Selective production of IL-33-neutralizing autoantibody ameliorates asthma responses and severity.

BACKGROUND: Natural anti-cytokine autoantibodies can regulate homeostasis of infectious and inflammatory diseases. The anti-cytokine autoantibody profile and relevance to the pathogenesis of asthma are unknown. We aim to identify key anti-cytokine autoantibodies in asthma patients, and reveal their immunological function and clinical significance. METHODS: A Luciferase Immunoprecipitation System was used to screen serum autoantibodies against 11 key cytokines in patients with allergic asthma and healthy donors. The antigen-specificity, immunomodulatory functions and clinical significance of anti-cytokine autoantibodies were determined by ELISA, qPCR, neutralization assays and statistical analysis, respectively. Potential conditions for autoantibody induction were revealed by in vitro immunization. RESULTS: Of 11 cytokines tested, only anti-IL-33 autoantibody was significantly increased in asthma, compare to healthy controls, and the proportion positive was higher in patients with mild-to-moderate than severe allergic asthma. In allergic asthma patients, the anti-IL-33 autoantibody level correlated negatively with serum concentration of pathogenic cytokines (e.g., IL-4, IL-13, IL-25 and IL-33), IgE, and blood eosinophil count, but positively with mid-expiratory flow FEF25-75%. The autoantibodies were predominantly IgG isotype, polyclonal and could neutralize IL-33-induced pathogenic responses in vitro and in vivo. The induction of the anti-IL-33 autoantibody in blood B-cells in vitro required peptide IL-33 antigen along with a stimulation cocktail of TLR9 agonist and cytokines IL-2, IL-4 or IL-21. CONCLUSIONS: Serum natural anti-IL-33 autoantibodies are selectively induced in some asthma patients. They ameliorate key asthma inflammatory responses, and may improve lung function of allergic asthma.

Low-Dose Lung Radiation Therapy for COVID-19 Lung Disease: A Preclinical Efficacy Study in a Bleomycin Model of Pneumonitis.

PURPOSE: Low-dose whole lung radiation therapy (LDLR) has been proposed as a treatment for patients with acute respiratory distress syndrome associated with SARS-CoV-2 infection, and clinical trials are underway. There is an urgent need for preclinical evidence to justify this approach and inform dose, scheduling, and mechanisms of action. METHODS AND MATERIALS: Female C57BL/6 mice were treated with intranasal bleomycin sulfate (7.5 or 11.25 units/kg, day 0) and then exposed to whole lung radiation therapy (0.5, 1.0, or 1.5 Gy, or sham; day 3). Bodyweight was measured daily, and lung tissue was harvested for histology and flow cytometry on day 10. Computed tomography lung imaging was performed before radiation (day 3) and pre-endpoint (day 10). RESULTS: Bleomycin caused pneumonitis of variable severity, which correlated with weight loss. LDLR at 1.0 Gy was associated with a significant increase in the proportion of mice recovering to 98% of initial bodyweight, and a proportion of these mice exhibited less severe histopathologic lung changes. Mice experiencing moderate initial weight loss were more likely to respond to LDLR than those experiencing severe initial weight loss. In addition, LDLR (1.0 Gy) significantly reduced bleomycin-induced increases in interstitial macrophages, CD103+ dendritic cells (DCs), and neutrophil-DC hybrids. Overall, bleomycin-treated mice exhibited significantly higher percentages of nonaerated lung in left than right lungs, and LDLR (1.0 Gy) limited further reductions in aerated lung volume in right but not left lungs. LDLR at 0.5 and 1.5 Gy did not improve bodyweight, flow cytometric, or radiologic readouts of bleomycin-induced pneumonitis. CONCLUSIONS: Our data support the concept that LDLR can ameliorate acute inflammatory lung injury, identify 1.0 Gy as the most effective dose, and provide evidence that it is more effective in the context of moderate than severe pneumonitis. Mechanistically, LDLR at 1.0 Gy significantly suppressed bleomycin-induced accumulation of pulmonary interstitial macrophages, CD103+ DCs, and neutrophil-DC hybrids.

Monophosphoryl lipid A directly regulates Th1 cytokine production in human CD4+ T-cells through Toll-like receptor 2 and 4.

