A High-Throughput Screening Assay for Fungicidal Compounds against Cryptococcus neoformans

Cryptococcus neoformans is a pathogenic fungus that causes meningitis worldwide, particularly in human immunodeficiency virus (HIV)-infected individuals. Although amphotericin B is the gold standard treatment for cryptococcal meningitis, the toxicity and inconvenience of intravenous injection emphasize a need for development of new anticryptocccal drugs. Recent data from humans and animal studies suggested that a nutrient-deprived host environment may exist in cryptococcal meningitis. Thus, a screening assay for identifying fungicidal compounds under nutrient-deprived conditions may provide an alternative strategy to develop new anticryptococcal drugs for this disease. A high-throughput fungicidal assay was developed using a profluorescent dye, alamarBlue, to detect residual metabolic activity of C. neoformans under nutrient-limiting conditions. Screening the Library of Pharmacologically Active Compounds (LOPAC) with this assay identified a potential chemical scaffold, 10058-F4, that exhibited fungicidal activity in the low micromolar range. These results thus demonstrate the feasibility of this alamarBlue-based assay for high-throughput screening of fungicidal compounds under nutrient-limiting conditions for new anticryptococcal drug development.