Gene expression profiles of human dendritic cells interacting with Aspergillus fumigatus in a bilayer model of the alveolar epithelium/endothelium interface.

The initial stages of the interaction between the host and Aspergillus fumigatus at the alveolar surface of the human lung are critical in the establishment of aspergillosis. Using an in vitro bilayer model of the alveolus, including both the epithelium (human lung adenocarcinoma epithelial cell line, A549) and endothelium (human pulmonary artery epithelial cells, HPAEC) on transwell membranes, it was possible to closely replicate the in vivo conditions. Two distinct sub-groups of dendritic cells (DC), monocyte-derived DC (moDC) and myeloid DC (mDC), were included in the model to examine immune responses to fungal infection at the alveolar surface. RNA in high quantity and quality was extracted from the cell layers on the transwell membrane to allow gene expression analysis using tailored custom-made microarrays, containing probes for 117 immune-relevant genes. This microarray data indicated minimal induction of immune gene expression in A549 alveolar epithelial cells in response to germ tubes of A. fumigatus. In contrast, the addition of DC to the system greatly increased the number of differentially expressed immune genes. moDC exhibited increased expression of genes including CLEC7A, CD209 and CCL18 in the absence of A. fumigatus compared to mDC. In the presence of A. fumigatus, both DC subgroups exhibited up-regulation of genes identified in previous studies as being associated with the exposure of DC to A. fumigatus and exhibiting chemotactic properties for neutrophils, including CXCL2, CXCL5, CCL20, and IL1B. This model closely approximated the human alveolus allowing for an analysis of the host pathogen interface that complements existing animal models of IA.

RT-qPCR detection of Aspergillus fumigatus RNA in vitro and in a murine model of invasive aspergillosis utilizing the PAXgene® and Tempus™ RNA stabilization systems.

Molecular diagnosis of invasive aspergillosis (IA) is a potentially life-saving tool in the care of at-risk individuals. To date, the development of PCR-based diagnostic tests has been hampered by the lack of standardization in the methods for such critical activities. In this study, we used both spiked volunteer blood samples and a murine model of IA to test the utility of the PAXgene and Tempus systems for stabilization and isolation of fungal RNA from blood as part of an evaluation of a new diagnostic strategy. In spiking experiments, RNA isolation followed by RT-qPCR that targeted the 18S gene was compared to a standard DNA isolation and qPCR assay that targeted the ITS ribosomal region. We demonstrated that both PAXgene and Tempus RNA stabilization and extraction systems followed by RT-qPCR had similar performance in detecting fungal RNA in blood samples from Aspergillus fumigates-infected mice. In spiked samples, the Tempus system performed better than the PAXgene system as it detected 100% of all samples spiked with 10 or 20 germinated Aspergillus conidia/ml blood sample as compared to the PAXgene system which detected 33% and 56% of the samples spiked with 10 or 20 conidia/ml, respectively. The stabilization of fungal nucleic acids in blood samples and its efficient isolation by a commercial method is an important step in the development of standardized molecular diagnostic tools that are needed to improve the outcomes for individuals with IA.