Phenotype-specific treatment of difficult asthma in children

Asthma clustering methods: a literature-informed application to the children's health study data

OBJECTIVE

The heterogeneity of asthma has inspired widespread application of statistical clustering algorithms to a variety of datasets for identification of potentially clinically meaningful phenotypes. There has not been a standardized data analysis approach for asthma clustering, which can affect reproducibility and clinical translation of results. Our objective was to identify common and effective data analysis practices in the asthma clustering literature and apply them to data from a Southern California population-based cohort of schoolchildren with asthma.

METHODS

As of January 1, 2020, we reviewed key statistical elements of 77 asthma clustering studies. Guided by the literature, we used 12 input variables and three clustering methods (hierarchical clustering, k-medoids, and latent class analysis) to identify clusters in 598 schoolchildren with asthma from the Southern California Children's Health Study (CHS).

RESULTS

Clusters of children identified by latent class analysis were characterized by exhaled nitric oxide, FEV₁/FVC, FEV₁ percent predicted, asthma control and allergy score; and were predictive of control at two year follow up. Clusters from the other two methods were less clinically remarkable, primarily differentiated by sex and race/ethnicity and less predictive of asthma control over time.

CONCLUSION

Upon review of the asthma phenotyping literature, common approaches of data clustering emerged. When applying these elements to the Children's Health Study data, latent class analysis clusters-represented by exhaled nitric oxide and spirometry measures-had clinical relevance over time.

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.

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

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

Severe asthma in children

Severe asthma in children is characterized by sustained symptoms despite treatment with high doses of inhaled corticosteroids or oral corticosteroids. Children with severe asthma may fall into 2 categories, difficult-to-treat asthma or severe therapy-resistant asthma. Difficult-to-treat asthma is defined as poor control due to an incorrect diagnosis or comorbidities, or poor adherence due to adverse psychological or environmental factors. In contrast, treatment resistant is defined as difficult asthma despite management of these factors. It is increasingly recognized that severe asthma is a highly heterogeneous disorder associated with a number of clinical and inflammatory phenotypes that have been described in children with severe asthma. Guideline-based drug therapy of severe childhood asthma is based primarily on extrapolated data from adult studies. The recommendation is that children with severe asthma be treated with higher-dose inhaled or oral corticosteroids combined with long-acting β-agonists and other add-on therapies, such as antileukotrienes and methylxanthines. It is important to identify and address the influences that make asthma difficult to control, including reviewing the diagnosis and removing causal or aggravating factors. Better definition of the phenotypes and better targeting of therapy based upon individual patient phenotypes is likely to improve asthma treatment in the future.

Evaluation of functional, autonomic and inflammatory outcomes in children with asthma

Asthma is common in childhood. This respiratory disease is characterized by persistent inflammation of the airways even when the child is not in the throes of an attack. Chronic inflammation is caused by an imbalance between pro-inflammatory and anti-inflammatory mechanisms as well as autonomic dysfunction, which plays an important role in the pathogenesis and control of this condition. The impact of these physiopathological aspects leads to inactivity and a sedentary lifestyle, which exerts an influence on functional capacity and control of the disease. The main objective of non-pharmacological therapy is the clinical control of asthma and the minimization of airway obstruction and hyperinflation during an attack. These factors can be controlled with noninvasive ventilation. The aim or the present review was to describe important neural, inflammatory and functional mechanisms that affect children with asthma.

Difficult-to-treat asthma in childhood

Asthma continues to be one of the greatest burdens to healthcare resources throughout the developed world. In most cases, good symptom control can be achieved with low-dose inhaled corticosteroids, and can be cared for in the primary and secondary healthcare systems. However, there is a group in whom control is not achieved despite high-dose inhaled corticosteroids and maximal add-on therapies; these are children with problematic severe asthma that should be referred to a specialist team for further investigation and management. In this review we aimed to provide an evidence-based guide for pediatricians providing care for children with asthma in secondary healthcare settings. The review focuses on a proposed investigation and management strategy for children aged between 6 and 16 years with problematic severe asthma, and is supported as far as possible by evidence from the literature. We first address recent advances in nomenclature and then discuss our proposed course of investigation and management of these children. Distinction of children with true, severe, therapy-resistant asthma from those with asthma that is difficult to treat because of unaddressed underlying modifiable factors is critical and is discussed in detail.

