Journal of Allergy and Clinical Immunology

Eosinophilic esophagitis (EoE) is a chronic allergic disease driven by exposure to culprit antigens. Due to the local nature of the inflammation, diagnosis and assessment are limited to invasive procedures. Based on prior single-cell RNA sequencing (scRNA-seq) data linking peripheral GPR15+ pathogenic effector Th2 (peTh2) cells to esophageal tissue peTh2s, we hypothesized the direct involvement of GPR15+ peTh2 cells in EoE pathogenesis and aimed to further evaluate their association with EoE disease status. We subjected samples from subjects with or without EoE to flow cytometry (n = 74 peripheral blood, 17 biopsy) and scRNA-seq (n = 27 peripheral blood, 10 biopsy). Expression of GPR15 by peripheral peTh2 cells was increased in EoE, and these cells expressed increased CD38 in active EoE--findings recapitulated in esophageal biopsies. We also identified a peTh2-associated, CD38-containing gene expression program that peripheral GPR15+ peTh2 cells upregulated in active EoE. The level of upregulation was distinct from other circulating peTh2 cells and was more similar to that seen in esophageal peTh2 cells. An association between expression of GPR15 by peripheral peTh2 cells, the aryl hydrocarbon receptor was strongest in subjects with EoE, suggesting an environmental exposure or susceptibility. The magnitude of GPR15 expression by peripheral peTh2 cells could effectively in discriminate active EoE from no EoE in our study population (AUC 0.93). Our data suggest that EoE-related peTh2 cells are identifiable and accessible in the peripheral blood, and could be exploited in both clinical practice as a non-invasive biomarker and continued investigation into mechanisms driving EoE. One sentence summaryGPR15 marks a subset of peripheral blood pathogenic effector Th2 cells associated with eosinophilic esophagitis (EoE) that upregulate CD38 during active disease - an observation that has potential to be used for non-invasive diagnosis and monitoring of EoE and that has suggests new mechanisms driving this increasingly prevalent allergic disease.

BackgroundEosinophilic esophagitis (EoE) is a chronic T helper type 2 (Th2)-associated inflammatory disorder triggered by food allergens, resulting in esophageal dysfunction through edema, fibrosis, and tissue remodeling. The role of epithelial remodeling in EoE pathogenesis is critical but not fully understood. ObjectiveTo investigate the role of epithelial IKK{beta}/NF{kappa}B signaling in EoE pathogenesis using a mouse model with conditional Ikk{beta} knockout in esophageal epithelial cells (Ikk{beta}EEC-KO). MethodsEoE was induced in Ikk{beta}EEC-KOmice through skin sensitization with MC903/Ovalbumin (OVA) followed by intraesophageal OVA challenge. Histological and transcriptional analyses were performed to assess EoE features. Single-cell RNA sequencing (scRNA-seq) was used to profile esophageal mucosal cell populations and gene expression changes. ResultsIkk{beta}EEC-KO/EoE mice exhibited hallmark EoE features, including eosinophil infiltration, intraepithelial eosinophils, microabscesses, basal cell hyperplasia, and lamina propria remodeling. RNA-seq revealed significant alterations in IKK{beta}/NF{kappa}B signaling pathways, with decreased expression of RELA and increased expression of IKK{beta} negative regulators. scRNA- seq analyses identified disrupted epithelial differentiation and barrier integrity, alongside increased type 2 immune responses and peptidase activity. ConclusionOur study demonstrates that loss of epithelial IKK{beta} signaling exacerbates EoE pathogenesis, highlighting the critical role of this pathway in maintaining epithelial homeostasis and preventing allergic inflammation. The Ikk{beta}EEC-KO/EoE mouse model closely mirrors human EoE, providing a valuable tool for investigating disease mechanisms and therapeutic targets. This model can facilitate the development of strategies to prevent chronic inflammation and tissue remodeling in EoE. Key MessagesO_LICritical Role of Epithelial IKK{beta}/NF{kappa}B Signaling: Loss of this signaling exacerbates EoE, causing eosinophil infiltration, basal cell hyperplasia, and tissue remodeling, highlighting its importance in esophageal health. C_LIO_LIMolecular Insights and Therapeutic Targets: scRNA-seq identified disrupted epithelial differentiation, barrier integrity, and enhanced type 2 immune responses, suggesting potential therapeutic targets for EoE. C_LIO_LIRelevance of the Ikk{beta}EEC-KO/EoE Mouse Model: This model replicates human EoE features, making it a valuable tool for studying EoE mechanisms and testing treatments, which can drive the development of effective therapies. C_LI Capsule SummaryThis study reveals the crucial role of epithelial IKK{beta}/NF{kappa}B signaling in EoE, providing insights into disease mechanisms and potential therapeutic targets, highly relevant for advancing clinical management of EoE.

