food allergies (aOR, 1.3; 95% CI, 1.23-1.32), more frequent food-related allergic reactions (aOR, 1.2; 95% CI, 1.11-1.24), previous anaphylaxis (aOR, 1.5; 95% CI, 1.15-1.83), and health care utilization for food-related allergic reactions (aOR, 1.3; 95% CI, 1.01-1.67)-specifically intensive care unit admission (aOR, 1.2; 95% CI, 1.07-1.33)-were more likely to have EoE after controlling for demographics. However, no significant difference in ever using epinephrine for food-related allergic reactions was detected.

CONCLUSIONS

These self-reported data showed that coexisting EoE is associated with an increased number of food allergies, food-related allergic reactions per year, and measures of reaction severity, calling attention to the likely increased health care needs of food-allergic patients with EoE.

Genetic and Molecular Contributors in Eosinophilic Esophagitis

PURPOSE OF REVIEW

Eosinophilic esophagitis (EoE) is an allergic inflammatory esophageal disorder with a complex underlying genetic and molecular etiology. The interest of the scientific community in EoE has grown considerably over the past three decades, and the understanding of the genetic and molecular mechanisms involved in this disease has greatly increased.

RECENT FINDINGS

In this article, we aim to provide both historic aspects and updates on the recent genetic and molecular advances in the understanding of EoE. Although EoE is a relatively newly described disorder, much progress has been made toward identifying the genetic and molecular factors contributing to the disease pathogenesis by a variety of approaches with next-generation sequencing technologies, including genome-wide association study, whole exome sequencing, and bulk and single-cell RNA sequencing. This review highlights the multifaceted impacts of various findings that have shaped the current molecular and genetic landscape of EoE, providing insights that facilitate further understanding of the disease process.

Eosinophilic Esophagitis beyond Eosinophils - an Emerging Phenomenon Overlapping with Eosinophilic Esophagitis: Collegium Internationale Allergologicum (CIA) Update 2023

Having long been considered the mainstay in eosinophilic esophagitis (EoE) diagnosis and pathogenesis, the role of eosinophils has been questioned and might be less important than previously thought. It is well known now that EoE is a Th2-mediated disease with many more disease features than eosinophilic infiltration. With more knowledge on EoE, less pronounced phenotypes or nuances of the disease have become apparent. In fact, EoE might be only the tip of the iceberg (and the most extreme phenotype) with several variant forms, at least three, lying on a disease spectrum. Although a common (food induced) pathogenesis has yet to be confirmed, gastroenterologists and allergologists should be aware of these new phenomena in order to further characterize these patients. In the following review, we discuss the pathogenesis of EoE, particularly those mechanisms beyond eosinophilic infiltration of the esophageal mucosa, non-eosinophilic inflammatory cell populations, the new disease entity EoE-like disease, variant forms of EoE, and the recently coined term mast cell esophagitis.

Induction of Severe Eosinophilic Esophagitis and Multi-Organ Inflammation by Airborne Allergens is Associated with IL-4/IL-13 and CCL11 but Not IgE in Genetic Susceptible Mice

Background

Eosinophilic Esophagitis (EoE) is an increasingly common chronic inflammatory disease. The pathological mechanisms underlying EoE are largely unknown.

Objective

We sought to understand the mechanisms underlying aeroallergen-induced EoE in Sharpin gene deficient (Sharpin-/-) mice that is prone to inflammatory response.

Methods

Sharpin-/-mice were exposed with Aspergillus fumigatus and ovalbumin intranasally every alternate day for 4 weeks. Wild type (WT) naïve mice, WT exposed, and un-exposed Sharpin-/- mice were controls. Histopathological analysis was performed by H&E, trichrome and major basic protein staining. Total and specific IgE, IgG, and IgA levels were measured by ELISA and Th2 cytokine and CCL11 chemokine gene expression were determined.

Results

Airborne allergen exposed Sharpin-/- mice showed severe eosinophilic inflammation in the esophagus (p < 0.001), and markedly increased epithelial thickening (p < 0.0001) compared to WT normal controls, whereas airborne allergen exposed WT mice and unexposed Sharpin-/- mice only showed mild eosinophilic inflammation in the esophagus. These exposed Sharpin-/- mice also showed over 7-fold increase in blood eosinophils (p < 0.0001), 60-fold increase in eosinophils in bronchoalveolar lavage fluid (p < 0.0001) and 4-fold increase in eosinophils in the skin (p < 0.0001) compared to normal controls. Surprisingly, exposed Sharpin-/- mice did not show elevation of serum total or antigen-specific IgE levels but reduced total IgA and IgG levels than normal controls There was a marked increase in IL-4, IL-13 and CCL11 gene expression in esophageal tissue (p < 0.001) in exposed Sharpin-/- mice compared to WT normal mice.

