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Eosinophilic asthma is characterized by frequent exacerbations, poor symptom control and accelerated lung function decline. It is now recognized that the immune response underlying eosinophilic asthma involves a complex network of interconnected pathways from both the adaptive and innate immune systems. Within this response, interleukin-5 (IL-5) plays a central role in eosinophil differentiation, activation and survival and has emerged as a key target for therapies treating severe asthma. The monoclonal antibodies mepolizumab and reslizumab target the ligand IL-5, preventing its interaction with eosinophils; in contrast, benralizumab binds to the IL-5 receptor (IL-5R), preventing IL-5 from binding and leading to substantially greater eosinophil reduction by enhanced antibody-dependent cell-mediated cytotoxicity. Although no direct head-to-head clinical trials of asthma have been published to formally evaluate the clinical significance of these different therapeutic approaches, the potential benefits of partial versus complete eosinophil depletion continue to remain an important area of study and debate. Here, we review the existing real-world and clinical study data of anti-IL-5/anti-IL-5R therapies in severe eosinophilic asthma., (© 2024 The Author(s). Allergy published by European Academy of Allergy and Clinical Immunology and John Wiley & Sons Ltd.)

Eosinophilic gastrointestinal diseases (EGIDs) encompass a group of disorders characterized by an abnormal accumulation of eosinophils in various parts of the gastrointestinal tract. EGIDs present with a wide range of symptoms such as abdominal pain, vomiting, diarrhea, difficulty swallowing, and food impaction. Monoclonal antibodies, targeting inflammatory cytokines or eosinophils, are the next emerging therapy for EGIDs. The only Food and Drug Administration-approved monoclonal antibody is dupilumab, and it has been approved for the treatment of eosinophilic esophagitis (EoE). In this article, the authors will discuss biologics that have been used in the treatment of eosinophilic gastrointestinal diseases., Competing Interests: Disclosures The authors have nothing to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Eosinophil accumulation is a main feature of eosinophilic gastritis (EoG) and is associated with its histologic diagnosis and pathology. However, a recent clinical trial has demonstrated that EoG endoscopic, noneosinophil histologic, and clinical features remain persistent despite complete eosinophil depletion., Objective: Our aim was to examine gastric T-cell composition and associated cytokine levels of patients with EoG following benralizumab-induced eosinophil depletion versus following administration of placebo., Methods: A cohort of subjects with EoG from a subset of subjects who participated in a recent phase 2 benralizumab trial was treated for 12 weeks with administration of 3 doses of benralizumab (anti-IL-5 receptor α antibody [n = 5]) or placebo (n = 4). Single-cell suspensions obtained by gastric biopsy were stimulated with phorbol 12,13-dibutyrate and ionomycin in the presence of brefeldin A and monensin. Harvested cells were fixed, stained, and analyzed by flow cytometry to examine T-cell populations and associated cytokines., Results: Following benralizumab treatment but not placebo, blood and gastric eosinophil levels decreased 16-fold and 10-fold, respectively. Whereas histologic score and features were significantly decreased, no change was observed in endoscopic score and features. Following complete eosinophil depletion with benralizumab, gastric T H 2 cell levels were 3-fold higher than the levels in the patients with EoG who were given placebo; and the levels of associated type 2 cytokine production of IL-4, IL-5, and IL-13 in the benralizumab-treated patients were, respectively, 4-, 5.5-, and 2.5-fold, higher than those in the placebo-treated patients., Conclusion: We have identified a putative positive feedback loop whereby eosinophil depletion results in a paradoxic increase in levels of T H 2 cells and derived cytokines; this finding suggests an explanation for the limited success of eosinophil depletion as monotherapy in eosinophil-associated gastrointestinal disorders., Competing Interests: Disclosure statement Supported by a grant from AstraZeneca. Disclosure of potential conflict of interest: M. E. Rothenberg is a consultant for Pulm One, Spoon Guru, ClostraBio, Serpin Pharm, Allakos, Celldex, Uniquity Bio, Santa Ana Bio, EnZen Therapeutics, Bristol-Myers Squibb, AstraZeneca, Pfizer, GlaxoSmithKline, Regeneron/Sanofi, Revolo Biotherapeutics, and Guidepoint; has an equity interest in the first 9 of the aforementioned companies; receives royalties from reslizumab (Teva Pharmaceuticals), PEESSv2 (Mapi Research Trust), and UpToDate; and is an inventor of patents owned by Cincinnati Children’s Hospital Medical Center. V. A. Mukkada is a consultant for Takeda Sanofi, Regeneron, Phantom, and Allakos and serves on an adjudication board for Alladapt. M. H. Collins is a consultant for Allakos, Arena/Pfizer, AstraZeneca, Calypso, Biotech, EsoCap Biotech, GlaxoSmithKline, Receptos/Celgene/BMS, Regeneron Pharmaceuticals, Robarts Clinical Trials Inc/Alimentiv Inc, and Shire, a Takeda company. The rest of the authors declare that they have no relevant conflicts of interest., (Copyright © 2024 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Nonasthmatic eosinophilic bronchitis is characterized by persistent dry or barely productive cough and bronchial eosinophilia without airway obstruction or bronchial hyperreactivity. It is primarily a chronic disease, in which some patients have clinical and pathophysiological relapses, while others progress to asthma or chronic obstructive pulmonary disease. It accounts for 5% to 30% of cases referred for chronic cough. Exposure to common inhalants and occupational sensitizers has been proposed as a possible cause of the disease, although the etiology and underlying mechanisms are uncertain. Some features are similar to those of asthma, such as airway eosinophilia, inflammatory mediator levels, and airway remodeling. Differences in airway pathophysiology, such as the location of airway inflammation and levels of IL-13 and PGE-2, have been reported. Sputum cell count is the gold standard test for diagnosis, and other biomarkers, such as exhaled nitric oxide, could support the diagnosis. A systematic review of treatments for the disease shows that while inhaled corticosteroids are the primary option, the appropriate dose, the type of corticosteroid, and the duration of treatment remain unknown. Treatment duration is inversely correlated with the relapse rate. Increased doses of inhaled corticosteroids, oral corticosteroids, and leukotriene receptor antagonists are recommended in persistent disease. Anti-IL-5 biologics could be promising in this disease. Studies that investigate biomarkers for diagnosis and prognosis are necessary, as are randomized controlled studies for second-line treatments.

We have created a precisely pegylated IL-2 [SAR-444245 (SAR'245) or pegenzileukin, previously THOR-707] designed for proliferation of target CD8+ T and NK cells for anticancer activity, with minimal expansion of anti-target regulatory CD4+ T cells (Treg) that counter their action, or eosinophils that trigger vascular leak syndrome (VLS). We performed in vivo studies in nonhuman primates (NHP) to monitor the safety of SAR'245, pharmacokinetic profile, and pharmacodynamic parameters including expansion of peripheral CD8+ T and NK cells, and effects on Tregs and eosinophils. Studies included multiple ascending dosing and repeat dosing with different regimens (QW, Q2W, Q3W and Q4W). We also conducted ex vivo studies using human primary cells to further evaluate SAR'245 stimulation of target cells alone and in combination with programmed cell-death 1 (PD-1) checkpoint inhibitors. The pharmacokinetic profile of SAR'245 in NHP demonstrated dose-proportional exposure that was comparable with redosing. It elicited expansion of peripheral CD8+ T and NK cells that was comparable with each dose and with multiple dosing regimens. Once-weekly dosing showed no significant adverse effects, including no hallmark signs of VLS at dosing levels up to 1 mg/kg. Ex vivo, SAR'245 enhanced T-cell receptor responses alone and in combination with PD-1 inhibitors without inducing cytokines associated with cytokine release syndrome or VLS. Results support the clinical development of SAR'245 as a drug candidate for the treatment of solid tumors, alone or in combination with PD-1 inhibitory agents., Significance: SAR-444245 (SAR'245, pegenzileukin) is an extended half-life IL-2 that targets effector CD8+ T and NK cells, with little effect on regulatory T cells. We show that in the nonhuman primate model that closely approximates human immune function and response to IL-2, SAR'245 selectively activates CD8+ T and NK effectors without significant serious side effects (vascular leak syndrome or cytokine release syndrome), suggesting its potential for the treatment of solid tumors in humans., (©2024 The Authors; Published by the American Association for Cancer Research.)

