Neutral proteinase activities in different strains and clones of Entamoeba histolytica. Correlation with virulence.

ABSTRACT

Although several factors are involved in the invasive behavior of E. histolytica, proteinases seem to play a key role. Different proteinases have been found in virulent trophozoites of this parasite. Cytosols of clones A, 32-1 462-1 and L-6 of E. histolytica exhibiting various degrees of virulence were used to study the activity of trypsin-like, plasminogen activator and cathepsin B neutral proteinases with specific synthetic oligopeptides. Cathepsin-B like activity showed the highest values in highly virulent clone A, which is derived from virulent strain HM1IMSS. On the contrary, non virulent clones had very low activity. Clone L-6, a non virulent subclone of strain HM1IMSS, retained some cathepsin B-like activity. Trypsin-like and plasminogen activator assays revealed low activity and no differences between virulent and non-virulent clones were found. It is concluded that the Arg-Arg-thiol proteinase (Cathepsin B-like) is a good virulence marker.