RationaleAsthma displays temporally variable symptoms which worsen overnight, corresponding with a nocturnal increase in airway eosinophils. The molecular clock within the club cell of the bronchial epithelium is a key driver of lung rhythmic processes, however, its role in chronic allergic airways disease (AAD) is not known. Elucidating the role of the club cell clock in regulating rhythmic inflammation in AAD could lead to new therapeutic advances. ObjectivesTo investigate the club cell molecular clock regulation of leukocyte trafficking in chronic AAD. Methodsccsp-bmal1 KO mice (which lack a functional clock in club cells) and littermate control mice underwent a 5-week chronic house dust mite (HDM) model of AAD, following which leukocyte populations and cytokines from blood, lung and airway compartments were quantified in a 24-hour time-course. Airway epithelial cells were cultured and transepithelial electrical resistance measured to explore circadian variability in barrier permeability and impact of pharmacological modulation of the clock. Main ResultsLeukocyte populations accumulate in the blood, lung and airways of HDM exposed mice in a time-of-day dependent manner, with time of peak accumulation dependent on cell type. This temporal gating of leukocyte accumulation is controlled and coordinated by the club cell circadian clock, which also regulates airway barrier integrity. Targeting REVERBa (a component of the molecular circadian clock), was effective at modifying airway barrier permeability achieving reduced transepithelial leukocyte migration. ConclusionsThe club cell clock gates leukocyte trafficking signals and airway barrier integrity by time of day in chronic allergic airway inflammation.

BackgroundEosinophilic esophagitis (EoE) is a chronic, type 2 inflammatory disease that is increasing in incidence and has substantial morbidity. Despite being clinically defined as a food allergy, the molecular details of food antigen presentation and recognition by the immune system are unknown. ObjectiveThe objective of this study was to identify and characterize the molecular basis of milk antigen presentation and T cell recognition in a patient with EoE milk allergy. MethodsMilk-expanded TCR clonotypes were identified using ex vivo stimulation followed by single cell RNA with linked, paired TRA and TRB sequencing. HLA restriction and antigen specificity of TCRs were identified using a combination of lentiviral expression, HLA sequencing, antibody blockade, and a peptide library screen. ResultsWe isolated a {beta}-casein specific TCR clonotype (eoeTCR-4) and determined its HLA restriction (HLA-DRB1*07:01) and cognate antigen ({beta}-casein AA 59-78). EoeTCR-4 was not detected among a larger group of subjects and is likely private to EoE Subject 1. ConclusionIn conjunction with the parent manuscript, this companion article provides the first molecular identity of food antigen presentation and immune recognition in EoE. SUMMARYThis manuscript is a companion to the parent manuscript "A molecular basis for milk allergen immune recognition in eosinophilic esophagitis". It provides additional data and detailed methods not provided in the parent manuscript. It is designed to supplement and support the findings and conclusions of the parent manuscript.

Atopic dermatitis (AD) commonly precedes food allergy and asthma in the atopic march. Epicutaneous (EC) sensitization in mice with ovalbumin (OVA) results in allergic skin inflammation that mimics AD and promotes food anaphylaxis or asthma following a gastric or intranasal challenge with OVA, respectively. Using our mouse model of EC sensitization with OVA we evaluate whether anti-IL-4R blocking antibody improve allergic skin inflammation and impact the atopic march. IL-4R blockade at the end of EC sensitization decreased allergic skin inflammation in OVA-sensitized mice, evidenced by significantly decreased eosinophil infiltration, decrease production of IL-4, IL-13 by OVA- restimulated splenocytes and reduced serum levels OVA-specific IgE. However, late IL- 4R blockade did not affect food anaphylaxis or airway inflammation in EC sensitized mice following an oral or intranasal challenge with OVA. IL-4R blockade at the beginning of EC sensitization not only impact allergic skin inflammation and systemic response to the antigen, but also decreased food anaphylaxis or airway inflammation following OVA challenge. These results suggest that the blockade of sensitization through the skin by IL-4R blockade could impact the atopic march.

