Type 2 innate lymphoid cells: at the cross-roads in allergic asthma

Type 2 innate immunity promotes the development of pulmonary fibrosis in Hermansky-Pudlak syndrome

Hermansky-Pudlak syndrome (HPS), particularly types 1 and 4, is characterized by progressive pulmonary fibrosis, a major cause of morbidity and mortality. However, the precise mechanisms driving pulmonary fibrosis in HPS are not fully elucidated. Our previous studies suggested that CHI3L1-driven fibroproliferation may be a notable factor in HPS-associated fibrosis. This study aimed to explore the role of CHI3L1-CRTH2 interaction on type 2 innate lymphoid cells (ILC2s) and explored the potential contribution of ILC2-fibroblast crosstalk in the development of pulmonary fibrosis in HPS. We identified ILC2s in lung tissues from patients with idiopathic pulmonary fibrosis and HPS. Using bleomycin-challenged WT and Hps1-/- mice, we observed that ILC2s were recruited and appeared to contribute to fibrosis development in the Hps1-/- mice, with CRTH2 playing a notable role in ILC2 accumulation. We sorted ILC2s, profiled fibrosis-related genes and mediators, and conducted coculture experiments with primary lung ILC2s and fibroblasts. Our findings suggest that ILC2s may directly stimulate the proliferation and differentiation of primary lung fibroblasts partially through amphiregulin-EGFR-dependent mechanisms. Additionally, specific overexpression of CHI3L1 in the ILC2 population using the IL-7Rcre driver, which was associated with increased fibroproliferation, indicates that ILC2-mediated, CRTH2-dependent mechanisms might contribute to optimal CHI3L1-induced fibroproliferative repair in HPS-associated pulmonary fibrosis.

Tissue microenvironment induces tissue specificity of ILC2

Type 2 innate lymphoid cells were found to be members of the innate immune cell family, which is involved in innate and adaptive immunity to resist the invasion of foreign antigens and induce allergic reactions caused by allergens. The advancement of ILC2 research has pointed out that ILC2s have a high degree of diversity, challenging the notion of their homogeneity as a cellular population. An increasing number of studies indicate that ILC2 is a cell population with tissue specificity which can be induced by the tissue microenvironment. In addition, crosstalk between tissues can change ILC2 functions of migration and activation. Here, we emphasize that ILC2 undergoes adaptive changes under the regulation of the tissue microenvironment and distant tissues, thereby coordinating the organization's operation. In addition, ILC2 alterations induced by the tissue microenvironment are not limited to the ILC2 cell population, and ILC2 can also transdifferentiate into another class of ILC cell population (ILC1 or ILC3). In this review, we summarized the tissue-specific effects of ILC2 by tissue microenvironment and focused on the function of ILC2 in inter-tissue crosstalk. Lastly, we discussed the transdifferentiations of ILC2 caused by the abnormal change in tissue environment.

LINC00998 Modulating M2 Macrophage Activation in Allergic Rhinitis by Stabilizing BOB.1 mRNA

Background

Allergic rhinitis (AR) is globally recognized as a considerable threat to human health with a rising prevalence and a substantial medical and socioeconomic burden. Numerous studies have emphasized the significance of long noncoding RNAs (lncRNAs) in allergic responses. Hence, this research dealt with exploring the involvement of the lncRNA LINC00998 in the mechanism of AR.

Methods

LINC00998 expression was assessed by qRT-PCR in peripheral blood mononuclear cells acquired from individuals with AR. Additionally, the potential relationship between LINC00998 and macrophage polarization was observed in vitro. Then we constructed AR mice model and macrophage polarization models using THP-1 cells as well as primary human macrophages to verify the M2 shift in AR and the low expression level of LINC00998 in M2 macrophages. We used gain- and loss-of-function experiments to explore the modification of LINC00998 in macrophage polarization. Furthermore, we explored the underlying mechanism of LINC00998 mediates through qRT-PCR, flow cytometry, and Western blot.

Results

The analysis revealed a significant decrease in LINC00998 expression in the samples obtained from patients with AR. LINC00998 is markedly increased in M1 macrophages whereas decreased in M2 macrophages in vitro. Furthermore, suppression of LINC00998 caused a remarkable enhancement in M2 polarization, whereas its overexpression led to its attenuation. Knockdown of LINC00998 led to a remarkable downregulation of BOB.1 mRNA and protein, while overexpression of LINC00998 upregulated their expression. Moreover, it was found that BOB.1 modulated macrophage polarization through the PU.1/IL-1β axis. Meanwhile, the modulation of LINC00098 overexpression on macrophage polarization and PU.1/ IL-1β can be reversed by BOB.1 siRNA.

Conclusion

This research revealed the lncRNA LINC00998 altered M2 macrophage polarization by regulating the BOB.1/PU.1/IL-1β axis, which open up new avenues for studying the pathogenesis of AR.

Dermis resident macrophages orchestrate localized ILC2 eosinophil circuitries to promote non-healing cutaneous leishmaniasis

Tissue-resident macrophages are critical for tissue homeostasis and repair. We previously showed that dermis-resident macrophages produce CCL24 which mediates their interaction with IL-4+ eosinophils, required to maintain their M2-like properties in the TH1 environment of the Leishmania major infected skin. Here, we show that thymic stromal lymphopoietin (TSLP) and IL-5+ type 2 innate lymphoid cells are also required to maintain dermis-resident macrophages and promote infection. Single cell RNA sequencing reveals the dermis-resident macrophages as the sole source of TSLP and CCL24. Generation of Ccl24-cre mice permits specific labeling of dermis-resident macrophages and interstitial macrophages from other organs. Selective ablation of TSLP in dermis-resident macrophages reduces the numbers of IL-5+ type 2 innate lymphoid cells, eosinophils and dermis-resident macrophages, and ameliorates infection. Our findings demonstrate that dermis-resident macrophages are self-maintained as a replicative niche for L. major by orchestrating localized type 2 circuitries with type 2 innate lymphoid cells and eosinophils.

House dust mite allergy: The importance of house dust mite allergens for diagnosis and immunotherapy

House dust mite (HDM) allergy belongs to the most important allergies and affects approximately 65-130 million people worldwide. Additionally, untreated HDM allergy may lead to the development of severe disease manifestations such as atopic dermatitis or asthma. Diagnosis and immunotherapy of HDM allergic patients are well established but are often hampered by the use of mite extracts that are of bad quality and lack important allergens. The use of individual allergens seems to be a promising alternative to natural allergen extracts, since they represent well-defined components that can easily be produced and quantified. However, a thorough characterization of the individual allergens is required to determine their clinical relevance and to identify those allergens that are required for correct diagnosis of HDM allergy and for successful immunotherapy. This review gives an update on the individual HDM allergens and their benefits for diagnosis and immunotherapy of HDM allergic patients.

Dermis resident macrophages orchestrate localized ILC2-eosinophil circuitries to maintain their M2-like properties and promote non-healing cutaneous leishmaniasis

Tissue-resident macrophages (TRMs) are critical for tissue homeostasis/repair. We previously showed that dermal TRMs produce CCL24 (eotaxin2) which mediates their interaction with IL-4 producing eosinophils, required to maintain their number and M2-like properties in the TH1 environment of the Leishmania major infected skin. Here, we unveil another layer of TRM self-maintenance involving their production of TSLP, an alarmin typically characterized as epithelial cell-derived. Both TSLP signaling and IL-5+ innate lymphoid cell 2 (ILC2s) were shown to maintain the number of dermal TRMs and promote infection. Single cell RNA sequencing identified the dermal TRMs as the sole source of TSLP and CCL24. Development of Ccl24-cre mice permitted specific labeling of dermal TRMs, as well as interstitial TRMs from other organs. Genetic ablation of TSLP from dermal TRMs reduced the number of dermal TRMs, and disease was ameliorated. Thus, by orchestrating localized type 2 circuitries with ILC2s and eosinophils, dermal TRMs are self-maintained as a replicative niche for L. major.

