Biological treatment of obstructive lung diseases.

In the last 30 years, the treatment of obstructive lung diseases, such as asthma and COPD, has seen significant advancements. Introduction of inhaled corticosteroids (ICS) and, more recently, biological treatments has revolutionized care. Biological treatments are very successful in severe asthma and are expected to be approved for COPD soon. Systematic assessment and multidimensional treatment approaches are crucial in both conditions. Future care may involve specialized centres for severe obstructive lung diseases, focusing on personalized approaches and monitoring, as argued in this review.

The airway epithelium: an orchestrator of inflammation, a key structural barrier and a therapeutic target in severe asthma.

Asthma is a disease of heterogeneous pathology, typically characterised by excessive inflammatory and bronchoconstrictor responses to the environment. The clinical expression of the disease is a consequence of the interaction between environmental factors and host factors over time, including genetic susceptibility, immune dysregulation and airway remodelling. As a critical interface between the host and the environment, the airway epithelium plays an important role in maintaining homeostasis in the face of environmental challenges. Disruption of epithelial integrity is a key factor contributing to multiple processes underlying asthma pathology. In this review, we first discuss the unmet need in asthma management and provide an overview of the structure and function of the airway epithelium. We then focus on key pathophysiological changes that occur in the airway epithelium, including epithelial barrier disruption, immune hyperreactivity, remodelling, mucus hypersecretion and mucus plugging, highlighting how these processes manifest clinically and how they might be targeted by current and novel therapeutics.

Airway hyperresponsiveness correlates with airway TSLP in asthma independent of eosinophilic inflammation.

BACKGROUND: Thymic stromal lymphopoietin (TSLP) is released from the airway epithelium in response to various environmental triggers, inducing a type-2 inflammatory response, and is associated with airway inflammation, airway hyperresponsiveness (AHR), and exacerbations. TSLP may also induce AHR via a direct effect on airway smooth muscle and mast cells, independently of type-2 inflammation, although association between airway TSLP and AHR across asthma phenotypes has been described sparsely. OBJECTIVES: This study sought to investigate the association between AHR and levels of TSLP in serum, sputum, and bronchoalveolar lavage in patients with asthma with and without type-2 inflammation. METHODS: A novel ultrasensitive assay was used to measure levels of TSLP in patients with asthma (serum, n = 182; sputum, n = 81; bronchoalveolar lavage, n = 85) and healthy controls (serum, n = 47). The distribution and association among airway and systemic TSLP, measures of AHR, type-2 inflammation, and severity of disease were assessed. RESULTS: TSLP in sputum was associated with AHR independently of levels of eosinophils and fractional exhaled nitric oxide (ρ = 0.49, P = .005). Serum TSLP was higher in both eosinophil-high and eosinophil-low asthma compared to healthy controls: geometric mean: 1600 fg/mL (95% CI: 1468-1744 fg/mL) and 1294 fg/mL (95% CI: 1167-1435 fg/mL) versus 846 fg/mL (95% CI: 661-1082 fg/mL), but did not correlate with the level of AHR. Increasing age, male sex, and eosinophils in blood were associated with higher levels of TSLP in serum, whereas lung function, inhaled corticosteroid dose, and symptom score were not. CONCLUSIONS: The association between TSLP in sputum and AHR to mannitol irrespective of markers of type-2 inflammation further supports a role of TSLP in AHR that is partially independent of eosinophilic inflammation.

Severe asthma trajectories in adults: findings from the NORDSTAR cohort.