BackgroundEosinophilic esophagitis (EoE) is a chronic allergic disease characterized by esophageal dysfunction, type-2 inflammation, and esophageal eosinophilic infiltrate. While proton pump inhibitor (PPI) therapy is commonly used for EoE management, the underlying mechanism of action remains unclear. MethodsAir-liquid interface culture of esophageal epithelial cells was employed to investigate the impact of the PPI omeprazole on barrier integrity in IL-13-treated cultures. Epithelial chemokine secretion was assessed following stimulation with IL-13 and omeprazole, and the migration of eosinophils from healthy human donors was evaluated using 3 {micro}m pore-sized transwells. A co-culture system of epithelial cells and eosinophils was employed to study chemokine secretion and eosinophil adhesion and activation markers. ResultsOmeprazole treatment in the IL-13-treated air-liquid interface (ALI) model resulted in 186 differentially expressed genes and restored barrier integrity compared to ALI treated with IL-13 alone. Omeprazole treatment reduced STAT6 phosphorylation, downregulated calpain 14, and upregulated desmoglein-1 in the IL-13-treated air-liquid interface samples. IL-13-induced upregulation of Eotaxin-3, CXCL10, and periostin, but this was downregulated by omeprazole. Further, the expression of CD11b, CD18, and CD69 was lower on eosinophils from omeprazole-treated epithelial-eosinophil co-cultures, which also had lower levels of eotaxin-3, CXCL10, CCL2, and CCL4. ConclusionOmeprazole reduced the effects of IL-13 in both the epithelial air-liquid interface model and eosinophil-epithelial co-cultures, reducing barrier dysfunction, chemokine expression, and upregulation of eosinophil adhesion markers.

Allergic asthma is a chronic inflammatory respiratory disease associated with eosinophilic infiltration, increased mucus production, airway hyperresponsiveness (AHR), and airway remodeling. Epidemiologic data has revealed that the prevalence of allergic sensitization and associated diseases has increased in the twentieth century. This has been hypothesized to be partly due to reduced contact with microbial organisms (the hygiene hypothesis) in industrialized society. Airway epithelial cells, once considered a static physical barrier between the body and the external world, are now widely recognized as immunologically active cells that can initiate, maintain, and restrain inflammatory responses, such as those that mediate allergic disease. Airway epithelial cells can sense allergens via myriad expression of Toll-like receptors (TLRs) and other pattern-recognition receptors (PRRs). We sought to determine whether the innate immune response stimulated by a combination of Pam2CSK4 ("Pam2", TLR2/6 ligand) and a class C oligodeoxynucleotide ODN362 ("ODN", TLR9 ligand) when delivered together by aerosol ("Pam2ODN"), can modulate the allergic immune response to allergens. Treatment with Pam2ODN 7 days before sensitization to House Dust Mite (HDM) extract resulted in a strong reduction in eosinophilic and lymphocytic inflammation. This Pam2ODN immunomodulatory effect was also seen using Ovalbumin (OVA) and A. oryzae (Ao) mouse models. The immunomodulatory effect was observed as much as 30 days before sensitization to HDM, but ineffective just 2 days after sensitization, suggesting that Pam2ODN immunomodulation lowers the allergic responsiveness of airway epithelial cells. Furthermore, Pam2 and ODN cooperated synergistically suggesting that this treatment is superior to any single agonist in the setting of allergen immunotherapy. One Sentence SummaryA synergistic combination of Toll-like Receptor agonists, delivered directly into the lung mucosa, can attenuate allergic responsiveness of airway epithelial cells and prevent host sensitization to aeroallergens. What is already knownO_LIAllergic sensitization has increased in the 20th century due to reduced contact with microbial organisms in industrialized society (ie. hygiene hypothesis) C_LIO_LIWe have previously identified a pharmacological means to stimulate innate immunity of lung epithelial cells. C_LI What this study addsO_LIActivation of innate immunity in lung epithelial cells attenuates the allergic responsiveness of mice. C_LIO_LISynergistic cooperation of pattern recognition receptors induces stronger immunomodulatory responses C_LI What is the clinical significanceO_LIAerosolized Toll-like Receptor agonists have been demonstrated as safe in human clinical trials C_LIO_LIThis study provides proof-of-principle that aerosolized toll-like receptor agonists could have clinical efficacy in the setting of the allergen immunotherapy C_LI