Therapeutic Effect of Renifolin F on Airway Allergy in an Ovalbumin-Induced Asthma Mouse Model In Vivo

Renifolin F is a prenylated chalcone isolated from Shuteria involucrata, a traditional minority ethnic medicine used to treat the respiratory diseases and asthma. Based on the effects of the original medicine plant, we established an in vivo mouse model of allergic asthma using ovalbumin (OVA) as an inducer to evaluate the therapeutic effects of Renifolin F. In the research, mice were sensitized and challenged with OVA to establish an allergic asthma model to evaluate the effects of Renifolin F on allergic asthma. The airway hyper-reactivity (AHR) to methacholine, cytokine levels, ILC2s quantity and mircoRNA-155 expression were assessed. We discovered that Renifolin F attenuated AHR and airway inflammation in the OVA-induced asthmatic mouse model by inhibiting the regulation of ILC2s in the lung, thereby, reducing the upstream inflammatory cytokines IL-25, IL-33 and TSLP; the downstream inflammatory cytokines IL-4, IL-5, IL-9 and IL-13 of ILC2s; and the co-stimulatory factors IL-2 and IL-7; as well as the expression of microRNA-155 in the lung. The findings suggest a therapeutic potential of Renifolin F on OVA-induced airway inflammation.

Novel potential treatable traits in asthma: Where is the research taking us?

Asthma is a complex, heterogeneous disease in which the underlying mechanisms are not fully understood. Patients are often grouped into phenotypes (based on clinical, biologic, and physiologic characteristics) and endotypes (based on distinct genetic or molecular mechanisms). Recently, patients with asthma have been broadly split into 2 phenotypes based on their levels of type 2 inflammation: type 2 and non-type 2 asthma. However, this approach is likely oversimplified, and our understanding of the non-type 2 mechanisms in asthma remains extremely limited. A better understanding of asthma phenotypes and endotypes may assist in development of drugs for new therapeutic targets in asthma. One approach is to identify "treatable traits," which are specific patient characteristics related to phenotypes and endotypes that can be targeted by therapies. This review will focus on emerging treatable traits in asthma and aim to describe novel patient subgroups and endotypes that may represent the next step in the search for new therapeutic approaches.

Tissue-Dependent Adaptations and Functions of Innate Lymphoid Cells

Tissue-resident immune cells reside in distinct niches across organs, where they contribute to tissue homeostasis and rapidly respond to perturbations in the local microenvironment. Innate lymphoid cells (ILCs) are a family of innate immune cells that regulate immune and tissue homeostasis. Across anatomical locations throughout the body, ILCs adopt tissue-specific fates, differing from circulating ILC populations. Adaptations of ILCs to microenvironmental changes have been documented in several inflammatory contexts, including obesity, asthma, and inflammatory bowel disease. While our understanding of ILC functions within tissues have predominantly been based on mouse studies, development of advanced single cell platforms to study tissue-resident ILCs in humans and emerging patient-based data is providing new insights into this lymphocyte family. Within this review, we discuss current concepts of ILC fate and function, exploring tissue-specific functions of ILCs and their contribution to health and disease across organ systems.

Acupoint Catgut-Embedding Therapy Inhibits NF-κB/COX-2 Pathway in an Ovalbumin-Induced Mouse Model of Allergic Asthma

Allergic asthma is associated with T helper (Th) 2 cell-biased immune responses and characterized by the airway hyperresponsiveness (AHR). Studies have shown that the acupoint catgut-embedding therapy (ACE) has a therapeutic effect on allergic asthma. However, the relevant mechanism is poorly understood. In present study, female BALB/c mice were sensitized and challenged with ovalbumin (OVA) to establish a model of allergic asthma. AHR was evaluated by using airway resistance ( $R_L$ ) and lung dynamic compliance (Cdyn). Airway inflammation and mucus hypersecretion were observed by HE and PAS staining. Inflammatory cells were counted, and related cytokines in bronchoalveolar lavage fluid (BALF) were detected by enzyme-linked immunosorbent assay (ELISA). Pulmonary group 2 innate lymphoid cell (ILC2s) proportions were analyzed by flow cytometry. The expression of nuclear factor κB (NF-κB) and cyclooxygenase-2 (COX-2) was detected by immunostaining. Our results showed that OVA induction resulted in a significant increase in $R_L$ , accompanied by a significant decrease in Cdyn. The levels of interleukin- (IL-) 4, IL-13, OVA-specific IgE in BALF, and the percentage of ILC2 in the lungs were markedly increased accompanied by a significant decreased in interferon-γ (IFN-γ). Furthermore, the expressions of p-NF-κB p65 and COX-2 in airways were significantly upregulated. After ACE treatment, the indicators above were significantly reversed. In conclusion, ACE treatment inhibited the secretion of Th2 cytokines and the proliferation of ILC2s in the lungs, thereby dampening the inflammatory activity in allergic asthma. The underlying mechanism might be related to the inhibition of NF-κB/COX-2 pathway.

2021 Brazilian Thoracic Association recommendations for the management of severe asthma

Advances in the understanding that severe asthma is a complex and heterogeneous disease and in the knowledge of the pathophysiology of asthma, with the identification of different phenotypes and endotypes, have allowed new approaches for the diagnosis and characterization of the disease and have resulted in relevant changes in pharmacological management. In this context, the definition of severe asthma has been established, being differentiated from difficult-to-control asthma. These recommendations address this topic and review advances in phenotyping, use of biomarkers, and new treatments for severe asthma. Emphasis is given to topics regarding personalized management of the patient and selection of biologicals, as well as the importance of evaluating the response to treatment. These recommendations apply to adults and children with severe asthma and are targeted at physicians involved in asthma treatment. A panel of 17 Brazilian pulmonologists was invited to review recent evidence on the diagnosis and management of severe asthma, adapting it to the Brazilian reality. Each of the experts was responsible for reviewing a topic or question relevant to the topic. In a second phase, four experts discussed and structured the texts produced, and, in the last phase, all experts reviewed and approved the present manuscript and its recommendations.

IL13 May Play an Important Role in Developing Eosinophilic Chronic Rhinosinusitis and Eosinophilic Otitis Media with Severe Asthma

A woman in her 50s was a super responder to benralizumab administered for the treatment of severe bronchial asthma (BA) with eosinophilic chronic rhinosinusitis with nasal polyp (ECRS) and eosinophilic otitis media (EOM). She exhibited the gradual exacerbation of ECRS/EOM despite good control of BA approximately 1 year after benralizumab initiation. Therefore, the treatment was switched to dupilumab, and the condition of the paranasal sinuses and middle ear greatly improved with the best control of her asthma. The patient reported that her physical condition was the best of her life. However, she developed a pulmonary opacity on chest computed tomography after 6 months. Histological examination of the lung parenchyma and cell differentiation of the bronchoalveolar lavage fluid indicated atypical chronic eosinophilic pneumonia, and treatment was switched to mepolizumab. Similarly to the period of benralizumab treatment, exacerbation of ECRS/EOM reduced her quality of life approximately 10 months after the administration of mepolizumab. Dupilumab was again introduced as a replacement for mepolizumab. The clinical course and consideration of the interaction between inflammatory cells led us to speculate that interleukin-13 could play a key role in the development of ECRS/EOM with severe BA.

The protective effect of solidagenone from Solidago chilensis Meyen in a mouse model of airway inflammation

Solidagenone is the main active constituent present in Solidago chilensis Meyen which is used in folk medicine to treat pain and inflammatory diseases. This study aimed to evaluate the anti-inflammatory activity of solidagenone in vitro and in a model of allergic airway inflammation. In vitro studies were performed in activated macrophages and lymphocytes. BALB/c mice were sensitized and challenged with ovalbumin and treated with solidagenone orally (30 or 90 mg/kg body weight) or dexamethasone, as a positive control in our in vivo analysis. Supernatant concentrations of nitrite, TNF and IL-1β, as well as gene expression of pro-inflammatory mediators in macrophages cultures, were reduced after solidagenone treatment, without affecting macrophages viability. Besides, solidagenone significantly decreased T cell proliferation and secretion of IFNγ and IL-2. Th2 cytokine concentrations and inflammatory cell counts, especially eosinophils, in bronchoalveolar lavage fluid were reduced in mice treated with solidagenone. Histopathological evaluation of lung tissue was performed, and morphometrical analyses demonstrated reduction of cellular infiltration and mucus hypersecretion. Altogether, solidagenone presented anti-inflammatory activity in vitro and in vivo in the OVA-induced airway inflammation model, suggesting its promising pharmacological use as an anti-inflammatory agent for allergic hypersensitivity.

