O-glycosylation in Echinococcus granulosus: Identification and characterization of the carcinoma-associated Tn antigen

In the present work we demonstrate that the cancer-associated O-glycosylate d Tn antigen (GalNAc-O-Ser/Thr) is expressed by the cestode Echinococcus gr anulosus. This antigen was detected in both larval and adult worm extracts, with the highest specific activity observed in the adult excretion/secreti on preparation. Histochemical analysis showed that Tri is preferentially ex pressed in the parenchyma in both parasite stages and the external part of tegument in adult worms. A similar pattern was observed for sialyl-Tn, a re lated O-linked antigen. Tn glycoproteins from protoscoleces were resolved b y SDS-PAGE in two main components of 43 and 49 kDa. After purification, thi s material was reactive with lectins which bind GlcNAc/sialic acid, GalNAc, and T antigen. In a preliminary evaluation, high levels of Tn antigen were detected in serum samples from patients with hydatid cyst, suggesting that the measure of Tri in serum could be a biomarker of this disease, although extensive work is necessary in order to determine the clinical usefulness of this assay. The results reported here, the first evidence of O-glycosyla tion pathways in E. granulosus and the presence of Tn antigen in cestodes. suggest that the evaluation of O-glycosylated antigens might give new insig hts in the host-parasite relationship. (C) 2001 Academic Press.