Biologic Therapy in Rare Eosinophil-Associated Disorders: Remaining Questions and Translational Research Opportunities.

Rare eosinophil-associated disorders (EADs), including hypereosinophilic syndrome, eosinophilic granulomatosis with polyangiitis and eosinophilic gastrointestinal disorders, are a heterogeneous group of conditions characterized by blood and/or tissue hypereosinophilia and eosinophil-related clinical manifestations. Although the recent availability of biologic therapies that directly and indirectly target eosinophils has the potential to dramatically improve treatment options for all EADs, clinical trials addressing their safety and efficacy in rare EADs have been relatively few. Consequently, patient access to therapy is limited for many biologics, and the establishment of evidence-based treatment guidelines has been extremely difficult. In this regard, multicenter retrospective collaborative studies focusing on disease manifestations and treatment responses in rare EADs have provided invaluable data for physicians managing patients with these conditions and helped identify important questions for future translational research. During the Clinical Pre-Meeting Workshop held in association with the July 2023 biennial meeting of the International Eosinophil Society in Hamilton, Ontario, Canada, the successes and limitations of pivotal multicenter retrospective studies in EADs were summarized, and unmet needs regarding the establishment of guidelines for use of biologics in rare EADs were discussed. Key topics of interest included: 1) clinical outcome measures, 2) minimally invasive biomarkers of disease activity, 3) predictors of response to biologic agents, and 4) long-term safety of eosinophil depletion. Herein, we report a summary of these discussions, presenting a state-of-the-art overview of data currently available for each of these topics, the limitations of the data, and avenues for future data generation through implementation of multidisciplinary and multicenter studies.

Mepolizumab has clinical benefits including oral corticosteroid sparing irrespective of baseline EGPA characteristics.

Background: The Mepolizumab in Relapsing or Refractory EGPA (MIRRA) trial (GSK ID: 115921/NCT02020889) demonstrated that mepolizumab increased remission time and reduced oral corticosteroid (OCS) use compared with placebo in patients with relapsing or refractory eosinophilic granulomatosis with polyangiitis (EGPA). The present analysis investigated the impact of baseline characteristics on clinical outcomes and characterised the OCS-sparing effect of mepolizumab. Methods: In a phase 3, randomised controlled trial for patients with EGPA (MIRRA), patients received standard of care plus mepolizumab 300 mg or placebo every 4 weeks for 52 weeks. The accrued duration of remission, the proportion of patients in remission at weeks 36 and 48, and the proportion of patients with clinical benefit (remission, OCS or relapse-related) were assessed according to baseline EGPA characteristic subgroups (post hoc). Mepolizumab-related OCS-sparing benefits were also quantified. Results: Accrued duration of remission and the proportion of patients in remission at weeks 36 and 48 were greater with mepolizumab than placebo across the baseline subgroups of refractory disease, immunosuppressant use, EGPA duration, relapse number and OCS use ≤20 mg·day-1. The proportion of patients with clinical benefit was greater with mepolizumab versus placebo (range 76-81% versus 25-39%), irrespective of immunosuppressant use or EGPA duration. Patients treated with mepolizumab versus placebo accrued significantly more weeks on OCS ≤4 mg·day-1 (OR 5.06, 95% CI 2.47-10.38) and had a mean of 1423.1 mg less per-patient OCS exposure over 52 weeks. Conclusions: Mepolizumab treatment provided benefits to patients with EGPA across varying baseline clinical characteristics and can be considered an OCS-sparing treatment in EGPA.

HES and EGPA: Two Sides of the Same Coin.

