Intraepithelial neutrophils in pediatric severe asthma are associated with better lung function

A novel syndrome of silent rhinovirus-associated bronchoalveolitis in children with recurrent wheeze

BACKGROUND

Rhinovirus (RV) infections trigger wheeze episodes in children. Thus, understanding of the lung inflammatory response to RV in children with wheeze is important.

OBJECTIVES

This study sought to examine the associations of RV on bronchoalveolar lavage (BAL) granulocyte patterns and biomarkers of inflammation with age in children with treatment-refractory, recurrent wheeze (n = 616).

METHODS

Children underwent BAL to examine viral nucleic acid sequences, bacterial cultures, granulocyte counts, and phlebotomy for both general and type-2 inflammatory markers.

RESULTS

Despite the absence of cold symptoms, RV was the most common pathogen detected (30%), and when present, was accompanied by BAL granulocytosis in 75% of children. Compared to children with no BAL pathogens (n = 341), those with RV alone (n = 127) had greater (P < .05) isolated neutrophilia (43% vs 16%), mixed eosinophils and neutrophils (26% vs 11%), and less pauci-granulocytic (27% vs 61%) BAL. Children with RV alone furthermore had biomarkers of active infection with higher total blood neutrophils and serum C-reactive protein, but no differences in blood eosinophils or total IgE. With advancing age, the log odds of BAL RV alone were lower, 0.82 (5th-95th percentile CI: 0.76-0.88; P < .001), but higher, 1.58 (5th-95th percentile CI: 1.01-2.51; P = .04), with high-dose daily corticosteroid treatment.

CONCLUSIONS

Children with severe recurrent wheeze often (22%) have a silent syndrome of lung RV infection with granulocytic bronchoalveolitis and elevated systemic markers of inflammation. The syndrome is less prevalent by school age and is not informed by markers of type-2 inflammation. The investigators speculate that dysregulated mucosal innate antiviral immunity is a responsible mechanism.

Childhood asthma phenotypes and endotypes: a glance into the mosaic

BACKGROUND

Asthma is an inflammatory lung disease that constitutes the most common noncommunicable chronic disease in childhood. Childhood asthma shows large heterogeneity regarding onset of disease, symptoms, severity, prognosis, and response to therapy.

MAIN BODY

Evidence suggests that this variability is due to distinct pathophysiological mechanisms, which has led to an exhaustive research effort to understand and characterize these distinct entities currently designated as "endotypes." Initially, studies focused on identifying specific groups using clinical variables yielding different "clinical phenotypes." In addition, the identification of specific patterns based on inflammatory cell counts and cytokine data has resulted in "inflammatory endotypes." More recently, an increasing number of molecular data from high-throughput technology ("omics" data) have allowed to investigate more complex "molecular endotypes."

CONCLUSION

A better definition and comprehension of childhood asthma heterogeneity is key for improving diagnosis and treatment. This review aims at summarizing the current knowledge on this topic and discusses some limitations in their application as well as recommendations for future studies.

Severe pediatric asthma endotypes: current limits and future perspectives

INTRODUCTION

Although rare, pediatric severe therapy-resistant asthma (STRA) is a highly heterogeneous, resource-demanding disease that differs significantly from severe adult asthma and whose pathogenesis is still poorly understood.

AREAS COVERED

This review summarizes the latest 10 years of English-written studies defining pediatric STRA endotypes using lung-specific techniques such as bronchoalveolar lavage and endobronchial biopsy. Results of the studies and limits on the field are discussed, together with some future perspectives.

EXPERT OPINION

Over the years, it has become increasingly clear that 'one size does not fit all" in asthma. However, "Does an extremely tailored size fit more than one?'. Only using multicentric, longitudinal pediatric studies, will we be able to answer. Three issues could be particularly critical for future research. First, to provide, if existing, a distinction between prepuberal STRA and puberal STRA endotypes to understand the transition from pediatric to adult STRA and to design effective, tailored therapies in adolescents, usually suffering from poorer asthma control. Second, design early treatments for pediatric airway remodeling to preserve lifelong good lung function. Finally, to better characterize inflammation before and during biological therapies, to provide clues on whether to stop or change treatments.

T2-Low Asthma: A Discussed but Still Orphan Disease

Asthma affects 10% of the worldwide population; about 5% of cases are severe with the need for target therapies such as biologics. All the biologics approved for asthma hit the T2 pathway of inflammation. T2-high asthma is classified as allergic and non-allergic, whereas T2-low asthma can be further defined as paucigranulocytic asthma, Type 1 and Type-17 inflammation and the neutrophilic form that accounts for 20-30% of all patients with asthma. Neutrophilic asthma's prevalence is even higher in patients with severe or refractory asthma. We searched Medline and PubMed archives from the past ten years for articles with the subsequent titles: "neutrophilic asthma", "non-type 2 asthma" and "paucigranulocytic asthma". We identified 177 articles; 49 were considered relevant by the title and 33 by the reading of the abstract. Most of these articles are reviews (n = 19); only 6 are clinical trials. No study identified an effective treatment. We used the literature reported by these articles to search for further biologic treatments that target pathways different from T2. We identified 177 articles, 93 of which were considered relevant for the review and included in the present article. In conclusion, T2-low asthma remains poorly investigated in terms of biomarkers, especially as a therapeutic orphan disease.

Pediatric obesity and severe asthma: Targeting pathways driving inflammation

Asthma affects more than 300 million people of all ages worldwide, including about 10-15% of school-aged children, and its prevalence is increasing. Severe asthma (SA) is a particular and rare phenotype requiring treatment with high-dose inhaled corticosteroids plus a second controller and/or systemic glucocorticoid courses to achieve symptom control or remaining "uncontrolled" despite this therapy. In SA, other diagnoses have been excluded, and potential exacerbating factors have been addressed. Notably, obese asthmatics are at higher risk of developing SA. Obesity is both a major risk factor and a disease modifier of asthma in children and adults: two main "obese asthma" phenotypes have been described in childhood with high or low levels of Type 2 inflammation biomarkers, respectively, the former characterized by early onset and eosinophilic inflammation and the latter by neutrophilic inflammation and late-onset. Nevertheless, the interplay between obesity and asthma is far more complex and includes obese tissue-driven inflammatory pathways, mechanical factors, comorbidities, and poor response to corticosteroids. This review outlines the most recent findings on SA in obese children, particularly focusing on inflammatory pathways, which are becoming of pivotal importance in order to identify selective targets for specific treatments, such as biological agents.

THE LEVEL OF REACTIVE OXYGEN SPECIES AS A MARKER OF ASTHMA SEVERITY IN CHILDREN

OBJECTIVE

The aim of the research was to assess the reactive oxygen species (ROS) levels in granulocytes of patients with asthma.

PATIENTS AND METHODS

Materials and methods: The study involved 35 children aged 5 to 17 years. 26 children with persistent asthma, partially controlled course in the period of exacerbation were divided into groups: 1 group - mild asthma (n = 12), group 2 - moderate asthma (n = 7) group 3 - severe asthma (n = 7) and control group included almost healthy children (n = 9). ROS levels in granulocytes were evaluated using BD FACSDiva™. The spirographic complex was used to assess the function of external respiration.

