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Comparative transcriptomics of Aspergillus fumigatus strains upon exposure to human airway epithelial cells.

ABSTRACT: Aspergillus fumigatus is an opportunistic, ubiquitous, saprophytic mould that can cause severe allergic responses in atopic individuals as well as life-threatening infections in immunocompromised patients. A critical step in the establishment of infection is the invasion of airway epithelial cells by the inhaled fungi. Understanding how A. fumigatus senses and responds to airway cells is important to understand the pathogenesis of invasive pulmonary aspergillosis. Here, we analysed the transcriptomes of two commonly used clinical isolates, Af293 and CEA10, during infection of the A549 type II pneumocyte cell line in vitro. We focused our RNA-seq analysis on the core set of genes that are present in the genomes of the two strains. Our results suggest that: (a) A. fumigatus does not mount a conserved transcriptional response to airway epithelial cells in our in vitro model and (b) strain background and time spent in the tissue culture media have a greater impact on the transcriptome than the presence of host cells. Our analyses reveal both common and strain-specific transcriptional programmes that allow for the generation of hypotheses about gene function as it pertains to pathogenesis and the significant phenotypic heterogeneity that is observed among A. fumigatus isolates.

SUBMITTER: Watkins TN

PROVIDER: S-EPMC5857381 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Comparative transcriptomics of Aspergillus fumigatus strains upon exposure to human airway epithelial cells.

Watkins Tonya N TN Liu Hong H Chung Matthew M Hazen Tracy H TH Dunning Hotopp Julie C JC Filler Scott G SG Bruno Vincent M VM

Microbial genomics 20180118 2

Aspergillus fumigatus is an opportunistic, ubiquitous, saprophytic mould that can cause severe allergic responses in atopic individuals as well as life-threatening infections in immunocompromised patients. A critical step in the establishment of infection is the invasion of airway epithelial cells by the inhaled fungi. Understanding how A. fumigatus senses and responds to airway cells is important to understand the pathogenesis of invasive pulmonary aspergillosis. Here, we analysed the transcrip ...[more]

PMID: 29345613

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Project description:BackgroundAspergillus fumigatus is the most common etiologic agent of invasive aspergillosis in immunocompromised patients. Several studies have addressed the mechanism involved in host defense but only few have investigated the pathogen's response to attack by the host cells. To our knowledge, this is the first study that investigates the genes differentially expressed in conidia vs hyphae of A. fumigatus in response to neutrophils from healthy donors as well as from those with chronic granulomatous disease (CGD) which are defective in the production of reactive oxygen species.Methodology/principal findingsTranscriptional profiles of conidia and hyphae exposed to neutrophils, either from normal donors or from CGD patients, were obtained by using the genome-wide microarray. Upon exposure to either normal or CGD neutrophils, 244 genes were up-regulated in conidia but not in hyphae. Several of these genes are involved in the degradation of fatty acids, peroxisome function and the glyoxylate cycle which suggests that conidia exposed to neutrophils reprogram their metabolism to adjust to the host environment. In addition, the mRNA levels of four genes encoding proteins putatively involved in iron/copper assimilation were found to be higher in conidia and hyphae exposed to normal neutrophils compared to those exposed to CGD neutrophils. Deletants in several of the differentially expressed genes showed phenotypes related to the proposed functions, i.e. deletants of genes involved in fatty acid catabolism showed defective growth on fatty acids and the deletants of iron/copper assimilation showed higher sensitivity to the oxidative agent menadione. None of these deletants, however, showed reduced resistance to neutrophil attack.ConclusionThis work reveals the complex response of the fungus to leukocytes, one of the major host factors involved in antifungal defense, and identifies fungal genes that may be involved in establishing or prolonging infections in humans.

