Novel inhalational murine model of invasive pulmonary aspergillosis

Abstract

We developed a novel model of invasive aspergillosis (IA) that recapitulates human disease. Mice were immunosuppressed with cyclophosphamide and cortisone acetate and then infected in an aerosol chamber. This procedure reproducibly delivered 1 x 10(3) to 3 x 10(3) conidia to the lungs. Lethal pulmonary IA developed over 2 weeks and was prevented by amphotericin B.

FIG. 1.

Inhalation infection apparatus. Inset panel depicts the compressed air-driven nebulizer connected to a channel across the top of the chamber. This channel leads to an opening located in the center of the chamber ceiling. Nebulized conidia enter the chamber through this orifice and are dispersed throughout the chamber. A door at the right end of the chamber permits access.

FIG. 2.

Duration of leukopenia induced by two doses of cyclophosphamide and cortisone acetate. Data are shown as mean leukocyte counts ± standard deviations. Five mice were sampled at each time point. The X denotes the days of administration of cyclophosphamide and cortisone acetate. WBC, white blood cells.

FIG. 3.

Survival of mice infected by inhalation and treated with two doses of immunosuppression. Results are the combination of three independent experiments (total n of 27 for each group). *, P of <0.001 by log-rank test compared with values for uninfected mice. ♦, uninfected mice; ▪, infected mice.

FIG. 4.

PAS-stained lung sections of mice infected with A. fumigatus by inhalation. (A) Lung tissue 7 days after inoculation showing a focal lesion of IA with invasion of a neighboring blood vessel indicated by the arrow (×100). (B) Higher magnification (×400) demonstrating complete penetration of the blood vessel wall by hyphae (arrow). (C) Lung tissue 10 days after inoculation (after leukocyte recovery) showing the formation of a parenchymal fungal abscess (×100). (D) Higher magnification (×400) demonstrating abundant hyphae surrounded by leukocytes.

FIG. 5.

Survival of mice infected with A. fumigatus and treated with AMB, combined results of two experiments, total n of 20 per group. *, P of <0.001 by log-rank test compared with values for mice receiving 5% dextrose agents. ♦, AMB at 3 mg/kg/day; ▪, vehicle (5% dextrose).