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Differences in sialic acid density in pathogenic and non-pathogenic Aspergillus species
Julie A Wasylnka1, Megan I Simmer1, Margo M Moore1
1Department of Molecular Biology and Biochemistry1 and Department of Biological Sciences2, Simon Fraser University, Burnaby, B.C., Canada V5A 1S6.
Microbiology (Reading, England)
|April 3, 2001
Summary
This study identifies sialic acids on Aspergillus fumigatus conidia, crucial for fungal adhesion to host cells. Sialic acid density varies with nutrient availability and is higher in pathogenic strains, suggesting a role in invasive lung disease.
Area of Science:
- Medical Mycology
- Fungal Pathogenesis
- Carbohydrate Chemistry
Background:
- Aspergillus fumigatus causes invasive lung disease in immunocompromised individuals.
- Conidial surface adhesins are critical for initial host cell attachment and infection establishment.
- Negatively charged carbohydrates on the conidial surface mediate adhesion to extracellular matrix proteins.
Purpose of the Study:
- To identify specific carbohydrates contributing to the negative charge of the A. fumigatus conidial surface.
- To investigate the role of these carbohydrates in fungal adhesion to host cells and extracellular matrix.
- To correlate sialic acid expression with pathogenicity in Aspergillus species.
Main Methods:
- Direct chemical analysis and indirect binding assays using sialic acid-specific lectins (Limax flavus agglutinin, Maackia amurensis agglutinin, Sambucus nigra agglutinin).
- Pre-treatment with sialidase to assess the role of sialic acids in binding and adhesion.
- High-performance thin-layer chromatography (HPTLC) for carbohydrate identification.
- Colorimetric assays for quantifying sialic acid density.
- Flow cytometry to compare sialic acid expression between pathogenic and non-pathogenic Aspergillus species.
- Inhibition assays using sialylated glycoproteins to study fibronectin adhesion.
Main Results:
- Sialic acids were identified on the surface of A. fumigatus conidia.
- Sialidase pre-treatment reduced lectin binding and adhesion to poly L-lysine.
- 2,3-alpha- and 2,6-alpha-linked sialic acids were not the predominant forms.
- Sialic acid biosynthesis occurs de novo and is regulated by nutrient composition.
- A. fumigatus exhibited significantly higher sialic acid density compared to non-pathogenic Aspergillus species.
- Sialic acids may mediate adhesion to fibronectin, a basal lamina component.
Conclusions:
- Sialic acids are key negatively charged components on the A. fumigatus conidial surface.
- The presence and density of sialic acids are linked to the pathogenic potential of A. fumigatus.
- Sialic acids likely play a role in the adhesion of A. fumigatus to host tissues, potentially via fibronectin interaction.