Elevated eosinophil counts are implicated in multiple diseases, from relatively prevalent organ-specific disorders such as severe eosinophilic asthma, to rare multisystem disorders such as hypereosinophilic syndrome (HES) and eosinophilic granulomatosis with polyangiitis (EGPA). Patients with these multisystem diseases, often associated with markedly elevated eosinophil counts, have a substantial risk of morbidity and mortality due to delayed diagnosis or inadequate treatment. A thorough workup of symptomatic patients presenting with elevated eosinophil counts is essential, although in some cases the differential diagnosis may remain difficult because of overlapping presentations between HES and EGPA. Notably, first- and second-line treatment options and response to therapy may differ for specific HES and EGPA variants. Oral corticosteroids are the first line of treatment for HES and EGPA, except when HES is the result of specific mutations driving clonal eosinophilia that are amenable to targeted treatment with a kinase inhibitor. Cytotoxic or immunomodulatory agents may be required for those with severe disease. Novel eosinophil-depleting therapies, such as those targeting interleukin 5 or its receptor, have shown great promise in reducing blood eosinophil counts, and reducing disease flares and relapses in patients with HES and EGPA. Such therapies could reduce the side effects associated with long-term oral corticosteroids or immunosuppressant use. This review provides a pragmatic guide to approaching the diagnosis and clinical management of patients with systemic hypereosinophilic disorders. We highlight practical considerations for clinicians and present cases from real-world clinical practice to show the complexity and challenges associated with diagnosing and treating patients with HES and EGPA.

The Association Between Age at Diagnosis and Disease Characteristics and Damage in Patients With ANCA-Associated Vasculitis.

OBJECTIVE: This study examined the relationship between age at diagnosis and disease characteristics and damage in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). METHODS: Analysis of a prospective longitudinal cohort of patients with granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic GPA (EGPA) in the Vasculitis Clinical Research Consortium (2013-2021). Disease cohorts were divided by age at diagnosis (years): children (<18), young adults (18-40), middle-aged adults (41-65), and older adults (>65). Data included demographics, ANCA type, clinical characteristics, Vasculitis Damage Index (VDI) scores, ANCA Vasculitis Index of Damage (AVID) scores, and novel disease-specific and non-disease-specific damage scores built from VDI and AVID items. RESULTS: Analysis included data from 1020 patients with GPA/MPA and 357 with EGPA. Female predominance in GPA/MPA decreased with age at diagnosis. AAV in childhood was more often GPA and proteinase 3-ANCA positive. Children with GPA/MPA experienced more subglottic stenosis and alveolar hemorrhage; children and young adults with EGPA experienced more alveolar hemorrhage, need for intubation, and gastrointestinal involvement. Older adults (GPA/MPA) had more neurologic manifestations. After adjusting for disease duration, medications, tobacco, and ANCA, all damage scores increased with age at diagnosis for GPA/MPA (P < 0.001) except the disease-specific damage score, which did not differ (P = 0.44). For EGPA, VDI scores increased with age at diagnosis (P < 0.009), whereas all other scores were not significantly different. CONCLUSION: Age at diagnosis is associated with clinical characteristics in AAV. Although VDI and AVID scores increase with age at diagnosis, this is driven by non-disease-specific damage items.

Clinical Benefit of Mepolizumab in Eosinophilic Granulomatosis With Polyangiitis for Patients With and Without a Vasculitic Phenotype.

