Airway Remodeling and Inflammation in Symptomatic Infants with Reversible Airflow Obstruction

Extracellular Matrix as a Driver of Chronic Lung Diseases

The extracellular matrix (ECM) is not just a three-dimensional scaffold that provides stable support for all cells in the lungs, but also an important component of chronic fibrotic airway, vascular, and interstitial diseases. It is a bioactive entity that is dynamically modulated during tissue homeostasis and disease, that controls structural and immune cell functions and drug responses, and that can release fragments that have biological activity and that can be used to monitor disease activity. There is a growing recognition of the importance of considering ECM changes in chronic airway, vascular, and interstitial diseases, including 1) compositional changes, 2) structural and organizational changes, and 3) mechanical changes and how these affect disease pathogenesis. As altered ECM biology is an important component of many lung diseases, disease models must incorporate this factor to fully recapitulate disease-driver pathways and to study potential novel therapeutic interventions. Although novel models are evolving that capture some or all of the elements of the altered ECM microenvironment in lung diseases, opportunities exist to more fully understand cell-ECM interactions that will help devise future therapeutic targets to restore function in chronic lung diseases. In this perspective article, we review evolving knowledge about the ECM's role in homeostasis and disease in the lung.

Bacteria and viruses and their role in the preschool wheeze to asthma transition

Wheezing is the cardinal symptom of asthma; its presence early in life, mostly caused by viral infections, is a major risk factor for the establishment of persistent or recurrent disease. Early-life wheezing and asthma exacerbations are triggered by common respiratory viruses, mainly rhinoviruses (RV), and to a lesser extent, respiratory syncytial virus, parainfluenza, human metapneumovirus, coronaviruses, adenoviruses, influenza, and bocavirus. The excess presence of bacteria, several of which are part of the microbiome, has also been identified in association with wheezing and acute asthma exacerbations, including haemophilus influenza, streptococcus pneumoniae, moraxella catarrhalis, mycoplasma pneumoniae, and chlamydophila pneumonia. While it is not clear when asthma starts, its characteristics develop over time. Airway remodeling already appears between the ages of 1 and 3 years of age even prior to the presence of atopic inflammation or an asthma diagnosis. The role of genetic defect or variations hampering the airway epithelium in response to environmental stimuli and severe disease morbidity are now considered as major determinants for early structural changes. Repeated viral infections can induce and perpetuate airway hyperresponsiveness. Allergic sensitization, that often precedes infection-induced wheezing, shifts inflammation toward type-2, while common respiratory infections themselves promote type-2 inflammation. Nevertheless, most children who wheeze with viral infections during infancy and during preschool years do not develop persistent asthma. Multiple factors, including illness severity, viral etiology, allergic sensitization, and the exposome, are associated with disease persistence. Here, we summarize current knowledge and developments in infection epidemiology of asthma in children, describing the known impact of each individual agent and mechanisms of transition from recurrent wheeze to asthma.

Prevention Is Better than Cure: Impact of Allergen Immunotherapy on the Progression of Airway Disease

Allergen immunotherapy is highly effective for seasonal pollinosis. Three years of treatment results in long-term efficacy. This disease modification is accompanied by downregulation of allergen-specific Th2 responses and the induction of persistent specific IgG- and IgA-associated IgE-blocking activity. In children with seasonal rhinitis, both subcutaneous and sublingual pollen immunotherapy have been shown to reduce the development of asthma symptoms and asthma medication requirements. House dust mite tablet allergen immunotherapy has been shown to be effective for perennial mite-driven rhinitis in adults and children and may suppress asthma exacerbations, whereas its long-term efficacy has yet to be explored. The success of primary prevention of peanut allergy in childhood by introduction of peanut into the diet during infancy provides a strong rationale to explore whether primary prevention of inhalant allergies and asthma may also be possible. House dust mite allergy is a major risk factor for developing asthma. Preliminary data in at-risk children suggest that sublingual house dust mite immunotherapy initiated during infancy could reduce the onset of multiple allergen sensitizations and prevent the development of asthma at age 6 years. This possibility should now be explored in an adequately powered, prospectively randomized controlled trial.

Limited clinical role of blood eosinophil levels in early life atopic disease: A mother-child cohort study

BACKGROUND

Blood eosinophil count is a well-established biomarker of atopic diseases in older children and adults. However, its predictive role for atopic diseases in preschool children is not well established.

OBJECTIVE

To investigate the association between blood eosinophil count in children and development of atopic diseases up to age 6 years.

METHODS

We investigated blood eosinophil count at age 18 months and 6 years in relation to recurrent wheeze/asthma, atopic dermatitis, allergic rhinitis, and allergic sensitization during the first 6 years of life in the two Copenhagen Prospective Studies on Asthma in Childhood cohorts (n = 1111). Blood eosinophil count was investigated in association with remission of existing atopic disease, current atopic disease, and later development of atopic disease.

RESULTS

Blood eosinophil count at 18 months was not associated with current wheezing/asthma or atopic dermatitis, while blood eosinophil count at age 6 years was associated with increased occurrence of current wheezing/asthma (OR = 1.1; 1.04-1.16, p = .0005), atopic dermatitis (OR = 1.06; 1.01-1.1, p = .02), and allergic rhinitis (OR = 1.11; 1.05-1.18, p = .0002). Blood eosinophil count at 18 months did not predict persistence or development of recurrent wheeze/asthma or atopic dermatitis at age 6 years.

CONCLUSION

Blood eosinophil count at 18 months was not associated with current wheezing/asthma or atopic dermatitis and did not predict persistence or development of disease. This implies a limited clinical role of blood eosinophil levels in early-life atopic disease and questions the clinical value of blood eosinophil counts measured in toddlers as a predictive biomarker for subsequent atopic disease in early childhood.

Small airway disease in post-acute COVID-19 syndrome, a non-conventional approach in three years follow-up of a patient with long COVID: a case report

BACKGROUND

Small airways disease (SAD), a novel finding described in post-acute COVID-19 patients, should be suspected when respiratory symptoms continue, air trapping persists on expiratory CT scans, and imaging findings fail to improve despite objectively better conventional pulmonary function test (PFT) parameters. The forced oscillation technique (FOT) and Multiple breathing washout (MBW) are both very sensitive methods for detecting anomalies in the peripheral airways.

