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.

Validation of a SCID mouse model for transfusion by concurrent comparison of circulation kinetics of human platelets, stored under various temperature conditions, between human volunteers and mice.

BACKGROUND: Initial evaluation of new platelet (PLT) products for transfusion includes a clinical study to determine in vivo recovery and survival of autologous radiolabeled PLTs in healthy volunteers. These studies are expensive and do not always produce the desired results. A validated animal model of human PLTs in vivo survival and recovery used pre-clinically could reduce the risk of failing to advance product development. STUDY DESIGN AND METHODS: An immunodeficient (SCID) mouse model to evaluate recovery of human PLTs was compared to a radiolabeling study in human volunteers. Autologous apheresis PLTs stored for 7 days at room temperature (RT), thermo-cycled (TC), and cold temperature (CT) were radiolabeled and infused into healthy humans (n = 16). The same PLTs, non-radiolabeled, were also infused into mice (n = 160) on the same day. Blood samples from humans and mice were collected to generate clearance curves of PLTs in circulation. Flow cytometry was used to detect human PLTs in mouse blood. RESULTS: Human and mouse PLTs were cleared with one phase exponential clearance. Relative differences for initial recovery and AUC, expressed as ratio of test and control PLTs, were similar in humans and mice. The initial recovery ratio of TC/RT was 0.73 ± 0.07 in humans and 0.67 ± 0.14 in mice. The ratio for CT/TC was 0.53 ± 0.06 in humans and 0.75 ± 0.18 in mice. CONCLUSION: The SCID mouse model can provide information on relative differences of initial in vivo recovery and AUC between control and alternatively stored/processed human PLTs that is predictive of performance in healthy human volunteers.

Temperature cycling during platelet cold storage improves in vivo recovery and survival in healthy volunteers.

BACKGROUND: Room temperature (RT) storage of platelets (PLTs) can support bacterial proliferation in contaminated units, which can lead to transfusion-transmitted septic reactions. Cold temperature storage of PLTs could reduce bacterial proliferation but cold exposure produces activation-like changes in PLTs and leads to their rapid clearance from circulation. Cold-induced changes are reversible by warming and periodic rewarming during cold storage (temperature cycling [TC]) has been proposed to alleviate cold-induced reduction in PLT circulation. STUDY DESIGN AND METHODS: A clinical trial in healthy human volunteers was designed to compare in vivo recovery, survival, and area under the curve (AUC) of radiolabeled autologous apheresis PLTs stored for 7 days at RT or under TC or cold conditions. Paired comparisons of RT versus TC and TC versus cold PLTs were conducted. RESULTS: Room temperature PLTs had in vivo recovery of 55.7 ± 13.9%, survival of 161.3 ± 28.8 hours, and AUC of 5031.2 ± 1643.3. TC PLTs had recovery of 42.6 ± 16.4%, survival of 48.1 ± 14.4% hours, and AUC of 1331.3 ± 910.2 (n = 12, p < 0.05). In a separate paired comparison, cold PLTs had recovery of 23.1 ± 8.8%, survival of 33.7 ± 14.7 hours, and AUC of 540.2 ± 229.6 while TC PLTs had recovery of 36.5 ± 12.9%, survival of 49.0 ± 17.3 hours, and AUC of 1164.3 ± 622.2 (n = 4, AUC had p < 0.05). CONCLUSION: TC storage for 7 days produced PLTs with better in vivo circulation kinetics than cold storage but is not equivalent to RT storage.

Proceedings of the Food and Drug Administration's public workshop on new red blood cell product regulatory science 2016.

The US Food and Drug Administration (FDA) held a workshop on red blood cell (RBC) product regulatory science on October 6 and 7, 2016, at the Natcher Conference Center on the National Institutes of Health (NIH) Campus in Bethesda, Maryland. The workshop was supported by the National Heart, Lung, and Blood Institute, NIH; the Department of Defense; the Office of the Assistant Secretary for Health, Department of Health and Human Services; and the Center for Biologics Evaluation and Research, FDA. The workshop reviewed the status and scientific basis of the current regulatory framework and the available scientific tools to expand it to evaluate innovative and future RBC transfusion products. A full record of the proceedings is available on the FDA website (http://www.fda.gov/BiologicsBloodVaccines/NewsEvents/WorkshopsMeetingsConferences/ucm507890.htm). The contents of the summary are the authors' opinions and do not represent agency policy.