OBJECTIVE: To evaluate mepolizumab's efficacy in eosinophilic granulomatosis with polyangiitis (EGPA) with and without a vasculitic phenotype. METHODS: The MIRRA study (NCT02020889/GSK ID: 115921) included adults with relapsing/refractory EGPA and 4 or more weeks of stable oral glucocorticoids (OG). Patients received mepolizumab (300 mg subcutaneously every 4 weeks) or placebo, plus standard of care for 52 weeks. This post hoc analysis assessed EGPA vasculitic phenotype using antineutrophil cytoplasmic antibody (ANCA) history, baseline Birmingham Vasculitis Activity Score (BVAS), and Vasculitis Damage Index (VDI) score. Coprimary endpoints included accrued remission over 52 weeks and proportion in remission at Week 36 and Week 48. Remission was defined as a BVAS equal to 0 and an OG dose of 4 or more mg/day of a prednisone equivalent. Types of relapses (vasculitis, asthma, and sino-nasal) and EGPA vasculitic characteristics (by study remission status) were also assessed. RESULTS: A total of 136 patients were included (n = 68, mepolizumab and placebo). Irrespective of history of ANCA positivity status, baseline BVAS, or baseline VDI, the accrued remission duration and the proportion of patients in remission at Weeks 36 and 48 were greater with mepolizumab compared with placebo. With mepolizumab, remission at both Week 36 and Week 48 was achieved by 54% of patients with and 27% of patients without a history of ANCA positivity compared with 0% and 4%, respectively (placebo); 45% of patients with a BVAS of 0 and 22% of patients with BVAS of greater than 0 compared with 5% and 2%, respectively (placebo); and 29% of patients with a VDI score of less than 5 and 37% of patients with a VDI score of 5 or more compared with 6% and 0%, respectively (placebo). Mepolizumab reduced all types of relapses as compared with placebo. Baseline vasculitic characteristics (neuropathy, glomerulonephritis, alveolar hemorrhage, palpable purpura, and ANCA positivity) were generally similar among patients with and without remission. CONCLUSION: Mepolizumab is associated with clinical benefits for patients with and without a vasculitic EGPA phenotype.

Urine eosinophil-derived neurotoxin: A potential marker of activity in select eosinophilic disorders.

BACKGROUND: Biomarkers of eosinophilic disease activity, especially in the context of novel therapies that reduce blood eosinophil counts, are an unmet need. Absolute eosinophil count (AEC) does not accurately reflect tissue eosinophilia or eosinophil activation. Therefore, the aims of this study were to compare the reliability of plasma and urine eosinophil major basic protein 1, eosinophil cationic protein, eosinophil-derived neurotoxin (EDN), and eosinophil peroxidase measurement and to evaluate the usefulness of eosinophil granule protein (EGP) measurement for the assessment of disease activity in patients with eosinophil-associated diseases treated with mepolizumab, benralizumab, or dexpramipexole. METHODS: Eosinophil granule protein concentrations were measured in serum, plasma, and urine from healthy volunteers and patients with hypereosinophilic syndrome (HES), eosinophilic granulomatosis with polyangiitis (EGPA), and eosinophilic asthma using a multiplex assay. RESULTS: Urine EGP concentrations remained stable, whereas serum and plasma EGP concentrations increased significantly with delayed processing. Plasma (p) EDN, but not urine (u) EDN, concentration correlated with AEC and negatively correlated with prednisone dose. Both pEDN and uEDN decreased significantly following treatment of HES patients with benralizumab and EGPA patients with mepolizumab. uEDN appeared to increase with clinical relapse in both patient groups. CONCLUSIONS: Measurement of EGP in urine is noninvasive and unaffected by cellular lysis. Although plasma and urine EDN concentrations showed a similar pattern following benralizumab and mepolizumab treatment, the lack of correlation between AEC or prednisone dose and uEDN concentrations suggests that measurement of uEDN may provide a potential biomarker of disease activity in patients with HES and EGPA.

Clinical Profile and Treatment in Hypereosinophilic Syndrome Variants: A Pragmatic Review.

