Sialic acids as potential virulence factors of the fungal pathogen, Aspergillus Fumigatus

Aspergillus fumigatus is an opportunistic fungal pathogen that causes invasive disease in immunosuppressed individuals. Sialic acids have been identified on A. fumigatus, but neither their structure nor biological significance had been studied in detail. Sialic acids are a family of 9-carbon monosaccharides, which are important in microbial pathogenesis. The objectives of this study were: 1) to identify the linkage, sub-terminal monosaccharide and structure of A. fumigatus sialic acids, 2) to determine the role of sialic acids in adhesion to the extracellular matrix protein, fibronectin, and 3) to determine the role of conidiospore sialic acids in phagocytosis by cultured cells. Unsubstituted sialic acid linked ?2,6 to galactose was identified on the surface of A. fumigatus conidia. Removal of conidial sialic acids decreased binding to fibronectin and uptake by cultured cells. The data indicate that sialylated glycans on A. fumigatus mediate both adhesion and uptake of this fungus by host cells.