COMPARISON OF METHYLENE-BLUE AND METHYLENE VIOLET FOR PHOTOINACTIVATION OF INTRACELLULAR AND EXTRACELLULAR VIRUS IN RED-CELL SUSPENSIONS

Previous studies with methylene blue (MB) in red cell suspensions have demonstrated that extracellular, but not intracellular, virus can be readily photoinactivated. To test if the resistance of intracellular v irus to inactivation is related to the permanent positive charge of th e phenothiazine, a series of uncharged phenothiazine dyes, methylene v iolet (MV), monodemethylated MV and didemethylated MV, were studied, V alues of the sensitivity of intracellular relative to extracellular ve sicular stomatitis virus (VSV) inactivation for the three dyes (D-10 e xtracellular/D-10 intracellular) in buffer were 1.0, 0.60 and 0.33, re spectively, In contrast, intracellular virus was resistant to inactiva tion with MB, with a D-10 extracellular/D-10 intracellular of 0.05 in buffer, Because virucidal activity of MV was inhibited by the presence of plasma, the red cells (30% hematocrit) were repeatedly washed prio r to photoinactivation and storage, Under conditions where MB and MV i nactivated approximately 5 log(10) of extracellular VSV, intracellular VSV was inactivated by more than 4 log(10) with MV compared to 0.88 l og(10) with MB, These phototreatment conditions did not significantly affect red cell morphology, extracellular pH, ATP or 2,3-diphosphoglyc erol levels during 42 days of 1-6 degrees C storage, There was enhance d potassium efflux and hemolysis over values obtained from untreated c ontrols; the extent of change from controls was comparable for each ph ototreatment. These results indicate that the uncharged phenothiazine dye, MV, can inactivate both intracellular and extracellular virus yet exhibit similar in vitro red cell storage properties as MB phototreat ment.