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Lung Microbiota Contribute to Pulmonary Inflammation and Disease Progression in Pulmonary Fibrosis.

ABSTRACT: Rationale: Idiopathic pulmonary fibrosis (IPF) causes considerable global morbidity and mortality, and its mechanisms of disease progression are poorly understood. Recent observational studies have reported associations between lung dysbiosis, mortality, and altered host defense gene expression, supporting a role for lung microbiota in IPF. However, the causal significance of altered lung microbiota in disease progression is undetermined. Objectives: To examine the effect of microbiota on local alveolar inflammation and disease progression using both animal models and human subjects with IPF. Methods: For human studies, we characterized lung microbiota in BAL fluid from 68 patients with IPF. For animal modeling, we used a murine model of pulmonary fibrosis in conventional and germ-free mice. Lung bacteria were characterized using 16S rRNA gene sequencing with novel techniques optimized for low-biomass sample load. Microbiota were correlated with alveolar inflammation, measures of pulmonary fibrosis, and disease progression. Measurements and Main Results: Disruption of the lung microbiome predicts disease progression, correlates with local host inflammation, and participates in disease progression. In patients with IPF, lung bacterial burden predicts fibrosis progression, and microbiota diversity and composition correlate with increased alveolar profibrotic cytokines. In murine models of fibrosis, lung dysbiosis precedes peak lung injury and is persistent. In germ-free animals, the absence of a microbiome protects against mortality. Conclusions: Our results demonstrate that lung microbiota contribute to the progression of IPF. We provide biological plausibility for the hypothesis that lung dysbiosis promotes alveolar inflammation and aberrant repair. Manipulation of lung microbiota may represent a novel target for the treatment of IPF.

SUBMITTER: O'Dwyer DN

PROVIDER: S-EPMC6515865 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundThe role of the lung microbiome in the pathogenesis of idiopathic pulmonary fibrosis is unknown. We investigated whether unique microbial signatures were associated with progression of idiopathic pulmonary fibrosis.MethodsPatients (aged 35-80 years) with idiopathic pulmonary fibrosis within 4 years of diagnosis from the Correlating Outcomes with biochemical Markers to Estimate Time-progression (COMET) in idiopathic pulmonary fibrosis study were followed up for a maximum of 80 weeks. Progression-free survival was defined as time to death, acute exacerbation, lung transplant, or decrease in forced vital capacity (FVC) of 10% or greater or decrease in diffusion capacity of the lung (DLCO) of 15% or greater. DNA was isolated from 55 samples of bronchoscopic alveolar lavage. 454 pyrosequencing was used to assign operational taxonomic units (OTUs) to bacteria based on a 3% sequence divergence. Adjusted Cox models were used to identify OTUs that were significantly associated with progression-free survival at a p<0.10. These OTUs were then used in the analysis of the principal components. The association between principal components and microbes with high factor loadings and progression-free survival were assessed with Cox regression analyses. The COMET study is registered with ClinicalTrials.gov, number NCT01071707.FindingsMean FVC was 70.1% (SD 17.0) and DLCO 42.3% (14.0) of predicted. Disease progression was significantly associated with increased relative abundance of two OTUs-Streptococcus OTU 1345 (relative risk 1.11, 95% CI 1.04-1.18; p=0.0009) and Staphylococcus OTU 1348 (1.16, 1.03-1.31, p=0.012). Thresholds for relative abundance of each OTU associated with progression-free survival were more than 3.9% for Streptococcus OTU 1345 (10.19, 2.94-35.35; p=0.0002) and more than 1.8% for Staphylococcus OTU 1348 (5.06, 1.71-14.93; p=0.003).InterpretationThese preliminary data suggest progression of idiopathic pulmonary fibrosis is associated with the presence of specific members within the Staphylococcus and Streptococcus genera. Additional research will be needed to identify the specific bacterial species and to ascertain whether this is a causal association.FundingNational Institutes of Health.

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Lung Microbiota Contribute to Pulmonary Inflammation and Disease Progression in Pulmonary Fibrosis.

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