BACKGROUND: The monophosphoryl lipid A (MPLA) is a detoxified LPS derivative and an emerging safe immune adjuvant in human vaccine development. The adjuvant MPLA promotes antigen-presenting cell (APC) function and preferentially induces a Th1 response following vaccination. However, the mechanism by which the MPLA detoxicates and exerts its adjuvants effect on T-cell, particualrly the Th1 response is unknown. AIMS: We assessed the direct effects of MPLA on murine and human CD4+ T-cell proliferation and the profile of cytokine production ex vivo. RESULTS: We report that CD4+ T-cells only express functional TLR2 and TLR4 when activated by TCR stimulation, in particularly in the presence of IFNα. The activated T cells thereafter can respond directly to MPLA. MPLA does not affect T-cell proliferation in human T cells, but can induce a balanced Th1 cytokine profile in CD4+ T-cells by reducing the production of Th1 cytokines and enhancing the production of the regulatory cytokine IL-10. The MPLA-mediated regulatory effect on activated CD4+ T-cells is TLR2 and TLR4 dependent and can be abolished by the lipid A blocker polymyxin B. CONCLUSION: These data provide evidence, at least in part, for the safe induction of an appropriate level of Th1 response by adjuvant MPLA in human vaccine development.

COVID-19 and RA share an SPP1 myeloid pathway that drives PD-L1+ neutrophils and CD14+ monocytes.

We explored the potential link between chronic inflammatory arthritis and COVID-19 pathogenic and resolving macrophage pathways and their role in COVID-19 pathogenesis. We found that bronchoalveolar lavage fluid (BALF) macrophage clusters FCN1+ and FCN1+SPP1+ predominant in severe COVID-19 were transcriptionally related to synovial tissue macrophage (STM) clusters CD48hiS100A12+ and CD48+SPP1+ that drive rheumatoid arthritis (RA) synovitis. BALF macrophage cluster FABP4+ predominant in healthy lung was transcriptionally related to STM cluster TREM2+ that governs resolution of synovitis in RA remission. Plasma concentrations of SPP1 and S100A12 (key products of macrophage clusters shared with active RA) were high in severe COVID-19 and predicted the need for Intensive Care Unit transfer, and they remained high in the post-COVID-19 stage. High plasma levels of SPP1 were unique to severe COVID-19 when compared with other causes of severe pneumonia, and IHC localized SPP1+ macrophages in the alveoli of COVID-19 lung. Investigation into SPP1 mechanisms of action revealed that it drives proinflammatory activation of CD14+ monocytes and development of PD-L1+ neutrophils, both hallmarks of severe COVID-19. In summary, COVID-19 pneumonitis appears driven by similar pathogenic myeloid cell pathways as those in RA, and their mediators such as SPP1 might be an upstream activator of the aberrant innate response in severe COVID-19 and predictive of disease trajectory including post-COVID-19 pathology.

Occupation versus environmental factors in hypersensitivity pneumonitis: population attributable fraction.

BACKGROUND: Despite well-documented case series of hypersensitivity pneumonitis (HP), epidemiological data delineating relative contributions of risk factors are sparse. To address this, we estimated HP risk in a case-referent study of occupational and nonoccupational exposures. METHODS: We recruited cases of HP by ICD-9 codes from an integrated healthcare delivery system (IHCDS) and a tertiary medical care centre. We drew referents, matched for age and sex, from the IHCDS. Participants underwent comprehensive, structured telephone interviews eliciting details of occupational and home environmental exposures. We employed a hierarchical analytic approach for data reduction based on the false discovery rate method within clusters of exposures. We measured lung function and selected biomarkers in a subset of participants. We used multivariate logistic regression to estimate exposure-associated odds ratios (ORs) and population attributable fractions (PAFs) for HP. RESULTS: We analysed data for 192 HP cases (148 IHCDS; 44 tertiary care) and 229 referents. Occupational exposures combined more than doubled the odds of developing HP (OR 2.67; 95% CI 1.73-4.14) with a PAF of 34% (95% CI 21-46%); nonoccupational bird exposure also doubled the HP odds (OR 2.02; 95% CI 1.13-3.60), with a PAF of 12% (3-21%). Lung function and selected biomarkers did not substantively modify the risk estimates on the basis of questionnaire data alone. DISCUSSION: In a case-referent approach evaluating HP risk, identifiable exposures accounted, on an epidemiological basis, for approximately two in three cases of disease; conversely, for one in three, the risk factors for disease remained elusive.

