Faculty Bibliography

Microaspiration is a common phenomenon in healthy subjects, but its frequency is increased in chronic inflammatory airway diseases, and its role in inflammatory and immune phenotypes is unclear. We have previously demonstrated that acellular bronchoalveolar lavage samples from half of the healthy people examined are enriched with oral taxa (here called pneumotypeSPT) and this finding is associated with increased numbers of lymphocytes and neutrophils in bronchoalveolar lavage. Here, we have characterized the inflammatory phenotype using a multi-omic approach. By evaluating both upper airway and acellular bronchoalveolar lavage samples from 49 subjects from three cohorts without known pulmonary disease, we observed that pneumotypeSPT was associated with a distinct metabolic profile, enhanced expression of inflammatory cytokines, a pro-inflammatory phenotype characterized by elevated Th-17 lymphocytes and, conversely, a blunted alveolar macrophage TLR4 response. The cellular immune responses observed in the lower airways of humans with pneumotypeSPT indicate a role for the aspiration-derived microbiota in regulating the basal inflammatory status at the pulmonary mucosal surface.

Background and objectives Airway abnormalities and increased lung tissue citrullination is found in both RA patients and individuals at at-risk for the development of disease. Recent data suggest that the gut (Prevotella copri) and oral (Porphyromonas gingivalis) microbiome might potentially contribute to the priming of an aberrant systemic immune response characteristic of RA. Our objective was to study whether the RA lung microbiome contains distinct taxonomic features associated with local and/or systemic autoimmunity. Materials and methods Bronchoalveolar lavage (BAL) samples from 20 subjects with RA, 10 with sarcoidosis (DC) and 24 healthy controls (HC) were obtained by research bronchoscopy. 16S rDNA sequencing was performed to define microbiota composition. Autoantibodies, including anti-CCP, RF and ACPAs were also measured in sera of RA subjects. Statistical analysis was performed using wilcoxon test and Spearman correlation. Results The16S sequencing data showed similar alpha/beta diversity between RA and DC groups, but significantly different from HC. Taxonomic comparison between groups was performed using LEfSe, which revealed several significant differences (LDA score>2). Multiple taxa, including Rhanella and Rhodanobacter were present only in the RA and DC groups, but completely absent from HC (p < 0.001). While RA BAL samples were enriched with Sphingobacteria, sarcoidosis BAL was enriched with Bacteroidia, Rhizobiales, Nitrospirales, and Campylobacter. Raoultella and Barnesiella correlated with CCP2 levels in BAL (rho = 0.49 and 0.47; p-value = 0.026 and 0.032). Serum levels of CCP-IgA had a negative correlation with Massilia and Tannerella (rho = -0.63 and 0.53; p-value 0.003 and 0.016), and a positive correlation with Vagococcus and Lactobacillus (rho= 0.59 and 0.54; p-value 0.006 and 0.014). Unclas-Lactobacillales also had a positive correlation with serum levels of RF-IgA (rho = 0.71; p-value <0.001). Serum levels of anti-CCP2 antibodies had a positive correlation with Porphyromonas, Rahnella and Chryseobacterium (rho =0.46, 0.46 and 0.45; p-value = 0.03, 0.03 and 0.04). Conclusions Despite the relatively small number of samples analysed, several taxonomic differences were noted between groups. Correlations between relative abundance of specific taxa in RA BAL with serum autoantibodies (ie, anti-CCP) support an association between the lung microbiome and the host immune phenotype in RA. Further evaluation of functional aspects of this microbiome may provide further insights into its possible contribution to RA

RATIONALE: Obesity is characterized by increased systemic and pulmonary blood volumes (pulmonary vascular congestion). Concomitant abnormal alveolar membrane diffusion suggests subclinical interstitial edema. In this setting, functional abnormalities should encompass the entire distal lung including the airways. OBJECTIVES: We hypothesize that in obesity: 1) pulmonary vascular congestion will affect the distal lung unit with concordant alveolar membrane and distal airway abnormalities; and 2) the degree of pulmonary congestion and membrane dysfunction will relate to the cardiac response. METHODS: 54 non-smoking obese subjects underwent spirometry, impulse oscillometry (IOS), diffusion capacity (DLCO) with partition into membrane diffusion (DM) and capillary blood volume (VC), and cardiac MRI (n = 24). Alveolar-capillary membrane efficiency was assessed by calculation of DM/VC. MEASUREMENTS AND MAIN RESULTS: Mean age was 45+/-12 years; mean BMI was 44.8+/-7 kg/m2. Vital capacity was 88+/-13% predicted with reduction in functional residual capacity (58+/-12% predicted). Despite normal DLCO (98+/-18% predicted), VC was elevated (135+/-31% predicted) while DM averaged 94+/-22% predicted. DM/VC varied from 0.4 to 1.4 with high values reflecting recruitment of alveolar membrane and low values indicating alveolar membrane dysfunction. The most abnormal IOS (R5 and X5) occurred in subjects with lowest DM/VC (r2 = 0.31, p<0.001; r2 = 0.34, p<0.001). Cardiac output and index (cardiac output / body surface area) were directly related to DM/VC (r2 = 0.41, p<0.001; r2 = 0.19, p = 0.03). Subjects with lower DM/VC demonstrated a cardiac output that remained in the normal range despite presence of obesity. CONCLUSIONS: Global dysfunction of the distal lung (alveolar membrane and distal airway) is associated with pulmonary vascular congestion and failure to achieve the high output state of obesity. Pulmonary vascular congestion and consequent fluid transudation and/or alterations in the structure of the alveolar capillary membrane may be considered often unrecognized causes of airway dysfunction in obesity.