Improvements in current practices of viral marker screening and donor self-exclusion are continuously increasing the safety of the blood supply. However, despite these practices, a risk of transmission of pathogens with the transfusion of cellular components of blood remains since current screening tests do not screen for rarely occurring or as yet unknown transfusion transmissible pathogens (Dodd, R. Y. New Engl. J. Med. 327:419-421 (1992); Soland, E. M., et al. J. Am. Med. Assoc. 274:1368-1373 (1995); Schreiber, G. B., et al. New Engl. J. Med. 334:1685-1690 (1996)).
To combat the deficiencies associated with screening practices, the use of sterilization procedures of blood, red blood cell concentrates (RBCC), and other blood-derived components hold promise for eliminating pathogen transmission. In this connection, various approaches have been used to sterilize blood cells, the most efficacious so far use photochemical methods (Ben-Hur, E. and B. Horowitz Photochem. Photobiol. 62:383-388 (1995); Ben-Hur, E. and B. Horowitz AIDS 10:1183-1190 (1996)). The most promising photochemical methods employ the use of phthalocyanines (which are activated by light in the far red (660-700 nm)) for sterilization of RBCC (Horowitz, B., et al. Transfusion 31:102-108 (1991); Ben-Hur, E., et al. J. Photochem. Photobiol. B:Biol. 13:145-152 (1992)).
Of the phthalocyanines, silicon phthalocyanine Pc4 has been proven to be most effective for inactivation of HIV in its multiple forms (Margolis-Nunno, H., et al. Transfusion 36:743-750 (1996)). However, because Pc4 and other phthalocyanines target the lipid envelope of viruses and can, therefore, cause red cell damage, quenchers of reactive oxygen species have been used to prevent some of this damage (Rywkin, S., et al. Photochem. Photobiol. 56:463-469 (1992); Ben-Hur, E., et al. Transfusion 35:401-406 (1995)). The use of high irradiance (Ben-Hur, et al. Photochem. Photobiol. 61:190-195 (1995)) and Chremophor as the vehicle (Ben-Hur, et al. Photochem. Photobiol. 62:575-579 (1995)) also improved the specificity of viral sterilization by Pc4.