Automated cold temperature cycling improves in vitro platelet properties and in vivo recovery in a mouse model compared to continuous cold storage.

BACKGROUND: Platelets (PLTs) stored at cold temperatures (CTs) for prolonged time have dramatically reduced bacterial growth but poor survival when infused. A previous study demonstrated that human PLTs stored with manual cycling between 4 °C (12 hr) and 37 °C (30 min) and infused into severe combined immunodeficient (SCID) mice had survivals similar to or greater than those stored at room temperature (RT). In this study, the in vitro and in vivo properties of PLTs stored in an automated incubator programmed to cycle between 5 °C (11 hr) and 37 °C (1 hr) were evaluated. STUDY DESIGN AND METHODS: A Trima apheresis unit (n = 12) was aliquoted (60 mL) in CLX bags. One sample was stored with continuous agitation (RT), a second sample was stored at 4-6 °C without agitation (CT), and a third sample was placed in an automated temperature cycler with 5 minutes of agitation during the warm-up period (thermocycling [TC]). PLTs were assayed for several relevant quality variables. On Day 7, PLTs were infused into SCID mice and in vivo recovery was assessed at predetermined time points after transfusion. RESULTS: The glucose consumption rate, morphology score, hypotonic shock recovery level, and aggregation levels were increased and mitochondrial reactive oxygen species accumulations were decreased in TC-PLTs compared to those of CT-PLTs. The pH and Annexin V binding were comparable to those of RT-PLTs. All TC-PLTs had greater recovery than CT-PLTs and were comparable to RT-PLTs. CONCLUSION: PLTs stored under automated TC conditions have improved in vivo recovery and improved results for a number of in vitro measures compared to CT-PLTs.

Expression of the cellular prion protein affects posttransfusion recovery and survival of red blood cells in mice.

BACKGROUND: Cellular prion protein (PrP(C) ) is expressed on various cell types including red blood cells (RBCs). The PrP(C) plays a key role in the pathogenesis of prion diseases, but its physiologic function remains unclear. PrP(C) is expressed on CD34+ hematopoietic stem cells and its expression is regulated during blood cell differentiation including the erythroid line. STUDY DESIGN AND METHODS: We investigated the role of PrP(C) in RBC survival in circulation by transfusing a mix of biotin-labeled RBCs from wild-type (WT) and PrP knockout (KO) mice to groups of recipient mice (WT and KO). The proportion of biotinylated RBCs in peripheral blood was estimated by flow cytometry. RESULTS: KO RBCs displayed a markedly higher first-day posttransfusion recovery but had a decreased survival in circulation when compared to WT RBCs. Similar results were obtained in all groups of transfused mice, irrespective of RBCs biotinylation level. In addition, we confirmed this finding in an analogous study using Tga20 mice overexpressing PrP(C) and KO mice of a different genetic background. CONCLUSION: Our results demonstrate that PrP(C) expression affects RBC recovery and survival in circulation.

Human platelets pathogen reduced with riboflavin and ultraviolet light do not cause acute lung injury in a two-event SCID mouse model.

BACKGROUND: Pathogen reduction technologies (PRTs) can induce platelet (PLT) lesions that reduce PLT survival and recovery from circulation and may be associated with acute lung injury (ALI). STUDY DESIGN AND METHODS: Human PLTs (hPLTs) in plasma with or without single or multiple Mirasol PRT treatments were assessed in vitro by aggregation and percentage of P-selectin expression. In vivo studies included PLT recovery in SCID mice and assessment of ALI in a two-event mouse model in which the sensitizing event was lipopolysaccharide injection and the second event was infusion of Mirasol-treated hPLTs. RESULTS: A single-dose Mirasol treatment (5 J/cm(2) ) did not induce any change in aggregation in response to adenosine 5'-diphosphate (ADP) while a five-times-repeat Mirasol treatment (5×) increased aggregation response to low concentration of ADP. Mirasol PLTs (1×-5×) had increased percentage of P-selectin-positive PLTs after treatment and decreased aggregation with TRAP as the agonist. In vivo recovery in SCID mice was reduced extensively with Mirasol treatments (1× and 5×). In the two-event model of ALI, only the 5× Mirasol PLTs accumulated in the lung and this was not accompanied by changes in lung histology or increases in MIP-2 levels in bronchoalveolar lavage fluid. CONCLUSIONS: Mirasol PRT treatment induced PLT activation and reduced in vivo recovery in a SCID mouse model of transfusion. In our two-event mouse model of ALI, the 5× Mirasol hPLTs accumulated in the lung, but did not cause signs of ALI. The 1× Mirasol treatment did not lead to PLT lung accumulation or ALI in this model.