BACKGROUND: There is limited evidence on the pathways leading to severe asthma and we are presently unable to effectively predict the progression of the disease. We aimed to describe the longitudinal trajectories leading to severe asthma and to describe clinical events preceding disease progression in a nationwide population of patients with severe asthma. METHODS: We conducted an observational study based on Swedish data from the NORdic Dataset for aSThmA Research (NORDSTAR) research collaboration platform. We identified adult patients with severe asthma in 2018 according to the European Respiratory Society/American Thoracic Society definition and used latent class analysis to identify trajectories of asthma severity over a 10-year retrospective period from 2018. RESULTS: Among 169 128 asthma patients, we identified 4543 severe asthma patients. We identified four trajectories of severe asthma that were labelled as: trajectory 1 "consistently severe asthma" (n=389 (8.6%)), trajectory 2 "gradual onset severe asthma" (n=942 (20.7%)), trajectory 3 "intermittent severe asthma" (n=1685 (37.1%)) and trajectory 4 "sudden onset severe asthma" (n=1527 (33.6%)). "Consistently severe asthma" had a higher daily inhaled corticosteroid dose and more prevalent osteoporosis compared with the other trajectories. Patients with "gradual onset severe asthma" and "sudden onset severe asthma" developed type 2-related comorbidities concomitantly with development of severe asthma. In the latter group, this primarily occurred within 1-3 years preceding onset of severe asthma. CONCLUSIONS: Four distinct trajectories of severe asthma were identified illustrating different patterns of progression of asthma severity. This may eventually enable the development of better preventive management strategies in severe asthma.

Prevalence and management of severe asthma in the Nordic countries: findings from the NORDSTAR cohort.

Background: Real-life evidence on prevalence and management of severe asthma is limited. Nationwide population registries across the Nordic countries provide unique opportunities to describe prevalence and management patterns of severe asthma at population level. In nationwide register data from Sweden, Norway and Finland, we examined the prevalence of severe asthma and the proportion of severe asthma patients being managed in specialist care. Methods: This is a cross-sectional study based on the Nordic Dataset for Asthma Research (NORDSTAR) research collaboration platform. We identified patients with severe asthma in adults (aged ≥18 years) and in children (aged 6-17 years) in 2018 according to the European Respiratory Society/American Thoracic Society definition. Patients managed in specialist care were those with an asthma-related specialist outpatient contact (only available in Sweden and Finland). Results: Overall, we identified 598 242 patients with current asthma in Sweden, Norway and Finland in 2018. Among those, the prevalence of severe asthma was 3.5%, 5.4% and 5.2% in adults and 0.4%, 1.0%, and 0.3% in children in Sweden, Norway and Finland, respectively. In Sweden and Finland, 37% and 40% of adult patients with severe asthma and two or more exacerbations, respectively, were managed in specialist care; in children the numbers were 56% and 41%, respectively. Conclusion: In three Nordic countries, population-based nationwide data demonstrated similar prevalence of severe asthma. In children, severe asthma was a rare condition. Notably, a large proportion of patients with severe asthma were not managed by a respiratory specialist, suggesting the need for increased recognition of severe asthma in primary care.

Airway hyperresponsiveness reflects corticosteroid-sensitive mast cell involvement across asthma phenotypes.

BACKGROUND: Airway hyperresponsiveness is a hallmark of asthma across asthma phenotypes. Airway hyperresponsiveness to mannitol specifically relates to mast cell infiltration of the airways, suggesting inhaled corticosteroids to be effective in reducing the response to mannitol, despite low levels of type 2 inflammation. OBJECTIVE: We sought to investigate the relationship between airway hyperresponsiveness and infiltrating mast cells, and the response to inhaled corticosteroid treatment. METHODS: In 50 corticosteroid-free patients with airway hyperresponsiveness to mannitol, mucosal cryobiopsies were obtained before and after 6 weeks of daily treatment with 1600 µg of budesonide. Patients were stratified according to baseline fractional exhaled nitric oxide (Feno) with a cutoff of 25 parts per billion. RESULTS: Airway hyperresponsiveness was comparable at baseline and improved equally with treatment in both patients with Feno-high and Feno-low asthma: doubling dose, 3.98 (95% CI, 2.49-6.38; P < .001) and 3.85 (95% CI, 2.51-5.91; P < .001), respectively. However, phenotypes and distribution of mast cells differed between the 2 groups. In patients with Feno-high asthma, airway hyperresponsiveness correlated with the density of chymase-high mast cells infiltrating the epithelial layer (ρ, -0.42; P = .04), and in those with Feno-low asthma, it correlated with the density in the airway smooth muscle (ρ, -0.51; P = .02). The improvement in airway hyperresponsiveness after inhaled corticosteroid treatment correlated with a reduction in mast cells, as well as in airway thymic stromal lymphopoietin and IL-33. CONCLUSIONS: Airway hyperresponsiveness to mannitol is related to mast cell infiltration across asthma phenotypes, correlating with epithelial mast cells in patients with Feno-high asthma and with airway smooth muscle mast cells in patients with Feno-low asthma. Treatment with inhaled corticosteroids was effective in reducing airway hyperresponsiveness in both groups.

