Photochemical eradication of methicillin-resistant Staphylococcus aureus by blue light activation of riboflavin.

PURPOSE: To compare elimination of methicillin-resistant Staphylococcus aureus (MRSA) by exposure of blue light alone and with riboflavin. METHODS: A reference strain of MRSA was cultured and diluted in PBS with and without riboflavin (0.01%). Fifteen microlitre was added on a microscope slide, creating a fluid layer with a thickness of around 400 microns. Both of the bacterial suspensions were exposed to blue light, and the effect between exposure with and without riboflavin was compared. Evaluation involved two different wavelengths (412 and 450 nm) of blue light with a lower (5.4 J/cm2 ) and higher dose (approximately 28.5 J/cm2 ). The effect of 412 nm light was also evaluated for a thicker fluid layer (1.17 mm). After exposure, colony-forming units (CFUs) were determined for each solution. All measurements were repeated eight times. RESULTS: The reductions in bacteria were similar for both wavelengths. With riboflavin, a statistically significant elimination was observed for both 412 and 450 nm (p < 0.001). At both dosages, the mean reduction was more pronounced with the presence of riboflavin than without it. Using the higher dose, CFU reduction was 99% and 98%, respectively, for 412 and 450 nm light. The bactericidal efficacy was high also in the deeper fluid layer (93%, higher dose). CONCLUSION: Riboflavin enhanced the antibacterial effect on the exposed MRSA strain of blue light for both 412 and 450 nm blue light. This indicates that blue light could be considered for possible implementation in deep corneal infections.

Treatment of whole blood with riboflavin plus ultraviolet light, an alternative to gamma irradiation in the prevention of transfusion-associated graft-versus-host disease?

BACKGROUND: Exposure of blood products to gamma irradiation is currently the standard of care in the prevention of transfusion-associated graft-versus-host disease (TA-GVHD). Regulatory, technical, and clinical challenges associated with the use of gamma irradiators are driving efforts to develop alternatives. Pathogen reduction methods were initially developed to reduce the risk of microbial transmission by blood components. Through modifications of nucleic acids, these technologies interfere with the replication of both pathogens and white blood cells (WBCs). To date, systems for pathogen and WBC inactivation of products containing red blood cells are less well established than those for platelets and plasma. STUDY DESIGN AND METHODS: In this study, the in vitro and in vivo function of WBCs present in whole blood after exposure to riboflavin plus ultraviolet light (Rb-UV) was examined and compared to responses of WBCs obtained from untreated or gamma-irradiated blood by measuring proliferation, cytokine production, activation, and antigen presentation and xenogeneic (X-)GVHD responses in an in vivo mouse model. RESULTS: In vitro studies demonstrated that treatment of whole blood with Rb-UV was as effective as gamma irradiation in preventing WBC proliferation, but was more effective in preventing antigen presentation, cytokine production, and T-cell activation. Consistent with in vitro findings, treatment with Rb-UV was as effective as gamma irradiation in preventing X-GVHD, a mouse model for TA-GVHD. CONCLUSION: The ability to effectively inactivate WBCs in fresh whole blood using Rb-UV, prior to separation into components, provides the transfusion medicine community with a potential alternative to gamma irradiation.

In vitro quality of single-donor platelets treated with riboflavin and ultraviolet light and stored in platelet storage medium for up to 8 days.

BACKGROUND: The Mirasol pathogen reduction technology system is known to increase the activation and metabolic rate of platelets (PLTs). Storage of Mirasol PLTs in PLT storage medium (PSM) has the potential to slow this accelerated PLT storage lesion. We investigated the quality of Mirasol-treated PLTs stored in either 50% SSP+ or 50% Composol for 8 days. STUDY DESIGN AND METHODS: Single-donor double hyperconcentrates were divided between control and Mirasol-treated arms and after treatment were suspended in approximately 50% (vol/vol) SSP+ (n = 8) or Composol (n = 7). In vitro markers of PLT activation and/or apoptosis were measured over an 8-day storage period. RESULTS: Mirasol treatment resulted in increased spontaneous PLT activation and glycolysis and these effects were worsened when PLTs were treated below a certain volume (150 mL). At higher treatment volumes there were no significant differences between treated units stored in either Composol or SSP+. When low-volume units were stored in Composol the median pH fell below 6.4 on Day 5 and bicarbonate was undetectable, whereas in SSP+ the median pH value was greater than 6.9 and bicarbonate remained at detectable levels, despite other markers of in vitro function being similar to those of Composol. CONCLUSION: Mirasol treatment of PLTs followed by storage in PSM results in increased PLT activation and metabolism to a level similar to that reported for PLTs treated and stored in plasma. Units treated at a low volume (<150 mL) showed poor in vitro quality.