BackgroundThe immunometabolic mechanisms underlying variable responses to oral immunotherapy (OIT) in patients with IgE-mediated food allergy are unknown. ObjectiveTo identify novel pathways associated with tolerance in food allergy, we used metabolomic profiling to find pathways important for food allergy in multi-ethnic cohorts and responses to OIT. MethodsUntargeted plasma metabolomics data were generated from the VDAART healthy infant cohort (N=384), a Costa Rican cohort of children with asthma (N=1040), and a peanut OIT trial (N=20) evaluating sustained unresponsiveness (SU, protection that lasts after therapy) versus transient desensitization (TD, protection that ends immediately afterwards). Generalized linear regression modeling and pathway enrichment analysis identified metabolites associated with food allergy and OIT outcomes. ResultsCompared with unaffected children, those with food allergy were more likely to have metabolomic profiles with altered histidines and increased bile acids. Eicosanoids (e.g., arachidonic acid derivatives) (q=2.4x10-20) and linoleic acid derivatives (q=3.8x10-5) pathways decreased over time on OIT. Comparing SU versus TD revealed differing concentrations of bile acids (q=4.1x10-8), eicosanoids (q=7.9x10-7), and histidine pathways (q=0.015). In particular, the bile acid lithocholate (4.97[1.93,16.14], p=0.0027), the eicosanoid leukotriene B4 (3.21[1.38,8.38], p=0.01), and the histidine metabolite urocanic acid (22.13[3.98,194.67], p=0.0015) were higher in SU. ConclusionsWe observed distinct profiles of bile acids, histidines, and eicosanoids that vary among patients with food allergy, over time on OIT and between SU and TD. Participants with SU had higher levels of metabolites such as lithocholate and urocanic acid, which have immunomodulatory roles in key T-cell subsets, suggesting potential mechanisms of tolerance in immunotherapy. Key Messages- Compared with unaffected controls, children with food allergy demonstrated higher levels of bile acids and distinct histidine/urocanic acid profiles, suggesting a potential role of these metabolites in food allergy. - In participants receiving oral immunotherapy for food allergy, those who were able to maintain tolerance-even after stopping therapyhad lower overall levels of bile acid and histidine metabolites, with the exception of lithocholic acid and urocanic acid, two metabolites that have roles in T cell differentiation that may increase the likelihood of remission in immunotherapy. Capsule summaryThis is the first study of plasma metabolomic profiles of responses to OIT in individuals with IgE-mediated food allergy. Identification of immunomodulatory metabolites in allergic tolerance may help identify mechanisms of tolerance and guide future therapeutic development. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=125 SRC="FIGDIR/small/24308233v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1d199f3org.highwire.dtl.DTLVardef@1d24661org.highwire.dtl.DTLVardef@abb6corg.highwire.dtl.DTLVardef@96e3ca_HPS_FORMAT_FIGEXP M_FIG C_FIG

Defects of filaggrin (FLG) compromise epidermal barrier function and represent an important known genetic risk factor for atopic dermatitis (AD), but also for systemic atopy, including allergic sensitization and asthma. The flaky tail mouse model, widely used to address mechanisms of atopy induction by barrier-defective skin, harbors two mutations that affect the skin barrier, the mutation Flgft, resulting in near-complete loss of FLG expression, and the matted mutation inactivating transmembrane protein 79 (Tmem79). Upon separation of the two mutant loci, which are closely linked on chromosome 3, mice defective only for Tmem79 featured pronounced dermatitis and systemic atopy. Upon extensive backcross to BALB/c, also Flgft/ft mice (assumed to be wild type for Tmem79), developed AD-like dermatitis and reproduced the human atopic march, with high IgE levels and spontaneous asthma, suggesting a key role for functional Flg in protection from atopy also in mice. In contrast, BALB/c mice congenic for a targeted Flg knock out mutation did not develop skin inflammation or atopy. To resolve this discrepancy, we generated Flg-deficient mice on a pure BALB/c background by inactivating the Flg gene in BALB/c embryos. These animals feature an ichthyosis phenotype, but do not develop spontaneous dermatitis or systemic atopy. We sequenced the genome of the atopic Flgft BALB/c congenics and discovered that they were unexpectedly homozygous for the atopy-causing Tmem79matted mutation. In summary, we show that Flg-deficiency does not cause atopy in mice. This finding is in line with lack of atopic disease in a fraction of Ichthyosis vulgaris patients carrying two FLG null alleles. However, absence of FLG may promote and modulate dermatitis caused by other genetic barrier defects, as skin inflammation in Tmem79ma/maFlgft/ft BALB/c congenics is qualitatively different compared to Tmem79ma/ma mice.

Group 2 innate lymphoid cells (ILC2s) are critical players during type 2 inflammation present in most forms of asthma. ILC2s are tissue-resident cells that produce cytokines IL-5 and IL-13 critical to eosinophilic airway inflammation, mucus production, remodeling, and hyperresponsiveness. Though each ILC subset (ILC1s, ILC2s, ILC3s) is identified by specific transcription factors, cell surface receptors and cytokine profiles, functional plasticity between ILC subtypes occurs in various contexts. IL-18/IL-18R loci SNPs are linked to asthma in multiple genome-wide association studies and IL-18 has been shown to promote plasticity in ILC2s. Despite this, little is known about the in vivo role of IL-18/IL-18R on ILC2 responses in the lung. Within hours after mice were exposed to the fungal allergy Alternaria alternata, airway levels of IL-18 and IL-18 receptor expression increased on ST2+ ILCs. Single-cell RNA sequencing of lung cells from Alternaria-challenged mice showed that Il18 was largely expressed by alveolar macrophages, while IL-18R was highly expressed in IL-13+ILC2s. Utilizing IL-18 receptor knock-out mice (IL- 18R-/-), we observed increases in IL-17A production from both ST2+ and ST2-negative ILCs compared to control mice. We further observed an early increase in dual production of IL-5 and IL-17A in ST2+ ILCs followed by enhanced lung eosinophilia in the absence of IL-18R. Together, our findings suggest that IL-18 signaling prevents IL-17A production from ILC2s and subsequent eosinophilia in vivo. A further understanding of the regulation of ILC plasticity may lead to novel therapeutic targets in the treatment of ILC-driven asthma.

