The airway microbiome is a potential therapeutic target in asthma exacerbations

Published: November 4, 2022

Asthma is one of the major health concerns, affecting more than 300 million people worldwide. Inhaled corticosteroids (ICS) are the main controller medication used to treat asthma symptoms. However, over 10% of patients do not respond well and develop episodes of worsening asthma symptoms, known as exacerbations. These lead to higher medication consumption, reduced quality of life, and increased mortality (>400 thousand deaths per year). In the last decades, the microbial communities inhabiting the human body (human microbiome) have been demonstrated to have a role in the development of asthma. Nonetheless, little is known about its influence on treatment response.

In a study recently published in The Journal of Allergy and Clinical Immunology (JACI), Perez-Garcia and colleagues presented the largest study evaluating the upper-airway microbiome as a biomarker of asthma exacerbations despite ICS use. The authors analyzed the salivary, nasal, and pharyngeal samples from 250 adults and children with asthma enrolled in the Genomics and Metagenomics of Asthma Severity (GEMAS) study. The upper-airway microbiome was profiled by sequencing a specific bacterial genetic marker (16S rRNA gene). Cases and controls were defined based on the presence or absence of asthma exacerbations despite ICS treatment in the past six months. The authors tested for the association of the microbiome diversity and composition with asthma exacerbations, considering potential clinical, demographic, and technical confounders to ensure the robustness of the findings. Moreover, the authors integrated clinical, genetic, and microbiome data to identify potential predictive biomarkers of asthma exacerbations.

The authors demonstrated that the salivary and nasal bacterial diversity was lower in patients who developed asthma exacerbations compared to those who did not, supporting the well-recognized protective effect of high bacterial diversity on allergies and asthma development. They identified differences in the salivary, pharyngeal, and nasal microbiome composition between cases and controls, revealing 18 bacterial genera associated with asthma exacerbations. The bacterial genera with the strongest protective effect in each body site (i.e., Bifidobacterium, Selenomonas, and Porphyromonas) have been considered promising biomarkers and therapeutic probiotics to reduce airway inflammation and bronchial hyperreactivity. The authors developed a new model based on two clinical variables, two genetic variants, and 11 salivary bacterial genera that allowed good discrimination of patients who develop asthma exacerbations from those who did not. These results showed the potential of the salivary microbiome to improve clinical and genetic predictive models of asthma exacerbations.

This study demonstrated for the first time that the diversity and composition of the upper-airway microbiome are associated with asthma exacerbations despite ICS treatment. Moreover, it showed the potential role of the salivary microbiome as a biomarker in asthma precision medicine. This study reinforces the use of non-invasive samples to profile the airway microbiome and remarks on the interest in the human microbiome as a modulable therapeutic target 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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