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Can sputum microbiome be used in phenotyping of severe asthmatics?

Published online: April 27, 2020

Asthma is a heterogenous airway disease which manifests in different clinical presentations (phenotypes). Asthmatic patients have shown to exhibit airway microbial dysbiosis (abnormality or imbalance of host microbial profiles). However, the association of this airway microbial dysbiosis in relation to asthma phenotypes, has not been adequately investigated.

In a recent study published in The Journal of Allergy & Clinical Immunology (JACI), Abdel-Aziz et al. characterized the induced sputum microbiome and metagenome of severe asthma patients (n=100) recruited from the Unbiased BIOmarkers in PREDiction of respiratory disease outcomes (U-BIOPRED) cohort. They performed unsupervised clustering on the microbial profiles to reveal microbiome-driven clusters and later assess their stability after 12-18 months of inclusion. To assess the clustering robustness, the authors included additional 24 mild-moderate asthmatics.

The authors showed that the sputum microbiome/metagenome profiles could identify two severe asthma phenotypes (clusters) that differ in age of asthma onset, residential locations, smoking status, blood and/or sputum inflammatory biomarkers, lung function parameters and used asthma medication. One cluster was relatively more severe compared to the other. Patients in that cluster exhibited more severe airway obstruction, neutrophilia in sputum and/or blood, and reduced macrophages percentages. The microbial profile of the more severe asthma cluster showed apparent microbial dysbiosis as characterized by deficiency of several commensal bacteria and increased abundances of pathogenic bacteria. Interestingly, the identified clusters were relatively stable (approximately 85% of patients remained within the same clusters’ assignments) after 12-18 months of inclusion. In assessing clustering robustness, most of the mild-moderate asthmatics (n=23) were assigned to the less severe cluster, with exception of one patient who was assigned to the more severe cluster showing similar clinical characteristics.

This study highlights the associations between microbial profiles and certain distinct asthma phenotypes. The identified microbiome-driven phenotypes and their relative stability over time, suggest that microbial profiles could be used as a marker of personalized asthma diagnosis and/or treatment.

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

Graphical Abstract

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