CASE PRESENTATION

We discuss the case of a 60-year-old Hispanic patient who had severe COVID-19 pneumonia and developed dyspnea, fatigue, and limited daily activity a year later. The PFTs revealed restrictive lung disease, as seen by significant diffusing capacity of the lungs for carbon monoxide (DLCO) decrease, severe desaturation, and poor 6-min walk test (6MWT) performance. The patient was treated with lowering corticosteroids as well as pulmonary rehabilitation (PR). During the 24-month follow-up, the dyspnea and fatigue persisted. On PFTs, 6MWT performance and restricted pattern improved slightly, but MBW discovered significant ventilatory inhomogeneity. FOT revealed substantial peripheral airway obstructive abnormalities. On CT scans, air trapping and ground-glass opacities (GGO) improved somewhat. The patient used a bronchodilator twice a day and low-dose inhaled corticosteroids (160 µg of budesonide and 4.5 µg of formoterol fumarate dihydrate) for nine months. PR sessions were resuming. The restricting parameters were stabilized and the DLCO had normalized after 36 months, with a 6MWT performance of 87% but significant desaturation. The CT scan revealed traction bronchiectasis, low GGO, and persistent air trapping. Without normalization, FOT and MBW scores improved, indicating small airway disease.

CONCLUSIONS

The necessity of integrating these tests when detecting SAD is emphasized in our paper. This article lays the foundation for future research into the best ways to manage and monitor SAD in post-acute COVID-19 patients.

Airway epithelial development and function: A key player in asthma pathogenesis?

Though asthma is a common and relatively easy to diagnose disease, attempts at primary or secondary prevention, and cure, have been disappointing. The widespread use of inhaled steroids has dramatically improved asthma control but has offered nothing in terms of altering long-term outcomes or reversing airway remodeling and impairment in lung function. The inability to cure asthma is unsurprising given our limited understanding of the factors that contribute to disease initiation and persistence. New data have focused on the airway epithelium as a potentially key factor orchestrating the different stages of asthma. In this review we summarize for the clinician the current evidence on the central role of the airway epithelium in asthma pathogenesis and the factors that may alter epithelial integrity and functionality.

Early Prediction of Asthma

The clinical manifestations of asthma in children are highly variable, are associated with different molecular and cellular mechanisms, and are characterized by common symptoms that may diversify in frequency and intensity throughout life. It is a disease that generally begins in the first five years of life, and it is essential to promptly identify patients at high risk of developing asthma by using different prediction models. The aim of this review regarding the early prediction of asthma is to summarize predictive factors for the course of asthma, including lung function, allergic comorbidity, and relevant data from the patient's medical history, among other factors. This review also highlights the epigenetic factors that are involved, such as DNA methylation and asthma risk, microRNA expression, and histone modification. The different tools that have been developed in recent years for use in asthma prediction, including machine learning approaches, are presented and compared. In this review, emphasis is placed on molecular mechanisms and biomarkers that can be used as predictors of asthma in children.

Immunoregulation of asthma by type 2 cytokine therapies: Treatments for all ages?

Asthma is classically considered to be a disease of type 2 immune dysfunction, since many patients exhibit the consequences of excess secretion of cytokines such as IL-4, IL-5, and IL-13 concomitant with inflammation typified by eosinophils. Mouse and human disease models have determined that many of the canonical pathophysiologic features of asthma may be caused by these disordered type 2 immune pathways. As such considerable efforts have been made to develop specific drugs targeting key cytokines. There are currently available multiple biologic agents that successfully reduce the functions of IL-4, IL-5, and IL-13 in patients, and many improve the course of severe asthma. However, none are curative and do not always minimize the key features of disease, such as airway hyperresponsiveness. Here, we review the current therapeutic landscape targeting type 2 immune cytokines and discuss evidence of efficacy and limitations of their use in adults and children with asthma.

Basic clinical management of preschool wheeze

Preschool wheeze is very common and often difficult to treat. Most children do not require any investigations; only a detailed history and physical examination to ensure an alternative diagnosis is not being missed; and the differential diagnosis, and hence investigation protocols for the child in whom a major illness is suspected, shows geographical variation. The pattern of symptoms may be divided into episodic viral and multiple trigger to guide treatment, but the pattern of symptoms must be re-assessed regularly. However, symptom patterns are a poor guide to underlying pathology. Attention to the proper use of spacers, and adverse environmental exposures such as tobacco smoke exposure, is essential. There are no disease-modifying therapies, so therapy is symptomatic. This paper reviews recent advances in treatment, including new data on the place of leukotriene receptor antagonists, prednisolone for acute attacks of wheeze, and antibiotics, based on new attempts to understand the underlying pathology in a way that is clinically practical.

Blood Eosinophils for Prediction of Exacerbation in Preschool Children With Recurrent Wheezing

BACKGROUND

Although clinical features of type 2 inflammation have been associated with poorer longitudinal outcomes in preschool children with recurrent wheezing, it remains difficult to predict which children are at highest risk for poor outcomes during a routine clinical encounter.

OBJECTIVE

We tested the hypothesis that prespecified cut points of blood eosinophil counts would predict exacerbation and treatment response outcomes in preschool children with recurrent wheezing and that prediction could be improved with the addition of a second biomarker.

METHODS

Data from 3 clinical trials of 1,074 preschool children aged 12 to 71 months with recurrent wheezing were merged. The primary outcome was the occurrence of any exacerbation during follow-up. Secondary outcomes included the annualized rate of wheezing exacerbations and the occurrence of any exacerbation requiring hospitalization. Exploratory analyses focused on exacerbation outcomes, offline exhaled nitric oxide concentrations, and caregiver-reported asthma control scores after inhaled corticosteroid treatment initiation.

RESULTS

Each blood eosinophil cut point was associated with increased odds of exacerbation, higher exacerbation rates, and greater hospitalization occurrence in preschool children with recurrent wheezing. However, outcome detection was improved in children with more elevated blood eosinophil counts. Addition of a second biomarker of type 2 inflammation improved outcome detection and was further associated with an improved response to initiation of daily inhaled corticosteroids in exploratory analyses. However, the specificity of blood eosinophils was poor.

CONCLUSIONS

Although validation studies are warranted, blood eosinophil cut points may be useful for clinical assessment and future studies of exacerbation and treatment response in preschool children with recurrent wheezing.

