Distinct SARS-CoV-2 antibody reactivity patterns in coronavirus convalescent plasma revealed by a coronavirus antigen microarray

A coronavirus antigen microarray (COVAM) was constructed containing 11 SARS-CoV-2, 5 SARS-1, 5 MERS, and 12 seasonal coronavirus recombinant proteins. The array is designed to measure immunoglobulin isotype and subtype levels in serum or plasma samples against each of the individual antigens printed on the array. We probed the COVAM with COVID-19 convalescent plasma (CCP) collected from 99 donors who recovered from a PCR+ confirmed SARS-CoV-2 infection. The results were analyzed using two computational approaches, a generalized linear model (glm) and random forest (RF) prediction model, to classify individual specimens as either Reactive or non-reactive against the SARS-CoV-2 antigens. A training set of 88 pre-COVID-19 specimens (PreCoV) collected in August 2019 and102 positive specimens from SARS-CoV-2 PCR+ confirmed COVID-19 cases was used for these analyses. Results compared with an FDA emergency use authorized (EUA) SARS-CoV2 S1-based total Ig chemiluminescence immunoassay (Ortho Clinical Diagnostics VITROS Anti-SARS-CoV-2 Total, CoV2T) and with a SARS-CoV-2 S1-S2 spike-based pseudovirus micro neutralization assay (SARS-CoV-2 reporter viral particle neutralization titration (RVPNT) showed high concordance between the three assays. Three CCP specimens that were negative by the VITROS CoV2T immunoassay were also negative by both COVAM and the RVPNT assay. Concordance between VITROS CoV2T and COVAM was 96%, VITROS CoV2T and RVPNT 93%, and RVPNT and COVAM 91%. The discordances were all weakly reactive samples near the cutoff threshold of the VITROS CoV2T immunoassay. The multiplex COVAM allows CCP to be grouped according to antibody reactivity patterns against 11 SARS-CoV-2 antigens. Unsupervised K-means analysis, via the gap statistics, as well as hierarchical clustering analysis revealed three main clusters with distinct reactivity intensities and patterns. These patterns were not recapitulated by adjusting the VITROS CoV2T or RVPNT assay thresholds. Plasma classified by COVAM reactivity patterns offers potential to improve CCP therapeutic efficacy CoV2T alone. The use of a SARS-CoV-2 antigen array can qualify CCP for administration as a treatment for acute COVID-19, and interrogate vaccine immunogenicity and performance in preclinical, clinical studies, and routine vaccination to identify antibody responses predictive of protection from infection and disease.

Selecting COVID-19 convalescent plasma for neutralizing antibody potency using a high-capacity SARS-CoV-2 antibody assay

BACKGROUND

Efficacy of COVID-19 convalescent plasma (CCP) is hypothesized to be associated with the concentration of neutralizing antibodies (nAb) to SARS-CoV-2. High capacity serologic assays detecting binding antibodies (bAb) have been developed; nAb assays are not adaptable to high-throughput testing. We sought to determine the effectiveness of using surrogate bAb signal-to-cutoff ratios (S/Co) in predicting nAb titers using a pseudovirus reporter viral particle neutralization (RVPN) assay.

METHODS

CCP donor serum collected by three US blood collectors was tested with a bAb assay (Ortho Clinical Diagnostics VITROS Anti-SARS-CoV-2 Total, CoV2T) and a nAb RVPN assay. Prediction effectiveness of various CoV2T S/Co criteria was evaluated for RVPN nAb NT50 titers using receiver operating characteristics.

RESULTS

Seven hundred and fifty-three CCPs were tested with median CoV2T S/Co and NT50 of 71.2 of 527.5. Proportions of donors with NT50 over target nAb titers were 86% ≥1:80, 76% ≥1:160, and 62% ≥1:320. Increasing CoV2T S/Co criterion reduced the sensitivity to predict NT50 titers, while specificity to identify those below increased. As target NT50 titers increase, the CoV2T assay becomes less accurate as a predictor with a decline in positive predictive value and rise in negative predictive value.

CONCLUSION

Selection of a clinically effective nAb titer will impact availability of CCP. Product release with CoV2T assay S/Co criterion must balance the risk of releasing products below target nAb titers with the cost of false negatives. A two-step testing scheme may be optimal, with nAb testing on CoV2T samples with S/Cos below criterion.

