A homologue of the cysteine proteinase gene (ACP1 or Eh-CPp3) of pathogenic Entamoeba histolytica is present in non-pathogenic E. dispar strains

One of the three cysteine proteinase genes, ACP1 (or CP 3), has been reported to be missing in non-pathogenic strains of Entamoeba histolytica (or Entamoeba dispar as recently labeled). Unexpectedly, a gene fragment very similar in its sequence (95% homology) to ACP1 of pathogenic strains was obtained by use of the polymerase chain reaction from genomic DNA and cDNA of various cloned non-pathogenic strains as well as in 23 clinical isolates from asymptomatic carriers. The finding of the ACP1 homologue in non-pathogenic or E. dispar strains rules out the proposed use of its absence for diagnostic purposes.