Krebs von den Lungen-6 (KL-6) is a pathophysiological biomarker of early-stage acute hypersensitivity pneumonitis among pigeon fanciers.

BACKGROUND: Identifying early stages of hypersensitivity pneumonitis (HP) is hampered by variable presentation, heterogeneous or undetected causal antigens and lack of gold-standard biomarkers. Krebs von den Lungen (KL)-6 is pathophysiological biomarker of alveolar epithelial damage. Pigeon fanciers, susceptible to HP, provide a model to investigate early HP. OBJECTIVE: To test the hypothesis that plasma concentrations of KL-6 are increased in early-stage acute HP. METHODS: Clinical history, spirometry and blood samples were obtained from pigeon fanciers, 20 with intermittent acute symptoms indicative of developing HP, 27 with no symptoms and 10 healthy subjects with no avian exposure. Plasma KL-6 (units/mL) and pigeon antigen-specific IgG antibody were quantified by enzyme immunoassay. Blood lymphocytes were quantified by flow cytometry and antigen specificity by in vitro cytokine production. RESULTS: KL-6 was higher in fanciers than controls, median (IQR) 452 (244, 632) vs 274 (151, 377), P = .01. Although fanciers with symptoms had similar antigen exposure and lung function, they had higher KL-6 than those without, 632 (468, 1314) vs 320 (200, 480), P < .001. KL-6 correlated with IgG antibody titre in those with symptoms, r = .591, P = .006. High KL-6, irrespective of symptom category, was associated with higher antibody (P = .006) and lymphocyte proliferation (P = .041), and lower CD4+ T lymphocyte proportion (P = .032). CONCLUSION AND CLINICAL RELEVANCE: Raised KL-6 is associated with acute symptoms of early-stage HP, and its correlation with antibody may support therapeutic strategies when HP is suspected. KL-6 may act as a mechanistic biomarker of early pathogenesis by linking lung pathophysiological changes with an endotype of immune hypersensitivity.

Why do some asthma patients respond poorly to glucocorticoid therapy?

Glucocorticosteroids are the first-line therapy for controlling airway inflammation in asthma. They bind intracellular glucocorticoid receptors to trigger increased expression of anti-inflammatory genes and suppression of pro-inflammatory gene activation in asthmatic airways. In the majority of asthma patients, inhaled glucocorticoids are clinically efficacious, improving lung function and preventing exacerbations. However, 5-10 % of the asthmatic population respond poorly to high dose inhaled and then systemic glucocorticoids. These patients form a category of severe asthma associated with poor quality of life, increased morbidity and mortality, and constitutes a major societal and health care burden. Inadequate therapeutic responses to glucocorticoid treatment is also reported in other inflammatory conditions such as rheumatoid arthritis and inflammatory bowel disease; however, asthma represents the most studied steroid-refractory disease. Several cellular and molecular events underlying glucocorticoid resistance in asthma have been identified involving abnormalities of glucocorticoid receptor signaling pathways. These events have been strongly related to immunological dysregulation, genetic, and environmental factors such as cigarette smoking or respiratory infections. A better understanding of the multiple mechanisms associated with glucocorticoid insensitivity in asthma phenotypes could improve quality of life for people with asthma but would also provide transferrable knowledge for other inflammatory diseases. In this review, we provide an update on the molecular mechanisms behind steroid-refractory asthma. Additionally, we discuss some therapeutic options for treating those asthmatic patients who respond poorly to glucocorticoid therapy.

Distinct synovial tissue macrophage subsets regulate inflammation and remission in rheumatoid arthritis.

Immune-regulatory mechanisms of drug-free remission in rheumatoid arthritis (RA) are unknown. We hypothesized that synovial tissue macrophages (STM), which persist in remission, contribute to joint homeostasis. We used single-cell transcriptomics to profile 32,000 STMs and identified phenotypic changes in patients with early/active RA, treatment-refractory/active RA and RA in sustained remission. Each clinical state was characterized by different frequencies of nine discrete phenotypic clusters within four distinct STM subpopulations with diverse homeostatic, regulatory and inflammatory functions. This cellular atlas, combined with deep-phenotypic, spatial and functional analyses of synovial biopsy fluorescent activated cell sorted STMs, revealed two STM subpopulations (MerTKposTREM2high and MerTKposLYVE1pos) with unique remission transcriptomic signatures enriched in negative regulators of inflammation. These STMs were potent producers of inflammation-resolving lipid mediators and induced the repair response of synovial fibroblasts in vitro. A low proportion of MerTKpos STMs in remission was associated with increased risk of disease flare after treatment cessation. Therapeutic modulation of MerTKpos STM subpopulations could therefore be a potential treatment strategy for RA.

