The A. fumigatus rhbA gene encodes a homologue of rheb, a ras-family member. To determine the effect of rhbA deletion on the pathology associated with invasive aspergillosis, a murine model of pulmonary aspergillosis was used. Mice were immunosupressed with cyclophosphamide and cortisone acetate and inoculated intranasally with 5X104 conidia of the wild type, &Delta_upper;rhbA strain or reconstituted mutant. Two-three animals inoculated with each of the three strains were sacrificed at four and seven days post-inoculation. A portion of lung from each animal was used to assay fungal burden by measurement of CFU/mL lung homogenate and chitin content. A portion of lung from the same animals was fixed for histology and three sections from each animal were mounted and stained with PAS. Images of fungal lesions were captured with an SGI IRIS indigo workstation, and images were analyzed using Scion Image software. The average area of fungal lesions in lung section from each group of animals was measured. The fungal lesion was defined as the border of visible hyphal growth, excluding surrounding infarct and necrosis. No significant difference in fungal burden was seen among the three groups by measurement of CFU and chitin content. However, image analysis revealed a significant decrease in average fungal lesion area in mice inoculated with the &Delta_upper;rhbA strain compared to those inoculated with the wild type or reconstituted strain on both day 4 and 7 post-inoculation. These results suggest that the &Delta_upper;rhbA strain has an impaired ability to cause the pathology associated with invasive aspergillosis. This study also demonstrates the potential utility of image analysis as a measure of fungal burden in animal models of invasive aspergillosis.
Full conference title:
American Society for Microbiology General Meeting
- ASM 102nd (2002)