Bronchial Remodeling-based Latent Class Analysis Predicts Exacerbations in Severe Preschool Wheezers

Rationale: Children with preschool wheezing represent a very heterogeneous population with wide variability regarding their clinical, inflammatory, obstructive, and/or remodeling patterns. We hypothesized that assessing bronchial remodeling would help clinicians to better characterize severe preschool wheezers. Objectives: The main objective was to identify bronchial remodeling-based latent classes of severe preschool wheezers. Secondary objectives were to compare cross-sectional and longitudinal clinical and biological data between classes and to assess the safety of bronchoscopy. Methods: This double-center prospective study (NCT02806466) included severe preschool wheezers (1-5 yr old) requiring fiberoptic bronchoscopy. Bronchial remodeling parameters (i.e., epithelial integrity, reticular basement membrane [RBM] thickness, mucus gland, fibrosis and bronchial smooth muscle [BSM] areas, the density of blood vessels, and RBM-BSM distance) were assessed and evaluated by latent class analysis. An independent cohort of severe preschool wheezers (NCT04558671) was used to validate our results. Measurements and Main Results: Fiberoptic bronchoscopy procedures were well tolerated. A two-class model was identified: Class BR1 was characterized by increased RBM thickness, normalized BSM area, the density of blood vessels, decreased mucus gland area, fibrosis, and RBM-BSM distance compared with Class BR2. No significant differences were found between classes in the year before fiberoptic bronchoscopy. By contrast, Class BR1 was associated with a shorter time to first exacerbation and an increased risk of both frequent (3 or more) and severe exacerbations during the year after bronchoscopy in the two cohorts. Conclusions: Assessing bronchial remodeling identified severe preschool wheezers at risk of frequent and severe subsequent exacerbations with a favorable benefit to risk ratio.

Intermittent Tiotropium Bromide for Episodic Wheezing: A Randomized Trial

BACKGROUND AND OBJECTIVES

Options to treat and prevent episodic wheezing in children are scarce. Our objective was to assess the efficacy of intermittent tiotropium bromide treatment in early childhood episodic wheezing.

METHODS

This 48-week, randomized, open-label, controlled, parallel-group trial was conducted at 4 hospitals in Finland. Children aged 6 to 35 months with 2 to 4 physician-confirmed episodes of wheeze and/or shortness of breath were considered eligible. Study participants were randomly allocated to receive 1 of 3 treatments: once-daily tiotropium bromide 5 µg for 7 to 14 days during respiratory tract infections and as-needed albuterol sulfate 0.2 mg (n = 27), twice-daily fluticasone propionate 125 µg for 7 to 14 days during respiratory tract infections and as-needed albuterol sulfate 0.2 mg (n = 25), or as-needed albuterol sulfate 0.2 mg alone (n = 28). The primary outcome was efficacy, assessed as intention-to-treat by comparing the proportion of episode-free days (the days lacking symptoms or treatments) between the treatment groups.

RESULTS

The proportion of episode-free days was higher in those receiving intermittent tiotropium bromide (median 97% [interquartile range, 93% to 99%]) than in those receiving intermittent fluticasone propionate (87% [78% to 93%], P = .002), or with as-needed albuterol sulfate alone (88% [79% to 95%], P = .003). Adjustment with allergic sensitization, the baseline number of physician-confirmed episodes of wheeze and/or shortness of breath, or short-course glucocorticoid treatment in the 2 weeks before the enrollment, did not affect the result. Intervention-related adverse events were not seen.

CONCLUSIONS

Intermittent tiotropium bromide treatment may be an effective alternative to current therapies for episodic wheezing. Before implementation of use, further research on safety and efficacy is indicated.

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.

Impact of early life exposures on respiratory disease

The antecedents of asthma and chronic obstructive pulmonary disease (COPD) lie before school age. Adverse effects are transgenerational, antenatal and in the preschool years. Antenatal adverse effects impair spirometry by causing low birth weight, altered lung structure and immune function, and sensitizing the foetus to later insults. The key stages of normal lung health are lung function at birth, lung growth to a plateau age 20-25 years, and the phase of decline thereafter; contrary to perceived wisdom, accelerated decline is not related to smoking. There are different trajectories of lung function. Lung function usually tracks from preschool to late middle age. Asthma is driven by antenatal and early life influences. The airflow obstruction, emphysema and multi-morbidity of COPD all start early. Failure to reach a normal plateau and accelerated decline in lung function are risk factors for COPD. Airway disease cannot be prevented in adult life; prevention must start early.

Impact of early life exposures on COPD in adulthood: A systematic review and meta-analysis

Early life represents a critical period for the development and growth of the lungs. Adverse exposures in this stage may drive the development of chronic obstructive pulmonary disease (COPD). Thus, we quantitatively evaluated the impact of different early life exposures on COPD in adulthood. The PubMed, Embase and Cochrane Library electronic databases were searched for articles published from January 2001 to October 2020. A total of 30 studies (795,935 participants) met the criteria and were included in the review. We found a significant association of COPD with childhood serious respiratory infections, pneumonia or bronchitis (pooled adjusted OR [aOR], 2.23 [95% CI, 1.63-3.07]). The probability of COPD was increased 3.45-fold for children with than without asthma (pooled aOR, 3.45 [95% CI, 2.37-5.02]). In addition, the probability of COPD was associated with maternal smoking (pooled aOR, 1.42 [95% CI, 1.17-1.72]), any child maltreatment (pooled aOR, 1.30 [95% CI, 1.18-1.42]) and low birth weight (pooled aOR, 1.58 [95% CI, 1.08-2.32]) but not childhood environmental tobacco smoke exposure (pooled aOR, 1.15 [0.83-1.61]) or premature birth (pooled aOR, 1.17 [95% CI, 0.87-1.58]). Furthermore, subgroup analyses revealed that probability was increased for only women with childhood physical abuse, sexual abuse and exposure to intimate partner violence. Factors resulting in COPD in adults could trace back to early life. Childhood respiratory disease, maltreatment, maternal smoking and low birth weight increase the risk of COPD. Promising advances in prevention strategies for early life exposures could markedly decrease the risk of COPD.

Airway Wall Remodeling in Childhood Asthma-A Personalized Perspective from Cell Type-Specific Biology

Airway wall remodeling is a pathology occurring in chronic inflammatory lung diseases including asthma, chronic obstructive pulmonary disease, and fibrosis. In 2017, the American Thoracic Society released a research statement highlighting the gaps in knowledge and understanding of airway wall remodeling. The four major challenges addressed in this statement were: (i) the lack of consensus to define “airway wall remodeling” in different diseases, (ii) methodologic limitations and inappropriate models, (iii) the lack of anti-remodeling therapies, and (iv) the difficulty to define endpoints and outcomes in relevant studies. This review focuses on the importance of cell-cell interaction, especially the bronchial epithelium, in asthma-associated airway wall remodeling. The pathology of “airway wall remodeling” summarizes all structural changes of the airway wall without differentiating between different pheno- or endo-types of asthma. Indicators of airway wall remodeling have been reported in childhood asthma in the absence of any sign of inflammation; thus, the initiation event remains unknown. Recent studies have implied that the interaction between the epithelium with immune cells and sub-epithelial mesenchymal cells is modified in asthma by a yet unknown epigenetic mechanism during early childhood.

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.

