With an alpha-galactosidase, B erythrocytes can be converted to blood group O under conditions that neither impair their viability in vitro nor affect their ability to survive normally after transfusion to individuals of groups O, A, and B. Such an approach has the potential for producing enzymatically converted group O cells for use in transfusion therapy. It should also be possible to convert A cells to group O by using the appropriate alpha-N-acetylgalactosaminidase.

The relative importance of type I and type II mechanisms in the photodynamic treatment of red blood cell concentrations (RBCC) to inactivate viruses was studied using aluminum phthalocyanine tetrasulfonate (AlPcS4), visible light and quenching or enhancing agents of reactive forms of oxygen. Treatment of a human RBCC with 10-13 microM AlPcS4 and 25-26 mW/cm2 visible light resulted in the rapid and complete inactivation of added vesicular stomatitis virus (VSV). The addition of mannitol, glycerol, reduced glutathione (GSH), or superoxide dismutase (SOD), known quenching agents of type I mechanisms, had little to no effect on the rate of inactivation of VSV. Significant inhibition of VSV kill was observed on addition of tryptophan or sodium azide, known quenchers of type II mechanisms. Additionally, the rate of VSV kill was enhanced in the presence of D2O. Taken together, these results indicate a predominant role of singlet oxygen in the inactivation of VSV on photodynamic treatment of RBCC. The relative importance of type I and type II mechanisms on cellular toxicity was also evaluated. Little, if any hemoglobin release was observed on treatment of human or rabbit RBCC with 10 microM AlPcS4 and 44 J/cm2 of visible light in the presence or absence of the above mentioned quenchers. The effect of the addition of quenchers on the recovery and circulatory survival of treated, autologous rabbit RBCC, labeled with 51Cr, was also assessed.(ABSTRACT TRUNCATED AT 250 WORDS)

Virus inactivation in red blood cell concentrates (RBCC) is being studied in order to increase the safety of the blood supply. For this purpose we have been studying the silicon phthalocyanine (Pc 4), a photosensitizer activated with red light. Two approaches were used to achieve enhanced selectivity of Pc 4 for virus inactivation. One was formulation of Pc 4 in liposomes that reduce its binding to red cells. The other was the use of a light emitting diode (LED) array emitting at 700 nm. Vesicular stomatitis virus (VSV) infectivity served as an endpoint for virus kill in treated RBCC. Red cell hemolysis and circulatory survival in rabbits served as measures for red cell damage. Treatment of small aliquots of human RBCC with 2 μM Pc 4 in liposomes and 10 J/cm2 of 700 nm LED light in the presence of the quenchers of reactive oxygen species glutathione and trolox resulted in 6 log10 inactivation of VSV. Under these conditions hemolysis of treated red cells stored at 4 °C for 21 days was only slightly above that of control cells. Rabbit RBCC similarly treated circulated with a half life of 7.5 days compared with 10.5 days of control. It is concluded that Pc 4 used as described here may be useful for viral decontamination of RBCC, pending toxicological and clinical studies. © 1999 Society of Photo-Optical Instrumentation Engineers.

These results extend those observed in our earlier 1-unit transfusion studies and suggest that ECO RBCs pose little risk and will be useful in transfusion medicine.