Conclusion

Th2 cytokines and chemokines, but not IgE may play an important pathologic role in aeroallergen-induced EoE. This study may provide insight into new therapeutics for EoE.

Butyrate and propionate restore interleukin 13-compromised esophageal epithelial barrier function

BACKGROUND

Eosinophilic esophagitis (EoE) is a food allergen driven disease that is accompanied by interleukin (IL) 13 overexpression and esophageal barrier dysfunction allowing transepithelial food allergen permeation. Nutraceuticals, such as short-chain fatty acids (SCFAs) that restore barrier function and increase immune fitness may be a promising tool in the management of EoE. Here, we investigated the effects of the SCFAs acetate, propionate, and butyrate on an IL-13-compromised human esophageal epithelial barrier, including the mechanisms involved.

METHODS

An air-liquid interface culture model of differentiated human EPC2-hTERT (EPC2) was used to study whether SCFAs could restore barrier function after IL-13-induced impairment. Esophageal epithelial barrier function was monitored by transepithelial electrical resistance (TEER) and FITC-dextran paracellular flux, and was further examined by qPCR and immunohistochemical analysis. G protein-coupled receptor (GPR) GPR41, GPR43, GPR109a, or histone deacetylase (HDAC) (ant)agonists were used to assess mechanisms of action of SCFAs.

RESULTS

IL-13 stimulation decreased TEER and increased FITC flux, which was counteracted by butyrate and propionate, but not acetate treatment. Barrier proteins FLG and DSG1 mRNA expression was upregulated following butyrate and propionate treatment, whereas expression of eosinophil chemoattractant CCL26 and protease CAPN14 was downregulated. Similarly, butyrate and propionate restored FLG and DSG1 protein expression. Similar effects were observed with an HDAC antagonist but not with GPR agonists.

CONCLUSION

Nutraceuticals butyrate and propionate restore the barrier function of esophageal epithelial cells after an inflammatory insult and may be of therapeutic benefit in the management of EoE.

Clinicopathological Differences between Eosinophilic Esophagitis and Asymptomatic Esophageal Eosinophilia

Objective According to consensus guidelines, eosinophilic esophagitis (EoE) is defined as a clinicopathological entity whose symptoms and histology must always be considered together. However, endoscopic findings typical of EoE are often seen in asymptomatic esophageal eosinophilia (aEE). We aimed to clarify the clinicopathological features of aEE. Methods We retrospectively compared cases of aEE and those of symptomatic EoE. Materials We reviewed 146 patients who underwent upper gastrointestinal endoscopy and were confirmed histopathologically to have esophageal eosinophil infiltration of at least 15 eosinophils per high-power field. They were divided into the aEE group (n=75) and the EoE group (n=71). Patients' clinicopathological findings were then collected and examined. Results The EoE group experienced dysphagia (47.9%), heartburn (40.8%), food impaction (40.8%), chest pain (16.9%), and other symptoms (8.5%). There was no significant difference between the two groups with regard to age, sex, current smoking status, or alcohol consumption. The aEE group had a significantly higher body mass index (p<0.01) and significantly lower frequency of concurrent allergic diseases (p<0.01) than the EoE group. No significant differences were found between the two groups with regard to the mean peripheral blood eosinophil count, non-specific immunoglobulin E concentration, peak eosinophil infiltration in the biopsy specimens, EoE histology scoring system, phenotype and location of typical endoscopic findings of EoE, or thickness of the esophagus wall or the mucosal and submucosal layer as measured by endoscopic ultrasonography. Two patients in the aEE group who were followed up without treatment subsequently developed esophageal symptoms. Conclusion aEE and EoE may have the same clinicopathological features.

TSLP disease-associated genetic variants combined with airway TSLP expression influence asthma risk

BACKGROUND

Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine important in initiation of allergic inflammation. Single nucleotide polymorphisms (SNPs) in TSLP are associated with asthma, yet studies have shown inconsistent associations between circulating TSLP and asthma. Studies that integrate the combined effects of TSLP genotype, TSLP mRNA, circulating TSLP levels, and asthma outcome are lacking.

OBJECTIVES

This study sought to recruit a novel cohort based on asthma-relevant TSLP SNPs and determine their impact on TSLP mRNA expression and TSLP circulating protein levels, and their individual and combined effects on asthma.

METHODS

This study developed an algorithm to prioritize TSLP SNPs and recruited 51 carriers and noncarriers based on TSLP genotypes. TSLP mRNA was quantified in nasal epithelial cells and circulating TSLP levels in plasma. This study determined the associations of defined TSLP risk genotypes and/or TSLP mRNA and protein levels with asthma.

