Identification of a putative pore-forming hemolysin active at acid pH in Leishmania amazonensis.

Several organisms, including the protozoa Entamoeba histolytica and Trypanosoma cruzi, have been shown to contain pore-forming proteins (PFP) thought to play a role in the pathogenesis of the diseases they generate. In the present report, we show that promastigotes of Leishmania amazonensis express a hemolysin that appears to cause colloid-osmotic lysis, typical of pore formation. This hemolysin affects red blood cells of different species at 37 degrees C, but not at 0 degrees C, with maximum activity at pH 5.0. The hemolytic activity is heat-labile, but lysis is not affected by protease inhibitors. These results suggest the involvement of a protein with no proteolytic or detergent activity. Hemolysis is inhibited by polyethyleneglycol, suggesting its colloid-osmotic nature. Hemolytic extracts of the parasite contain a polypeptide that reacts with antibodies to perforin from mouse cytotoxic T lymphocytes or to C9 from human complement. In addition, genomic DNA of L. amazonensis contains a fragment that hybridizes to a perforin cDNA probe. The circumstantial evidence suggests that the L. amazonensis hemolytic activity may be mediated by a PFP homologous to perforin and C9.