Absence of airway inflammation in a large proportion of adolescents with asthma

Gut microbiome signature and nasal lavage inflammatory markers in young people with asthma

Background

Asthma is a complex disease and a severe global public health problem resulting from interactions between genetic background and environmental exposures. It has been suggested that gut microbiota may be related to asthma development; however, such relationships needs further investigation.

Objective

This study aimed to characterize the gut microbiota as well as the nasal lavage cytokine profile of asthmatic and nonasthmatic individuals.

Methods

Stool and nasal lavage samples were collected from 29 children and adolescents with type 2 asthma and 28 children without asthma in Brazil. Amplicon sequencing of the stool bacterial V4 region of the 16S rRNA gene was performed using Illumina MiSeq. Microbiota analysis was performed by QIIME 2 and PICRUSt2. Type 2 asthma phenotype was characterized by high sputum eosinophil counts and positive skin prick tests for house dust mite, cockroach, and/or cat or dog dander. The nasal immune marker profile was assessed using a customized multiplex panel.

Results

Stool microbiota differed significantly between asthmatic and nonasthmatic participants (P = .001). Bacteroides was more abundant in participants with asthma (P < .05), while Prevotella was more abundant in nonasthmatic individuals (P < .05). In people with asthma, the relative abundance of Bacteroides correlated with IL-4 concentration in nasal lavage samples. Inference of microbiota functional capacity identified differential fatty acid biosynthesis in asthmatic compared to nonasthmatic subjects.

Conclusion

The stool microbiota differed between asthmatic and nonasthmatic young people in Brazil. Asthma was associated with higher Bacteroides levels, which correlated with nasal IL-4 concentration.

Differential airway resistome and its correlations with clinical characteristics in Haemophilus- or Pseudomonas-predominant microbial subtypes of bronchiectasis

The prevalence and clinical correlates of antibiotic resistance genes (ARGs) in bronchiectasis are not entirely clear. We aimed to profile the ARGs in sputum from adults with bronchiectasis, and explore the association with airway microbiome and disease severity and subtypes. In this longitudinal study, we prospectively collected 118 sputum samples from stable and exacerbation visits of 82 bronchiectasis patients and 19 healthy subjects. We profiled ARGs with shotgun metagenomic sequencing, and linked these to sputum microbiome and clinical characteristics, followed by validation in an international cohort. We compared ARG profiles in bronchiectasis according to disease severity, blood and sputum inflammatory subtypes. Unsupervised clustering revealed a Pseudomonas predominant subgroup (n = 16), Haemophilus predominant subgroup (n = 48), and balanced microbiome subgroup (N = 54). ARGs of multi-drug resistance were over-dominant in the Pseudomonas-predominant subgroup, while ARGs of beta-lactam resistance were most abundant in the Haemophilus-predominant subgroup. Pseudomonas-predominant subgroup yielded the highest ARG diversity and total abundance, while Haemophilus-predominant subgroup and balanced microbiota subgroup were lowest in ARG diversity and total abundance. PBP-1A, ksgA and emrB (multidrug) were most significantly enriched in Haemophilus-predominant subtype. ARGs generally correlated positively with Bronchiectasis Severity Index, fluoroquinolone use, and modified Reiff score. 68.6% of the ARG-clinical correlations could be validated in an independent international cohort. In conclusion, ARGs are differentially associated with the dominant microbiome and clinical characteristics in bronchiectasis.

Sputum inflammatory, neural, and remodelling mediators in eosinophilic and non-eosinophilic asthma

BACKGROUND

Neural and remodelling mechanisms may play a role in asthma, particularly non-eosinophilic asthma (NEA).

OBJECTIVE

To assess sputum mediators associated with neural, remodelling, and inflammatory mechanisms in eosinophilic asthma (EA), NEA, and non-asthmatics.

METHODS

111 participants with and 62 without asthma (14-21 years) underwent sputum induction, exhaled nitric oxide (FeNO), atopy, and spirometry tests. Twenty-four mediators were measured in sputum using ELISA or bead array. EA (n=52) and NEA (n=59) were defined using a sputum eosinophil cut-point of ≥2.5%.