RESULTS

TSLP mRNA expression, but not circulating TSLP, was significantly increased in people who are asthmatic compared with in people who are nonasthmatic (P = .007; odds ratio, 1.44). Notably, 90% of children with the defined TSLP risk genotypes and high nasal TSLP mRNA expression (top tertile) had asthma compared with 40% of subjects without risk genotypes and with low TSLP expression (bottom tertile) (P = .024). No association between circulating TSLP and asthma was observed.

CONCLUSIONS

Collectively, these data suggest childhood asthma is modified by the combined effects of TSLP genotype and TSLP expression in the nasal epithelium. The increased asthma risk likely manifests when genetic variation enables expression quantitative trait loci in the TSLP locus to elevate TSLP. It is important to consider both biomarkers when factoring asthma risk.

Viral Induced Effects on a Vulnerable Epithelium; Lessons Learned From Paediatric Asthma and Eosinophilic Oesophagitis

The epithelium is integral to the protection of many different biological systems and for the maintenance of biochemical homeostasis. Emerging evidence suggests that particular children have epithelial vulnerabilities leading to dysregulated barrier function and integrity, that resultantly contributes to disease pathogenesis. These epithelial vulnerabilities likely develop in utero or in early life due to various genetic, epigenetic and environmental factors. Although various epithelia are uniquely structured with specific function, prevalent allergic-type epithelial diseases in children potentially have common or parallel disease processes. These include inflammation and immune response dysregulation stemming from atypical epithelial barrier function and integrity. Two diseases where aetiology and pathogenesis are potentially linked to epithelial vulnerabilities include Paediatric Asthma and Eosinophilic Oesophagitis (EoE). For example, rhinovirus C (RV-C) is a known risk factor for paediatric asthma development and is known to disrupt respiratory epithelial barrier function causing acute inflammation. In addition, EoE, a prevalent atopic condition of the oesophageal epithelium, is characterised by similar innate immune and epithelial responses to viral injury. This review examines the current literature and identifies the gaps in the field defining viral-induced effects on a vulnerable respiratory epithelium and resulting chronic inflammation, drawing from knowledge generated in acute wheezing illness, paediatric asthma and EoE. Besides highlighting the importance of epithelial structure and barrier function in allergic disease pathogenesis regardless of specific epithelial sub-types, this review focuses on the importance of examining other parallel allergic-type disease processes that may uncover commonalities driving disease pathogenesis. This in turn may be beneficial in the development of common therapeutics for current clinical management and disease prevention in the future.

Review of eosinophilic oesophagitis in children and young people

Eosinophilic oesophagitis is a relapsing inflammatory disorder involving oesophagus identified over 30 years ago. Diagnosis is made by upper gastrointestinal endoscopy and oesophageal biopsies. There is huge variation in management practices across the globe. Therapeutic options include the use of proton pump inhibitors, topical steroids, and elimination diet. Biologics and immunomodulator drugs are being explored but not yet recommended in children. Long-term treatment may be required to control symptoms and to prevent complications such as fibrosis/stricture.Conclusion: Even though clinicians have better understanding of eosinophilic oesophagitis, further research is warranted in exploring the unmet needs of developing a highly sensitive non-invasive biomarker for its diagnosis and response to treatment along with a robust and easily deliverable therapeutic option. What is Known: •Incidence of eosinophilic oesophagitis has increased over the recent years. •Diagnostic confirmation requires upper gastrointestinal endoscopy and therapeutic options include elimination diet and/or topical steroids. What is New: •There is a lack of consensus ion management strategy with wide variation across the globe. •There is a need to develop a highly reliable and non-invasive biomarker to diagnose eosinophilic oesophagitis and to monitor the response to treatment.

Desmoplakin and periplakin genetically and functionally contribute to eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic allergic inflammatory disease with a complex underlying genetic etiology. Herein, we conduct whole-exome sequencing of a multigeneration EoE pedigree (discovery set) and 61 additional multiplex families with EoE (replication set). A series of rare, heterozygous, missense variants are identified in the genes encoding the desmosome-associated proteins DSP and PPL in 21% of the multiplex families. Esophageal biopsies from patients with these variants retain dilated intercellular spaces and decrease DSP and PPL expression even during disease remission. These variants affect barrier integrity, cell motility and RhoGTPase activity in esophageal epithelial cells and have increased susceptibility to calpain-14-mediated degradation. An acquired loss of esophageal DSP and PPL is present in non-familial EoE. Taken together, herein, we uncover a pathogenic role for desmosomal dysfunction in EoE, providing a deeper mechanistic understanding of tissue-specific allergic responses.

