Antisense inhibition of expression of cysteine proteinases does not affect Entamoeba histolytica cytopathic or haemolytic activity but inhibits phagocytosis.

Inhibition of most of the expression of the cysteine proteinases of Entamoeba histolytica strain HM-1:IMSS was successfully performed by transcription of ehcp5 antisense RNA using the promoter of ehg34, which encodes a L21 ribosomal protein of E. histolytica. We have generated a stable transfectant in which the overall level of cysteine proteinase activity is strongly reduced ( 90%). This transfectant has a normal growth rate in Diamond's TYI-S-33 medium, a cytopathic and haemolytic activity similar to the control HM-1:IMSS pEhAct-Neo transfectant but with a significantly lower phagocytic activity.