RESULTS

Results: The level of ROS in granulocytes of patients with severe asthma was significantly reduced compared with children in the control group and patients with mild and moderate asthma (p₁-₃ = 0.0003, p₂-₃ = 0.0017, p c-₃ = 0.0150). The concentration of ROS in granulocytes ≤ 285 a.u. was prognostically significant with high specificity and sensitivity with severe asthma.

CONCLUSION

Conclusions: The concentration of ROS levels in neutrophils in patients with severe asthma probably reflected the suppression of their products, which suggests the depletion of the reserve capacity of neutrophils. Decreased concentrations of reactive oxygen species in children with asthma can be considered as a possible marker of asthma severity.

Age-Related Clinical Characteristics, Inflammatory Features, Phenotypes, and Treatment Response in Asthma

BACKGROUND

Emerging evidence suggests that aging affects asthma outcomes, but the mechanism remains largely unexplored.

OBJECTIVE

To explore age-related clinical characteristics, inflammatory features, phenotypes, and treatment response in asthma.

METHODS

This was a prospective cohort study of asthmatic patients with a 12-month follow-up in a real-world setting. Clinical inflammatory and phenotypic characteristics, future risk for exacerbations, and treatment response were assessed across different age groups (young was defined as age 18 to 39 years; middle-aged, 40 to 64 years; and elderly, 65 years or older).

RESULTS

Compared with young (n = 106) and middle-aged (n = 179) asthmatic patients, elderly patients (n = 55) had worse airway obstruction, more comorbidities including chronic obstructive pulmonary disease and diabetes, less atopy, and lower levels of IgE and FeNO, and were more likely to have late-onset and fixed airflow obstruction asthma and a reduced risk for having type 2 profile asthma. Levels of IFN-gamma, IL-17A, and IL-8 in induced sputum were significantly increased in elderly asthmatic patients (all P < .05). Path analysis indicated that age directly and significantly led to future exacerbations in asthma, partially mediated by an upregulation of airway IFN-gamma. Moreover, elderly patients with asthma had a reduced treatment response (improvement in FEV₁ of 12% or greater, or 200 mL, and a reduction in Borg scores of 1 or greater) (adjusted odds ratio = 0.11; 95% CI, 0.02-0.52; and adjusted odds ratio = 0.12; 95% CI, 0.03-0.49, respectively).

CONCLUSIONS

This study confirms that asthma in the elderly population represents a specific phenotype and indicates that aging can influence asthma in terms of clinical characteristics, inflammatory features, exacerbations, and treatment response.

Sterols in asthma

While sterols regulate immune processes key to the pathogenesis of asthma, inhibition of sterols with statin drugs has shown conflicting results in human asthma. Here, a novel understanding of the impact of sterols on type 17 immune responses and asthma lead us to hypothesize that sterols and statins may be relevant to severe asthma endotypes with neutrophil infiltration.

EphA2 recognizes Dermatophagoidespteronyssinus to mediate airway inflammation in asthma

Most of the asthma with low Th2 is severe steroid-resistant asthma, the exact pathogenesis of which has not yet been fully elucidated. We found that IL-6 and IL-8 were highly expressed in the sputum supernatant of severe asthma and ephrin type-A receptor 2 (EphA2) was highly expressed on bronchial epithelial cells. So, is there a connection between these two phenomena? To clarify this issue, we stimulated bronchial epithelial cells 16HBE with Dermatophagoides pteronyssinus and its compontents LPS, respectively, and detected the activation of EphA2, activation of downstream pathways and secretion of inflammatory cytokines. A mouse asthma model was established, and the therapeutic effects of inhibiting or blocking EphA2 on mouse asthma were investigated. The results showed that D. pteronyssinus and its component LPS phosphorylated EphA2 on 16HBE, activated downstream signaling pathways STAT3 and p38 MAPK, and promoted the secretion of IL-6 and IL-8. After knockout of EphA2 on 16HBE, the activation of inflammatory pathways was attenuated and the secretion of IL-6 and IL-8 was significantly reduced. Inhibition or blockade of EphA2 on mouse airways resulted in a significant reduction in airway hyperresponsiveness and airway inflammation, and a significant decrease in the expression levels of IL-6, IL-17F, IL-1α, IL-1β and TNF in bronchoalveolar lavage fluid and lung tissue. Our study uncovers a novel role for EphA2 expressed on airway epithelial cells in the pathogenesis of asthma; EphA2 recognizes D. pteronyssinus or its component LPS and promotes the secretion of IL-6 and IL-8 by airway epithelial cell, thereby mediating airway inflammation. Thus, it is possible to provide a new molecular therapy for severe asthma.

Difficult-to-Treat Asthma Management in School-Age Children

The World Health Organization divides severe asthma into three categories: untreated severe asthma; difficult-to-treat severe asthma; and severe, therapy-resistant asthma. The apparent frequency of severe asthma in the general population of asthmatic children is probably around 5%. Upon referral of these children, it is important to evaluate the diagnosis of asthma carefully before modifying management and applying a long-term monitoring plan. Identification of pathophysiologic phenotypes using objective biomarkers is essential in our routine assessments of severe asthma. Although conventional pharmacologic approaches should be attempted first, there is growing recognition that children with difficult-to-treat asthma may have unique clinical phenotypes that may necessitate alternative treatment approaches including asthma biologics. These new medications, especially those with effects on multiple pathologic features of asthma, raise the hope that new treatment strategies could induce remission. Besides introducing new medications, the opportunity for closer monitoring is feasible with advances in digital health. Therefore, we have the opportunity to improve response to medications, individualize treatment, and monitor response along with potential steps to prevent severe asthma.

Interleukin-5 receptor alpha (CD125) expression on human blood and lung neutrophils

BACKGROUND

Our previous studies revealed the presence of interleukin-5 (IL-5) receptor alpha chain (IL-5Rα, CD125) on neutrophils in a murine model of influenza and in the lung fluid of children with severe asthma.

OBJECTIVE

To further evaluate the functional characteristics and effects of clinical factors and inflammatory variables on neutrophil surface IL-5Rα abundance in lung fluid and blood.

METHODS

IL-5Rα expression was quantified by flow cytometry performed on purified neutrophils from blood and bronchoalveolar lavage fluid samples obtained from healthy controls and individuals with asthma. Expression was further confirmed by immunohistochemistry. Functional signaling through the IL-5Rα was evaluated by measurement of IL-5-inducible modulation of neutrophil surface CD62L and IL-5Rα expression.

RESULTS

IL-5Rα was consistently present but at a variable magnitude on blood and lung neutrophils. Expression on lung neutrophils was significantly higher than that on blood cells (p"?>P < .001) where their expression was higher in the presence of airway pathogens, especially with respiratory viruses. Increased receptor expression occurred in response to the translocation of preformed receptors from intracellular stores. Receptors were functional as revealed by IL-5-mediated down-regulation of CD62L and the feed-forward up-regulation of reception expression.

CONCLUSION

In addition to the expression on eosinophils and basophils, the IL-5Rα is consistently and abundantly expressed on the surface of blood and especially air space neutrophils. These observations support the concept that some of the efficacy of IL-5/IL-5R-targeting biologics observed in asthma may reflect their ability to target neutrophilic air space inflammation.

