Synthesis of Galα(1,3)Galβ(1,4)GlcNAcα-, Galβ(1,4)GlcNAcα- and GlcNAc-containing neoglycoproteins and their immunological evaluation in the context of Chagas disease
作者:Nathaniel S Schocker、Susana Portillo、Carlos R N Brito、Alexandre F Marques、Igor C Almeida、Katja Michael
DOI:10.1093/glycob/cwv081
日期:——
The protozoan parasite, Trypanosoma cruzi, the etiologic agent of Chagas disease (ChD), has a cell surface covered by immunogenic glycoconjugates. One of the immunodominant glycotopes, the trisaccharide Galα(1,3)Galβ(1,4)GlcNAcα, is expressed on glycosylphosphatidylinositol-anchored mucins of the infective trypomastigote stage of T. cruzi and triggers high levels of protective anti-α-Gal antibodies (Abs) in infected individuals. Here, we have efficiently synthesized the mercaptopropyl glycoside of that glycotope and conjugated it to maleimide-derivatized bovine serum albumin (BSA). Chemiluminescent-enzyme-linked immunosorbent assay revealed that Galα(1,3)Galβ(1,4)GlcNAcα-BSA is recognized by purified anti-α-Gal Abs from chronic ChD patients ∼230-fold more strongly than by anti-α-Gal Abs from sera of healthy individuals (NHS anti-α-Gal). Similarly, the pooled sera of chronic Chagas disease patients (ChHSP) recognized Galα(1,3)Galβ(1,4)GlcNAcα ∼20-fold more strongly than pooled NHS. In contrast, the underlying disaccharide Galβ(1,4)GlcNAcα and the monosaccharide GlcNAcα or GlcNAcβ conjugated to BSA are poorly or not recognized by purified anti-α-Gal Abs or sera from Chagasic patients or healthy individuals. Our results highlight the importance of the terminal Galα moiety for recognition by Ch anti-α-Gal Abs and the lack of Abs against nonself Galβ(1,4)GlcNAcα and GlcNAcα glycotopes. The substantial difference in binding of Ch vs. NHS anti-α-Gal Abs to Galα(1,3)Galβ(1,4)GlcNAcα-BSA suggests that this neoglycoprotein (NGP) might be suitable for experimental vaccination. To this end, the Galα(1,3)Galβ(1,4)GlcNAcα-BSA NGP was then used to immunize α1,3-galactosyltransferase-knockout mice, which produced antibody titers 40-fold higher as compared with pre-immunization titers. Taken together, our results indicate that the synthetic Galα(1,3)Galβ(1,4)GlcNAcα glycotope coupled to a carrier protein could be a potential diagnostic and vaccine candidate for ChD.
BSA的差异在于,Ch抗α-Gal抗体与Galα(1,3)Galβ(1,4)GlcNAcα-BSA的结合能力比NHS抗α-Gal抗体强230倍。同样,慢性恰加斯病患者(ChHSP)的混合血清与Galα(1,3)Galβ(1,4)GlcNAcα的结合能力比NHS混合血清强20倍。相比之下,与BSA结合的潜在二糖Galβ(1,4)GlcNAcα和单糖GlcNAcα或GlcNAcβ很少或根本不被纯化的抗α-Gal抗体或恰加斯病患者或健康个体的血清识别。我们的研究结果强调了末端Galα部分对于恰加斯病抗α-Gal抗体识别的重要性,以及缺乏针对非自身Galβ(1,4)GlcNAcα和GlcNAcα糖基化合物的抗体。