Establishing a Pulmonary Aspergillosis fumigatus infection in Neutropenic mice

Pulmonary aspergillosis is a life-threatening infection of immunocompromised individuals caused by Aspergillus spp., particularly Aspergillus fumigatus. These patients are immunosuppressed with steroids, anti-rejection agents for transplants and/or anticancer drugs, such as cyclophosphamide which targets the bone marrow cells and induces neutropenia. Neutropenia is one of the highest risk factors for contracting pulmonary aspergillosis. Previous pulmonary aspergillosis studies in our laboratory have investigated the efficacy of different drugs using mice immunosuppressed with a steroid. The focus of this study was to establish a pulmonary aspergillosis infection in neutropenic, cyclophosphamide treated animals for future drug testing. Mice (n=8/gp) were given cyclophosphamide intraperitoneally (150mg/kg on d-4 and d+2, 100mg/kg on d-1 relative to challenge), and challenged intranasally d0 with varying concentrations of A. fumigatus (ATCC 13073) (1ex10^5 to 2ex10^7 spores/mouse). Mice were evaluated for morbidity and disease signs to d+16, lungs from moribund animals collected and fungal burden (CFU/g lung) determined by plating lung homogenates on Sabouraud's agar. A challenge dose of 1X10^6 spores/mouse was the most effective in establishing the pulmonary infection based on high levels of fungus in the lungs and morbidity of the animals occurring on d+3 which would enable the mice to receive at least 3 days of drug dosing (d0,d+1,d+2). The use of this cyclophosphamide murine model of pulmonary aspergillosis is clinically relevant and can now be used for studying anti-Aspergillus treatments.