Biology subjects

Huffnagle, G. B.

Publications and source records attributed to Huffnagle, G. B..

3 recordsLinked to original sources

bioRxiv2025

Alveolar metabolite availability facilitates secondary infection by Pseudomonas aeruginosa in acutely injured lungs

Secondary bacterial pneumonia is a frequent complication of acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). Prior efforts to explain increased pneumonia risk in ALI/ARDS have focused on impaired immunity and bacterial virulence, but have overlooked the potential contribution of ecological factors within acutely injured lungs. Here, we show that lung injury profoundly alters the alveolar metabolic microenvironment, a change that can be exploited by a common pneumonia pathogen. In mice and humans, we found that growth of Pseudomonas aeruginosa (the most prominent respiratory pathogen in a retrospective cohort of patients with ARDS) is enhanced by increased alveolar concentrations of multiple ALI/ARDS-associated metabolites, which are derived from the blood and cross the compromised alveolar-capillary barrier during alveolar leak. Collectively, this work reveals an ecological mechanism by which pathogens may survive in the injured lung microenvironment and identifies new potential targets for secondary pneumonia prevention and treatment.

microbiology↗

bioRxiv2024

Lung Microbiome Intervention Attenuates Herpesvirus-Induced Post-HCT Pulmonary Fibrosis Through PD-L1 Upregulation on Dendritic Cells

Alterations in the lung microbiome frequently accompany adverse pulmonary outcomes. Hematopoietic cell transplantation (HCT) markedly affects the lung microbiome corresponding with a high incidence of post-HCT pulmonary complications. In a preclinical mouse model of HCT, we observed a reduction in Lactobacillus johnsonii within the lung microbiome following transplantation. Intranasal administration of live or heat-killed (HK) L. johnsonii at low doses reduced gammaherpesvirus-induced pulmonary fibrosis in HCT mice, in which IL-17A plays an essential role. HK L. johnsonii treatment of HCT mice suppressed inflammatory cytokine production by lung macrophages and decreased Il17a expression in T helper 17 (Th17) cells. HK L. johnsonii increased PD-L1 expression on the surface of type II conventional dendritic cells (cDC2) in HCT mice and in vitro in bone marrow-derived dendritic cells (BMDCs). HK L. johnsonii-exposed BMDCs also inhibited IL-17A secretion from co-cultured Th17 cells in a PD-1-dependent manner. Notably, when HK L. johnsonii was administered to HCT mice reconstituted with bone marrow cells from PD-1 knockout (KO) mice, which lack a PD-L1 mediated response, HK L. johnsonii-mediated reduction of pulmonary fibrosis was negated. Collectively, our findings demonstrate that HK L. johnsonii mitigates herpesvirus-induced pulmonary fibrosis in HCT mice by modulating cDC2 surface expression of PD-L1, which subsequently suppresses Il17a expression in Th17 cells, pointing towards a potential postbiotic-based strategy for immunomodulation to address pulmonary complications of HCT.

immunology↗

bioRxiv2020

Application of an ecology-based analytic approach to discriminate signal and noise in low-biomass microbiome studies: whole lung tissue is the preferred sampling method for amplicon-based characterization of murine lung microbiota

BackgroundLow-biomass microbiome studies (such as those of the lungs, placenta, and skin) are vulnerable to contamination and sequencing stochasticity, which obscure legitimate microbial signal. Since low-biomass microbiome fields have had variable success in establishing the reality and clinical significance of identified microbiota, we sought to develop and apply an analytical approach to discriminate signal from noise in low-biomass microbiome studies. We used this approach to determine the optimal sampling strategy in murine lung microbiome studies, which will be essential for future mechanistic lung microbiome research. MethodsUsing a novel, ecology-based analytic approach, we compared bacterial DNA from the lungs of healthy adult mice collected via two common sampling approaches: homogenized whole lung tissue and bronchoalveolar lavage (BAL) fluid. We quantified bacterial DNA using droplet digital PCR, characterized bacterial communities using 16S rRNA gene sequencing, and systematically assessed the quantity and identity of bacterial DNA in both specimen types. We compared bacteria detected in lung specimens to each other and to potential source communities: negative (background) control specimens and paired oral samples. FindingsBy all measures, whole lung tissue in mice contained greater bacterial signal and less evidence of contamination than did BAL fluid. Relative to BAL fluid, whole lung tissue exhibited a greater quantity of bacterial DNA, distinct community composition, decreased sample-to-sample variation, and greater biological plausibility when compared to potential source communities. In contrast, bacteria detected in BAL fluid were minimally different from those of procedural, reagent, and sequencing controls. InterpretationAn ecology-based analytical approach discriminates signal from noise in low-biomass microbiome studies and identifies whole lung tissue as the preferred specimen type for murine lung microbiome studies. Sequencing, analysis, and reporting of potential source communities, including negative control specimens and contiguous biological sites, is crucial for biological interpretation of low-biomass microbiome studies, independent of specimen type. FundingNational Institutes of Health

microbiology↗