Recent progress in the molecular biology of Entamoeba histolytica.

Entamoeba histolytica, a protozoan parasite causing human amoebiasis, has recently been found to comprise two genetically distinct forms, potentially pathogenic and constitutively nonpathogenic ones. Host tissue destruction by pathogenic forms is believed to result from cell functions mediated by a lectin-type adherence receptor, a pore-forming peptide involved in host cell lysis, and abundant expression of cysteine proteinases. Comparisons of these products from pathogenic and nonpathogenic E. histolytica suggest that they have evolved to serve functions in free-living or commensal behaviour. Isolation of the corresponding genes have provided the tools for detailed structural studies and manipulations of amoeba cell functions.