BackgroundIn modern societies, irregular and unhealthy eating behavior is increasingly prevalent, contributing to the development of both metabolic and inflammatory disorders. Limiting food access to a specific time window of the day, without caloric restriction, helps prevent and treat metabolic diseases. Given the close connection between metabolism and immune function, we investigated how meal timing influences the severity of contact hypersensitivity (CHS), a murine model of human allergic contact dermatitis which affects approximately 20% of the population. MethodsMice were fed with normal (NC) or high-fat (HF) chow under ad libitum (AL) or 10/14 time-restricted feeding (TRF). CHS severity was analyzed at macroscopic, tissue and cellular levels in both mild (acute) and severe (subacute) forms of the disease. To assess the mediator role of leptin, we used db/db mice, inhibited leptin signaling and analyzed human transcriptomic data. ResultsUnder conditions with ad libitum (AL) food access, HF diet resulted in impaired metabolic state and a more severe form of inflammation. Increased ear thickness, leukocyte infiltration, pustule formation, IL-1{beta}, CXCL2 levels and markedly delayed resolution of the inflammation were observed in HF-AL animals. Time-restricted feeding (TRF) reduced HF diet-induced weight gain and exacerbation of the inflammatory symptoms, even when started after disease onset. In HF-AL mice, serum leptin levels were elevated and displayed a phase-shifted diurnal pattern compared to the NC group, whereas TRF markedly attenuated these changes. NC-fed db/db mice that produced high levels of leptin exhibited worsened CHS. Blocking the leptin receptors alleviated the inflammatory symptoms in both db/db and HF-AL mice. Extending the analysis to patients transcriptomic data and histology suggests that leptin may contribute to pustule formation in non-infectious dermatitis in humans. ConclusionsOur data indicate that both TRF and local inhibition of leptin receptors can individually and in combination serve as effective new tools in managing allergic contact dermatitis.

Eosinophilic esophagitis is a chronic food antigen-driven allergic inflammatory disease associated with symptoms involving the nervous system such as refractory pain. Yet, the role of the nervous system in disease pathogenesis has not received much attention. Herein, we demonstrate that allergen exposure evokes pain-like behavior in association with increased nociceptor signaling and transcriptional responses in dorsal root ganglia. NaV1.8+ sensory nerves were found traveling along the length of the esophagus, organized in distinct bundles adjacent to the basal epithelium, with beta III-tubulin+ sensory nerves distributed more distal to the lumen. Targeted deletion of Il4ra in NaV1.8+ neurons impeded allergen-induced increases in nerve innervation density. Furthermore, Il4ra-/-NaV1.8 mice had diminished allergen-induced allergic inflammation in the esophagus including eosinophilia and transcription of pro-inflammatory genes. Translational studies revealed extensive myelinated nerve innervation in the human esophagus, which was increased in patients with eosinophilic esophagitis. Taken together, these data indicate that allergic inflammation is associated with an increase in non-evoked pain, esophageal nerve density, altered sensitivity of sensory neurons, and transcriptional changes in dorsal root ganglia. These finding identify a type 2 neuroimmune circuit that involves the interplay of allergen-induced IL-4 receptor-dependent DRG responses that modify esophageal end-organ inflammatory responses.

BackgroundMultiple regulatory mechanisms have been identified employing conventional hypothesis-driven approaches as contributing to allergen-specific immunotherapy outcomes, but understanding of how these integrate to maintain immunological homeostasis is incomplete. ObjectiveTo explore the potential for unbiased systems-level gene co-expression network analysis to advance understanding of immunotherapy mechanisms. MethodsWe profiled genome-wide allergen-specific Th-memory responses prospectively across 24mths of subcutaneous immunotherapy (SCIT) in 25 rhinitics, documenting changes in immunoinflammatory pathways and associated co-expression networks and their relationships to symptom scores to 36mths. ResultsPrior to immunotherapy, mite-specific Th-memory response networks involved multiple discrete co-expression modules including those related to Th2-, Type1-IFN-, Inflammation-, and FOXP3/IL2-associated signalling. A signature comprising 109 genes correlated with symptom scores, and these mapped to cytokine signalling/T-cell activation-associated pathways, with upstream drivers including hallmark Th1/Th2-and inflammation-associated genes. Reanalysis after 3.5mths SCIT updosing detected minimal changes to pathway/upstream regulator profiles despite 32.5% reduction in symptoms, however network analysis revealed underlying merging of FOXP3/IL2-with Inflammation-and Th2-associated modules. By 12mths on SCIT, symptoms had reduced by 41% without further significant changes to pathway/upstream regulator or network profiles. Continuing SCIT to 24mths stabilised symptoms at 47% of baseline, accompanied by upregulation of the Type1-IFN-associated network module and its merging into the Th2/FOXP3/IL2/Inflammation module. ConclusionsSCIT stimulates progressive integration of Th-memory-associated Th2-,FOXP3/IL2-, Inflammation-, and Type1-IFN-signalling subnetworks, forming a single highly integrated co-expression network module, maximising potential for stable homeostatic control of allergen-specific Th2 responses via cross-regulation. Th2-anatogonistic Type1-IFN signalling may play a key role in stabilising clinical effects of SCIT. Clinical ImplicationStabilisation of the clinical effectiveness of SCIT involves recruitment of Th2-antagonistic Type 1 IFN-dependent signalling into the overall gene co-expression network underlying the allergen-specific Th-memory response, and this does not occur until the 2nd year of treatment. Capsule summarySCIT-induced rewiring of the gene network governing allergen-specific Th2-memory, as opposed to selective upregulation of genes associated with regulatory functions, underlies the clinical effectiveness of immunotherapy.