Trait profiles in difficult-to-treat asthma: Clinical impact and response to systematic assessment.

BACKGROUND: Multidisciplinary systematic assessment improves outcomes in difficult-to-treat asthma, but without clear response predictors. Using a treatable-traits framework, we stratified patients by trait profile, examining clinical impact and treatment responsiveness to systematic assessment. METHODS: We performed latent class analysis using 12 traits on difficult-to-treat asthma patients undergoing systematic assessment at our institution. We examined Asthma Control Questionnaire (ACQ-6) and Asthma Quality of Life Questionnaire (AQLQ) scores, FEV1 , exacerbation frequency, and maintenance oral corticosteroid (mOCS) dose, at baseline and following systematic assessment. RESULTS: Among 241 patients, two airway-centric profiles were characterized by early-onset with allergic rhinitis (n = 46) and adult onset with eosinophilia/chronic rhinosinusitis (n = 60), respectively, with minimal comorbid or psychosocial traits; three non-airway-centric profiles exhibited either comorbid (obesity, vocal cord dysfunction, dysfunctional breathing) dominance (n = 51), psychosocial (anxiety, depression, smoking, unemployment) dominance (n = 72), or multi-domain impairment (n = 12). Compared to airway-centric profiles, non-airway-centric profiles had worse baseline ACQ-6 (2.7 vs. 2.2, p < .001) and AQLQ (3.8 vs. 4.5, p < .001) scores. Following systematic assessment, the cohort showed overall improvements across all outcomes. However, airway-centric profiles had more FEV1 improvement (5.6% vs. 2.2% predicted, p < .05) while non-airway-centric profiles trended to greater exacerbation reduction (1.7 vs. 1.0, p = .07); mOCS dose reduction was similar (3.1 mg vs. 3.5 mg, p = .782). CONCLUSION: Distinct trait profiles in difficult-to-treat asthma are associated with different clinical outcomes and treatment responsiveness to systematic assessment. These findings yield clinical and mechanistic insights into difficult-to-treat asthma, offer a conceptual framework to address disease heterogeneity, and highlight areas responsive to targeted intervention.

Allergen Immunotherapy Enhances Airway Epithelial Antiviral Immunity in Patients with Allergic Asthma (VITAL Study): A Double-Blind Randomized Controlled Trial.

Rationale: Allergic asthma is linked to impaired bronchial epithelial secretion of IFNs, which may be causally linked to the increased risk of viral exacerbations. We have previously shown that allergen immunotherapy (AIT) effectively reduces asthma exacerbations and prevents respiratory infections requiring antibiotics; however, whether AIT alters antiviral immunity is still unknown. Objectives: To investigate the effect of house dust mite sublingual AIT (HDM-SLIT) on bronchial epithelial antiviral and inflammatory responses in patients with allergic asthma. Methods: In this double-blind, randomized controlled trial (VITAL [The Effect of Allergen Immunotherapy on Anti-viral Immunity in Patients with Allergic Asthma]), adult patients with HDM allergic asthma received HDM-SLIT 12-SQ or placebo for 24 weeks. Bronchoscopy was performed at baseline and at Week 24, which included sampling for human bronchial epithelial cells. Human bronchial epithelial cells were cultured at baseline and at Week 24 and stimulated with the viral mimic polyinosinic:polycytidylic acid (poly(I:C)). mRNA expression was quantified using qRT-PCR, and protein concentrations were measured using multiplex ELISA. Measurements and Main Results: Thirty-nine patients were randomized to HDM-SLIT (n = 20) or placebo (n = 19). HDM-SLIT resulted in increased polyinosinic:polycytidylic acid-induced expression of IFN-ß at both the gene (P = 0.009) and protein (P = 0.02) levels. IFN-λ gene expression was also increased (P = 0.03), whereas IL-33 tended to be decreased (P = 0.09). On the other hand, proinflammatory cytokines IL-6 (P = 0.009) and TNF-α (tumor necrosis factor-α) (P = 0.08) increased compared with baseline in the HDM-SLIT group. There were no significant changes in TSLP (thymic stromal lymphopoietin), IL-4, IL-13, and IL-10. Conclusions: HDM-SLIT improves bronchial epithelial antiviral resistance to viral infection. These results potentially explain the efficacy of HDM-SLIT in reducing exacerbations in allergic asthma. Clinical trial registered with www.clinicaltrials.gov (NCT04100902).

