Synthesis, antigenicity against human sera and structure-activity relationships of carbohydrate moieties from Toxocara larvae and their analogues.

Stereocontrolled syntheses of biotin-labeled oligosaccharide portions containing the Gal beta 1-3GalNAc core of the TES-glycoprotein antigen obtained from larvae of the parasite Toxocara and their analogues have been accomplished. Trisaccharides Fuc2Me alpha 1-2Gal4Me beta 1-3GalNAc alpha 1-OR (A), Fuc alpha 1-2Gal4Me beta 1-3GalNAc alpha 1-OR (B), Fuc2Me alpha 1-2Gal beta 1-3GalNAc alpha 1-OR (C), Fuc alpha 1-2Gal beta 1-3GalNAc alpha 1-OR (D) and a disaccharide Fuc2Me alpha 1-2Gal4Me beta 1-OR (E) (R = biotinylated probe) were synthesized by block synthesis using 5-(methoxycarbonyl) pentyl-2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl-(1 -> 3)-2-azide-4-O-benzyl-2-deoxy-alpha-D-galactopyranoside as a common glycosyl acceptor. We examined the antigenicity of these five oligosaccharides by enzyme linked immunosorbent assay (ELISA). Our results demonstrate that the O-methyl groups in these oligosaccharides are important for their antigenicity and the biotinylated oligosaccharides A, B, C and E have high serodiagnostic potential to detect infections caused by Toxocara larvae.