Eosinophilic esophagitis: pathophysiology and its clinical implications

Nonepithelial Gene Expression Correlates With Symptom Severity in Adults With Eosinophilic Esophagitis

BACKGROUND

The mechanistic basis of the variable symptomatology seen in eosinophilic esophagitis (EoE) remains poorly understood.

OBJECTIVE

We examined the correlation of a validated, patient-reported outcome metric with a broad spectrum of esophageal transcripts to uncover potential symptom pathogenesis.

METHODS

We extracted data from 146 adults with EoE through the Consortium of Eosinophilic Gastrointestinal Disease Researchers. Patients were subgrouped by esophageal dilation history. We compared a validated patient-reported outcome metric, the EoE Activity Index (EEsAI), with a set of transcripts expressed in the esophagus of patients with EoE, the EoE Diagnostic Panel (EDP). We used single-cell RNA sequencing data to identify the cellular source of EEsAI-related EDP genes and further analyzed patients with mild and severe symptoms.

RESULTS

The EEsAI correlated with the EDP total score, especially in patients without recent esophageal dilation (r = -0.31; P = .003). We identified 14 EDP genes that correlated with EEsAI scores (r ≥ 0.3; P < .05). Of these, 11 were expressed in nonepithelial cells and three in epithelial cells. During histologic remission, only four of 11 nonepithelial genes (36%) versus all three epithelial genes (100%) had decreased expression to less than 50% of that in active EoE. Fibroblasts expressed five of 11 nonepithelial EEsAI-associated EDP genes (45%). A subset of nonepithelial genes (eight of 11; 73%), but not EoE-representative genes (none of four; 0%; CCL26, CAPN14, DSG1, and SPINK7), was upregulated in patients with EoE with the highest versus lowest symptom burden.

CONCLUSION

The correlation of symptoms and nonepithelial esophageal gene expression substantiates that nonepithelial cells (eg, fibroblasts) likely contribute to symptom severity.

Immunoglobulin G4 in eosinophilic esophagitis: Immune complex formation and correlation with disease activity

BACKGROUND

Recent studies have shown deposition of immunoglobulin G4 (IgG4) and food proteins in the esophageal mucosa of eosinophilic esophagitis (EoE) patients. Our aims were to assess whether co-localization of IgG4 and major cow's milk proteins (CMPs) was associated with EoE disease activity and to investigate the proteins enriched in proximity to IgG4 deposits.

METHODS

This study included adult subjects with EoE (n = 13) and non-EoE controls (n = 5). Esophageal biopsies were immunofluorescence stained for IgG4 and CMPs. Co-localization in paired samples from active disease and remission was assessed and compared to controls. The proteome surrounding IgG4 deposits was evaluated by the novel technique, AutoSTOMP. IgG4-food protein interactions were confirmed with co-immunoprecipitation and mass spectrometry.

RESULTS

IgG4-CMP co-localization was higher in the active EoE group compared to paired remission samples (Bos d 4, p = .02; Bos d 5, p = .002; Bos d 8, p = .002). Co-localization was also significantly higher in the active EoE group compared to non-EoE controls (Bos d 4, p = .0013; Bos d 5, p = .0007; Bos d 8, p = .0013). AutoSTOMP identified eosinophil-derived proteins (PRG 2 and 3, EPX, RNASE3) and calpain-14 in IgG4-enriched areas. Co-immunoprecipitation and mass spectrometry confirmed IgG4 binding to multiple food allergens.

CONCLUSION

These findings further contribute to the understanding of the interaction of IgG4 with food antigens as it relates to EoE disease activity. These data strongly suggest the immune complex formation of IgG4 and major cow's milk proteins. These immune complexes may have a potential role in the pathophysiology of EoE by contributing to eosinophil activation and disease progression.

Predictors of histologic response to mepolizumab in pediatric eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) is a chronic, allergic disease of the esophagus. Current treatment options are limited. One experimental therapy is antibodies against interleukin-5 (IL-5). However, it is unknown why some patients respond to anti-IL-5 treatment whereas others do not. We sought to delineate predictors of histologic response to anti-IL-5 therapy in pediatric EoE.

