CONICET | Buscador de Institutos y Recursos Humanos

Candida albicans (Ca) is a major fungal pathogen causing systemic infections in immunosuppressed patients. High mortality rates induced by candidiasis are usually associated with the development of biofilms. The cell wall of Ca is composed of an outer layer containing mannoproteins, which are essential for the adhesion to host cells and biofilm formation. In addition, non-specific unions attributed to hydrophobic forces, have been implicated in the adhesion to biotic and abiotic surfaces. We have previously isolated a sunflower mannose-binding lectin called Helja that exerts antifungal effect, antibiofilm activity and reduction of the adherence of Ca to primary host cells from buccal epithelium. The aim of this work was to investigate the interaction of the lectin with yeast cell surface. Therefore, to assess whether Helja (0.1 μg/μl) induces changes in the cell surface hydrophobicity (CSH), the method of microbial adhesion to hydrocarbons was used. Interestingly, the CSH of the yeast cells was drastically reduced from 40 % in the controls to 4 % in Helja treated cells. To explore the direct interaction of the lectin with C. albicans cells, Helja was conjugated to fluorescein isothiocyanate (FITC) and monitored by confocal laser scanning microscopy. The cells were completely labeled with the green fluorescence of Helja-FITC, revealing the binding of the protein to the fungal cell surface. Simultaneous staining with the cell wall marker Calcofluor White showed the Helja-FITC fluorescence as a thin and outer layer relative to the CFW signal, which was abolished after mannose addition. These results point out that the mode of action of Helja would be based on the binding to the mannoproteins of the Ca cell wall, which could limit the exposure of both, the mannoproteins and the hydrophobic residues necessary for cell-cell adhesion and consequent establishment of biofilm.