BACKGROUND: Hypereosinophilic syndrome (HES) is a group of rare hematologic disorders leading to eosinophil-driven tissue damage and dysfunction. Better understanding of HES variants may facilitate improved patient management. OBJECTIVE: To describe disease characteristics, treatment, and outcomes of patients with idiopathic (I-HES), myeloproliferative (M-HES), lymphocytic (L-HES), and chronic eosinophilic leukemia, not otherwise specified (CEL-NOS) among HES case reports and aggregate data where available. METHODS: Relevant articles published between January 1, 2000, and March 20, 2020, were retrieved via PubMed; those reporting secondary, associated/reactive, overlap/single-organ, or familial HES were excluded. RESULTS: Of 188 articles included, 171 contained data on 347 separate HES cases (152 I-HES, 121 M-HES, 62 L-HES, 12 CEL-NOS). Based on individual data, mean age at diagnosis was 43 to 48 years for patients with all HES variants. Males accounted for 90% to 91% of M-HES/CEL-NOS and 55% to 65% of I-HES/L-HES cases. Cardiac symptoms were frequently observed for all HES variants (13%-22% of patients). Respiratory symptoms (I-HES), splenomegaly (M-HES and CEL-NOS), and skin conditions (L-HES) were also frequently observed. Bone marrow, heart, lung, spleen, liver, skin, and lymph nodes were commonly involved. Most patients with I-HES, L-HES, and CEL-NOS received corticosteroids (65%-85%), whereas most with M-HES received imatinib (81%); those with CEL-NOS also received interferon alpha (42%). CONCLUSIONS: Collective analysis of HES case reports supports and extends current understanding of HES variants, highlighting differences in signs and symptoms, organ involvement, and treatment approaches. Improved characterization of HES variants may facilitate the development of novel treatments.

An International, Retrospective Study of Off-Label Biologic Use in the Treatment of Hypereosinophilic Syndromes.

BACKGROUND: Treatment of hypereosinophilic syndrome (HES) often requires the use of immunomodulators with substantial side effect profiles. The emergence of biologics offers an alternative treatment modality. OBJECTIVE: To examine real-world practice data to describe the safety and consequences of various biologics suspected to directly or indirectly affect eosinophilic inflammation for the treatment of HES. METHODS: Retrospective data from 13 centers were collected via an online Research Electronic Data Capture repository. Inclusion criteria included (1) peripheral eosinophil count of 1,500/mm3 or greater without a secondary cause; (2) clinical manifestations attributable to the eosinophilia; and (3) having received mepolizumab (anti-IL-5), benralizumab (afucosylated anti-IL-5 receptor α), omalizumab (anti-IgE), alemtuzumab (anti-CD52), dupilumab (anti-IL-4 receptor α), or reslizumab (anti-IL-5) outside a placebo-controlled clinical trial. RESULTS: Of the 151 courses of biologics prescribed for 121 patients with HES, 59% resulted in improved HES symptoms and 77% enabled tapering of other HES medications. Overall, 105 patients were receiving daily systemic glucocorticoids at the time of a biologic initiation and were able to reduce the glucocorticoid dose by a median reduction of 10 mg of daily prednisone equivalents. Biologics were generally safe and well-tolerated other than infusion reactions with alemtuzumab. Thirteen of 24 patients had clinical improvement after switching biologics and nine patients responded to increasing the dose of mepolizumab after a lack of response to a lower dose. CONCLUSIONS: Biologics may offer a safer treatment alternative to existing therapies for HES, although the optimal dosing and choice for each subtype of HES remain to be determined. Limitations of this study include its retrospective nature and intersite differences in data collection and availability of each biologic.

Eosinophils and eosinophilic immune dysfunction in health and disease.

The functions ascribed to eosinophils have classically been limited to host defence against certain parasitic infections and potentially deleterious effects in the setting of specific diseases that are associated with elevated eosinophil counts in blood and/or tissue. The ability to induce eosinophil depletion either experimentally in animal models or through targeted therapies in humans has extended our understanding of the roles played by eosinophils in health and homeostasis as well as in disease pathogenesis. When associated with human disease aetiology, the eosinophil takes on a pathogenic rather than a protective role. This maladaptive response, called "eosinophilic immune dysfunction" herein, appears central to exacerbation pathogenesis and disease control in severe asthma and may be involved in the aetiology of other eosinophil-related conditions ranging from organ-system-limited diseases such as phenotypic subsets of chronic obstructive pulmonary disease and chronic rhinosinusitis with nasal polyposis to more broadly systemic diseases such as eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndrome. In this review, we describe the evidence supporting eosinophilic functions related to health and homeostasis and explore the contribution of eosinophilic immune dysfunction to human disease.

