Structural and functional analysis of glycosphingolipids of Schistosoma mansoni

Glycosphingolipids are ubiquitous membrane components that play important roles in signal transduction events thereby affecting many cellular functions, including modulation of the immune response. Whereas many studies focus on the functional roles of glycosphingolipids in mammals, relatively little is known about the structures of glycosphingolipids of pathogenic organisms, and how such pathogen-derived glycosphingolipids influence immune functions of their hosts. Many different glycosphingolipids of the human parasitic helminth Schistosoma mansoni have been structurally characterized. Recent evidence indicates that glycosphingolipids isolated from different life-cycle stages of the parasite have the potential to modulate the function of human dendritic cells, a cell population that is crucial to regulate adaptive immunity in the host. A remarkable finding in this context is that glycosphingolipids derived from adult worms induce maturation of dendritic cells, in contrast to glycosphingolipids of eggs or cercariae. The glycosphingolipid-induced dendritic cell activation requires intact fucose residues on the glycolipids, and is induced via a mechanism that involves both the dendritic cell receptors TLR4 and DC-SIGN. In this chapter, we describe methods to extract glycosphingolipids from the different life-cycle stages of the parasite, techniques to separate them by thin-layer chromatography or high-performance liquid chromatography as well as strategies to structurally characterize the glycan and ceramide moieties of the glycosphingolipids. Moreover, an overview is provided of the structural diversity in the glycosphingolipid-derived glycan moieties found in this helminth. Finally, we discuss methods used to isolate monocyte-derived dendritic cells from human blood and to study the modulation of dendritic cell function by these molecules.