Ultraviolet light and riboflavin accelerates red blood cell dysfunction in vitro and in a guinea pig transfusion model.

BACKGROUND: Quality assessment of modified or processed red blood cell (RBC) components, such as pathogen-reduced RBCs, using only in vitro testing may not always be predictive of in vivo performance. Mouse or rat in vivo models are limited by a lack of applicability to certain aspects of human RBC biology. Here, we used a guinea pig model to study the effects of riboflavin combined with UV light on the integrity of RBCs in vitro and following transfusion in vivo. MATERIALS AND METHODS: Guinea pig RBCs were collected from whole blood (WB) treated with varying UV doses (10, 20, 40 or 80 J/mL) in the presence of riboflavin (UVR-RBCs). In vitro tests for UVR-RBCs included hemolysis, osmotic fragility, and cellular morphology by scanning electron microscopy. Guinea pigs transfused with one-day post-treatment UVR-RBCs were evaluated for plasma hemoglobin (Hb), non-transferrin bound iron (NTBI), total iron and Perls-detectable hemosiderin deposition in the spleen and kidney, and renal uptake of Hb. RESULTS: Acute RBC injury was dose dependently accelerated after treatment with UV light in the presence of riboflavin. Aberrant RBC morphology was evident at 20, 40, and 80 J/mL, and membrane lysis with Hb release was prominent at 80 J/mL. Guinea pigs transfused with 40 and 80 J/mL UVR-RBCs showed increased plasma Hb levels, and plasma NTBI was elevated in all UVR-RBC groups (10-80 J/mL). Total iron levels and Perls-hemosiderin staining in spleen and kidney as well as Hb uptake in renal proximal tubules were increased 8 hours post-transfusion with 40 and 80 J/mL UVR-RBCs. DISCUSSION: UVR-RBCs administered to guinea pigs increased markers of intravascular and extravascular hemolysis in a UV dose-dependent manner. This model may allow for the discrimination of RBC injury during testing of extensively processed RBCs intended for transfusion.

Activation of platelet protein kinase C by ultraviolet light B mediates platelet transfusion-related acute lung injury in a two-event animal model.

BACKGROUND: We recently reported that infusion of ultraviolet light B (UVB)-exposed human platelets (HPs) can be the second event that mediates acute lung injury (ALI) in a two-event mouse model of transfusion-related acute lung injury (mTRALI). We have now identified changes in HPs induced by UVB light and responses of the recipient animal that mediate the mTRALI. STUDY DESIGN AND METHODS: Effects of UVB on HPs were monitored by flow cytometry and aggregation. HPs exposed to UVB, with or without inhibitors to specific biochemical pathways, were infused into lipopolysaccharide (LPS)-primed severe combined immunodeficient (SCID) mice. ALI was monitored by protein elevations in bronchoalveolar lavage fluid (BALF). RESULTS: UVB increased fibrinogen binding and potentiated HP aggregation. Infusion of UVB HPs into LPS-primed SCID mice led to macrophage inflammatory protein 2 (MIP-2) elevations in plasma and BALF and resulted in ALI. Protein kinase C (PKC) inhibitors prevented UVB-induced HP changes in vitro and reduced MIP-2 elevation and mTRALI in vivo. Blocking of fibrinogen binding to HP αIIbß3 with c7E3 monoclonal antibody prevented mTRALI. MIP-2 elevation in vivo in response to UVB HPs was essential for ALI since blocking of MIP-2 receptor in vivo prevented mTRALI. CONCLUSION: PKC signaling mediates UVB-induced HP fibrinogen binding and aggregation in vitro. The host animal responds to an infusion of UVB HPs by MIP-2 elevation that mediates downstream mTRALI. Elucidation of molecular mechanisms in UVB HP-mediated mTRALI may provide insight into pulmonary adverse events reported with UV-irradiated pathogen-reduced platelets.

