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Binding of fibrinogen to the pathogenic Aspergillus species
J P Bouchara1, A Bouali, G Tronchin
1Laboratoire de Parasitologie--Mycologie, Centre Hospitalier Régional, Angers, France.
Abstract:
The binding of human fibrinogen to the pathogenic aspergilli was investigated in vitro by different procedures using either fibrinogen in solution or fixed, insolubilized fibrinogen. Binding of fibrinogen was detected at the surface of hyphae and conidia by an immunofluorescence assay. Ultrastructural localization of the binding sites was visualized with fibrinogen-sensitized gold particles. The labelling was restricted to the outer cell wall layer of the 'smooth' walled conidia. Quantitative analysis of the binding carried out with 125I-labelled human fibrinogen on 33 species belonging to different groups (opportunistic fungi, strictly saprophytic or phytopathogenic fungi and dermatophytes or related species) clearly demonstrated that among all the fungi tested, only the pathogenic aspergilli significantly bound fibrinogen. The average amount of fibrinogen bound to individual conidia was also quantified. Binding was greater to Aspergillus niger (5-fold), Aspergillus fumigatus (2.5-fold) and Aspergillus flavus conidia (2.3-fold) than to Aspergillus terreus conidia. The results suggest that fibrinogen binding could contribute to the pathogenesis of aspergillosis.
Insights
Pathogenic aspergilli, but not other fungi, significantly bind human fibrinogen. This fibrinogen binding to fungal surfaces may play a role in the development of aspergillosis infections.
Area of Science:
- Medical Mycology
- Infectious Diseases
- Biochemistry
Background:
- Pathogenic fungi, particularly Aspergillus species, cause significant human infections (aspergillosis).
- Fibrinogen, a key protein in blood clotting, is increasingly recognized for its role in host-pathogen interactions.
- Understanding fungal surface interactions with host proteins is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the in vitro binding of human fibrinogen to pathogenic Aspergillus species.
- To determine if fibrinogen binding is specific to pathogenic aspergilli compared to other fungal groups.
- To explore the potential contribution of fibrinogen binding to the pathogenesis of aspergillosis.
Main Methods:
- In vitro binding assays using soluble and insolubilized human fibrinogen.
- Immunofluorescence assays to detect fibrinogen binding on fungal surfaces (hyphae and conidia).
- Ultrastructural localization using fibrinogen-sensitized gold particles.
- Quantitative analysis of fibrinogen binding using 125I-labelled human fibrinogen across 33 fungal species.
Main Results:
- Pathogenic Aspergillus species demonstrated significant binding of human fibrinogen.
- No significant fibrinogen binding was observed in other tested fungal groups, including opportunistic, saprophytic, phytopathogenic, and dermatophyte species.
- Fibrinogen binding was localized to the outer cell wall layer of conidia.
- Quantitative analysis revealed differential binding affinities, with Aspergillus niger, Aspergillus fumigatus, and Aspergillus flavus showing higher binding than Aspergillus terreus.
Conclusions:
- Human fibrinogen specifically binds to pathogenic Aspergillus species.
- The outer cell wall of conidia represents a key site for fibrinogen interaction.
- Fibrinogen binding is a potential virulence factor contributing to the pathogenesis of aspergillosis.