The role of eosinophils in airway inflammation and asthma pathogenesis is well established, with raised eosinophil counts in blood and sputum associated with increased disease severity and risk of asthma exacerbation. Conversely, there is also preliminary evidence suggesting antiviral properties of eosinophils in the airways. These dual roles for eosinophils are particularly pertinent as respiratory virus infections contribute to asthma exacerbations. Biologic therapies targeting key molecules implicated in eosinophil-associated pathologies have been approved in patients with severe asthma and, therefore, the effects of depleting eosinophils in a clinical setting are of considerable interest. This review discusses the pathological and antiviral roles of eosinophils in asthma and exacerbations. We also highlight the significant reduction in asthma exacerbations seen with biologic therapies, even at the height of the respiratory virus season. Furthermore, we discuss the implications of these findings in relation to the role of eosinophils in inflammation and antiviral responses to respiratory virus infection in asthma., (© 2024 The Author(s). Allergy published by European Academy of Allergy and Clinical Immunology and John Wiley & Sons Ltd.)

The Consortium of Eosinophilic Gastrointestinal disease Researchers (CEGIR) and The International Gastrointestinal Eosinophil Researchers (TIGERs) organized a daylong symposium at the 2024 annual meeting of the American Academy of Allergy, Asthma & Immunology. The symposium featured new discoveries in basic and translational research as well as debates on the mechanisms and management of eosinophilic gastrointestinal diseases. Updates on recent clinical trials and consensus guidelines were also presented. We summarize the updates on eosinophilic gastrointestinal diseases presented at the symposium., Competing Interests: Disclosure statement Supported by U54AI117804 (Consortium of Eosinophilic Gastrointestinal Disease Researchers), which is part of the Rare Disease Clinical Research Network (RDCRN), an initiative of the Office of Rare Disease Research (ORDR), National Center for Advancing Translational Sciences (NCATS), and is funded through collaboration between National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH)/National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NCATS, and in part by the Division of Intramural Research, NIAID/NIH. CEGIR is also supported by patient advocacy groups including American Partnership for Eosinophilic Disorders (APFED), Campaign Urging Research for Eosinophilic Diseases (CURED), and Eosinophilic Family Coalition (EFC). As a member of the RDCRN, CEGIR is also supported by its Data Management and Coordinating Center (DMCC) (U2CTR002818). Funding support for the DMCC is provided by the NCATS and the National Institute of Neurological Disorders and Stroke (NINDS). B.L.W. was funded by NIH/NIAID (K23AI158813). E.M.A. was funded by the NIH (KL2TR002552, K12TR004410). S.S.A. was funded by NIH/NIDDK (R56AI092135). S.J.A. was funded by NIH/National Heart, Lung, and Blood Institute (NHLBI) (R01HL153170). D.A.H. was directly supported by the Hartwell Foundation, the Food Allergy Fund, and a faculty development award from the American Academy of Allergy, Asthma & Immunology. Allergy research in the Hill laboratory was supported by NIH/NHLBI (R01HL162715) and the Children’s Hospital of Philadelphia Research Institute. J.W.C. was supported by the NIH (K23DK129784). F.L.K. was funded by APFED HOPE Pilot Grant 2023 and NIH/NIAID K23AI171085. M.A.R. was funded by the NIH (K08AI148456). L.A.S. was supported by NIH/NIAID (R01AI168134). The contents are those of the authors and do not necessarily represent the official views or an endorsement by the NIH or other funders. None of the funding sources had a role in the design or conduct of the study. Disclosure of potential conflict of interest: B. L. Wright reports in-kind support from Regeneron in the form of study drug (dupilumab and placebo) for a clinical trial of milk oral immunotherapy. J. P. Abonia reports receipt of payment or honoraria for lectures from Takeda Global Research and Development; participation on a data safety monitoring board for OctaPharma USA; and receipt of grants or contracts from Cures Within Reach and Celgene. E. M. Abud is coinventor of patent WO/2018/160496 (microglia differentiation and use); serves as advisory board member and consulting agreements with StemPharm and Neucyte; and reports advisory board participation for Amgen and AstraZeneca. S. S. Aceves is coinventor of oral viscous budesonide, patented by the University of California, San Diego, and licensed by Takeda (oral budesonide suspension); has acted as speaker for Regeneron/Sanofi; and has received research funding from Bristol Myers Squibb. S. J. Ackerman is chief science officer and executive board member of EnteroTrack; has received patents on the Esophageal String Test (EST); has consulted for Areteia Pharmaceuticals; and has participated on the medical advisory panel of the American Partnership for Eosinophilic Disorders (APFED). M. Braskett reports acting as scientific advisor to Bryn Pharma; and receipt of royalties from UpToDate. J. W. Chang reports consulting for Regeneron/Sanofi, Takeda, and Bristol Myers Squibb. M. Chehade reports consulting for Regeneron/Sanofi, Adare/Ellodi, AstraZeneca, Bristol Myers Squibb, Allakos, Shire/Takeda, Phathom, and Recludix Pharma; and receipt of research funding from Regeneron, Allakos, AstraZeneca, Adare/Ellodi, Bristol Myers Squibb, Danone, and Shire/Takeda. G. M. Constantine reports speaker honoraria from PeerView CME. C. M. Davis reports research funding from NIH/NIAID, DBV, Regeneron, AstraZeneca, Takeda, and Allergenis; and educational funding from Genentech. E. S. Dellon reports research funding from Adare/Ellodi, Allakos, Arena/Pfizer, AstraZeneca, Eupraxia, Ferring, GSK, Meritage, Miraca, Nutricia, Celgene/Receptos/BMS, Regeneron, Revolo, and Shire/Takeda; consulting for Abbott, AbbVie, Adare/Ellodi, Aimmune, Akesobio, Alfasigma, ALK, Allakos, Amgen, Apollo, Aqilion, Arena/Pfizer, Aslan, AstraZeneca, Avir, Biorasi, Bryn, Calypso, Celgene/Receptos/BMS, Celldex, Eli Lilly, EsoCap, Eupraxia, Dr Falk Pharma, Ferring, GSK, Gossamer Bio, Holoclara, Invea, Knightpoint, Landos, LucidDx, Morphic, Nexstone Immunology/Uniquity, Nutricia, Parexel/Calyx, Phathom, Regeneron, Revolo, Robarts/Alimentiv, Salix, Sanofi, Shire/Takeda, Target RWE, and Upstream Bio; and receipt of educational grants from Allakos, Aqilion, Holoclara, and Invea. R. Durban reports consulting for Sanofi, AstraZeneca, Reckitt/Mead Johnson Nutrition, Abbott Nutrition, and Nutricia North America. D. A. Hill has received a patent related to the utilization of food-specific T-cell responses for the diagnosis and management of EoE. E. T. Jensen reports consulting fees from Regeneron, Jazz Pharmaceuticals, and TARGET-RWE. A. Kewalramani reports sitting on the Sanofi Mid-Atlantic Regional Respiratory Field medical advisory board. P. Khoury and A. D. Klion report royalties from UpToDate. F. L. Kuang reports research funding from AstraZeneca. E. C. McGowan reports funding from NIH/NIAID and American College of Gastroenterology; and consulting for Regeneron/Sanofi and Takeda. J. M. Spergel reports grant support from the NIH, Regeneron/Sanofi, and Novartis; and has consulted for Regeneron/Sanofi, Allakos, Readysetfood, Novartis, and Bristol Myers Squibb. A. M. Uchida reports consulting for Regeneron/Sanofi, Takeda, and AstraZeneca. J. B. Wechslerc reports consulting for Allakos, Ellodi, Regeneron/Sanofi/Genzyme, Bristol Myers Squibb, Invea Therapeutics, CellDex, and AstraZeneca; and clinical trial/research funding from Allakos and Regeneron/Sanofi. R. D. Pesek reports consulting for Regeneron. The rest of the authors declare that they have no relevant conflicts of interest., (Copyright © 2024 American Academy of Allergy, Asthma & Immunology. All rights reserved.)

