Gomesin, a peptide produced by the spider Acanthoscurria gomesiana, is a potent anticryptococcal agent that acts in synergism with fluconazole.

Gomesin is an 18-residue cysteine-rich antimicrobial peptide produced by hemocytes of the spider Acanthoscurria gomesiana. In the present study, the antifungal properties of gomesin against Cryptococcus neoformans, the etiologic agent of cryptococcosis, were evaluated. Gomesin bound to the cell surface of cryptococci, which resulted in cell death associated with membrane permeabilization. Antifungal concentrations of gomesin were not toxic for human brain cells. Supplementation of cryptococcal cultures with the peptide (1 microM) caused a decrease in capsule expression and rendered fungal cells more susceptible to killing by human brain phagocytes. The possible use of gomesin in combination with fluconazole, a standard antifungal drug, was also evaluated. In association with fluconazole, gomesin concentrations with low antimicrobial activity (0.1-1 microM) inhibited fungal growth and enhanced the antimicrobial activity of brain phagocytes. These results reveal the potential of gomesin to promote inhibition of cryptococcal growth directly or by enhancing the effectiveness of host defenses.

An ectophosphatase activity in Candida parapsilosis influences the interaction of fungi with epithelial cells.

This study describes the biochemical characterization of a phosphatase activity present on the cell surface of Candida parapsilosis, a common cause of candidemia. Intact yeasts hydrolyzed p-nitrophenylphosphate to p-nitrophenol at a rate of 24.30+/-2.63 nmol p-nitrophenol h(-1) 10(-7) cells. The cell wall distribution of the Ca. parapsilosis enzyme was demonstrated by transmission electron microscopy. The duration of incubation of the yeast cells with the substrate and cell density influenced enzyme activity linearly. Values of V(max) and apparent K(m) for p-nitrophenylphosphate hydrolysis were 26.80+/-1.13 nmol p-nitrophenol h(-1) 10(-7) cells and 0.47+/-0.05 mM p-nitrophenylphosphate, respectively. The ectophosphatase activity was strongly inhibited at high pH as well as by classical inhibitors of acid phosphatases, such as sodium orthovanadate, sodium molybdate, sodium fluoride, and inorganic phosphate, the final product of the reaction. Only the inhibition caused by sodium orthovanadate was irreversible. Different phophorylated amino acids were used as substrates for the Ca. parapsilosis ectoenzyme, and the highest rate of phosphate hydrolysis was achieved using phosphotyrosine. A direct relationship between ectophosphatase activity and adhesion to host cells was established. In these assays, irreversible inhibition of enzyme activity resulted in decreased levels of yeast adhesion to epithelial cells.

Binding of glucuronoxylomannan to the CD14 receptor in human A549 alveolar cells induces interleukin-8 production.

Glucuronoxylomannan (GXM) is the major capsular polysaccharide of Cryptococcus neoformans. GXM receptors have been characterized in phagocytes and endothelial cells, but epithelial molecules recognizing the polysaccharide remain unknown. In the current study, we demonstrate that GXM binds to the CD14 receptor in human type II alveolar epithelial cells, resulting in the production of the proinflammatory chemokine interleukin-8.

Glucuronoxylomannan-mediated interaction of Cryptococcus neoformans with human alveolar cells results in fungal internalization and host cell damage.

Infection by Cryptococcus neoformans begins with inhalation of infectious propagules. Fungi reach the lung tissue and interact with epithelial cells in a crucial but poorly understood process. In this study, the interaction of C. neoformans with the human alveolar epithelial cell lineage A549 was investigated, focusing on the relevance of the capsular polysaccharide in this process. The association of encapsulated strains with A549 cells was significantly inhibited by a monoclonal antibody to glucuronoxylomannan (GXM), a major component of the cryptococcal capsule. A purified preparation of GXM produced similar results, suggesting the occurrence of surface receptors for this polysaccharide on the surface of alveolar cells. A549 cells were in fact able to bind soluble GXM, as confirmed by indirect immunofluorescence analysis using the anti-polysaccharide antibody. C. neoformans is internalized after GXM-mediated interaction with A549 cells in a process that culminates with death of host cells. Our results suggest that C. neoformans can use GXM for attachment to alveolar epithelia, allowing the fungus to reach the intracellular environment and damage host cells through still uncharacterized mechanisms.