Ultraviolet-Based Pathogen Inactivation Systems: Untangling the Molecular Targets Activated in Platelets

Biotinylation of human platelets is compatible with pathogen inactivation treatment and cold storage for clinical studies

BACKGROUND

Production of platelet concentrates (PCs) involves several steps that significantly affect platelet behavior. To gain a deeper understanding of how storage conditions impact donor platelet recirculation and functionality post-transfusion, ex vivo platelet labeling is a feasible approach. However, before pursuing clinical investigations of platelet recirculation and function in humans, we aimed to determine the effects of pathogen inactivation technology (PIT) and storage conditions (4°C vs. room temperature [RT]) on phenotype and function of biotinylated platelets compared to conventional PIT PCs for transfusion.

METHODS

Nine PCs were prepared in 61% additive solution from 45 buffy coats (five buffy coats each). A pool-and-split of three units was used to prepare three equivalent PCs: two labeled with biotin and stored at RT or 4°C, and one without labeling and stored at RT. All PCs were then treated by PIT (amotosalen/UVA) and stored for 14 days. Labeling efficiency, platelet concentration, metabolic parameters, aggregation response (ADP, collagen, co-aggregation with epinephrine), and platelet phenotype (CD42b, CD62-P, phosphatidylserine) at the basal stage and upon stimulation (ADP or TRAP-6) were performed.

RESULTS

Labeling efficiency of PIT and 4°C PCs was stable over 14 days of storage. Differences in platelet function and phenotype were mainly due to the storage temperature and not the biotinylation process. Phenotypes at baseline or after stimulation were equivalent in biotin-positive and biotin-negative platelets.

CONCLUSION

Biotin-labeled platelets can effectively enable investigation of the effects of PIT and storage temperature for clinical studies. This method shows great potential for improving platelet transfusion knowledge.

Increase of Phosphoprotein Expressions in Amotosalen/UVA-Treated Platelet Concentrates

Background

Pathogen inactivation treatment (PIT) has been shown to alter platelet function, phenotype, morphology and to induce a faster aging of platelet concentrates (PCs). Key pieces of information are still missing to understand the impacts of PITs at the cellular level.

Objectives

This study investigated the impact of amotosalen/UVA on PCs, from a post-translational modifications (PTM) point of view. Phosphoproteomic analyses were conducted on resting platelets, right after the amotosalen/UVA treatment and compared with untreated PCs.

Method

A two-arm study setting was carried out to compare PIT (amotosalen/UVA) to untreated PCs, on day 1 post-donation. Based on a pool-and-split approach, 12 PCs were split into two groups (treated and untreated). Quantitative phosphoproteomics was performed using TMT technology to study the changes of phosphoproteins right after the PIT.

Results

A total of 3,906 proteins and 7,334 phosphosites were identified, and 2,473 proteins and 2,214 phosphosites were observed in at least 5 to 6 replicates. Compared to untreated platelets, PIT platelets exhibited an upregulation of the phosphorylation effects, with 109 phosphosites identified with a higher than 2-fold change. Two pathways were clearly identified. The mitogen activated protein kinases (MAPKs) cascade, which triggers the granule secretion and the activation of the pS15 HSPB1. One of the shape change pathways was also observed with the inhibition of the Threonine 18 and Serine 19 phosphorylations on myosin light chain (MLC) protein after the amotosalen/UVA treatment.

Conclusions

This work provides a deep insight into the impact of amotosalen/UVA treatment from a phosphoprotein viewpoint on resting platelets. Clear changes in phosphorylation of proteins belonging to different platelet pathways were quantified. This discovery corroborates previous findings and fills missing parts of the effect of photochemical treatments on platelets.

The Preclinical Validation of 405 nm Light Parasiticidal Efficacy on Leishmania donovani in Ex Vivo Platelets in a Rag2-/- Mouse Model

Violet-blue light of 405 nm in the visible spectrum at a dose of 270 J/cm2 alone has been shown to be an effective microbicidal tool for inactivating several bacteria, HIV-1, and Trypanosoma cruzi in ex vivo plasma and platelets. Unlike chemical- and ultraviolet (UV)-based pathogen inactivation methods for plasma and platelet safety, 405 nm light is shown to be less toxic to host cells at light doses that are microbicidal. In this report, we evaluated the parasiticidal activity of a 405 nm light treatment on platelets spiked with the Leishmania donovani parasite. Following the light treatment, parasite viability was observed to be near zero in both low- and high-titer-spiked platelets relative to controls. Furthermore, to test the residual infectivity after inactivation in vivo, the light-treated low-titer L. donovani-spiked platelets were evaluated in an immunodeficient Rag2-/- mouse model and monitored for 9 weeks. The parasiticidal efficacy of 405 nm light was evident from the lack of a presence of parasites in the mice spleens. Parasiticidal activity was confirmed to be mediated through 405 nm light-induced reactive oxygen species (ROS), as quantitatively measured by a 2',7'-Dichlorodihydrofluorescein diacetate (H2DCFDA)-based assay. Overall, these results confirm the complete inactivation of L. donovani spiked in ex vivo platelets by 405 nm light treatment and exemplify the utility of the Rag2-/- mouse infection model for the preclinical validation of the parasiticidal efficacy of 405 nm light and this light-based technology as a potential PRT for ex vivo platelets.