Background: Basal cell hyperplasia is commonly observed in nasal polyp epithelium of eosinophilic chronic rhinosinusitis (eCRS). We examined the function and mechanisms of basal cell hyperplasia in the pathophysiology of eCRS., Methods: We found that normal human bronchial epithelial (NHBE) cells obtained basal cell characteristics when cultured with PneumaCult™-Ex Plus Medium. Most of the cells passaged three times expressed basal cell surface markers CD49f and CD271 by flow cytometry, and basal cell nuclear marker p63 by immunohistochemical staining. We named these NHBE cells with basal cell characteristics cultured Basal-like cells (cBC), and NHBE cells cultured with BEGM™ cultured Epithelial cells (cEC). The characteristics of cBC and cEC were examined and compared by RNA sequencing, RT-PCR, ELISA, and cell proliferation studies., Results: RNA sequencing revealed that cBC showed higher gene expression of thymic stromal lymphopoietin (TSLP), IL-8, TLR3, and TLR4, and lower expression of PAR-2 compared with cEC. The mRNA expression of TSLP, IL-8, TLR3, and TLR4 was significantly increased in cBC, and that of PAR-2 was significantly increased in cEC by RT-PCR. Poly(I:C)-induced TSLP production and LPS-induced IL-8 production were significantly increased in cBC. IL-4 and IL-13 stimulated the proliferation of cBC. Finally, the frequency of p63-positive basal cells was increased in nasal polyp epithelium of eCRS, and Ki67-positive proliferating cells were increased in p63-positive basal cells., Conclusions: Type 2 cytokines IL-4 and IL-13 induce basal cell hyperplasia, and basal cells exacerbate type 2 inflammation by producing TSLP in nasal polyp of eCRS., (Copyright © 2024 Japanese Society of Allergology. Published by Elsevier B.V. All rights reserved.)

Immune activation status determines non-small cell lung cancer (NSCLC) prognosis, with reported positive/negative associations for T helper type 2 (TH2) responses, including allergen-specific IgE and eosinophils. Our study seeks to explore the potential impact of these comorbid immune responses on the survival rates of patients with NSCLC. Our retrospective study used data from the Data Warehouse of the German Center for Lung Research (DZL) and Lung Biobank at Thoraxklinik Heidelberg. We estimated the association of blood eosinophilia and neutrophilia on survival rates in an inflammatory cohort of 3143 patients with NSCLC. We also tested sensitization to food and inhalants and high-sensitivity C-reactive protein (hs-CRP) in a comorbidity cohort of 212 patients with NSCLC. Finally, we estimated the infiltration of immune-relevant cells including eosinophils, T-cells, and mast cells in a tissue inflammatory sub-cohort of 60 patients with NSCLC. Sensitization to at least one food or inhalant (sIgE) was higher in patients with adenocarcinoma (adeno-LC) than the non-adenocarcinoma (non-adeno-LC). Furthermore, hs-CRP was higher in non-adeno-LC compared with adeno-LC. Peripheral inflammation, particularly eosinophilia and neutrophilia, was associated with poor survival outcomes in NSCLC with a clear difference between histological subgroups. Finally, blood eosinophilia was paralleled by significant eosinophil infiltration into the peritumoral tissue in the lung. This study provides novel perspectives on the crucial role of peripheral inflammation, featuring eosinophilia and neutrophilia, with overall survival, underscoring distinctions between NSCLC subgroups (adeno-LC vs. non-adeno-LC). Peripheral eosinophilia enhances eosinophil infiltration into tumors. This sheds light on the complex interplay between inflammation, eosinophil infiltration, and NSCLC prognosis among various histological subtypes. Further studies are required to underscore the role of eosinophils in NSCLC among different histological subgroups and their role in shaping the tumor microenvironment.

Background: Epithelial remodeling is a prominent feature of eosinophilic chronic rhinosinusitis with nasal polyps (eCRSwNP), and infiltration of M2 macrophages plays a pivotal role in the pathogenesis of eCRSwNP, but the underlying mechanisms remain undefined., Objective: We sought to investigate the role of ALOX15 + M2 macrophages in the epithelial remodeling of eCRSwNP., Methods: Digital spatial transcriptomics and single-cell sequencing analyses were used to characterize the epithelial remodeling and cellular infiltrate in eCRSwNP. Hematoxylin and eosin staining, immunohistochemical staining, and immunofluorescence staining were used to explore the relationship between ALOX15 + M2 (CD68 + CD163 + ) macrophages and epithelial remodeling. A coculture system of primary human nasal epithelial cells (hNECs) and the macrophage cell line THP-1 was used to determine the underlying mechanisms., Results: Spatial transcriptomics analysis showed the upregulation of epithelial remodeling-related genes, such as Vimentin and matrix metalloproteinase 10, and enrichment of epithelial-mesenchymal transition (EMT)-related pathways, in the epithelial areas in eCRSwNP, with more abundance of epithelial basal, goblet, and glandular cells. Single-cell analysis identified that ALOX15 + , rather than ALOX15 - , M2 macrophages were specifically highly expressed in eCRSwNP. CRSwNP with high ALOX15 + M2 THP-1-IL-4+IL-13 macrophages had more obvious epithelial remodeling features and increased genes associated with epithelial remodeling and integrity of epithelial morphology versus that with low ALOX15 + M2 THP-1-IL-4+IL-13 macrophages. IL-4/IL-13-polarized M2 THP-1-IL-4+IL-13 macrophages upregulated expressions of EMT-related genes in hNECs, including Vimentin, TWIST1, Snail, and ZEB1. ALOX15 inhibition in M2 THP-1-IL-4+IL-13 macrophages resulted in reduction of the EMT-related transcripts in hNECs. Blocking chemokine (C-C motif) ligand 13 signaling inhibited M2 THP-1-IL-4+IL-13 macrophage-induced EMT alteration in hNECs., Conclusions: ALOX15 + M2 macrophages are specifically increased in eCRSwNP and may contribute to the pathogenesis of epithelial remodeling via production of chemokine (C-C motif) ligand 13., (Copyright © 2024 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Competing Interests: None.

Summary: Eosinophil-associated diseases (EADs) refer to heterogeneous conditions in which eosinophils are believed to play critical pathological roles. They encompass common respiratory conditions, such as asthma, chronic rhinosinusitis with nasal polyps (CRSwNP), less common primary eosinophilic disorders of gastrointestinal tract, and rare conditions including eosinophilic granulomatosis with polyangiitis (EGPA) and hypereosinophilic syndrome (HES). A literature search was carried out in January 2024 in the MEDLINE and Scopus databases using the PubMed search engine (PubMed, National Library of Medicine, Bethesda, MD). We focused on blood eosinophilia and hypereosinophilia. A diagnostic workup is proposed. From allergist's point of view, we focused the review on 4 groups of eosinophilic disorders of specific interest. Our increased understanding of type 2 inflammation and biology has recently led to development of highly effective precision targeted therapies that are now approved for a growing number of eosinophilic disorders. Novel targeted biologics have a major impact on treatment strategies and have resulted in major advances in our understanding of the pathogenesis of these disorders. In the context of EADs, according to the heterogeneity of eosinophilic disorders a multidisciplinary approach should be adopted. Allergists and Clinical Immunologists play an important role as they have a clear understanding of the eosinophilic inflammation and the role of cytokines and are trained to recognize and characterize type 2 (T2) inflammation and its associated pathologies.

Background: Previous studies implied that local M2 polarization of macrophage promoted mucosal edema and exacerbated T H 2 type inflammation in chronic rhinosinusitis with nasal polyps (CRSwNP). However, the specific pathogenic role of M2 macrophages and the intrinsic regulators in the development of CRS remains elusive., Objective: We sought to investigate the regulatory role of SIRT5 in the polarization of M2 macrophages and its potential contribution to the development of CRSwNP., Methods: Real-time reverse transcription-quantitative PCR and Western blot analyses were performed to examine the expression levels of SIRT5 and markers of M2 macrophages in sinonasal mucosa samples obtained from both CRS and control groups. Wild-type and Sirt5-knockout mice were used to establish a nasal polyp model with T H 2 inflammation and to investigate the effects of SIRT5 in macrophage on disease development. Furthermore, in vitro experiments were conducted to elucidate the regulatory role of SIRT5 in polarization of M2 macrophages., Results: Clinical investigations showed that SIRT5 was highly expressed and positively correlated with M2 macrophage markers in eosinophilic polyps. The expression of SIRT5 in M2 macrophages was found to contribute to the development of the disease, which was impaired in Sirt5-deficient mice. Mechanistically, SIRT5 was shown to enhance the alternative polarization of macrophages by promoting glutaminolysis., Conclusions: SIRT5 plays a crucial role in promoting the development of CRSwNP by supporting alternative polarization of macrophages, thus providing a potential target for CRSwNP interventions., Competing Interests: Disclosure statement Supported by the National Natural Science Foundation of China (grants U23A20439 to H.-H.L. and 82271136 to WW.R.) and the Shanghai Commissions of Health (grant GWVI-11.2-YQ53 to C.-Q.L.). Disclosure of potential conflict of interest: The authors declare that they have no relevant conflicts of interest., (Copyright © 2024. Published by Elsevier Inc.)