Pilot Study of Anti-Th2 Immunotherapy for the Treatment of Breast Cancer-Related Upper Extremity Lymphedema

Recent studies suggest that Th2 cells play a key role in the pathology of secondary lymphedema by elaborating cytokines such as IL4 and IL13. The aim of this study was to test the efficacy of QBX258, a monoclonal IL4/IL13 neutralizing antibody, in women with breast cancer-related lymphedema (BCRL). We enrolled nine women with unilateral stage I/II BCRL and treated them once monthly with intravenous infusions of QBX258 for 4 months. We measured limb volumes, bioimpedance, and skin tonometry, and analyzed the quality of life (QOL) using a validated lymphedema questionnaire (Upper Limb Lymphedema 27, ULL-27) before treatment, immediately after treatment, and 4 months following treatment withdrawal. We also obtained 5 mm skin biopsies from the normal and lymphedematous limbs before and after treatment. Treatment was well-tolerated; however, one patient with a history of cellulitis developed cellulitis during the trial and was excluded from further analysis. We found no differences in limb volumes or bioimpedance measurements after drug treatment. However, QBX258 treatment improved skin stiffness (p < 0.001) and improved QOL measurements (Physical p < 0.05, Social p = 0.01). These improvements returned to baseline after treatment withdrawal. Histologically, treatment decreased epidermal thickness, the number of proliferating keratinocytes, type III collagen deposition, infiltration of mast cells, and the expression of Th2-inducing cytokines in the lymphedematous skin. Our limited study suggests that immunotherapy against Th2 cytokines may improve skin changes and QOL of women with BCRL. This treatment appears to be less effective for decreasing limb volumes; however, additional studies are needed.

Building a Population Representative Pediatric Biobank: Lessons Learned From the Greater Cincinnati Childhood Cohort

Background: Biobanks can accelerate research by providing researchers with samples and data. However, hospital-based recruitment as a source for controls may create bias as who comes to the hospital may be different from the broader population. Methods: In an effort to broadly improve the quality of research studies and reduce costs and challenges associated with recruitment and sample collection, a group of diverse researchers at Cincinnati Children's Hospital Medical Center led an institution-supported initiative to create a population representative pediatric "Greater Cincinnati Childhood Cohort (GCC)." Participants completed a detailed survey, underwent a brief physician-led physical exam, and provided blood, urine, and hair samples. DNA underwent high-throughput genotyping. Results: In total, 1,020 children ages 3-18 years living in the 7 county Greater Cincinnati Metropolitan region were recruited. Racial composition of the cohort was 84% non-Hispanic white, 15% non-Hispanic black, and 2% other race or Hispanic. Participants exhibited marked demographic and disease burden differences by race. Overall, the cohort was broadly used resulting in publications, grants and patents; yet, it did not meet the needs of all potential researchers. Conclusions: Learning from both the strengths and weaknesses, we propose leveraging a community-based participatory research framework for future broad use biobanking efforts.

Replication and meta-analyses nominate numerous eosinophilic esophagitis risk genes

BACKGROUND

Eosinophilic esophagitis (EoE) is an emerging, chronic, rare allergic disease associated with marked eosinophil accumulation in the esophagus. Previous genome-wide association studies have provided strong evidence for 3 genome-wide susceptibility loci.

OBJECTIVE

We sought to replicate known and suggestive EoE genetic risk loci and conduct a meta-analysis of previously reported data sets.

METHODS

An EoE-Custom single-nucleotide polymophism (SNP) Chip containing 956 candidate EoE risk single-nucleotide polymorphisms was used to genotype 627 cases and 365 controls. Statistical power was enhanced by adding 1959 external controls and performing meta-analyses with 2 independent EoE genome-wide association studies.

RESULTS

Meta-analysis identified replicated association and genome-wide significance at 6 loci: 2p23 (2 independent genetic effects) and 5q22, 10p14, 11q13, and 16p13. Seven additional loci were identified at suggestive significance (P < 10-6): 1q31, 5q23, 6q15, 6q21, 8p21, 17q12, and 22q13. From these risk loci, 13 protein-coding EoE candidate risk genes were expressed in a genotype-dependent manner. EoE risk genes were expressed in disease-relevant cell types, including esophageal epithelia, fibroblasts, and immune cells, with some expressed as a function of disease activity. The genetic risk burden of EoE-associated genetic variants was markedly larger in cases relative to controls (P < 10-38); individuals with the highest decile of genetic burden had greater than 12-fold risk of EoE compared with those within the lowest decile.

CONCLUSIONS

This study extends the genetic underpinnings of EoE, highlighting 13 genes whose genotype-dependent expression expands our etiologic understanding of EoE and provides a framework for a polygenic risk score to be validated in future studies.

