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 phthalocyanines and red light inactivates lipid-enveloped viruses, such as vesicular stomatitis virus (VSV) and human immunodeficiency virus, To protect RBCs from photodynamic damage, type I free radical quenchers, such as mannitol, which did not affect virus inactivation, were added. Study 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 immediately after treatment, and the effect of Trolox on VSV inactivation in RBCs was evaluated. Results: Trolox at a concentration of 5 mM was found to reduce potassium leakage during storage after Pc 4 and AlPcS(4) photodynamic treatment of RBCs, Hemolysis during Storage of RBC concentrates treated with Pc 4 or Pc 5 was drastically reduced by the addition of 5 mM Trolox prior to light exposure. At the same concentration, Trolox inhibited the reduction of negative surface charges on RBCs following Pc 4 and Pc 5 photodynamic treatment. Under these conditions, VSV inactivation by photodynamic treatment with all phthalocyanines was not affected by Trolox. In aqueous solution, Trolox formed a complex 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: These findings indicate that Trolox protects RBCs from phthalocyanine-photosensitized damage without affecting virus kill. The addition of Trolox would be beneficial for improving the quality of RBCs subjected to photodynamic treatment.