Purpose of Review: This review aims to provide an overview of the current understanding of eosinophilic gastrointestinal disorders (EGIDs) and the role of the epithelium in influencing disease pathogenesis to inform and devise future therapeutic strategies., Recent Findings: Changes in epithelial cell structure, functions, and integrity are observed in EGIDs. In eosinophilic esophagitis (EoE), the esophageal epithelium has been shown to play key roles in perpetuating the inflammatory response in EoE through the expression of pro-inflammatory cytokines and immunological cell-surface proteins. Similar mechanisms appear to exist in the other EGIDs, including eosinophilic gastritis (EoG), eosinophilic enteritis (EoN), and eosinophilic colitis (EoC). Because of the increasing rarity of each non-EoE EGID, research focusing on how the epithelium is modulating disease in each lower gastrointestinal compartment is still in its rudimentary stages., Summary: While there has been significant progress in understanding the role of the epithelium in EoE, further research is needed to obtain a better understanding of the mechanisms mediating epithelial-immune crosstalk in non-EoE EGIDs. Using EoE-epithelial cell research to inform future EGID investigations could lead to the development of new therapeutic interventions, such as targeted therapies to restore epithelial barrier function and reduce inflammation, to improve rare disease-patient quality of life., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Introduction: Chronic inflammation of the gastrointestinal tissues underlies gastrointestinal inflammatory disorders, leading to tissue damage and a constellation of painful and debilitating symptoms. These disorders include inflammatory bowel diseases (Crohn's disease and ulcerative colitis), and eosinophilic disorders (eosinophilic esophagitis and eosinophilic duodenitis). Gastrointestinal inflammatory disorders can often present with overlapping symptoms necessitating the use of invasive procedures to give an accurate diagnosis., Methods: This study used peripheral blood mononuclear cells from individuals with Crohn's disease, ulcerative colitis, eosinophilic esophagitis, and eosinophilic duodenitis to better understand the alterations to the transcriptome of individuals with these diseases and identify potential markers of active inflammation within the peripheral blood of patients that may be useful in diagnosis. Single-cell RNA-sequencing was performed on peripheral blood mononuclear cells isolated from the blood samples of pediatric patients diagnosed with gastrointestinal disorders, including Crohn's disease, ulcerative colitis, eosinophilic esophagitis, eosinophilic duodenitis, and controls with histologically healthy gastrointestinal tracts., Results: We identified 730 (FDR < 0.05) differentially expressed genes between individuals with gastrointestinal disorders and controls across eight immune cell types., Discussion: There were common patterns among GI disorders, such as the widespread upregulation of MTRNR2L8 across cell types, and many differentially expressed genes showed distinct patterns of dysregulation among the different gastrointestinal diseases compared to controls, including upregulation of XIST across cell types among individuals with ulcerative colitis and upregulation of Th2-associated genes in eosinophilic disorders. These findings indicate both overlapping and distinct alterations to the transcriptome of individuals with gastrointestinal disorders compared to controls, which provide insight as to which genes may be useful as markers for disease in the peripheral blood of patients., Competing Interests: The work reported herein was conducted while VS was affiliated with CMKC. VS is employed by Ironwood Pharmaceuticals. CV is employed by KCAS Bioanalytical & Biomarker Services. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Keever-Keigher, Harvey, Williams, Vyhlidal, Ahmed, Johnston, Louiselle, Grundberg, Pastinen, Friesen, Chevalier, Smail and Shakhnovich.)

Eosinophils are key effector cells mediating airway inflammation and exacerbation in patients with severe eosinophilic asthma. They are present in increased numbers and activation states in the airway mucosa and lumen. Interleukin-5 (IL-5) is the key eosinophil growth factor that is thought to play a role in eosinophil priming and activation. However, the mechanism of these effects is still not fully understood. The anti-IL-5 antibody mepolizumab reduces eosinophil counts in the airway modestly but has a large beneficial effect on the frequency of exacerbations of severe eosinophilic asthma, suggesting that reduction in eosinophil priming and activation is of central mechanistic importance. In this study, we used the therapeutic effect of mepolizumab and single-cell ribonucleic acid sequencing to investigate the mechanism of eosinophil priming and activation by IL-5. We demonstrated that IL-5 is a dominant driver of eosinophil priming and plays multifaceted roles in eosinophil function. It enhances eosinophil responses to other stimulators of migration, survival, and activation by activating phosphatidylinositol-3-kinases, extracellular signal-regulated kinases, and p38 mitogen-activated protein kinases signaling pathways. It also enhances the pro-fibrotic roles of eosinophils in airway remodeling via transforming growth factor-β pathway. These findings provide a mechanistic understanding of eosinophil priming in severe eosinophilic asthma and the therapeutic effect of anti-IL-5 approaches in the disease., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Chronic rhinosinusitis (CRS) is a common inflammatory condition affecting the nasal and paranasal sinus mucosa, often accompanied by olfactory dysfunction. Eosinophilic CRS with nasal polyps (ECRSwNP) is a subtype of CRS characterized by eosinophilic infiltration. Animal models for ECRSwNP with olfactory dysfunction are necessary for exploring potential therapeutic strategies., Objective: The aim of this study was to establish a mouse model of ECRSwNP combined with olfactory dysfunction in a shorter time frame using intranasal ovalbumin and Aspergillus protease (AP) administration. The efficacy of the model was validated by evaluating sinonasal inflammation, cytokine levels, olfactory function, and neuroinflammation in the olfactory bulb., Methods: Male BALB/c mice were intranasally administered ovalbumin and AP for 6 and 12 weeks to induce ECRSwNP. The resultant ECRSwNP mouse model underwent histologic assessment, cytokine analysis of nasal lavage fluid, olfactory behavioral tests, and gene expression profiling to identify neuroinflammatory markers within the olfactory bulb., Results: The developed mouse model exhibited substantial eosinophil infiltration, increased levels of inflammatory cytokines in nasal lavage fluid, and confirmed olfactory dysfunction through behavioral assays. Furthermore, olfactory bulb inflammation and reduced mature olfactory sensory neurons were observed in the model., Conclusion: This study successfully established a validated mouse model of ECRSwNP with olfactory dysfunction within a remarkably short span of 6 weeks, providing a valuable tool for investigating the pathogenesis and potential therapies for this condition. The model offers an efficient approach for future research in CRS with nasal polyps and olfactory dysfunction., (Copyright © 2024 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Eosinophilic gastrointestinal disorders (EGIDs) are a group of conditions characterized by an abnormal accumulation of eosinophils in the gastrointestinal tract, leading to inflammation and tissue damage. Regulatory cells are a subset of immune cells that are crucial in maintaining the balance of the immune system and preventing the occurrence of autoimmune diseases. In EGIDs, regulatory cells are believed to play a key role in controlling the immune response and overseeing the growth and activation of eosinophils in the gastrointestinal tract. There is evidence indicating that regulatory T cells (Tregs) and regulatory eosinophils may play a role in suppressing the inflammatory response in EGIDs. Regulatory eosinophils are a subgroup of eosinophils that possess an anti-inflammatory role. Recent studies have shown that enhancing the number or effectiveness of regulatory eosinophils can reduce the severity of EGIDs. Regulatory eosinophils dampen inflammation through their regulatory mediators, such as galectin-10 and growth factor beta (TGF-β), which promote Treg expansion and inhibit effector T cell function. Further research on regulatory cells in EGIDs may have significant implications for the advancement of novel therapies for these uncommon and intricate disorders. The aim of this review is to provide complete view of the immune responses connected to EGIDs, examine the regulatory cells that control these responses, and evaluate their potential as therapeutic targets for EGID treatment., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer AA declared a shared affiliation with all the authors at the time of review., (Copyright © 2024 Kheshtchin, Kanannejad, Ghahramani, Esmaeilzadeh and Sepahi.)

