SUMMARY Homeostatic mucosal immune responses are fine-tuned by naturally evolved interactions with native microbes, and integrating these relationships into experimental models can provide new insights into human diseases. Here, we leverage a murine-adapted airway microbe, Bordetella pseudohinzii ( Bph ), to investigate how chronic colonization impacts mucosal immunity and the development of allergic airway inflammation (AAI). Colonization with Bph induces the differentiation of interleukin-17A (IL-17A)-secreting T-helper cells that aid in controlling bacterial abundance. Bph colonization protects from AAI and is associated with increased production of secretory leukocyte protease inhibitor (SLPI), an antimicrobial peptide with anti-inflammatory properties. These findings are additionally supported by clinical data showing that higher levels of upper respiratory SLPI correlate both with greater asthma control and the presence of Haemophilus, a bacterial genus associated with AAI. We propose that SLPI could be used as a biomarker of beneficial host-commensal relationships in the airway.

The composition of the gut microbiota in early childhood is linked to asthma risk but the role of the gut microbiota in older patients with established asthma is less clear. Here, we used a cohort of 38 school-aged children (19 with asthma) and 57 adults (17 with asthma) to develop a model that aids in the design of mechanistic experiments in gnotobiotic mice. These experiments show that enterotoxigenic Bacteroides fragilis (ETBF) is associated with increased gut permeability, oxidative stress, and markers of Th17-mediated inflammation in the lungs of mice following ovalbumin sensitization and challenge (OSC). Further, ETBF is enriched in a human population with asthma compared to healthy controls. Our results provide evidence that ETBF has the potential to alter the phenotype of airway inflammation in a subset of patients with asthma outside of early childhood which suggests that therapies targeting the gut microbiota may be helpful tools for asthma control.

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In the originally published version of this article, due to a data input error, one of the participants in the MARS cohort, participant 0064, was inadvertently categorized as a healthy child in Figure S7 and Tables 1 and S3 instead of as a healthy adult. In addition, in Figures S7C, S7D, and S7E, only a subset of the complete 16S rRNA dataset was shown. The corrected versions of Tables 1 and S3 now appear with the article online. The original and corrected version of Figure S7 appears here. The re-analysis of the corrected dataset does not change the original interpretation of data or conclusions reported in the paper.

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