Detection of Low Oxygen Microenvironments in a Murine Model of Invasive Pulmonary Aspergillosis Using Pimonidazole

Infection tissue microenvironments are dynamic, complex, and play a critical role in host-microbe interaction outcomes. A crucial parameter of the infection site microenvironment is oxygen. Both host and microbial cell physiology is significantly impacted by the availability of oxygen. When oxygen tensions drop to levels that do not meet the metabolic demands of the cell, a hypoxia response ensues. In numerous host-microbe studies, it has now been observed that the host and microbial hypoxia response plays a critical role in disease outcomes. However, in most pathosystems, spatial and temporal oxygen dynamics throughout the infection remain ill defined. Here, we detail a protocol for detecting low oxygen environments in tissue in a murine model of invasive pulmonary aspergillosis. The protocol utilizes mice immune compromised with a high dose of steroid and challenged via the aerosol route with conidia of the major human fungal pathogen Aspergillus fumigatus. Qualitative analysis of oxygen levels at the site of infection in the murine lung is accomplished with pimonidazole-mediated adduct detection via immunohistochemistry. The protocol is adaptable to other host-microbe interaction models.