RESULTS

Elevated levels of nociceptin (median: 39.1 vs 22.4 ng/mL, p=0.03), periostin (33.8 vs 9.4 ng/mL, p=0.01), and eosinophil cationic protein (ECP); (220.1 vs 83.7 ng/mL, p=0.03) were found in asthmatics compared with non-asthmatics. Nociceptin was elevated in EA (54.8 vs 22.4 ng/mL, p=0.02) compared with non-asthmatics. EA had higher levels of inflammatory (ECP: 495.5 vs 100.3 ng/mL, p≤0.01; interleukin-1β: 285.3 vs 209.3 pg/mL, p=0.03; histamine: 5805.0 vs 3172.5 pg/mL, p=<0.01) and remodelling (vascular endothelial growth factor A (VEGF-A); 3.3 vs 2.5 ng/mL, p=0.03; periostin: 47.7 vs 22.1 ng/mL, p=0.04) mediators than NEA. Whilst macrophages were associated with neural mediators e.g. neurokinin A (r=0.27, p=0.01) and nociceptin (r=0.30, p=0.02), granulocytes were associated with inflammatory/remodelling mediators; e.g. ECP and VEGF-A correlated with neutrophils (r=0.53 & r=0.33 respectively, p=<0.01) and eosinophils (r=0.53 & r=0.29 respectively, p≤0.01).

CONCLUSION

Elevated levels of nociceptin and inflammatory/remodelling markers were found in EA, but no evidence for neural and remodelling pathways was found in NEA. Neural and remodelling mechanisms appear to coexist with inflammation.

Heart rate variability as a marker of autonomic nervous system activity in young people with eosinophilic and non-eosinophilic asthma

OBJECTIVE

An imbalance in autonomic nervous system (ANS) activity may play a role in asthma, but it is unclear whether this is associated with specific pathophysiology. This study assessed ANS activity by measuring heart rate variability (HRV) in eosinophilic (EA) and non-eosinophilic asthma (NEA) and people without asthma.

METHODS

HRV, combined hypertonic saline challenge/sputum induction, exhaled nitric oxide (FeNO), skin prick tests to measure atopy, and spirometry tests were conducted in teenagers and young adults (14-21 years) with (n = 96) and without (n = 72) generally well-controlled asthma. HRV parameters associated with sympathetic and parasympathetic ANS branches were analyzed. EA and NEA were defined using a 2.5% sputum eosinophil cut-point. Airway hyperreactivity (AHR) was defined as ≥15% reduction in FEV₁ following saline challenge.

RESULTS

HRV parameters did not differ between asthmatics and non-asthmatics or EA and NEA. They were also not associated with markers of inflammation, lung function or atopy. However, increased absolute low frequency (LFµs²; representing increased sympathetic nervous system (SNS) activity) was found in asthmatics who used β-agonist medication compared to those who did not (median: 1611, IQR 892-3036 vs 754, 565-1592; p < 0.05) and increased normalized low frequency (LF nu) was found in those with AHR compared to without AHR (64, 48-71 vs 53, 43-66; p < 0.05).

CONCLUSION

ANS activity (as measured using HRV analysis) is not associated with pathophysiology or inflammatory phenotype in young asthmatics with generally well-controlled asthma. However, enhanced SNS activity can be detected in asthmatics with AHR or who use β-agonist medication.

Parental Education and Adolescents' Asthma: The Role of Ethnicity

While high parental education is associated with better health, this association may be weaker for ethnic minority than for ethnic majority families. It is unknown whether the association between parental education and adolescents' asthma also varies by ethnicity.

AIM

To study the association between parental education and adolescents' asthma overall and by ethnicity.

METHODS

The current study used data from the Population Assessment of Tobacco and Health (PATH)-Adolescents study. All participants were 12 to 17-year-old non-smokers (n = 8652). The outcome of interest was adolescents' asthma. The predictor of interest was baseline parental education, the covariates were age, sex, and number of parents present at baseline, and the moderator was ethnicity.

RESULTS

According to logistic regression analyses, higher parental education was predictive of adolescents' asthma; however, this association was weaker for Latino than non-Latino adolescents (OR 1.771; CI 1.282-2.446). We did not find a significant difference in the effect of parental education on asthma of White and African American adolescents. Our stratified models also showed that higher parental education was associated with lower asthma for non-Latino but not for Latino adolescents.

CONCLUSION

The effect of high parental education on adolescents' asthma prevalence differs between Latino and non-Latino families, with Latino families showing weaker protective effects of parental education on adolescents' asthma. Future research should test the role of exposure to environmental pollutants, neighborhood quality, and prevalence of smoking in social network members as well as other contextual factors at home, in school, and in the neighborhood that may increase prevalence of asthma in Latino adolescents regardless of their parental education. Given that these potential causes are multi-level, potential causes of such disparities should be tested in future multi-level research.

Motile Ciliary Disorders of the Nasal Epithelium in Adults With Bronchiectasis

BACKGROUND

Motile ciliary disorder (MCD) has been implicated in chronic inflammatory airway diseases such as asthma and COPD.

RESEARCH QUESTION

What are the characteristics of MCD of the nasal epithelium and its association with disease severity and inflammatory endotypes in adults with bronchiectasis?

