Entamoeba histolytica: Cytopathogenicity and lectin activity of avirulent mutants

Abstract

Three clones of Entamoeba histolytica (L-6, C 93, C 919) were isolated by mutagenesis with ethyl methanesulfonate from the axenic strain HM1:IMSS and were studied for adherence, cytolytic, and soluble galactose inhibitable lectin activity. Avirulent clones adhered to and killed fewer Chinese hamster ovary cells than HM1:IMSS ( P < 0.01). However, only C 919 was deficient in adherence to red blood cells. Galactose (1.0 g) completely inhibited adherence of all the mutants to Chinese hamster ovary cells; however, adherence to erythrocytes was only partially inhibitable by galactose. Avirulent mutants were more susceptible to being killed by human neutrophils in vitro ( P < 0.01 compared to HM1:IMSS). Soluble protein preparations from all the avirulent mutants were markedly less mitogenic for human lymphocytes and had lower lectin activity for Chinese hamster ovary cells compared to the HM1:IMSS wild type ( P < 0.01 for each activity with each mutant). Indirect immunofluorescence with a monoclonal antibody (F-14) that recognizes the Gal GalNAc lectin was positive for L-6 and C 919. These findings utilizing avirulent mutants of E. histolytica further support a role for the amebic galactose inhibitable lectin in the in vivo pathogenesis of amebiasis.