Red Between the Lines: Evolution of Eosinophilic Esophagitis as a Distinct Clinicopathologic Syndrome

Eosinophilic esophagitis (EoE) is characterized by eosinophilic infiltration of the esophageal mucosa and symptoms of esophageal dysfunction, including dysphagia. While EoE is still considered a rare disease, in practice it seems that more and more cases are diagnosed every week, research in the field is exploding, and the pipeline for treatments contains multiple agents, some of which are quite far along the development pathway. After only scattered cases and small series were published in the late 1970s and 1980, Stephen Attwood, Thomas Smyrk, Tom DeMeester, and James Jones, published in Digestive Diseases and Sciences in 1993 a seminal report that described a clinicopathologic syndrome of esophageal eosinophilia with dysphagia. This review details the origins of this paper and compares and contrast what was observed then and what is known now about multiple aspects of EoE, including the clinical presentation, diagnosis, epidemiology, natural history, and treatments and outcomes. Moreover, it will highlight how the paper presaged a number of controversies in the field that have yet to be resolved, as well as foreshadowed the collaborative, multidisciplinary approach that has led to rapid advances.

Dysphagia: A review

Dysphagia is a common symptom with several differential diagnoses ranging from benign and functional to life threatening. Given the potential severity, it is essential to obtain an accurate and pointed history to dictate appropriate diagnostic testing. This article differentiates between oropharyngeal and esophageal dysphagia before outlining a systematic approach to subsequent testing, including when to refer to a specialist.

Retrospective chart review: seasonal variation in incidence of bolus impaction is maintained and statistically significant in subgroups with atopy and eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic inflammatory condition with eosinophilic infiltration of the esophageal mucosa. The most prominent symptom is dysphagia, which may result in esophageal bolus impaction in need of surgical extraction. To investigate whether an earlier reported seasonal variation in esophageal bolus impaction present only in a subgroup of patients with EoE and atopic disorders could be confirmed in this larger study. A single center retrospective chart review of patients who were diagnosed with esophageal bolus impaction between January 2004 and December 2017 was performed. Clinical, epidemiological and histologic data were collected. A total of 755 cases with esophageal bolus impaction were reviewed. A significantly higher occurrence of soft bolus impaction in summer and fall was shown in cases with confirmed EoE and in cases with atopy but not in the nonatopic group or in the group with a negative biopsy result. EoE was found in 48% of biopsied patients. A significant seasonal variation in cases with esophageal bolus impaction and concomitant atopy and EoE is confirmed, but the study design does not allow a causative role of allergens to be established.

"Severe-controlled" asthma 4 years later: is it still controlled?

BACKGROUND

Controlled severe asthma is based on needing regular medication and 4 markers of good asthma control. This study reevaluated a community sample defined 4 years earlier as "severe-controlled" based on electronic medical records of medications dispensed over 12 months.

OBJECTIVES

Determine the current extent of clinically-controlled asthma and asthma-related quality-of-life among patients previously considered "severe-controlled".

METHODS

69 patients considered "severe-controlled" 4 years earlier answered a questionnaire that included the asthma control test (ACT), demographics, education, comorbidities, medications, asthma-related healthcare utilization, atopy history, environmental exposures, and follow-up. Patients underwent spirometry, eosinophil count, total IgE, and skin-prick testing for airborne allergens.

RESULTS

Ninety-seven percent reported using combined inhalers (ICS + LABA) regularly. Only 4% visited the ER and none was hospitalized in the last year. Average predicted FEV₁ was 80%. Average ACT score was 19; 51% reported recurrent heartburn, 46% night awakenings and 70% recurrent rhinitis. Skin-prick testing was positive in 72%, average IgE was 376 IU/ml. Eosinophil counts were ≥300/ml in 42% and ≥400/ml in 25%. ACT < 20 was strongly related to recurrent heartburn. Formal education was related to ACT ≥ 20 (p = 0.045) and perception of good asthma control the previous month (p < 0.001). Eosinophil count, recurrent heartburn, total IgE, and recurrent rhinitis were interrelated.

CONCLUSIONS

Among severe asthmatics, good drug compliance, low use of relievers and low rates of exacerbations do not necessarily reflect asthma-related quality-of-life and optimal control. We urge physicians and HMOs to address asthma control in terms of quality-of-life based on validated questionnaires, and offer all patients asthma education; perhaps more to those with low formal education.