Recurrent Severe Preschool Wheeze: From Pre-Specified Diagnostic Labels to Underlying Endotypes

Rationale: Preschool wheezing is heterogeneous, but the underlying mechanisms are poorly understood.

Objectives: To investigate lower airway inflammation and infection in preschool children with different clinical diagnoses undergoing elective bronchoscopy and BAL.

Methods: We recruited 136 children aged 1–5 years (105 with recurrent severe wheeze [RSW]; 31 with nonwheezing respiratory disease [NWRD]). Children with RSW were assigned as having episodic viral wheeze (EVW) or multiple-trigger wheeze (MTW). We compared lower airway inflammation and infection in different clinical diagnoses and undertook data-driven analyses to determine clusters of pathophysiological features, and we investigated their relationships with prespecified diagnostic labels.

Measurements and Main Results: Blood eosinophil counts and percentages and allergic sensitization were significantly higher in children with RSW than in children with a NWRD. Blood neutrophil counts and percentages, BAL eosinophil and neutrophil percentages, and positive bacterial culture and virus detection rates were similar between groups. However, pathogen distribution differed significantly, with higher detection of rhinovirus in children with RSW and higher detection of Moraxella in sensitized children with RSW. Children with EVW and children with MTW did not differ in terms of blood or BAL-sample inflammation, or bacteria or virus detection. The Partition around Medoids algorithm revealed four clusters of pathophysiological features: 1) atopic (17.9%), 2) nonatopic with a low infection rate and high use of inhaled corticosteroids (31.3%), 3) nonatopic with a high infection rate (23.1%), and 4) nonatopic with a low infection rate and no use of inhaled corticosteroids (27.6%). Cluster allocation differed significantly between the RSW and NWRD groups (RSW was evenly distributed across clusters, and 60% of the NWRD group was assigned to cluster 4; P < 0.001). There was no difference in cluster membership between the EVW and MTW groups. Cluster 1 was dominated by Moraxella detection (P = 0.04), and cluster 3 was dominated by Haemophilus or Staphylococcus or Streptococcus detection (P = 0.02).

Conclusions: We identified four clusters of severe preschool wheeze, which were distinguished by using sensitization, peripheral eosinophilia, lower airway neutrophilia, and bacteriology.

Factors and mechanisms contributing to the development of preschool wheezing disorders

INTRODUCTION

Half of all children will experience an episode of wheezing by their sixth birthday and acute episodes of wheezing in preschool children account for the majority of all childhood hospital admissions for wheeze. Recurrent preschool wheezing associates with early loss of lung function and a life-long impact on lung health.

AREAS COVERED

We reviewed the literature on PubMed from August 2010-2020 focussing on factors associated with wheeze inception and persistence, paying specific attention to mechanistic studies that have investigated the impact of early life exposures in shaping immune responses in children with underlying susceptibility to wheezing. In particular, the role of early allergen sensitization, respiratory infections, and the impact of the environment on shaping the airway microbiome and resulting immune responses are discussed.

EXPERT OPINION

There is an abundance of associative data showing the role of in utero and postnatal factors influencing wheeze onset and persistence. However, mechanistic and stratified, biomarker-based interventional studies that confirm these associations are now needed if we are to impact the significant healthcare burden resulting from preschool wheezing disorders.

Mitochondria are involved in bronchial smooth muscle remodeling in severe preschool wheezers

BACKGROUND

Bronchial remodeling is a key feature of asthma that is already present in preschoolers with wheezing. Moreover, bronchial smooth muscle (BSM) remodeling at preschool age is predictive of asthma at school age. However, the mechanism responsible for BSM remodeling in preschoolers with wheezing remains totally unknown. In contrast, in adult asthma, BSM remodeling has been associated with an increase in BSM cell proliferation related to increased mitochondrial mass and biogenesis triggered by an altered calcium homeostasis. Indeed, BSM cell proliferation was decreased in vitro by the calcium channel blocker gallopamil.

OBJECTIVE

Our aim was to investigate the mechanisms involved in BSM cell proliferation in preschoolers with severe wheezing, with special attention to the role of mitochondria and calcium signaling.

METHODS

Bronchial tissue samples obtained from 12 preschool controls without wheezing and 10 preschoolers with severe wheezing were used to measure BSM mass and establish primary BSM cell cultures. BSM cell proliferation was assessed by manual counting and flow cytometry, ATP content was assessed by bioluminescence, mitochondrial respiration was assessed by using either the Seahorse or Oroboros technique, mitochondrial mass and biogenesis were assessed by immunoblotting, and calcium response to carbachol was assessed by confocal microscopy. The effect of gallopamil was also evaluated.

RESULTS

BSM mass, cell proliferation, ATP content, mitochondrial respiration, mass and biogenesis, and calcium response were all increased in preschoolers with severe wheezing compared with in the controls. Gallopamil significantly decreased BSM mitochondrial biogenesis and mass, as well as cell proliferation.

CONCLUSION

Mitochondria are key players in BSM cell proliferation in preschoolers with severe wheezing and could represent a potential target to treat BSM remodeling at an early stage of the disease.

Risk factors for recurrent wheezing after bronchiolitis in infants: 2-year follow up in China

Background

Infants with bronchiolitis have an increased risk of developing recurrent wheezing and asthma. However, the risk factors for the development of recurrent wheezing after bronchiolitis remains controversial. Our study was to investigate risk factors of post-bronchiolitis recurrent wheezing.

Methods

Infants with bronchiolitis were enrolled from November 2016 through March 2017. Nasopharyngeal aspirates were obtained for detection of respiratory viruses which were analyzed by reverse transcriptase polymerase chain reaction (RT-PCR) and direct immunofluorescent assay. Serum cytokines including TSLP, IL2, IL13, TIMP-1, MMP-9, IL33, IL5, IL4, IL25, TNF- α and MIP-1α were measured by flow cytometry. Patients were followed up every 3 months for a duration of 2 years by telephone or at outpatient appointments.

Results

We enrolled 89 infants, of which 81 patients were successfully followed up. In total, 22.2% of patients experienced recurrent wheezing episodes. The proportion of patients with history of eczema, systemic glucocorticoid use and patients with moderate-to-severe disease were significantly higher in the recurrent wheezing group than the non-recurrent wheezing group (83.3% vs 52.4%; 66.7% vs 36.5%; 61.1% vs 33.3%, respectively, all P < 0.05); There were no significant differences between patients with and without recurrent wheezing episodes in the levels of TSLP, IL2, IL13, TIMP-1, MMP-9, IL33, IL5, IL4, IL25, TNF- α and MIP-1α (P > 0.05). Logistic regression analysis showed that history of eczema was an independent risk factor for post-bronchiolitis recurrent wheezing (odds ratio [OR] = 5.622; 95% confidence interval [CI], 1.3–24.9; P = 0.023).

