Expression of Lex antigen in Schistosoma japonicum and S.haematobium and immune responses to Lex in infected animals: Lack of Lex 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 (Lex) Galβ1→4(Fucα1→3)GlcNAcβ1→R, but not sialyl Lewis x (sLex), antigen. We now report on our analyses of Lex and sLex 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 Lex antigen, but no sialyl Lex antigen was detected. In addition, sera from humans and rodents infected with S.haematobium and S.japonicum contain antibodies reactive with Lex. These results led us to investigate whether Lex 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 Lex nor sialyl-Lex is detectable in these other helminths. Furthermore, none of the helminths, including schistosomes, express Lea, Leb, Ley, 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 Lex antigen, whereas many different helminths may express α1,3-fucosylated glycans and the LDN motif.