Diagnostic value of a medical algorithm for investigation of perioperative hypersensitivity reactions.

BACKGROUND: Evaluation of perioperative hypersensitivity (POH) is challenging, and accurate screening tools are needed to optimize the diagnostic process. We aimed to assess and validate the diagnostic value of a published algorithm (using tryptase and clinical presentation) to identify appropriate individuals for further testing for IgE-mediated POH. METHODS: We analysed the clinical presentation (tryptase elevation, cardiovascular, respiratory, skin involvement) of patients proceeding to testing for possible IgE-mediated POH at a single tertiary referral centre, relative to subsequent skin testing and specific IgE results. Clinical presentations by drug class were also determined. RESULTS: In 293 consecutive patients, the use of a published algorithm based on one or more of; (i) defined increase in serum tryptase, (ii) involvement of at least two-organ systems, or (iii) presentation with new urticaria and/or angioedema; was highly sensitive [98.8% (CI95: 95.7-99.9%)] but less specific [34.6% (CI95: 25.7-44.4%)] in identifying patients testing positive on skin testing and/or specific IgE. Presentation with cardiovascular symptoms was also sensitive [89.8%(CI95: 84.2-94.0%)], while the combination of respiratory symptoms and increased tryptase was most specific [85.9%(CI95:76.6-92.5%)]. Respiratory involvement was more common in neuromuscular blocking agent allergy, while urticaria/angioedema was more common in antibiotic allergy. CONCLUSION: The published algorithm (of tryptase rise, two-organ involvement or new urticaria/angioedema) is highly sensitive, and appropriate as a screening tool to identify patients suitable for testing for IgE-mediated POH.

Mucosal cryobiopsies: a new method for studying airway pathology in asthma.

Background: In vivo studies of airway pathology in obstructive lung disease are limited by poor quality of specimens obtained with forceps. Obtainment of cryobiopsies has increased diagnostic yield in cancer and interstitial lung disease but has not been used in patients with asthma. In a recent pilot study, we found mucosal cryobiopsies to be larger and more intact than conventional forceps biopsies. The aim of the present study was to compare quality and safety of mucosal cryobiopsies versus conventional forceps biopsies in patients with asthma. Methods: Endobronchial biopsies were obtained with forceps and cryoprobe from patients with asthma not currently treated with inhaled steroids and evaluated histologically. Results: A total of 240 cryobiopsies and 288 forceps biopsies were obtained from 48 patients. Bleeding from the biopsy site was common but self-limiting. No major complications related to the procedure were seen. Cryobiopsy cross areas were four times larger compared with forceps. Stretches of intact epithelium were detected in all cryobiopsies compared to 33% in forceps biopsies. Further, the length of intact epithelium was on average four times longer in the cryobiopsies. Importantly, there was a good preservation of both antigens and mRNA in the cryobiopsies ensuring a suitability and robustness for immunohistochemistry and in situ hybridisation. Conclusion: Obtainment of mucosal cryobiopsies in patients with asthma is safe and yields biopsies that are significantly larger and morphologically better preserved compared with traditional forceps biopsies. The cryotechnique thus seems to be a promising tool for future in vivo studies of airway pathology.

Missing sputum samples are common in asthma intervention studies and successful collection at follow-up is related to improvement in clinical outcomes.

Several factors significantly impact ability to produce a sputum sample after an anti-inflammatory intervention and these authors argue that the widely used complete-case analysis is inappropriate for paired sputum-based outcome measures https://bit.ly/3qN2pk5.

House dust mite sensitization and exposure affects bronchial epithelial anti-microbial response to viral stimuli in patients with asthma.