Conclusion

The incidence of recurrent wheezing among infants after contracting bronchiolitis was 22.2% during a 2-year follow-up. History of eczema was the only independent risk factor identified and no correlation was found between the specific virus and disease severity in children with post-bronchiolitis recurrent wheezing.

Immunologic Pathophysiology and Airway Remodeling Mechanism in Severe Asthma: Focused on IgE-Mediated Pathways

Despite the expansion of the understanding in asthma pathophysiology and the continual advances in disease management, a small subgroup of patients remains partially controlled or refractory to standard treatments. Upon the identification of immunoglobulin E (IgE) and other inflammatory mediators, investigations and developments of targeted agents have thrived. Omalizumab is a humanized monoclonal antibody that specifically targets the circulating IgE, which in turn impedes and reduces subsequent releases of the proinflammatory mediators. In the past decade, omalizumab has been proven to be efficacious and well-tolerated in the treatment of moderate-to-severe asthma in both trials and real-life studies, most notably in reducing exacerbation rates and corticosteroid use. While growing evidence has demonstrated that omalizumab may be potentially beneficial in treating other allergic diseases, its indication remains confined to treating severe allergic asthma and chronic idiopathic urticaria. Future efforts may be bestowed on determining the optimal length of omalizumab treatment, seeking biomarkers that could better predict treatment response and as well as extending its indications.

A randomized trial of subcutaneous allergy immunotherapy in inner-city children with asthma less than 4 years of age

BACKGROUND

Allergic sensitization to environmental allergens in the first years of life is a strong predictor of asthma morbidity in children. Allergy immunotherapy can improve asthma and allergy outcomes, but its efficacy in inner-city, atopic children of less than 4 years of age with recurrent wheezing has not yet been established.

OBJECTIVE

To determine whether subcutaneous allergy immunotherapy improves asthma in a population of US inner-city children when started at less than 4 years of age.

METHODS

In a randomized controlled, open-label phase I-II single-center trial in the Bronx, New York, 58 children with recurrent wheezing or physician-diagnosed asthma were randomized to receive asthma standard of care treatment with or without a 3-year course of multiple allergen subcutaneous immunotherapy.

RESULTS

A total of 23 children in the control group and 27 children in the immunotherapy group began the study. A total of 20 of 27 children commencing immunotherapy completed at least 2 years of immunotherapy. There was no difference in asthma medication and symptom scores between the treatment or control groups over time. Similarly, naso-ocular symptoms and allergy medication use were similar in both groups over time. Nevertheless, asthma-related quality of life improved in the immunotherapy group compared with the control group (P = .03).

CONCLUSION

With the exception of asthma-related quality of life, allergy immunotherapy was ineffective in improving asthma outcomes in this population of inner-city children of less than 4 years of age. These findings suggest that the effects of allergy immunotherapy depend on population-specific factors and highlight the importance of precise predictors of immunotherapy efficacy.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01028560.

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.

What Have In Vitro Co-Culture Models Taught Us about the Contribution of Epithelial-Mesenchymal Interactions to Airway Inflammation and Remodeling in Asthma?

As the lung develops, epithelial-mesenchymal crosstalk is essential for the developmental processes that drive cell proliferation, differentiation, and extracellular matrix (ECM) production within the lung epithelial-mesenchymal trophic unit (EMTU). In asthma, a number of the lung EMTU developmental signals have been associated with airway inflammation and remodeling, which has led to the hypothesis that aberrant activation of the asthmatic EMTU may lead to disease pathogenesis. Monoculture studies have aided in the understanding of the altered phenotype of airway epithelial and mesenchymal cells and their contribution to the pathogenesis of asthma. However, 3-dimensional (3D) co-culture models are needed to enable the study of epithelial-mesenchymal crosstalk in the setting of the in vivo environment. In this review, we summarize studies using 3D co-culture models to assess how defective epithelial-mesenchymal communication contributes to chronic airway inflammation and remodeling within the asthmatic EMTU.

Preschool Wheezing: Trajectories and Long-Term Treatment

Wheezing is very common in infancy affecting one in three children during the first 3 years of life. Several wheeze phenotypes have been identified and most rely on temporal pattern of symptoms. Assessing the risk of asthma development is difficult. Factors predisposing to onset and persistence of wheezing such as breastfeeding, atopy, indoor allergen exposure, environmental tobacco smoke and viral infections are analyzed. Inhaled corticosteroids are recommended as first choice of controller treatment in all preschool children irrespective of phenotype, but they are particularly beneficial in terms of fewer exacerbations in atopic children. Other therapeutic options include the addition of montelukast or the intermittent use of inhaled corticosteroids. Overuse of inhaled steroids must be avoided. Therefore, adherence to treatment and correct administration of the medications need to be checked at every visit.

A prenatally disrupted airway epithelium orchestrates the fetal origin of asthma in mice

BACKGROUND

Prenatal challenges such as maternal stress perception increase the risk and severity of asthma during childhood. However, insights into the trajectories and targets underlying the pathogenesis of prenatally triggered asthma are largely unknown. The developing lung and immune system may constitute such targets.

OBJECTIVE

Here we have aimed to identify the differential sex-specific effects of prenatal challenges on lung function, immune response, and asthma severity in mice.

METHODS

We generated bone marrow chimeric (BMC) mice harboring either prenatally stress-exposed lungs or a prenatally stress-exposed immune (hematopoietic) system and induced allergic asthma via ovalbumin. Next-generation sequencing (RNA sequencing) of lungs and assessment of airway epithelial barrier function in ovalbumin-sensitized control and prenatally stressed offspring was also performed.

RESULTS

Profoundly enhanced airway hyperresponsiveness, inflammation, and fibrosis were exclusively present in female BMC mice with prenatally stress-exposed lungs. These effects were significantly perpetuated if both the lungs and the immune system had been exposed to prenatal stress. A prenatally stress-exposed immune system alone did not suffice to increase the severity of these asthma features. RNA sequencing analysis of lungs from prenatally stressed, non-BMC, ovalbumin-sensitized females unveiled a deregulated expression of genes involved in asthma pathogenesis, tissue remodeling, and tight junction formation. It was also possible to independently confirm a tight junction disruption. In line with this, we identified an altered perinatal and/or postnatal expression of genes involved in lung development along with an impaired alveolarization in female prenatally stressed mice.

CONCLUSION

Here we have shown that the fetal origin of asthma is orchestrated by a disrupted airway epithelium and further perpetuated by a predisposed immune system.

Airway hyperresponsiveness, remodeling and inflammation in infants with wheeze

BACKGROUND

The relationship of airway hyperresponsiveness to airway remodeling and inflammation in infants with wheeze is unclear.

