A novel in vitro assay for assessing efficacy and toxicity of antifungals using human leukemic cells infected with Candida albicans

Aims This study describes a novel in vitro assay that simultaneously determines antifungal efficiency and host cell toxicity using suspensions of human leukemic cells (HL-60) infected with Candida albicans. Methods and Results The effect of Candida infection on host cell viability was evaluated by microscopy of trypan blue stained cells and lactate dehydrogenase (LDH) activity. The in vitro ‘drug potency assay’ utilized the Cell Counting Kit-8 and measured post antifungal treatment viability of Candida-infected HL-60 cells and ability of the antifungal to prevent infection. LDH activity showed that 42% ± 4.0 and 85.3% ± 7.40 of HL-60 cells were killed following Candida infection at multiplicity of infection (MOI) of 1:1 and 1:5, respectively. Using the assay, the antifungal nystatin (0.78-25 μmol l−1) was found to inhibit C. albicans infection as seen by significantly increased viability of HL-60 cells. Using the assay, cytotoxicity of nystatin towards infected HL-60 cells was evident at higher concentrations and this was also confirmed by propidium iodide staining. Conclusions An assay using undisturbed cell suspension conditions was successfully developed for assessing selectivity of antifungal therapy in the host-Candida environment. Significance and Impact of the Study The assay employing Candida infection of host cell suspensions represents a promising method for testing interactions of antifungal compounds with both fungal and host cells