To decrease the risk of virus infection by blood transfusion, we investigated a virus photoinactivation method which employs methylene blue (MB) in combination with red light irradiation on human plasma. Irradiation equipment containing light emitting diodes (LED) has been developed. The LED irradiation spectrum overlaps well the MB absorption spectrum. Vesicular stomatitis virus (VSV) 4.1 log10 was inactivated with 1uM MB at 2.4J/cm2 irradiation. Similarly, 4.1 log10 infectivity of human immunodeficiency virus type 1 (HIV-1) was reduced to below the detection limit (0.5 log10) with 1uM MB at 1.4J/cm2. Under conditions in which HIV-1 was completely killed, the activities of coagulation factor VIII and fibrinogen were maintained at more than 90% of pretreatment level. Antithrombin III activity was not affected by phototreatment. Prothrombin time and activated partial thromboplastin time were slightly prolonged. These data suggest that MB phototreatment is an effective method of inactivating viruses in plasma and, hence, of ensuring the supply of safer plasma products.