OBJECTIVE

To investigate airway hyperresponsiveness, remodeling and inflammation in infants with wheeze and troublesome breathing.

METHODS

Inclusion criteria were as follows: full-term, 3-23 months of age; doctor -diagnosed wheeze and persistent recurrent troublesome breathing; without obvious structural defect, suspicion of ciliary dyskinesia, cystic fibrosis, immune deficiency or specified use of corticosteroids. Airway hyperresponsiveness (AHR) was evaluated by performing a methacholine bronchial challenge test combined with whole body plethysmography and rapid thoracoabdominal compression. Endobronchial biopsies were analysed for remodeling (thickness of reticular basement membrane and amount of airway smooth muscle) and for inflammation (numbers of inflammatory cells). Correlation analyses were performed.

RESULTS

Forty-nine infants fulfilled the inclusion criteria for the present study. Median age was 1.06 years (IQR 0.6; 1.5). Lung function was impaired in 39/49 (80%) children, at the median age of 1.1 years. Methacholine challenge was successfully performed in 38/49 children. Impaired baseline lung function was correlated with AHR (P = .047, Spearman). In children with the most sensitive quartile of AHR, the percentage of median bronchial airway smooth muscle % and the number of bronchial mast cells in airway smooth muscle were not significantly higher compared to others (P = .057 and 0.056, respectively). No association was found between AHR and thickness of reticular basement membrane or inflammatory cells. Only a small group of children with both atopy and AHR (the most reactive quartile) had thicker airway smooth muscle area than non-atopics with AHR (P = .031).

CONCLUSIONS AND CLINICAL RELEVANCE

These findings do not support the concept that AHR in very young children with wheeze is determined by eosinophilic inflammation or clear-cut remodeling although it is associated with impaired baseline lung function. The possible association of increased airway smooth muscle area among atopic children with AHR remains to be confirmed.

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.

Persistent Asthma from Childhood to Adulthood Presents a Distinct Phenotype of Adult Asthma

BACKGROUND

In approximately 30% of children with asthma, the condition persists into adulthood. The longer duration of asthma in these patients is a risk factor for poor asthma control. However, the characteristics of adult patients with asthma that has persisted since childhood are not well documented.

OBJECTIVE

We sought to compare the clinical characteristics among patients with adult-onset asthma, patients who outgrew childhood asthma but relapsed, and patients with persistent asthma since childhood.

METHODS

We conducted a cross-sectional study of adult patients with asthma who visited our hospital. We classified them into 3 groups: those with adult-onset asthma (adult-onset), those who had remitted childhood asthma that relapsed (relapsed), and those who had asthma that had persisted since childhood (persistent). The clinical characteristics of these groups were compared.

RESULTS

A total of 1443 patients were enrolled. The persistent group was younger and included fewer patients with a smoking history. There were statistically significant differences among the 3 groups in the percentages of patients with a family history of asthma and comorbidities of allergic rhinitis and atopic dermatitis. The proportion of patients with severe asthma differed among the 3 groups (31% in the adult-onset group, 34% in the relapsed group, and 40% in the persistent group; P = .015). The values of forced expiratory flow at 75% of vital capacity were lower in the persistent group than the relapsed or adult-onset group. A multivariable logistic regression analysis (dependent variable: severe asthma) in each group revealed that the factors associated with severe asthma differed among the adult-onset, relapsed, and persistent groups. When we established an overall model that included interaction terms of cohort-by-other factors, there was a trend that comorbidity of allergic rhinitis affected the severity of asthma differently in the relapsed group compared with the other groups.

CONCLUSION

The clinical phenotype of asthma that persists from childhood to adulthood seems to be a distinct phenotype of adult asthma.

Tiotropium in children and adolescents with asthma

BACKGROUND

Asthma is a major cause of morbidity in children, despite the availability of various treatments. In adults, tiotropium-a long-acting muscarinic antagonist-as add-on therapy to an inhaled corticosteroid with or without a long-acting β₂-agonist provides clinical benefit with a safety profile similar to placebo.

OBJECTIVE

To review published evidence on the efficacy and safety of tiotropium as add-on a long-acting muscarinic antagonist therapy in children and adolescents with asthma that is uncontrolled despite use of an inhaled corticosteroid with or without additional controller medication(s).

METHODS

We searched PubMed from inception until June 12, 2018, for randomized controlled trials of children and adolescents aged 1 to 17 years treated with tiotropium and reporting a primary outcome of any pulmonary function test and a secondary outcome of adverse events.

RESULTS

Overall, 7 randomized controlled trials of 1902 preschool children (aged 1-5 years; n = 102), school-age children (aged 6-11 years; n = 905), and adolescents (aged 12-17 years; n = 895) with moderate to severe asthma were included in the analysis. Once-daily tiotropium (5, 2.5, or 1.25 μg) improved lung function parameters, including peak and trough forced expiratory volume in 1 second, vs placebo. Commonly reported adverse events across treatment groups included asthma worsening or exacerbations, decreased peak expiratory flow rate, nasopharyngitis, viral respiratory tract infection, and respiratory tract infection.

CONCLUSION

Once-daily tiotropium as add-on therapy is efficacious and safe in adolescents and children with moderate to severe asthma. These results support the expanded indication by regulatory authorities for add-on tiotropium in patients 6 years or older.

Environment and Host-Genetic Determinants in Early Development of Allergic Asthma: Contribution of Fungi

Asthma is a chronic debilitating airway disease affecting millions of people worldwide. Although largely thought to be a disease of the first world, it is now clear that it is on the rise in many middle- and lower-income countries. The disease is complex, and its etiology is poorly understood, which explains failure of most treatment strategies. We know that in children, asthma is closely linked to poor lung function in the first 3-years of life, when the lung is still undergoing post-natal alveolarization phase. Epidemiological studies also suggest that environmental factors around that age do play a critical part in the establishment of early wheezing which persists until adulthood. Some of the factors that contribute to early development of asthma in children in Western world are clear, however, in low- to middle-income countries this is likely to differ significantly. The contribution of fungal species in the development of allergic diseases is known in adults and in experimental models. However, it is unclear whether early exposure during perinatal or post-natal lung development influences a protective or promotes allergic asthma. Host immune cells and responses will play a crucial part in early development of allergic asthma. How immune cells and their receptors may recognize fungi and promote allergic asthma or protect by tolerance among other immune mechanisms is not fully understood in this early lung development stage. The aim of this review is to discuss what fungal species are present during early exposure as well as their contribution to the development of allergic responses. We also discuss how the host has evolved to promote tolerance to limit hyper-responsiveness to innocuous fungi, and how host evasion by fungi during early development consequentially results in allergic diseases.