Cold-stored platelets for acute bleeding in cardiac surgical patients: a narrative review

PURPOSE

Cold-stored platelets (CSP) are an increasingly active topic of international research. They are maintained at 1-6 °C, in contrast to standard room-temperature platelets (RTP) kept at 20-24 °C. Recent evidence suggests that CSP have superior hemostatic properties compared with RTP. This narrative review explores the application of CSP in adult cardiac surgery, summarizes the preclinical and clinical evidence for their use, and highlights recent research.

SOURCE

A targeted search of MEDLINE and other databases up to 24 February 2022 was conducted. Search terms combined concepts such as cardiac surgery, blood, platelet, and cold-stored. Searches of trial registries ClinicalTrials.gov and WHO International Clinical Trials Registry Platform were included. Articles were included if they described adult surgical patients as their population of interest and an association between CSP and clinical outcomes. References of included articles were hand searched.

PRINCIPAL FINDINGS

When platelets are stored at 1-6 °C, their metabolic rate is slowed, preserving hemostatic function for increased storage duration. Cold-stored platelets have superior adhesion characteristics under physiologic shear conditions, and similar or superior aggregation responses to physiologic agonists. Cold-stored platelets undergo structural, metabolic, and molecular changes which appear to "prime" them for hemostatic activity. While preliminary, clinical evidence supports the conduct of trials comparing CSP with RTP for patients with platelet-related bleeding, such as those undergoing cardiac surgery.

CONCLUSION

Cold-stored platelets may have several advantages over RTP, including increased hemostatic capacity, extended shelf-life, and reduced risk of bacterial contamination. Large clinical trials are needed to establish their potential role in the treatment of acutely bleeding patients.

Human leukocyte antigen alloimmunization prevention mechanisms in blood transfusion

In many fields of clinical medicine and blood transfusion, the human leukocyte antigen (HLA) system is crucial. Alloimmunization happens as a result of an immune response to foreign antigens encountered during blood transfusion. This gives rise to alloantibodies against red blood cells (RBCs), HLA, or human platelet antigen (HPA). HLA alloimmunization following allogeneic transfusion was shown to be a result of contaminating white blood cells (WBCs) present in the product. It is a common complication of transfusion therapy that leads to difficulties in clinical intolerance and refractoriness to platelet transfusion during patient management. Single-donor platelets, prophylactic HLA matching, leukoreduction, and irradiation of cellular blood products are some of the mechanisms to prevent HLA alloimmunization during a blood transfusion. Now, the best approach to reduce the occurrence of primary HLA alloimmunization is the removal of WBCs from the blood by filtration.

Platelet transfusion in adults: An update

Many patients worldwide receive platelet components (PCs) through the transfusion of diverse types of blood components. PC transfusions are essential for the treatment of central thrombocytopenia of diverse causes, and such treatment is beneficial in patients at risk of severe bleeding. PC transfusions account for almost 10% of all the blood components supplied by blood services, but they are associated with about 3.25 times as many severe reactions (attributable to transfusion) than red blood cell transfusions after stringent in-process leukoreduction to less than 10⁶ residual cells per blood component. PCs are not homogeneous, due to the considerable differences between donors. Furthermore, the modes of PC collection and preparation, the safety precautions taken to limit either the most common (allergic-type reactions and febrile non-hemolytic reactions) or the most severe (bacterial contamination, pulmonary lesions) adverse reactions, and storage and conservation methods can all result in so-called PC "storage lesions". Some storage lesions affect PC quality, with implications for patient outcome. Good transfusion practices should result in higher levels of platelet recovery and efficacy, and lower complication rates. These practices include a matching of tissue ABH antigens whenever possible, and of platelet HLA (and, to a lesser extent, HPA) antigens in immunization situations. This review provides an overview of all the available information relating to platelet transfusion, from donor and donation to bedside transfusion, and considers the impact of the measures applied to increase transfusion efficacy while improving safety and preventing transfusion inefficacy and refractoriness. It also considers alternatives to platelet component (PC) transfusion.

