Characterization of BBB permeability in a preclinical model of cryptococcal meningoencephalitis using magnetic resonance imaging

Cryptococcus neoformans meningoencephalitis (CNME) is a leading fungal cause of death among acquired immunodeficiency syndrome patients. Innovative preclinical systems that permit high throughput in vivo evaluation of novel agents are desperately needed. Magnetic resonance imaging (MRI) was evaluated as a tool to develop a rat model of CNME and to quantify noninvasively blood-brain barrier (BBB) disruption secondary to this disease. The aim of this study was to identify MRI changes compared with histopathology and fungal burden measurements as potential biomarkers. A well-characterized strain of C neoformans (CN) var grubii was used to infect rats using intravenous inoculation. An inoculum-finding study was performed by infecting rats with 103, 105, and 107 colony-forming units (CFUs). Animals underwent dynamic MRI on days 4 and 7 after inoculation. An inoculum-confirming study was performed by infecting rats with 105, 106, and 107 CFU and fungal burden was determined in the brain, lung, and spleen. Animals infected with 107 CFU of CN developed lesions that appeared hyperintense on T2-weighted images on day 4. The histopathology results correlated well with MRI data. Diffusion weighted and permeability estimates were 1.4 and 6.1-fold higher, respectively, in lesions compared with healthy tissue. Magnetic resonance imaging is a promising preclinical tool to evaluate effects of antifungal and adjunctive agents.