Quantification of the APE2 gene expression level in Candida albicans clinical isolates from patients with diagnosed fungal infections.

The production of hydrolytic enzymes is considered a key virulence determinant of Candida albicans. Aminopeptidase 2 (Ape2) facilitates the penetration of C. albicans into the host tissue, by providing free amino acids to support fungal growth and proliferation. The objective of this study was to estimate the APE2 expression profile in C. albicans cells during invasion of the human epithelium. Sixty-one clinical fungal isolates and five reference strains were included in this study. The wild-type APE2 sequence was analyzed by polymerase chain reaction (PCR) amplification using genomic DNA from pathogenic isolates. Amplicons were verified in 1% agarose gel and visualized by illumination with ultraviolet (UV) light. The APE2 expression levels were analyzed with reverse transcription quantitative real-time PCR (RT-qPCR) and APE2 quantification was normalized against the reference gene in C. albicans cells grown in YEPD and during Caco-2 invasion. The APE2-specific PCR product band was found in all C. albicans and C. dubliniensis strains, but not in other common pathogenic fungi. APE2 transcript abundance was elevated in the clinical isolates growing on the Caco-2 cell line in comparison to their counterparts grown in YEPD. Our data indicate a potential role for Ape2 in the invasion of epithelial cells. APE2 expression is also strain-specific, and it is not related to isolation site or disease entity.