Ultrafast-UV laser integrating cavity device for inactivation of SARS-CoV-2 and other viruses

Ultraviolet (UV) irradiation-based methods used for viral inactivation have provided an important avenue targeting severe acute respiratory-syndrome coronavirus-2 (SARS-CoV-2) virus. A major problem with state-of-the-art UV inactivation technology is that it is based on UV lamps, which have limited efficiency, require high power, large doses, and long irradiation times. These drawbacks limit the use of UV lamps in air filtering systems and other applications. To address these limitations, herein we report on the fabrication of a device comprising a pulsed nanosecond 266 nm UV laser coupled to an integrating cavity (LIC) composed of a UV reflective material, polytetrafluoroethylene. Previous UV lamp inactivation cavities were based on polished walls with specular reflections, but the diffuse reflective UV ICs were not thoroughly explored for virus inactivation. Our results show that LIC device can inactivate several respiratory viruses including SARS-CoV-2, at ~ 1 ms effective irradiation time, with > 2 orders of magnitude higher efficiency compared to UV lamps. The demonstrated 3 orders of magnitude cavity enhancement relative to direct exposure is crucial for the development of efficient real-time UV air and water purification systems. To the best of our knowledge this is the first demonstration of LIC application for broad viral inactivation with high efficiency.

Antioxidants in single methylene-blue-treated plasma units cannot be used to predict pathogen inactivation treatment success

BACKGROUND AND OBJECTIVES

Measurement of antioxidant power (AOP) can be useful to validate the execution of the pathogen inactivation (PI) treatment of plasma units. The aim of this study was to evaluate the Theraflex technology for plasma units routinely used in Belgium.

MATERIALS AND METHODS

AOP was tested on plasma units treated by Theraflex with various non-complete treatment scenarios. AOP was quantified electrochemically using disposable devices and was expressed as equivalent ascorbic acid concentration.

RESULTS

During a complete PI treatment, AOP rose from 195 ± 32 to 230 ± 42 μmol/L eq. ascorbic acid after addition of methylene blue (MB), and decreased to 192 ± 30 μmol/L eq. ascorbic acid after illumination and finally to 177 ± 27 μmol/L eq. ascorbic acid after final filtration. Without MB, the final filtration had no effect on the plasma AOP (197 ± 22 μmol/L eq. ascorbic acid before filtration and 194 ± 22 μmol/L eq. ascorbic acid after filtration). With no MB and no illumination, there was no significant difference between the plasma AOP at the beginning (188 ± 23 μmol/L eq. ascorbic acid) and at the end of the process (179 ± 21 μmol/L eq. ascorbic acid).

CONCLUSION

AOP measurement may not indicate the effectiveness of the PI treatment.

In Vitro Comparative Study of Platelets Treated with Two Pathogen-Inactivation Methods to Extend Shelf Life to 7 Days

Background and Objectives: Since 2015, platelet products have been pathogen-inactivated (PI) at the Luxemburgish Red Cross (LRC) using Riboflavin and UV light (RF-PI). As the LRC should respond to hospital needs at any time, platelet production exceeds the demand, generating a discard rate of 18%. To reduce this, we consider the extension of storage time from 5 to 7 days. This study’s objective was to evaluate the in vitro 7-day platelet-storage quality, comparing two PI technologies, RF-PI and amotosalen/UVA light (AM-PI), for platelet pools from whole-blood donations (PPCs) and apheresis platelets collected from single apheresis donation (APCs). Materials and Methods: For each product type, 6 double-platelet concentrates were prepared and divided into 2 units; one was treated with RF-PI and the other by AM-PI. In vitro platelet-quality parameters were tested pre- and post-PI, at days 5 and 7. Results: Treatment and storage lesions were observed in PPCs and APCs with both PI methods. We found a higher rate of lactate increase and glucose depletion, suggesting a stronger stimulation of the glycolytic pathway, a higher Annexin V binding, and a loss of swirling in the RF-PI-treated units from day 5. The platelet loss was significantly higher in the AM-PI compared with the RF-PI units. Conclusions: Results suggest that RF-PI treatment has a higher deleterious impact on in vitro platelet quality compared to AM-PI, but we observed higher loss of platelets with AM-PI due to the post-illumination amotosalen adsorption step. If 7-day storage is needed, it can only be achieved with AM-PI, based on our quality criteria.

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.