STUDY DESIGNS AND METHODS

In this observational study, we recruited 167 patients with bronchiectasis and 39 healthy control participants who underwent brushing of the nasal epithelium. A subgroup of patients underwent bronchoscopy for bronchial epithelium sampling (n = 13), elective surgery for bronchial epithelium biopsy (n = 18), and blood sampling for next-generation sequencing (n = 37). We characterized systemic and airway inflammatory endotypes in bronchiectasis. We conducted immunofluorescence assays to profile ultrastructural (dynein axonemal heavy chain 5 [DNAH5], dynein intermediate chain 1 [DNAI1], radial spoke head protein 9 [RSPH9]) and ciliogenesis marker expression (ezrin).

RESULTS

MCD was present in 89.8% of patients with bronchiectasis, 67.6% showed secondary MCD, and 16.2% showed primary plus secondary MCD. Compared with healthy control participants, patients with bronchiectasis yielded abnormal staining patterns of DNAH5, DNAI1, and RSPH9 (but not ezrin) that were more prominent in moderate to severe bronchiectasis. MCD pattern scores largely were consistent between upper and lower airways and between large-to-medium and small airways in bronchiectasis. Coexisting nasal diseases and asthma did not confound nasal ciliary ultrastructural marker expression significantly. The propensity of MCD was unaffected by the airway or systemic inflammatory endotypes. MCD, particularly an ultrastructural abnormality, was notable in patients with mild bronchiectasis who showed blood or sputum eosinophilia.

INTERPRETATION

Nasal ciliary markers profiling provides complimentary information to clinical endotyping of bronchiectasis.

Asthma inflammatory phenotypes on four continents: most asthma is non-eosinophilic

BACKGROUND

Most studies assessing pathophysiological heterogeneity in asthma have been conducted in high-income countries (HICs), with little known about the prevalence and characteristics of different asthma inflammatory phenotypes in low-and middle-income countries (LMICs). This study assessed sputum inflammatory phenotypes in five centres, in Brazil, Ecuador, Uganda, New Zealand (NZ) and the United Kingdom (UK).

METHODS

We conducted a cross-sectional study of 998 asthmatics and 356 non-asthmatics in 2016-20. All centres studied children and adolescents (age range 8-20 years), except the UK centre which involved 26-27 year-olds. Information was collected using questionnaires, clinical characterization, blood and induced sputum.

RESULTS

Of 623 asthmatics with sputum results, 39% (243) were classified as eosinophilic or mixed granulocytic, i.e. eosinophilic asthma (EA). Adjusted for age and sex, with NZ as baseline, the UK showed similar odds of EA (odds ratio 1.04, 95% confidence interval 0.37-2.94) with lower odds in the LMICs: Brazil (0.73, 0.42-1.27), Ecuador (0.40, 0.24-0.66) and Uganda (0.62, 0.37-1.04). Despite the low prevalence of neutrophilic asthma in most centres, sputum neutrophilia was increased in asthmatics and non-asthmatics in Uganda.

CONCLUSIONS

This is the first time that sputum induction has been used to compare asthma inflammatory phenotypes in HICs and LMICs. Most cases were non-eosinophilic, including in settings where corticosteroid use was low. A lower prevalence of EA was observed in the LMICs than in the HICs. This has major implications for asthma prevention and management, and suggests that novel prevention strategies and therapies specifically targeting non-eosinophilic asthma are required globally.

A rational approach to compare and select biologic therapeutics in asthma

OBJECTIVE

To review key literature on asthma biologic therapeutics-currently available and under investigation-to inform a rational approach to select biologics for the management of people with severe asthma by precision medicine.

DATA SOURCES

We used the PubMed database to review literature on biologic therapeutics in asthma.

STUDY SELECTIONS

We included published randomized control trials and real-world studies on biologic therapeutics, available in English, through September 2021.

RESULTS

Increased understanding of asthma endotypes and the roles of various inflammatory mechanisms has led to therapeutic agents that inhibit specific cytokines or immune pathways. Currently available biologic therapeutics target type 2-high asthma. Grouped by mechanisms of action, there are the following 3 types: (1) anti-immunoglobulin E, (2) anti-interleukin (IL)-5 or IL-5 receptor, and (3) anti-IL-4 receptor α. There are also various potential future biologic therapeutics currently under investigation. Although there remains a paucity of data regarding prospective direct head-to-head comparisons of biologic therapeutics in asthma, there are some retrospective and indirect comparison data available.

CONCLUSION

Precision medicine guides selection of biologic therapeutics along with shared decision-making. Biomarkers, although not comprehensive, allow approximations of likely mechanisms. Use of biomarkers, to include historical levels and trends, in addition to consideration of key clinical characteristics and comorbidities can greatly help guide biologic selection. Efficacy, safety, potential adverse effects, indications for other key comorbidities, and logistics should also be considered.