Longitudinal single-cell epitope and RNA-sequencing reveals the immunological impact of type 1 interferon autoantibodies in critical COVID-19: Anti-IFN antibodies in critical COVID-19 correlate with poor ISG response and upregulation of LAIR1 surface protein in PBMCs

Type I interferon (IFN-I) neutralizing autoantibodies have been found in some critical COVID-19 patients; however, their prevalence and longitudinal dynamics across the disease severity scale, and functional effects on circulating leukocytes remain unknown. Here, in 284 COVID-19 patients, we found IFN-I autoantibodies in 19% of critical, 6% of severe and none of the moderate cases. Longitudinal profiling of over 600,000 peripheral blood mononuclear cells using multiplexed single-cell epitope and transcriptome sequencing from 54 COVID-19 patients, 15 non-COVID-19 patients and 11 non-hospitalized healthy controls, revealed a lack of IFN-I stimulated gene (ISG-I) response in myeloid cells from critical cases, including those producing anti-IFN-I autoantibodies. Moreover, surface protein analysis showed an inverse correlation of the inhibitory receptor LAIR-1 with ISG-I expression response early in the disease course. This aberrant ISG-I response in critical patients with and without IFN-I autoantibodies, supports a unifying model for disease pathogenesis involving ISG-I suppression via convergent mechanisms.

Blood donor exposome and impact of common drugs on red blood cell metabolism

Computational models based on recent maps of the RBC proteome suggest that mature erythrocytes may harbor targets for common drugs. This prediction is relevant to RBC storage in the blood bank, in which the impact of small molecule drugs or other xenometabolites deriving from dietary, iatrogenic, or environmental exposures (“exposome”) may alter erythrocyte energy and redox metabolism and, in so doing, affect red cell storage quality and posttransfusion efficacy. To test this prediction, here we provide a comprehensive characterization of the blood donor exposome, including the detection of common prescription and over-the-counter drugs in blood units donated by 250 healthy volunteers in the Recipient Epidemiology and Donor Evaluation Study III Red Blood Cell–Omics (REDS-III RBC-Omics) Study. Based on high-throughput drug screenings of 1366 FDA-approved drugs, we report that approximately 65% of the tested drugs had an impact on erythrocyte metabolism. Machine learning models built using metabolites as predictors were able to accurately predict drugs for several drug classes/targets (bisphosphonates, anticholinergics, calcium channel blockers, adrenergics, proton pump inhibitors, antimetabolites, selective serotonin reuptake inhibitors, and mTOR), suggesting that these drugs have a direct, conserved, and substantial impact on erythrocyte metabolism. As a proof of principle, here we show that the antacid ranitidine — though rarely detected in the blood donor population — has a strong effect on RBC markers of storage quality in vitro. We thus show that supplementation of blood units stored in bags with ranitidine could — through mechanisms involving sphingosine 1–phosphate–dependent modulation of erythrocyte glycolysis and/or direct binding to hemoglobin — improve erythrocyte metabolism and storage quality.

Guidance for the procurement of COVID-19 convalescent plasma: differences between high- and low-middle-income countries

Background and objectives

COVID‐19 convalescent plasma (CCP) has been used, predominantly in high‐income countries (HICs) to treat COVID‐19; available data suggest the safety and efficacy of use. We sought to develop guidance for procurement and use of CCP, particularly in low‐ and middle‐income countries (LMICs) for which data are lacking.

Materials and methods

A multidisciplinary, geographically representative group of individuals with expertise spanning transfusion medicine, infectious diseases and haematology was tasked with the development of a guidance document for CCP, drawing on expert opinion, survey of group members and review of available evidence. Three subgroups (i.e. donor, product and patient) were established based on self‐identified expertise and interest. Here, the donor and product‐related challenges are summarized and contrasted between HICs and LMICs with a view to guide related practices.

Results

The challenges to advance CCP therapy are different between HICs and LMICs. Early challenges in HICs related to recruitment and qualification of sufficient donors to meet the growing demand. Antibody testing also posed a specific obstacle given lack of standardization, variable performance of the assays in use and uncertain interpretation of results. In LMICs, an extant transfusion deficit, suboptimal models of donor recruitment (e.g. reliance on replacement and paid donors), limited laboratory capacity for pre‐donation qualification and operational considerations could impede wide adoption.

