In vitro model of pulmonary candidiasis for testing novel therapeutics.

Invasive candidiasis is one of the most common causes of hospital-acquired blood infections, with the most common cause being Candida albicans. These bloodstream infections often lead to long hospital stays and have a high mortality rate. Once C. albicansenters the bloodstream it can disseminate and invade many organs of the body, including the lungs, where it can inhibit function and cause further complications. Furthermore, C. albicansis commonly isolated from the lungs of cystic fibrosis patients and often causes coinfection in patients with severe COVID-19. Current antifungal drugs exhibit high toxicity, poor water solubility, and are ineffective against some strains of C. albicans due to antifungal resistance, creating an urgent need for new antifungal therapeutics. Here, we have developed a customizable in vitroplatform to study the interaction between rat lung microvascular endothelial cells (ECs), C. albicansSC5314, and novel liposomes encapsulating the antifungal drug anidulafungin. Liposome formulations composed of hydrogenated soy phosphatidylcholine, phosphatidylglycerol, cholesterol, and α-tocopherol were fabricated containing three different % wt/wt concentrations of anidulafungin (0.31, 1.55, and 3.10, or 1x, 5x and 10x, respectively). The minimum inhibitory concentrations (MICs) of the different liposome formulations for C. albicans were determined using a microdilution assay. After 24 hours of exposure, the MICs were found to be 12.50, 6.25, and 1.56 μg/mL for 1x, 5x, and 10x liposome formulations, respectively. Cell Counting Kit 8 was used to determine EC viability after 24-hour treatment with the different liposome formulations. The 1x and 5x anidulafungin liposome formulations showed no significant decrease in viability up to the maximum liposome concentration tested (50 μg/mL), with the 10x formulation causing a slight but significant decrease in viability. The 1x and 5x anidulafungin liposomes were then assessed at 6.25 and 12.5 μg/mL in a co-culture setting. C. albicans were seeded onto established EC monolayers and were allowed to form hyphae, which is the invasive form. After the two hours, the co-cultures were treated with the antifungal liposomes. Treatment with the liposomes reduced hyphae formation and prevented C. albicansovergrowth within four hours of exposure, with the 5x anidulafungin liposome at 12.5 μg/mL showing the strongest change. These data suggest that these novel antifungal liposomes have the potential to treat pulmonary candidiasis without the toxic side effects associated with current antifungal drugs.