Session: Poster Session: Experimental Mycology
Sunday, October 26, 2008: 12:00 AM
Room: Hall C
Background: Development of brain lesions due to CNME is associated with poor prognosis in HIV patients (PLoS ONE 2008;3(4):e1950). We evaluated the role of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) as a NI biomarker of BBB disruption using magnetic resonance imaging (MRI) in a rat model of CNME. Methods: A 48-hour (H) culture of Cryptococcus neoformans (CN) serotype A [ATCC 208821, H99] was used to generate an inoculum of 108 colony forming units (CFU)/mL. A 0.1 mL (107 CFU) inocula were injected into five male 250-300 g Fischer F344 rats via the lateral tail vein. MRI was performed at baseline (pre-infection) and on day 4 post-infection using a 4.7T Biospec® MRI scanner with a small bore linear radiofrequency coil. MRI studies at baseline included T2-weighted-3 dimensional rapid acquistion with relaxation enhancement. This structural imaging protocol was repeated on day 4 along with a multiple graphical analysis (MGA) method. The MGA protocol included bolus intravenous injection via a catheter of 0.2 mM/kg of Gd-DTPA with a rapid T1 mapping protocol of 14 time-points over 45 minutes. Apparent diffusion coefficient (ADC) and permebaility coefficient (PC) maps were generated and compared within rats using the paired t-test. Rats were sacrificed on day 5, and brain histology of the optic chiasm, pons, and cerebellum were compared to MRI data. Results: All rats had formation of numerous brain lesions on day 4 noted by high signal intensity on T2-weighted images. The average ADC values were 39% higher (p<0.05) on day 4 relative to baseline. The mean ± SD PC was significantly (p<0.05) higher within lesions 2.06 ± 0.42 mL/(g*min) compared to normal tissue 0.34 ± 0.10 mL/(g*min). Brain histology matched MRI data with demonstration of classic ‘soap-bubble’ non-inflammatory cystic lesions that were filled with CN. Conclusions: CNME disrupts rat BBB and is detectable by Gd-DTPA enhanced MRI. This suggests that novel antifungals agents with high molecular weights should not be discounted as possible treatments of CNME.