TGF-{beta}1 is known to have a pro-inflammatory impact by inducing Th9 cells, while it also induces anti-inflammatory Treg cells (Tregs). In the context of allergic airway inflammation (AAI) its dual role can be of critical importance in influencing the outcome of the disease. Here we demonstrate that TGF-{beta} acts in AAI by driving effector T cells into Th9 cells, while Tregs differentiate independently. Induction of experimental AAI and airway hyperreactivity in a mouse model with inducible genetic ablation of the TGF{beta}-receptor 2 (TGFBR2) on CD4+T cells significantly reduced the disease phenotype. Further, it blocked the induction of Th9 cell frequencies, but increased Treg cells. To translate these findings into a human clinically relevant context, Th9 and Treg cells were quantified both locally in induced sputum and systemically in blood of allergic rhinitis and asthma patients with or without allergen-specific immunotherapy (AIT). Natural allergen exposure induced local and systemic Th2, Th9 cell and reduced Tregs, while therapeutic allergen exposure by AIT suppressed Th2 and Th9 cell frequencies along with TGF-{beta} and IL-9 secretion. Altogether, these findings support that neutralization of TGF-{beta} represents a viable therapeutic option in allergy and asthma, not posing the risk of immune dysregulation by impacting Tregs.

BackgroundThe incidence of lung allergies is reduced in countries with higher prevalence of infection and environmental exposure to microbes. However, enteric bacterial infections do not always correlate with lower incidence of allergic disorders and how lung immunity to allergens can be regulated by gut exposure to pathogens and their toxins is not fully understood. ObjectiveWe used mouse models of enterotoxigenic Escherichia coli (ETEC) infection and lung allergy to examine how gut exposure to bacteria, or their related toxins, affects allergic lung inflammation. MethodsNaive C57BL/6 mice were infected with enterotoxigenic Escherichia coli (ETEC) or orally treated with the ETEC LT toxin, to mimic enteric bacterial infections. After two weeks, these mice were treated intranasally with Ovalbumin (OVA) and Papain or IL-33, followed by challenge with OVA, to induce allergic lung inflammation that was assessed using multiple readouts. ResultsGut exposure to ETEC significantly inhibited allergic lung inflammation in a LT-dependent manner, as demonstrated by reduced tissue inflammation, less accumulation of type 2 cytokines, and reduced lung numbers of type 2 immune cells such as type 2 innate lymphoid cells (ILC2) and eosinophils. The anti-allergic capacity of LT was associated with reduced ability of lung ILC2s to recognize IL-33. Counterintuitively, deletion of either IL-33 or ILC2s significantly reverted the LT protective effect, suggesting the LT-mediated protection may occur through gut release and local sensing of IL-33. ConclusionsExposure to ETEC protects hosts against allergic lung inflammation through a negative feedback loop regulated by gut IL-33 release and sensing, suggesting a possible new immunological mechanism for reduced lung allergy incidence observed in areas with enteric bacterial infections. Key Messages- Enteric exposure to enterotoxigenic E. coli (ETEC) bacteria or its toxin LT significantly protects hosts against lung type 2 allergic inflammation. - ETEC and LT downregulate the capacity of lung ILC2s to respond to allergen-induced IL-33. - Deletion of IL-33 or ILC2s significantly impairs the protective effect of ETEC and LT, suggesting the presence of a negative feedback loop driven by toxin-induced gut IL-33 release.

