The α-Galactosyl Carbohydrate Epitope in Pathogenic Protozoa

The alpha-gal epitope, which refers to the carbohydrate alpha-D-Galp-(1 -> 3)-beta-D-Galp-(1 -> 4)-D-GlcNAc-R, was first described in the glycoconjugates of mammals other than humans. Evolution caused a mutation that resulted in the inactivation of the alpha-1,3-galactosyltransferase gene. For that reason, humans produce antibodies against alpha-D-Galp containing glycoproteins and glycolipids of other species. We summarize here the glycoconjugates with alpha-D-Galp structures in Trypanosoma, Leishmania, and Plasmodium pathogenic protozoa. These were identified in infective stages of Trypanosoma cruzi and in Plasmodium sporozoites. In Leishmania, alpha-D-Galp is linked differently in the glycans of glycoinositolphospholipids (GIPLs). Chemically synthesized neoglycoconjugates have been proposed as diagnostic tools and as antigens for vaccines. Several syntheses reported for the alpha-gal trisaccharide, also called the Galili epitope, and the glycans of GIPLs found in Leishmania, the preparation of neoglycoconjugates, and the studies in which they were involved are also included in this Review.