Expression of Le(x) antigen in Schistosoma japonicum and S.haematobium and immune responses to Le(x) in infected animals: Lack of Le(x) expression in other trematodes and nematodes

Adults of the human parasitic trematode Schistosoma mansoni, which causes hepatosplenic/intestinal complications in humans, synthesize glycoconjugates containing the Lewis x (Le(x)) Galβ1→4(Fucα1→3)GlcNAcβ1→R, but not sialyl Lewis x (sLe(x)), antigen. We now report on our analyses of Le(x) and sLe(x) expression in S.haematobium and S.japonicum, which are two other major species of human schistosomes that cause disease, and the possible autoimmunity to these antigens in infected individuals. Antigen expression was evaluated by both ELISA and Western blot analyses of detergent extracts of parasites using monoclonal antibodies. Several high molecular weight glycoproteins in both S.haematobium and S.japonicum contain the Le(x) antigen, but no sialyl Le(x) antigen was detected. In addition, sera from humans and rodents infected with S.haematobium and S.japonicum contain antibodies reactive with Le(x). These results led us to investigate whether Le(x) antigens are expressed in other helminths, including the parasitic trematode Fasciola hepatica, the parasitic nematode Dirofilaria immitis (dog heartworm), the ruminant nematode Haemonchus contortus, and the free-living nematode Caenorhabditis elegans. Neither Le(x) nor sialyl-Le(x) is detectable in these other helminths. Furthermore, none of the helminths, including schistosomes, express Le^a, Le^b, Le(y), or the H-type 1 antigen. However, several glycoproteins from all helminths analyzed are bound by Lotus tetragonolobus agglutinin, which binds Fucα1→3GlcNAc, and Wisteria floribunda agglutinin, which binds GalNAcβ1→4GlcNAc (lacdiNAc or LDN). Thus, schistosomes may be unique among helminths in expressing the Le(x) antigen, whereas many different helminths may express α1,3-fucosylated glycans and the LDN motif.