Nutraceuticals: unlocking newer paradigms in the mitigation of inflammatory lung diseases

Persistent respiratory tract inflammation contributes to the pathogenesis of various chronic respiratory diseases, such as asthma, chronic obstructive pulmonary disease, and pulmonary fibrosis. These inflammatory respiratory diseases have been a major public health concern as they are the leading causes of worldwide mortality and morbidity, resulting in heavy burden on socioeconomic growth throughout these years. Although various therapeutic agents are currently available, the clinical applications of these agents are found to be futile due to their adverse effects, and most patients remained poorly controlled with a low quality of life. These drawbacks have necessitated the development of novel, alternative therapeutic agents that can effectively improve therapeutic outcomes. Recently, nutraceuticals such as probiotics, vitamins, and phytochemicals have gained increasing attention due to their nutritional properties and therapeutic potential in modulating the pathological mechanisms underlying inflammatory respiratory diseases, which could ultimately result in improved disease control and overall health outcomes. As such, nutraceuticals have been held in high regard as the possible alternatives to address the limitations of conventional therapeutics, where intensive research are being performed to identify novel nutraceuticals that can positively impact various inflammatory respiratory diseases. This review provides an insight into the utilization of nutraceuticals with respect to their molecular mechanisms targeting multiple signaling pathways involved in the pathogenesis of inflammatory respiratory diseases.

Efficacy of Tezepelumab in Patients with Severe, Uncontrolled Asthma and Perennial Allergy

BACKGROUND

Tezepelumab is an anti-thymic stromal lymphopoietin monoclonal antibody. In the PATHWAY phase IIb study (NCT02054130), tezepelumab significantly reduced annualized asthma exacerbation rates (AAERs) versus placebo in adults with severe, uncontrolled asthma.

OBJECTIVE

This post hoc analysis assessed the efficacy of tezepelumab in PATHWAY participants with perennial allergy.

METHODS

Adults (N=550) with severe, uncontrolled asthma were randomized to receive tezepelumab (70 mg or 210 mg every 4 weeks or 280 mg every 2 weeks) or placebo, for 52 weeks. The AAER over 52 weeks was analyzed in patients grouped by sensitivity to perennial aeroallergens and by eligibility for omalizumab treatment according to the US or EU prescribing information. Change from baseline to week 52 in pre-bronchodilator forced expiratory volume in 1 second (FEV₁) and type 2 (T2) biomarkers were assessed in the perennial allergy subgroups.

RESULTS

Across doses, tezepelumab reduced the AAER versus placebo by 66-78% in patients with perennial allergy (n=254) and 67-71% in patients without perennial allergy (n=261). Tezepelumab improved pre-bronchodilator FEV₁ and reduced blood eosinophil counts and fractional exhaled nitric oxide levels over 52 weeks, irrespective of perennial allergy status. Tezepelumab reduced the AAER versus placebo by 61-82% in omalizumab-eligible patients (US, n=159; EU, n=101) and 63-70% in omalizumab-ineligible patients (US, n=372; EU, n=440), respectively.

CONCLUSIONS

Treatment with tezepelumab reduced exacerbations, improved lung function and reduced T2 biomarkers versus placebo in patients with severe, uncontrolled asthma with or without perennial allergy, further supporting its efficacy in a broad population of patients with severe, uncontrolled asthma.

Understanding the key issues in the treatment of uncontrolled persistent asthma with type 2 inflammation

Asthma is a complex respiratory disease that varies in severity and response to treatment. Several asthma phenotypes with unique clinical and inflammatory characteristics have been identified. Endotypes, based on distinct molecular profiles, help to further elucidate the heterogeneity within asthma. Type 2 inflammation, involving both the innate (type 2 innate lymphoid cell) and adaptive (T-helper type 2 cells) immune systems, underpins the complex pathophysiology of chronic inflammation in asthma, as well as the presence of comorbid disease (e.g. chronic rhinosinusitis with nasal polyps, allergic rhinitis and atopic dermatitis). Type 2 inflammation is characterised by upregulation of the type 2 cytokines interleukin (IL)-4, IL-5 and IL-13, IgE-mediated release of immune mediators and dysfunction of epithelial or epidermal barriers. Targeting these key proximal type 2 cytokines has shown efficacy in recent studies adopting a personalised approach to treatment using targeted biologics. Elevated levels of biomarkers downstream of type 2 cytokines, including fractional exhaled nitric oxide, serum IgE and blood and sputum eosinophils, have been linked to mechanisms involved in type 2 inflammation. They have the potential to aid diagnosis, and to predict and monitor response to treatment. The objective of this review is to summarise the current understanding of the biology of type 2 inflammation in asthma, examine its influence on type 2 inflammatory comorbidities, and discuss how type 2 inflammatory biomarkers can be harnessed to further personalise treatments in the age of biologic medicines.

Neuroimmune regulatory networks of the airway mucosa in allergic inflammatory disease

Communication between the nervous and immune systems serves a key role in host‐protective immunity at mucosal barrier sites including the respiratory tract. In these tissues, neuroimmune interactions operate in bidirectional circuits that can sense and respond to mechanical, chemical, and biologic stimuli. Allergen‐ or helminth‐induced products can produce airway inflammation by direct action on nociceptive afferents and adjacent tissues. The activity of nociceptive afferents can regulate innate and adaptive immune responses via neuropeptides and neurotransmitter signaling. This review will summarize recent work investigating the role of neuropeptides CGRP, VIP, neuromedins, substance P, and neurotransmitters dopamine and the B2‐adrenoceptor agonists epinepherine/norepinepherine, each of which influence type 2 immunity by instructing mast cell, innate lymphoid cell type 2, dendritic cell, and T cell responses, both in the airway and the draining lymph node. Afferents in the airway also contain receptors for alarmins and cytokines, allowing their activity to be modulated by immune cell secreted products, particularly those secreted by mast cells. Taken together, we propose that further investigation of how immunoregulatory neuropeptides shape respiratory inflammation in experimental systems may reveal novel therapeutic targets for addressing the increasing prevalence of chronic airway disease in humans.

Identification and treatment of T2-low asthma in the era of biologics

Currently, and based on the development of relevant biologic therapies, T2-high is the most well-defined endotype of asthma. Although much progress has been made in elucidating T2-high inflammation pathways, no specific clinically applicable biomarkers for T2-low asthma have been identified. The therapeutic approach of T2-low asthma is a problem urgently needing resolution, firstly because these patients have poor response to steroids, and secondly because they are not candidates for the newer targeted biologic agents. Thus, there is an unmet need for the identification of biomarkers that can help the diagnosis and endotyping of T2-low asthma. Ongoing investigation is focusing on neutrophilic airway inflammation mediators as therapeutic targets, including interleukin (IL)-8, IL-17, IL-1, IL-6, IL-23 and tumour necrosis factor-α; molecules that target restoration of corticosteroid sensitivity, mainly mitogen-activated protein kinase inhibitors, tyrosine kinase inhibitors and phosphatidylinositol 3-kinase inhibitors; phosphodiesterase (PDE)3 inhibitors that act as bronchodilators and PDE4 inhibitors that have an anti-inflammatory effect; and airway smooth muscle mass attenuation therapies, mainly for patients with paucigranulocytic inflammation. This article aims to review the evidence for noneosinophilic inflammation being a target for therapy in asthma; discuss current and potential future therapeutic approaches, such as novel molecules and biologic agents; and assess clinical trials of licensed drugs in the treatment of T2-low asthma.

Asthmatics with concordant eosinophilic disease classified according to their serum IgE status

BACKGROUND

Eosinophilic inflammation has long been associated with asthma. Looking at systemic and airway eosinophilia, we have recently identified a group of patients exhibiting diffuse eosinophilic inflammation. Among the mechanisms governing eosinophilic inflammation, IgE-mediated mast cell activation is a key event leading to eosinophilia in atopic asthmatics.

METHODS

We conducted a retrospective study on our asthma clinic database containing more than 1500 patients and identified 205 asthmatics with successful sputum induction and concordant eosinophilic phenotype. This phenotype was defined as a sputum eosinophil count≥3% and a blood eosinophils concentration≥400cells/mm³. IgE-high atopic phenotype was characterized by the presence of at least one positive specific IgE (>0.35kU/L) to common aeroallergens and a raised total serum IgE (≥113kU/L).

RESULTS

The largest group of asthmatics displaying concordant eosinophilic phenotype had a raised total serum IgE and atopy (45%). IgE-low non-atopic concordant eosinophilic asthma was a predominantly late onset disease, exhibited a more intense airway eosinophilic inflammation (P<0.05), required more often maintenance treatment with oral corticosteroids (P<0.05) but, surprisingly, had a reduced level of bronchial hyperresponsiveness to methacholine (P<0.05) despite similar baseline airway calibre impairment.