Biologic monoclonal antibody therapies for severe asthma target the Type 2 endotype through blockade of the IgE, IL-5/eosinophil, or IL-4/13 pathways, which represents at least two-thirds of patients, and have led to significant clinical benefits in severe asthma management. However, studies show that 10-20% of patients may be non-responders and require a change in therapy. There is also the emerging concept that a significant percentage of patients may enter clinical remission, with a very high level of disease control and virtually symptom-free. These clinical scenarios and heterogeneity increase the need to develop blood-based biomarkers that can predict outcome. Identifying markers of clinical remission may also have potential for expanding access to other severe asthma patients not currently identified through serum IgE, blood eosinophils, or FeNO. In this study, blood was taken prior to therapy from severe asthma patients (n=31) with a Type 2 endotype, high serum IgE, atopy, and blood eosinophilia who qualified for both Omalizumab (anti-IgE) and Mepolizumab (anti-IL-5) and were randomised to receive either treatment. White blood cells underwent single cell RNA-sequencing and patients were assessed for clinical outcomes over a 6-month period. Non-response to either Omalizumab or Mepolizumab was predicted by a gene signature expressed in antiviral plasmacytoid dendritic cells. Clinical remission was predicted by a common gene signature in rarer CD34+ blood progenitors and circulating MAIT cells with a ROC Curve AUC of 0.91 and 0.88, respectively. This discovery study identifies novel blood biomarkers that predict clinical outcome to multiple biologic therapies in severe asthma.

Asthma is a complex airway inflammatory disease characterized by immune dysregulation, with diverse cellular contributors to inflammation that result in airway hyperresponsiveness (AHR) and excessive immune responses. The role of the inflammasome in asthma is conflicted. AIM2 is an innate immune receptor that activates the inflammasome through DNA binding. The clinical relevance of AIM2 in asthma is supported by analysis of blood or endobronchial biopsies from patients with severe asthma, showing increased AIM2 but not NLRP3 expression. We investigated the role of AIM2 in allergic asthma using ovalbumin (OVA)-LPS and house dust mite (HDM)- induced models. AIM2 expression was elevated in lung homogenates and bronchoalveolar lavage fluid (BALF) cells from allergen-induced groups compared to controls. In the OVA-LPS model, deletion of Aim2 led to reduced airway smooth muscle actin expression and DNA damage, contributing to decreased AHR and lung inflammation in whole body Aim2-/- mice. Surprisingly, cell-specific deletion in CD4+ T cells but not regulatory T cells or myeloid cells significantly affected AHR, indicating AIM2 in CD4+ T cells is a main driver of pathogenesis. Additionally, in HDM-induced asthma, Aim2-/- mice also exhibited reduced AHR. Cell-specific deletion reveals that AIM2 in CD4+ T cells promotes AHR and cytokine production, while AIM2 in myeloid cells modulates IgG1 levels and IL-13-producing CD4+ T cells, and the percentage of alveolar macrophages in BALF. These findings reveal that AIM2 differentially regulates HDM-induced allergic asthma through distinct exacerbating roles in T cells and myeloid cells, highlighting its potential as a therapeutic target. SignificanceAllergic asthma is a complex, heterogeneous disease characterized by airway inflammation and hyper-responsiveness. AIM2, an inflammasome activated by DNA, has emerged as a critical regulator of inflammatory diseases. In humans, AIM2 expression is elevated in severe asthma. In vivo studies highlight AIM2 as a key modulator of allergic asthma in both OVA-LPS and HDM- induced models. Surprisingly, its functional relevance in both models is mediated by its intrinsic role in T cells, while a modest role in myeloid cells is restricted to the HDM model. AIM2 promotes airway hyper-responsiveness and lung inflammation through enhancing type II cytokines, immune subpopulations and DNA damage response. These findings suggest AIM2 as a biomarker and therapeutic target for managing asthma, particularly in severe asthma subtypes.

Dendritic cells (DC) play a crucial role in regulating allergic asthma. We have demonstrated that the absence of semaphorin3E (Sema3E) exacerbates asthma features in acute and chronic asthma models. However, the role of plexinD1 in these events, especially in DC is unknown. Therefore, we investigated the role of plexinD1 in CD11c+ DC in the HDM model of asthma. CD11c+ DC-specific plexinD1 knockout mice and wild-type mice were subjected to HDM acute allergen protocol. Airway hyperresponsiveness (AHR) parameters were measured using the FlexiVent ventilator. Lung tissue and bronchoalveolar lavage fluid (BALF) were processed by flow cytometry. Cytokines and antibodies were measured using mesoscale and ELISA. Collagen deposition and mucus production were visualized by histological staining, and associated genes were investigated using Real-time PCR. We showed that DC-specific plexinD1 knockout mice exhibited exacerbated airway hyperresponsiveness, including increased airway resistance and tissue elastance. These mice displayed enhanced levels of mucus production and collagen gene expression compared to wild-type mice. These events were accompanied by enhanced recruitment of conventional DCs, specifically CD11b+ cDC2, into the lungs and higher levels of total and HDM-specific serum IgE in CD11cPLXND1 KO compared to wild-type counterparts. Mechanistically, a significantly higher level of IgE in the co-culture of B-DCs isolated from CD11cPLXND1 KO mice compared to DCs isolated from wild-type mice. Overall, our data reveals that the Sema3E-plexinD1 signalling pathway in CD11c+ DC is critical in modulating asthma features. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/557276v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@170c121org.highwire.dtl.DTLVardef@1979dddorg.highwire.dtl.DTLVardef@fd547borg.highwire.dtl.DTLVardef@1b5726a_HPS_FORMAT_FIGEXP M_FIG C_FIG