The genetic etiology of eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic allergic disease associated with marked mucosal eosinophil accumulation. Multiple studies have reported a strong familial component to EoE, with the presence of EoE increasing the risk for other family members with EoE. Epidemiologic studies support an important role for environmental risk factors as modulators of genetic risk. In a small percentage of cases, including patients who have Mendelian diseases with co-occurrent EoE, rare genetic variation with large effect sizes could mediate EoE and explain multigenerational incidence in families. Common genetic risk variants mediate genetic risk for the majority of patients with EoE. Across the 31 reported independent EoE risk loci (P < 10-5), most of the EoE risk variants are located in between genes (36.7%) or within the introns of genes (42.4%). Although some variants do change the amino acid sequence of genes (2.2%), only 3 of the 31 EoE risk loci harbor an amino acid-changing variant. Thus most EoE risk loci are outside of the coding regions of genes, suggesting a key role for gene regulation in patients with EoE, which is consistent with most other complex diseases.

High-fat diet-induced obesity worsens TH2 immune response and immunopathologic characteristics in murine model of eosinophilic oesophagitis

BACKGROUND

Eosinophilic oesophagitis (EoE) is an emergent chronic immune-mediated disease of the oesophagus, which affects both children and adults. It is clinically characterized by dysphagia, food impaction and oesophageal eosinophilia. Epidemiological studies indicate that obesity can worsen allergic symptoms; however, its effect on EoE immunopathological response has not been evaluated yet. This study aimed to assess the effect of obesity on allergic inflammation and T helper-2 profile in an EoE experimental model.

METHODS

Obesity was induced by high-fat feeding. After 7 weeks of diet, male BALB/c mice were subcutaneously sensitized and orally challenged with OVA.

RESULTS

Obesity itself induced a significant mast cell and eosinophil accumulation in the oesophagus, trachea, gut and lung. After allergy induction, this number was higher, when compared to lean-allergic mice. Moreover, obese-allergic mice showed higher remodelling area, in the oesophagus, associated with higher IL-5 and TSLP mRNA expression. In contrast, FoxP3 and IL-10 were less expressed in comparison with lean-allergic mice. In addition, the amount of CD11c⁺ MHCII⁺ PDL1⁺ dendritic cells was reduced, while the number of CD11c⁺ MHCII⁺ CD80⁺ DCs and CD3⁺ CD4⁺ GATA₃ ⁺ IL-4⁺ cells was increased in obese-allergic mice in the spleen and lymph nodes when compared to lean-allergic mice.

CONCLUSION

Obesity aggravated the immune histopathological characteristics in the EoE experimental model, which was associated with the reduction in the regulatory profile, and the increased inflammatory cells influx, related to the T_H 2 profile. Altogether, the data provide new knowledge about obesity as a risk factor, worsening EoE symptoms, and contribute for future treatment strategies for this specific profile.

Phenotypes and endotypes in eosinophilic esophagitis

OBJECTIVE

To improve understanding of the heterogeneous presentation of eosinophilic esophagitis (EoE), and its different potential phenotypes and endotypes.

DATA SOURCES

We reviewed studies addressing EoE genetics, risks, natural history, treatment, phenotype, or endotype to assess data relating to differences in the presentation of EoE in children and adults. This review was restricted to articles in the English language.

STUDY SELECTIONS

Data source abstracts, pertinent articles, and book chapters meeting the objectives were critically reviewed.

RESULTS

Data to support differing phenotypes and endotypes in EoE are emerging, but findings are based on multiple studies and therefore sometimes incomparable. Like other atopic disorders EoE is a complex disease with diverse clinical presentations (phenotypes) based on response to therapy, natural history, and association with atopic comorbidities. Different pathogenetic mechanisms (endotypes) may drive the multiple phenotypes. T Helper type 2 inflammation, epithelial barrier defects, enhanced fibrosis, and association with rare monogenetic diseases are the most described endotypes in EoE.

CONCLUSION

Eosinophilic esophagitis is an atopic disorder that is increasing in prevalence and can be difficult to treat. Better understanding of phenotypes and endotypes in EoE may enable future care to be individualized more effectively, resulting in shorter time to remission and fewer endoscopies.

Advances in eosinophilic diseases in 2018

Interest in eosinophil biology and eosinophilic diseases is increasing, as reflected in a doubling of the number of annual articles focused on this topic published in the Journal of Allergy and Clinical Immunology over the past decade. Although the majority of these publications relate to eosinophilic asthma, a growing proportion of them focus on breakthroughs in the diagnosis, treatment, and pathogenesis of other eosinophilic disorders, most notably eosinophilic esophagitis. This review highlights advances in our understanding of eosinophilia and eosinophilic disorders (excluding asthma) published in the Journal in 2018.

Eosinophilic esophagitis: early diagnosis is the key

Eosinophilic esophagitis (EoE) is a disorder which affects all ages, from infancy through adulthood. It typically affects atopic individuals (Table 1) and is a chronic allergic disorder, with foods ubiquitous in the diet being the most described trigger of this isolated eosinophilic inflammation of the esophagus in both adults and children. This inflammatory process leads to esophageal symptoms such as dysphagia and feeding intolerance. In this review, we provide a brief overview of the current state of EoE therapy and symptomatology and then try to make the case for early diagnosis and treatment to prevent some of the long-term consequences of esophageal inflammation.