How to Choose the Correct Drug in Severe Pediatric Asthma

When a child with severe asthma (asthma defined clinically for the purposes of this review as wheeze, breathlessness, and chest tightness sometimes with cough) does not respond to treatment, it is important to be sure that an alternative or additional diagnosis is not being missed. In school age children, the next step is a detailed protocolized assessment to determine the nature of the problem, whether within the airway or related to co-morbidities or social/environmental factors, in order to personalize the treatment. For example, those with refractory difficult asthma due to persistent non-adherence may benefit from using budesonide and formoterol combined in a single inhaler [single maintenance and reliever treatment (SMART)] as both a reliever and preventer. For those with steroid-resistant Type 2 airway inflammation, the use of biologicals such as omalizumab and mepolizumab should be considered, but for mepolizumab at least, there is a paucity of pediatric data. Protocols are less well developed in preschool asthma, where steroid insensitive disease is much more common, but the use of two simple measurements, aeroallergen sensitization, and peripheral blood eosinophil count, allows the targeted use of inhaled corticosteroids (ICSs). There is also increasing evidence that chronic airway infection may be important in preschool wheeze, increasing the possibility that targeted antibiotics may be beneficial. Asthma in the first year of life is not driven by Type 2 inflammation, so beyond avoiding prescribing ICSs, no evidence based recommendations can be made. In the future, we urgently need to develop objective biomarkers, especially of risk, so that treatment can be targeted effectively; we need to address the scandal of the lack of data in children compared with adults, precluding making evidence-based therapeutic decisions and move from guiding treatment by phenotypes, which will change as the environment changes, to endotype based therapy.

Bronchial eosinophils, neutrophils, and CD8 + T cells influence asthma control and lung function in schoolchildren and adolescents with severe treatment-resistant asthma

BACKGROUND

Studies in adult severe treatment-resistant asthma (STRA) have demonstrated heterogeneous pathophysiology. Studies in the pediatric age group are still scarce, and few include bronchial tissue analysis.

OBJECTIVE

We investigated 6-18-year-old patients diagnosed with STRA in Sao Paulo, Brazil, by characterizing the different lung compartments and their correlations with asthma control and lung function.

METHODS

Inflammatory profiles of 13 patients with a confirmed diagnosis of STRA were analyzed using blood, induced sputum, bronchoalveolar lavage, viral and bacterial screens and endobronchial biopsy. Inflammatory cells, cytokines, and basement membrane thickening were tested for correlations with the asthma control test (ACT) and spirometry and plethysmography parameters.

RESULTS

Endobronchial biopsy specimens from 11 patients were viable for analysis. All biopsies showed eosinophilic infiltration. Submucosal (SM) eosinophils and neutrophils were correlated with worse lung function (pre-BD FEV1), and SM neutrophils were correlated with fixed obstruction (post-BD FEV1). Intraepithelial (IE) neutrophils were positively correlated with lung function (pre-BD sGaw). CD8 + T cells had the highest density in the IE and SM layers and were positively correlated with ACT and negatively correlated with the cytokines IL1β, IL2, IL5, IL7, IL10, IL12, IL17, GCSF, MCP-1, INF-δ, and TNFα in sputum supernatant. The ASM chymase + mast cell density correlated positively with quality-of-life score (pAQLQ) and ACT.

CONCLUSION

Eosinophils and SM neutrophils correlated with worse lung function, while IE neutrophils correlated with better lung function. Most importantly, CD8 + T cells were abundant in bronchial biopsies of STRA patients and showed protective associations, as did chymase + mast cells.

Benefits and risks of bronchoalveolar lavage in severe asthma in children

Background

Although bronchoscopy can be part of the exploration of severe asthma in children, the benefit of bronchoalveolar lavage (BAL) is unknown. The present study aimed to decipher whether systematic BAL during a flexible bronchoscopy procedure could better specify the characteristics of severe asthma and improve asthma management.

Material and methods

The study took place in two departments of a university hospital in Paris. Children who underwent flexible bronchoscopy for the exploration of severe asthma between April 2017 and September 2019 were retrospectively included.

Results

In total, 203 children were included, among whom 107 had a BAL. BAL cell count was normal in most cases, with an increasing number of eosinophils with age, independently from the atopic status of the patients. Compared with bronchial aspiration only, BAL increased the rate of identified bacterial infection by 1.5. Nonatopic patients had more bacterial infections (p<0.001). BAL induced a therapeutic modification only for azithromycin and omalizumab prescriptions. The practice of a BAL decreased bronchoscopy tolerance (p=0.037), especially in the presence of tracheobronchial malacia (p<0.01) and when performed in a symptomatic patient (p=0.019).

Discussion and conclusion

Although BAL may provide interesting information in characterising severe asthma, in most cases its impact on the patient's management remains limited. Moreover, BAL can be poorly tolerated and should be avoided in the case of tracheobronchial malacia or current asthma symptoms.

Bronchoalveolar lavage can help characterise severe asthma in children. However, it can be poorly tolerated and, in most cases, its impact on the patient's management remains limited.https://bit.ly/39XOlMt

Our evolving view of neutrophils in defining the pathology of chronic lung disease

Neutrophils are critical components of the body's immune response to infection, being loaded with a potent arsenal of toxic mediators and displaying immense destructive capacity. Given the potential of neutrophils to impart extensive tissue damage, it is perhaps not surprising that when augmented these cells are also implicated in the pathology of inflammatory diseases. Prominent neutrophilic inflammation is a hallmark feature of patients with chronic lung diseases such as chronic obstructive pulmonary disease, severe asthma, bronchiectasis and cystic fibrosis, with their numbers frequently associating with worse prognosis. Accordingly, it is anticipated that neutrophils are central to the pathology of these diseases and represent an attractive therapeutic target. However, in many instances, evidence directly linking neutrophils to the pathology of disease has remained somewhat circumstantial and strategies that have looked to reduce neutrophilic inflammation in the clinic have proved largely disappointing. We have classically viewed neutrophils as somewhat crude, terminally differentiated, insular and homogeneous protagonists of pathology. However, it is now clear that this does not do the neutrophil justice, and we now recognize that these cells exhibit heterogeneity, a pronounced awareness of the localized environment and a remarkable capacity to interact with and modulate the behaviour of a multitude of cells, even exhibiting anti-inflammatory, pro-resolving and pro-repair functions. In this review, we discuss evidence for the role of neutrophils in chronic lung disease and how our evolving view of these cells may impact upon our perceived assessment of their contribution to disease pathology and efforts to target them therapeutically.

Severe acute asthma at the pediatric intensive care unit: can we link the clinical phenotypes to immunological endotypes?

INTRODUCTION

The clinical phenotype of severe acute asthma at the pediatric intensive care unit (PICU) is highly heterogeneous. However, current treatment is still based on a 'one-size-fits-all approach'.

AREAS COVERED

We aim to give a comprehensive description of the clinical characteristics of pediatric patients with severe acute asthma admitted to the PICU and available immunological biomarkers, providing the first steps toward precision medicine for this patient population. A literature search was performed using PubMed for relevant studies on severe acute (pediatric) asthma.

EXPERT OPINION

Omics technologies should be used to investigate the relationship between cellular molecules and pathways, and their clinical phenotypes. Inflammatory phenotypes might guide bedside decisions regarding the use of corticosteroids, neutrophil modifiers and/or type of beta-agonist. A next step toward precision medicine should be inclusion of these patients in clinical trials on biologics.