Cytokines at the Interplay Between Asthma and Atherosclerosis?

Cardiovascular disease (CVD) is an important comorbidity in a number of chronic inflammatory diseases. However, evidence in highly prevalent respiratory disease such as asthma are still limited. Epidemiological and clinical data are not univocal in supporting the hypothesis that asthma and CVD are linked and the mechanisms of this relationship remain poorly defined. In this review, we explore the relationship between asthma and cardiovascular disease, with a specific focus on cytokine contribution to vascular dysfunction and atherosclerosis. This is important in the context of recent evidence linking broad inflammatory signaling to cardiovascular events. However inflammatory regulation in asthma is different to the one typically observed in atherosclerosis. We focus on the contribution of cytokine networks encompassing IL-4, IL-6, IL-9, IL-17A, IL-33 but also IFN-γ and TNF-α to vascular dysfunction in atherosclerosis. In doing so we highlight areas of unmet need and possible therapeutic implications.

Insights into frequent asthma exacerbations from a primary care perspective and the implications of UK National Review of Asthma Deaths recommendations.

The United Kingdom National Review of Asthma Deaths (NRAD) recommends that patients who require ≥3 courses of oral corticosteroids (OCS) for exacerbations in the past year or those on British Thoracic Society (BTS) Step 4/5 treatment must be referred to a specialist asthma service. The aim of the study was to identify the proportion of asthma patients in primary care that fulfil NRAD criteria for specialist referral and factors associated with frequent exacerbations. A total of 2639 adult asthma patients from 10 primary care practices in Glasgow, UK were retrospectively studied between 2014 and 2015. Frequent exacerbators and short-acting ß2-agonist (SABA) over-users were identified if they received ≥2 confirmed OCS courses for asthma and ≥13 SABA inhalers in the past year, respectively. Community dispensing data were used to assess treatment adherence defined as taking ≥75% of prescribed inhaled corticosteroid (ICS) dose. The study population included 185 (7%) frequent exacerbators, 137 (5%) SABA over-users, and 319 (12%) patients on BTS Step 4/5 treatment. Among frequent exacerbators, 41% required BTS Step 4/5 treatment, 46% had suboptimal ICS adherence, 42% had not attended an asthma review in the past year and 42% had no previous input from a specialist asthma service. Older age, female gender, BTS Step 4/5, SABA over-use and co-existing COPD diagnosis increased the risk of frequent exacerbations independently. Fourteen per 100 asthma patients would fulfil the NRAD criteria for specialist referral. Better collaboration between primary and secondary care asthma services is needed to improve chronic asthma care.

MicroRNA-34a dependent regulation of AXL controls the activation of dendritic cells in inflammatory arthritis.

Current treatments for rheumatoid arthritis (RA) do not reverse underlying aberrant immune function. A genetic predisposition to RA, such as HLA-DR4 positivity, indicates that dendritic cells (DC) are of crucial importance to pathogenesis by activating auto-reactive lymphocytes. Here we show that microRNA-34a provides homoeostatic control of CD1c+ DC activation via regulation of tyrosine kinase receptor AXL, an important inhibitory DC auto-regulator. This pathway is aberrant in CD1c+ DCs from patients with RA, with upregulation of miR-34a and lower levels of AXL compared to DC from healthy donors. Production of pro-inflammatory cytokines is reduced by ex vivo gene-silencing of miR-34a. miR-34a-deficient mice are resistant to collagen-induced arthritis and interaction of DCs and T cells from these mice are reduced and do not support the development of Th17 cells in vivo. Our findings therefore show that miR-34a is an epigenetic regulator of DC function that may contribute to RA.

Investigating the causal effect of smoking on hay fever and asthma: a Mendelian randomization meta-analysis in the CARTA consortium.

