A Tetrasaccharide Containing a Galactofuranosyl Determinant of Mucins from <i>Trypanosoma cruzi</i> Inhibits the Parasite Adhesion on <i>Triatoma infestans</i> Rectum

Trypanosoma cruzi, the etiologic agent of Chagas disease, is a protozoan parasite transmitted to humans via the feces of blood-sucking triatomine vectors such as Triatoma infestans. It has been shown that galactofuranose-containing oligosaccharides present in mucins of T. cruzi are involved in parasite adhesion to the T. infestans rectal ampoule, a key step in the differentiation programme from dividing epimastigote to nondividing mammal-infective metacyclic forms of the parasite. To further characterize this process, the α-benzyl glycoside of β-D-Galf(1 → 2)-β-D-Galf(1 → 4)-[β-D-Galp-(1 → 6)]-D-GlcNAc is synthesized and its alditol derivative is spectroscopically characterized. The tetrasaccharide component of this glycoside is a substructure of the O-linked pentasaccharide and hexasaccharide structures found in the T. cruzi epimastigote mucins. The tetrasaccharide glycoside inhibits parasite adhesion to the rectal ampoule of T. infestans, suggesting that some or all of the binding capacity of T. cruzi epimastigotes resides within this O-glycan tetrasaccharide substructure. Since T. cruzi mucin O-linked glycans are known to be acceptors for T. cruzi trans-sialidase, it is investigated whether the tetrasaccharide substructure acts as an acceptor substrate for this activity. The successful transfer of sialic acid to the tetrasaccharide glycoside indicates that further elaboration to the pentasaccharide and hexasaccharide structures is not essential for sialic acid transfer.