Temperature cycling improves in vivo recovery of cold-stored human platelets in a mouse model of transfusion.

BACKGROUND: Platelet (PLT) storage at room temperature (RT) is limited to 5 days to prevent growth of bacteria, if present, to high levels. Storage in cold temperatures would reduce bacterial proliferation, but cold-exposed PLTs are rapidly cleared from circulation by the hepatic Ashwell-Morell (AM) receptor, which recognizes PLT surface carbohydrates terminated by ß-galactose. We cycled storage temperature between 4 and 37°C to preserve PLT function and reduce bacterial growth. STUDY DESIGN AND METHODS: Temperature-cycled (TC) human PLTs were stored at 4°C for 12 hours and then incubated at 37°C for 30 minutes before returning back to cold storage. PLTs stored at RT or at 4°C (COLD) or TC for 2, 5, and 7 days were infused into SCID mice and the in vivo recovery was determined at 5, 20, and 60 minutes after transfusion. RESULTS: PLTs stored for 2 days in COLD had significantly lower in vivo recoveries than RT PLTs. TC PLTs had improved recoveries over COLD and comparable to RT PLTs. After 5- and 7-day storage, TC PLTs had better recoveries than RT and COLD PLTs. PLT surface ß-galactose was increased significantly for both COLD and TC PLTs compared to RT. Blocking of the AM receptor by asialofetuin increased COLD but not TC PLT recovery. CONCLUSION: TC cold storage may be an effective method to store PLTs without loss of in vivo recovery. The increased ß-galactose exposure in TC PLTs suggests that mechanisms in addition to AM receptors may mediate clearance of cold-stored PLTs.

Rejuvenation improves roller pump-induced physical stress resistance of fresh and stored red blood cells.

BACKGROUND: Retrospective studies on transfusion recipients suggested that transfusion of older red blood cells (RBCs) was associated with higher morbidity. Similar studies were also done on cardiac surgery patients who were placed on cardiac bypass pumps. It is possible that stored RBCs are more fragile and could be more easily damaged by these pumps, thus leading to additional morbidity. STUDY DESIGN AND METHODS: Fresh and stored (42 days) RBCs, rejuvenated and nonrejuvenated, were compared in resistance to physical stress, induced by a roller pump, and osmotic fragility changes during physical stress to model RBCs going through cardiac bypass instruments. In addition, posttransfusion in vivo recovery was evaluated in an immunodeficient mouse model to minimize species differences between transfusion product and recipient. RESULTS: Fresh RBCs were more resistant to both osmotic and physical stress than stored cells. After 2 hours of physical stress, the osmotic stress resistance of fresh cells declined and was the same as for stored cells. Rejuvenated fresh cells did not demonstrate a decline in osmotic resistance during the stress test and both fresh and stored cells had the same improved resistance to osmotic stress before and after the physical stress. Rejuvenation slightly improved recovery of fresh RBCs but almost doubled the recovery of stored cells in the mouse model. CONCLUSIONS: Our studies suggest that rejuvenation improves roller pump-induced physical and osmotic stress resistance of stored RBCs.

Ultraviolet B light-exposed human platelets mediate acute lung injury in a two-event mouse model of transfusion.

BACKGROUND: Ultraviolet B (UVB) light has been used alone on platelet (PLT) transfusion products to prevent alloimmunization or with chemical sensitizers to reduce pathogens. Such processing can damage PLTs and potentiate their storage lesion. Transfusion-related acute lung injury (ALI) has occurred in patients whose underlying condition led to an inflamed endothelium and who were transfused with products that contained either HLA or HNA antibodies or biologic modifiers such as lipids or antigens from stored cells. Clinical trials of UV-treated PLTs in patients with thrombocytopenia generated controversy regarding association of these cells with respiratory distress. We evaluated whether UVB PLTs could mediate ALI in an animal model of ALI. STUDY DESIGN AND METHODS: We used a two-event animal model where the sensitizing event was lipopolysaccharide (LPS) and the second event was infusion of human PLTs or UVB human PLTs (2.4 J/cm(2) ). Infused human PLTs were followed with whole animal imaging, lung histology, confocal microscopy, lung water, and changes in bronchoalveolar lavage fluid (BALF) related to ALI. RESULTS: In LPS-treated mice UVB human PLTs accumulated in the lungs and were associated with ALI manifested by increased protein and white blood cells (WBCs) in BALF. Untreated human PLTs did not accumulate in the lungs or increase BALF protein or WBC counts. CONCLUSIONS: We provide a proof of principle that UVB human PLTs can accumulate in lungs of LPS-primed animals and mediate ALI. PLTs exposed to high doses of UVB could potentially mediate similar effects in patients predisposed with sepsis or other causes of endothelial cell inflammation.