Eosinophil sombrero vesicles are large tubular carriers resident in the cytoplasm of human eosinophils, identifiable by transmission electron microscopy, and important for immune mediator transport. Increased formation of sombrero vesicles occurs in activated eosinophils in vitro and in vivo. In tissue sites of eosinophilic cytolytic inflammation, extracellular eosinophil sombrero vesicles are noted, but their frequency and significance in eosinophil-associated diseases remain unclear. Here, we performed comprehensive quantitative transmission electron microscopy analyses and electron tomography to investigate the numbers, density, integrity, and 3-dimensional structure of eosinophil sombrero vesicles in different biopsy tissues from 5 prototypic eosinophil-associated diseases (eosinophilic chronic rhinosinusitis/nasal sinuses, ulcerative colitis/intestines, hypereosinophilic syndrome/skin, dermatitis/skin, and schistosomiasis/rectum). The morphology of extracellular eosinophil sombrero vesicles was also compared with that of cytoplasmic eosinophil sombrero vesicles, isolated by subcellular fractionation from peripheral blood eosinophils. We demonstrated that (i) eosinophil cytolysis, releasing intact sombrero vesicles and membrane-bound granules, is a consistent event in all eosinophil-associated diseases; (ii) eosinophil sombrero vesicles persist intact even after complete disintegration of all cell organelles, except granules (late cytolysis); (iii) the eosinophil sombrero vesicle population, composed of elongated, curved, and typical sombreros, and the eosinophil sombrero vesicle 3-dimensional architecture, diameter, and density remain unchanged in the extracellular matrix; (iv) free eosinophil sombrero vesicles closely associate with extracellular granules; and (v) free eosinophil sombrero vesicles also associate with externalized chromatin during eosinophil ETosis. Remarkably, eosinophil sombrero vesicles appeared on the surface of other cells, such as plasma cells. Thus, eosinophil cytolysis/ETosis can secrete intact sombrero vesicles, alongside granules, in inflamed tissues of eosinophil-associated diseases, potentially serving as propagators of eosinophil immune responses after cell death., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for Leukocyte Biology.)

Upon encountering allergens, CD4 + T cells differentiate into IL-4-producing Th2 cells in lymph nodes, which later transform into polyfunctional Th2 cells producing IL-5 and IL-13 in inflamed tissues. However, the precise mechanism underlying their polyfunctionality remains elusive. In this study, we elucidate the pivotal role of NRF2 in polyfunctional Th2 cells in murine models of allergic asthma and in human Th2 cells. We found that an increase in reactive oxygen species (ROS) in immune cells infiltrating the lungs is necessary for the development of eosinophilic asthma and polyfunctional Th2 cells in vivo. Deletion of the ROS sensor NRF2 specifically in T cells, but not in dendritic cells, significantly abolished eosinophilia and polyfunctional Th2 cells in the airway. Mechanistically, NRF2 intrinsic to T cells is essential for inducing optimal oxidative phosphorylation and glycolysis capacity, thereby driving Th2 cell polyfunctionality independently of IL-33, partially by inducing PPARγ. Treatment with an NRF2 inhibitor leads to a substantial decrease in polyfunctional Th2 cells and subsequent eosinophilia in mice and a reduction in the production of Th2 cytokines from peripheral blood mononuclear cells in asthmatic patients. These findings highlight the critical role of Nrf2 as a spatial and temporal metabolic hub that is essential for polyfunctional Th2 cells, suggesting potential therapeutic implications for allergic diseases., Competing Interests: Competing interests statement:The authors declare no competing interest.

Background: This study aimed to clarify the diagnostic and predictive factors for perennial allergic rhinitis (PAR) onset in children by analyzing the results of the Chiba High-risk Birth Cohort for Allergy study, which examined newborns with a family history of allergies., Methods: Overall, 306 pregnant women were recruited. Their newborns were examined by otolaryngologists and pediatric allergists at 1, 2, and 5 years of age. Participants with clinical and laboratory data available at all consultation points were considered eligible., Results: Among 187 eligible participants, the prevalence rates of PAR were 2.1%, 4.3%, and 24.1% at 1, 2, and 5 years of age, respectively. AR-specific nasal local findings and eosinophils in nasal smear were observed in a substantial number of patients with PAR at 1 and 2 years of age. Factors present up to 2 years of age that were associated with PAR onset at 5 years of age, in descending order, were as follows: sensitization to house dust mites (HDM), nasal eosinophilia, and sensitization to cat dander. In 44 cases with HDM sensitization, nasal eosinophilia up to 2 years of age achieved a sensitivity of 76.0% and a specificity of 73.7% for predicting PAR onset at 5 years., Conclusions: Rhinitis findings and nasal eosinophilia are useful auxiliary diagnostic items for pediatric PAR. Sensitization to HDM and nasal eosinophilia were the most influential factors associated with future PAR onset. A combination of these factors may facilitate the prediction of PAR onset., (Copyright © 2024 Japanese Society of Allergology. Published by Elsevier B.V. All rights reserved.)

Eosinophilic inflammation is primarily characterized by type 2 immune responses against parasitic organisms. In the contemporary human being especially in developed countries, eosinophilic inflammation is strongly associated with allergic/sterile inflammation, and constitutes an undesired immune reaction. This situation is in stark contrast to neutrophilic inflammation, which is indispensable for the host defense against bacterial infections. Among eosinophilic inflammatory disorders, massive accumulation of eosinophils within mucus is observed in certain cases, and is often linked to the distinctive clinical finding of mucus with high viscosity. Eosinophilic mucus is found in a variety of diseases, including chronic allergic keratoconjunctivitis, chronic rhinosinusitis encompassing allergic fungal sinusitis, eosinophilic otitis media, eosinophilic sialodochitis, allergic bronchopulmonary aspergillosis/mycosis, eosinophilic plastic bronchitis, and eosinophilic asthma. In these pathological conditions, chronic inflammation and tissue remodeling coupled with irreversible organ damage due to persistent adhesion of toxic substances and luminal obstruction may impose a significant burden on the body. Eosinophils aggregate in the hyperconcentrated mucus together with cell-derived crystals, macromolecules, and polymers, thereby affecting the biophysical properties of the mucus. This review focuses on the clinically significant challenges of mucus and discusses the consequences of activated eosinophils on the mucosal surface that impact mucus and persistent inflammation., (Copyright © 2024 Japanese Society of Allergology. Published by Elsevier B.V. All rights reserved.)

Background/aims: Sensitization to staphylococcal superantigens (SAgs) could contribute to asthma severity. However, its relevance with eosinophilic phenotype has not yet been clarified. This study aimed to investigate associations between serum specific IgE levels to SAg and eosinophilic airway inflammation in adult asthmatics., Methods: The serum specific IgE levels to 3 SAgs, including staphylococcal enterotoxin A (SEA) and B (SEB), and toxic shock syndrome toxin-1 (TSST-1) were measured by ImmunoCAP in 230 adult asthmatic patients and 50 healthy controls (HCs). Clinical characteristics and laboratory parameters, including serum total/free IgE, and 2 eosinophil-activation markers, eosinophil cationic protein (ECP), and eosinophil-derived neurotoxin (EDN), were analyzed according to blood eosinophil counts (BEC; 150 cells/μL) and serum specific IgE levels to 3 SAgs (0.35 kU/L)., Results: Asthmatic patients showed higher serum specific IgE levels to 3 SAgs than HCs (p < 0.05 for all). The serum total/clinfree IgE levels were significantly higher in asthmatics with positive IgE responses to 3 SAgs than those without (p < 0.05 for all). There were no significant differences in clinical parameters including age, asthma severity, comorbidities, or smoking according to IgE responses to 3 SAgs. Patients with positive IgE responses to SEB (not to SEA/TSST-1) had higher serum specific IgE levels to house dust mites and ECP/EDN as well as higher BEC with positive correlations between serum SEB-specific IgE levels and BEC/ECP/EDN (p < 0.05 for all)., Conclusion: These findings suggest that serum SEB-specific IgE levels could contribute to eosinophil activation as well as IgE production in adult asthma.

Allergic airway inflammation results from uncontrolled immune responses to environmental Ags. Although it is well established that allergic immune responses exhibit a high degree of diversity, driven by primary effector cell types such as eosinophils, neutrophils, or CD4 T cells with distinct effector signatures, the mechanisms responsible for such pathogenesis remain elusive. Foxp3+ regulatory T cells (Tregs) are essential immune regulators during chronic inflammation, including allergic airway inflammation. Emerging evidence suggests that Tregs infiltrating inflamed tissues exhibit distinct phenotypes dependent on the specific tissue sites and can display heterogeneity and tissue residency. Whether diverse allergic airway inflammatory responses influence infiltrating Treg heterogeneity or Treg lung residency has not been explored. We employed an unbiased single-cell RNA sequencing approach to investigate lung-infiltrating Tregs in models of eosinophilic and neutrophilic airway inflammation. We found that lung-infiltrating Tregs are highly heterogeneous, and that Tregs displaying lung-resident phenotypes are significantly different depending on the types of inflammation. Treg expression of ST2, a receptor for alarmin IL-33, was predominantly associated with eosinophilic inflammation and tissue residency. Nevertheless, Treg-specific ST2 deficiency did not affect the development of eosinophilic allergic inflammation or the generation of lung-resident Tregs. These results uncover a stark heterogeneity among Tregs infiltrating the lungs during allergic airway inflammation. The results indicate that varying types of inflammation may give rise to phenotypically distinct lung-resident Tregs, underscoring a (to our knowledge) novel mechanism by which inflammatory cues may shape the composition of infiltrating Tregs, allowing them to regulate inflammatory responses through tissue-adapted mechanisms., (Copyright © 2024 by The American Association of Immunologists, Inc.)

