Carbohydrate Chemistry and Synthesis (148)Trypanosoma species research and implications (81)Glycosylation and Glycoproteins Research (67)Lysosomal Storage Disorders Research (27)Microbial Metabolites in Food Biotechnology (22)
Balouz V, Lopez R, Conte N, Abal M, Ducrey I, et al.
PLoS neglected tropical diseases •
Chagas disease (ChD), caused by the parasitic protozoan Trypanosoma cruzi, is a lifelong, neglected tropical disease with substantial medical and socioeconomic impact. Despite this situation, currently available diagnostic and therapeutic methods display serious limitations. A promising strategy to improve ChD serodiagnosis involves targeting parasite carbohydrate antigens, particularly the α-galactosyl-rich mucins that coat the surface of bloodstream trypomastigotes (tGPI-mucins). Here, we present a concise and efficient protocol for the chemical synthesis of a tGPI-mucin-derived glycotope, the disaccharide α-D-Galp-(1 → 3)-β-D-Galp, and its functional conjugation to different scaffolds using the squarate method. A neoglycoprotein made upon a bovine serum albumin (BSA) carrier decorated with ∼38 units of the disaccharide, termed BSA-Di, was interrogated with sera of chronic ChD patients and healthy individuals from Argentina using an in-house enzyme-linked immunosorbent assay (ELISA). BSA-Di exhibited excellent sensitivity and effectively discriminated between ChD-positive and negative sera with high accuracy (AUC = 0.905), though its specificity was partially affected by cross-reactivity of some non-ChD sera containing natural α-Gal antibodies. Conjugation of α-D-Galp-(1 → 3)-β-D-Galp to T. cruzi antigenic peptides, instead of BSA, corroborated these findings and enabled the generation of bivalent ChD diagnostic reagents combining glycan- and peptide-based epitopes. Overall, our results identify α-D-Galp-(1 → 3)-β-D-Galp as a robust and reliable biomarker of T. cruzi infection. The methodologies and tools described here, together with optimized derivatives, are expected to positively impact ChD serological applications.
The α-gal epitope, which refers to the carbohydrate α-d-Gal-(1 → 3)-β-d-Gal-(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 α-1,3-galactosyltransferase gene. For that reason, humans produce antibodies against α-d-Gal containing glycoproteins and glycolipids of other species. We summarize here the glycoconjugates with α-d-Gal structures in , , and pathogenic protozoa. These were identified in infective stages of and in sporozoites. In , α-d-Gal 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 α-gal trisaccharide, also called the Galili epitope, and the glycans of GIPLs found in , the preparation of neoglycoconjugates, and the studies in which they were involved are also included in this Review.
Villar M, Pacheco I, Mateos-Hernández L, Cabezas-Cruz A, Tabor AE, et al.
Expert review of proteomics •
Ticks are obligate hematophagous arthropods that synthesize the glycan Galα1-3Galβ1-(3)4GlcNAc-R (α-Gal) associated with the alpha-gal syndrome (AGS) or allergy to mammalian meat consumption. In this study, we used a proteomics approach to characterize tick proteins in salivary glands (sialome SG), secreted saliva (sialome SA) and with α-Gal modification (alphagalactome SG and SA) in model tick species associated with the AGS in the United States () and Australia (). Selected proteins reactive to sera (IgE) from patients with AGS were identified to advance in the identification of possible proteins associated with the AGS. For comparative analysis, the α-Gal content was measured in various tick species. The results confirmed that ticks produce proteins with α-Gal modifications and secreted into saliva during feeding. Proteins identified in tick alphagalactome SA by sera from patients with severe AGS symptomatology may constitute candidate disease biomarkers. The results support the presence of tick-derived proteins with α-Gal modifications in the saliva with potential implications in AGS and other disorders and protective capacity against tick infestations and pathogen infection. Future research should focus on the characterization of the function of tick glycoproteins with α-Gal in tick biology and AGS.