The Mirasol Pathogen Reduction Technology system and quality of platelets stored in platelet additive solution.

BACKGROUND: The Mirasol Pathogen Reduction Technology system for platelets and plasma uses riboflavin and UV light to introduce irreparable lesions into nucleic acids thereby inhibiting pathogen and white blood cell replication and reducing the load of infectious pathogens. The aim of the present study was to evaluate low plasma buffy coat platelet concentrates obtained from the OrbiSac System and to examine the effects on the development of platelet storage lesion during storage in platelet additive solution. MATERIAL AND METHODS: Twenty buffy coat platelet concentrates were generated by pooling five individual units using the OrbiSac System. Riboflavin was added during the final pooling step, and the units were exposed to UV light. The bag was removed after the target energy of 6.24 J/mL had been delivered and 150 mL of platelet additive solution were added prior to storage. Platelet quality was assessed by pH, swirl, CD62P expression, lactate dehydrogenase, lactate production and glucose consumption rates over 7 days of storage. RESULTS: Buffy coat platelet concentrates generated on the OrbiSac contained an average 3.5 +/- 0.6 x 10(11) platelets at a concentration of 2976+/- 406 x 10(6)/mL. After addition of 150 mL platelet additive solution the storage concentration was 1043 +/- 148x 10(6)/mL. Values obtained for pH, lactate production and glucose consumption rates were all within the limits of previously established correlations between in vitro cell quality and in vivo performance of Pathogen Reduction Technology-treated platelets in plasma. DISCUSSION: In vitro studies show that OrbiSac-derived platelets treated with the Mirasol Pathogen Reduction Technology system preserve adequate function, which would indicate acceptable in vitro viability.

Evaluation of Different Preparation Procedures of Pathogen Reduction Technology(Mirasol®)-Treated Platelets Collected by Plateletpheresis.

SUMMARY: BACKGROUND: The Mirasol® pathogen reduction technology (PRT) for platelet concentrates (PC) uses riboflavin and UV light (270-360 nm). We evaluated the impact of PRT on platelets in comparison to standard single-donor PC. MATERIAL AND METHODS: Platelets were resuspended in autologous plasma. After 2 h rest without agitation, PC were split into an untreated control unit (C-PC) and an immediately treated unit (T-PC) (series I). In series IV, split PC were stored under agitation over night before PRT was carried out. Platelet quality was assessed by pH, glucose consumption, lactate production rate, LDH, soluble sCD62p and CD62p expression with and without TRAP (thrombin receptor-activating peptide) over 7 days. RESULTS: SERIES I: On day 5, pH values were lower for T-PC (6.8 ± 0.2 vs. 7.4 ± 0.1, C-PC), accompanied by a higher glucose consumption rate of 0.069 ± 0.016 vs. 0.035 ± 0.006 mmol/10(12) platelets/h and lactate production rate of 0.126 ± 0.031 vs. 0.063 ± 0.011 mmol/10(12) platelets/h. CD62p using TRAP was lower for T-PC (50 ± 11 vs. 62 ± 14%). Baseline activation was higher in T-PC (35 ± 12 vs. 28 ± 15%). Longer initial rest time had no impact on these results (series II/III/IV). CONCLUSION: PRT leads to an increase of platelet metabolism and activation independent of the length of the initial rest times. PC resuspended in autologous plasma should be stored at maximum up to day 5.