STRUCTURAL CHARACTERIZATION OF THE N-GLYCANS FROM ECHINOCOCCUS-GRANULOSUS HYDATID CYST MEMBRANE AND PROTOSCOLECES

Infection by the tapeworm Echinococcus granulosus in the intermediate host results in the development of a hydatid cyst which contains the p rotoscoleces within a fluid-filled cavity enclosed by the bilayered cy st membrane. N-glycans were enzymatically released from crude extracts of homogenates of hydatid cyst membranes and protoscoleces and their structures were defined by high sensitivity fast atom bombardment mass spectrometry in conjunction with sequential exoglycosidase digestions . The major N-glycans from the cyst membrane were found to be non-char ged structures having complex-type antennae and core fucosylation. The antennae are either truncated at the first N-acetylglucosamine or are extended with beta-galactose to form N-acetyllactosamine (lacNAc). A significant proportion of the lacNAc backbones are capped by alpha-gal actose. The resulting Gal alpha-Gal beta-terminal structures may accou nt for the earlier observation that antibodies against the blood group Pl epitope recognise components of hydatid cyst extracts. The complex -type N-glycans identified in the protoscoleces extracts were the same as the neutral structures found in the cyst membrane but a small prop ortion of high mannose structures and truncated di- and trimannosyl co re structures were also identified. Sialylated N-glycans were identifi ed as minor constituents of the cyst membrane preparation but were not observed in protoscoleces extracts. Whether the sialylated glycans ar e host derived or endogenously synthesized by the parasite remains to be established. This is the first reported structural analysis of N-gl ycans from cestodes and provides new insights into protein glycosylati on in helminths. (C) 1997 Elsevier Science Ireland B.V.