INTRODUCTION: Allergen exposure worsens viral-triggered asthma exacerbations and could predispose the host to secondary bacterial infections. We have previously demonstrated that exposure to house dust mite (HDM) reduced TLR-3-induced IFN-ß in human bronchial epithelial cells (HBECs) from healthy donors. We hypothesize that HDM sensitization in different ways may be involved in both viral and bacterial resistance of HBECs in asthma. In this study, the role of HDM sensitization and effects of HDM exposure on viral stimulus-challenged HBECs from asthmatic donors have been explored with regard to expression and release of molecules involved in anti-viral and anti-bacterial responses, respectively. METHODS: HBECs from HDM-sensitized (HDM+) and unsensitized (HDM-) patients with asthma were used. HBECs were exposed to HDM or heat inactivated (hi)-HDM (20 µg/ml) for 24 h prior to stimulation with the viral infection mimic, Poly(I:C), for 3 or 24 h. Samples were analyzed with ELISA and RT-qPCR for ß-defensin-2, IFN-ß, TSLP, and neutrophil-recruiting mediators: IL-8 and TNF-⍺. NFκB signaling proteins p105, p65, and IκB-⍺ were analyzed by Western blot. RESULTS: Poly(I:C)-induced IFN-ß expression was reduced in HBECs from HDM + compared to HDM- patients (p = 0.05). In vitro exposure of HBECs to HDM furthermore reduced anti-microbial responses to Poly(I:C) including ß-defensin-2, IL-8, and TNF-⍺, along with reduced NFκB activity. This was observed in HBECs from asthma patients sensitized to HDM, as well as in non-sensitized patients. By contrast, Poly (I:C)-induced release of TSLP, a driver of T2 inflammation, was not reduced with exposure to HDM. CONCLUSION: Using HBECs challenged with viral infection mimic, Poly(I:C), we demonstrated that allergic sensitization to HDM was associated with impaired anti-viral immunity and that HDM exposure reduced anti-viral and anti-bacterial defense molecules, but not TSLP, across non-allergic as well as allergic asthma. These data suggest a role of HDM in the pathogenesis of asthma exacerbations evoked by viral infections including sequential viral-bacterial and viral-viral infections.

Azithromycin and hydroxychloroquine in hospitalised patients with confirmed COVID-19: a randomised double-blinded placebo-controlled trial.

BACKGROUND: Combining the antibiotic azithromycin and hydroxychloroquine induces airway immunomodulatory effects, with the latter also having in vitro antiviral properties. This may improve outcomes in patients hospitalised for coronavirus disease 2019 (COVID-19). METHODS: Placebo-controlled double-blind randomised multicentre trial. Patients aged ≥18 years, admitted to hospital for ≤48 h (not intensive care) with a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcription PCR test were recruited. The intervention was 500 mg daily azithromycin for 3 days followed by 250 mg daily azithromycin for 12 days combined with 200 mg twice-daily hydroxychloroquine for all 15 days. The control group received placebo/placebo. The primary outcome was days alive and discharged from hospital within 14 days (DAOH14). RESULTS: After randomisation of 117 patients, at the first planned interim analysis, the data and safety monitoring board recommended stopping enrolment due to futility, based on pre-specified criteria. Consequently, the trial was terminated on 1 February 2021. 61 patients received the combined intervention and 56 patients received placebo. In the intervention group, patients had a median (interquartile range) 9.0 (3-11) DAOH14 versus 9.0 (7-10) DAOH14 in the placebo group (p=0.90). The primary safety outcome, death from all causes on day 30, occurred for one patient in the intervention group versus two patients receiving placebo (p=0.52), and readmittance or death within 30 days occurred for nine patients in the intervention group versus six patients receiving placebo (p=0.57). CONCLUSIONS: The combination of azithromycin and hydroxychloroquine did not improve survival or length of hospitalisation in patients with COVID-19.

Phenotype and severity of asthma determines bronchial epithelial immune responses to a viral mimic.

