In vitro lysis of the bloodstream forms of Trypanosoma brucei gambiense by stearylamine-bearing liposomes.

Cytolytic activity of liposomes consisting of stearylamine and phosphatidylcholine (SA/PC-liposomes) was examined in vitro against the bloodstream forms of Trypanosoma brucei gambiense. More than 99% of the cells (2 X 10(6)/ml) were killed within 30 min by treatment with 15 mol% SA/PC-liposomes (100 microM total lipids). As few as 1.2 X 10(12) liposomes per ml (equivalent to 2 nM liposome) showed trypanocidal activity. Fluorescence microscopy of cells treated with the dansylated SA/PC-liposomes suggested that the liposomes bound to and accumulated on the cell surface, eventually damaging the plasma membrane. SA/PC-liposomes showed no significant hemolysis when incubated with human and mouse erythrocytes under conditions that killed greater than 99.9% of the T. b. gambiense trypomastigotes. Human leukocytes were also shown to be less susceptible to SA/PC-liposomes than T. b. gambiense. These results may point to a new direction in strategy for therapy of African trypanosomiasis.