Conclusion

There has been wide‐scale adoption of CCP in many HICs, which could increase if clinical trials show efficacy of use. By contrast, LMICs, having received little attention, require locally applicable strategies for adoption of CCP.

Retrospective cohort studies of repeat donors reveal donor-dependent variability in the recovery of transfused platelets

BACKGROUND

The in vivo recovery of transfused platelets is variable and often unpredictable. Although many recipient-dependent factors are well described, donor-dependent variables remain poorly understood.

STUDY DESIGN AND METHODS

To explore donor-dependent variables we conducted 2 retrospective studies of platelet transfusion outcomes in repeat donors. One study analyzed multiple autologous, radiolabeled platelet transfusions, and a second study analyzed multiple clinical platelet transfusions from a small cohort of repeat donors.

RESULTS

In 36 subjects, multiple within-subject determinations of recovery and survival of radiolabeled autologous platelets revealed a relative consistency in platelet recoveries within donors compared to the range of recoveries among donors. Intraclass correlation coefficients for platelet recovery were 43% to 93%. In 524 ABO-compatible clinical platelet transfusions derived from seven donors, a linear mixed-effects model revealed significant donor-dependent differences in corrected count increments for units stored for 4 or 5 days.

CONCLUSIONS

These two studies indicate reproducible donor-dependent differences in transfused platelet recovery, suggesting a possible heritable influence on the quality of transfused platelets.

Impact of taurine on red blood cell metabolism and implications for blood storage

BACKGROUND

Taurine is an antioxidant that is abundant in some common energy drinks. Here we hypothesized that the antioxidant activity of taurine in red blood cells (RBCs) could be leveraged to counteract storage-induced oxidant stress.

STUDY DESIGN AND METHODS

Metabolomics analyses were performed on plasma and RBCs from healthy volunteers (n = 4) at baseline and after consumption of a whole can of a common, taurine-rich (1000 mg/serving) energy drink. Reductionistic studies were also performed by incubating human RBCs with taurine ex vivo (unlabeled or ¹³ C¹⁵ N-labeled) at increasing doses (0, 100, 500, and 1000 μmol/L) at 37°C for up to 16 hours, with and without oxidant stress challenge with hydrogen peroxide (0.1% or 0.5%). Finally, we stored human and murine RBCs under blood bank conditions in additives supplemented with 500 μmol/L taurine, before metabolomics and posttransfusion recovery studies.

RESULTS

Consumption of energy drinks increased plasma and RBC levels of taurine, which was paralleled by increases in glycolysis and glutathione (GSH) metabolism in the RBC. These observations were recapitulated ex vivo after incubation with taurine and hydrogen peroxide. Taurine levels in the RBCs from the REDS-III RBC-Omics donor biobank were directly proportional to the total levels of GSH and glutathionylated metabolites and inversely correlated to oxidative hemolysis measurements. Storage of human RBCs in the presence of taurine improved energy and redox markers of storage quality and increased posttransfusion recoveries in FVB mice.

CONCLUSION

Taurine modulates RBC antioxidant metabolism in vivo and ex vivo, an observation of potential relevance to transfusion medicine.

Methylation of protein aspartates and deamidated asparagines as a function of blood bank storage and oxidative stress in human red blood cells

BACKGROUND

Being devoid of de novo protein synthesis capacity, red blood cells (RBCs) have evolved to recycle oxidatively damaged proteins via mechanisms that involve methylation of dehydrated and deamidated aspartate and asparagine residues. Here we hypothesize that such mechanisms are relevant to routine storage in the blood bank.

STUDY DESIGN AND METHODS

Within the framework of the REDS-III RBC-Omics (Recipient Epidemiology Donor Evaluation Study III Red Blood Cell-Omics) study, packed RBC units (n = 599) were stored under blood bank conditions for 10, 23, and 42 days and profiled for oxidative hemolysis and time-dependent metabolic dysregulation of the trans-sulfuration pathway.