BACKGROUND: Asthma is characterised by an aggravated immune response to respiratory viral infections. This phenomenon is a clinically well-recognised driver of acute exacerbations, but how different phenotypes of asthma respond immunologically to viruses is unclear. OBJECTIVES: To describe the association between different phenotypes and severity of asthma and bronchial epithelial immune responses to viral stimulation. METHODS: In the Immunoreact study, healthy subjects (n=10) and 50 patients with asthma were included; 30 (60%) were atopic, and 34 (68%) were eosinophilic; 14 (28%) had severe asthma. All participants underwent bronchoscopy with collection of bronchial brushings. Bronchial epithelial cells (BECs) were expanded and stimulated with the viral replication mimic poly (I:C) (Toll-like receptor (TLR)3 agonist) in vitro. The expression of TLR3-induced pro-inflammatory and antiviral responses of BECs were analysed using reverse transcriptase quantitative PCR and multiplex ELISA and compared across asthma phenotypes and severity of disease. RESULTS: Patients with atopic asthma had increased induction of interleukin (IL)-4, interferon (IFN)-ß, IL-6, tumour necrosis factor-α, and IL-1ß after poly (I:C) stimulation compared to non-atopic patients, whereas in patients with eosinophilic asthma only IL-6 and IL-8 induction was higher than in non-eosinophilic asthma. Patients with severe asthma displayed a decreased antiviral IFN-ß, and increased expression of IL-8, most pronounced in atopic and eosinophilic asthmatics. Furthermore, induction of IL-33 in response to poly (I:C) was increased in severe atopic and in severe eosinophilic asthma, but thymic stromal lymphopoietin only in severe eosinophilic asthma. CONCLUSIONS: The bronchial epithelial immune response to a viral mimic stimulation differs between asthma phenotypes and severities, which may be important to consider when targeting novel asthma treatments.

Imiquimod Boosts Interferon Response, and Decreases ACE2 and Pro-Inflammatory Response of Human Bronchial Epithelium in Asthma.

Background: Both anti-viral and anti-inflammatory bronchial effects are warranted to treat viral infections in asthma. We sought to investigate if imiquimod, a TLR7 agonist, exhibits such dual actions in ex vivo cultured human bronchial epithelial cells (HBECs), targets for SARS-CoV-2 infectivity. Objective: To investigate bronchial epithelial effects of imiquimod of potential importance for anti-viral treatment in asthmatic patients. Methods: Effects of imiquimod alone were examined in HBECs from healthy (N=4) and asthmatic (N=18) donors. Mimicking SARS-CoV-2 infection, HBECs were stimulated with poly(I:C), a dsRNA analogue, or SARS-CoV-2 spike-protein 1 (SP1; receptor binding) with and without imiquimod treatment. Expression of SARS-CoV-2 receptor (ACE2), pro-inflammatory and anti-viral cytokines were analyzed by RT-qPCR, multiplex ELISA, western blot, and Nanostring and proteomic analyses. Results: Imiquimod reduced ACE2 expression at baseline and after poly(I:C) stimulation. Imiquimod also reduced poly(I:C)-induced pro-inflammatory cytokines including IL-1ß, IL-6, IL-8, and IL-33. Furthermore, imiquimod increased IFN-ß expression, an effect potentiated in presence of poly(I:C) or SP1. Multiplex mRNA analysis verified enrichment in type-I IFN signaling concomitant with suppression of cytokine signaling pathways induced by imiquimod in presence of poly(I:C). Exploratory proteomic analyses revealed potentially protective effects of imiquimod on infections. Conclusion: Imiquimod triggers viral resistance mechanisms in HBECs by decreasing ACE2 and increasing IFN-ß expression. Additionally, imiquimod improves viral infection tolerance by reducing viral stimulus-induced epithelial cytokines involved in severe COVID-19 infection. Our imiquimod data highlight feasibility of producing pluripotent drugs potentially suited for anti-viral treatment in asthmatic subjects.

The use of the mannitol test as an outcome measure in asthma intervention studies: a review and practical recommendations.