Increased chitinase expression and fungal-specific antibodies in the bronchoalveolar lavage fluid of asthmatic children

BACKGROUND

Increasing evidence highlights the contribution of chitinases and fungal infection to the development of asthma.

OBJECTIVE

The purpose of this study was to characterize chitinase expression and serological markers of fungal infection in children with severe asthma.

METHODS

Bronchoalveolar lavage fluid (BALF) was collected from children undergoing clinically indicated flexible bronchoscopy. A diagnosis of asthma was confirmed by pulmonary function testing. BALF was tested for chitinase activity and YKL-40 (an enzymatically inactive chitinase) concentrations. Specimens were cultured for fungal organisms and tested for cryptococcal antigen by ELISA. IgG and IgA reactivity to whole extract fungal (Aspergillus fumigatus, Alternaria alternata, Cryptococcus neoformans and Candida albicans) proteins were determined by immunoblot assay.

RESULTS

Among the 37 patients studied, 30 were asthmatic and 7 were non-asthmatic. Asthmatics exhibited elevated serum IgE levels (median: 748 IU/mL, IQR: 219-1765 IU/mL). Chitinase activity was greater in the BALF of asthmatics (mean, 0.85 ± 1.2 U/mL) compared with non-asthmatics (mean: 0.23 ± 0.21 U/mL, P = 0.012). Likewise YKL-40 concentrations were higher in the BALF of asthmatics and correlated with chitinase activity. There was a trend towards increased fungal-specific IgG in the BALF of asthmatics compared with non-asthmatics and for C. albicans this difference reached statistical significance. IgA reactivity to C. neoformans and A. fumigatus was greater in the BALF of asthmatics compared with non-asthmatics.

CONCLUSIONS AND CLINICAL RELEVANCE

Compared with non-asthmatics, asthmatic children exhibited increased chitinase activity and increased YKL-40 levels in BALF. Increased IgG and IgA reactivity to fungal proteins in the BALF of asthmatics may reflect a local response to fungal infection. Our findings are consistent with and suggest a role for chitinases in asthma pathogenesis among Bronx children and provide serological evidence of an association between fungal infection and severe asthma.

Rapamycin decreases airway remodeling and hyperreactivity in a transgenic model of noninflammatory lung disease

Airway hyperreactivity (AHR) and remodeling are cardinal features of asthma and chronic obstructive pulmonary disease. New therapeutic targets are needed as some patients are refractory to current therapies and develop progressive airway remodeling and worsening AHR. The mammalian target of rapamycin (mTOR) is a key regulator of cellular proliferation and survival. Treatment with the mTOR inhibitor rapamycin inhibits inflammation and AHR in allergic asthma models, but it is unclear if rapamycin can directly inhibit airway remodeling and AHR, or whether its therapeutic effects are entirely mediated through immunosuppression. To address this question, we utilized transforming growth factor-α (TGF-α) transgenic mice null for the transcription factor early growth response-1 (Egr-1) (TGF-α Tg/Egr-1(ko/ko) mice). These mice develop airway smooth muscle thickening and AHR in the absence of altered lung inflammation, as previously reported. In this study, TGF-α Tg/Egr-1(ko/ko) mice lost body weight and developed severe AHR after 3 wk of lung-specific TGF-α induction. Rapamycin treatment prevented body weight loss, airway wall thickening, abnormal lung mechanics, and increases in airway resistance to methacholine after 3 wk of TGF-α induction. Increases in tissue damping and airway elastance were also attenuated in transgenic mice treated with rapamycin. TGF-α/Egr-1(ko/ko) mice on doxycycline for 8 wk developed severe airway remodeling. Immunostaining for α-smooth muscle actin and morphometric analysis showed that rapamycin treatment prevented airway smooth muscle thickening around small airways. Pentachrome staining, assessments of lung collagen and fibronectin mRNA levels, indicated that rapamycin also attenuated fibrotic pathways induced by TGF-α expression for 8 wk. Thus rapamycin reduced airway remodeling and AHR, demonstrating an important role for mTOR signaling in TGF-α-induced/EGF receptor-mediated reactive airway disease.

Risk factors for current wheezing and its phenotypes among elementary school children

BACKGROUND

Accumulating evidence suggests, asthma includes many phenotypes with varying clinical and prognostic features. Epidemiological surveys documented a number of environmental risk factors for the development of asthma and interestingly these differ between and within countries, suggesting that the differences may be related with the different distribution of asthma phenotypes. This study aimed to investigate risk factors of current wheezing (CW) and different wheezing phenotypes in elementary school children.