METHODS

This post hoc analysis of a multicenter, double-blind clinical trial (ClinicalTrial.gov identifier: NCT00358449) evaluated mepolizumab for the treatment of EoE in pediatric patients. Predictors were assessed for their association with a histologic response at week 12 of treatment. A histologic response was defined as either <15 eosinophils per hpf or a reduction in peak eosinophil counts by ≥50%. Predictors on univariate analysis with P  < 0.10 were included in multivariate logistic regression models. Statistical significance for multivariate comparisons was set at P  < 0.05.

RESULTS

Patients with a higher BMI were more likely to attain histologic response at week 12, defined as <15 eosinophils per hpf [aOR, 1.31; 95% confidence interval (CI), 1.07-1.60; P  = 0.008]. Higher BMI (aOR, 1.70; 95% CI, 1.06-2.74; P  = 0.029) and signs of exudate plaques on endoscopy (aOR, 18.30; 95% CI, 2.11-158.53; P  = 0.008) were significant predictors of histologic response at week 12 where a histologic response was defined as a reduction in peak eosinophil counts by ≥50.

CONCLUSION

Higher BMI and signs of exudative plaques on endoscopy may be predictors of histologic response in pediatric EoE patients treated with antibodies against IL-5. Further studies are needed to validate our findings.

Recent Trends in the Management of Eosinophilic Esophagitis: A Systematic Review

Eosinophilic esophagitis (EoE) is a chronic immune-mediated condition characterized by inflammation and eosinophilic accumulation of the esophagus, resulting in dysphagia and food impaction. While the exact etiology of EoE remains unclear, it is believed to be triggered by food allergens and dynamic environmental factors, resulting in various clinical manifestations, from inflammation to fibrosis. Although clinical presentation varies with age, the number of eosinophils in esophagogastroduodenal endoscopy remains the diagnostic gold standard. While diet elimination, proton pump inhibitors (PPIs), topical corticosteroids, and biological therapy are promising treatment options for EoE, there are insufficient data to determine the optimal therapeutic treatment approach. Combination therapies - the use of dietary therapies in conjunction with other treatment modalities, such as PPIs, topical corticosteroids, or biologic agents - have also emerged as a potential management strategy for EoE. In this systematic review, we attempt to highlight the recent advances in EoE therapies and provide updated guidance to their management. From 2017 to 2022, we conducted a comprehensive electronic search of PubMed (MEDLINE) using specific keywords related to our objective and eventually included a total of 44 articles.

Adult eosinophilic esophagitis and advances in its treatment

Eosinophilic esophagitis (EoE) is a chronic eosinophil inflammation that seems to be T helper type 2 antigen-driven. The disease is one of several eosinophilic gastrointestinal disorders in which there appears to be inflammation of the gastrointestinal tract without any apparent underlying causes. Differential diagnosis needs to be made with gastroesophageal reflux, which is characterized by chronic inflammation due to gastric refluxate from disorders related to motility. EoE, however, is considered a chronic allergic inflammatory disorder related to destructive tissue remodeling. There seems to be a higher prevalence of EoE in Western countries. It is typically found in atopic male individuals. Physiopathological risk factors include atopy, environmental factors, esophageal epithelial barrier dysfunctions, etc. EoE can cause several symptoms that include retrosternal burning sensation, dysphagia, food impaction, chronic reflux symptoms, nausea, and vomiting. Early diagnosis, which requires a biopsy to assess for esophageal inflammation, is essential for proper treatment. The aim of our brief overview is to summarize the current literature regarding the characteristics, diagnosis, complications, mechanisms of pathology, clinical features, influence of comorbidities, and treatment in patients with EoE.

Association between eosinophilic esophagitis and esophageal dysmotility: A systematic review and meta-analysis

BACKGROUND

There is conflicting evidence about the association between eosinophilic esophagitis (EoE) and esophageal motility disorders. The aim of this study was to evaluate esophageal manometry findings in EoE.

