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

Stereocontrolled syntheses of biotin-labeled oligosaccharide portions with a Galβ1-3GalNAc core of the Em2 glycoprotein antigen obtained from the parasite Echinococcus multilocularis have been accomplished. Trisaccharide Galβ1-3(GlcNAcβ1-6)GalNAcα1-R (G), tetrasaccharide Galβ1-3(Galβ1-4GlcNAcβ1-6)GalNAcα1-R (J) and pentasaccharide Galβ1-3(Galα1-4Galβ1-4GlcNAcβ1-6)GalNAcα1-R (K) (R = biotinylated probe) were synthesized by block synthesis by the use of 5-(methoxycarbonyl)pentyl 2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl-(1→3)-2-azido-4-O-benzyl-2-deoxy-α-d-galactopyranoside as a common glycosyl acceptor. Moreover, linear trisaccharide Galα1-4Galβ1-3GalNAcα1-R (H) and branched tetrasaccharide Galα1-4Galβ1-3(GlcNAcβ1-6)GalNAcα1-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 Galα1-4Galβ1-3GalNAcα1-R in oligosaccharide (H) appears to show the highest sensitivity (95%). Moreover, our study clarified the dominant carbohydrate epitope of Em2 antigen.

Graphical abstractFive oligosaccharides of the glycoprotein obtained from Echinococcus multilocularis were synthesized and evaluated for anitgenicity against human sera. Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Biotinylated oligosaccharides derived from E. multilocularis have been synthesized. ► The antigenicity of these oligosaccharides was examined by an ELISA. ► Some of them were showed good serodiagnostic potential to detect the infection. ► Among them, the linear trisaccharide was showed the highest sensitivity. ► Our study clarified the dominant carbohydrate epitope of Em2 antigen.