METHODS

Six thousand nine hundred sixty-three 9- to 11-year-old children of a previous multicenter survey where the methodology of the International Study of Asthma and Allergies in Childhood (ISAAC) Phase-II was used were analyzed. Wheezing phenotypes were defined as wheezing with rhinitis (RW), wheezing with rhinoconjunctivitis (RCW), atopic wheezing (AW), non-atopic wheezing (NAW), and frequent wheezing (FW) (≥4/year wheezing episodes).

RESULTS

The prevalence of CW was 15.8% and among these, 22.4%, 67.3%, 45.9%, 20.5%, and 79.5% were classified as FW, RW, RCW, AW, and NAW, respectively. History of parental asthma/allergic rhinitis, coexistence of other allergic diseases, presence of mold and dampness in the house lived during the first year of life and maternal smoking in pregnancy were found to be risk factors for most phenotypes (odds ratio (OR) ranged from 1.43 to 3.56). Number of household in the last year (OR = 1.14), prematurity (OR = 2.08), and duration of breastfeeding (OR = 1.02) per additional month were found to be risk factor for FW, AW, and RCW, respectively.

CONCLUSION

Beside common risk factors for the development of asthma and its phenotypes, certain risk factors appeared to play a role in the development of phenotypic characteristics of asthma. These findings support our hypothesis that each phenotype has not only different clinical characteristics but also has different roots.

Corticosteroid responsiveness and clinical characteristics in childhood difficult asthma

This study describes the clinical characteristics and corticosteroid responsiveness of children with difficult asthma (DA). We hypothesised that complete corticosteroid responsiveness (defined as improved symptoms, normal spirometry, normal exhaled nitric oxide fraction (F(eNO)) and no bronchodilator responsiveness (BDR <12%)) is uncommon in paediatric DA. We report on 102 children, mean+/-sd age 11.6+/-2.8 yrs, with DA in a cross-sectional study. 89 children underwent spirometry, BDR and F(eNO) before and after 2 weeks of systemic corticosteroids (corticosteroid response study). Bronchoscopy was performed after the corticosteroid trial. Of the 102 patients in the cross-sectional study, 88 (86%) were atopic, 60 (59%) were male and 52 (51%) had additional or alternative diagnoses. Out of the 81 patients in the corticosteroid response study, nine (11%) were complete responders. Of the 75 patients with symptom data available, 37 (49%) responded symptomatically, which was less likely if there were smokers in the home (OR 0.31, 95% CI 0.02-0.82). Of the 75 patients with available spirometry data, 35 (46%) had normal spirometry, with associations being BAL eosinophilia (OR 5.43, 95% CI 1.13-26.07) and high baseline forced expiratory volume in 1 s (FEV(1)) (OR 1.08, 95% CI 1.02-1.12). Of these 75 patients, BDR data were available in 64, of whom 36 (56%) had <12% BDR. F(eNO) data was available in 70 patients, of whom 53 (75%) had normal F(eNO). Airflow limitation data was available in 75 patients, of whom 17 (26%) had persistent airflow limitation, which was associated with low baseline FEV(1) (OR 0.93, 95% CI 0.90-0.97). Only 11% of DA children exhibited complete corticosteroid responsiveness. The rarity of complete corticosteroid responsiveness suggests alternative therapies are needed for children with DA.

Gene-environment interactions in asthma

Asthma is a complex disease, and its incidence is determined by an intricate interplay of genetic and environmental factors. The identification of novel genes for asthma suggests that many genes with small effects rather than few genes with strong effects contribute to the development of asthma. These genetic effects may in part differ with respect to a subject's environmental exposures, although some genes may also exert their effect independently of the environment. Whereas the geneticist uses highly advanced, rapid, comprehensive technologies to assess even subtle changes in the human genome, the researcher interested in environmental exposures is often confronted with crude information obtained from questionnaires or interviews. There is thus substantial need to develop better tools for individual exposure assessment in all relevant environmental fields. Despite these limitations, a number of important gene-environment interactions have been identified. These interactions point to the biology of environmental exposures as the involved genetic variation is suggestive of certain underlying mechanisms. Furthermore, the identification of subjects who are particularly susceptible to environmental hazards through genetic analyses helps to estimate better the strength of effect of environmental exposures. Finally, the analysis of gene-environment interactions may result in a reconciliation of seemingly contradictory findings from studies not taking environmental exposures into account.