IL-26 in asthma and COPD

INTRODUCTION

New targets are needed to enable more accurate diagnosis, monitoring and effective therapy in uncontrolled asthma and chronic obstructive pulmonary disease (COPD), two disorders characterized by pathogenic alterations in the innate immune response. Interestingly, the IL-10-related cytokine IL-26 has been found to be abundantly expressed in human airways and alterations in its expression have been linked to reduced lung function and markers of neutrophilic inflammation in patients with uncontrolled asthma or COPD.

AREAS COVERED

Literature search was conducted on PubMed to identify articles in the field of IL-26 immunology, as well as clinical studies on IL-26 in asthma and COPD, published between 2000 and 2021. We outline the main sources of IL-26 in human airways, as well as the effect of this cytokine on relevant immune and structural cells. Finally, we discuss the potential involvement of IL-26 in the pathophysiology of uncontrolled asthma and COPD.

EXPERT OPINION

IL-26 constitutes a potential target for diagnostic purposes and therapeutic modulation of the innate immune response in the airways of patients with asthma and COPD. It seems reasonable to expect more conclusive evidence of its clinical utility for personalized medicine within the coming 5-year period.

Enhanced airway sensory nerve reactivity in non-eosinophilic asthma

BACKGROUND

Neural mechanisms may play an important role in non-eosinophilic asthma (NEA). This study compared airway sensory nerve reactivity, using capsaicin challenge, in eosinophilic asthma (EA) and NEA and non-asthmatics.

METHODS

Thirty-eight asthmatics and 19 non-asthmatics (aged 14-21 years) underwent combined hypertonic saline challenge/sputum induction, fractional exhaled nitric oxide, atopy and spirometry tests, followed by capsaicin challenge. EA and NEA were defined using a sputum eosinophil cut-point of 2.5%. Airway hyperreactivity was defined as a ≥15% drop in FEV₁ during saline challenge. Sensory nerve reactivity was defined as the lowest capsaicin concentration that evoked 5 (C5) coughs.

RESULTS

Non-eosinophilic asthmatics (n=20) had heightened capsaicin sensitivity (lower C5) compared with non-asthmatics (n=19) (geometric mean C5: 58.3 µM, 95% CI 24.1 to 141.5 vs 193.6 µM, 82.2 to 456.0; p<0.05). NEA tended to also have greater capsaicin sensitivity than EA, with the difference in capsaicin sensitivity between NEA and EA being of similar magnitude (58.3 µM, 24.1 to 141.5 vs 191.0 µM, 70.9 to 514.0) to that observed between NEA and non-asthmatics; however, this did not reach statistical significance (p=0.07). FEV₁ was significantly reduced from baseline following capsaicin inhalation in both asthmatics and non-asthmatics but no differences were found between subgroups. No associations with capsaicin sensitivity and atopy, sputum eosinophils, blood eosinophils, asthma control or treatment were observed.

CONCLUSION

NEA, but not EA, showed enhanced capsaicin sensitivity compared with non-asthmatics. Sensory nerve reactivity may therefore play an important role in the pathophysiology of NEA.

Airway Remodeling in Asthma

Asthma is an inflammatory disease of the airways that may result from exposure to allergens or other environmental irritants, resulting in bronchoconstriction, wheezing, and shortness of breath. The structural changes of the airways associated with asthma, broadly referred to as airway remodeling, is a pathological feature of chronic asthma that contributes to the clinical manifestations of the disease. Airway remodeling in asthma constitutes cellular and extracellular matrix changes in the large and small airways, epithelial cell apoptosis, airway smooth muscle cell proliferation, and fibroblast activation. These pathological changes in the airway are orchestrated by crosstalk of different cell types within the airway wall and submucosa. Environmental exposures to dust, chemicals, and cigarette smoke can initiate the cascade of pro-inflammatory responses that trigger airway remodeling through paracrine signaling and mechanostimulatory cues that drive airway remodeling. In this review, we explore three integrated and dynamic processes in airway remodeling: (1) initiation by epithelial cells; (2) amplification by immune cells; and (3) mesenchymal effector functions. Furthermore, we explore the role of inflammaging in the dysregulated and persistent inflammatory response that perpetuates airway remodeling in elderly asthmatics.

