Synthesis of the carbohydrate moiety from the parasite Echinococcus multilocularis and their antigenicity against human sera.

摘要

Stereocontrolled syntheses of biotin-labeled oligosaccharide portions with a Galbeta1-3GalNAc core of the Em2 glycoprotein antigen obtained from the parasite Echinococcus multilocularis have been accomplished. Trisaccharide Galbeta1-3(GlcNAcbeta1-6)GalNAcalpha1-R (G), tetrasaccharide Galbeta1-3(Galbeta1-4GlcNAcbeta1-6)GalNAcalpha1-R (J) and pentasaccharide Galbeta1-3(Galalpha1-4Galbeta1-4GlcNAcbeta1-6)GalNAcalpha1-R (K) (R=biotinylated probe) were synthesized by block synthesis by the use of 5-(methoxycarbonyl)pentyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl-(1-->3)-2-azido-4-O-benzyl-2-deoxy -alpha-d-galactopyranoside as a common glycosyl acceptor. Moreover, linear trisaccharide Galalpha1-4Galbeta1-3GalNAcalpha1-R (H) and branched tetrasaccharide Galalpha1-4Galbeta1-3(GlcNAcbeta1-6)GalNAcalpha1-R (I) were synthesized by stepwise condensation. We examined the antigenicity of these five oligosaccharides by an enzyme linked immunosorbent assay (ELISA). Our results demonstrate that biotinylated oligosaccharides H, I and K show good serodiagnostic potential to detect infections caused by the parasite E. multilocularis. Among them the linear sequence Galalpha1-4Galbeta1-3GalNAcalpha1-R in oligosaccharide (H) appears to show the highest sensitivity (95%). Moreover, our study clarified the dominant carbohydrate epitope of Em2 antigen.