Severe exacerbations in children with mild asthma: characterizing a pediatric phenotype

BACKGROUND

NHLBI guidelines classify asthma in children as intermittent, mild persistent, moderate persistent, and severe persistent asthma based on baseline symptoms and pulmonary function. However, this may not capture the spectrum of asthma in children, since even mild baseline disease can have significant effects on quality of life. Our objective was to describe a population of children with mild asthma admitted to the ICU with severe exacerbations.

METHODS

We examined data from all children with asthma who were admitted to the ICU with an acute exacerbation between April 1997, and December 2006. Children were defined as having mild asthma if their disease was classified as intermittent or mild persistent according to NHLBI criteria.

RESULTS

Of the 298 children admitted to the ICU with asthma, 164 (55%) were classified as having mild baseline asthma. Compared with children with more severe baseline asthma, mild asthmatic children were younger and less likely to have been previously admitted to the hospital for asthma. Other demographics, including admission severity of illness, gender, and prevalence of overweight, were similar in the two groups. There were no differences between the groups in ICU length of stay, hospital length of stay or types of therapies received. Thirteen children with mild asthma were intubated, although less frequently than those with more severe disease.

CONCLUSIONS

Children with mild asthma have severe exacerbations. This suggests that chronic asthma severity does not necessarily predict asthma phenotypes during acute exacerbations.

Azithromycin may reduce cholestasis in primary sclerosing cholangitis: a case report and serendipitous observation

The newer macrolides have been shown to exert additional anti-inflammatory effects. We report the possible effect of azithromycin on primary sclerosing cholangitis in a patient treated with the drug for severe asthma. A 45-year-old woman with Crohn?s disease and primary sclerosing cholangitis, also suffering from severe asthma, was treated with azithromycin 500 mg OD for 3 consecutive days a week because of the clinical suspicion of bronchiectasis and the severity of her asthma. When the therapy was discontinued, her urine again became darker, pruritus reappeared with the usual severity and laboratory parameters, evaluated after 6 weeks without azithromycin, also worsened. For these reasons macrolide treatment was re-established. Cholestasis-related symptoms and the dark colour of the urine were again reduced 6 weeks later and laboratory parameters were again reversed. We are therefore tempted to speculate that azithromycin may have an effect on primary sclerosing cholangitis on the basis of its anti-inflammatory properties.

Diagnosis and treatment of asthma in childhood: a PRACTALL consensus report

Asthma is the leading chronic disease among children in most industrialized countries. However, the evidence base on specific aspects of pediatric asthma, including therapeutic strategies, is limited and no recent international guidelines have focused exclusively on pediatric asthma. As a result, the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma and Immunology nominated expert teams to find a consensus to serve as a guideline for clinical practice in Europe as well as in North America. This consensus report recommends strategies that include pharmacological treatment, allergen and trigger avoidance and asthma education. The report is part of the PRACTALL initiative, which is endorsed by both academies.

Exhaled nitric oxide after a single dose of intramuscular triamcinolone in children with difficult to control asthma

In a previous study, we reported that intramuscular (IM) triamcinolone improves symptoms in children with difficult asthma. In 2005, we revised our difficult asthma protocol to include assessment of airway inflammation, both directly using sputum induction and indirectly by measurement of exhaled nitric oxide (eNO). In this retrospective review, we aimed to describe (i) the changes in eNO and symptoms after a single 60 mg dose of IM triamcinolone and (ii) the changes in inflammatory markers in the subgroup with non-eosinophilic asthma (i.e., an induced sputum eosinophil differential count <2.0%). Seven children received IM triamcinolone during the study period. In all children, symptom scores fell in the week following the IM injection (P < 0.01 vs. the pre-treatment week), and remained reduced for up to 6 weeks. eNO also fell within a week after IM therapy (P < 0.01), and remained reduced for up to 4 weeks. Non-eosinophilic asthma was definitively identified in three children, and in this group, eNO and symptoms fell after the IM injection. We conclude that IM triamcinolone therapy reduces both eNO and symptoms for up to 4 weeks in children with difficult asthma. Our data provide preliminary evidence that IM triamcinolone is an effective anti-inflammatory therapy in children with induced sputum non-eosinophilic asthma.