Blood eosinophil count in the general population: typical values and potential confounders

There is growing interest in blood eosinophil counts in the management of chronic respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD). Despite this, typical blood eosinophil levels in the general population, and the impact of potential confounders on these levels have not been clearly defined.We measured blood eosinophil counts in a random sample of 11 042 subjects recruited from the general population in Austria. We then: 1) identified factors associated with high blood eosinophil counts (>75th percentile); and 2) excluded subjects with these factors to estimate median blood eosinophil counts in a "healthy" sub-population (n=3641).We found that: 1) in the entire cohort, age ≤18 years (OR 2.41), asthma (OR 2.05), current smoking (OR 1.72), positive skin prick test (OR 1.64), COPD (OR 1.56), metabolic syndrome (OR 1.41), male sex (OR 1.36) and obesity (OR 1.16) were significantly (p<0.05) associated with high blood eosinophil counts (binary multivariable logistic regression analysis), and had an additive effect; and 2) after excluding these factors, in those older than 18 years, blood eosinophil counts were higher in males than in females (median 120 (5%-95% CI: 30-330) versus 100 (30-310) cells·µL^-1, respectively) and did not change with age.Median blood eosinophil counts in adults are considerably lower than those currently regarded as normal, do not change with age beyond puberty, but are significantly influenced by a variety of factors which have an additive effect. These observations will contribute to the interpretation of blood eosinophil levels in clinical practice.

Value of bronchial reversibility to salbutamol, exhaled nitric oxide and responsiveness to methacholine to corroborate the diagnosis of asthma in children

INTRODUCTION AND OBJECTIVES

Functional and inflammatory measures have been recommended to corroborate asthma diagnosis in schoolchildren, but the evidence in this regard is conflicting. We aimed to determine, in real-life clinical situation, the value of spirometry, spirometric bronchial reversibility to salbutamol (BDR), bronchial responsiveness to methacholine (MCT) and fractional exhaled nitric oxide (FENO), to corroborate the diagnosis of asthma in children on regular inhaled corticosteroids (ICS) referred from primary care.

METHODS

One hundred and seventy-seven schoolchildren with mild-moderate persistent asthma, on treatment with regular ICS, participated in the study. Abnormal tests were defined as FENO ≥ 27 ppb, BDR (FEV1 ≥ 12%) and methacholine PC20 ≤ 4 mg/mL.

RESULTS

The proportions of positive BDR, FENO and MCT, were 16.4%, 33.3%, and 87.0%, respectively. MCT was associated with FENO (p < 0.03) and BDR (p = 0.001); FENO was associated with BDR (p = 0.045), family history of asthma (p = 0.003) and use of asthma medication in the first two years of life (p = 0.004). BDR was significantly related with passive tobacco exposure (p = 0.003).

CONCLUSIONS

Spirometry, BDR and BDR had a poor performance for corroborating diagnosis in our asthmatic children on ICS treatment; on the contrary, MCT was positive in most of them, which agrees with previous reports. Although asthma tests are useful to corroborate asthma when positive, clinical diagnosis remains the best current approach for asthma diagnosis, at least while better objective and feasible measurements at the daily practice are available. At present, these tests may have a better role for assessing the management and progression of the condition.

Respiratory health in professional cleaners: Symptoms, lung function, and risk factors

BACKGROUND

Cleaning is associated with an increased risk of asthma symptoms, but few studies have measured functional characteristics of airway disease in cleaners.

AIMS

To assess and characterize respiratory symptoms and lung function in professional cleaners, and determine potential risk factors for adverse respiratory outcomes.

METHODS

Symptoms, pre-/post-bronchodilator lung function, atopy, and cleaning exposures were assessed in 425 cleaners and 281 reference workers in Wellington, New Zealand between 2008 and 2010.

RESULTS

Cleaners had an increased risk of current asthma (past 12 months), defined as: woken by shortness of breath, asthma attack, or asthma medication (OR = 1.83, 95% CI = 1.18-2.85). Despite this, they had similar rates of current wheezing (OR = 0.93, 95% CI = 0.65-1.32) and were less likely to have a doctor diagnosis of asthma ever (OR = 0.62, 95% CI = 0.42-0.92). Cleaners overall had lower lung function (FEV₁ , FVC; P < .05). Asthma in cleaners was associated with less atopy (OR = 0.35, 95% CI = 0.13-0.90), fewer wheezing attacks (OR = 0.40, 95% CI = 0.17-0.97; >3 vs ≤3 times/year), and reduced bronchodilator response (6% vs 9% mean FEV₁ -%-predicted change, P < .05) compared to asthma in reference workers. Cleaning of cafes/restaurants/kitchens and using upholstery sprays or liquid multi-use cleaner was associated with symptoms, whilst several exposures were also associated with lung function deficits (P < .05).

CONCLUSIONS AND CLINICAL RELEVANCE

Cleaners are at risk of some asthma-associated symptoms and reduced lung function. However, as it was not strongly associated with wheeze and atopy, and airway obstruction was less reversible, asthma in some cleaners may represent a distinct phenotype.