Project description:During the initiation of invasive aspergillosis, inhaled Aspergillus fumigatus conidia are deposited on the epithelial cells lining the bronchi, terminal bronchioles, and alveoli. While the interactions of A. fumigatus with bronchial and type II alveolar cell lines have been investigated in vitro, little is known about the interactions of this fungus with terminal bronchiolar epithelial cells. Using the HSAEC1-KT human small airway epithelial (HSAE) cell line, we developed an in vitro model to study the interaction of two strains of A. fumigatus with these cells. We then compared the interactions of A. fumigatus with the A549 type II alveolar epithelial cell line and the HSAE cell line. We found that A. fumigatus conidia were poorly endocytosed by A549 cells, but avidly endocytosed by HSAE cells. A. fumigatus germlings invaded both cell types by induced endocytosis, but not by active penetration. A549 cell endocytosis of A. fumigatus was independent of fungal viability, more dependent on host microfilaments than microtubules, and induced by A. fumigatus CalA interacting with host cell integrin α5β1. By contrast, HSAE cell endocytosis required fungal viability, was more dependent on microtubules than microfilaments, and did not require CalA or integrin α5β1. HSAE cells were more susceptible than A549 cells to damage caused by direct contact with killed A. fumigatus germlings and by secreted fungal products. In response to A. fumigatus infection, A549 cells secreted a broader profile of cytokines and chemokines than HSAE cells. Taken together, these results demonstrate that studies of HSAE cells provide complementary data to A549 cells and thus represent a useful model for probing the interactions of A. fumigatus with bronchiolar epithelial cells in vitro. Importance During the initiation of invasive aspergillosis, Aspergillus fumigatus interacts with the epithelial cells that line the airways and alveoli. Previous studies of A. fumigatus-epithelial cell interactions in vitro used either large airway epithelial cell lines or the A549 type II alveolar epithelial cell line; the interactions of fungi with terminal bronchiolar epithelial cells were not investigated. Using the TERT-immortalized human small airway epithelial HSAEC1-KT (HSAE) cell line, we developed an in vitro model of the interactions of A. fumigatus with bronchiolar epithelial cells. We discovered that A. fumigatus invades and damages A549 and HSAE cell lines by distinct mechanisms. Also, the proinflammatory responses of the cell lines to A. fumigatus are different. These results provide insight into how A. fumigatus interacts with different types of epithelial cells during invasive aspergillosis and demonstrate that HSAE cells are useful in vitro model for investigating the interactions of this fungus with bronchiolar epithelial cells.

Project description:BackgroundChronic Obstructive Pulmonary Disease (COPD) is a progressive lung disease characterized by chronic inflammation upon inhalation of noxious particles, e.g., cigarette smoke. FAM13A is one of the genes often found to be associated with COPD, however its function in the pathophysiology of COPD is incompletely understood. We studied its role in airway epithelial barrier integrity and cigarette smoke-induced epithelial responses.Materials and methodsProtein level and localization of FAM13A was assessed with immunohistochemistry in lung tissue from COPD patients and non-COPD controls. In vitro, FAM13A expression was determined in the absence or presence of cigarette smoke extract (CSE) in primary airway epithelial cells (AECs) from COPD patients and controls by western blotting. FAM13A was overexpressed in cell line 16HBE14o- and its effect on barrier function was monitored real-time by electrical resistance. Expression of junctional protein E-cadherin and β-catenin was assessed by western blotting. The secretion of neutrophil attractant CXCL8 upon CSE exposure was measured by ELISA.ResultsFAM13A was strongly expressed in airway epithelium, but significantly weaker in airways of COPD patients compared to non-COPD controls. In COPD-derived AECs, but not those of controls, FAM13A was significantly downregulated by CSE. 16HBE14o- cells overexpressing FAM13A built up epithelial resistance significantly more rapidly, which was accompanied by higher E-cadherin expression and reduced CSE-induced CXCL8 levels.ConclusionOur data indicate that the expression of FAM13A is lower in airway epithelium of COPD patients compared to non-COPD controls. In addition, cigarette smoking selectively downregulates airway epithelial expression of FAM13A in COPD patients. This may have important consequences for the pathophysiology of COPD, as the more rapid build-up of epithelial resistance upon FAM13A overexpression suggests improved (re)constitution of barrier function. The reduced epithelial secretion of CXCL8 upon CSE-induced damage suggests that lower FAM13A expression upon cigarette smoking may facilitate epithelial-driven neutrophilia.

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Comparative transcriptomics of Aspergillus fumigatus strains upon exposure to human airway epithelial cells.

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Comparative transcriptomics of Aspergillus fumigatus strains upon exposure to human airway epithelial cells.

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