Inactivation of Plasmodium spp. in plasma and platelet concentrates using riboflavin and ultraviolet light.

Background: Photochemical treatment of blood products could help prevent transfusion-transmitted malaria and reduce the need for donor deferrals. In this study we evaluated the effectiveness of riboflavin and ultraviolet (UV) light against both Plasmodium falciparum, which causes the most severe form of human malaria, and Plasmodium yoelii, an in vivo murine model for malaria.

Study Design And Methods: Plasma and platelet (PLT) concentrates were inoculated with either P. falciparum- or P. yoelii-infected red blood cells (RBCs). Aliquots from each unit were collected after inoculation, after addition of riboflavin, and after treatment. In vitro P. falciparum growth was assessed using thin blood films of duplicate samples at 24, 48, 72, and 96 hours. P. yoelii parasitemia was followed in mice for 14 days postinoculation.

Results: In the in vitro studies, the mean P. falciparum parasitemia increased 12- to 19-fold in pretreatment samples, both before and after addition of riboflavin, after 96-hour culture. Few parasites were observed in Mirasol-treated units at 24 hours; those that were observed were degenerating. Through the remainder of the 96-hour culture period, cultures of treated samples were negative. In the in vivo study, mouse plasma containing P. yoelii-infected RBCs had a mean starting titer of 4.6 log mouse infectious dose 50%/mL. No infectious parasite was detected in treated samples.

Conclusion: Treatment with riboflavin and UV light was effective at reducing viable P. falciparum in both PLT and plasma products by at least 3.2 logs. Additionally, an at least 4.4-log reduction was observed with P. yoelii.