CONCLUSION

The more severe airway eosinophilic inflammation in IgE-low non-atopic asthmatics despite similar treatment with ICS and a higher burden of OCS points to a certain corticosteroid resistance in this asthma phenotype.

Pathogenesis and Persistence of Increased Epithelial Mucosubstances in the Nasal Airways of Rats and Mice Episodically Exposed to Ethylene

Rats repeatedly exposed to high airborne concentrations of ethylene develop eosinophilic rhinitis and mucous cell hyperplasia/hypertrophy (MCH) in nasal respiratory epithelium. Mechanisms underlying these lesions are not well understood to inform occupational exposure guidelines. In this study, we determined (1) the nasal histopathology in rats episodically exposed to ethylene, (2) the ethylene-induced nasal histopathology in similarly exposed mice, and (3) how innate lymphoid cells (ILCs) play a role in ethylene-induced MCH. Animals were exposed to 0 or 10,000 ppm ethylene, 6 h/d, 5 d/wk, for 2 weeks and sacrificed 1 day or 2 weeks postexposure. Others received three 2-week exposure blocks separated by 2-week intervals of no exposure. Episodic exposure was chosen to aid in distinguishing irritant from immune responses. Mucous cell hyperplasia/hypertrophy was induced by ethylene in both species. Rats developed a mild, but transient, eosinophilic rhinitis. Mucous cell hyperplasia/hypertrophy was transient in mice, but persistent in rats. Increases in epithelial mucosubstances after 2 weeks of exposure were only present in ILC-sufficient mice, but not in ILC-deficient mice suggesting that ILCs play a role in MCH and overexpression of genes associated with mucus production/secretion. These findings in animals suggest that inhaled ethylene does not act as a sensitizing agent and will not induce allergen-like nasal airway disease.

Epigenetics and the Environment in Airway Disease: Asthma and Allergic Rhinitis

Asthma and rhinitis are complex, heterogeneous diseases characterized by chronic inflammation of the upper and lower airways. While genome-wide association studies (GWAS) have identified a number of susceptible loci and candidate genes associated with the pathogenesis of asthma and allergic rhinitis (AR), the risk-associated alleles account for only a very small percent of the genetic risk. In allergic airway and other complex diseases, it is thought that epigenetic modifications, including DNA methylation, histone modifications, and non-coding microRNAs, caused by complex interactions between the underlying genome and the environment may account for some of this "missing heritability" and may explain the high degree of plasticity in immune responses. In this chapter, we will focus on the current knowledge of classical epigenetic modifications, DNA methylation and histone modifications, and their potential role in asthma and AR. In particular, we will review epigenetic variations associated with maternal airway disease, demographics, environment, and non-specific associations. The role of specific genetic haplotypes in environmentally induced epigenetic changes are also discussed. A major limitation of many of the current studies of asthma epigenetics is that they evaluate epigenetic modifications in both allergic and non-allergic asthma, making it difficult to distinguish those epigenetic modifications that mediate allergic asthma from those that mediate non-allergic asthma. Additionally, most DNA methylation studies in asthma use peripheral or cord blood due to poor accessibility of airway cells or tissue. Unlike DNA sequences, epigenetic alterations are quite cell- and tissue-specific, and epigenetic changes found in airway tissue or cells may be discordant from that of circulating blood. These two confounding factors should be considered when reviewing epigenetic studies in allergic airway disease.

Innate lymphoid cell and adaptive immune cell cross-talk: A talk meant not to forget

Innate lymphoid cells (ILCs) are a relatively new class of innate immune cells with phenotypical characters of lymphocytes but genotypically or functionally behave as typical innate immune cells. They have been classically divided into 3 groups (group 1 ILCs or ILC1s, group 2 ILCs or ILC2s, and group 3 ILCs or ILC3s). They serve as the first line of defense against invading pathogens and allergens at mucosal surfaces. The adaptive immune response works effectively in association with innate immunity as innate immune cells serve as APCs to directly stimulate the adaptive immune cells (various sets of T and B cells). Additionally, innate immune cells also secrete various effector molecules, including cytokines or chemokines impacting the function, differentiation, proliferation, and reprogramming among adaptive immune cells to maintain immune homeostasis. Only superantigens do not require their processing by innate immune cells as they are recognized directly by T cells and B cells. Thus, a major emphasis of the current article is to describe the cross-talk between different ILCs and adaptive immune cells during different conditions varying from normal physiological situations to different infectious diseases to allergic asthma.

Targeting the interleukin-7 receptor alpha by an anti-CD127 monoclonal antibody improves allergic airway inflammation in mice

BACKGROUND

Interleukin-7 (IL-7) is the most important cytokine for T-cell homeostasis. IL-7 signals through the IL-7 receptor (IL-7R) which is composed of an alpha chain (IL-7Rα), also called CD127 and a common gamma chain. T lymphocytes, especially T helper type 2, play a crucial role in the pathobiology of allergic asthma.

OBJECTIVE

To study the effects of an anti-CD127 monoclonal antibody (mAb) in a murine model of allergic airway inflammation induced by house dust mite (HDM).

METHODS

Allergic airway inflammation was induced in mice using a protocol comprising 4 weekly percutaneous sensitizations followed by 2 weekly intranasal challenges with total HDM extracts and treated by intraperitoneal injections of an anti-CD127 mAb. Because CD127 is shared by both IL-7R and the receptor for thymic stromal lymphopoietin (TSLP), a group of mice was also treated with an anti-IL-7 mAb to block only the IL-7 signalling pathway.

RESULTS

Anti-CD127 mAb-treated mice showed significantly lower airway resistance in response to methacholine and improvement in lung histology compared with isotype mAb-treated animals. Anti-CD127 mAb treatment significantly decreased the mRNA expression of Th2 cytokines (IL-4, IL-5, and IL-13) and chemokines (CCL5/RANTES) in lung tissue, decreased the secretion of Th2 cytokines (IL-4, IL-5, and IL-13) and chemokines (CXCL1 and CCL11/eotaxin) in bronchoalveolar lavage fluid (BALF), decreased serum HDM-specific IgE, and reduced the number of total leucocytes and leucocyte subpopulations such as eosinophils, macrophages, lymphocytes, T lymphocytes, and ILC2 in BALF and lung tissue. Mice treated with anti-IL-7 mAb also showed less allergic airway inflammation as evidenced by significantly lower airway resistance and fewer leucocytes in BALF and lung tissue compared to mice treated with the corresponding isotype control mAb.

CONCLUSION AND CLINICAL RELEVANCE

Targeting the IL-7Rα by an anti-CD127 mAb improves allergic airway inflammation in mice and presents as a potential therapeutic approach for allergic asthma.

Acupuncture inhibited airway inflammation and group 2 innate lymphoid cells in the lung in an ovalbumin-induced murine asthma model

BACKGROUND

Group 2 innate lymphoid cells (ILC2s) are known to serve important functions in the pathogenesis of allergic airway inflammation. Studies have shown that acupuncture has an anti-inflammatory effect in the airways. However, how acupuncture treatment affects innate immunity, especially with regard to the function of ILC2s in ovalbumin (OVA)-induced allergic airway inflammation, is poorly understood.

METHODS

BALB/c mice were injected and subsequently challenged with OVA ± treated with manual acupuncture. At the end of the experimental course, lung function was assessed by measurement of airway resistance (R_L) and lung dynamic compliance (Cdyn). Cytokine levels were detected by enzyme-linked immunosorbent assay (ELISA). ILC2 proportions in the lung were analyzed by flow cytometry.

RESULTS

The results showed that airway inflammation and mucus secretion were significantly suppressed by acupuncture treatment. R_L decreased while Cdyn increased after acupuncture treatment. There was an apparent decrease in the bronchoalveolar lavage fluid (BALF) concentrations of interleukin (IL)-5, IL-13, IL-9, IL-25 and IL-33 and an increase in soluble IL-33 receptor (sST2) levels compared with untreated asthmatic mice. Acupuncture also reduced the lin^-CD45⁺KLRG1⁺ST2⁺ cell proportion in the lung.