Human Platelet Lysate for Good Manufacturing Practice-Compliant Cell Production

Numerous cell-based therapeutics are currently being tested in clinical trials. Human platelet lysate (HPL) is a valuable alternative to fetal bovine serum as a cell culture medium supplement for a variety of different cell types. HPL as a raw material permits animal serum-free cell propagation with highly efficient stimulation of cell proliferation, enabling humanized manufacturing of cell therapeutics within a reasonable timeframe. Providers of HPL have to consider dedicated quality issues regarding identity, purity, potency, traceability and safety. Release criteria have to be defined, characterizing the suitability of HPL batches for the support of a specific cell culture. Fresh or expired platelet concentrates from healthy blood donors are the starting material for HPL preparation, according to regulatory requirements. Pooling of individual platelet lysate units into one HPL batch can balance donor variation with regard to essential platelet-derived growth factors and cytokines. The increasingly applied pathogen reduction technologies will further increase HPL safety. In this review article, aspects and regulatory requirements of whole blood donation and details of human platelet lysate manufacturing are presented. International guidelines for raw materials are discussed, and defined quality controls, as well as release criteria for safe and GMP-compliant HPL production, are summarized.

Effects and Side Effects of Platelet Transfusion

Aside from their canonical role in hemostasis, it is increasingly recognized that platelets have inflammatory functions and can regulate both adaptive and innate immune responses. The main topic this review aims to cover is the proinflammatory effects and side effects of platelet transfusion. Platelets prepared for transfusion are subject to stress injury upon collection, preparation, and storage. With these types of stress, they undergo morphologic, metabolic, and functional modulations which are likely to induce platelet activation and the release of biological response modifiers (BRMs). As a consequence, platelet concentrates (PCs) accumulate BRMs during processing and storage, and these BRMs are ultimately transfused alongside platelets. It has been shown that BRMs present in PCs can induce immune responses and posttransfusion reactions in the transfusion recipient. Several recent reports within the transfusion literature have investigated the concept of platelets as immune cells. Nevertheless, current and future investigations will face the challenge of encompassing the immunological role of platelets in the scope of transfusion.

Sulfenylome analysis of pathogen-inactivated platelets reveals the presence of cysteine oxidation in integrin signaling pathway and cytoskeleton regulation

Essentials Cysteine oxidation to sulfenic acid plays a key role in redox regulation and signal transduction. Platelet sulfenylome was studied by quantitative proteomics in pathogen inactivated platelets. One hundred and seventy-four sulfenylated proteins were identified in resting platelets. Pathogen inactivation oxidized integrin βIII, which could activate the mitogen-activated protein kinases pathway. ABSTRACT: Background Cysteine-containing protein modifications are involved in numerous biological processes such redox regulation or signal transduction. During the preparation and storage of platelet concentrates, cell functions and protein regulations are impacted. In spite of several proteomic investigations, the platelet sulfenylome, ie, the proteins containing cysteine residues (R-SH) oxidized to sulfenic acid (R-SOH), has not been characterized. Methods A dimedone-based sulfenic acid tagging and enrichment coupled to a mass spectrometry identification workflow was developed to identify and quantify the sulfenic acid-containing proteins in platelet concentrates treated or not with an amotosalen/ultraviolet A (UVA) pathogen inactivation technique. Results One hundred and seventy-four sulfenylated proteins were identified belonging mainly to the integrin signal pathway and cytoskeletal regulation by Rho GTPase. The impact on pathogen inactivated platelet concentrates was weak compared to untreated ones where three sulfenylated proteins (myosin heavy chain 9, integrin βIII, and transgelin 2) were significantly affected by amotosalen/UVA treatment. Of particular interest, the reported oxidation of cysteine residues in integrin βIII is known to activate the receptor αIIbβIII. Following the pathogen inactivation, it might trigger the phosphorylation of p38MAPK and explain the lesions reported in the literature. Moreover, procaspase activating compound-1 (PAC-1) binding assays on platelet activation showed an increased response to adenosine diphosphate exacerbated by the tagging of proteins with dimedone. This result corroborates the hypothesis of an oxidation-triggered activation of αIIbβIII by the pathogen inactivation treatment. Conclusions The present work completes missing information on the platelet proteome and provides new insights on the effect of pathogen inactivation linked to integrin signaling and cytoskeleton regulation.