METHODS

We conducted a systematic review using PubMed, EMBASE, and Web of Science. All articles from 1990 to 2021 with EoE patients who underwent esophageal manometry were eligible. We also included pertinent abstracts from national conferences from 2015 to 2020. The primary outcomes were the prevalence of specific Chicago 3 Classification (CCv3) diagnoses in EoE, as well as broader categories of non-relaxing lower esophageal sphincter, and major and minor peristaltic disorders. When multiple studies reported a specific outcome, we performed random effects meta-analysis to obtain pooled prevalence of each outcome. To reduce heterogeneity, we restricted meta-analysis to high-resolution manometry (HRM) studies only.

KEY RESULTS

Of 763 publications identified, 27 original studies met criteria for inclusion, encompassing 706 EoE patients; 14 studies (425 patients) had HRM and underwent meta-analysis. The pooled prevalence of any motility abnormality was 53% (95% CI: 43%-63%), largely comprised of minor motility disorders such as ineffective esophageal motility and fragmented peristalsis. Major motility disorders, classified by CCv3, were less common in EoE, with pooled prevalence of 2% (0%-7%), 10% (5%-16%), and 1% (0%-3%), for achalasia, esophagogastric-junction outflow obstruction, and hypercontractile disorders, respectively.

CONCLUSION AND INFERENCES

Non-specific motility disorders were common in patients with EoE, but major motility disorders were rare. Further studies are needed to determine the relationship between eosinophilic infiltration and the clinical relevance of abnormal esophageal motility findings in this population.

Mechanisms and clinical management of eosinophilic oesophagitis: an overview

Since the first description of eosinophilic oesophagitis (EoE) less than three decades ago, we have observed a striking increase in the number of patients diagnosed with EoE and the understanding of its clinical and immunopathogenic background. Nonetheless, a plethora of open questions await elucidation. In this Review, we discuss the current state of knowledge regarding the underlying mechanisms, particularly environmental factors and their interaction with genetic susceptibility. Subsequently, we discuss how to translate these factors into the diagnostic and therapeutic management of this chronic, immune-mediated disorder. Finally, we dissect the still long list of unmet needs, such as reasons for and handling refractory EoE and atypical clinical presentations. These open questions can guide us through future research steps and potentially foster reconsideration of the diagnostic guidelines of EoE.

Epithelial-intrinsic defects in TGFβR signaling drive local allergic inflammation manifesting as eosinophilic esophagitis

Allergic diseases are a global health challenge. Individuals harboring loss-of-function variants in transforming growth factor-β receptor (TGFβR) genes have an increased prevalence of allergic disorders, including eosinophilic esophagitis. Allergic diseases typically localize to mucosal barriers, implicating epithelial dysfunction as a cardinal feature of allergic disease. Here, we describe an essential role for TGFβ in the control of tissue-specific immune homeostasis that provides mechanistic insight into these clinical associations. Mice expressing a TGFβR1 loss-of-function variant identified in atopic patients spontaneously develop disease that clinically, immunologically, histologically, and transcriptionally recapitulates eosinophilic esophagitis. In vivo and in vitro, TGFβR1 variant-expressing epithelial cells are hyperproliferative, fail to differentiate properly, and overexpress innate proinflammatory mediators, which persist in the absence of lymphocytes or external allergens. Together, our results support the concept that TGFβ plays a fundamental, nonredundant, epithelial cell-intrinsic role in controlling tissue-specific allergic inflammation that is independent of its role in adaptive immunity.

Emerging Therapies for Eosinophilic Gastrointestinal Diseases

Besides eosinophilic esophagitis, other eosinophilic gastrointestinal diseases (EGIDs), such as eosinophilic gastritis, eosinophilic gastroenteritis, and eosinophilic colitis, are increasingly diagnosed over the last decade. Whereas diagnosis and therapy of eosinophilic esophagitis have been standardized, the diagnosis and therapy of other EGIDs are areas of active research. Motivated by the increasing prevalence of these conditions, concerted efforts of different stakeholders have led to the evaluation of targeted biologic therapies for EGID management over the last couple of years, and several promising molecules are currently in the pipeline. This review article provides an overview of targeted biologic therapies for use in EGIDs.