CONCLUSION

In conclusion, this study has demonstrated that acupuncture treatment alleviates allergic airway inflammation and inhibits pulmonary ILC2 influx and IL-5, IL-9 and IL-13 production. The inhibition of ILC2s by acupuncture may be associated with the IL-33/ST2-signaling pathway and IL-25 levels, thereby offering protection from the respiratory inflammation associated with asthma.

The Future of Asthma Care: Personalized Asthma Treatment

Although once considered a single disease entity, asthma is now known to be a complex inflammatory disease engaging a range of causal pathways. The most frequent forms of asthma are identified by sputum/blood eosinophilia and activation of type 2 inflammatory pathways involving interleukins-3, -4, -5, and granulocyte-macrophage colony-stimulating factor. The use of diagnostics that identify T2 engagement linked to the selective use of highly targeted biologics has opened up a new way of managing severe disease. Novel technologies, such as wearables and intelligent inhalers, enable real-time remote monitoring of asthma, creating a unique opportunity for personalized health care.

Eighty-eight variants highlight the role of T cell regulation and airway remodeling in asthma pathogenesis

Asthma is one of the most common chronic diseases affecting both children and adults. We report a genome-wide association meta-analysis of 69,189 cases and 702,199 controls from Iceland and UK biobank. We find 88 asthma risk variants at 56 loci, 19 previously unreported, and evaluate their effect on other asthma and allergic phenotypes. Of special interest are two low frequency variants associated with protection against asthma; a missense variant in TNFRSF8 and 3‘ UTR variant in TGFBR1. Functional studies show that the TNFRSF8 variant reduces TNFRSF8 expression both on cell surface and in soluble form, acting as loss of function. eQTL analysis suggests that the TGFBR1 variant acts through gain of function and together with an intronic variant in a downstream gene, SMAD3, points to defective TGFβR1 signaling as one of the biological perturbations increasing asthma risk. Our results increase the number of asthma variants and implicate genes with known role in T cell regulation, inflammation and airway remodeling in asthma pathogenesis.

Asthma is a common allergic airway disease with significant inter-individual heterogeneity. Here, Olafsdottir et al. report a genome-wide meta-analysis of two large population-based cohorts to identify sequence variants that associate with asthma risk and perform follow-up functional analyses on a protective loss-of-function variant in TNFRSF8.

MicroRNA-146a negatively regulates IL-33 in activated group 2 innate lymphoid cells by inhibiting IRAK1 and TRAF6

Type II innate lymphoid cells (ILC2) play a very important role in the pathogenesis of allergic asthma. This study aims to investigate whether miR-146a inhibition of asthma is related with interleukin (IL)-33 signaling path way in ILC2 and the underlying mechanisms. Asthma mice model was induced by ovalbumin. miRNA146a mimics was administrated to asthma mice or transfected to activated ILC2 purified from asthma mice lung. RT-PCR was used to detect miRNA146a level in lung tissue and ILC2. IL-5 and IL-13 levels in culture supernatant were detected by flow cytometry. Interleukin-1 receptor-associated kinase 1 (IRAK1), TNF receptor-associated factor 6 (TRAF6), signal transducer and activator of transcription 1 (STAT1) protein expression levels were detected by western blot. miR-146a directly inhibited ILC2 function and suppressed ILC2 proliferation both in vivo and in vitro. During stimulation of ILC2, miR-146a expression gradually increased with a decrease of cell proliferation. Modulation of ILC2 function by miR-146a may depend on IL-33/interleukin 1 receptor-like 1 (IL1RL1 or ST2) signaling through inhibiting IRAK1 and TRAF6.miR-146a can inhibit IRAK1 and TRAF6, downstream molecules of ST2 signal pathway, thereby negatively regulate IL-33/ST2-activated ILC2 to inhibit asthma. Targeting miR-146 maybe a novel strategy for the treatment of allergic asthma.

Innate Lymphoid Cells in the Airways: Their Functions and Regulators

Since the airways are constantly exposed to various pathogens and foreign antigens, various kinds of cells in the airways—including structural cells and immune cells—interact to form a precise defense system against pathogens and antigens that involve both innate immunity and acquired immunity. Accumulating evidence suggests that innate lymphoid cells (ILCs) play critical roles in the maintenance of tissue homeostasis, defense against pathogens and the pathogenesis of inflammatory diseases, especially at body surface mucosal sites such as the airways. ILCs are activated mainly by cytokines, lipid mediators and neuropeptides that are produced by surrounding cells, and they produce large amounts of cytokines that result in inflammation. In addition, ILCs can change their phenotype in response to stimuli from surrounding cells, which enables them to respond promptly to microenvironmental changes. ILCs exhibit substantial heterogeneity, with different phenotypes and functions depending on the organ and type of inflammation, presumably because of differences in microenvironments. Thus, ILCs may be a sensitive detector of microenvironmental changes, and analysis of their phenotype and function at local sites may enable us to better understand the microenvironment in airway diseases. In this review, we aimed to identify molecules that either positively or negatively influence the function and/or plasticity of ILCs and the sources of the molecules in the airways in order to examine the pathophysiology of airway inflammatory diseases and facilitate the issues to be solved.

The Influence of Innate Lymphoid Cells and Unconventional T Cells in Chronic Inflammatory Lung Disease

The lungs are continuously subjected to environmental insults making them susceptible to infection and injury. They are protected by the respiratory epithelium, which not only serves as a physical barrier but also a reactive one that can release cytokines, chemokines, and other defense proteins in response to danger signals, and can undergo conversion to protective mucus-producing goblet cells. The lungs are also guarded by a complex network of highly specialized immune cells and their mediators to support tissue homeostasis and resolve integrity deviation. This review focuses on specialized innate-like lymphocytes present in the lung that act as key sensors of lung insults and direct the pulmonary immune response. Included amongst these tissue-resident lymphocytes are innate lymphoid cells (ILCs), which are classified into five distinct subsets (natural killer, ILC1, ILC2, ILC3, lymphoid tissue-inducer cells), and unconventional T cells including natural killer T (NKT) cells, mucosal-associated invariant T (MAIT) cells, and γδ-T cells. While ILCs and unconventional T cells together comprise only a small proportion of the total immune cells in the lung, they have been found to promote lung homeostasis and are emerging as contributors to a variety of chronic lung diseases including pulmonary fibrosis, allergic airway inflammation, and chronic obstructive pulmonary disease (COPD). A particularly intriguing trait of ILCs that has recently emerged is their plasticity and ability to alter their gene expression profiles and adapt their function in response to environmental cues. The malleable nature of these cells may aid in rapid responses to pathogen but may also have downstream pathological consequences. The role of ILC2s in Th2 allergic airway responses is becoming apparent but the contribution of other ILCs and unconventional T cells during chronic lung inflammation is poorly described. This review presents an overview of our current understanding of the involvement of ILCs and unconventional T cells in chronic pulmonary diseases.

Effect of mepolizumab in severe eosinophilic asthma according to omalizumab eligibility

BACKGROUND

Patients with severe asthma can present with overlapping eosinophilic and allergic phenotypes, which makes it challenging when deciding which biologic therapy is most appropriate to reduce exacerbations and help achieve asthma control.

OBJECTIVE

This post hoc meta-analysis evaluated the efficacy of the licensed dose of mepolizumab (100 mg administered subcutaneously [SC]) versus placebo in patients with severe eosinophilic asthma (SEA), according to omalizumab eligibility and associated allergic characteristics.

METHODS

Data from two Phase 3 studies (MENSA [MEA115588/NCT01691521]; MUSCA [200862/NCT02281318]) were analyzed. Patients ≥12 years of age with SEA who experienced ≥2 exacerbations in the previous year received placebo, mepolizumab 100 mg SC or 75 mg intravenously, plus standard of care (high-dose inhaled corticosteroids and other controllers), every 4 weeks. Data from patients who received ≥1 dose placebo or mepolizumab 100 mg SC were used for this analysis. The primary endpoint was the rate of clinically significant exacerbations; other outcomes included forced expiratory volume in 1 s (FEV₁), Asthma Control Questionnaire (ACQ-5) score and quality of life measured using St George's Respiratory Questionnaire (SGRQ).

RESULTS

Rate reductions in clinically significant exacerbations with mepolizumab versus placebo were similar in omalizumab eligible and ineligible patients (57% vs 55%). FEV₁, ACQ-5 and SGRQ scores improved with mepolizumab versus placebo regardless of omalizumab eligibility, Immunoglobulin E levels, or atopic status.