Phenotype-Specific Therapeutic Effect of Rhodiola wallichiana var. cholaensis Combined with Dexamethasone on Experimental Murine Asthma and Its Comprehensive Pharmacological Mechanism

The heterogeneity of asthma involves complex pathogenesis leading to confusion regarding the choice of therapeutic strategy. In the clinic, asthma is commonly classified as having either eosinophilic asthma (EA) or non-eosinophilic asthma (NEA) phenotypes. Microbiota colonizing in airways has been demonstrated to induce distinct phenotypes of asthma and the resistance to steroids. Rhodiola wallichiana var. cholaensis (RWC) has the potential to alleviate asthmatic inflammation according to recent studies, but its pharmacological mechanisms remain unclarified. In our study, murine asthmatic phenotypes were established and treated with RWC and/or dexamethasone (DEX). Combined treatment with RWC and DEX could improve spirometry and airway hyperresponsiveness (AHR) in asthmatic phenotypes, alleviate steroid resistance in NEA, and reduce the inflammatory infiltration of the both phenotypes. The combined treatment increased Th1, regulated the imbalance of Th2/Th1, and decreased the related cytokines in EA. As for NEA, the combined treatment reduced Th17 and promoted the accumulation of regulatory T cells (Tregs) in lung. A microbiome study based on 16S rDNA sequencing technique revealed the significantly changed structure of the lower airway microbiota after combined treatment in NEA, with 4 distinct genera and 2 species identified. OPLS-DA models of metabolomics analysis based on UPLC-Q/TOF-MS technique identified 34 differentiated metabolites and 8 perturbed metabolic pathways. A joint multiomics study predicted that the colonized microbiota in airways might be associated with susceptibility of asthma and steroid resistance, which involved systematic and pulmonary metabolic perturbation. In summary, the pharmacological network of RWC included the complicated interaction mechanisms of immune regulation, microbiota change, and metabolic perturbation.

Clinical profile of predefined asthma phenotypes in a large cohort of UK primary care patients (Clinical Practice Research Datalink)

BACKGROUND

Distinct asthma phenotypes have previously been suggested, including benign asthma, atopic asthma and obese non-eosinophilic asthma. This study aims to establish if these phenotypes can be identified using data recorded in primary care clinical records and reports on patient characteristics and exacerbation frequency.

METHODS

A population-based cohort study identified 193,999 asthma patients in UK primary care from 2007 to 2017. We used linked primary and secondary care data from the Clinical Practice Research Datalink, Hospital Episode Statistics and Office for National Statistics. Patients were classified into predefined phenotypes or included in an asthma "not otherwise specified" (NOS) group. We used negative binomial regression to calculate the exacerbation rates and adjusted rate ratios. Rate ratios were further stratified by asthma treatment step.

RESULTS

In our cohort, 3.9% of patients were categorized as benign asthma, 28.6% atopic asthma and 4.8% obese non-eosinophilic asthma. About 62.7% of patients were asthma NOS, including asthma NOS without treatment (10.4%), only on short-acting beta agonist (6.1%) and on maintenance treatment (46.2%). Crude severe exacerbation rates per 1,000 person-years were lowest for benign asthma (106.8 [95% CI: 101.2-112.3]) and highest for obese non-eosinophilic asthma (469.0 [451.7-486.2]). Incidence rate ratios for all phenotype groups decreased when stratified by treatment step but remained raised compared to benign asthma.

CONCLUSION

Established phenotypes can be identified in a general asthma population, although many patients did not fit into the specific phenotypes which we studied. Phenotyping patients and knowledge of asthma treatment step could help anticipate clinical course and therefore could aid clinical management but is only possible in a minority of primary care patients based on current phenotypes and electronic health records (EHRs).

Eosinophilic airway inflammation is a main feature of unstable asthma in adolescents

BACKGROUND

Stability of asthma is a clinical phenotype of the disease based on long-term evaluation of control of asthma symptoms and its exacerbations. A relationship between airway inflammation and clinical classification of asthma based on stability criterion has not been well studied.

OBJECTIVES

The purpose of our study was to analyze the inflammation profile of stable and unstable asthma in adolescents treated with moderate and high doses of inhaled corticosteroids.

METHODS

139 young asthmatics of 16.8 (3.25) years were classified in the stable group (N = 72) and unstable group (N = 67) after a 3-month prospective observation. Inflammatory markers including cytogram of the induced sputum (IS), fractional exhaled nitric oxide (FeNO) and bronchial hyperresponsiveness (BHR) following provocation with hypertonic saline and exercises, as well as clinical and spirometric parameters in both groups were compared.