Pathogenesis of Eosinophilic Esophagitis: A Comprehensive Review of the Genetic and Molecular Aspects

Eosinophilic esophagitis (EoE) is a relatively new condition described as an allergic-mediated disease of the esophagus. Clinically, it is characterized by dysphagia, food impaction, and reflux-like symptoms. Multiple genome-wide association studies (GWAS) have been conducted to identify genetic loci associated with EoE. The integration of numerous studies investigating the genetic polymorphisms in EoE and the Mendelian diseases associated with EoE are discussed to provide insights into the genetic risk of EoE, notably focusing on CCL26 and CAPN14. We focus on the genetic loci investigated thus far, and their classification according to whether the function near the loci is known. The pathophysiology of EoE is described by separately presenting the known function of each cell and molecule, with the major contributors being eosinophils, Th2 cells, thymic stromal lymphopoietin (TSLP), transforming growth factor (TGF)-β1, and interleukin (IL)-13. This review aims to provide detailed descriptions of the genetics and the comprehensive pathophysiology of EoE.

Reconsidering the "protective" hypothesis of Helicobacter pylori infection in eosinophilic esophagitis

Since its discovery, Helicobacter pylori (H. pylori) has attracted attention in the biomedical world with its numerous pathophysiologic implications, both gastrointestinal and systemic. Beyond its well-established carcinogenic properties, emerging evidence also supports "harmful" proinflammatory and neurodegenerative roles of H. pylori. On the other hand, H. pylori infection has been proposed to be "protective" against several diseases, such as asthma and gastroesophageal reflux disease. Eosinophilic esophagitis (EoE) is a relatively new, allergen/immune-mediated disease, which has also been linked to these considerations. Main arguments are a postulated shift of immune responses by H. pylori from T helper 2 (T_H 2) to T_H 1 polarization, as well as a potential decline of the H. pylori burden with the dramatic parallel rise of ΕοΕ: a series of observational studies reported an inverse association. In this review, we counter these arguments by providing further epidemiological data, which point out that this generalization might be rather incomplete. We also discuss the limitations of the existing studies evaluating a possible association. Furthermore, we provide current evidence on common pathogenetic components, which share both entities. In summary, the claim that H. pylori is protective against EoE is rather incomplete, and further mechanistic studies are necessary to elucidate a possible association.

Eosinophilic Esophagitis in Children: Clinical Findings and Diagnostic Approach

Eosinophilic esophagitis (EoE) is an emerging chronic immune and antigen-mediated clinicopathologic disease. During the last 2 decades, the incidence of this condition in children has increased significantly, thanks to practitioners for creating the awareness and higher use of diagnostic endoscopy. We have analysed paediatric literature on EoE focusing on the epidemiology, pathophysiology, clinical findings and diagnostic approach. EoE is pathogenically related to a Th2 inflammation characterized by a mixed IgE and non-IgEmediated reaction to food and/or environmental agents. This leads to esophageal dysfunction and remodeling accompanied by subepithelial fibrosis. EoE can be presented with several range of gastrointestinal symptoms, including regurgitation, vomiting, feeding difficulties or feeding refusal in infants and toddlers, as well as heartburn, dysphagia and food bolus impaction in older children and adults. The diagnostic suspicion is based on the presence of chronic symptoms of esophgeal dysfunction and esophageal eosinophilia characterised histologically by a significant eosinophilic infiltration of the oesophageal mucosa (>15 eosinophils per high powered field). In this review, we will provide an update on clinical presentation and diagnostic approach to EoE in children. We emphasized on the relevant aspects of the new clinical condition termed "PPI responsive esophageal eosinophilia", as entities distinct from EoE and the role of PPI trial in the diagnostic workup, therefore we proposed a new diagnostic algorithm.