Purpose: Colonization of airways by Aspergillus fumigatus hyphae in immunocompetent patients with chronic pulmonary disease leads to worsening of lung function and more frequent hospitalizations. Current animal models mimic allergic bronchopulmonary aspergillosis by inhalation of A. fumigatus crude extract or antigens and does not permit the study of the interactions of live intact organisms with host cells. Attempts to induce colonization of A. fumigatus in healthy mice have been unsuccessful, as conidia are rapidly cleared from airways. Here we present a novel murine model, where airways of immunocompetent mice were colonized with live A. fumigatus hyphae. Methods: Healthy C57BL/6 mice were intratracheally inoculated with 5 x 105 A. fumigatus conidia embedded within agar beads. Mice were sacrificed at days 14, 21 and 28 post-infection during which blood, bronchoalveolar lavage (BAL) fluid, as well as lungs for either histopathology or homogenates, were collected. Fungal burden was measured using the BioRad Platelia GM assay and by histopathological assessment. Cytokine expression in homogenates and BAL fluid was examined by Luminex® Multiplex assay. The levels of IgE from plasma were determined by ELISA. Results: Histopathological examination showed that A. fumigatus hyphae persisted in the lungs of mice up to 28 days post-infection without invasive disease or mortality. Determination of galactomannan in lung homogenates confirmed the presence of hyphae during this period. Fungal lesions within the airways were surrounded by a robust cellular inflammatory reaction, mostly consisting of neutrophils. This inflammatory response was not seen in mice infected with sterile agar beads or A. fumigatus conidia in suspension alone. Elevated levels of neutrophils were also seen in cytospins of A. fumigatus-bead infected BAL fluid. Whole lung cytokine analysis from mice infected with A. fumigatus-beads revealed an increase in pro-inflammatory molecules (e.g. IL-1, MCP-1, GM-CSF and MIP-1 alpha) that was not seen in any of the other groups. Futhermore, IgE levels in plasma were significantly elevated in mice infected with A. fumigatus beads but not in the other groups. Conclusions: Chronic airway colonization with live A. fumigatus in immunocompetent mice can be achieved using infection with conidia embedded within agar beads. This colonization is associated with increased cellular inflammation, production of pro-inflammatory cytokines and elevated IgE levels, suggesting this may provide a useful in vivo model system to study the pathogenesis of A. fumigatus-induced chronic airways disease.
Full conference title:
4th Advances Against Aspergillosis
- AAA 4th (2010)