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

Abstract

Aims: This study describes a novel in vitro assay that simultaneously determines antifungal efficiency and host cell toxicity using suspensions of human leukaemic cells (HL-60) infected with Candida albicans.

Methods and results: The effect of Candida infection on host cell viability was evaluated by the 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 the ability of the antifungal treatment 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 the multiplicity of infection (MOI) of 1 : 1 and 1 : 5, respectively. The antifungal nystatin (0·78-25 μmol l(-1) ) was found to inhibit C. albicans infection as seen by the significantly increased viability of HL-60 cells. 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 the selectivity of the 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.

Keywords: antimicrobials; fungi; infection; mycology; nystatin.