Difficult to control asthma in children

PURPOSE OF REVIEW

The management of children with difficult asthma requires a systematic approach. These children are prescribed high doses of inhaled or oral corticosteroids and a balance must be struck between therapeutic efficacy and side effects. It is important to ensure the diagnosis is correct and that the reasons for poor control in a given child are characterized so that treatment can be targeted for maximal effect.

RECENT FINDINGS

Recent data have demonstrated the correlation between invasive and noninvasive measurement of airway eosinophils. Noninvasive markers of inflammation can be used to determine phenotype and there is increasing evidence on the utility of repeated measures to monitor control and treatment effects. Side effects of high-dose corticosteroids remain a concern. The emergence of new therapies may be of benefit. These are often expensive, however, and have the potential for major side effects. Adherence remains a significant obstacle to the effective management of difficult asthma.

SUMMARY

Children with difficult asthma are a heterogeneous group. Characterization and monitoring of these children can be enhanced by measurements of noninvasive markers of inflammation. Further evaluation of new and phenotype-specific treatments for children with difficult asthma need to be evaluated in prospective randomized controlled trials.

Airway eosinophilia in children with severe asthma: predictive values of noninvasive tests

RATIONALE

Children with severe asthma experience persistent symptoms despite maximal conventional treatment. Fraction of exhaled nitric oxide (Fe(NO)) and sputum eosinophils are used as markers of airway inflammation to guide treatment with steroids, but no data are available on how reliable they are in predicting airway eosinophilia assessed bronchoscopically in these children.

OBJECTIVES

To determine how Fe(NO) and sputum eosinophils predict airway eosinophilia measured in both bronchoalveolar lavage (BAL) and endobronchial biopsy.

METHODS

Twenty-seven children with moderate to severe persistent asthma attempted measurement of Fe(NO) and sputum eosinophils, followed by bronchoscopy, BAL, and endobronchial biopsy within 24 h.

MAIN RESULTS

Significant correlations were found between eosinophils in sputum and both BAL eosinophils (n = 20, r = 0.45, p = 0.045) and Fe(NO) (n = 23, r = 0.42, p = 0.049). The relationship between Fe(NO) and BAL eosinophils was also significant with a stronger correlation (n = 24, r = 0.54, p = 0.006). The positive predictive value (PPV) for increased sputum eosinophil percentage (> 2.5%) to detect elevated eosinophils in BAL (> 1.19%) was 75%; the negative predictive value (NPV) was 63%. All patients with both increased sputum eosinophils and an elevated Fe(NO) value (> 23 ppb) had elevated eosinophils in BAL (PPV, 100%); the NPV of these two markers was 65%. Eight of nine patients without any sputum eosinophils had normal subepithelial eosinophil numbers (< 1.2%; NPV, 89%). However, the PPV of any sputum eosinophils for increased subepithelial eosinophilia was only 36.4%.

CONCLUSIONS

There was moderate agreement between both Fe(NO) and sputum eosinophils and BAL eosinophils. There was good NPV, but only poor PPV for these markers for mucosal eosinophilia.

Anti-IgE therapy in allergic disease

PURPOSE OF REVIEW

Recombinant monoclonal humanized anti-IgE has put forward a fundamentally new concept for the control of allergic disorders. This review will present recent data from clinical studies with anti-IgE in asthma, allergic rhinitis, and food allergy and will examine the place of anti-IgE among current therapeutic options for the treatment of asthma.

RECENT FINDINGS

Therapy with anti-IgE depresses circulating free IgE to the limits of detection, inhibits early- and late-phase responses to allergens, suppresses inflammation and improves the control of allergic diseases. In moderate to severe asthma it results in fewer exacerbations and a lower requirement for both corticosteroids and beta-agonists. IgE appears to be an important regulator of high-affinity Fc receptors (FcepsilonRI) and, in the mouse, to enhance mast cell survival and activation. IgE receptors have been found on diverse inflammatory cells. Anti-IgE reduces the expression of FcepsilonRI on inflammatory cells. Current work has documented a marked decrease in tissue eosinophils, lymphocytes, and interleukin-4-positive cells by anti-IgE treatment and has provided insight into the mechanisms underlying improved control of asthma.

SUMMARY

Clinical studies with anti-IgE have promoted and will continue to advance the understanding of IgE-mediated disease mechanisms. They have documented its efficacy in the treatment of allergic diseases, but much remains to be learned about the most effective clinical strategies and the selection of patients for therapy.