Snail host finding by Fasciola hepatica and Trichobilharzia ocellata: Compound analysis of "miracidia-attracting glycoproteins"

The glycoconjugates from snail-conditioned water of Lymnaea truncatula and L. stagnalis which elicit typical host finding behavior in miracidia of Fas ciola hepatica and Trichobilharzia ocellata were separated by anion-exchang e chromatography and a two-step size-exclusion chromatography. We obtained fractions attractive for the parasites with MW of about 10(6) Da in both sn ail species. These fractions still contained species-specific information s ince miracidia responded only to molecules from their respective host snail . Analysis of the amino acid composition from the protein backbone revealed a similar composition in the effective fractions of both snails. Amounts o f serine and threonine were higher than 30 mol %, which is typical for muci n-type glycoproteins. The carbohydrate moieties consisted mainly of galacto se and fucose, but nine different other monosaccharides also were identifie d in smaller amounts. The heterogeneity of the molecules was also confirmed by the binding of six different lectins. Because of these characteristics, the effective molecules were termed "miracidia-attracting glycoproteins" ( MAGs). MAGs may play an important role for parasite transmission, as they m ay increase the chance of an encounter between parasite and host and enable the miracidia to discriminate between their specific intermediate host and other unsuitable snail species. (C) 2000 Academic Press.