Early Airway Pathological Changes in Children: New Insights into the Natural History of Wheezing

Asthma is a heterogeneous condition characterized by reversible airflow limitation, with different phenotypes and clinical expressions. Although it is known that asthma is influenced by age, gender, genetic background, and environmental exposure, the natural history of the disease is still incompletely understood. Our current knowledge of the factors determining the evolution from wheezing in early childhood to persistent asthma later in life originates mainly from epidemiological studies. The underlying pathophysiological mechanisms are still poorly understood. The aim of this review is to converge epidemiological and pathological evidence early in the natural history of asthma to gain insight into the mechanisms of disease and their clinical expression.

Eosinophil cell count in bronchoalveolar lavage fluid in early childhood wheezing: is it predictive of future asthma?

Objective: Increased eosinophil level in bronchoalveolar lavage fluid (BALF) characterizes asthma in school-age children and adults and has been suggested as a marker for disease severity and response to treatment. We aimed to investigate the occurrence and yield of BALF eosinophil cell count in preschool children with recurrent wheezing and its possible relation to future diagnosis of asthma. Methods: BALF was retrospectively studied in young wheezy children and its relation to asthma at age 6 years was evaluated. BALF from children aged 1-48 months (mean = 20.4) was analyzed in preschool wheezy children. Children with anatomical airway obstruction and other lower airway/lung diseases who underwent BALF served as controls. Assessment of asthma was accomplished at 6 years. Results: Eighty-two children were included. The mean age during bronchoscopy and BAL was 20.4 ± 14.4 months (range: 1-48 months). Twenty-six patients had recurrent preschool wheezing, 13 anatomical airway obstruction and 43 had other lower airways/lung diseases. Groups were comparable for age during bronchoscopy and gender. No difference was found between groups for any of the BALF cell types. Eosinophils were very low in all three groups [mean (interquartile range): 0 (0-0.4), 0 (0-0.8), and 0.4 (0-1), respectively, p = 0.25]. No difference in eosinophil levels during bronchoscopy was found between asthmatic children to non-asthmatic as defined at age 6 years. Conclusions: Wheezing in preschool children is not associated with increased BALF eosinophils; hence, at this age, the diagnostic yield of BALF for cell count analysis for diagnosing asthma is limited and is not routinely indicated.

Question 3: Can we diagnose asthma in children under the age of 5 years?

The diagnosis of asthma in children under five years has been controversial due to changing concepts of what true asthma is in this age group. Previous diagnostic algorithms that used clinical indices to predict the persistence of asthma symptoms or phenotypes based on asthma triggers do not predict which children will benefit from asthma medication. A pragmatic approach to asthma diagnosis in this age group is based on identifying signs and symptoms of reversible airflow obstruction and documenting their response to asthma medication. Hopefully, this approach will provide clearer guidance to clinicians and improve asthma morbidity in these young children.

Early Lung Function and Future Asthma

Asthmatic adults with lower lung function have been described as having had this worse condition early in life. Lung function is reduced in children with persistent asthma and continues low throughout adult life. The challenge is to know if impaired lung function is a risk factor of asthma, as a consequence of special congenital characteristics of the airways, or whether asthmatic patients suffer a loss in lung function as early as 9 years of age as a consequence of very precocious remodeling of the airways. The loss is so early in life that it is probably a congenital characteristic, however there is not a cut-off point with clinical interest to predict risk of asthma later in life. There are contradictory results regarding whether asthmatic children lose lung function as a consequence of the airway remodeling by the illness itself. This aspect seemed to be shown for children at risk-the offspring of asthmatic mothers. The early BHR seems to be very frequent even in healthy infants, but is probably not a risk factor for asthma years later; except in the offspring of asthmatic mothers in which it has been shown. There are still many uncertainties in this field; so, more research is needed in order to better understand the pathophysiology of asthma, the early risk factors and to design new therapeutic targets and early interventions to change the natural history of the disease.

Severe Asthma-Perspectives From Adult and Pediatric Pulmonology

Both adults and children with severe asthma represent a small proportion of the asthma population; however, they consume disproportionate resources. For both groups it is important to confirm the diagnosis of severe asthma and ensure that modifiable factors such as adherence have, as far as possible, been addressed. Most children can be controlled on inhaled corticosteroids and long term oral corticosteroid use is rare, in contrast to adults where steroid related morbidity accounts for a large proportion of the costs of severe asthma. Atopic sensitization is very common in children with severe asthma as are other atopic conditions such as allergic rhinitis and hay fever which can impact on asthma control. In adults, the role of allergic driven disease, even in those with co-existent evidence of sensitization, is unclear. There is currently an exciting pipeline of novel biologicals, particularly directed at Type 2 inflammation, which afford the possibility of improved asthma control and reduced treatment side effects for people with asthma. However, not all drugs will work for all patients and accurate phenotyping is essential. In adults the terms T2 high and T2 low asthma have been coined to describe groups of patients based on the presence/absence of eosinophilic inflammation and T-helper 2 (TH₂) cytokines. Bronchoscopic studies in children with severe asthma have demonstrated that these children are predominantly eosinophilic but the cytokine patterns do not fit the T2 high paradigm suggesting other steroid resistant pathways are driving the eosinophilic inflammation. It remains to be seen whether treatments developed for adult severe asthma will be effective in children and which biomarkers will predict response.

Cytokines and Chemokines as Biomarkers of Future Asthma

Antenatal and preschool factors are key in determining the progression to pre-school wheeze and eosinophilic school age asthma. The conventional view of eosinophilic asthma is that airway inflammation is the fundamental underlying abnormality, and airway inflammation and hyper-responsiveness are secondary; in fact, these three are parallel processes. Very early structural changes, independent of inflammation and infection, are associated with early airway hyper-responsiveness and later adverse respiratory outcomes. There is a bidirectional relationship between structural airway wall changes and airway inflammation, with airway contraction per se leading to the release of growth factors, and inflammatory pathways promoting airway remodeling. Early viral infection (and increasingly being appreciated, bacterial infection) is important in wheeze outcomes. There is evidence of abnormal immune function including cytokine release before the onset of viral infections. However, viral infections may also have prolonged effects on the host immune system, and the evidence for beneficial and adverse effects of viral infection is conflicting. In older children and adults, asthmatic epithelial cells show impaired interferon responses to viral infection, but only in the presence of uncontrolled type 2 inflammation, implying these are secondary phenomena. There are also compelling data relating the innate immune system to later asthma and atopy, and animal studies suggest that the effects of a high endotoxin, microbiologically diverse environment may be modulated via the epithelial alarmin IL-33. Whereas, previously only viral infection was thought to be important, early bacterial colonization of the upper airway is coming to the fore, associated with a mixed pattern of TH1/TH2/TH17 cytokine secretion, and adverse long term outcomes. Bacterial colonization is probably a marker of a subtle immune deficiency, rather than directly causal. The airway and gut microbiome critically impacts the development of Type 2 inflammatory responses. However, Type 2 inflammatory cytokines, which are critical both to progression from pre-school wheeze to eosinophilic asthma, and sustaining the eosinophilic asthmatic state, are not implicated in the very early development of the disease. Taken together, the evidence is that the earliest cytokine and chemokine signals will come from the study of bronchial epithelial cell function and their interactions with viruses and the microbiome.

