Systemic Corticosteroid Responses in Children with Severe Asthma: Phenotypic and Endotypic Features

Lung function, airway and peripheral basophils and eosinophils are associated with molecular pharmacogenomic endotypes of steroid response in severe asthma

INTRODUCTION

Asthma is a complex disease with heterogeneous expression/severity. There is growing interest in defining asthma endotypes consistently associated with different responses to therapy, focusing on type 2 inflammation (Th2) as a key pathological mechanism. Current asthma endotypes are defined primarily by clinical/laboratory criteria. Each endotype is likely characterised by distinct molecular mechanisms that identify optimal therapies.

METHODS

We applied unsupervised (without a priori clinical criteria) principal component analysis on sputum airway cells RNA-sequencing transcriptomic data from 19 asthmatics from the Severe Asthma Research Program at baseline and 6-8 weeks follow-up after a 40 mg dose of intramuscular corticosteroids. We investigated principal components PC1, PC3 for association with 55 clinical variables.

RESULTS

PC3 was associated with baseline Th2 clinical features including blood (rank-sum p=0.0082) and airway (rank-sum p=0.0024) eosinophilia, FEV₁ change (Kendall tau-b R=-0.333 (-0.592 to -0.012)) and follow-up FEV₁ albuterol response (Kendall tau-b R=0.392 (0.079 to 0.634)). PC1 with blood basophlia (rank-sum p=0.0191). The top 5% genes contributing to PC1, PC3 were enriched for distinct immune system/inflammation ontologies suggesting distinct subject-specific clusters of transcriptomic response to corticosteroids. PC3 association with FEV₁ change was reproduced in silico in a comparable independent 14-subject (baseline, 8 weeks after daily inhaled corticosteroids (ICS)) airway epithelial cells microRNAome dataset.

CONCLUSIONS

Transcriptomic PCs from this unsupervised methodology define molecular pharmacogenomic endotypes that may yield novel biology underlying different subject-specific responses to corticosteroid therapy in asthma, and optimal personalised asthma care. Top contributing genes to these PCs may suggest new therapeutic targets.

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.

Understanding the immunology of asthma: Pathophysiology, biomarkers, and treatments for asthma endotypes

Asthma is a common disease in paediatrics and adults with a significant morbidity, mortality, and financial burden worldwide. Asthma is now recognized as a heterogeneous disease and emerging clinical and laboratory research has elucidated understanding of asthma's underlying immunology. The future of asthma is classifying asthma by endotype through connecting discernible characteristics with immunological mechanisms. This comprehensive review of the immunology of asthma details the currently known pathophysiology and clinical practice biomarkers in addition to forefront biologic and targeted therapies for all of the asthma endotypes. By understanding the immunology of asthma, practitioners will be able to diagnose patients by asthma endotype and provide personalized, biomarker-driven treatments to effectively control patients' 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.

Latent Class Analysis of School-Age Children at Risk for Asthma Exacerbation

BACKGROUND

Factors responsible for asthma exacerbations in children are complex and may differ from those that drive asthma severity.

OBJECTIVE

To identify latent classes of children at risk for asthma exacerbation and determine whether latent class assignment is useful in the prediction of future exacerbation.

METHODS

Latent class analysis was performed on 513 children aged 6 to 17 years at risk for asthma exacerbation, with 31 variables encompassing demographics, medical history, treatment, symptoms, lung function, sensitization, and type 2 inflammation. Primary and secondary outcomes included exacerbation occurrence by 12 months and time to first exacerbation, respectively.

RESULTS

Four latent classes were identified with differing demographic features, sensitization and type 2 inflammatory markers, prior exacerbation severity and health care utilization, and lung function. Exacerbations occurred in 22.4% of class 1 ("lesser sensitization with normal lung function"), 27.9% of class 2 ("lesser sensitization with prior severe exacerbation and normal lung function"), 45.3% of class 3 ("multiple sensitization with reversible airflow limitation"), and 64.3% of class 4 ("multiple sensitization with partially reversible airflow limitation") (P < .001). Time to exacerbation also followed similar trends and was shortest in the latent classes with multiple sensitization and airflow limitation (P < .001). Outcomes were driven largely by children with exacerbation-prone asthma (defined as ≥3 exacerbations in the prior year), who were present in each class but most strongly represented in classes 3 and 4.

CONCLUSIONS

Children at risk for asthma exacerbation are a heterogeneous group. Sensitization, prior exacerbation severity, and lung function variables may be particularly useful in identifying children at greatest risk for future exacerbation.

