Structural characterization of the N-glycans of Dictyocaulus viviparus: Discovery of the Lewis(x) structure in a nematode

Abstract

This paper reports the first rigorous evidence for the existence of N-linked oligosaccharides in Dictyocaulus viviparus, an economically important nematode that parasitises cattle. Structural strategies based upon fast atom bombardment mass spectrometry were employed to examine detergent extracts of homogenised adult D. viviparus for their N-glycan content. These revealed that detergent-soluble material is rich in high mannose, truncated and complex-type families of N-linked oligosaccharides. Importantly, the most abundant antennae in the complex-type structures were shown to carry the Lewis(x) epitope (Galβ1-4(Fucα1-3)GlcNAc). Although the Lewis(x) moiety occurs in other helminths such as schistosomes, nematodes have previously been thought to lack this epitope. The Lewis(x) epitopes in D. viviparus are carried on bi-, tri-, and tetraantennary glycans and are therefore candidates for recognition events requiring multivalent ligands. There is compelling evidence from schistosome research that glycoconjugates containing Lewisx structures are immunomodulators. We propose that the Lewis(x)-rich glycans identified in this study might similarly be involved in D. viviparus host interactions.