Lung Microbiome Mediates Asthmatics’ Pulmonary Function

The lung microbiome plays a significant role in asthma severity and response to treatment, according to a new study.

Results suggest the microbiome has relevance beyond the gut, and that it is a potential biomarker for asthma.

The microbiome is the ecosystem of good and bad bacteria living in the body. Lower airway microbiota has been associated with clinical features such as airway obstruction, symptom control, and response to corticosteroids.

“Because the lungs continuously and automatically draw air, and any number of environmental agents, into the body, the composition and balance of microbes in the lungs may have a profound effect on many respiratory conditions,” said senior author Patricia Finn, MD, Professor of Medicine at the University of Illinois at Chicago.

Finn and colleagues assessed a cohort of 13 young adult, atopic asthmatics with intermittent or mild/moderate persistent symptoms via bronchoscopy, lavage, and spirometry. The patients were compared to 6 age-matched, non-asthmatic controls and to themselves after 6 weeks of treatment with fluticasone propionate. Airway inflammation was assessed via a cytokine and chemokine panel.

The researchers identified 2 asthmatic phenotypes, termed AP1 and AP2, with distinct bronchoalveolar lavage inflammatory profiles. AP1 was associated with less severe asthma and decreased T-helper cytokines and increased enterococcus bacteria, but normal pulmonary function tests. AP2 was associated with increased pro-inflammatory cytokines, increased oral taxa and strep pneumonia bacteria, and decreased pulmonary function tests, or more severe asthma. This suggests that the relationship between inflammation and the microbiome is associated with pulmonary function in asthmatics. “These data indicate that in atopic asthmatics differences in pulmonary function may be mediated by unique immune responses to the airway microbiome,” the researchers stated.

Also, in both AP1 and AP2, the associations between the composition of the microbiome and specific inflammatory cytokines were decreased after treatment with the inhaled corticosteroid. This suggests that treatment with inhaled corticosteroids may function by dampening responses to microbes.

“The data suggest that further study of the microbiome may help to develop more personalized treatment recommendations for patients with asthma,” said Finn. Asthma research has increasingly focused on the differences between seemingly similar patients.

This study adds to the growing body of evidence that patients benefit from precision medicine approaches to common chronic diseases, such as asthma. “If we can better understand how the individual’s lung microbiome affects asthma and identify likely microbial culprits, we may get to a point where we can predict and control asthma development and severity by shifting the microbiome early in life,” Finn said. “This could be as simple as diet, probiotics, or medication.”

More personalized approaches are being developed for treatment of the most severe forms of asthma. “Our study indicates that even in mild to moderate asthmatics with intermittent or persistent symptom there are distinct sub-phenotypes (AP1 and AP2) that differ in their immune response and microbiome. These sub-phenotypes are associated with important aspects of airway physiology. Additionally, monitoring for microbiological changes, such as an abundance of Streptococcus pneumoniae and oral-pharyngeal taxa, may allow for personalized approaches for patient monitoring,” the researchers stated.