Severity of allergic asthma is related to the respiratory microbiota.
In cases of moderate to severe allergic asthma, the respiratory function is determined by the type of local inflammation and the composition of the respiratory microbiota.
Pulmonary function in people with allergic asthma showing moderate to severe symptoms depends on inflammation in the lower respiratory tract, which itself depends on the composition of the local microbiota. American researchers analyzed the connections between these various parameters in 13 young adults with clinically comparable asthma, before and after treatment with fluticasone propionate, and control subjects (healthy, untreated volunteers).
To this end, they carried out bronchoalveolar lavage, which allowed them to describe the cytokines and chemokines present as well as the composition of the respiratory microbiota. As a result, they distinguished two groups of asthmatic patients. The AP1 group presented a deficit of G-CSF, IFN-γ, and IL-17F and the second group (AP2) had a deficit of IL-2 and IL-10 and an excess of MIP-1β and TNF-α. The latter profile correlated with more significant bronchial obstruction and reduced respiratory function (FEV1*). The authors also identified a group of cytokines, including MIP-1β and TNF-α, that negatively correlated with lung function.
These inflammatory profiles were in turn associated with a specific composition of the respiratory microbiota, with at least seven species represented differently in the two groups. The excess of MIP-1β, for example, was associated with an increase in Streptococcus pneumoniae, and a deficit of IL-2 with a reduction of Enterococci. However, six weeks of fluticasone propionate treatment effectively reduced bronchial obstruction in 12 of the 13 patients and smoothed out phenotypic differences, with a drop in MIP-1β and TNF-α, an increase in IL-2, and a loss of correlation between type of inflammation and respiratory microbiota, confirming the connection between respiratory function, inflammation, andmicrobiota.
*FEV1: Forced Expiratory Volume in 1 second
Turturice B et al. Atopic asthmatic immune phenotypes associated with airway microbiota and airway obstruction. PLoS One. 2017 Oct 20;12(10):e0184566