RESULTS

75% of patients with unstable asthma revealed elevated percentage of eosinophils in the induced sputum (>2.5%), and mean values were significantly higher in comparison with stable asthma: 2.0 (0,5-4,2) vs 5,5 (2,6-11,3), p < 0,001. Bronchial hyperresponsiveness was markedly higher in unstable asthma, especially in asthma with eosinophilic profile; statistically significant differences also related to functional pulmonary tests. In multivariate analysis, asthma instability was significantly associated with sEos (p = 0.005), BHR (p = 0.001) but not FeNO (p = 0.24).

CONCLUSION (AND CLINICAL RELEVANCE)

Eosinophilic inflammation, relatively resistant to high doses of inhaled corticosteroids, is a dominant type of inflammation in unstable asthma in adolescents. Asthma instability is also associated with higher bronchial hyperresponsiveness and lower spirometric parameters. In the light of the new studies and progress in biological methods of therapy of eosinophilic inflammation, unstable asthma, especially in case of severe course, requires extended diagnostics with determination of inflammatory phenotype.

Non-eosinophilic asthma: current perspectives

Although non-eosinophilic asthma (NEA) is not the best known and most prevalent asthma phenotype, its importance cannot be underestimated. NEA is characterized by airway inflammation with the absence of eosinophils, subsequent to activation of non-predominant type 2 immunologic pathways. This phenotype, which possibly includes several not well-defined subphenotypes, is defined by an eosinophil count <2% in sputum. NEA has been associated with environmental and/or host factors, such as smoking cigarettes, pollution, work-related agents, infections, and obesity. These risk factors, alone or in conjunction, can activate specific cellular and molecular pathways leading to non-type 2 inflammation. The most relevant clinical trait of NEA is its poor response to standard asthma treatments, especially to inhaled corticosteroids, leading to a higher severity of disease and to difficult-to-control asthma. Indeed, NEA constitutes about 50% of severe asthma cases. Since most current and forthcoming biologic therapies specifically target type 2 asthma phenotypes, such as uncontrolled severe eosinophilic or allergic asthma, there is a dramatic lack of effective treatments for uncontrolled non-type 2 asthma. Research efforts are now focusing on elucidating the phenotypes underlying the non-type 2 asthma, and several studies are being conducted with new drugs and biologics aiming to develop effective strategies for this type of asthma, and various immunologic pathways are being scrutinized to optimize efficacy and to abolish possible adverse effects.

Understanding asthma phenotypes: the World Asthma Phenotypes (WASP) international collaboration

The World Asthma Phenotypes (WASP) study started in 2016 and has been conducted in five centres, in the UK, New Zealand, Brazil, Ecuador and Uganda. The objectives of this study are to combine detailed biomarker and clinical information in order to 1) better understand and characterise asthma phenotypes in high-income countries (HICs) and low and middle-income countries (LMICs), and in high and low prevalence centres; 2) compare phenotype characteristics, including clinical severity; 3) assess the risk factors for each phenotype; and 4) assess how the distribution of phenotypes differs between high prevalence and low prevalence centres. Here we present the rationale and protocol for the WASP study to enable other centres around the world to carry out similar analyses using a standardised protocol. Large collaborative and integrative studies like this are essential to further our understanding of asthma phenotypes. The findings of this study will help elucidate the aetiological mechanisms of asthma and might potentially identify new causes and guide the development of new treatments, thereby enabling better management and prevention of asthma in both HICs and LMICs.

Paucigranulocytic asthma: Uncoupling of airway obstruction from inflammation

Among patients with asthma, heterogeneity exists regarding the pattern of airway inflammation and response to treatment, prompting the necessity of recognizing specific phenotypes. Based on the analysis of inflammatory cell counts in induced sputum, asthmatic patients can be classified into 4 unique phenotypes: eosinophilic asthma, neutrophilic asthma, mixed granulocytic asthma, and paucigranulocytic asthma (PGA). PGA is an asthma phenotype with no evidence of increased numbers of eosinophils or neutrophils in sputum or blood and in which anti-inflammatory therapies are ineffective at controlling symptoms. Although underinvestigated, PGA is the most common asthma phenotype in patients with stable asthma. However, PGA is sometimes underestimated because of the exclusive reliance on induced sputum cell counts, which are variable among cohorts of studies, prompting the necessity of developing improved biomarkers. Importantly, investigators have reported that inhaled corticosteroids had a limited effect on airway inflammatory markers in patients with PGA and therefore defining PGA as a potentially "steroid-insensitive" phenotype that requires exploration of alternative therapies. PGA manifests as an uncoupling of airway obstruction from airway inflammation that can be driven by structural changes within the airways, such as airway smooth muscle tissue hypertrophy. Animal models provide evidence that processes evoking airway hyperresponsiveness and airway smooth muscle thickening occur independent from inflammation and might be a consequence of a loss of negative homeostatic processes. Collectively, further understanding of PGA with a focus on the characterization, prevalence, clinical significance, and pathobiology derived from animal studies will likely provide precision therapies that will improve PGA clinical outcomes.

