Fungi In Asthma - Investigation Of The Lung Mycobiome And Characterisation Of Allergens

Asthma is a heterogeneous and complex disease, where sensitisation to, and colonisation with fungi have been associated with decreased lung function. The full spectrum of fungi involved with asthma and their role has not been established due in part to limitations in traditional culture methods. Furthermore, most fungi lack commercially available allergy tests and their allergens have not been characterised. To obtain a better understanding of the fungi involved in asthma, subjects with or without fungal sensitisation provided sputum samples which were subjected to amplicon-based high-throughput sequencing to assess the fungal microbiome (mycobiome). A subset also underwent a bronchoscopy. Fungal sensitised people with asthma showed higher levels of Candida dubliniensis in sputum than non-fungal sensitised asthmatics and healthy controls. Aspergillus tubingensis and Cryptococcus pseudolongus were more prevalent and abundant in bronchoscopy-derived samples, particularly from subjects with asthma, and were significantly associated with decreased sputum neutrophil counts. These fungi could contribute to the asthma phenotype, however, their allergen profile is unknown. This was addressed for A. tubingensis, the IgE response of A. tubingensis and its close relative A. niger were investigated. Only subjects with high A. fumigatus-specific IgE levels (> 17 kU/L) showed sensitisation to these fungi. Yet undescribed IgE cross-reactions with Aspergillus fumigatus proteins Asp f 3 and 6 could be detected, which may contribute to lung inflammation. Other potential IgE cross-reactive allergens were identified using immunoprecipitation of fungal proteins from crude extract. Both known and yet undescribed allergens from A. fumigatus could be detected by these proof-of-principle experiments

Fungal bronchitis is a distinct clinical entity which is responsive to antifungal therapy

Chronic productive cough in the context of exacerbations of airway disease can be associated with positive sputum cultures for fungi, in particular Aspergillus fumigatus and Candida spp., suggesting fungal bronchitis, a condition not widely recognised, as a possible cause for the exacerbation. Our objective was to determine the response to antifungal therapy in patients with suspected fungal bronchitis. Retrospective analysis of data extracted from case records of patients under secondary care respiratory clinics who had been treated with triazole therapy for suspected fungal bronchitis between 2010–2017. Primary outcome was lung function response after 1 month of treatment. Nineteen patients with fungal bronchitis due to A. fumigatus and 12 patients due to Candida spp., were included in the study. Most of the patients, particularly in the Aspergillus group, had allergic fungal airway disease on a background of asthma. All but one of the patients in each group were recorded as showing clinical improvement with antifungal therapy. In the majority of patients this was reflected in an improvement in lung function. Aspergillus group: FEV1 (1.44 ± 0.8 L vs 1.6 ± 0.8 L: p < 0.02), FVC (2.49 ± 1.08 L vs 2.8 ± 1.1 L: p = 0.01), and PEF (260 ± 150L/min vs 297 ± 194ml/min: p < 0.02). Candida group: FEV1 (1.6 ± 0.76 L vs 2.0 ± 0.72 L: p < 0.004), FVC (2.69 ± 0.91 L vs 3.13 ± 0.7 L: p = 0.05), and PEF (271± 139L/min vs 333 ± 156 L/min: p = 0.01). Side effects of treatment were common, but resolved on stopping treatment. This service improvement project supports the idea that fungal bronchitis is a distinct clinical entity which is responsive to treatment. Controlled clinical trials to confirm the clinical impression that this is relatively common and treatable complication of complex airway disease are required

The airway fungal microbiome in asthma.

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-sensitisation and healthy controls; to compare samples representing different airway compartments; to determine if 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 Aspergillus niger and Cryptococus humicola species complexes may play unexpected roles in the pathogenesis of asthma