Effect of the echinocandin caspofungin on expression of Candida albicans secretory aspartyl proteinases and phospholipase in vitro

Abstract

Although the echinocandin caspofungin primarily inhibits the synthesis of cell wall 1,3-beta-D-glucan, its fungicidal activity could also potentially perturb the expression of virulence factors involved in the ability of Candida albicans to cause infection. Expression of the C. albicans secretory aspartyl proteinase (SAP) and phospholipase B (PLB) virulence genes was determined by reverse transcription-PCR after the addition of caspofungin to cells grown for 15 h in Sabouraud dextrose broth. In cells that remained viable, expression of SAP1 to SAP3, SAP7 to SAP9, and PLB1 was unaltered after exposure to fungicidal concentrations (4 to 16 micro g/ml) of caspofungin over a period of 7 h. However, expression of SAP5 increased steadily beginning 1 h after exposure to caspofungin. These results indicate that caspofungin is rapidly fungicidal against C. albicans, before any suppression of SAP or PLB1 gene expression can occur.

FIG. 1.

Plots of the number of C. albicans treated with different concentrations of caspofungin over time. The mean values for log₁₀ of the number of CFU per milliliter versus time for C. albicans strain LAM-1 tested against different concentrations of caspofungin. The following concentrations (in micrograms per milliliter) of caspofungin were used: 0 (control) (□), 0.0625 (▾), 0.125 (♦), 0.25 (•), 1 (▴), 4 (○), 8 (▵), and 16 (▪). Caspofungin was added to cultures in SDB after 15 h of incubation (A) or at the start of culture (B). Representative results are shown from four (A) and two (B) independent experiments.

FIG. 2.

Expression of the SAP2, SAP5, and EFB1 genes of C. albicans over a period of 7 h after the addition of caspofungin (4 to 16 μg/ml) to cells grown for 15 h in SDB. Representative results are shown from two independent experiments. EFB1 was used as a positive control. Expression of the remaining SAP genes and PLB1 was similar to that of SAP2.