Pathogen-reduced PRP blocks T-cell activation, induces Treg cells, and promotes TGF-β expression by cDCs and monocytes in mice

Alloimmunization against platelet-rich plasma (PRP) transfusions can lead to complications such as platelet refractoriness or rejection of subsequent transfusions and transplants. In mice, pathogen reduction treatment of PRP with UVB light and riboflavin (UV+R) prevents alloimmunization and appears to induce partial antigen-specific tolerance to subsequent transfusions. Herein, the in vivo responses of antigen-presenting cells and T cells to transfusion with UV+R-treated allogeneic PRP were evaluated to understand the cellular immune responses leading to antigen-specific tolerance. Mice that received UV+R-treated PRP had significantly increased transforming growth factor β (TGF-β) expression by CD11b+ CD4+ CD11cHi conventional dendritic cells (cDCs) and CD11bHi monocytes (P < .05). While robust T-cell responses to transfusions with untreated allogeneic PRP were observed (P < .05), these were blocked by UV+R treatment. Mice given UV+R-treated PRP followed by untreated PRP showed an early significant (P < .01) enrichment in regulatory T (Treg) cells and associated TGF-β production as well as diminished effector T-cell responses. Adoptive transfer of T-cell-enriched splenocytes from mice given UV+R-treated PRP into naive recipients led to a small but significant reduction of CD8+ T-cell responses to subsequent allogeneic transfusion. These data demonstrate that pathogen reduction with UV+R induces a tolerogenic profile by way of CD11b+ CD4+ cDCs, monocytes, and induction of Treg cells, blocking T-cell activation and reducing secondary T-cell responses to untreated platelets in vivo.

What about Platelet Function in Platelet Concentrates?

The characterization of platelet concentrates (PCs) in transfusion medicine has been performed with different analytical methods and platelet lesions (from biochemistry to cell biology) have been documented. In routine quality assessment and validation of manufacturing processes of PCs for transfusion purposes, only basic parameters are monitored and the platelet functions are not included. However, PCs undergo several manipulations during the processing and the basic parameters do not provide sensitive analyses to properly picture out the impact of the blood component preparation and storage on platelets. To improve the transfusion supply chain and the platelet functionalities, additional parameters should be used. The present short review will focus on the different techniques to monitor ex vivo platelet lesions from phenotype characterization to advanced omic analyses. Then, the opportunities to use these methods in quality control, process validation, development, and research will be discussed. Functional markers should be considered because they would be an advantage for the future developments in transfusion medicine.

Antioxidant power measurement in platelet concentrates treated by two pathogen inactivation systems in different blood centres

BACKGROUND AND OBJECTIVES

The antioxidant power measurement can be useful to validate the execution of the pathogen inactivation treatment of platelet concentrates. The aim of this study is to evaluate the technology on different blood preparations including INTERCEPT and Mirasol treatments that are in routine use in Belgium and Luxemburg.

MATERIALS AND METHODS

The antioxidant power measurement was tested on 78 apheresis platelet concentrates and 54 pools of buffy-coats-derived platelet concentrates before and after INTERCEPT treatment. In addition, 100 Reveos platelet pools were tested before and after Mirasol treatment. The antioxidant power was quantified electrochemically using disposable devices and was expressed as equivalent ascorbic acid concentration.

RESULTS

Mean results for apheresis platelet concentrates were of 90 ± 14 and 35 ± 10 µmol/l eq. ascorbic acid before and after INTERCEPT treatment, respectively. The mean results for pools of buffy-coats-derived platelet concentrates were of 81 ± 10 and 29 ± 4 eq. µmol/l ascorbic acid before and after INTERCEPT treatment, respectively. For buffy-coats-derived platelet concentrates treated by Mirasol technology, the mean results were of 98 ± 11 and 32 ± 10 µmol/l eq. ascorbic acid before and after illumination, respectively.

CONCLUSION

The antioxidant power significantly decreases with pathogen inactivation treatments for platelet concentrates treated by INTERCEPT or Mirasol technologies.

Quantum Leap from Gold and Silver to Aluminum Nanoplasmonics for Enhanced Biomedical Applications

Nanotechnology has been used in many biosensing and medical applications, in the form of noble metal (gold and silver) nanoparticles and nanostructured substrates. However, the translational clinical and industrial applications still need improvements of the efficiency, selectivity, cost, toxicity, reproducibility, and morphological control at the nanoscale level. In this review, we highlight the recent progress that has been made in the replacement of expensive gold and silver metals with the less expensive aluminum. In addition to low cost, other advantages of the aluminum plasmonic nanostructures include a broad spectral range from deep UV to near IR, providing additional signal enhancement and treatment mechanisms. New synergistic treatments of bacterial infections, cancer, and coronaviruses are envisioned. Coupling with gain media and quantum optical effects improve the performance of the aluminum nanostructures beyond gold and silver.