Objective: Angiotensin-(1-7) [Ang-(1-7)] is a pro-resolving mediator. It is not known whether the pro-resolving effects of Ang-(1-7) are sustained and protect the lung from a subsequent inflammatory challenge. This study sought to investigate the impact of treatment in face of a second allergic or lipopolysaccharide (LPS) challenge., Methods: Mice, sensitized and challenged with ovalbumin (OVA), received a single Ang-(1-7) dose at the peak of eosinophilic inflammation, 24 h after the final OVA challenge. Subsequently, mice were euthanized at 48, 72, 96, and 120 h following the OVA challenge, and cellular infiltrate, inflammatory mediators, lung histopathology, and macrophage-mediated efferocytic activity were evaluated. The secondary inflammatory stimulus (OVA or LPS) was administered 120 h after the last OVA challenge, and subsequent inflammatory analyses were performed., Results: Treatment with Ang-(1-7) resulted in elevated levels of IL-10, CD4 + Foxp3 + , Mres in the lungs and enhanced macrophage-mediated efferocytic capacity. Moreover, in allergic mice treated with Ang-(1-7) and then subjected to a secondary OVA challenge, inflammation was also reduced. Similarly, in mice exposed to LPS, Ang-(1-7) effectively prevented the lung inflammation., Conclusion: A single dose of Ang-(1-7) resolves lung inflammation and protect the lung from a subsequent inflammatory challenge highlighting its potential therapeutic for individuals with asthma., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Background: The PI3K/Akt/mTOR pathway and autophagy are important physiological processes. But their roles in eCRSwNP remains controversial., Methods: In this study, we used the eCRSwNP mouse model, PI3K/Akt/mTOR pathway inhibitors, and autophagy inhibitors and activators to investigate the regulatory effects of the PI3K/Akt/mTOR pathway on autophagy, and their effects on eosinophilic inflammation, and tissue remodeling. The role of ILC2s in eCRSwNP was also studied, and the relationship between ILC2s and autophagy was preliminarily determined., Results: Our results show that eosinophilic inflammation in eCRSwNP mice could be inhibited by promoting the autophagy; otherwise, eosinophilic inflammation could be promoted. Meanwhile, inhibition of the PI3K/Akt/mTOR pathway can further promote autophagy and inhibit eosinophilic inflammation. Meanwhile, inhibiting the PI3K/Akt/mTOR pathway and promoting autophagy can reduce the number of ILC2s and the severity of tissue remodeling in the nasal polyps of eCRSwNP mice., Conclusions: We conclude that the PI3K/Akt/mTOR pathway plays roles in eosinophilic inflammation and tissue remodeling of eCRSwNP, in part by regulating the level of autophagy. The downregulation of autophagy is a pathogenesis of eCRSwNP; therefore, the recovery of normal autophagy levels might be a new target for eCRSwNP therapy. Furthermore, autophagy might inhibit eosinophilic inflammation and tissue remodeling, in part by reducing the number of ILC2s., (© 2024 The Author(s). Immunity, Inflammation and Disease published by John Wiley & Sons Ltd.)

Eosinophilic gastrointestinal diseases (EGIDs) are a group of diseases characterized by selective eosinophil infiltration of the gastrointestinal (GI) tract in the absence of other causes of eosinophilia. These diseases are generally driven by type 2 inflammation, often in response to food allergen exposure. Among all EGIDs, the clinical presentation often includes a history of atopic disease with a variety of GI symptoms. EGIDs are traditionally separated into eosinophilic esophagitis (EoE) and non-EoE EGIDs. EoE is relatively better understood and now associated with clinical guidelines and 2 US Food and Drug Administration-approved treatments, whereas non-EoE EGIDs are rarer and less well-understood diseases without US Food and Drug Administration-approved treatments. Non-EoE EGIDs are further subclassified by the area of the GI tract that is involved; they comprise eosinophilic gastritis, eosinophilic enteritis (including eosinophilic duodenitis), and eosinophilic colitis. As with other GI disorders, the disease presentations and mechanisms differ depending on the involved segment of the GI tract; however, the differences between EoE and non-EoE EGIDs extend beyond which GI tract segment is involved. The aim of this article is to summarize the commonalities and differences between the clinical presentations and disease mechanisms for EoE and non-EoE EGIDs., Competing Interests: Disclosure statement Supported by the National Institutes of Health (grant K99/R00 AI158660 [to T.S.] and grants R01 AI045898, R01 AI124355, and U19 AI070235 [to M.E.R.]); the Digestive Health Center (Pilot and Feasibility Program; grant P30 DK078392 [to T.S.]); Cincinnati Children's Trustee Award (to T.S.); the Campaign Urging Research for Eosinophilic Disease (CURED) (to M.E.R.); the Sunshine Charitable Foundation and its supporters Denise A. Bunning and David G. Bunning (to M.E.R.); and CEGIR (U54 AI117804 to M.E.R.), which is part of the Rare Diseases Clinical Research Network (RDCRN), an initiative of the Office of Rare Diseases Research (ORDR), NCATS, and is funded through collaboration between NIAID, NIDDK, NCATS. CEGIR is also supported by patient advocacy groups including the Campaign Urging Research for Eosinophilic Diseases (CURED), American Partnership for Eosinophilic Disorders (APFED), and Eosinophilic Family Coalition (EFC). As a member of the RDCRN, CEGIR is also supported by its Data Management and Coordinating Center (DMCC) (U2CTR002818). Funding support for the DMCC is provided by the National Center for Advancing Translational Sciences (NCATS) and the National Institute of Neurological Disorders and Stroke (NINDS). Disclosure of potential conflict of interest: M. E. Rothenberg is a consultant for Pulm One, Spoon Guru, ClostraBio, Serpin Pharm, Celldex, Uniquitybio, Santa Ana Bio, EnZen Therapeutics, Bristol Myers Squibb, AstraZeneca, Pfizer, GlaxoSmith Kline, Regeneron/Sanofi, and Guidepoint and has an equity interest in the first 8 listed plus Allakos and royalties from reslizumab (Teva Pharmaceuticals), PEESSv2 (Mapi Research Trust), and UpToDate. In addition, T. Shoda and M. E. Rothenberg are inventors of patents owned by Cincinnati Children’s Hospital. The rest of the authors declare that they have no relevant conflicts of interest., (Copyright © 2024 American Academy of Allergy, Asthma & Immunology. All rights reserved.)

Facioscapulohumeral muscular dystrophy (FSHD) is a progressive myopathy caused by the aberrant increased expression of the DUX4 retrogene in skeletal muscle cells. The DUX4 gene encodes a transcription factor that functions in zygotic genome activation and then is silenced in most adult somatic tissues. DUX4 expression in FSHD disrupts normal muscle cell function; however, the downstream pathogenic mechanisms are still unclear. Histologically, FSHD affected muscles show a characteristic dystrophic phenotype that is often accompanied by a pronounced immune cell infiltration, but the role of the immune system in FSHD is not understood. Previously, we used ACTA1;FLExDUX4 FSHD-like mouse models varying in severity as discovery tools to identify increased Interleukin 6 and microRNA-206 levels as serum biomarkers for FSHD disease severity. In this study, we use the ACTA1;FLExDUX4 chronic FSHD-like mouse model to provide insight into the immune response to DUX4 expression in skeletal muscles. We demonstrate that these FSHD-like muscles are enriched with the chemoattractant eotaxin and the cytotoxic eosinophil peroxidase, and exhibit muscle eosinophilia. We further identified muscle fibers with positive staining for eosinophil peroxidase in human FSHD muscle. Our data supports that skeletal muscle eosinophilia is a hallmark of FSHD pathology., (© The Author(s) 2024. Published by Oxford University Press.)

