Binding of fibrinogen to the pathogenic Aspergillus species.

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.