CONCLUSION

This analysis indicated that mepolizumab 100 mg SC has clinical benefit in patients with blood eosinophil counts ≥150 cells/μL (or history of ≥300 cells/μL), regardless of allergic characteristics or omalizumab eligibility.

T cells in severe childhood asthma

Severe asthma in children is a debilitating condition that accounts for a disproportionately large health and economic burden of asthma. Reasons for the lack of a response to standard anti-inflammatory therapies remain enigmatic. Work in the last decade has shed new light on the heterogeneous nature of asthma, and the varied immunopathologies of severe disease, which are leading to new treatment approaches for the individual patient. However, most studies to date that explored the immune landscape of the inflamed lower airways have focused on adults. T cells are pivotal to the inception and persistence of inflammatory processes in the diseased lungs, despite a contemporary shift in focus to immune events at the epithelial barrier. This article outlines current knowledge on the types of T cells and related cell types that are implicated in severe asthma. The potential for environmental exposures and other inflammatory cues to condition the immune environment of the lung in early life to favour pathogenic T cells and steroid resistance is discussed. The contributions of T cells and their cytokines to inflammatory processes and treatment resistance are also considered, with an emphasis on new observations in children that argue against conventional type 1 and type 2 T cell paradigms. Finally, the ability for new technologies to revolutionize our understanding of T cells in severe childhood asthma, and to guide future treatment strategies that could mitigate this disease, is highlighted.

IL-33, IL-25 and TSLP contribute to development of fungal-associated protease-induced innate-type airway inflammation

Certain proteases derived from house dust mites and plants are considered to trigger initiation of allergic airway inflammation by disrupting tight junctions between epithelial cells. It is known that inhalation of proteases such as house dust mite-derived Der p1 and/or papaya-derived papain caused airway eosinophilia in naïve mice and even in Rag-deficient mice that lack acquired immune cells such as T, B and NKT cells. In contrast, little is known regarding the possible involvement of proteases derived from Aspergillus species (fungal-associated proteases; FAP), which are ubiquitous saprophytic fungi in the environment, in the development of allergic airway eosinophilia. Here, we found that inhalation of FAP by naïve mice led to airway eosinophilia that was dependent on protease-activated receptor-2 (PAR2), but not TLR2 and TLR4. Those findings suggest that the protease activity of FAP, but not endotoxins in FAP, are important in the setting. In addition, development of that eosinophilia was mediated by innate immune cells (ILCs) such as innate lymphoid cells, but not by acquired immune cells such as T, B and NKT cells. Whereas IL-33, IL-25 and thymic stromal lymphopoietin (TSLP) are involved in induction of FAP-induced ILC-mediated airway eosinophilia, IL-33-rather than IL-25 and/or TSLP-was critical for the eosinophilia in our model. Our findings improve our understanding of the molecular mechanisms involved in induction of airway inflammation by FAP.

Obesity May Provide Pro-ILC3 Development Inflammatory Environment in Asthmatic Children

The prevalence of obesity in children has dramatically increased in the last few decades, and obesity has also emerged as an important risk factor for asthma. Innate mechanisms have been shown to be involved in both diseases, particularly through the recently described innate lymphoid cells (ILCs), in which ILC3s have been linked to obesity both in human and in murine models. The aim of this study was to explore whether being overweight in asthmatic children was associated with elevated circulating ILC3 or elevated messenger RNA (mRNA) levels of RORC, IL-17A, and IL-22. Our results showed significantly elevated ILC3 frequencies in overweight asthmatic children compared with nonoverweight controls based on the detection of Lin+CD127+IL-23R+ cells by flow cytometry. Moreover, elevated ILC3 frequencies positively correlated with the mRNA expression of RORC which has been identified as a transcription factor of ILC3s. The relative mRNA expression level of IL-17A was also upregulated in overweight compared to nonoverweight children, as was the relative mRNA level of IL-22. However, there were no correlations between ILC3 frequencies or the expressions of RORC, IL-17A, and IL-22 and asthma severity. These results suggested that childhood obesity is an independent factor that is associated with an elevated frequency of circulating ILC3s and higher expressions of RORC, IL-22, and IL-17A.

Fixed airflow obstruction relates to eosinophil activation in asthmatics

BACKGROUND

Some asthmatics develop irreversible chronic airflow obstruction, for example, fixed airflow obstruction (fixed-AO). This is probably a consequence of airway remodelling, but neither its relation to inflammation nor which asthma biomarkers can be clinically useful are elucidated. We hypothesized that the presence of type 2 inflammation relates to fixed-AO.

OBJECTIVES

To evaluate the presence of four markers for type 2 inflammation in fixed airflow obstruction among asthmatics.

METHODS

This was a cross-sectional study of 403 participants with asthma, aged 17-75 years, from three Swedish centres. Fixed airflow obstruction was defined as forced expiratory volume during the first second (FEV₁ ) over forced vital capacity (FVC) being below the lower limit of normal (LLN). The following type 2 inflammation markers were assessed: exhaled nitric oxide (FeNO), serum periostin, serum eosinophil cationic protein (S-ECP), and urinary eosinophil-derived neurotoxin (U-EDN).

RESULTS

Elevated U-EDN (values in the highest tertile, ≥65.95 mg/mol creatinine) was more common in subjects with fixed-AO vs. subjects without fixed-AO: 55% vs. 29%, P < 0.001. Elevated U-EDN related to increased likelihood of having fixed-AO in both all subjects and never-smoking subjects, with adjusted (adjusted for sex, age group, use of inhaled corticosteroids last week, atopy, early-onset asthma, smoking history, and packyears) odds ratios (aOR) of 2.38 (1.28-4.41) and 2.51 (1.04-6.07), respectively. In a separate analysis, having both elevated S-ECP (>20 μg/L) and U-EDN was related to having the highest likelihood of fixed-AO (aOR (95% CI) 6.06 (2.32-15.75)). Elevated serum periostin or FeNO did not relate to fixed-AO.

CONCLUSIONS AND CLINICAL RELEVANCE

These findings support that type 2 inflammation, and in particular eosinophil inflammation, is found in asthma with fixed-AO. This could indicate a benefit from eosinophil-directed therapies. Further longitudinal studies are warranted to investigate causality and relation to lung function decline.

Epigenetic Regulation via Altered Histone Acetylation Results in Suppression of Mast Cell Function and Mast Cell-Mediated Food Allergic Responses

Mast cells are highly versatile cells that perform a variety of functions depending on the immune trigger, context of activation, and cytokine stimulus. Antigen-mediated mast cell responses are regulated by transcriptional processes that result in the induction of numerous genes contributing to mast cell function. Recently, we also showed that exposure to dietary agents with known epigenetic actions such as curcumin can suppress mast cell-mediated food allergy, suggesting that mast cell responses in vivo may be epigenetically regulated. To further assess the effects of epigenetic modifications on mast cell function, we examined the behavior of bone marrow-derived mast cells (BMMCs) in response to trichostatin A (TSA) treatment, a well-studied histone deacetylase inhibitor. IgE-mediated BMMC activation resulted in enhanced expression and secretion of IL-4, IL-6, TNF-α, and IL-13. In contrast, pretreatment with TSA resulted in altered cytokine secretion. This was accompanied by decreased expression of FcεRI and mast cell degranulation. Interestingly, exposure to non-IgE stimuli such as IL-33, was also affected by TSA treatment. Furthermore, continuous TSA exposure contributed to mast cell apoptosis and a decrease in survival. Further examination revealed an increase in I-κBα and a decrease in phospho-relA levels in TSA-treated BMMCs, suggesting that TSA alters transcriptional processes, resulting in enhancement of I-κBα transcription and decreased NF-κB activation. Lastly, treatment of wild-type mice with TSA in a model of ovalbumin-induced food allergy resulted in a significant attenuation in the development of food allergy symptoms including decreases in allergic diarrhea and mast cell activation. These data therefore suggest that the epigenetic regulation of mast cell activation during immune responses may occur via altered histone acetylation, and that exposure to dietary substances may induce epigenetic modifications that modulate mast cell function.

Birch pollen-specific subcutaneous immunotherapy reduces ILC2 frequency but does not suppress IL-33 in mice

BACKGROUND

The underlying mechanism of allergen-specific subcutaneous immunotherapy (SCIT) is not yet fully understood, but suppression of allergen-specific Th2 cells and production of allergen-specific IgG4 antibodies are two hallmarks. The impact on the innate arm of the immune system is far less clear.