Whole Blood Cytokine Response to Local Traffic-Related Particulate Matter in Peruvian Children With and Without Asthma

This study sought to investigate if acute phase immune responses of whole blood from Peruvian children with controlled and uncontrolled asthma differed from children without asthma, following exposure to traffic-related particulate matter (TRPM). TRPM, including particulate matter from diesel combustion, has been shown to stimulate acute airway inflammation in individuals with and without asthma. For this study, a whole blood assay (WBA) was used to test peripheral whole blood samples from 27 children with asthma, and 12 without asthma. Participant blood samples were stimulated, ex vivo, for 24-h with an aqueous extract of TRPM that was collected near study area highways in Lima, Peru. All participant blood samples were tested against the same TRPM extract, in addition to purified bacterial endotoxin and pyrogen-free water, which served as positive and negative WBA controls, respectively. The innate and adaptive cytokine responses were evaluated in cell-free supernatants of the whole blood incubations. Comparatively similar levels were recorded for nine out of the 10 cytokines measured [e.g., – Interleukin (IL)-1β, IL-6, IL-10], regardless of study participant asthma status. However, IL-8 levels in TRPM-stimulated blood from children with uncontrolled asthma were diminished, compared to subjects without asthma (633 pg/ml vs. 1,023 pg/ml, respectively; p < 0.01); IL-8 responses for subjects with controlled asthma were also reduced, but to a lesser degree (799 pg/ml vs. 1,023 pg/ml, respectively; p = 0.10). These relationships were present before, and after, adjusting for age, sex, obesity/overweight status, C-reactive protein levels, and residential proximity to the study area’s major roadway. For tests conducted with endotoxin, there were no discernible differences in cytokine response between groups, for all cytokines measured. The WBA testing conducted for this study highlighted the capacity of the TRPM extract to potently elicit the release of IL-8 from the human whole blood system. Although the small sample size of the study limits the capacity to draw definitive conclusions, the IL-8 responses suggest that that asthma control may be associated with the regulation of a key mediator in neutrophil chemotaxis, at a systemic level, following exposure to PM derived from traffic-related sources.

Novel approaches to the management of noneosinophilic asthma

Noneosinophilic airway inflammation occurs in approximately 50% of patients with asthma. It is subdivided into neutrophilic or paucigranulocytic inflammation, although the proportion of each subtype is uncertain because of variable cut-off points used to define neutrophilia. This article reviews the evidence for noneosinophilic inflammation being a target for therapy in asthma and assesses clinical trials of licensed drugs, novel small molecules and biologics agents in noneosinophilic inflammation. Current symptoms, rate of exacerbations and decline in lung function are generally less in noneosinophilic asthma than eosinophilic asthma. Noneosinophilic inflammation is associated with corticosteroid insensitivity. Neutrophil activation in the airways and systemic inflammation is reported in neutrophilic asthma. Neutrophilia in asthma may be due to corticosteroids, associated chronic pulmonary infection, altered airway microbiome or delayed neutrophil apoptosis. The cause of poorly controlled noneosinophilic asthma may differ between patients and involve several mechanism including neutrophilic inflammation, T helper 2 (Th2)-low or other subtypes of airway inflammation or corticosteroid insensitivity as well as noninflammatory pathways such as airway hyperreactivity and remodelling. Smoking cessation in asthmatic smokers and removal from exposure to some occupational agents reduces neutrophilic inflammation. Preliminary studies of 'off-label' use of licensed drugs suggest that macrolides show efficacy in nonsmokers with noneosinophilic severe asthma and statins, low-dose theophylline and peroxisome proliferator-activated receptor gamma (PPARγ) agonists may benefit asthmatic smokers with noneosinophilic inflammation. Novel small molecules targeting neutrophilic inflammation, such as chemokine (CXC) receptor 2 (CXCR2) antagonists reduce neutrophils, but do not improve clinical outcomes in studies to date. Inhaled phosphodiesterase (PDE)4 inhibitors, dual PDE3 and PDE4 inhibitors, p38MAPK (mitogen-activated protein kinase) inhibitors, tyrosine kinase inhibitors and PI (phosphoinositide) 3kinase inhibitors are under development and these compounds may be of benefit in noneosinophilic inflammation. The results of clinical trials of biological agents targeting mediators associated with noneosinophilic inflammation, such as interleukin (IL)-17 and tumor necrosis factor (TNF)-α are disappointing. Greater understanding of the mechanisms of noneosinophilic inflammation in asthma should lead to improved therapies.