Glycotope analysis in miracidia and primary sporocysts of Schistosoma mansoni: Differential expression during the miracidium-to-sporocyst transformation

Fucosylated carbohydrate epitopes (glycotopes) expressed by larval and adult schistosomes are thought to modulate the host immune response and possibly mediate parasite evasion in intermediate and definitive hosts. While previous studies showed glycotope expression is developmentally and stage-specifically regulated, relatively little is known regarding their occurrence in miracidia and primary sporocysts. In this study, previously defined monoclonal antibodies were used in confocal laser scanning microscopy, standard epifluorescence microscopy and Western blot analyses to investigate the developmental expression of the following glycotopes in miracidia and primary sporocysts of Schistosoma mansoni: GalNAc beta 1-4GlcNAc (LDN), GalNAc beta 1-4(Fuc alpha 1-3)GlcNAc (LDN-F), Fuc alpha 1-3GalNAc beta 1-4GlcNAc (F-LDN), Fuc alpha 1-3GalNAc beta 1-4(Fuc alpha 1-3)GlcNAc (F-LDN-F), GalNAc beta 1-4(Fuc alpha 1-2Fuc alpha 1-3)GlcNAc (LDN-DF), Fuc alpha 1-2Fuc alpha 1-3GalNAc beta 1-4(Fuc alpha 1-2Fuc alpha 1-3)GlcNAc (DF-LDN-DF), Gal beta 1-4(Fuc alpha 1-3)GlcNAc (Lewis X) and the truncated trimannosyl N-glycan Man alpha 1-3(Man alpha 1-6)Man beta 1-4GlcNAc beta 1-4GlcNAc beta 1-Asn (TriMan). All but Lewis X were variously expressed by miracidia and sporocysts of S. mansoni. Most notably, alpha 3-fucosylated LDN (F-LDN, F-LDN-F, LDN-F) was prominently expressed on the larval surface and amongst glycoproteins released during larval transformation and early sporocyst development, possibly implying a role for these glycotopes in snail-schistosome interactions. Interestingly, Fuc alpha 2Fuc alpha 3-subsituted LDN (LDN-DF, DF-LDN-DF) and LDN-F were heterogeneously surface-ex pressed on individuals of a given larval population, particularly amongst miracidia. In contrast, LDN and TriMan primarily localised in internal somatic tissues and exhibited only minor surface expression. Immunoblots indicate that glycotopes occur on overlapping but distinct protein sets in both larval stages, further demonstrating the underlying complexity of schistosome glycosylation. Additionally, sharing of specific larval glycotopes with Biomphalaria glabrata suggests an evolutionary convergence of carbohydrate expression between schistosomes and their snail host. (C) 2009 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.