Pediatric problematic severe asthma: Recent advances in management

Problematic severe asthma remains a significant challenge to manage, accounting for the majority of healthcare utilization among children with asthma. The heterogeneity is recognized and the clinical phenotypes of "difficult-to-treat" asthma (DA) and "severe therapy-resistant asthma" (STRA) help to guide management. Recent evidence supports molecular distinctions between these phenotypes and shows poor correlations between peripheral and airway markers of inflammation, especially in STRA. Airway neutrophils in the context of childhood severe asthma have been explored, but their role in disease causation, protection, or as bystanders remain unknown, and thus, treatment implications are unclear. Several novel management strategies, including once-daily maintenance therapy, single-device maintenance and reliever therapy, and novel biological treatments are being increasingly used for DA and STRA. However, pediatric data for efficacy of novel treatments is scarce, and when available, is restricted to adolescents. The aim of this review is to highlight recent advances in objective biomarkers that aid stratification and management of childhood severe asthma and to highlight gaps in pediatric evidence. Specifically, the urgent need for efficacy studies to improve the management of problematic severe asthma in children younger than 12 years.

Challenging the paradigm: moving from umbrella labels to treatable traits in airway disease

Airway diseases were initially described by nonspecific patterns of symptoms, for example "dry and wheezy" and "wet and crackly". The model airway disease is cystic fibrosis, which has progressed from nonspecific reactive treatments such as antibiotics for airway infection to molecular sub-endotype, proactive therapies with an unequivocal evidence base, early diagnosis, and biomarkers of treatment efficacy. Unfortunately, other airway diseases lag behind, not least because nonspecific umbrella labels such as "asthma" are considered to be diagnoses not mere descriptions. Pending the delineation of molecular sub-endotypes in other airway disease the concept of treatable traits, and consideration of airway disease in a wider context is preferable. A treatable trait is a characteristic amenable to therapy, with measurable benefits of treatment. This approach determines what pathology is actually present and treatable, rather than using umbrella labels. We determine if airway inflammation is present, and whether there is airway eosinophilia which will likely respond to inhaled corticosteroids; whether there is variable airflow obstruction due to bronchoconstriction which will respond to β2-agonists; and whether there is unsuspected underlying airway infection which should be treated with antibiotics unless there is an underlying endotype which can be addressed, as for example an immunodeficiency. The context of airway disease should also be extrapulmonary comorbidities, social and environmental factors, and a developmental perspective, particularly this last aspect if preventive strategies are being contemplated. This approach allows targeted treatment for maximal patient benefit, as well as preventing the discarding of therapies which are useful for appropriate subgroups of patients. Failure to appreciate this almost led to the discarding of valuable treatments such as prednisolone.

EDUCATIONAL AIMS

To use cystic fibrosis as a paradigm to show the benefits of the journey from nonspecific umbrella terms to specific endotypes and sub-endotypes, as a road map for other airway diseases to follow.Demonstrate that nonspecific labels to describe airway disease can and should be abandoned in favour of treatable traits to ensure diagnostic and therapeutic precision.Begin to learn to see airway disease in the context of extrapulmonary comorbidities, and social and environmental factors, as well as with a developmental perspective.

Respiratory Viral and Bacterial Factors That Influence Early Childhood Asthma

Asthma is a chronic respiratory condition characterised by episodes of shortness of breath due to reduced airway flow. The disease is triggered by a hyperreactive immune response to innocuous allergens, leading to hyper inflammation, mucus production, changes in structural cells lining the airways, and airway hyperresponsiveness. Asthma, although present in adults, is considered as a childhood condition, with a total of about 6.2 million children aged 18 and below affected globally. There has been progress in understanding asthma heterogeneity in adults, which has led to better patient stratification and characterisation of multiple asthma endotypes with distinct, but overlapping inflammatory features. The asthma inflammatory profile in children is not well-defined and heterogeneity of the disease is less described. Although many factors such as genetics, food allergies, antibiotic usage, type of birth, and cigarette smoke exposure can influence asthma development particularly in children, respiratory infections are thought to be the major contributing factor in poor lung function and onset of the disease. In this review, we focus on viral and bacterial respiratory infections in the first 10 years of life that could influence development of asthma in children. We also review literature on inflammatory immune heterogeneity in asthmatic children and how this overlaps with early lung development, poor lung function and respiratory infections. Finally, we review animal studies that model early development of asthma and how these studies could inform future therapies and better understanding of this complex disease.

Defining pediatric asthma: phenotypes to endotypes and beyond

Asthma is the most common chronic pediatric lung disease that has traditionally been defined as a syndrome of airway inflammation characterized by clinical symptoms of cough and wheeze. Highlighting the complex and heterogeneous nature of asthma, this review summarizes recent advances in asthma classification that are based on pathobiology, and thereby directly addresses limitations of existent definitions of asthma. By reviewing and contrasting clinical and mechanistic features of adult and childhood asthma, the review summarizes key biomarkers that distinguish childhood asthma subtypes. While atopy and its severity are important features of childhood asthma, there is evidence to support the existence of a childhood asthma endotype distinct from the atopic endotype. Although biomarkers of non-atopic asthma are an area of future research, we summarize a clinical approach that includes existing measures of airway-specific and systemic measures of atopy, co-existing morbidities, and disease severity and control, in the definition of childhood asthma, to empower health care providers to better characterize asthma disease burden in children. Identification of biomarkers of non-atopic asthma and the contribution of genetics and epigenetics to pediatric asthma burden remains a research need, which can potentially allow delivery of precision medicine to pediatric asthma. IMPACT: This review highlights asthma as a complex and heterogeneous disease and discusses recent advances in the understanding of the pathobiology of asthma to demonstrate the need for a more nuanced definitions of asthma. We review current knowledge of asthma phenotypes and endotypes and put forth an approach to endotyping asthma that may be useful for defining asthma for clinical care as well as for future research studies in the realm of personalized medicine for asthma.

T2-"Low" Asthma: Overview and Management Strategies

Although the term "asthma" has been applied to all patients with airway lability and variable chest symptoms for centuries, phenotypes of asthma with distinct clinical and molecular features that may warrant different treatment approaches are well recognized. Patients with type 2 (T2)-"high" asthma are characterized by upregulation of T2 immune pathways (ie, IL-4 and IL-13 gene sets) and eosinophilic airway inflammation, whereas these features are absent in patients with T2-"low" asthma and may contribute to poor responsiveness to corticosteroid treatment. This review details definitions and clinical features of T2-"low" asthma, potential mechanisms and metabolic aspects, pediatric considerations, and potential treatment approaches. Priority research questions for T2-"low" asthma are also discussed.

Neutrophils in asthma: the good, the bad and the bacteria

Airway inflammation plays a key role in asthma pathogenesis but is heterogeneous in nature. There has been significant scientific discovery with regard to type 2-driven, eosinophil-dominated asthma, with effective therapies ranging from inhaled corticosteroids to novel biologics. However, studies suggest that approximately 1 in 5 adults with asthma have an increased proportion of neutrophils in their airways. These patients tend to be older, have potentially pathogenic airway bacteria and do not respond well to classical therapies. Currently, there are no specific therapeutic options for these patients, such as neutrophil-targeting biologics.Neutrophils comprise 70% of the total circulatory white cells and play a critical defence role during inflammatory and infective challenges. This makes them a problematic target for therapeutics. Furthermore, neutrophil functions change with age, with reduced microbial killing, increased reactive oxygen species release and reduced production of extracellular traps with advancing age. Therefore, different therapeutic strategies may be required for different age groups of patients.The pathogenesis of neutrophil-dominated airway inflammation in adults with asthma may reflect a counterproductive response to the defective neutrophil microbial killing seen with age, resulting in bystander damage to host airway cells and subsequent mucus hypersecretion and airway remodelling. However, in children with asthma, neutrophils are less associated with adverse features of disease, and it is possible that in children, neutrophils are less pathogenic.In this review, we explore the mechanisms of neutrophil recruitment, changes in cellular function across the life course and the implications this may have for asthma management now and in the future. We also describe the prevalence of neutrophilic asthma globally, with a focus on First Nations people of Australia, New Zealand and North America.