Underestimation of the expression of cellular prion protein on human red blood cells.

BACKGROUND: Recent transmissions of variant Creutzfeldt-Jakob disease by blood transfusion emphasize the need for the development of prion screening tests. The detection of prions in blood is complicated by the presence of poorly characterized cellular prion protein (PrP(C) ) in both plasma and blood cells. According to published studies, most of PrP(C) in blood cells resides in platelets (PLTs) and white blood cells. STUDY DESIGN AND METHODS: To clarify conflicting reports about the quantity of PrP(C) associated with human red blood cells (RBCs), quantitative flow cytometry, Western blot (WB), and enzyme-linked immunosorbent assay (ELISA) were used to measure protein levels in healthy donors. RESULTS: RBCs expressed 290 ± 140 molecules of PrP(C) per cell, assuming equimolar binding of monoclonal antibody (MoAb) 6H4 to PrP(C). Binding of alternate PrP(C) MoAbs, FH11 and 3F4, was substantially lower. WB estimated the level of PrP(C) per cell on RBCs to be just four times lower than in PLTs. A similar level of PrP(C) was detected using ELISA. The weak binding of commonly used MoAb 3F4 was not caused by PrP(C) conformation, truncation, or glycosylation, suggesting a covalent modification, likely glycation, of the 3F4 epitope. CONCLUSIONS: Taken together, human RBCs express low but significant amounts of PrP(C) /cell, which makes them, due to high RBC numbers, major contributors to the pool of cell-associated PrP(C) in blood. Previous reports utilizing MoAb 3F4 may have underestimated the amount of PrP(C) in RBCs. Likewise, screening tests for the presence of the abnormal prion protein in blood may be difficult if the abnormal protein is modified similar to RBC PrP(C).

P38 mitogen activated protein kinase inhibitor improves platelet in vitro parameters and in vivo survival in a SCID mouse model of transfusion for platelets stored at cold or temperature cycled conditions for 14 days.

Platelets for transfusion are stored at room temperature (20-24°C) up to 7 days but decline in biochemical and morphological parameters during storage and can support bacterial proliferation. This decline is reduced with p38MAPK inhibitor, VX-702. Storage of platelets in the cold (4-6°C) can reduce bacterial proliferation but platelets get activated and have reduced circulation when transfused. Thermocycling (cold storage with brief periodic warm ups) reduces some of the effects of cold storage. We evaluated in vitro properties and in vivo circulation in SCID mouse model of human platelet transfusion of platelets stored in cold or thermocycled for 14 days with and without VX-702. Apheresis platelet units (N = 15) were each aliquoted into five storage bags and stored under different conditions: room temperature; cold temperature; thermocycled temperature; cold temperature with VX-702; thermocycled temperature with VX-702. Platelet in vitro parameters were evaluated at 1, 7 and 14 days. On day 14, platelets were infused into SCID mice to assess their retention in circulation by flow cytometry. VX-702 reduced negative platelet parameters associated with cold and thermocycled storage such as an increase in expression of activation markers CD62, CD63 and of phosphatidylserine (marker of apoptosis measured by Annexin binding) and lowered the rise in lactate (marker of increase in anaerobic metabolism). However, VX-702 did not inhibit agonist-induced platelet aggregation indicating that it does not interfere with platelet hemostatic function. In vivo, VX-702 improved initial recovery and area under the curve in circulation of human platelets infused into a mouse model that has been previously validated against a human platelet infusion clinical trial. In conclusion, inhibition of p38MAPK during 14-days platelet storage in cold or thermocycling conditions improved in vitro platelet parameters and platelet circulation in the mouse model indicating that VX-702 may improve cell physiology and clinical performance of human platelets stored in cold conditions.

