BINDING OF HUMAN FIBRONECTIN TO ASPERGILLUS-FUMIGATUS CONIDIA

Aspergillus fumigatus conidia exhibited the ability to bind purified h uman fibronectin, whereas mycelial forms did not bind the ligand, as d etected by an indirect immunofluorescence assay with an antifibronecti n polyclonal antibody after incubation of the cells with fibronectin. Flow cytometry confirmed that binding of the ligand to conidia was dos e dependent and saturable, Pretreatment of the cells with trypsin mark edly reduced binding, which suggested a protein nature for the binding sites present at the surface of conidia. Intact conidia were also abl e to adhere to fibronectin immobilized on microtiter plates. When adhe sion experiments were performed in the presence of soluble fibronectin or antifibronectin antibodies, a significant reduction (from 88 to 92 %) in the binding of conidia was noticed, thus suggesting that adhesio n to the immobilized ligand was specific. Analysis by sodium dodecyl s ulfate-polyacrylamide gel electrophoresis and Western immunoblotting w ith fibronectin and antifibronectin antibody of whole conidial homogen ates and 2 mercaptoethanol extracts from isolated conidial cell walls allowed identification, among the complex array of protein and glycopr otein species present in both cell-free preparations, of two polypepti des with apparent molecular masses of 23 and 30 kDa which specifically interact with fibronectin.