Asthma phenotypes and endotypes in childhood

Asthma is a very heterogeneous disease and since early childhood many classifications have been proposed according to phenotype and endotype. The phenotype includes the clinical features of asthma such as age of onset, triggers, comorbidities, response to treatment and evolution over time. The endotype is more difficult to define, includes the underlying immunopathological mechanisms of the disease and requires reliable biomarkers. A deep knowledge of phenotype and endotype of the patient may guide a tailored therapeutic approach. In this review the main phenotypes and endotypes of asthma acknowledged in children will be discussed.

Role of IL-22 in persistent allergic airway diseases caused by house dust mite: a pilot study

BACKGROUND

Persistent allergic airway diseases cause a great burden worldwide. Their pathogenesis is not clear enough. There is evidence that one of the recently described cytokine interleukin (IL) 22 may be involved in the pathogenesis of these diseases. Scientists argue if this cytokine acts as proinflammatory or anti-inflammatory agent. The aim of this study was to investigate IL-22 level in patients with persistent allergic airway diseases caused by house dust mite (HDM) in comparison with healthy individuals and to evaluate its relationship with IL-13 and IL-10 level, symptoms score and quality of life.

METHODS

Patients with persistent allergic rhinitis caused by HDM and having symptoms for at least 2 years with or without allergic asthma were involved into the study. Measurements of IL-22, IL-13 and IL-10 and in serum and nasal lavage was performed by ELISA. Questionnaires assessing symptoms severity and quality of life were used.

RESULTS

A tendency was observed that IL-22 in serum and nasal lavage was higher in patients with allergic airway diseases compared to control group (14.86 pg/ml vs. 7.04 pg/ml and 2.67 pg/ml vs. 1.28 pg/ml, respectively). Positive statistically significant correlation was estimated between serum IL-22 and serum IL-10 (rs = 0.57, p < 0.01) and IL-13 (rs = 0.44, p < 0.05) level. Moreover, positive significant correlation was found between IL-22 in nasal lavage and IL-10 in nasal lavage (rs = 0.37, p < 0.05). There was a negative statistically significant correlation between serum IL-22 and Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) (rs = - 0.42, p < 0.05).

CONCLUSION

Our study showed a possible anti-inflammatory effect of IL-22 in patients with persistent allergic airway diseases caused by HDM.

Clinical and histopathologic predictors of therapeutic response to bronchial thermoplasty in severe refractory asthma

BACKGROUND

Phenotypes and endotypes predicting optimal response to bronchial thermoplasty (BT) in patients with severe asthma remain elusive.

OBJECTIVE

Our aim was to compare the clinical characteristics and hallmarks of airway inflammation and remodeling before and after BT in responder and partial responder patients with severe asthma refractory to oral steroids and to omalizumab.

METHODS

In all, 23 patients with severe refractory asthma were divided into BT responders (n = 15) and BT partial responders (n = 8), according to the decrease in asthma exacerbations at 12 months after BT. Clinical parameters were compared at baseline and 12 months after BT, and hallmarks of airway inflammation and remodeling were analyzed by immunohistochemistry in bronchial biopsy specimens before and 3 months after BT.

RESULTS

At baseline, the BT responders were around 8 years younger than the BT partial responders (P = .02) and they had a greater incidence of atopy, higher numbers of blood eosinophils (both P = .03) and IgE levels, higher epithelial IFN-α expression, and higher numbers of mucosal eosinophils and IL-33-positive cells (P ≤ .05). A reduction in blood eosinophil count, serum IgE level, type 2 airway inflammation, and numbers of mucosal IL-33-positive cells and mast cells associated with augmented epithelial MUC5AC and IFN-α/β immunostaining was noted after BT in responders, whereas the numbers of mucosal IL-33-positive cells were augmented in BT partial responders. Most of these changes were correlated with clinical parameters. Subepithelial membrane thickening and airway smooth muscle area were similar in the 2 patient groups at baseline and after BT.

CONCLUSION

By reducing allergic type 2 inflammation and increasing epithelial MUC5AC and anti-viral IFN-α/β expression, BT may enhance host immune responses and thus attenuate exacerbations and symptoms in BT responders. Instead, targeting IL-33 may provide a clinical benefit in BT partial responders.

EAACI Biologicals Guidelines-Recommendations for severe asthma

Severe asthma imposes a significant burden on patients, families and healthcare systems. Management is difficult, due to disease heterogeneity, co-morbidities, complexity in care pathways and differences between national or regional healthcare systems. Better understanding of the mechanisms has enabled a stratified approach to the management of severe asthma, supporting the use of targeted treatments with biologicals. However, there are still many issues that require further clarification. These include selection of a certain biological (as they all target overlapping disease phenotypes), the definition of response, strategies to enhance the responder rate, the duration of treatment and its regimen (in the clinic or home-based) and its cost-effectiveness. The EAACI Guidelines on the use of biologicals in severe asthma follow the GRADE approach in formulating recommendations for each biological and each outcome. In addition, a management algorithm for the use of biologicals in the clinic is proposed, together with future approaches and research priorities.

Impaired airway epithelial cell wound-healing capacity is associated with airway remodelling following RSV infection in severe preschool wheeze

BACKGROUND

Respiratory syncytial virus (RSV) causes exacerbations of asthma and preschool wheeze (PSW). However, the anti-viral and repair responses of the bronchial epithelium in children with severe therapy-resistant asthma (STRA) and PSW are poorly understood.

METHODS

Children with STRA (age 12 [6-16] years), PSW (age 2 [1-5] years) and non-asthmatic controls (age 7 [2-14] years) underwent bronchoscopy with endobronchial brushings and biopsies. Anti-viral, wound injury responses were quantified in biopsies and primary bronchial epithelial cells (PBECs) in response to RSV, poly(I:C), house dust mite (HDM) or IL-33 using RT-qPCR, Luminex and live cell imaging. Collagen deposition and tissue expression of epithelial growth factor receptor (EGFR), IL-33 and receptor ST2 were investigated in bronchial biopsies.

RESULTS

PBECs from STRA and PSW had increased TLR3 gene expression and increased secretion of anti-viral and pro-inflammatory cytokines (IFN-γ, IL-6 and IL-13) in response to RSV compared to controls. Exposure of PBECs to concomitant TLR3 agonist poly(I:C) and HDM resulted in a significant reduction in epithelial cell proliferation in PSW compared to controls. Wound-healing was also impaired in PSW compared to controls at baseline and following IL-33 stimulation. In addition, tissue EGFR expression was significantly reduced in PSW and correlated with collagen deposition in endobronchial biopsies.

CONCLUSIONS

Despite increased anti-viral responses, preschool children with severe wheeze had impaired airway epithelial proliferative responses following damage. This might be connected to the low expression of EGFR in PSW which may affect epithelial function and contribute to asthma pathogenesis.