New strategies for the control of infectious and parasitic diseases in blood donors: the impact of pathogen inactivation methods

Around 70 infectious agents are possible threats for blood safety.

The risk for blood recipients is increasing because of new emergent agents like West Nile, Zika and Chikungunya viruses, or parasites such as Plasmodium and Trypanosoma cruzi in non-endemic regions, for instance.

Screening programmes of the donors are more and more implemented in several Countries, but these cannot prevent completely infections, especially when they are caused by new agents.

Pathogen inactivation (PI) methods might overcome the limits of the screening and different technologies have been set up in the last years.

This review aims to describe the most widely used methods focusing on their efficacy as well as on the preservation integrity of blood components.

Effects of amotosalen treatment on human platelet lysate bioactivity: A proof-of-concept study

BACKGROUND

Clinical application of mesenchymal stromal cells (MSCs) usually requires an in vitro expansion step to reach clinically relevant numbers. In vitro cell expansion necessitates supplementation of basal mammalian cell culture medium with growth factors. To avoid using supplements containing animal substances, human platelet lysates (hPL) produced from expired and pathogen inactivated platelet concentrates can be used in place of fetal bovine serum. However, globally, most transfusion units are currently not pathogen inactivated. As blood banks are the sole source of platelet concentrates for hPL production, it is important to ensure product safety and standardized production methods. In this proof-of-concept study we assessed the feasibility of producing hPL from expired platelet concentrates with pathogen inactivation applied after platelet lysis by evaluating the retention of growth factors, cytokines, and the ability to support MSC proliferation and tri-lineage differentiation.

METHODOLOGY/PRINCIPAL FINDINGS

Bone marrow-derived MSCs (BM-MSCs) were expanded and differentiated using hPL derived from pathogen inactivated platelet lysates (hPL-PIPL), with pathogen inactivation by amotosalen/ultraviolet A treatment applied after lysis of expired platelets. Results were compared to those using hPL produced from conventional expired pathogen inactivated platelet concentrates (hPL-PIPC), with pathogen inactivation applied after blood donation. hPL-PIPL treatment had lower concentrations of soluble growth factors and cytokines than hPL-PIPC treatment. When used as supplementation in cell culture, BM-MSCs proliferated at a reduced rate, but more consistently, in hPL-PIPL than in hPL-PIPC. The ability to support tri-lineage differentiation was comparable between lysates.

CONCLUSION/SIGNIFICANCE

These results suggest that functional hPL can be produced from expired and untreated platelet lysates by applying pathogen inactivation after platelet lysis. When carried out post-expiration, pathogen inactivation may provide a valuable solution for further standardizing global hPL production methods, increasing the pool of starting material, and meeting future demand for animal-free supplements in human cell culturing.

Platelets treated with pathogen reduction technology: current status and future direction

Allogeneic platelets collected for transfusion treated with pathogen reduction technology (PRT), which has been available in some countries for more than a decade, are now increasingly available in the United States (US). The implementation of PRT-treated platelets, also known as pathogen-reduced platelets (PRPs), has been spurred by the need to further decrease the risk of sepsis associated with bacterial contamination coupled with the potential of this technology to reduce the risk of infections due to already recognized, new, and emerging infectious agents. This article will review available PRP products, examine their benefits, highlight unresolved questions surrounding this technology, and summarize pivotal research studies that have compared transfusion outcomes (largely in adult patients) for PRPs with non-PRT-treated conventional platelets (CPs). In addition, studies describing the use of PRPs in pediatric patients and work done on the association between PRPs and HLA alloimmunization are discussed. As new data emerge, it is critical to re-evaluate the risks and benefits of existing PRPs and newer technologies and reassess the financial implications of adopting PRPs to guide our decision-making process for the implementation of transfusing PRPs.

The impact of bilirubin ditaurate on platelet quality during storage

Bilirubin ditaurate (BRT), a conjugated bilirubin analogue, has demonstrated anti-platelet characteristics following acute ex vivo exposure. Scavenging of mitochondrial superoxide and attenuation of granule exocytosis suggested a potential benefit for including BRT for storage. With no reports of cytotoxicity following acute exposure, the impact of 35µM BRT on platelet function was investigated, in clinically suppled units, for up to seven days. Exposure to 35µM BRT significantly reduced mitochondrial membrane potential and increased glucose consumption until exhaustion after 72 hours. Platelet aggregation and activation was significantly impaired by BRT. Mitochondrial superoxide production and phosphatidylserine expression were significantly elevated following glucose exhaustion, with decreased viability observed from day five onwards. Lactate accumulation and loss of bicarbonate, support a metabolic disturbance, leading to a decline of quality following BRT inclusion. Although acute ex vivo BRT exposure reported potentially beneficial effects, translation from acute to chronic exposure failed to combat declining platelet function during storage. BRT exposure resulted in perturbations of platelet quality, with the utility of BRT during storage therefore limited. However, these are the first data of prolonged platelet exposure to analogues of conjugated bilirubin and may improve our understanding of platelet function in the context of conjugated hyperbilirubinemia.