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.

Human cellular prion protein interacts directly with clusterin protein.

Prion protein is a glycosyl-phosphatidyl-inositol anchored glycoprotein localized on the surface and within a variety of cells. Its conformation change is thought to be essential for the proliferation of prion neurodegenerative diseases. Using the yeast two-hybrid assay we identified an interaction between prion protein and clusterin, a chaperone glycoprotein. This interaction was confirmed in a mammalian system by in vivo co-immunoprecipitation and in vitro by circular dichroism analysis. Through deletion mapping analysis we demonstrated that the alpha subunit, but not the beta subunit, of clusterin binds to prion and that the C-terminal 62 amino acid segment of the putative alpha helix region of clusterin is essential for the binding interaction. The full prion protein as well as the N-terminal section (aa 23-95) and C-terminal (aa 96-231) were shown to interact with clusterin. These findings provide new insights into the molecular mechanisms of interaction between prion and clusterin protein and contribute to the understanding of prion protein's physiological function.

Macrophage Depletion Mitigates Platelet Aggregate Formation in Splenic Marginal Zone and Alleviates LPS-Associated Thrombocytopenia in Rats.

Sepsis is often accompanied with thrombocytopenia partly due to platelet sequestration in the lung and liver. The spleen can store up to one-third of circulating platelets and can also significantly affect platelet transfusion outcomes by accumulating platelets. However, in sepsis, it is not clear whether there are platelet changes in the spleen which could contribute to sepsis-associated thrombocytopenia and also influence platelet transfusion outcomes. By using confocal microscopy, we examined endogenous rat platelets and infused human platelets in the spleen of severe combined immune deficient Rag2 KO rats which were injected intraperitoneally with lipopolysaccharide (LPS). LPS-injected Rag2 KO rats developed sepsis as indicated by increased TNFa, IL-6, IL-1b, and IL-10 levels and thrombocytopenia. Large platelet aggregates were observed in the spleen with majority located in the marginal zone and closely associated with CD169+ macrophages. Depletion of macrophages by clodrosome resulted in reduction of LPS-induced cytokine generation and alleviated LPS-induced thrombocytopenia. Macrophage depletion also remarkedly diminished large platelet aggregate formation in the splenic marginal zone but had less effect on those in red pulp. Infusion of human platelets into LPS-injected rats failed to raise platelet counts in the peripheral blood. In LPS-injected rat spleen, human platelets interacted with aggregated rat platelets in the marginal zone. In contrast, human platelets infused into control rats were located outside of splenic marginal zone. This study provides morphological evidence of platelet aggregates in the splenic marginal zone in sepsis which can interact with infused platelets and thus can contribute to platelet infusion refractoriness in sepsis. It indicates that macrophages play an important role in LPS-associated thrombocytopenia. It also suggests that CD169+ macrophages support platelet aggregate formation in the splenic marginal zone.

Reduced erythroid cell and erythropoietin production in response to acute anemia in prion protein-deficient (Prnp-/-) mice.

Cellular prion protein (PrPc) participates in the pathogenesis of prion diseases but its normal function remains unclear. PrPc is expressed on hematopoietic cells, including erythroid precursors. We investigated the role of PrPc in erythropoiesis in vivo with phenylhydrazine-induced acute anemia. Induction of equivalent anemia in wild-type (WT) and Prnp-/- mice resulted in a higher number of circulating reticulocytes, hematocrits and spleen weights in WT mice than in Prnp-/- mice on Days 5 and 7. Examination of bone marrow erythroid precursor cells (Ter119+) on Day 5 revealed no significant differences in the number of these cells between the two types of animals. However, a higher percentage of Ter119+ cells were going through apoptosis in Prnp-/- mice than in WT mice. Plasma erythropoietin (Epo) levels and Epo mRNA in kidneys peaked on Day 3 in response to anemia for both types of animals but rose less in Prnp-/- (5500 pg/ml ) than in WT (18,000 pg/ml) animals. Administration of recombinant human Epo to mice produced an equivalent reticulocyte response in both types of animals suggesting that the potential for erythroid generation is intact in Prnp-/- animals. These observations indicate that PrPc may modulate tissue hypoxia-sensing mechanisms or effect hypoxia target gene expression.