Purpose of Review: This review seeks to understand novel avenues for eosinophilic GI disease management. Biomarkers offer a unique and non-invasive approach to tracking EoE disease progression. While no biomarkers have definitively met the diagnostic criteria for eosinophilic GI diseases, some biomarkers have been shown to be associated with disease activity. Here, we examine the potential of recently studied biomarkers., Recent Findings: Current research shows advancements in blood, luminal fluid, and breath testing. Particular areas of interest include mRNA analyses, protein fingerprinting, amplicon sequence variants (ASVs), T cells and IgE receptors, eosinophilic cationic proteins, cytokines, and nitric oxide exhalation. Preliminary results showed that mucosal biomarkers, directly captured from the esophagus, may reflect the best representation of biopsy-based results, in contrast to biomarkers obtained from indirect or peripheral (blood, breath) methods. However, this is based on limited clinical studies without sufficient numbers to evaluate true diagnostic accuracy. Large-scale randomized trials are needed to fully ascertain both the optimal sampling technique and the specific biomarkers that reflect diagnostic status of the disease., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Rationale: Bronchiectasis is an airway inflammatory disease that is frequently associated with chronic rhinosinusitis (CRS). An eosinophilic endotype of bronchiectasis has recently been described, but detailed testing to differentiate eosinophilic bronchiectasis from asthma has not been performed. Objectives: This prospective observational study aimed to test the hypotheses that bronchiectasis with CRS is enriched for the eosinophilic phenotype in comparison with bronchiectasis alone and that the eosinophilic bronchiectasis phenotype exists as a separate entity from bronchiectasis associated with asthma. Methods: People with idiopathic or postinfectious bronchiectasis were assessed for concomitant CRS. We excluded people with asthma or primary ciliary dyskinesia and smokers. We assessed sputum and blood cell counts, nasal NO and fractional excreted NO, methacholine reactivity, skin allergy testing and total and specific immunoglobulin (Ig) E, cytokines in the sputum and serum, and the microbiome in the sputum and nasopharynx. Results: A total of 22 people with CRS (BE + CRS) and 17 without CRS (BE - CRS) were included. Sex, age, Reiff score, and bronchiectasis severity were similar. Median sputum eosinophil percentages were 0% (IQR, 0-1.5%) in BE - CRS and 3% (1-12%) in BE + CRS ( P  = 0.012). Blood eosinophil counts were predictive of sputum eosinophilia (counts ⩾3%; area under the receiver operating characteristic curve, 0.68; 95% confidence interval, 0.50-0.85). Inclusion of CRS improved the prediction of sputum eosinophilia by blood eosinophil counts (area under the receiver operating characteristic curve, 0.79; 95% confidence interval, 0.65-0.94). Methacholine tests were negative in 85.7% of patients in the BE - CRS group and 85.2% of patients in the BE + CRS group ( P  > 0.99). Specific IgE and skin testing were similar between the groups, but total IgE levels were increased in people with increased sputum eosinophils. Microbiome analysis demonstrated distinct microbiota in nasopharyngeal and airway samples in the BE + CRS and BE - CRS groups, without significant differences between groups. However, interactome analysis revealed altered interactomes in individuals with high sputum eosinophil counts and CRS. Conclusions: Bronchiectasis with CRS is associated with an eosinophilic airway inflammation that is distinct from asthma.

Objective: To characterize the eosinophilic granulomatosis with polyangiitis (EGPA) population from the POLVAS registry depending on ANCA status and diagnosis onset, including their comparison with the granulomatosis with polyangiitis (GPA) subset with elevated blood eosinophilia (min. 400/ μ l) (GPA HE) to develop a differentiating strategy., Methods: A retrospective analysis of the POLVAS registry., Results: The EGPA group comprised 111 patients. The ANCA-positive subset ( n  = 45 [40.54%]) did not differ from the ANCA-negative one in clinics. Nevertheless, cardiovascular manifestations were more common in ANCA-negative patients than in those with anti-myeloperoxidase (MPO) antibodies (46.97% vs. 26.92%, p  = 0.045). Patients diagnosed before 2012 ( n  = 70 [63.06%]) were younger (median 41 vs. 49 years, p   < 0.01), had higher blood eosinophilia at diagnosis (median 4,946 vs. 3,200/ μ l, p   < 0.01), and more often ear/nose/throat (ENT) and cardiovascular involvement. GPA HE comprised 42 (13.00%) out of 323 GPA cases with reported blood eosinophil count. Both GPA subsets had a lower prevalence of respiratory, cardiovascular, and neurologic manifestations but more often renal and ocular involvement than EGPA. EGPA also had cutaneous and gastrointestinal signs more often than GPA with normal blood eosinophilia (GPA NE) but not GPA HE. The model differentiating EGPA from GPA HE, using ANCA status and clinical manifestations, had an AUC of 0.92, sensitivity of 96%, and specificity of 95%., Conclusion: Cardiovascular symptoms were more prevalent in the ANCA-negative subset than in the MPO-ANCA-positive one. Since EGPA and GPE HE share similarities in clinics, diagnostic misleading may result in an inappropriate therapeutic approach. Further studies are needed to optimize their differentiation and tailored therapy, including biologics., Competing Interests: All authors have declared no conflicts of interest., (Copyright © 2024 Anna Drynda et al.)

The prevalence of diseases characterised by eosinophilia is on the rise, emphasising the importance of understanding the role of eosinophils in these conditions. Eosinophils are a subset of granulocytes that contribute to the body's defence against bacterial, viral, and parasitic infections, but they are also implicated in haemostatic processes, including immunoregulation and allergic reactions. They contain cytoplasmic granules which can be selectively mobilised and secrete specific proteins, including chemokines, cytokines, enzymes, extracellular matrix, and growth factors. There are multiple biological and emerging functions of these specialised immune cells, including cancer surveillance, tissue remodelling and development. Several oral diseases, including oral cancer, are associated with either tissue or blood eosinophilia; however, their exact mechanism of action in the pathogenesis of these diseases remains unclear. This review presents a comprehensive synopsis of the most recent literature for both clinicians and scientists in relation to eosinophils and oral diseases and reveals a significant knowledge gap in this area of research.

Introduction: Asthma encompasses a spectrum of phenotypes often categorized into two groups- type 2 high (T2 high) and type 2 low (T2 low). T2 high includes atopic and eosinophilic presentations whereas T2 low is non-atopic, non-eosinophilic, and oft associated with neutrophilic inflammation. Eosinophilic asthma is often driven by IgE, IL-4, IL-5, and IL-13 and TSLP. This can lead to eosinophilic inflammatory response in the airways which in turn can be used as target for treatment., Areas Covered: The article will focus on biologic therapy that is currently being used in eosinophilic asthma management in mainly the adult population including clinical trials and co-morbidities that can be treated using the same biologics. A review on asthma biologics for pediatric population has been reviewed elsewhere., Expert Opinion: Biological therapy for asthma targeting the IgE, IL-4, IL-5, IL-13, and TSLP pathways are shown to have benefit for the treatment of eosinophilic asthma, as exemplified in real-world studies. When choosing the right biological agent factors such as phenotype, comorbidities, and cost-effectiveness of the biologic agent must be taken into consideration.

Allergic airway disease (AAD) is an example of type 2 inflammation that leads to chronic airway eosinophilia controlled by CD4 Th2 cells. Inflammation is reinforced by mast cells and basophils armed with allergen-specific IgE made by allergen-specific B2 B cells of the adaptive immune system. Little is known about how AAD is affected by innate B1 cells, which produce natural antibodies (NAbs) that facilitate apoptotic cell clearance and detect damage- and pathogen-associated molecular patterns (DAMPS and PAMPS). We used transgenic mice lacking either B cells or NAbs in distinct mouse models of AAD that require either DAMPS or PAMPS as the initial trigger for type 2 immunity. In a DAMP-induced allergic model, driven by alum and uric acid, mouse strains lacking B cells (CD19DTA), NAbs (IgHEL MD4), or all secreted antibodies (sIgm-/-Aid-/-) displayed a significant reduction in both eosinophilia and Th2 priming compared with WT or Aid-/- mice lacking only germinal center-dependent high-affinity class-switched antibodies. Replenishing B cell-deficient mice with either unimmunized B1 B cells or NAbs during sensitization restored eosinophilia, suggesting that NAbs are required for licensing antigen-presenting cells to prime type 2 immunity. Conversely, PAMP-dependent type 2 priming to house dust mite or Aspergillus was not dependent on NAbs. This study reveals an underappreciated role of B1 B cell-generated NAbs in selectively driving DAMP-induced type 2 immunity.