LIGHT controls distinct homeostatic and inflammatory gene expression profiles in esophageal fibroblasts via differential HVEM and LTßR-mediated mechanisms.

Fibroblasts mediate tissue remodeling in eosinophilic esophagitis (EoE), a chronic allergen-driven inflammatory pathology. Diverse fibroblast subtypes with homeostasis-regulating or inflammatory profiles have been recognized in various tissues, but which mediators induce these alternate differentiation states remain largely unknown. We recently identified that TNFSF14/LIGHT promotes an inflammatory esophageal fibroblast in vitro. Herein we used esophageal biopsies and primary fibroblasts to investigate the role of the LIGHT receptors, herpes virus entry mediator (HVEM) and lymphotoxin-beta receptor (LTßR), and their downstream activated pathways, in EoE. In addition to promoting inflammatory gene expression, LIGHT down-regulated homeostatic factors including WNTs, BMPs and type 3 semaphorins. In vivo, WNT2B+ fibroblasts were decreased while ICAM-1+ and IL-34+ fibroblasts were expanded in EoE, suggesting that a LIGHT-driven gene signature was imprinted in EoE versus normal esophageal fibroblasts. HVEM and LTßR overexpression and deficiency experiments demonstrated that HVEM regulates a limited subset of LIGHT targets, whereas LTßR controls all transcriptional effects. Pharmacologic blockade of the non-canonical NIK/p100/p52-mediated NF-κB pathway potently silenced LIGHT's transcriptional effects, with a lesser role found for p65 canonical NF-κB. Collectively, our results show that LIGHT promotes differentiation of esophageal fibroblasts toward an inflammatory phenotype and represses homeostatic gene expression via a LTßR-NIK-p52 NF-κB dominant pathway.

Inflammatory phenotype modulation in the respiratory tract and systemic circulation of e-cigarette users: a pilot study.

Over 40 million people use e-cigarettes worldwide, but the impact of chronic e-cigarette use on health has not been adequately defined. In particular, effects of e-cigarette aerosol inhalation on inflammation and host defenses across the body are not fully understood. We conducted a longitudinal cohort pilot study to explore changes in the inflammatory state and monocyte function of e-cigarette users (n = 20) versus healthy controls (n = 13) and to evaluate effects of e-cigarette use reduction on the same. Saliva, sputum, and blood were obtained from e-cigarette users at baseline and after a 2-wk intervention of decreased e-cigarette use. Overall, across 38 proteins quantified by multiplex, airway samples from e-cigarette users tended to have decreased levels of immunomodulatory proteins relative to healthy controls, whereas levels of cytokines, chemokines, and growth factors in the circulation tended to be elevated. Specifically, e-cigarette users had lower levels of IL-1 receptor antagonist (IL-1Ra) in saliva (P < 0.0001), with higher IL-1Ra and growth-regulated oncogene (GRO) levels in sputum (P < 0.01 and P < 0.05, respectively), and higher levels of both TNFß (P < 0.0001) and VEGF (P < 0.0001) in plasma. Circulating monocytes from e-cigarette users had alterations in their inflammatory phenotype in response to reduced e-cigarette use, with blunted IL-8 and IL-6 release upon challenge with bacterial lipopolysaccharide (P < 0.001 and P < 0.05, respectively), suggesting a decreased ability to appropriately respond to bacterial infection. Based on these findings, chronic inhalation of e-cigarette aerosols alters the inflammatory state of the airways and systemic circulation, raising concern for the development of both inflammatory and infectious diseases in chronic users of e-cigarettes.

Hypersensitivity pneumonitis, allergic bronchopulmonary aspergillosis and other eosinophilic lung diseases.