Precision medicine in childhood asthma

PURPOSE OF REVIEW

Childhood asthma is a heterogeneous disease and many children have uncontrolled disease. Therefore an individualized approach is needed to improve asthma outcomes in children. Precision medicine using clinical characteristics, biomarkers, and the rapidly involving field of genomics and pharmacogenomics aims to achieve asthma control and reduce future risks with less side-effects in individual children with asthma.

RECENT FINDINGS

It is not yet possible to select treatment options on clinical characteristics. Novel monoclonal antibodies are efficacious in patients with severe, eosinophilic asthma. Reduced lung function growth and early decline is a prevalent finding in children with persistent asthma. Pharmacogenetic studies have identified children at risk for cortisol suppression when using inhaled corticosteroids.

SUMMARY

Clinical characteristics and simple biomarkers like eosinophils, IgE, and the fraction of exhaled nitric oxide may be used in clinical practice for a basic precision medicine approach, deciding which children will have the best chance to respond to inhaled corticosteroids and to the biologicals omalizumab and mepolizumab.Further application of pharmacogenomics and breathomics needs additional studies before they can be applied as tools for precision medicine in individual children with asthma.

Asthma and Corticosteroid Responses in Childhood and Adult Asthma

Corticosteroids are the most effective treatment for asthma; inhaled corticosteroids (ICSs) are the first-line treatment for children and adults with persistent symptoms. ICSs are associated with significant improvements in lung function. The anti-inflammatory effects of corticosteroids are mediated by both genomic and nongenomic factors. Variation in the response to corticosteroids has been observed. Patient characteristics, biomarkers, and genetic features may be used to predict response to ICSs. The existence of multiple mechanisms underlying glucocorticoid insensitivity raises the possibility that this might indeed reflect different diseases with a common phenotype.

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.

Development and initial validation of the Asthma Severity Scoring System (ASSESS)

BACKGROUND

Tools for quantification of asthma severity are limited.

OBJECTIVE

We sought to develop a continuous measure of asthma severity, the Asthma Severity Scoring System (ASSESS), for adolescents and adults, incorporating domains of asthma control, lung function, medications, and exacerbations.

METHODS

Baseline and 36-month longitudinal data from participants in phase 3 of the Severe Asthma Research Program (NCT01606826) were used. Scale properties, responsiveness, and a minimally important difference were determined. External replication was performed in participants enrolled in the Severe Asthma Research Program phase 1/2. The utility of ASSESS for detecting treatment response was explored in participants undergoing corticosteroid responsiveness testing with intramuscular triamcinolone and participants receiving biologics.

RESULTS

ASSESS scores ranged from 0 to 20 (8.78 ± 3.9; greater scores reflect worse severity) and differed among 5 phenotypic groups. Measurement properties were acceptable. ASSESS was responsive to changes in quality of life with a minimally important difference of 2, with good specificity for outcomes of asthma improvement and worsening but poor sensitivity. Replication analyses yielded similar results, with a 2-point decrease (improvement) associated with improvements in quality of life. Participants with a 2-point or greater decrease (improvement) in ASSESS scores also had greater improvement in lung function and asthma control after triamcinolone, but these differences were limited to phenotypic clusters 3, 4, and 5. Participants treated with biologics also had a 2-point or greater decrease (improvement) in ASSESS scores overall.

CONCLUSIONS

The ASSESS tool is an objective measure that might be useful in epidemiologic and clinical research studies for quantification of treatment response in individual patients and phenotypic groups. However, validation studies are warranted.

Opening the Window of Immune Opportunity: Treating Childhood Asthma

Asthma is an increasingly common childhood disease and although most patients can control their symptoms with medication, a proportion experience life-threatening symptoms. The advent of novel biologic therapies represents a giant leap forward for asthma treatment, but efficacy is rarely tested in children. Recent mechanistic work in mice suggests that early life is a key period for immune development and, therefore, allergen sensitization. Although children with severe asthma experience significant comorbidities and are at increased risk for serious diseases such as chronic obstructive pulmonary disease as adults, no specific investigation into tailored treatment for young children with severe asthma exists. Here, we propose how new information regarding early life immunity could be used to inform modified treatments for children.