Advances in understanding and reducing the burden of severe asthma in children

Severe asthma in children is rare, accounting for only a small proportion of childhood asthma. After addressing modifiable factors such as adherence to treatment, comorbidities, and adverse exposures, children whose disease is not well controlled on high doses of medication form a heterogeneous group of severe asthma phenotypes. Over the past decade, considerable advances have been made in understanding the pathophysiology of severe therapy-resistant asthma in children. However, asthma attacks and hospital admissions are frequent and mortality is still unacceptably high. Strategies to modify the natural history of asthma, prevent severe exacerbations, and prevent lung function decline are needed. Mechanistic studies have led to the development of several biologics targeting type 2 inflammation. This growing pipeline has the potential to reduce the burden of severe asthma; however, detailed assessment and characterisation of each child with seemingly severe asthma is necessary so that the most effective and appropriate management strategy can be implemented. Risk stratification, remote monitoring, and the integration of multiple data sources could help to tailor management for the individual child with severe asthma.

Are We Meeting the Promise of Endotypes and Precision Medicine in Asthma?

While the term asthma has long been known to describe heterogeneous groupings of patients, only recently have data evolved which enable a molecular understanding of the clinical differences. The evolution of transcriptomics (and other 'omics platforms) and improved statistical analyses in combination with large clinical cohorts opened the door for molecular characterization of pathobiologic processes associated with a range of asthma patients. When linked with data from animal models and clinical trials of targeted biologic therapies, emerging distinctions arose between patients with and without elevations in type 2 immune and inflammatory pathways, leading to the confirmation of a broad categorization of type 2-Hi asthma. Differences in the ratios, sources, and location of type 2 cytokines and their relation to additional immune pathway activation appear to distinguish several different (sub)molecular phenotypes, and perhaps endotypes of type 2-Hi asthma, which respond differently to broad and targeted anti-inflammatory therapies. Asthma in the absence of type 2 inflammation is much less well defined, without clear biomarkers, but is generally linked with poor responses to corticosteroids. Integration of "big data" from large cohorts, over time, using machine learning approaches, combined with validation and iterative learning in animal (and human) model systems is needed to identify the biomarkers and tightly defined molecular phenotypes/endotypes required to fulfill the promise of precision medicine.

Bronchoalveolar lavage cytokine patterns in children with severe neutrophilic and paucigranulocytic asthma

BACKGROUND

Asthma is a complex heterogeneous disease occurring in adults and children that is characterized by distinct inflammatory patterns. While numerous studies have been performed in adults, little is known regarding the heterogeneity of severe asthma in children, particularly inflammatory signatures involving the air spaces.

OBJECTIVE

We sought to determine the relationship of bronchoalveolar lavage (BAL) cytokine/chemokine expression patterns in children with severe therapy-resistant asthma stratified according to neutrophilic versus nonneutrophilic BAL inflammatory cell patterns.

METHODS

Children with severe asthma with inadequate symptom control despite therapy underwent diagnostic bronchoscopy and BAL. Inflammatory cytokine/chemokine concentrations were determined using a multiplex protein bead assay.

RESULTS

Analysis of BAL constituents with an unbiased clustering approach revealed distinct cytokine/chemokine patterns, and these aligned with pathways associated with type 2 innate lymphoid cells, monocytes, neutrophil trafficking, and T effector cells. All cytokines examined (n = 27) with 1 exception (vascular endothelial growth factor) were overexpressed with BAL neutrophilia compared with nonneutrophilic asthma, and this was confirmed in a cross-validation analysis. Cytokines specifically responsible for T_h17 (IL-17, IL-6, G-CSF) and T_h1 differentiation and expression (IL-12, TNF-α, IFN-γ) were enhanced in the neutrophilic cohorts. Neutrophilic groups were also characterized by higher prevalence of bacterial and viral pathogens; however, cytokine expression patterns manifested independently of pathogen expression.

CONCLUSIONS

The results demonstrate that children with refractory asthma and neutrophilic inflammation had a BAL cytokine pattern consistent with a mixed T_h17/T_h1/T_h2 response. In contrast, nonneutrophilic asthma presented independently of cytokine overexpression.

The role of interleukin-17 in asthma: a protective response?

While there now exist effective treatments for type 2 high, eosinophilic asthma, there are no specific therapies for 40–50% of people with asthma with other phenotypes, which result from poorly understood underlying pathological mechanisms. One such pathology is neutrophilic inflammation, which has been associated with interleukin (IL)-17 family cytokines. Human genetic studies identified IL-17 polymorphisms associated with asthma; in murine models of allergic airways disease, IL-17A contributes to airway hyperresponsiveness, and in humans, elevated airway IL-17A levels are repeatedly observed in severe asthma. However, the directionality of this association is unknown, and the assumption that IL-17 cytokines drive disease pathology remains speculative. Here, we explore the evidence underlying the relationship between IL-17 and asthma, we review lessons learned from investigating IL-17 in other inflammatory diseases, and discuss the possibility that IL-17 may even be protective in asthma rather than pathogenic. We also critically examine the newly proposed paradigm of a reciprocal relationship between type 2 and type 17 airways inflammation. In summary, we suggest an association between IL-17 and asthma, but research is needed examining the diverse functions of these cytokines, their longitudinal stability, their response to clinical interventions, and for mechanistic studies determining whether they are protective or pathogenic.

IL-17 cytokines have been implicated in neutrophilic asthma by genetic, murine and human data. Here, previous studies are critiqued and the assumption their dominant role is pathogenic rather than protective of airway epithelial barrier integrity is challenged.http://bit.ly/3axB4Zs

Measuring inflammation in paediatric severe asthma: biomarkers in clinical practice

Severe asthma in children is a highly heterogeneous disorder, encompassing different clinical characteristics (phenotypes) and immunopathological pathways (endotypes). Research is focusing on the identification of noninvasive biomarkers able to predict treatment response and assist in designing personalised therapies for severe asthma. Blood and sputum eosinophils, serum IgE and exhaled nitric oxide fraction mostly reflect type 2 airway inflammation in children. However, in the absence of available point-of-care biomarkers, the diagnosis of non-type 2 asthma is still reached by exclusion. In this review, we present the most recent evidence on biomarkers for severe asthma and discuss their implementation in clinical practice. We address the methods for guiding treatment decisions and patient identification, focusing on the paediatric age group.

Noninvasive biomarkers should be integrated with clinical findings to assist in diagnosing and guiding personalised therapies for severe asthma in childrenhttp://bit.ly/2JPvKFV

Severe asthma in children: therapeutic considerations

PURPOSE OF REVIEW

Children with poor asthma control despite maximal maintenance therapy have problematic severe asthma (PSA). A step-wise approach including objective adherence monitoring and a detailed multidisciplinary team assessment to identify modifiable factors contributing to poor control is needed prior to considering therapy escalation. Pathophysiological phenotyping in those with true severe therapy-resistant asthma (STRA) and the current array of add-on therapies will be discussed.

RECENT FINDINGS

Adherence monitoring using electronic devices has shown that only 20-30% of children with PSA have STRA and need additional therapies. Omalizumab and mepolizumab are licensed for children with STRA aged 6 years and older. Although robust safety and efficacy data, with reduced exacerbations, are available for omalizumab, biomarkers predicting response to treatment are lacking. Paediatric safety data are available for mepolizumab, but efficacy data are unknown for those aged 6-11 years and minimal for those 12 years and older. A sub-group of children with STRA have neutrophilia, but the clinical significance and contribution to disease severity remains uncertain.