Two recent articles by the same research group documented that patients with severe eosinophilic asthma exhibit an increased proportion of a subtype of eosinophils, namely CD62L low inflammatory eosinophils (iEos) and identified an intriguing correlation between such iEos and asthma control scores. Moreover, CD62L low iEos were reduced after treatment with the anti-IL-5 monoclonal antibody mepolizumab. In the future, we believe that eosinophil subtypes could represent a useful biomarker in severe eosinophilic asthma, helping clinicians characterize patient endotypes and monitoring the response to biological drugs.

Objective: Mechanisms that lead to Eosinophilic Chronic Rhinosinusitis (ECRS) are not fully established in the literature. It is desirable to assess ECRS in a model that embraces most of the related events. This article reviewed the murine models for ECRS and compared them regarding eosinophilic polypoid formation., Methods: The authors reviewed the articles that included the terms "chronic rhinosinusitis" OR "chronic sinusitis" AND "animal model". We analyzed articles in English that evaluated both the number of polyps and the number of eosinophils in the sinus mucosa of mouse models., Results: We identified a total of 15 articles describing different models of ECRS that used BALB/c or C57BL/6 mice, and different triggers/stimulants such as Staphylococcus aureus Enterotoxin B (SEB) + Ovalbumin (OVA); House Dust Mite (HDM) ± Ovalbumin (OVA); and Aspergillus oryzae Protease (AP) + Ovalbumin (OVA). OVA associated with SEB was the commonest protocol to induce ECRS in both BALB/c and C57BL/6 mice, and it produced a robust response of eosinophilic nasal polyps in both. AP + OVA protocol also led to a good ECRS response. The other models were not considered adequate to produce eosinophilic polyps in mice., Conclusion: In conclusion, OVA associated with SEB seems to produce the most robust eosinophilic sinonasal inflammation., (Copyright © 2023 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier España S.L.U. All rights reserved.)

We report a case of eosinophilic fasciitis triggered by strenuous physical activity, which did not relapse during the follow-up period. We ascertained that interleukin-33 (IL-33) was released from the vascular endothelial cells after intense exercise, inducing type 2 innate lymphocytes (ILC2) and causing fasciitis. A healthy woman experienced itching on both limbs a few hours after a game of drumming. Her hand, knee joints, and legs gradually swelled up with groove signs along the superficial veins. White blood cell and eosinophil counts were significantly elevated. Magnetic resonance imaging revealed a high signal at the fascia on both lower limbs. Histopathological findings of the left lower limb tissue specimen showed edematous fascia with eosinophils. No relapse of eosinophilic fasciitis was observed after finishing treatment with prednisolone. Immunological staining for IL-4, IL-5, IL-33, tumor necrosis factor-α, and interferon-γ was performed on the fascial tissue. Both IL-4 and IL-5 were stained on the lymphocytes at the muscle and fascia levels; however, CD3 and CD4 were unstained in these cells, suggesting that those cells were ILC2. Tumor necrosis factor-α and interferon-γ were unstained. Vascular endothelial cells in the fascia strongly expressed IL-33. Eosinophilic fasciitis may be associated with type 2 immunity triggered by IL-33 in the current case., (© 2022 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.)

This review highlights recent advances in the understanding of eosinophils and eosinophilic diseases, particularly eosinophilic gastrointestinal diseases during the last year. The increasing incidence of diseases marked by eosinophilia has been documented and highlighted the need to understand eosinophil biology and eosinophilic contributions to disease. Significant insight into the nature of eosinophilic diseases has been achieved using next-generation sequencing technologies, proteomic analysis, and machine learning to analyze tissue biopsies. These technologies have elucidated mechanistic underpinnings of eosinophilic inflammation, delineated patient endotypes, and identified patient responses to therapeutic intervention. Importantly, recent clinical studies using mAbs that interfere with type 2 cytokine signaling or deplete eosinophils point to multiple and complex roles of eosinophils in tissues. Several studies identified distinct activation features of eosinophils in different tissues and disease states. The confluence of these studies supports a new paradigm of tissue-resident eosinophils that have pro- and anti-inflammatory immunomodulatory roles in allergic disease. Improved understanding of unique eosinophil activation states is now poised to identify novel therapeutic targets for eosinophilic diseases., (Copyright © 2021 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Eosinophils are potent innate effector cells associated mainly with type 2 immune responses elicited by helminths and allergens. Their activity needs to be tightly controlled to prevent severe inflammation and tissue damage. Eosinophil degranulation and secretion of inflammatory effector molecules, including cytokines, chemokines, and lipid mediators, can be regulated by activating and inhibitory receptors on the cell surface. In this study, we investigated the modulation of proliferation, apoptosis, gene expression, and cytokine/chemokine secretion from IL-33-activated Mus musculus eosinophils on cross-linking of the transmembrane receptor Sialic acid-binding Ig-like lectin F (Siglec-F). Siglec-F contains an ITIM plus an ITIM-like motif in its intracellular tail and is mainly regarded as an inhibitory and apoptosis-inducing receptor. In vitro costimulation of bone marrow-derived eosinophils with anti-Siglec-F and IL-33 compared with treatment with either alone led to enhanced STAT6 phosphorylation, stronger induction of hypoxia/glycolysis-related proinflammatory genes, and elevated secretion of type 2 cytokines (IL-4, IL-13) and chemokines (CCL3, CCL4) with only minor effects on proliferation and apoptosis. Using a competitive mixed bone marrow chimera approach with wild-type and Siglec-F-deficient eosinophils, we observed no evidence for Siglec-F-regulated inhibition of Aspergillus fumigatus -elicited lung eosinophilia. Truncation of the Siglec-F cytoplasmic tail, but not mutation of the ITIM and ITIM-like motifs, ablated the effect of enhanced cytokine/chemokine secretion. This provides evidence for an ITIM phosphorylation-independent signaling pathway from the cytoplasmic tail of the Siglec-F receptor that enhances effector molecule release from activated eosinophils., (Copyright © 2022 by The American Association of Immunologists, Inc.)

This study aimed to investigate the effect of age in patients with chronic rhinosinusitis with nasal polyp (CRSwNP). 269 patients were divided into eosinophilic and non-eosinophilic groups based on tissue eosinophilia, defined by eosinophils accounting for more than 20% of the total inflammatory cells. Patients were then further divided into younger and older groups based on the age of 35 years. Clinical characteristics including blood eosinophil, Lund Mackay score, and modified Lund-Kennedy (mLK) scores were compared. Levels of 14 cytokines from nasal tissues of an additional 78 patients were analyzed. Tissue eosinophilia was significantly associated with age and the proportion of non-eosinophilic CRSwNP was significantly higher in younger patients as compared to older patients (79.2% vs 56.6%). There was no difference in clinical characteristics and cytokine levels between the younger and older patients with eosinophilic CRSwNP. In contrast, in patients with non-eosinophilic CRSwNP, younger patients had significantly lower preoperative blood eosinophils and higher mLK scores at three and six months, postoperatively, compared to older patients. Alpha-1 antitrypsin and IL-5 levels were significantly lower in younger patients than in older patients in non-eosinophilic CRSwNP. This study suggests a potential association between age, non-type 2 inflammation and treatment outcome in CRSwNP., (© 2022. The Author(s).)

Competing Interests: Declaration of interests We declare no competing interests.

Background: Reports indicate patients with feeding difficulties demonstrate signs of inflammation on biopsies, notably eosinophilia, but it is unknown whether mast cell density contributes to variety or volume limitation symptoms. The aim of our study was to evaluate eosinophil and mast cell density of EGD biopsies in pediatric patients with symptoms of decreased volume or variety of ingested foods., Methods: We conducted a single-center, retrospective chart review of EMRs for all new feeding clinic patients between 0 and 17 years of age. Patients were categorized by symptoms at the initial visit as well as eosinophil and mast cell densities in those with EGD biopsies. Ten patients were identified as controls., Results: We identified 30 patients each with volume and variety limitation. Antral mast cell density was increased in 32.1% of variety-limited patients, 37.5% of volume limited patients, and in no controls; Duodenal mast cell density was increased in 32.1% of variety-limited patients, 40.6% of volume-limited patients, and in no controls., Conclusions: In both variety- and volume-limited patients, antral and duodenal mast cell densities were increased. These associations warrant further investigation of the mechanism between mast cells and development of feeding difficulties, allowing more targeted pediatric therapies.