Epithelial origin of eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic, allergen-driven inflammatory disease of the esophagus characterized predominantly by eosinophilic inflammation, leading to esophageal dysfunction. Converging data have placed the esophageal epithelium at the center of disease pathogenesis. In particular, the main EoE disease susceptibility loci at 2p23 and 5p22 encode for gene products that are produced by the esophageal epithelium: the intracellular protease calpain 14 and thymic stromal lymphopoietin, respectively. Furthermore, genetic and functional data establish a primary role for impaired epithelial barrier function in disease susceptibility and pathoetiology. Additionally, the EoE transcriptome, a set of genes dysregulated in the esophagi of patients with EoE, is enriched in genes that encode for proteins involved in esophageal epithelial cell differentiation. This transcriptome has a high proportion of esophagus-specific epithelial genes that are notable for the unexpected enrichment in genes encoding for proteases and protease inhibitors, as well as in IL-1 family genes, demonstrating a previously unappreciated role for innate immunity responses in the esophagus under homeostatic conditions. Among these pathways, basal production of the serine protease inhibitor, Kazal-type 7 (SPINK7) has been demonstrated to be part of the normal differentiation program of esophageal epithelium. Profound lost expression of SPINK7 occurs in patients with EoE and is sufficient for unleashing increased proteolytic activity (including urokinase plasminogen activator), impaired barrier function, and production of large quantities of proinflammatory and proallergic cytokines, including thymic stromal lymphopoietin. Collectively, we put forth a model in which the esophagus is normally equipped as an anti-inflammatory sensing organ and that defects in this pathway, mediated by epithelial protease/protease inhibitor imbalances, unleash inflammatory responses resulting in disorders, such as EoE.

Allergic Comorbidity in Eosinophilic Esophagitis: Mechanistic Relevance and Clinical Implications

Allergic eosinophilic esophagitis (EoE) is a chronic, allergen-mediated inflammatory disease of the esophagus, and the most common cause of prolonged dysphagia in children and young adults in the developed world. While initially undistinguished from gastroesophageal reflux disease-associated esophageal eosinophilia, EoE is now recognized as a clinically distinct entity that shares fundamental inflammatory features of other allergic conditions and is similarly increasing in incidence and prevalence. The clinical and epidemiologic associations between EoE and other allergic manifestations are well established. In addition to exaggerated rates of atopic dermatitis, IgE-mediated food allergy, asthma, and allergic rhinitis in EoE patients, each of these allergic manifestations imparts individual and cumulative risk for subsequent EoE diagnosis. As such, EoE may be a member of the "allergic march"-the natural history of allergic manifestations during childhood. Several determinants likely contribute to the relationship between these conditions, including shared genetic, environmental, and immunologic factors. Herein, we present a comprehensive review of allergic comorbidity in EoE. We discuss areas of the genome associated with both EoE and other allergic diseases, including the well-studied variants encoding thymic stromal lymphopoietin and calpain 14, among other "atopic" regions. We summarize ways that environmental factors (such as microbiome-altering pressures and aeroallergen exposure) may predispose to multiple allergic conditions including EoE. Finally, we touch on some fundamental features of type 2 inflammation, and the resulting implications for the development of multiple allergic manifestations. We conclude with an analysis of the "type 2" biologics, and how mechanistic similarities between EoE and the other allergic manifestations have important implications for screening and treatment of the allergic patient.

Role of genetics, environment, and their interactions in the pathogenesis of eosinophilic esophagitis

The rise in incidence and prevalence of eosinophilic esophagitis (EoE) since the 1990s has prompted investigations into its pathogenesis, natural history, and management. Identified genetic variants in FLG, DSG1, CAPN14, SPINK5, and SPINK7 link EoE to epithelial barrier dysfunction, whereas variants in CCL26, POSTN, and TSLP associate EoE with T helper type 2-mediated immunity. Early-life, infectious, and geographic factors have been implicated in promoting esophageal microbial dysbiosis and, subsequently, T helper type 2 immune responses. However, research into environmental factors and their interactions with genetic variants are not as developed as their genetic counterparts. Further research into the subgroups and epigenetics of EoE will likely promote further understanding.

