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Background Objectives Methods Results Conclusions The effects of inhaled corticosteroids (ICS) on healthy airways are poorly defined.To delineate the effects of ICS on gene expression in healthy airways, without confounding caused by changes in disease‐related genes and disease‐related alterations in ICS responsiveness.Randomized open‐label bronchoscopy study of high‐dose ICS therapy in 30 healthy adult volunteers randomized 2:1 to (i) fluticasone propionate 500 mcg bd daily or (ii) no treatment, for 4 weeks. Laboratory staff were blinded to allocation. Biopsies and brushings were analysed by immunohistochemistry, bulk RNA sequencing, DNA methylation array and metagenomics.ICS induced small between‐group differences in blood and lamina propria eosinophil numbers, but not in other immunopathological features, blood neutrophils, FeNO, FEV1, microbiome or DNA methylation. ICS treatment upregulated 72 genes in brushings and 53 genes in biopsies, and downregulated 82 genes in brushings and 416 genes in biopsies. The most downregulated genes in both tissues were canonical markers of type‐2 inflammation (FCER1A, CPA3, IL33, CLEC10A, SERPINB10 and CCR5), T cell‐mediated adaptive immunity (TARP, TRBC1, TRBC2, PTPN22, TRAC, CD2, CD8A, HLA‐DQB2, CD96, PTPN7), B‐cell immunity (CD20, immunoglobulin heavy and light chains) and innate immunity, including CD48, Hobit, RANTES, Langerin and GFI1. An IL‐17‐dependent gene signature was not upregulated by ICS.In healthy airways, 4‐week ICS exposure reduces gene expression related to both innate and adaptive immunity, and reduces markers of type‐2 inflammation. This implies that homeostasis in health involves tonic type‐2 signalling in the airway mucosa, which is exquisitely sensitive to ICS. [ABSTRACT FROM AUTHOR]

Patients with asthma and chronic obstructive pulmonary disease (COPD) are susceptible to exacerbations, often caused by microbial pathogens. We hypothesised that intracellular Toll-like receptor (TLR) function in blood mononuclear cells (PBMCs) from these subjects would be impaired and that this impairment is related to exacerbation frequency. PBMCs stimulated with a TLR-9 agonist (but not TLR-3 or 7/8) produced significantly less IFN-α in asthma (26 [3-696]pg/ml) compared to control (943 [164-1651]) and COPD (597 [127-1186]) subjects (p=0.0019) but this was not related to the number of exacerbations per year in asthma or COPD. In COPD, IFN-α levels were related to KCO (% predicted) in COPD (r=-0.41, p=0.01). IFN-α was derived from plasmacytoid dendritic cells (pDCs) and their frequency was lower in asthma compared to control subjects (control 0.48% [0.33-0.64] versus asthma 0.29% [0.13-0.34], p=0.019) whereas pDC function per se was not significantly impaired between groups. The mechanism underlying reduced IFN-α production and the clinical consequences in severe asthma remains to be established. [ABSTRACT FROM AUTHOR]

Background: Fungal involvement in asthma is associated with severe disease. The full spectrum of fungal species in asthma is not well described and is derived largely from insensitive culture techniques. Objectives: To use high‐throughput sequencing to describe the airway mycobiota in asthmatics with and without fungal sensitization and healthy controls; to compare samples representing different airway compartments; to determine whether the mycobiota was influenced by the fungal composition of outdoor air; and to compare findings with clinically relevant outcomes. Methods: We amplified the internal transcribed spacer region 2 of the nuclear ribosomal operon to identify the fungal species present. Ninety‐seven subjects were recruited and provided sputum (83 asthmatics; 14 healthy subjects), with 29 also undergoing a bronchoscopy. A subset of airway samples were compared with matched outdoor air and mouthwash samples. Results: Two hundred and six taxa at the species level were identified in sputum, most at low relative abundance. Aspergillus fumigatus, Candida albicans and Mycosphaerella tassiana had the highest relative abundances and were the most prevalent species across all subjects. The airway mycobiota consisted of a complex community with high diversity between individuals. Notable shifts in the balance of fungi detected in the lung were associated with asthma status, asthma duration and biomarkers of inflammation. Aspergillus tubingensis, a member of the Aspergillus niger species complex, was most prevalent from bronchoscopic protected brush samples and significantly associated with a low sputum neutrophilia. Cryptococcus pseudolongus, from the Cryptococcus humicola species complex, was more abundant from bronchoscopy samples than sputum, and differentially more abundant in asthma than health. Conclusions and Clinical Relevance: The airway mycobiota was dominated by a relatively small number of species, but was distinct from the oropharyngeal mycobiota and air samples. Members of the A. niger and C. humicola species complexes may play unexpected roles in the pathogenesis of asthma. [ABSTRACT FROM AUTHOR]