Th1 cytokines TNF-α and IFN-γ promote corticosteroid resistance in developing human airway smooth muscle

Corticosteroids (CSs) are commonly used to manage wheezing and asthma in pediatric populations. Although corticosteroids are effective in alleviating airway diseases, some children with more moderate-severe asthma phenotypes show CS resistance and exhibit significant airflow obstruction, persistent inflammation, and more frequent exacerbations. Previous studies have demonstrated that Th1 cytokines, such as TNF-α and IFN-γ, promote CS resistance in adult human airway smooth muscle (ASM). In the present study, using a human fetal ASM cell model, we tested the hypothesis that TNF-α/IFN-γ induces CS resistance. In contrast to TNF-α or IFN-γ alone, the combination of TNF-α/IFN-γ blunted the ability of fluticasone propionate (FP) to reduce expression of the chemokines CCL5 and CXCL10 despite expression of key anti-inflammatory glucocorticoid receptor target genes being largely unaffected by TNF-α/IFN-γ. Expression of the NF-κB subunit p65 and phosphorylation of Stat1 were elevated in cells treated with TNF-α/IFN-γ, an effect that remained in the presence of FP. siRNA knockdown studies demonstrated the effects of TNF-α/IFN-γ on increased p65 are mediated by Stat1, a transcription factor activated by IFN-γ. Expression of TNFAIP3, a negative regulator of NF-κB activity, was not altered by TNF-α/IFN-γ. However, the effects of TNF-α/IFN-γ were partially reduced by overexpression of TNFAIP3 but did not influence p65 expression. Together, these data suggest that IFN-γ augments the effects of TNF-α on chemokines by enhancing expression of key inflammatory pathways in the presence of CS. Interactions between TNF-α- and IFN-γ-mediated pathways may promote inflammation in asthmatic children resistant to CSs.

The Journal of Allergy and Clinical Immunology: In Practice 2017 Year in Review

An impressive number of clinically impactful studies and reviews were published in The Journal of Allergy and Clinical Immunology: In Practice in 2017. As a service to our readers, the editors provide this Year in Review article to highlight and contextualize the advances published over the past year. We include information from articles on asthma, allergic rhinitis, rhinosinusitis, immunotherapy, atopic dermatitis, contact dermatitis, food allergy, anaphylaxis, drug hypersensitivity, urticarial/angioedema, eosinophilic disorders, and immunodeficiency. Within each topic, epidemiologic findings are presented, relevant aspects of prevention are described, and diagnostic and therapeutic advances are enumerated. Treatments discussed include behavioral therapy, allergen avoidance therapy, positive and negative effects of pharmacologic therapy, and various forms of immunologic and desensitization management. We hope this review will help readers consolidate and use this extensive and practical knowledge for the benefit of patients.

Tissue Remodeling in Chronic Eosinophilic Esophageal Inflammation: Parallels in Asthma and Therapeutic Perspectives

Chronic eosinophilic inflammation is associated with tissue remodeling and fibrosis in a number of chronic T-helper 2 (Th2)-mediated diseases including eosinophilic esophagitis (EoE) and asthma. Chronic inflammation results in dysregulated tissue healing, leading to fibrosis and end organ dysfunction, manifesting clinically as irreversible airway obstruction in asthma and as esophageal rigidity, strictures, narrowing, dysmotility, dysphagia, and food impactions in EoE. Current therapies for EoE and asthma center on reducing inflammation-driven tissue remodeling and fibrosis with corticosteroids, coupled with symptomatic control and allergen avoidance. Additional control of Th2 inflammation can be achieved in select asthma patients with biologic therapies such as anti-IL-5 and anti-IL-13 antibodies, which have also been trialed in EoE. Recent molecular analysis suggests an emerging role for structural cell dysfunction, either inherited or acquired, in the pathogenesis and progression of EoE and asthma tissue remodeling. In addition, new data suggest that inflammation-independent end organ rigidity can alter structural cell function. Herein, we review emerging data and concepts for the pathogenesis of tissue remodeling and fibrosis primarily in EoE and relevant pathogenetic parallels in asthma, focusing additionally on emerging disease-specific therapies and the ability of these therapies to reduce tissue remodeling in subsets of patients.

Changing Paradigms in the Treatment of Severe Asthma: The Role of Biologic Therapies

Cytokine antagonists are monoclonal antibodies that offer new treatment options for refractory asthma but will also increase complexity because they are effective only for patients with certain asthma subtypes that remain to be more clearly defined. The clinical and inflammatory heterogeneity within refractory asthma makes it difficult to manage the disease and to determine which, if any, biologic therapy is suitable for a specific patient. The purpose of this article is to provide a data-driven discussion to clarify the use of biologic therapies in patients with refractory asthma. We first discuss the epidemiology and pathophysiology of refractory asthma. We then interpret current evidence for biomarkers of eosinophilic or type 2-high asthma so that clinicians can determine potential treatments for patients based on knowledge of their effectiveness in specific asthma phenotypes. We then assess clinical data on the efficacy, safety, and mechanisms of action of approved and pipeline biologic therapies. We conclude by discussing the potential of phenotyping or endotyping refractory asthma and how biologic therapies can play a role in treating patients with refractory asthma.