PHOTOSENSITIZED INACTIVATION OF PLASMODIUM-FALCIPARUM-INFECTED AND BABESIA-DIVERGENS-INFECTED ERYTHROCYTES IN WHOLE-BLOOD BY LIPOPHILIC PHEOPHORBIDE DERIVATIVES

Background and objectives: Blood transfusions can transmit parasitic i nfections, such as those caused by Plasmodium (malaria), Trypanosoma c ruzi (Chagas' disease), and Babesia (babesiosis), A higher degree of b lood transfusion safety would be reached if methods were available for inactivating such parasites. Materials and methods: We evaluated the effectiveness of photosensitization using lipophilic pheophorbide and red light illumination to eradicate red blood cells infected with Plas modium falciparum, and with Babesia divergens, in whole blood. Fluores cence microscopy and conventional fluorometry showed the specific accu mulation of pheophorbide derivatives in the RBC infected with either p arasite, compared with uninfected RBC. The effectiveness of different derivatives in eradicating infected RBC was first estimated in parasit e cultures. Results: The best photosensitizer was the N-(4-butanol) ph rophorbide derivative (Ph4-OH) at 0.2 mu M concentration and 5-min ill umination. In whole blood, the eradication of RBC infected with B. div ergens and P. falciparum was obtained with 2 mu M Ph4-OH and 10 and 20 min illumination, respectively. Under these conditions of photosensit ization, low levels of RBC hemolysis were noted even after 2 weeks of storage at 4 degrees C and a subsequent 48-hour incubation at 37 degre es C. No reduction of negative charges on treated RBC was noted and no increase in methemoglobin content. Conclusion: In plasma, Ph4-OH is m ainly transported by high-density lipoproteins (HDL). This high affini ty for HDL may explain the selective accumulation of lipophilic pheoph orbide derivatives in the intracellular parasites. Photosensitization with pheophorbide derivatives may be a promising approach to inactivat ion of transfusion-transmissible parasites and viruses in blood bank u nits.