VIRUS INACTIVATION IN RED-CELL CONCENTRATES BY PHOTOSENSITIZATION WITH PHTHALOCYANINES - PROTECTION OF RED-CELLS BUT NOT VESICULAR STOMATITIS-VIRUS WITH A WATER-SOLUBLE ANALOG OF VITAMIN-E

Background: Photodynamic treatment of red cells (RBCs) with phthalocya nines and red light inactivates lipid-enveloped viruses, such as vesic ular stomatitis virus (VSV) and human immunodeficiency virus, To prote ct RBCs from photodynamic damage, type I free radical quenchers, such as mannitol, which did not affect virus inactivation, were added. Stud y Design and Methods: Aluminum phthalocyanine tetrasulfonate (AlPcS(4) ) was found to inactivate VSV at a rate one-fourth that of the silicon phthalocyanines (Pc 4 and Pc 5). However, the latter also caused more RBC damage. To protect RBCs against this photodynamic damage, Trolox, a water-soluble vitamin E analogue, was used. RBC damage was measured as potassium leakage or hemolysis during storage after treatment. In addition, reduction in negative surface charge on RBCs was measured im mediately after treatment, and the effect of Trolox on VSV inactivatio n in RBCs was evaluated. Results: Trolox at a concentration of 5 mM wa s found to reduce potassium leakage during storage after Pc 4 and AlPc S(4) photodynamic treatment of RBCs, Hemolysis during Storage of RBC c oncentrates treated with Pc 4 or Pc 5 was drastically reduced by the a ddition of 5 mM Trolox prior to light exposure. At the same concentrat ion, Trolox inhibited the reduction of negative surface charges on RBC s following Pc 4 and Pc 5 photodynamic treatment. Under these conditio ns, VSV inactivation by photodynamic treatment with all phthalocyanine s was not affected by Trolox. In aqueous solution, Trolox formed a com plex with AlPcS(4), thus quenching the excited triplet state of AlPcS( 4) at a constant rate of 8.8 x 10(6) per M per second. Conclusion: The se findings indicate that Trolox protects RBCs from phthalocyanine-pho tosensitized damage without affecting virus kill. The addition of Trol ox would be beneficial for improving the quality of RBCs subjected to photodynamic treatment.