Quantitative real-time polymerase chain-reaction assay allows characterization of Pneumocystis infection in immunocompetent mice

Pneumocystis causes pneumonia in immunodeficient hosts but also likely causes infection in healthy hosts. To characterize infection in healthy mice, we developed and validated a real-time polymerase chain reaction assay for quantitation of Pneumocystis carinii f. sp. muris. In healthy mice exposed to Pneumocystis-infected animals, organisms were first detected at 2 - 3 weeks, peaked at 5 - 6 weeks, and were cleared by 7 - 9 weeks. The peak organism load in healthy animals was 2 - 3 logs lower than that in immunodeficient animals. This approach should facilitate studies of anti-Pneumocystis immune mechanisms in healthy hosts and provide insights into the development of Pneumocystis pneumonia in immunodeficient hosts.