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Indoor mycobiome-microbiome and type 2-high asthma: toward a specific correlation?

Published: September 11, 2020

Links between microbial environmental exposures and asthma have been well-documented. However up to nowadays, no study has combined deep-sequencing analysis of pulmonary and indoor mycobiomes-microbiomes of asthmatic patients with clinical and endotypes parameters. Among the various described endotypes, Type 2 asthma can be defined by a blood eosinophil count of 300 cell/mm3 or higher and/or FeNO level of 25 ppb or higher.

In a recently published study in The Journal of Allergy and Clinical Immunology (JACI), Delhaes’s research group (Vandenborght et al.) investigated the links between endogenous (or pulmonary) and exogenous (or indoor) mycobiomes and microbiomes in order to decipher the role of microbial exposures onto inflammatory and clinical outcomes of patients with severe asthma.

The authors conducted a pilot study focused on severe asthma patients, from the national COBRA cohort, who were followed-up at the teaching hospital of Bordeaux. Patients received Electrostatic Dust Collectors (EDC) to analyze their indoor microbial floras. Twenty-two of the fifty-five included patients were able to produce sputa during stable or pulmonary exacerbation periods, and therefore exhibited complete pairs of EDC and sputum analyzed using amplicon deep-sequencing (NGS). NGS data were compared between all EDC and sputum samples of patients, according to Type 2-asthma endotypes.

Compared to patients with Type 2-low severe asthma, patients with Type 2-high severe asthma exhibited a distinct signature of their indoor mycobiome and microbiome which was defined by an increase of bacterial alpha-diversity and a decrease of fungal alpha-diversity; the latter being significantly correlated to the level of endobronchial Type 2 inflammation (FeNO levels). Beta-diversity of EDC mycobiome clustered significantly according to Type 2 endotypes. Moreover, using Linear discriminant analysis Effect Size (LEfSe), indoor microbial floras of patients with Type 2-high severe asthma displayed a significant enrichment of medically relevant fungi and bacteria such as Aspergillus, Candida, and Pseudomonas. In addition, the respiratory mycobiome of severe asthma patients shared more taxa with the corresponding indoor mycobiome when sputa were achieved during exacerbation than during stable state.

For the first time, this pilot study revealed an association between indoor mycobiome and clinical features of patients with severe asthma, renewing the interest in deciphering the interactions between indoor microbial exposure, fungi, and host response in asthma.

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.

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Graphical Abstract

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