Characteristic structural features of schistosome cercarial N-glycans: expression of Lewis X and core xylosylation

Schistosomal egg N-glycans are the only examples in nature that have been s tructurally shown to contain beta2-xglosylation, alpha6-fucosylation, and a lpha3-fucosylation on the N,N'-diacetyl chitobiose core. We present evidenc e that core difucosylated and xylosglated N-glycans are characteristics of Schistosoma japonicum eggs but not of the cercariae and adults, for which n either core xylosylation nor alpha3-fucosylation could be readily detected. In contrast, a majority of the N-glycans from Schistosoma mansoni cercaria e but not the adults are core xylosglated, Tandem mass spectrometry analysi s coupled with chromatographic mapping, sequential exoglycosidase digestion , and methylation analysis were employed to unambiguously define the struct ures of core beta2-xylosylated, alpha6-fucosylated N-glycans from S. manson i cercariae, Unexpectedly, a majority of these N-glycans were found to carr y Lewis X determinant, Gal beta1-->4(Fuct alpha1-->3)GlcNAc beta1-->, on th e nonreducing termini of mono- and biantennary structures. The Lewis X-cont aining glycoproteins were found to be distinct from those carrying the comp lex, multifucosylated glycocalyx O-glycans reported previously. The corresp onding N-glycans from S. japonicum cercariae are likewise dominated by Lewi s X termini but without the core xylosylation, We concluded that the invadi ng cercariae present an important and abundant source of Lewis X antigens, which may contribute to the induced humoral response upon infection. Follow ing transformation and development into the adults, the N-glycans synthesiz ed comprise a significantly larger amount of high mannose and fucosylated p auci-mannose structures in comparison with the cercarial N-glycans. A porti on of the mono- and biantennary complex types were identified to carry Lewi s X and fucosylated LacdiNAc termini, which could also be detected by mass spectrometry analysis on larger, complex-type structures.