Hypersensitivity pneumonitis (HP) is traditionally classified into acute, subacute and chronic forms. A high index of suspicion and a detailed investigation into the patient's environment is the key to diagnosis and treatment of HP. Eosinophilic lung diseases can be broadly categorized as idiopathic (acute eosinophilic pneumonia, chronic eosinophilic pneumonia, eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndromes), those with known cause (allergic bronchopulmonary aspergillosis, drugs, parasitic and non-parasitic infections), and those associated with other known lung diseases (asthma, interstitial lung diseases and lung cancers). A detailed review of drug intake, toxin exposures, and travel history is essential in the differential diagnosis of eosinophilic lung diseases.

Increased Production of LIGHT by T Cells in Eosinophilic Esophagitis Promotes Differentiation of Esophageal Fibroblasts Toward an Inflammatory Phenotype.

BACKGROUND & AIMS: Eosinophilic esophagitis (EoE) is an antigen-mediated eosinophilic disease of the esophagus that involves fibroblast activation and progression to fibrostenosis. Cytokines produced by T-helper type 2 cells and transforming growth factor beta 1 (TGFß1) contribute to the development of EoE, but other cytokines involved in pathogenesis are unknown. We investigate the effects of tumor necrosis factor superfamily member 14 (TNFSF14, also called LIGHT) on fibroblasts in EoE. METHODS: We analyzed publicly available esophageal CD3+ T-cell single-cell sequencing data for expression of LIGHT. Esophageal tissues were obtained from pediatric patients with EoE or control individuals and analyzed by immunostaining. Human primary esophageal fibroblasts were isolated from esophageal biopsy samples of healthy donors or patients with active EoE. Fibroblasts were cultured; incubated with TGFß1 and/or LIGHT; and analyzed by RNA sequencing, flow cytometry, immunoblots, immunofluorescence, or reverse transcription polymerase chain reaction. Eosinophils were purified from peripheral blood of healthy donors, incubated with interleukin 5, cocultured with fibroblasts, and analyzed by immunohistochemistry. RESULTS: LIGHT was up-regulated in the esophageal tissues from patients with EoE, compared with control individuals, and expressed by several T-cell populations, including T-helper type 2 cells. TNF receptor superfamily member 14 (TNFRSF14, also called HVEM) and lymphotoxin beta receptor are receptors for LIGHT that were expressed by fibroblasts from healthy donors or patients with active EoE. Stimulation of esophageal fibroblasts with LIGHT induced inflammatory gene transcription, whereas stimulation with TGFß1 induced transcription of genes associated with a myofibroblast phenotype. Stimulation of fibroblasts with TGFß1 increased expression of HVEM; subsequent stimulation with LIGHT resulted in their differentiation into cells that express markers of myofibroblasts and inflammatory chemokines and cytokines. Eosinophils tethered to esophageal fibroblasts after LIGHT stimulation via intercellular adhesion molecule-1. CONCLUSIONS: T cells in esophageal tissues from patients with EoE express increased levels of LIGHT compared with control individuals, which induces differentiation of fibroblasts into cells with inflammatory characteristics. TGFß1 increases fibroblast expression of HVEM, a receptor for LIGHT. LIGHT mediates interactions between esophageal fibroblasts and eosinophils via ICAM1. This pathway might be targeted for the treatment of EoE.

Pulmonary Eosinophilic Granulomatosis with Polyangiitis Has IgG4 Plasma Cells and Immunoregulatory Features.

