An in vitro evaluation of Candida tropicalis infectivity using human cell monolayers

Abstract

The aim of the present study was to investigate the interaction ofCandida tropicalis with three different human cell lines: TCC-SUP (epithelial cells from urinary bladder); HeLa (epithelial cells from cervical carcinoma); Caco-2 (epithelial cells from colorectal adenocarcinoma). In particular to assess the degree of cell damage and activity reduction induced by C. tropicalis adhesion and the role of SAPT gene expression in this process. Two C. tropicalis strains were used in this study, the reference strain ATCC 750 and a clinical isolate from urine (U69). The ability of C. tropicalis to adhere to a confluent layer of human cells was determined using an adaptation of the crystal violet staining method; cell damage and cell activity inhibition induced by the adhesion of C. tropicalis were assessed by LDH and MTS reduction, respectively. Candida tropicalis aspartyl proteinase (SAPT) gene expression was determined by real-time PCR. Candida tropicalis strains were able to adhere to the different human cells, although, in a strain and cell dependent manner. Concerning cellular response to C. tropicalis, the highest cell activity inhibition was obtained for Caco-2, followed by TCC-SUP and HeLa cells. The highest percentage of cell damage (around 14%) was observed for TCC-SUP in contact with the U69 isolate and for Caco-2 in contact with the reference strain. Real time PCR analysis revealed a wide range of expression profiles of SAP genes for both C. tropicalis strains in contact with the different types of epithelial cells. SAPT3 was the gene expressed at the highest level for both C. tropicalis strains in contact with the three human epithelial cell lines. It is important to highlight that human cells response to C. tropicalis adhesion, as well as SAPs production, is strain and epithelial cell line dependent.