The Microbiome and Food Allergy

The gut-associated lymphoid tissue (GALT) faces a considerable challenge. It encounters antigens derived from an estimated 1014 commensal microbes and greater than 30 kg of food proteins yearly. It must distinguish these harmless antigens from potential pathogens and mount the appropriate host immune response. Local and systemic hyporesponsiveness to dietary antigens, classically referred to as oral tolerance, comprises a distinct complement of adaptive cellular and humoral immune responses. It is increasingly evident that a functional epithelial barrier engaged in intimate interplay with innate immune cells and the resident microbiota is critical to establishing and maintaining oral tolerance. Moreover, innate immune cells serve as a bridge between the microbiota, epithelium, and the adaptive immune system, parlaying tonic microbial stimulation into signals critical for mucosal homeostasis. Dysregulation of gut homeostasis and the subsequent disruption of tolerance therefore have clinically significant consequences for the development of food allergy.

Singling out Th2 cells in eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a recently described disease in which exposure to specific foods and allergens leads to type 2 inflammation, epithelial barrier dysfunction, and difficulty in swallowing. In the current issue of the JCI, Wen and colleagues investigate tissue T cell heterogeneity in patients with EoE using single-cell RNA sequencing (scRNA-seq). Esophageal epithelium from individuals with EoE convtained a prominent population of Th2 cells not seen in controls. The short-chain fatty acid (SCFA) receptor FFAR3 was found to be highly expressed in EoE Th2 cells. Experiments presented here provide evidence that SCFAs may promote type 2 inflammation in allergic diseases such as EoE and asthma. This study provides an early example of scRNA-seq for identifying relevant cell populations and mechanisms underlying allergic diseases.

Epithelial cell-derived cytokines: more than just signaling the alarm

The epithelial cell-derived cytokines thymic stromal lymphopoietin (TSLP), IL-33, and IL-25 are central regulators of type 2 immunity, which drives a broad array of allergic responses. Often characterized as "alarmins" that are released by the barrier epithelium in response to external insults, these epithelial cell-derived cytokines were initially thought to act only early in allergic inflammation. Indeed, TSLP can condition dendritic cells to initiate type 2 responses, and IL-33 may influence susceptibility to asthma through its role in establishing the immune environment in the perinatal lungs. However, TSLP, IL-33, and IL-25 all regulate a broad spectrum of innate immune cell populations and are particularly potent in eliciting and activating type 2 innate lymphoid cells (ILC2s) that may act throughout allergic inflammation. Recent data suggest that a TSLP/ILC axis may mediate steroid resistance in asthma. Recent identification of memory Th2 cell subsets that are characterized by high receptor expression for TSLP, IL-33, and IL-25 further supports a role for these cytokines in allergic exacerbations. There is therefore growing interest in developing biologics that target TSLP, IL-33, and IL-25. This Review provides an overview of TSLP, IL-33, and IL-25 and the development of blocking antibodies that target these epithelial cell-derived cytokines.

Mechanisms of gastrointestinal allergic disorders

Gastrointestinal (GI) allergic disease is an umbrella term used to describe a variety of adverse, food antigen-driven, immune-mediated diseases. Although these diseases vary mechanistically, common elements include a breakdown of immunologic tolerance, a biased type 2 immune response, and an impaired mucosal barrier. These pathways are influenced by diverse factors such as diet, infections, exposure to antibiotics and chemicals, GI microbiome composition, and genetic and epigenetic elements. Early childhood has emerged as a critical period when these factors have a dramatic impact on shaping the immune system and therefore triggering or protecting against the onset of GI allergic diseases. In this Review, we will discuss the latest findings on the molecular and cellular mechanisms that govern GI allergic diseases and how these findings have set the stage for emerging preventative and treatment strategies.

Epithelial barrier repair and prevention of allergy

Allergic diseases have in common a dysfunctional epithelial barrier, which allows the penetration of allergens and microbes, leading to the release of type 2 cytokines that drive allergic inflammation. The accessibility of skin, compared with lung or gastrointestinal tissue, has facilitated detailed investigations into mechanisms underlying epithelial barrier dysfunction in atopic dermatitis (AD). This Review describes the formation of the skin barrier and analyzes the link between altered skin barrier formation and the pathogenesis of AD. The keratinocyte differentiation process is under tight regulation. During epidermal differentiation, keratinocytes sequentially switch gene expression programs, resulting in terminal differentiation and the formation of a mature stratum corneum, which is essential for the skin to prevent allergen or microbial invasion. Abnormalities in keratinocyte differentiation in AD skin result in hyperproliferation of the basal layer of epidermis, inhibition of markers of terminal differentiation, and barrier lipid abnormalities, compromising skin barrier and antimicrobial function. There is also compelling evidence for epithelial dysregulation in asthma, food allergy, eosinophilic esophagitis, and allergic rhinosinusitis. This Review examines current epithelial barrier repair strategies as an approach for allergy prevention or intervention.