Novel hemagglutinating, hemolytic and cytotoxic activities of the intermediate subunit of Entamoeba histolytica lectin

Galactose and N-acetyl-D-galactosamine (Gal/GalNAc) inhibitable lectin of Entamoeba histolytica, a common protozoan parasite, has roles in pathogenicity and induction of protective immunity in mouse models of amoebiasis. The lectin consists of heavy (Hgl), light (Lgl), and intermediate (Igl) subunits. Hgl has lectin activity and Lgl does not, but little is known about the activity of Igl. In this study, we assessed various regions of Igl for hemagglutinating activity using recombinant proteins expressed in Escherichia coli. We identified a weak hemagglutinating activity of the protein. Furthermore, we found novel hemolytic and cytotoxic activities of the lectin, which resided in the carboxy-terminal region of the protein. Antibodies against Igl inhibited the hemolytic activity of Entamoeba histolytica trophozoites. This is the first report showing hemagglutinating, hemolytic and cytotoxic activities of an amoebic molecule, Igl.