Inactivation of Babesia microti in red blood cells and platelet concentrates.

BACKGROUND: With an increasing number of recognized transfusion-transmitted (TT) babesiosis cases, Babesia microti is the most frequently TT parasite in the United States. We evaluated the inactivation of B. microti in red blood cells (RBCs) prepared in Optisol (AS-5) using amustaline and glutathione (GSH) and in platelet components (PCs) in 100% plasma using amotosalen and low-energy ultraviolet A (UVA) light. STUDY DESIGN AND METHODS: Individual RBCs and apheresis PCs were spiked with B. microti-infected hamster RBCs (iRBCs) to a final concentration of 106 iRBCs/mL and treated with the respective inactivation systems according to the manufacturer's instruction. Samples were collected before (control) and after (test) each treatment. Dilutions of the control samples to 10-6 were inoculated into hamsters, while the test samples were inoculated neat or at 10-1 dilution. At 3 and 5 weeks postinoculation, hamsters were evaluated for B. microti infection by microscopic observation of blood smears and 50% infectivity titers (ID50 ) were determined. Log reduction was calculated as control log ID50 minus test log ID50 . RESULTS: Parasitemia was detected in hamsters injected with as low as 100,000-fold diluted control samples, while no parasites were detectable in the blood smears of any hamsters receiving neat test samples. Mean log reduction was more than 5 log/mL by amustaline/GSH for RBCs and more than 4.5 log/mL by amotosalen/UVA for PCs. CONCLUSION: B. microti was inactivated to the limit of detection in RBCs and PCs after the respective inactivation treatment. Complete inactivation of B. microti was achieved in this animal infectivity model, and pathogen reduction treatment inhibited transmission of infection.

Riboflavin and ultraviolet light reduce the infectivity of Babesia microti in whole blood.

BACKGROUND: Babesia microti is the parasite most frequently transmitted by blood transfusion in the United States. Previous work demonstrated the efficacy of riboflavin (RB) and ultraviolet (UV) light to inactivate B.microti in apheresis plasma and platelet units. In this study we investigated the effectiveness of RB and UV light to reduce the levels of B.microti in whole blood (WB). STUDY DESIGN AND METHODS: WB units were spiked with B. microti-infected hamster blood. Spearman-Karber methods were used to calculate infectivity of each sample in terms of hamster infectious dose 50% (HID50 ) value. After RB addition, the units were illuminated with 80 J/mLRBC UV light. Two samples were collected: one before illumination and one after illumination. The samples were serially diluted and dilutions injected into a group of five naive hamsters. Four weeks postinoculation (PI), blood was collected from the animals and evaluated by microscopic observation. RESULTS: One pilot study showed a good dose response in the animals and demonstrated that sample infectivity could be calculated in terms of an HID50 . Three additional replicates were performed in the same manner as the pilot study, but with fewer dilutions. Infectivity values were consistent between the experiments and were used to calculate log reduction. The posttreatment reduction of B. microti for all the experiments was more than 5 log. CONCLUSIONS: The data collected indicate that use of RB and UV is able to decrease the parasite load in WB units thus reducing the risk of transfusion-transmitted B. microti from blood components containing B. microti-infected RBCs.

Evaluating pathogen reduction of Trypanosoma cruzi with riboflavin and ultraviolet light for whole blood.

BACKGROUND: Trypanosoma cruzi, the protozoan parasitic agent of Chagas disease, can be transmitted by blood transfusion. In 2007, most US blood banks started screening blood donations for T. cruzi, but the cost and perceived need of the test have been the subject of ongoing discussion. In this study, we evaluated the ability of the Mirasol System (CaridianBCT), which uses riboflavin (RB) and ultraviolet light to inactivate pathogens, to reduce the levels of infectious T. cruzi in whole blood (WB). STUDY DESIGN AND METHODS: WB units were inoculated with 4, 40, 400, and 4000 trypomastigotes/mL. After addition of RB and illumination at various energy levels, the samples were tested for the presence of live parasites by hemoculture. RESULTS: All preillumination samples exhibited T. cruzi growth in hemoculture, while postillumination samples from units containing 4 and 40 trypomastigotes/mL showed no signs of viable parasites after 16 weeks of culture. In contrast, at both 400 and 4000 parasites/mL, two of the three units were positive for viable parasites. CONCLUSIONS: The total log reduction observed for T. cruzi was 3.5 log or greater, but less than 4.5 log. This level of reduction is likely to be orders of magnitude higher than what would be expected in a tainted blood donation, indicating that the Mirasol System could be effective at preventing transfusion of the causative agent of Chagas disease.