Novel N-glycans of the parasitic nematode Trichinella spiralis

In this review we use the example of the parasitic nema- tode, Trichinella spiralis to demonstrate the significance of glycans at the host-parasite interface. The history of research on the N-glycans of T spiralis demonstrates the advantages of a multi-disciplinary approach, incorporating structural, synthetic, and immunologic methods to studies of parasitism. In common with many other nematodes, Trichinella secretes and displays on its cuticle a large number of proteins that display a rich repertoire of N-linked glycans. Many of these glycans are ubiquitous in nematodes, and, indeed, in many eukaryotes, but the most interesting are unique to Trichinella. The former group include high mannose and truncated structures, whilst the latter belong to the family of complex-type N-glycans. LacdiNAc is the preferred antenna building block in many helminths including Trichinella. The L1 stage of T spiralis modifies lacdiNAc with phosphorylcholine moieties or by substitution with D-tyvelose (3,6-dideoxy-D-arabino-hexose). Both modifications create highly immunogenic epitopes. Tyvelose is the target of protective immunity against T spiralis and has been studied in greatest depth. Chemical synthesis of the terminal tetrasaccharide, containing an alpha- or beta-linked tyvelose residue, was undertaken so that immunochemical experiments could be used to infer the stereochemistry of the terminal linkage in the naturally occurring glycan. The synthesis of these glycosides required the development of new methodology to introduce the unique capping 3,6-dideoxy-beta-D-arabino-hexopyranoside. Results of binding studies with synthetic glycans and protective antibodies have clarified the inhibitory actions of antibodies on T spiralis.