SUMMARY

Most children with PSA have steroid sensitive disease which improves with adherence to maintenance inhaled corticosteroids. Add-on therapies are only needed for the minority with STRA. Paediatric efficacy data of novel biologics and biomarkers that identify the optimal add-on for each child are lacking. If we are to progress toward individualized therapy for STRA, pragmatic clinical trials of biologics in accurately phenotyped children are needed.

Bronchoscopy in severe childhood asthma: Irresponsible or irreplaceable?

For children with severe asthma, guideline-based management focuses on the escalation of anti-inflammatory and bronchodilatory medications while addressing comorbid conditions. Bronchoscopy, in this context, has been relegated to ruling out asthma mimickers. More recently, however, there have been questions surrounding the clinical utility of bronchoscopy in severe childhood asthma. In this solicited lecture summary, we discuss the past, present, and potential future applications of bronchoscopy in severe childhood asthma.

Interleukin-22 in Allergic Airway Diseases: A Systematic Review

The immune system plays an important role in the pathogenesis of many disorders, including allergic airway diseases. There are studies suggesting that interleukin (IL)-22 can be important in the development of these diseases. However, it is not known if this cytokine acts as proinflammatory or anti-inflammatory agent. This systematic review aimed to analyze level and role of IL-22 in patients with allergic airway diseases in comparison with healthy individuals. Systematic review included only observational studies with patients having allergic rhinitis and/or allergic asthma. The primary outcome measure was IL-22 level in patients with allergic asthma and/or allergic rhinitis. A total of 95 articles were found. Overall, 6 articles were included in systematic review. Five of these studies showed that IL-22 was increased in patients with allergic airway diseases compared with control group. Majority of studies revealed relation between IL-22 level and severity of allergic asthma and allergic rhinitis. Some studies showed positive relation between IL-22 level and total immunoglobulin E (IgE), specific IgE, and eosinophil count in nasal mucosa. IL-22 level is increased in children and adults with allergic airway diseases and is likely to be associated with proinflammatory features.

Childhood Asthma: Advances Using Machine Learning and Mechanistic Studies

A paradigm shift brought by the recognition that childhood asthma is an aggregated diagnosis that comprises several different endotypes underpinned by different pathophysiology, coupled with advances in understanding potentially important causal mechanisms, offers a real opportunity for a step change to reduce the burden of the disease on individual children, families, and society. Data-driven methodologies facilitate the discovery of "hidden" structures within "big healthcare data" to help generate new hypotheses. These findings can be translated into clinical practice by linking discovered "phenotypes" to specific mechanisms and clinical presentations. Epidemiological studies have provided important clues about mechanistic avenues that should be pursued to identify interventions to prevent the development or alter the natural history of asthma-related diseases. Findings from cohort studies followed by mechanistic studies in humans and in neonatal mouse models provided evidence that environments such as traditional farming may offer protection by modulating innate immune responses and that impaired innate immunity may increase susceptibility. The key question of which component of these exposures can be translated into interventions requires confirmation. Increasing mechanistic evidence is demonstrating that shaping the microbiome in early life may modulate immune function to confer protection. Iterative dialogue and continuous interaction between experts with different but complementary skill sets, including data scientists who generate information about the hidden structures within "big data" assets, and medical professionals, epidemiologists, basic scientists, and geneticists who provide critical clinical and mechanistic insights about the mechanisms underpinning the architecture of the heterogeneity, are keys to delivering mechanism-based stratified treatments and prevention.

Management of severe asthma: a European Respiratory Society/American Thoracic Society guideline

This document provides clinical recommendations for the management of severe asthma. Comprehensive evidence syntheses, including meta-analyses, were performed to summarise all available evidence relevant to the European Respiratory Society/American Thoracic Society Task Force's questions. The evidence was appraised using the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach and the results were summarised in evidence profiles. The evidence syntheses were discussed and recommendations formulated by a multidisciplinary Task Force of asthma experts, who made specific recommendations on six specific questions. After considering the balance of desirable and undesirable consequences, quality of evidence, feasibility, and acceptability of various interventions, the Task Force made the following recommendations: 1) suggest using anti-interleukin (IL)-5 and anti-IL-5 receptor α for severe uncontrolled adult eosinophilic asthma phenotypes; 2) suggest using a blood eosinophil cut-point ≥150 μL^-1 to guide anti-IL-5 initiation in adult patients with severe asthma; 3) suggest considering specific eosinophil (≥260 μL^-1) and exhaled nitric oxide fraction (≥19.5 ppb) cut-offs to identify adolescents or adults with the greatest likelihood of response to anti-IgE therapy; 4) suggest using inhaled tiotropium for adolescents and adults with severe uncontrolled asthma despite Global Initiative for Asthma (GINA) step 4-5 or National Asthma Education and Prevention Program (NAEPP) step 5 therapies; 5) suggest a trial of chronic macrolide therapy to reduce asthma exacerbations in persistently symptomatic or uncontrolled patients on GINA step 5 or NAEPP step 5 therapies, irrespective of asthma phenotype; and 6) suggest using anti-IL-4/13 for adult patients with severe eosinophilic asthma and for those with severe corticosteroid-dependent asthma regardless of blood eosinophil levels. These recommendations should be reconsidered as new evidence becomes available.

Severe Asthma in Childhood

Severe asthma is broadly defined as asthma requiring a high level of therapy, usually high doses of inhaled corticosteroids, to bring under control. Children who remain symptomatic despite such treatment are a heterogeneous population, and bear a high burden of disease and require high resource utilization. Children with severe asthma require a comprehensive evaluation, careful consideration of alternative diagnoses and comorbid conditions, assessment of medication adherence and environmental conditions, and frequent disease monitoring.

Targeting NLRP3 Inflammasome Activation in Severe Asthma

Severe asthma (SA) is a chronic lung disease characterized by recurring symptoms of reversible airflow obstruction, airway hyper-responsiveness (AHR), and inflammation that is resistant to currently employed treatments. The nucleotide-binding oligomerization domain-like Receptor Family Pyrin Domain Containing 3 (NLRP3) inflammasome is an intracellular sensor that detects microbial motifs and endogenous danger signals and represents a key component of innate immune responses in the airways. Assembly of the NLRP3 inflammasome leads to caspase 1-dependent release of the pro-inflammatory cytokines IL-1β and IL-18 as well as pyroptosis. Accumulating evidence proposes that NLRP3 activation is critically involved in asthma pathogenesis. In fact, although NLRP3 facilitates the clearance of pathogens in the airways, persistent NLRP3 activation by inhaled irritants and/or innocuous environmental allergens can lead to overt pulmonary inflammation and exacerbation of asthma manifestations. Notably, administration of NLRP3 inhibitors in asthma models restrains AHR and pulmonary inflammation. Here, we provide an overview of the pathophysiology of SA, present molecular mechanisms underlying aberrant inflammatory responses in the airways, summarize recent studies pertinent to the biology and functions of NLRP3, and discuss the role of NLRP3 in the pathogenesis of asthma. Finally, we contemplate the potential of targeting NLRP3 as a novel therapeutic approach for the management of SA.

