LacdiNAc- and LacNAc-containing glycans induce granulomas in an in vivo model for schistosome egg-induced hepatic granuloma formation

Schistosomes, major parasitic helminths, express numerous glycoconjugates that provoke humoral and cellular immune responses in the infected human host. The main pathology in schistosomiasis is due to the formation of granulomas around tissue-trapped eggs and the resulting organ damage. By using a mouse model of induction of granulomas by hepatic implantation of antigen-coated beads, it has been determined that the glycan part of schistosomal soluble egg antigens (SEA) initiates granulomogenesis. To identify which individual glycan elements in this complex SEA mixture are granulomogenic, we have tested in the same mouse model conjugates of various synthetic oligosaccharides characteristic for schistosome eggs, including GalNAcbeta1-4GlcNAc (LacdiNAc, LDN), Galbeta1-4(Fucalpha1-3)GlcNAc (Lewisx), Fucalpha1-2Fucalpha1-3GlcNAc (DF-Gn), and Fucalpha1-3GalNAcbeta1-4(Fucalpha1-3)GlcNAc (F-LDN-F). Ribonuclease (RNase) A and B, and different fetuin glycoforms were included as controls. Only beads that carry glycoconjugates with terminal LacdiNAc or Galbeta1-4GlcNAc (LacNAc, LN) elements gave rise to granulomas, with macrophage, lymphocyte, and eosinophil levels similar to the granulomatous lesions caused by schistosome eggs in a natural infection. Uncoated beads, and beads coated with fucosylated glycoconjugates or glycoconjugates lacking terminally exposed Gal or GalNAc, only attracted a monolayer of macrophages. These results indicate that the formation of hepatic granulomas is triggered specifically by glycoconjugates which carry terminal LacNAc or LacdiNAc, both constituents of the schistosome egg.