The immunologic mechanisms promoting eosinophilic granulomatosis with polyangiitis (EGPA) are unclear. To characterize the mechanisms underlying pulmonary EGPA, we examined and compared EGPA paraffin-embedded lung biopsies with normal lung biopsies, using immunostaining, RNA sequencing, and RT-PCR. The results revealed novel type 2 as well as immuneregulatory features. These features included basophils and increased mast cell contents; increased immunostaining for tumor necrosis factor ligand superfamily member 14; sparse mast cell degranulation; numerous forkhead box protein P3 (FoxP3)+ regulatory T cells and IgG4 plasma cells; and abundant arachidonate 15-lipoxygenase and 25-hydroxyvitamin D-1 α hydroxylase, mitochondrial. Significantly decreased 15-hydroxyprostaglandin dehydrogenase [NAD(+)], which degrades eicosanoids, was observed in EGPA samples. In addition, there was significantly increased mRNA for chemokine (C-C motif) ligands 18 and 13 and major collagen genes, IgG4-rich immune complexes coating alveolar macrophages, and increased immunostaining for phosphorylated mothers against decapentaplegic homolog 2/SMAD2, suggesting transforming growth factor-ß activation. These findings suggest a novel self-promoting mechanism of activation of alveolar macrophages by arachidonate 15-lipoxygenase-derived eicosanoids to express chemokines that recruit a combined type 2/immunoregulatory immune response, which produces these eicosanoids. These results suggest that the pulmonary EGPA immune response resembles the immune response to a tissue-invasive parasite infection.

Human Eosinophils Express a Distinct Gene Expression Program in Response to IL-3 Compared with Common ß-Chain Cytokines IL-5 and GM-CSF.

Despite recent advances in asthma management with anti-IL-5 therapies, many patients have eosinophilic asthma that remains poorly controlled. IL-3 shares a common ß subunit receptor with both IL-5 and GM-CSF but, through α-subunit-specific properties, uniquely influences eosinophil biology and may serve as a potential therapeutic target. We aimed to globally characterize the transcriptomic profiles of GM-CSF, IL-3, and IL-5 stimulation on human circulating eosinophils and identify differences in gene expression using advanced statistical modeling. Human eosinophils were isolated from the peripheral blood of healthy volunteers and stimulated with either GM-CSF, IL-3, or IL-5 for 48 h. RNA was then extracted and bulk sequencing performed. DESeq analysis identified differentially expressed genes and weighted gene coexpression network analysis independently defined modules of genes that are highly coexpressed. GM-CSF, IL-3, and IL-5 commonly upregulated 252 genes and downregulated 553 genes, producing a proinflammatory and survival phenotype that was predominantly mediated through TWEAK signaling. IL-3 stimulation yielded the most numbers of differentially expressed genes that were also highly coexpressed (n = 119). These genes were enriched in pathways involving JAK/STAT signaling. GM-CSF and IL-5 stimulation demonstrated redundancy in eosinophil gene expression. In conclusion, IL-3 produces a distinct eosinophil gene expression program among the ß-chain receptor cytokines. IL-3-upregulated genes may provide a foundation for research into therapeutics for patients with eosinophilic asthma who do not respond to anti-IL-5 therapies.

Development and Application of a Functional Human Esophageal Mucosa Explant Platform to Eosinophilic Esophagitis.

There is an increasing prevalence of esophageal diseases but intact human tissue platforms to study esophageal function, disease mechanisms, and the interactions between cell types in situ are lacking. To address this, we utilized full thickness human donor esophagi to create and validate the ex vivo function of mucosa and smooth muscle (n = 25). Explanted tissue was tested for contractile responses to carbachol and histamine. We then treated ex vivo human esophageal mucosa with a cytokine cocktail to closely mimic the Th2 and inflammatory milieu of eosinophilic esophagitis (EoE) and assessed alterations in smooth muscle and extracellular matrix function and stiffening. We found that full thickness human esophagus as well as the individual layers of circular and longitudinal muscularis propria developed tension in response to carbachol ex vivo and that mucosa demonstrated squamous cell differentiation. Treatment of mucosa with Th2 and fibrotic cytokines recapitulated the majority of the clinical Eosinophilic Esophagitis Diagnostic Profile (EDP) on fluidic transcriptional microarray. Transforming growth factor-beta-1 (TGFß1) increased gene expression of fibronectin, smooth muscle actin, and phospholamban (p < 0.001). The EoE cocktail also increased stiffness and decreased mucosal compliance, akin to the functional alterations in EoE (p = 0.001). This work establishes a new, transcriptionally intact and physiologically functional human platform to model esophageal tissue responses in EoE.