Eosinophilic airway inflammation in asthma is associated with an altered airway microbiome

Publication date: Available online 29 December 2016
Source:Journal of Allergy and Clinical Immunology
Author(s): Asger Sverrild, Pia Kiilerich, Asker Brejnrod, Rebecca Pedersen, Celeste Porsbjerg, Anders Bergqvist, Jonas S. Erjefält, Karsten Kristiansen, Vibeke Backer
BackgroundSubjects with asthma have higher microbiome diversity, and an altered composition with more Proteobacteria and less Bacteroidetes compared to healthy controls. Studies comparing airway inflammation and airway microbiome are sparse, especially in subjects not on anti-inflammatory treatment.ObjectiveTo describe the relationship between the airway microbiome and patterns of airway inflammation in steroid-free subjects with asthma and healthy controls.MethodsBroncho-alveolar lavage was collected from 23 steroid-free, non-smoking subjects with asthma and 10 healthy controls. Bacterial DNA was extracted from and subjected to Illumina MiSeq sequencing of the 16S rDNA V4 region. Eosinophils and neutrophils in submucosa were quantified by immunohistochemical identification and computerized image analysis. Induced sputum was performed, and Airway hyperresponsiveness to mannitol and Fractional Exhaled Nitric Oxide were measured. Relationships between airway microbial diversity and composition, and inflammatory profiles were analyzed.ResultsIn patients with asthma, airway microbial composition was associated with airway eosinophilia and AHR to mannitol, but not airway neutrophilia. The overall composition of the airway microbiome of asthmatics with the lowest levels of eosinophils, but not asthmatics with the highest levels of eosinophils deviated significantly from that of healthy individuals. Asthmatics with the lowest levels of eosinophils had an altered bacterial abundance profile with more Neisseria, Bacteroides and Rothia, and less Sphingomonas, Halomonas and Aeribacillus compared to asthmatics with more eosinophils and healthy controls.ConclusionThe level of eosinophilic airway inflammation correlates with variations in microbiomes across subjects with asthma, whereas neutrophilic airway inflammation does not. This warrants further investigation on molecular pathways involved in eosinophilic as well as non-eosinophilic asthma.



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