Toward clinically applicable biomarkers for asthma: An EAACI position paper

Inflammation, structural, and functional abnormalities within the airways are key features of asthma. Although these processes are well documented, their expression varies across the heterogeneous spectrum of asthma. Type 2 inflammatory responses are characterized by increased levels of eosinophils, FeNO, and type 2 cytokines in blood and/or airways. Presently, type 2 asthma is the best-defined endotype, typically found in patients with allergic asthma, but surprisingly also in nonallergic patients with (severe) asthma. The etiology of asthma with non-type 2 inflammation is less clear. During the past decade, targeted therapies, including biologicals and small molecules, have been increasingly integrated into treatment strategies of severe asthma. These treatments block specific inflammatory pathways or single mediators. Single or composite biomarkers help to identify patients who will benefit from these treatments. So far, only a few inflammatory biomarkers have been validated for clinical application. The European Academy of Allergy & Clinical Immunology Task Force on Biomarkers in Asthma was initiated to review different biomarker sampling methods and to investigate clinical applicability of new and existing inflammatory biomarkers (point-of-care) to support diagnosis, targeted treatment, and monitoring of severe asthma. Subsequently, we discuss existing and novel targeted therapies for asthma as well as applicable biomarkers.

Update in Pediatric Asthma: Selected Issues

Asthma is a complex condition that affects 14% of the world's children and the approach to management includes both pharmacologic as well as non-pharmacologic strategies including attention to complex socioeconomic status phenomena. After an historical consideration of asthma, allergic and immunologic aspects of asthma in children and adolescents are presented. Concepts of socioeconomic aspects of asthma are considered along with environmental features and complications of asthma disparities. Also reviewed are links of asthma with mental health disorders, sleep disturbances and other comorbidities. A stepwise approach to asthma management is discussed that includes pharmacologic and non-pharmacologic strategies in the pediatric population. The role of immunotherapy and use of various immunomodulators are considered as well.

Options of immunotherapeutic treatments for children with asthma

Introduction: Asthma is the most common chronic disease in children. Avoiding triggers, and pharmacologic treatment with short acting beta-agonist, inhaler corticosteroids and anti-leukotriene are often enough to obtain symptoms control. Nevertheless, there is a subset of children with severe asthma and poor symptom control despite maximal therapy. In these patients, anti-IgE and anti-IL5 monoclonal antibodies are suggested as the fifth step of Global Initiative for Asthma guidelines. Area covered: Immunotherapeutic treatments are now suggested for asthma management. This article will discuss the available evidence on allergen immunotherapy and biologic drugs in pediatric asthma treatment. Expert opinion: Previously published studies demonstrated a good efficacy and safety profile of Allergen Immunotherapy in patients with mild-moderate asthma and sensitization to one main allergen. New understanding of mechanisms underlying severe asthma inflammation has allowed the identifications of specific biomarkers guiding the clinician in the choice of patient specific drug. Among the suggested immunotherapeutic options, omalizumab (blocking IgE) remains the first choice for atopic 'early onset' asthma in patients aged over 6 years. Instead, mepolizumab (blocking the IL5 ligand) should be considered for 'eosinophilic' asthma. Other biologic drugs are under consideration but data on the pediatric population are still lacking.

Expression of IL-5 receptor alpha by murine and human lung neutrophils

The role of eosinophilia in atopic diseases, including asthma, is well established, as is the well-known role of IL-5 as a major eosinophilopoeitin and chemoattractant. Following influenza A virus infection of mice, type 2 innate lymphoid cells are recruited to the respiratory tract and produce large quantities of IL-5, which contributes to the recruitment of eosinophils into the infected lungs during the recovery phase of infection. We demonstrate here that while IL-5 is required for optimal recovery from influenza A virus infection in BALB/c and C57BL/6 mice, the protective effect of IL-5 is independent of eosinophils, suggesting an alternative cellular target. We describe the unexpected finding of IL-5 receptor alpha (CD125) expression on neutrophils infiltrating the inflamed mouse lungs, as well as on neutrophils at other anatomic sites. We extend this finding of neutrophil CD125 expression to humans, specifically to neutrophils found in the bronchoalveolar lavage fluid from the inflamed lungs of children with treatment-refractory asthma. We further demonstrate that the IL-5 receptor on neutrophils is capable of signal transduction. Our data provide further evidence that neutrophils can play a role bridging atopic type 2 and innate anti-microbial immunity.

Pulmonary type-2 innate lymphoid cells in paediatric severe asthma: phenotype and response to steroids

Children with severe therapy-resistant asthma (STRA) have poor control despite maximal treatment, while those with difficult asthma (DA) have poor control from failure to implement basic management, including adherence to therapy. Although recognised as clinically distinct, the airway molecular phenotype, including the role of innate lymphoid cells (ILCs) and their response to steroids in DA and STRA is unknown.Immunophenotyping of sputum and blood ILCs and T-cells from STRA, DA and non-asthmatic controls was undertaken. Leukocytes were analysed longitudinally pre- and post-intramuscular triamcinolone in children with STRA. Cultured ILCs were evaluated to assess steroid responsiveness in vitroAirway eosinophils, type 2 T-helper (Th2) cells and ILC2s were significantly higher in STRA patients compared to DA and disease controls, while IL-17+ lymphoid cells were similar. ILC2s and Th2 cells were significantly reduced in vivo following intramuscular triamcinolone and in vitro with steroids. Furthermore, asthma attacks and symptoms reduced after systemic steroids despite persistence of steroid-resistant IL-17+ cells and eosinophils.Paediatric STRA and DA have distinct airway molecular phenotypes with STRA characterised by elevated type-2 cells. Systemic corticosteroids, but not maintenance inhaled steroids resulted in improved symptom control and exacerbations concomitant with a reduction in functional ILC2s despite persistently elevated IL-17+ lymphoid cells.

Interference of miR-943-3p with secreted frizzled-related proteins4 (SFRP4) in an asthma mouse model

The aim of this study is to investigate the potential roles of miR-943-3p and its target gene secreted frizzled-related proteins4 (SFRP4) in allergic asthma and elucidate its underlying mechanism, which may prompt a new clue about developing novel treatments of this disease. An allergic asthma mouse model was generated by challenging with ovalbumin (OVA); lung pathological features of mice were viewed using H&E staining; thickness of subepithelial fibrosis and smooth muscle was measured using Masson's trichrome staining. Inflammatory cells from bronchoalveolar lavage fluid (BALF) were counted based on Diff-Quik staining and morphometric analysis. Expressions of miR-943-3p, SFRP4 and Wnt signal pathway-associated proteins were detected using RT-PCR or immunoblotting, respectively. SFRP4 was downregulated in the bronchial biopsies of allergic asthma patients and represented a unique intersection between differentially expressed genes (DEGs) and genes in the Wnt signal pathway. Both miR-943-3p upregulation and SFRP4 downregulation were detected in allergic asthma patients and OVA-induced mice. Besides, OVA-induced mice possessed more inflammatory cells in BALF including macrophage (mac), eosinophil (eos), lymphocyte (lym) and neutrophil (neu), higher expression of collagen, β-catenin and c-Myc as well as thicker subepithelial fibrosis and smooth muscle in lung than control mice. In vivo delivery of miR-943-3p agomir worsened these symptoms, while both miR-943-3p antagomir and Ad-SFRP4 administration effectively alleviated this disease. Taken together, miR-943-3p accelerated the progression of airway inflammation and remodeling in allergic asthma via suppressing the activity of SFRP4 through Wnt signaling pathway in asthma patients and OVA-induced mice.