Observational studies on smoking and risk of hay fever and asthma have shown inconsistent results. However, observational studies may be biased by confounding and reverse causation. Mendelian randomization uses genetic variants as markers of exposures to examine causal effects. We examined the causal effect of smoking on hay fever and asthma by using the smoking-associated single nucleotide polymorphism (SNP) rs16969968/rs1051730. We included 231,020 participants from 22 population-based studies. Observational analyses showed that current vs never smokers had lower risk of hay fever (odds ratio (OR) = 0·68, 95% confidence interval (CI): 0·61, 0·76; P < 0·001) and allergic sensitization (OR = 0·74, 95% CI: 0·64, 0·86; P < 0·001), but similar asthma risk (OR = 1·00, 95% CI: 0·91, 1·09; P = 0·967). Mendelian randomization analyses in current smokers showed a slightly lower risk of hay fever (OR = 0·958, 95% CI: 0·920, 0·998; P = 0·041), a lower risk of allergic sensitization (OR = 0·92, 95% CI: 0·84, 1·02; P = 0·117), but higher risk of asthma (OR = 1·06, 95% CI: 1·01, 1·11; P = 0·020) per smoking-increasing allele. Our results suggest that smoking may be causally related to a higher risk of asthma and a slightly lower risk of hay fever. However, the adverse events associated with smoking limit its clinical significance.

The role of microRNA-155/liver X receptor pathway in experimental and idiopathic pulmonary fibrosis.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is progressive and rapidly fatal. Improved understanding of pathogenesis is required to prosper novel therapeutics. Epigenetic changes contribute to IPF; therefore, microRNAs may reveal novel pathogenic pathways. OBJECTIVES: We sought to determine the regulatory role of microRNA (miR)-155 in the profibrotic function of murine lung macrophages and fibroblasts, IPF lung fibroblasts, and its contribution to experimental pulmonary fibrosis. METHODS: Bleomycin-induced lung fibrosis in wild-type and miR-155-/- mice was analyzed by histology, collagen, and profibrotic gene expression. Mechanisms were identified by in silico and molecular approaches and validated in mouse lung fibroblasts and macrophages, and in IPF lung fibroblasts, using loss-and-gain of function assays, and in vivo using specific inhibitors. RESULTS: miR-155-/- mice developed exacerbated lung fibrosis, increased collagen deposition, collagen 1 and 3 mRNA expression, TGF-ß production, and activation of alternatively activated macrophages, contributed by deregulation of the miR-155 target gene the liver X receptor (LXR)α in lung fibroblasts and macrophages. Inhibition of LXRα in experimental lung fibrosis and in IPF lung fibroblasts reduced the exacerbated fibrotic response. Similarly, enforced expression of miR-155 reduced the profibrotic phenotype of IPF and miR-155-/- fibroblasts. CONCLUSIONS: We describe herein a molecular pathway comprising miR-155 and its epigenetic LXRα target that when deregulated enables pathogenic pulmonary fibrosis. Manipulation of the miR-155/LXR pathway may have therapeutic potential for IPF.

MicroRNA-155-at the Critical Interface of Innate and Adaptive Immunity in Arthritis.

MicroRNAs (miRNAs) are small non-coding RNAs that fine-tune the cell response to a changing environment by modulating the cell transcriptome. miR-155 is a multifunctional miRNA enriched in cells of the immune system and is indispensable for the immune response. However, when deregulated, miR-155 contributes to the development of chronic inflammation, autoimmunity, cancer, and fibrosis. Herein, we review the evidence for the pathogenic role of miR-155 in driving aberrant activation of the immune system in rheumatoid arthritis, and its potential as a disease biomarker and therapeutic target.

Effects of older age and age of asthma onset on clinical and inflammatory variables in severe refractory asthma.

BACKGROUND: Asthma in the elderly as well as asthma of adult-onset has been associated with increased morbidity, but little is known specifically about the effects of age on clinical and inflammatory outcomes in severe refractory asthma. The aims of the study were to examine the effects of age [<65 versus ≥65 years] and age of onset of asthma [childhood-onset, <18 versus adult-onset, ≥18 years] on clinical and inflammatory variables in patients with severe asthma. METHODS: In 1042 subjects with refractory asthma recruited to the British Thoracic Society Severe Asthma Registry, we compared patient demographics, disease characteristics and biomarkers of inflammation in patients aged <65 years (n = 896) versus ≥65 years (n = 146) and onset at age <18 years (n = 430) versus ≥18 years (n = 526). RESULTS: Severe asthma patients aged ≥65 years had improved symptom control, better asthma quality of life and in the last year, less emergency visits and rescue oral steroid courses [3 (1-6) versus 5 (2-7), p < 0.001] than severe asthmatics aged <65 years. Blood eosinophils were lower in the elderly group. Patients with severe adult-onset asthma had similar symptom control, lung function and health-care utilization compared to severe childhood-onset asthma. Adult-onset asthmatics had higher blood eosinophils and were less atopic. CONCLUSIONS: Patients with severe refractory asthma aged ≥65 years exhibit better clinical and health care outcomes and have lower blood eosinophils compared to those aged <65 years. Severe refractory adult-onset asthma is associated with similar levels of asthma control, higher blood eosinophils and less atopy than severe refractory childhood-onset asthma.

