In vitro activity of the trypanocidal diamidine DAPI on animal-infective Trypanosoma brucei brucei

A mammalian feeder layer system for the continuous cultivation of infective bloodstream forms of Trypanosoma brucei brucei has been used for investigating the antitrypanosomal activity of the aromatic diamidine DAPI. The drug was active at concentrations which can be reached under physiological conditions. The minimum effective concentration was 0.05 micrograms/ml. Minimum exposure times required for antitrypanosomal activity were dependent on the drug concentrations. Furthermore, DAPI was found to cause toxic side effects on bovine fibroblast feeder layer cells at high drug concentrations (10 micrograms/ml), however, at low concentrations (1 microgram/ml), the drug acted selectively on trypanosomes. Both the reproducibility and the high sensitivity to drugs of the system make this assay a valuable technique for chemotherapeutic studies on trypanosomes.