Pathogen reduction with riboflavin and ultraviolet light induces a quasi-apoptotic state in blood leukocytes

BACKGROUND

Alloimmunization to platelet-rich plasma (PRP) transfusions can cause adverse reactions such as platelet refractoriness or transplant rejection. Pathogen reduction treatment with ultraviolet light and riboflavin (UV + R) of allogeneic PRP was shown to reduce allogeneic antibody responses and confer partial antigen-specific immune tolerance to subsequent transfusions in mice. Studies have shown that UV + R was effective at both rapidly killing donor white blood cells (WBCs) and reducing their ability to stimulate an allogeneic response in vitro. However, the manner in which UV + R induces WBC death and its associated role in the immune response to treated PRP is unknown.

METHODS AND MATERIALS

This study evaluates whether UV + R causes WBC apoptosis by examining phosphatidylserine exposure on the plasma membrane, membrane asymmetry, caspase activity, and chromatin condensation by flow cytometry. The immunogenicity of WBCs killed with UV + R versus apoptotic or necrotic pathways was also examined in vivo.

RESULTS

WBCs after UV + R exhibited early apoptotic-like characteristics including phosphatidylserine exposure on the outer leaflet of the plasma membrane and loss of membrane asymmetry, but unlike canonical apoptotic cells, caspase activity and chromatin condensation were not apparent. However, in vivo studies demonstrated, unlike untreated or necrotic WBCs, both apoptotic WBCs and UV + R-treated WBCs failed to prime alloantibody responses to subsequent untreated transfusions.

CONCLUSION

Overall, the mechanism of WBC death following UV + R treatment shares some membrane characteristics of early apoptosis but is distinct from classic apoptosis. Despite these differences, UV + R-treated and apoptotic WBCs both offer some protection from alloimmunization.

Towards the understanding of the UV light, riboflavin and additive solution contributions to the in vitro lesions observed in Mirasol®-treated platelets

OBJECTIVES

Pathogen reduction technologies are implemented to increase the safety of blood products. We previously showed that the UVB alone significantly contributes to the storage lesions observed in platelets treated with riboflavin/UVB using a home-made illuminator. The present study aims at confirming these observations using the commercial Mirasol® technology.

METHODS

A three-arm study (untreated, UV-, Mirasol®-treated platelets) was conducted to investigate the platelet storage lesions throughout storage (n=4). A two-arm study was then designed to compare Intersol and T-PAS+ additive solutions (n=3). Phenotype and functional platelet characteristics were assessed using flow cytometry, aggregometry, antioxidant assays and metabolic parameters.

RESULTS

Mirasol®-treated platelets exhibit enhanced storage lesions compared to controls (increase of activation markers and glycolysis rate, lower hypotonic shock and double-agonist activation responses, and decrease of total antioxidant capacity). Here, we also confirmed that the UV radiation alone is causing platelet lesions. Riboflavin tends to have an intracellular protective role while it decreases the extracellular antioxidant defenses. Furthermore, benefits of platelet additive solutions containing potassium and magnesium were confirmed as it reduces the extent of storage lesions.

CONCLUSIONS

The photosensitizer, UV illumination and composition of the platelet additive solutions are key parameters influencing the platelet storage lesion. The clinical relevance of these findings is not fully understood and recent published clinical studies could not show increase in bleeding in patients receiving Mirasol-treated platelets. New developments in storage solutions might help to improve storage conditions of PRT-treated platelets and should be prioritised as research subject in the future.

Blood Utilization and Transfusion Reactions in Pediatric Patients Transfused with Conventional or Pathogen Reduced Platelets

OBJECTIVES

To assess the safety and efficacy of a Food and Drug Administration-approved pathogen-reduced platelet (PLT) product in children, as ongoing questions regarding their use in this population remain.

STUDY DESIGN

We report findings from a quality assurance review of PLT utilization, associated red blood cell transfusion trends, and short-term safety of conventional vs pathogen-reduced PLTs over a 21-month period while transitioning from conventional to pathogen-reduced PLTs at a large, tertiary care hospital. We assessed utilization in neonatal intensive care unit (NICU) patients, infants 0-1 year not in the NICU, and children age 1-18 years (PED).