BACKGROUND: The mannitol test is an indirect bronchial challenge test widely used in diagnosing asthma. Response to the mannitol test correlates with the level of eosinophilic and mast cell airway inflammation, and a positive mannitol test is highly predictive of a response to anti-inflammatory treatment with inhaled corticosteroids. The response to mannitol is a physiological biomarker that may, therefore, be used to assess the response to other anti-inflammatory treatments and may be of particular interest in early phase studies that require surrogate markers to predict a clinical response. The main objectives of this review were to assess the practical aspects of using mannitol as an endpoint in clinical trials and provide the clinical researcher and respiratory physician with recommendations when designing early clinical trials. METHODS: The aim of this review was to summarise previous uses of the mannitol test as an outcome measure in clinical intervention studies. The PubMed database was searched using a combination of MeSH and keywords. Eligible studies included intervention or repeatability studies using the standard mannitol test, at multiple timepoints, reporting the use of PD15 as a measure, and published in English. RESULTS: Of the 193 papers identified, 12 studies met the inclusion criteria and data from these are discussed in detail. Data on the mode of action, correlation with airway inflammation, its diagnostic properties, and repeatability have been summarised, and suggestions for the reporting of test results provided. Worked examples of power calculations for dimensioning study populations are presented for different types of study designs. Finally, interpretation and reporting of the change in the response to the mannitol test are discussed. CONCLUSIONS: The mechanistic and practical features of the mannitol test make it a useful marker of disease, not only in clinical diagnoses, but also as an outcome measure in intervention trials. Measuring airway hyperresponsiveness to mannitol provides a novel and reproducible test for assessing efficacy in intervention trials, and importantly, utilises a test that links directly to underlying drivers of disease.

Mast cell tryptase enhances wound healing by promoting migration in human bronchial epithelial cells.

Epithelial damage and increase of intraepithelial mast cells (MC) are characteristics of asthma. The role of MC mediator tryptase and the protease-activated receptor-2 (PAR2) on epithelial wound healing is not fully investigated. Stimulation of bronchial epithelial cells (BECs) with tryptase promoted gap closure, migration and cellular speed compared to controls. Stimulated BECs had higher expression of migration marker CD151 compared to controls. Proliferation marker KI67 was upregulated in tryptase-stimulated BECs compared to controls. Treatment with PAR2 antagonist I-191 reduced gap closure, migration and cell speed compared to BECs stimulated with tryptase. We found that tryptase enhances epithelial wound healing by increased migration and proliferation, which is in part regulated via PAR2. Our data suggest that tryptase might be beneficial in tissue repair under baseline conditions. However, in a pathological context such as asthma with increased numbers of activated MCs, it might lead to epithelial remodeling and loss of function.

Airway Hyperresponsiveness to Inhaled Mannitol Identifies a Cluster of Noneosinophilic Asthma Patients with High Symptom Burden.

BACKGROUND: Patients with asthma are heterogeneous in clinical presentation and in response to treatment. Despite this, tools to guide treatment are limited and include mainly measures of eosinophilic inflammation and symptoms. Airway hyperresponsiveness (AHR) to mannitol is present in patients across inflammatory phenotypes and improve with inhaled corticosteroids. OBJECTIVE: To investigate whether measuring AHR to mannitol in addition to eosinophilic inflammation and symptoms adds information to the phenotypic characterization of patients with asthma. METHODS: A total of 317 patients with asthma from 6 different cohorts were included in the analysis. All patients had measures of AHR to mannitol, blood eosinophils, and Asthma Control Questionnaire 5 available. A cluster analysis using Ward minimum variance method was performed. The distribution of fraction of exhaled nitric oxide, immunoglobulin E, lung function, induced sputum inflammatory cell count, age of onset, and severity of disease was compared between clusters. RESULTS: Four clusters were identified. Three of the clusters had proportionate levels of AHR, eosinophilic inflammation, and symptoms, but 1 cluster presented with low levels of eosinophilic inflammation and a significant symptom burden. Half of the subjects in this cluster presented with AHR to inhaled mannitol. Lung function, fraction of exhaled nitric oxide, body mass index, and immunoglobulin E were normal. CONCLUSIONS: Information on AHR to mannitol in addition to blood eosinophils and symptoms identifies a subgroup of asthma patients with symptomatic, noneosinophilic disease. Airway hyperresponsiveness to mannitol may provide a treatable trait in a subgroup of patients with noneosinophilic asthma.