Development of a Mouse Model of Coccidioidomycosis Using an Inhalation Exposure System

Coccidioides species are thermally dimorphic fungal pathogens that cause coccidioidomycosis (Valley Fever) primarily in North and South America. Coccidioides grow as hyphae that differentiate into arthroconidia, which can be aerosolized upon soil disturbance, and inhaled by the mammalian host to cause pulmonary infections with occasional dissemination to other organs. In the context of mouse models, current methods of infection include intranasal, intravenous, and intraperitoneal delivery of the arthroconidia into mice. To explore an aerosol route of infection, we compared the intranasal method with aerosolization using the Glass-Col Inhalation Exposure System (IES). Infection with a dose of 2 × 10⁶ CFU/mL, nebulized in 5 mL of PBS, but not in water, was able to infect mice, albeit inconsistently, compared to intranasal challenge. Arthroconidia were detected inside the IES after the nebulization and decontamination cycles. These studies highlight some of the challenges with aerosolization of Coccidioides arthroconidia and serve as a reminder about biosafety considerations for use of the IES to aerosolize pathogens.