RESULTS

In the 48 hours after an index conventional or pathogen-reduced platelet transfusion, respectively, NICU patients received 1.0 ± 1.4 (n = 91 transfusions) compared with 1.2 ± 1.3 (n = 145) additional platelet doses (P = .29); infants 0-1 year not in the NICU received 2.8 ± 3.0 (n = 125) vs 2.6 ± 2.6 (n = 254) additional platelet doses (P = .57); and PEDs received 0.9 ± 1.6 (n = 644) vs 1.4 ± 2.2 (n = 673) additional doses (P < .001). Time to subsequent transfusion and red cell utilization were similar in every group (P > .05). The number and type of transfusion reactions did not significantly vary based on PLT type and no rashes were reported in NICU patients receiving phototherapy and pathogen-reduced PLTs.

CONCLUSIONS

Conventional and pathogen-reduced PLTs had similar utilization patterns in our pediatric populations. A small, but statistically significant, increase in transfusions was noted following pathogen-reduced PLT transfusion in PED patients, but not in other groups. Red cell utilization and transfusion reactions were similar for both products in all age groups.

A double-virally-inactivated (Intercept-solvent/detergent) human platelet lysate for in vitro expansion of human mesenchymal stromal cells

BACKGROUND

Pooled human platelet lysate (HPL) can replace fetal bovine serum (FBS) as xeno-free supplement for ex vivo expansion of mesenchymal stromal cells (MSCs). We evaluate here whether a double-virally-inactivated HPL (DVI-HPL) prepared from expired Intercept-treated platelet concentrates (PCs) and treated by solvent/detergent (S/D) can be used for MSC expansion.

STUDY DESIGN AND METHODS

Expired Intercept-treated PCs in 65% platelet (PLT) additive solution were pooled and subjected to a 1% tri-n-butyl phosphate/1% Triton X-45 treatment followed by soybean oil, hydrophobic interaction chromatography purification, and sterile filtration. Bone marrow-derived MSCs (BM-MSCs) were expanded for four passages in growth medium containing 10% DVI-HPL, I-HPL (from Intercept-PC only), untreated HPL, and FBS. MSC morphology, doubling time, immunophenotype, immunosuppressive activity, and differentiation capacity were compared.

RESULTS

Expanded cells had typical spindle morphology and showed higher viability in all HPL conditions than in FBS. The DVI-HPL and FBS-expanded cells were morphologically larger than in I-HPL and HPL supplements. The cumulative population doubling was lower using DVI-HPL than with HPL and I-HPL, but significantly higher than using FBS. Immunophenotype was not affected by the supplements used. Immunosuppressive activity was maintained with all supplements. Differentiation capacity into chondrocytes and osteocytes was more effective in DVI-HPL but less toward adipocytes compared to other supplements.

CONCLUSIONS

Human PLT lysate made from Intercept-PCs subjected to S/D treatment may be an alternative to untreated HPL and to I-HPL for BM-MSC expansion. This finding reinforces the potential of HPL as a virally safe alternative to FBS for clinical grade MSC expansion protocols.

Irreversible oxidations of platelet proteins after riboflavin-UVB pathogen inactivation

Pathogen inactivation technologies are known to alter in vitro phenotype and functional properties of platelets. Because pathogen inactivation generates reactive oxygen species, oxidative stress is considered as one of the plausible cause at the origin of the platelet storage lesion acceleration after treatment. To date proteomics has been used to document the protein variations to picture out the impact. Here, platelet concentrates were prepared from buffy-coats in Intersol additive solution, leukoreduced and pathogen inactivated using a riboflavin/UVB treatment. At day 2 of storage the platelet proteomes of control (untreated) and treated platelet concentrates were investigated against the site specific oxidation by liquid chromatography coupled to tandem mass spectrometry in a shotgun experiment. The shotgun approach detected 9350 peptides (and 2534 proteins) of which 1714 were oxidized. Eighteen peptides were found exclusively oxidized in treated platelets whereas 3 peptides were only found oxidized in control. The present data evidenced an interference with several proteins involved in platelet aggregation and platelet shape change (such as talin and vinculin).

General overview of blood products in vitro quality: Processing and storage lesions

Blood products are issued from blood collection. Collected blood is immediately mixed with anticoagulant solutions that immediately induce chemical and/or biochemical modifications. Collected blood is then transformed into different blood products according to various steps of fabrication. All these steps induce either reversible or irreversible "preparation-related" lesions that combine with "storage-related" lesions. This short paper aims to provide an overview of the alterations that are induced by the "non-physiological" processes used to prepare blood products that are used in clinical practice.