Development of a Clinically Relevant, Reproducible Inhalational Model of Invasive aspergillosis.
Background: The study of the pathogenesis of invasive aspergillosis (IA) has been limited by the lack of an easily reproducible animal model that recapitulates human infection. Current models of intravenous and intranasal infection rely on high doses of conidia and do not deliver the infectious inoculum directly to the alveolus. Existing inhalational models have been limited by variability in infecting inoculum and by a limited capacity of the inhalation apparatus. We have developed a murine inhalational model of IA that is inexpensive, reproducible and recapitulates human IA. Methods: Female Balb/c mice were immunocompromised with cyclophosphamide 200mg/kg and cortisone acetate 250mg/kg on day -2 and day +2 of infection. To achieve infection, up to 40 mice were placed in an aerosol chamber for 1 hour. The inoculum was introduced using by aerosolizing a suspension of A. fumigatus AF293 conidia with a nebulizer designed to produce a particle size of 2.5 microns. Mice were infected with varying doses of conidia. Results: Using this regimen, neutropenia could be maintained for 10 days. By day 10 of infection, an LD80 was obtained by aerosolizing a suspension of 5 X 109 conidia, which resulted in an average inoculum of 1-3 X103 conidia per mouse. This inoculum was highly reproducible between experiments. Histopathology of mice infected by inhalation demonstrated invasive pulmonary disease with prominent vascular invasion. Treatment with Amphotericin B at 3mg/kg intraperitoneally reduced overall mortality by 50%. Conclusions: We have developed a novel model of murine IA that is reproducible, inexpensive and clinically relevant. The use of this chamber to test the virulence of A. fumigatus mutants is underway.
Full conference title:
43rd Interscience Conference on Antimicrobial Agents