Pathophysiological Mechanisms of Asthma

The recent Lancet commission has highlighted that "asthma" should be used to describe a clinical syndrome of wheeze, breathlessness, chest tightness, and sometimes cough. The next step is to deconstruct the airway into components of fixed and variable airflow obstruction, inflammation, infection and altered cough reflex, setting the airway disease in the context of extra-pulmonary co-morbidities and social and environmental factors. The emphasis is always on delineating treatable traits, including variable airflow obstruction caused by airway smooth muscle constriction (treated with short- and long-acting β-2 agonists), eosinophilic airway inflammation (treated with inhaled corticosteroids) and chronic bacterial infection (treated with antibiotics with benefit if it is driving the disease). It is also important not to over-treat the untreatable, such as fixed airflow obstruction. These can all be determined using simple, non-invasive tests such as spirometry before and after acute administration of a bronchodilator (reversible airflow obstruction); peripheral blood eosinophil count, induced sputum, exhaled nitric oxide (airway eosinophilia); and sputum or cough swab culture (bacterial infection). Additionally, the pathophysiology of risk domains must be considered: these are risk of an asthma attack, risk of poor airway growth, and in pre-school children, risk of progression to eosinophilic school age asthma. Phenotyping the airway will allow more precise diagnosis and targeted treatment, but it is important to move to endotypes, especially in the era of increasing numbers of biologicals. Advances in -omics technology allow delineation of pathways, which will be particularly important in TH2 low eosinophilic asthma, and also pauci-inflammatory disease. It is very important to appreciate the difficulties of cluster analysis; a patient may have eosinophilic airway disease because of a steroid resistant endotype, because of non-adherence to basic treatment, and a surge in environmental allergen burden. Sophisticated -omics approaches will be reviewed in this manuscript, but currently they are not being used in clinical practice. However, even while they are being evaluated, management of the asthmas can and should be improved by considering the pathophysiologies of the different airway diseases lumped under that umbrella term, using simple, non-invasive tests which are readily available, and treating accordingly.

Airway remodeling in asthma: update on mechanisms and therapeutic approaches

PURPOSE OF REVIEW

The term 'airway remodeling' reflects changes in the type, quantity, and nature of airway wall components and their organization. The purpose of this review is to look at recent publications on airway remodeling in asthma.

RECENT FINDINGS

Animal models and in-vitro studies have confirmed the involvement of airway epithelium, airway smooth muscle (ASM), and extracellular matrix components in asthma-related airway remodeling. They report influences on proliferation of ASM cells, and how their orientation or morphology, in addition to the heterogeneity of ASM mass at different levels of airways could influence their effects. Clinical benefits have been observed following reduction of ASM following bronchial thermoplasty. Asthmatic epithelial cell transcriptome alterations were found to involve metabolism and epigenetics, beyond epithelial mesenchymal trophic unit driven by injury and repair in chronic inflammation. New ways to explore airway remodeling such as imaging or endoscopic techniques have been evaluated. Finally, new data support the role of eosinophils and mast cells in remodeling and show the influence of new asthma drugs on this process.

SUMMARY

As recently stated by an American Thoracic Society task force, we need more research on airway remodeling, its determinants and clinical relevance, and on the effects of asthma drugs on its various components.

Management of Recurrent Preschool, Doctor-Diagnosed Wheeze

Preschool wheeze occurs in half of the children before they reach 6 y of age and recurrence is also common. Recurrent preschool wheeze is classified as either typical or atypical. For typical recurrent preschool wheeze, the diagnoses are either asthma or bronchiolitis/bronchitis. Responsiveness to a properly administered bronchodilator confirms asthma, atopic or otherwise. All atypical preschool wheeze should be referred to pediatric respirologist for assessment. Lung function test by impulse oscillometry (IOS) before and after bronchodilator is helpful to confirm airway hyperresponsiveness, an essential feature of asthma. Assessment of atopy is important by either skin prick test or serum IgE level. Treatment of acute wheeze includes standard supportive care, bronchodilator for those diagnosed with asthma and hypertonic saline for those diagnosed as having acute bronchiolitis. Other treatments included nebulized adrenaline for acute bronchiolitis and systemic steroids for asthma. For those with significant respiratory distress, continuous positive airway pressure (CPAP) or heated humidified high flow should be considered. Daily or intermittent inhaled corticosteroid or intermittent montelukast would reduce asthma exacerbation rate. A significant proportion of preschool wheeze persists till school age. An early diagnosis of asthma would be important to allow early optimal management.

Translating Asthma: Dissecting the Role of Metabolomics, Genomics and Personalized Medicine

The management of asthma has largely stagnated over the last 25 years, but we are at the dawning of a new age wherein -omics technology can help us manage the disease objectively and rationally. Even in this new scientific age, getting the basics of asthma management right remains essential. The new technologies which can be applied to multiple biological samples include genomics (study of the genome), transcriptomics (gene transcription), lipidomics, proteomics and metabolomics (lipids, proteins and metabolites, respectively) and breathomics, using exhaled breath as a source of biomarkers, which is of particular interest in view of its non-invasive nature in pediatrics. Important applications will include the diagnosis of airways disease, including its components; the pathways driving airway pathology; monitoring the response to treatment; and measuring future risk (asthma attacks, poor lung growth trajectory). With the advent of a wide range of novel biologicals to treat asthma, -omics technology to personalize therapy will be especially important. The U-BIOPRED (Europe) and SARP (USA) groups have been most active in this field, especially using bronchoscopically obtained samples to perform cluster analyses to define new asthma endotypes. However, stability over time and consistency between investigators is imperfect. This is perhaps unsurprising; results of biomarker studies in asthma will be a composite of the underlying disease, the (variable) effects of adverse drivers such as allergen exposure and pollution, the effects of treatment, and the effects of adherence or otherwise to treatment. Ultimately, the aim should be an exhaled breath based tool with a rapid result that can be used as a routine in the clinic. However, at the moment, there are as yet no clinical applications in children of -omics technology.