MicroRNA-155 regulates monocyte chemokine and chemokine receptor expression in Rheumatoid Arthritis.

OBJECTIVE: To test the hypothesis that miR-155 regulates monocyte migratory potential via modulation of chemokine and chemokine receptor expression in RA, and thereby is associated with disease activity. METHODS: The miR-155 copy-numbers in monocytes from peripheral blood (PB) of healthy (n = 22), RA (n = 24) and RA SF (n = 11) were assessed by real time-PCR using synthetic miR-155 as a quantitative standard. To evaluate the functional impact of miR-155, human monocytes were transfected with control or miR-155 mimic, and the effect on transcript levels, and production of chemokines was evaluated by Taqman low-density arrays and multiplex assays. A comparative study evaluated constitutive chemokine receptor expression in miR-155-/- and wild-type murine (CD115 + Ly6C + Ly6G-) monocytes. RESULTS: Compared with healthy monocytes, the miR-155 copy-number was higher in RA, peripheral blood (PB) and SF monocytes (PB P < 0.01, and SF P < 0.0001). The miR-155 copy-number in RA PB monocytes was higher in ACPA-positive compared with ACPA-negative patients (P = 0.033) and correlated (95% CI) with DAS28 (ESR), R = 0.728 (0.460, 0.874), and with tender, R = 0.631 (0.306, 0.824) and swollen, R = 0.503 (0.125, 0.753) joint counts. Enforced-expression of miR-155 in RA monocytes stimulated the production of CCL3, CCL4, CCL5 and CCL8; upregulated CCR7 expression; and downregulated CCR2. Conversely, miR155-/- monocytes showed downregulated CCR7 and upregulated CCR2 expression. CONCLUSION: Given the observed correlations with disease activity, these data provide strong evidence that miR-155 can contribute to RA pathogenesis by regulating chemokine production and pro-inflammatory chemokine receptor expression, thereby promoting inflammatory cell recruitment and retention in the RA synovium.

Interleukin-33 promoting Th1 lymphocyte differentiation dependents on IL-12.

The pro-Th2 cytokine IL-33 is now emerging as an important Th1 cytokine-IFN-γ inducer in murine CD4(+) T cells that is essential for protective cell-mediated immunity against viral infection in mice. However, whether IL-33 can promote human Th1 cell differentiation and how IL-33 polarizes Th1 cells is less understood. We assessed the ability of IL-33 to induce Th1 cell differentiation and IFN-γ production in vitro and in vivo. We report here that IL-33 alone had no ability in Th1 cell polarization. However it potentiated IL-12-mediated Th1 cell differentiation and IFN-γ production in TCR-stimulated murine and human CD4(+) T cells in vitro and in vivo. IL-33 promoted Th1 cell development via MyD88 and synergized with IL-12 to enhance St2 and IL-12R expression in CD4(+) T cells. These data therefore provide a novel mechanism for Th1 cell differentiation and optimal induction of a Type 1 response. Thus, IL-33 is capable of inducing IL-12-dependent Th1 cell differentiation in human and mouse CD4(+) T cells.

Effectiveness of bronchial thermoplasty in severe asthma in 'real life' patients compared with those recruited to clinical trials in the same centre.

Published information on the effectiveness of bronchial thermoplasty (BT) for severe asthma in 'real life' patients is limited. We compared safety and efficacy outcomes 12 months post procedure in 10 clinic patients and 15 patients recruited to clinical trials of BT at the same centre. Baseline asthma severity was greater in the clinic group. Adverse events were similar. Clinical improvements occurred in 50% of the clinic patients compared with 73% of the research patients.