OBJECTIVE

The aim of this study was to investigate the effect of birch pollen (BP) SCIT on the innate immune response in a BP SCIT mouse model.

METHODS

Mice with birch pollen-induced allergic airway inflammation received weekly subcutaneous immunotherapy injections with birch pollen extract (BPE) adsorbed to alum. The effect of the BP SCIT on innate cytokine levels in lung, the number and the functionality of ILC2s and the airway inflammation was determined.

RESULTS

Mice with BP allergy had an increased level of the innate cytokines IL-33, IL-25, GM-CSF and IL-5⁺ ILC2s in the lungs. BP SCIT suppressed the number of IL-5⁺ ILC2s, mast cell tryptase release, Th2 cytokine production, eosinophil recruitment and peribronchial inflammatory infiltrates. In contrast, innate cytokine production and collagen deposition in the airways were not affected.

CONCLUSION AND CLINICAL RELEVANCE

BP SCIT is able to suppress the adaptive and part of the innate immune response, but this is not sufficient to inhibit collagen deposition and the IL-33 expression in the airways in mice.

miR-146a Mimics Attenuate Allergic Airway Inflammation by Impacted Group 2 Innate Lymphoid Cells in an Ovalbumin-Induced Asthma Mouse Model

BACKGROUND

The prevalence of allergic asthma has increased dramatically. Previous studies have found that the microRNA 146a (miR-146a) expression in asthma inhibits cell proliferation and promotes apoptosis of bronchial smooth muscle cells. We aimed to investigate the effect of miR-146a mimics on ovalbumin (OVA)-induced asthma in a mouse model.

METHODS

Inflammatory cell infiltration in bronchoalveolar lavage fluid (BALF) was measured by flow cytometry. Levels of OVA-specific immunoglobulin E (IgE) in serum and cytokines in BALF were examined by enzyme-linked immunosorbent assay. For monitoring the airway, the Penh value (% baseline) was measured using a whole-body plethysmograph.

RESULTS

In OVA-induced asthmatic mice, miR-146a significantly suppressed the infiltration of inflammatory cells in BALF and decreased the levels of OVA-specific IgE and T helper 2 cell type cytokines. In addition, miR-146a inhibited the OVA-induced airway hyperresponsiveness and the group 2 innate lymphoid cell responses. Moreover, the effects of miR-146a mimics were dependent on interleukin 33 stimulation.

CONCLUSIONS

Our results suggest that miR-146a mimics might serve as an attractive candidate for further preclinical studies as an anti-inflammatory treatment of asthma.

Soluble ST2 regulation by rhinovirus and 25(OH)-vitamin D3 in the blood of asthmatic children

Paediatric asthma exacerbations are often caused by rhinovirus (RV). Moreover, 25(OH)-vitamin D3 (VitD3) deficiency during infancy was found associated with asthma. Here, we investigated the innate immune responses to RV and their possible modulation by 25(OH)-VitD3 serum levels in a preschool cohort of children with and without asthma. The innate lymphoid cell type 2 (ILC2)-associated marker, ST2, was found up-regulated in the blood cells of asthmatic children with low serum levels of 25(OH)-VitD3 in the absence of RV in their airways. Furthermore, in blood cells from control and asthmatic children with RV in their airways, soluble (s) ST2 (sST2) protein was found reduced. Asthmatic children with low 25(OH)-VitD3 in serum and with RV in vivo in their airways at the time of the analysis had the lowest sST2 protein levels in the peripheral blood compared to control children without RV and high levels of 25(OH)-VitD3. Amphiregulin (AREG), another ILC2-associated marker, was found induced in the control children with RV in their airways and low serum levels of 25(OH)-VitD3. In conclusion, the anti-inflammatory soluble form of ST2, also known as sST2, in serum correlated directly with interleukin (IL)-33 in the airways of asthmatic children. Furthermore, RV colonization in the airways and low serum levels of 25(OH)-VitD3 were found to be associated with down-regulation of sST2 in serum in paediatric asthma. These data indicate a counter-regulatory role of 25(OH)-VitD3 on RV-induced down-regulation of serum sST2 in paediatric asthma, which is relevant for the therapy of this disease.

A purinergic P2Y6 receptor agonist prodrug modulates airway inflammation, remodeling, and hyperreactivity in a mouse model of asthma

Background

Purinergic receptors control cell proliferation, apoptosis, migration, inflammation, and cytokine secretion. Increased expression of specific purinergic receptors is reported in asthma. The role of purinergic P2Y6 receptors (P2Y6R) in asthma is controversial.

Hypothesis

P2Y6R activation in asthma improves pulmonary function and reduces inflammation and smooth muscle amount.

Methods

Female mice (C57/BL6, age 30 days) were randomly assigned to receive intranasal house dust mite (HDM) antigen (40 or 80 µg) or saline, 5 days/week, for 6 weeks. Randomly selected subgroups received intraperitoneal P2Y6R agonist prodrug (GC021109; 10 or 100 µg/kg weight/dose) simultaneously with HDM. After 6 weeks, lung function was measured. Lung lavage fluid (LLF) was used to measure total cell count, total protein, and cytokines. Immunohistochemistry for alpha smooth muscle actin (α-SMA) was done. Airway wall thickness was measured on micro-computed tomography (micro-CT) images.

Results

Pulmonary function testing revealed a HDM dose-dependent airway hyperresponsiveness. Airway resistance was increased 2-fold while compliance was decreased by 50% at the higher HDM dose (P<0.05). GC021109 prevented these changes. HDM-exposed mice had elevated inflammatory cell and total protein levels in LLF which were prevented by GC021109 (P<0.05). HDM mice also had elevated LLF levels of interleukin (IL)-4, IL-5, IL-12, granulocyte colony stimulating factor, chemokine (C-X-C) motif ligand 1, and leukemia inhibitory factor that were reduced by GC021109 with a dose-dependent pattern. HDM mice had increased peribronchial and perivascular inflammatory cell infiltration and increased α-SMA; these changes were absent with GC021109. Airway wall thickness measured on micro-CT images was increased after HDM exposure and significantly reduced by GC021109 treatment.

Conclusion

The P2Y6R prodrug GC021109 inhibited allergen-induced changes in pulmonary function, inflammatory responses, and airway and vascular smooth muscle mass. P2Y6R activation may be an effective therapeutic maintenance strategy in asthma.

BCL11B mutations in patients affected by a neurodevelopmental disorder with reduced type 2 innate lymphoid cells

The transcription factor BCL11B is essential for development of the nervous and the immune system, and Bcl11b deficiency results in structural brain defects, reduced learning capacity, and impaired immune cell development in mice. However, the precise role of BCL11B in humans is largely unexplored, except for a single patient with a BCL11B missense mutation, affected by multisystem anomalies and profound immune deficiency. Using massively parallel sequencing we identified 13 patients bearing heterozygous germline alterations in BCL11B. Notably, all of them are affected by global developmental delay with speech impairment and intellectual disability; however, none displayed overt clinical signs of immune deficiency. Six frameshift mutations, two nonsense mutations, one missense mutation, and two chromosomal rearrangements resulting in diminished BCL11B expression, arose de novo. A further frameshift mutation was transmitted from a similarly affected mother. Interestingly, the most severely affected patient harbours a missense mutation within a zinc-finger domain of BCL11B, probably affecting the DNA-binding structural interface, similar to the recently published patient. Furthermore, the most C-terminally located premature termination codon mutation fails to rescue the progenitor cell proliferation defect in hippocampal slice cultures from Bcl11b-deficient mice. Concerning the role of BCL11B in the immune system, extensive immune phenotyping of our patients revealed alterations in the T cell compartment and lack of peripheral type 2 innate lymphoid cells (ILC2s), consistent with the findings described in Bcl11b-deficient mice. Unsupervised analysis of 102 T lymphocyte subpopulations showed that the patients clearly cluster apart from healthy children, further supporting the common aetiology of the disorder. Taken together, we show here that mutations leading either to BCL11B haploinsufficiency or to a truncated BCL11B protein clinically cause a non-syndromic neurodevelopmental delay. In addition, we suggest that missense mutations affecting specific sites within zinc-finger domains might result in distinct and more severe clinical outcomes.

