Viral reduction of human blood by ultraviolet A-photosensitized vitamin K5.

Blood product transfusion can transmit viral pathogens. Pathogen reduction methods for blood products have been developed but, so far, are not available for whole blood. We evaluated if vitamin K5 (VK5) and ultraviolet A (UVA) irradiation could be used for virus inactivation in plasma and whole blood. Undiluted human plasma and whole blood diluted to 20% were spiked with high levels of vaccinia or Zika viruses. Infectious titers were measured by standard TCID50 assay before and after VK5/UVA treatments. Up to 3.6 log of vaccinia and 3.2 log of Zika were reduced in plasma by the combination of 500 µM VK5 and 3 J/cm2 UVA, and 3.1 log of vaccinia and 2.9 log of Zika were reduced in diluted human blood (20%) by the combination of 500 µM VK5 and 70 J/cm2 UVA. At end of whole blood treatment, hemolysis increased from 0.18% to 0.41% but remained below 1% hemolysis, which is acceptable to the Food and Drug Administration for red cell transfusion products. No significant alteration of biochemical parameters of red blood cells occurred with treatment. Our results provide proof of the concept that a viral pathogen reduction method based on VK5/UVA may be developed for whole blood.

Synergistic bactericidal effects of pairs of photosensitizer molecules activated by ultraviolet A light against bacteria in plasma.

BACKGROUND: The current approach to reducing bacterial contamination in blood transfusion products is through detection or pathogen reduction methods, some of which utilize ultraviolet (UV) light photosensitizers. A small number of photosensitizers are being used as single agents in combination with UV light, but their efficacy can be limited against some pathogens. Benzophenone (BP) and vitamins B1, B6, and K3 have been identified as effective UVA photosensitizers for inactivation of bacteria. We evaluated whether combining pairs of photosensitizers in this group would have synergistic bactericidal effects on Gram-negative and Gram-positive bacteria. STUDY DESIGN AND METHODS: Bacteria species of Escherichia coli, Bacillus cereus, Staphylococcus aureus, and Klebsiella pneumoniae were mixed with 0 to 100 mM concentrations of photosensitizers and exposed to UVA irradiation at 18 J/cm2 to assess their bactericidal effects. RESULTS: Single photosensitizers irradiated with UVA produced a range of bactericidal activity. When combined in pairs, all demonstrated some synergistic bactericidal effects with up to 4-log reduction above the sum of activities of individual molecules in the pair against bacteria in plasma. Photosensitizer pairs with BP had the highest synergism across all bacteria. With vitamin K3 in the pair, synergism was evident for Gram-positive but not for Gram-negative bacteria. Vitamin B1 and vitamin B6 had the least synergism. These results indicate that a combination approach with multiple photosensitizers may extend effectiveness of pathogen reduction in plasma. CONCLUSIONS: Combining photosensitizers in pathogen reduction methods could improve bactericidal efficacy and lead to use of lower concentrations of photosensitizers to reduce toxicities and unwanted side effects.

Inactivation of bacteria in plasma by photosensitizers benzophenone and vitamins K3, B1 and B6 with UV A light irradiation.

BACKGROUND: A photosensitizer is a light-activated molecule that can generate reactive oxygen species or directly interact with nucleic acids. Both consequences can be applied to reduction of pathogens in various media and to selectively attack tumor cells. Numerous natural and synthesized photosensitizers have been identified for pathogen reduction. METHODS: The photosensitizers of vitamins K3 (VK3), B1 (VB1), B6 (VB6) and benzophenone (BP) were prepared in 100-200 µM of PBS solution, irradiated with UVA at 0-48 J/cm2 for absorption spectrum alterations analysis. Bacteria species of E. coli, B. cereus, S. aureus and K. pneumoniae were mixed with 0-200 mM concentration of compounds and exposed to UVA irradiation of different dose at 6, 12 or 18 J/cm2 to assess the bactericidal effects. RESULTS AND CONCLUSIONS: Over six logs CFU/ml reduction of E. coli suspended in PBS occurred after treatment with either VB1, VB6, VK3 or BP combined with UVA irradiation. When bacteria were suspended in plasma, two to seven logs reduction occurred depending on the UVA dose, photosensitizer concentration, and bacteria species. Among these photosensitizers, BP had the most potent bactericidal effect and is a promising UVA photosensitizer for pathogen reduction. The level of absorption spectrum alteration after UVA irradiation was profound for VK3 and VB6 but minimal for BP and VB1. The UV-vis absorption spectrum changes did not correlate with the bactericidal effect indicating that molecule modification by UVA light is not required for the bactericidal activity.