Jp. Bouchara et al., SIALIC ACID-DEPENDENT RECOGNITION OF LAMININ AND FIBRINOGEN BY ASPERGILLUS-FUMIGATUS CONIDIA, Infection and immunity, 65(7), 1997, pp. 2717-2724
In an attempt to define the molecular basis of the adherence of Asperg
illus fumigatus conidia to the host tissues, a step which might be med
iated by the recognition of basement membrane laminin or fibrinogen, w
e analyzed the binding of these glycoproteins by flow cytometry and a
microtiter plate adherence assay. Flow cytometry revealed that the bin
ding of fluorescein isothiocyanate-labeled laminin to conidia was satu
rable and specific. Moreover, the ability of conidia to bind laminin i
ncreased with their maturation. Competition experiments showed a cross
-reactivity between laminin and fibrinogen binding and a lack of inter
actions with glycosaminoglycans. In addition, the binding of laminin w
as not inhibited by the different adhesive synthetic peptides tested.
Furthermore, the microtiter plate assay of adherence to chymotrypsin d
egradation products of laminin or fibrinogen purified by gel filtratio
n suggested a unique binding site common to sequential degradation fra
gments or the presence of multiple binding sites on the two ligands. T
herefore, the role of carbohydrates in the recognition process was inv
estigated. Among the carbohydrates tested, constitutive of the conidia
l wall or of the oligosaccharide side chains of laminin and fibrinogen
, only N-acetylneuraminic acid and sialyllactose inhibited the binding
of these glycoproteins to conidia. In conclusion, these results stren
gthen the idea that the laminin and fibrinogen receptors in A. fumigat
us are identical and suggest an interaction mediated by a sialic acid-
specific lectin of the conidial wall.