OBJECTIVETo explore the feasibility of inducing fungal infection by Cryptococcus neoformans aerosol inhalation in immunosuppressed Balb/c mice.

METHODSTwenty-four Balb/c mice were randomized into cyclophosphamide (CTX) group and control group (n=12). The mice in CTX group were subject to inhalation of Cryptococcus neoformans aerosol prepared using a ultrasonic nebulizer 4 days after intraperitoneal CTX injection, and the control mice received the inhalation only. The leukocyte count and changes in appetite, body weight, and behaviors of the mice were observed after the treatments. On days 3 and 7 after the inoculation, the mice were sacrificed to analyze the fungal counts in brain and lung tissue homogenates and examine the pulmonary pathologies.

RESULTSCTX injection caused lowered appetite and body weight loss in the mice, and significantly reduced the leukocyte counts (2.77∓0.45 vs 8.26∓0.56, P<0.05). At days 3 and 7 after inoculation, the Cryptococci load in the lungs increased obviously in CTX group with a colony-forming unit (CFU) of the lungs of 271.67∓122.22 and 41.67∓0.28, respectively, significantly higher than that in the control group (60.00∓43.36 and 3.00∓5.30, respectively, P<0.05). In CTX group, the CFU was 10.17∓5.42 and 9.17∓6.34 in the peripheral blood and 6.83∓4.92 and 11.00∓5.44 in the brain tissue at days 3 and 7, respectively, whereas no Cryptococci was detected in the peripheral blood or in the brain tissue in the control group. Pathological examination of the lungs revealed destruction of normal alveolar structure in CTX group, with numerous infiltrating inflammatory cells and visible yeast.

CONCLUSIONInhalation of Cryptococcus neoformans aerosol can cause fungal infection in the lungs of immunosuppressed Balb/c mice.