RECONSTITUTION OF THE TRYPANOLYTIC FACTOR FROM COMPONENTS OF A SUBSPECIES OF HUMAN HIGH-DENSITY-LIPOPROTEINS

Trypanosoma brucei brucei is non-infectious to man due to the sensitiv ity of these parasites to the lytic activity of normal human serum. Ap olipoproteins (ape) have been purified, under non-denaturing condition s, from the subclass of human high-density lipoprotein (HDL), termed t rypanosome lytic factor (TLF), which is responsible for the cytotoxici ty of human serum to T. b. brucei. The TLF apolipoproteins were purifi ed by anion exchange chromatography in the presence of the nonionic de tergent octylglucoside and a reconstitution method was developed which allowed the role of the individual apolipoproteins and different lipi ds to be assessed. The results suggest that the TLF lipids do not have a direct role in lysis but are necessary for the correct assembly of the lytic HDL particle. Apo A-I, apo GIII and apo L-I contribute to ly sis in reconstituted particles but individually they are not cytotoxic . Apo A-II was not required in the reconstituted TLF particle for tryp anosome lysis. Formation of a lytic HDL particle required apo L-III su ggesting its potential role as a toxin. Thermal inactivation of TLF ac tivity correlated with the amount of denatured apo L-I, indicating tha t apo L-I was involved in lysis of T. b. brucei by native TLF.