BackgroundIL4, IL5, IL13, and IL17-producing CD4 T helper 2 (Th2)-cells and IL17-producing CD4 T helper 17 (Th17)-cells contribute to chronic eosinophilic and neutrophilic airway inflammation in asthma and allergic airway inflammation. Chemokines and their receptors are upregulated in Th2/Th17-mediated inflammation. However, the ability of CXCR1 and CXCR2 modulate Th2 and Th17-cell-mediated allergic lung inflammation has not been reported. MethodsMice sensitized and challenged with cat dander extract (CDE) mount a vigorous Th2-Th17-mediated allergic lung inflammation. Allosteric inhibitor of CXCR1 and CXCR2, ladarixin was orally administered in this model. The ability of ladarixin to modulate allergen-challenge induced recruitment of CXCR1 and CXCR2-expressing Th2 and Th17-cells and allergic lung inflammation were examined. ResultsAllergen challenge in sensitized mice increased mRNA expression levels of Il4, Il5, Il13, Il6, Il1{beta}, Tgf{beta}1, Il17, Il23, Gata3, and Rorc, and induced allergic lung inflammation characterized by recruitment of CXCR1- and CXCR2-expressing Th2-cells, Th17-cells, neutrophils, and eosinophils. Allosteric inhibition of CXCR1 and CXCR2 vigorously blocked each of these pro-inflammatory effects of allergen challenge. CXCL chemokines induced a CXCR1 and CXCR2-dependent proliferation of IL4, IL5, IL13, and IL17 expressing T-cells. ConclusionAllosteric inhibition of CXCR1 and CXCR2 abrogates blocks recruitment of CXCR1- and CXCR2-expressing Th2-cells, Th17-cells, neutrophils, and eosinophils in this mouse model of allergic lung inflammation. We suggest that the ability of allosteric inhibition of CXCR1 and CXCR2 to abrogate Th2 and Th17-mediated allergic inflammation should be investigated in humans.

To the editorO_ST_ABSBackgroundC_ST_ABSAnaphylaxis is an acute and potentially life-threatening hypersensitivity reaction often involving the cardiovascular system. Circulating microRNAs (miRNAs/miR), including those carried by extracellular vesicles (EVs), are emerging biomarkers that display regulatory functions in allergy. This study aims to investigate the role of miR-29a in anaphylaxis. MethodsMiR-29a (3p and 5p) levels were assessed by qPCR from acute and baseline samples of serum and EVs from 70 patients with food- and drug-mediated anaphylaxis. EVs purification was confirmed by Western blot, electron microscopy, and NanoSight. MiR-29a-3p target genes were studied in silico using systems biology analysis (SBA). Moreover, miR-29a levels were evaluated in vitro in endothelial cells (ECs) exposed to anaphylactic mediators. Additionally, a panel of endothelial glycocalyx (eGCX)-associated mRNA was analyzed after transfection with a miR-29a-3p inhibitor. ResultsPatients with food-induced anaphylaxis exhibited reduced miR-29a-3p levels in both serum and EVs during the acute reaction. In contrast, miR-29a-5p levels were decreased in serum but not in EVs. No significant modulation of either miRNA was observed in drug-induced anaphylaxis. SBA of miR-29a-3p identified molecular pathways, biological processes and functional networks associated with eGCX remodelling. Intracellular levels of miR-29a-3p were modulated in vitro in ECs following exposure to anaphylactic mediators. Inhibition of miR-29a-3p significantly reduced ESM1 expression. ConclusionsThe miR-29a-3p levels are decreased in serum and EVs from patients with acute food-induced anaphylaxis, suggesting its potential as a promising biomarker. Moreover, a role for miR-29a-3p in eGCX integrity under anaphylactic conditions was demonstrated, potentially regulating ESM1. Key MessageMiR-29a-3p is selectively reduced in serum and extracellular vesicles during acute food-induced anaphylaxis and may regulate endothelial glycocalyx-related pathways, which supports its potential as a novel biomarker and molecular mediator of vascular involvement in anaphylactic reactions.