Towards precision medicine in severe asthma: Treatment algorithms based on treatable traits

Asthma is a common disease, and although its clinical manifestations may be similar among patients, recent research discoveries have shown that it consists of several distinct clinical clusters or phenotypes, each with different underlying molecular pathways yielding different treatment responses. Based on these observations, an alternative approach - known as 'precision medicine' - has been proposed for the management of patients with severe asthma. Precision medicine advocates identification of treatable traits, linking them to therapeutic approaches targeting genetic, immunological, environmental, and/or lifestyle factors in individual patients. The main "goal" of this personalised approach is to enable choosing a treatment which will be more likely to produce a beneficial response in the individual patient rather than a 'one size fits all' approach. The aim of the present review is to discuss different ways of phenotyping asthma and to provide a rationale for treatment algorithms based on principles of precision medicine.

Type 2 immunity in asthma

Type 2-immunity represents the typical adaptive response to allergen exposure in atopic individuals. It mainly involves Th2 cells and immunoglobulin E, as the main orchestrators of type 2-inflammation. Recently, it has been highlighted that allergens may be responsible for a Th2 response beside specific IgE activation and that a number of other environmental stimuli, such as viruses and pollutants, can trigger the same pattern of inflammation beyond atopy. Emerging data sustain a substantial role of the so-called epithelial dysfunction in asthma pathogenesis, both from anatomic and functional point of view. Furthermore an increasing amount of evidence demonstrates the relevance of innate immunity in polarizing a Th2 impaired response in asthmatic patients. Under this perspective, the complex cross-talking between airway epithelium, innate and adaptive immunity is emerging as a major determinant of type 2-inflammation beyond allergens.

This review will include an update on the relevance of dysregulation of innate and adaptive type 2-immunity in asthma pathogenesis, particularly severe asthma, and on the role of the allergens that are associated with severe asthma. Type 2-immunity also will be reviewed in the light of the current and upcoming targeted treatments for severe asthma.

Progress in the understanding of the pathology of allergic asthma and the potential of fruit proanthocyanidins as modulators of airway inflammation

Allergic asthma is a chronic inflammatory lung disease characterized by sensitization of the airways, and the development of immunoglobulin E antibodies, to benign antigens. The established pathophysiology of asthma includes recurrent lung epithelial inflammation, excessive mucus production, bronchial smooth muscle hyperreactivity, and chronic lung tissue remodeling, resulting in reversible airflow restriction. Immune cells, including eosinophils and the recently characterized type 2 innate lymphoid cells, infiltrate into the lung tissue as part of the inflammatory response in allergic asthma. It is well established that a diet high in fruits and vegetables results in a reduction of the risk of developing inflammatory diseases. Secondary plant metabolites, such as proanthocyanidins which are found in apples, blackcurrants, boysenberries, cranberries, and grapes, have shown promising results in reducing or preventing allergic asthma airway inflammation. Recent evidence has also highlighted the importance of microbiome-mediated metabolism of plant polyphenols in modulating the immune system. In this review, we will discuss advances in our understanding of the pathophysiology of allergic asthma, including the role of the microbiome in lung immune function, and how proanthocyanidins modulate the airway inflammation. We will highlight the potential of dietary proanthocyanidins to impact on allergic asthma and the immune system.

Targeted Therapy for Severe Asthma: Identifying the Right Patients

Asthma affects over 300 million people worldwide. Most asthmatics are well controlled with inhaled corticosteroids and long-acting beta-agonists; however, a proportion of patients are unresponsive and attain limited disease control. This group represents a considerable healthcare and financial burden, particularly patients who experience frequent exacerbations and require hospital admission. Development of new biological agents and disease biomarkers has provided novel avenues for treatment. These treatments have been highly successful, reducing exacerbations and yielding modest improvements in quality of life and lung function. However, only a proportion of severe asthmatics respond to this targeted treatment, highlighting the heterogeneity of severe asthma. One of the first biological therapies targeted immunoglobulin E (IgE) and demonstrated modest benefit but could only be used in a subgroup of patients. Recent research has shown that treatment aimed at the T helper-2-(Th₂)-high pathways and cytokines such as interleukin (IL)-5, IL-4, and IL-13 may also be effective in another partially overlapping subgroup. A blood eosinophil count over a defined threshold (generally ≥300 cells/μl) was a reliable biomarker and identified the majority of responders in this group. Further discovery and validation of biological markers to define asthmatic phenotypes that may benefit from biological treatments remain an area of intense interest and research. We review the latest information pertaining to biological agents and demonstrate how patient responders may potentially be identified for treatment.

Targeted anti-IL-13 therapies in asthma: current data and future perspectives

INTRODUCTION

The identification of patients with severe asthma who will benefit from a personalized management approach remains an unmet need. Interleukin-13 (IL-13) is a cytokine possessing a significant role in asthma pathogenesis and progression of disease. Humanised monoclonal antibodies against IL-13 and IL-13 and IL-4 receptors are mainly proposed as add-on therapy in patients with T_H2-high inflammation with uncontrolled asthma despite maximum therapy.

AREAS COVERED

The role of IL-13 in airway inflammation in severe asthma, the targeted anti-IL-13 therapies and biomarkers that predict response to anti-IL-13 treatment are discussed.

EXPERT OPINION

New effective individualized therapies in severe asthma are urgently needed to block specific inflammatory pathways using monoclonal antibodies. Studies on anti-IL-13 therapies showed that asthmatic patients could benefit from this novel targeted therapy as far as lung function and exacerbation rate are concerned. T_H2-high and especially periostin-high groups of asthmatics with moderate-to-severe uncontrolled asthma seem to compose the group that could benefit from anti-IL-13 therapy. Targeting IL-13 alone may not be sufficient to achieve asthma control. Inhibition of IL-13 and IL-4 with mabs may be more encouraging and patients will probably have additional benefits from these therapeutic interventions because of IL-13/IL-4 overlapping actions in asthma pathophysiology.

Revisiting Type 2-high and Type 2-low airway inflammation in asthma: current knowledge and therapeutic implications

Asthma is a complex respiratory disorder characterized by marked heterogeneity in individual patient disease triggers and response to therapy. Several asthma phenotypes have now been identified, each defined by a unique interaction between genetic and environmental factors, including inflammatory, clinical and trigger-related phenotypes. Endotypes further describe the functional or pathophysiologic mechanisms underlying the patient's disease. type 2-driven asthma is an emerging nomenclature for a common subtype of asthma and is characterized by the release of signature cytokines IL-4, IL-5 and IL-13 from cells of both the innate and adaptive immune systems. A number of well-recognized biomarkers have been linked to mechanisms involved in type 2 airway inflammation, including fractional exhaled nitric oxide, serum IgE, periostin, and blood and sputum eosinophils. These type 2 cytokines are targets for pharmaceutical intervention, and a number of therapeutic options are under clinical investigation for the management of patients with uncontrolled severe asthma. Anticipating and understanding the heterogeneity of asthma and subsequent improved characterization of different phenotypes and endotypes must guide the selection of treatment to meet individual patients' needs.

Functions of tissue-resident eosinophils

Eosinophils are a prominent cell type in particular host responses such as the response to helminth infection and allergic disease. Their effector functions have been attributed to their capacity to release cationic proteins stored in cytoplasmic granules by degranulation. However, eosinophils are now being recognized for more varied functions in previously underappreciated diverse tissue sites, based on the ability of eosinophils to release cytokines (often preformed) that mediate a broad range of activities into the local environment. In this Review, we consider evolving insights into the tissue distribution of eosinophils and their functional immunobiology, which enable eosinophils to secrete in a selective manner cytokines and other mediators that have diverse, 'non-effector' functions in health and disease.

Pathological and therapeutic roles of innate lymphoid cells in diverse diseases

Innate lymphoid cells (ILCs) are a recently defined type of innate-immunity cells that belong to the lymphoid lineage and have lymphoid morphology but do not express an antigen-specific B cell or T-cell receptor. ILCs regulate immune functions prior to the formation of adaptive immunity and exert effector functions through a cytokine release. ILCs have been classified into three groups according to the transcription factors that regulate their development and function and the effector cytokines they produce. Of note, ILCs resemble T helper (Th) cells, such as Th1, Th2, and Th17 cells, and show a similar dependence on transcription factors and distinct cytokine production. Despite their short history in immunology, ILCs have received much attention, and numerous studies have revealed biological functions of ILCs including host defense against pathogens, inflammation, tissue repair, and metabolic homeostasis. Here, we describe recent findings about the roles of ILCs in the pathogenesis of various diseases and potential therapeutic targets.