RESULTS

In these units, methionine consumption positively correlated with storage age and oxidative hemolysis. Mechanistic studies show that this phenomenon is favored by oxidative stress or hyperoxic storage (sulfur dioxide >95%), and prevented by hypoxia or methyltransferase inhibition. Through a combination of proteomics approaches and ¹³ C-methionine tracing, we observed oxidation-induced increases in both Asn deamidation to Asp and formation of methyl-Asp on key structural proteins and enzymes, including Band 3, hemoglobin, ankyrin, 4.1, spectrin beta, aldolase, glyceraldehyde 3-phosphate dehydrogenase, biphosphoglycerate mutase, lactate dehydrogenase and catalase. Methylated regions tended to map proximal to the active site (e.g., N316 of glyceraldehyde 3-phosphate dehydrogenase) and/or residues interacting with the N-terminal cytosolic domain of Band 3.

CONCLUSION

While methylation of basic amino acid residues serves as an epigenetic modification in nucleated cells, protein methylation at carboxylate side chains and deamidated asparagines is a nonepigenetic posttranslational sensor of oxidative stress and refrigerated storage in anucleated human RBCs.

Comparison between manufacturing sites shows differential adhesion, activation, and GPIbα expression of cryopreserved platelets

BACKGROUND

Transfusion of cryopreserved platelets (cryoplatelets) is not common but may replace standard liquid-preserved platelets (PLTs) in specific circumstances. To better understand cryoplatelet function, frozen concentrates from different manufacturing sites were compared.

STUDY DESIGN AND METHODS

Cryoplatelets from Denver, Colorado (DEN); Sydney, Australia (SYD); and Ghent, Belgium (GHE) were compared (n = 6). A paired noncryopreserved control was included in Ghent. Microfluidic-flow chambers were used to study PLT adhesion and fibrin deposition in reconstituted blood. Receptor expression was measured by flow cytometry. Coagulation in static conditions was evaluated by rotational thromboelastometry (ROTEM).

RESULTS

Regardless of the manufacturing site, adhesion of cryoplatelets under shear flow (1000/sec) was significantly (p < 0.05) reduced compared to control. Expression of GPIbα was decreased in a subpopulation of cryoplatelets comprising 45% ± 11% (DEN), 63% ± 9% (GHE), and 94% ± 6% (SYD). That subpopulation displayed increased annexin V binding and decreased integrin activation. PLT adhesion, agglutination, and aggregation were moreover decreased in proportion to that subpopulation. Fibrin deposition under shear flow was normal but initiated faster (546 ± 163 sec GHE) than control PLTs (631 ± 120 sec, p < 0.01), only in the absence of tissue factor. In static conditions, clotting time was faster, but clot firmness decreased compared to control. Coagulation was not different between manufacturing sites.

CONCLUSION

Cryopreservation results in a subset of PLTs with enhanced GPIbα shedding, increased phosphatidylserine expression, reduced integrin response, and reduced adhesion to collagen in microfluidic models of hemostasis. The proportion of this phenotype is different between manufacturing sites. The clinical effects, if any, will need to be verified.

A Study of the Pharmacokinetic Properties and the In Vivo Kinetics of Erythrocytes Loaded With Dexamethasone Sodium Phosphate in Healthy Volunteers

The objectives of this 2-phase study were to elucidate pharmacokinetics (PK), in vivo 24-hour recovery, and red blood cell (RBC) survival properties of RBC-encapsulated dexamethasone sodium phosphate (DSP) prepared using the EryDex System (EDS). The 24-hour RBC recovery and T50 survival phase studied subjects were randomized to receive autologous RBCs loaded with either 15-20 mg DSP (Group 1A) or sham saline (Group 2A). Loaded RBCs were radiolabeled with 51-Cr, and the labeled RBCs were followed over time in vivo. The PK phase evaluated dose levels of 2.5-5 mg (Group 1B) and 15-20 mg (Group 2B) DSP encapsulated in RBCs infused into healthy randomized subjects. The mean ± SD 24-hour RBC recovery was 77.9% ± 3.3% and 72.7% ± 10.5% for Groups 1A and 2A, respectively. The mean ± SD RBC life span was 84.3 ± 8.3 days in Group 1A and 88.9 ± 6.2 days in Group 2A. The PK phase actual DSP loading doses (mean ± SEM) were 4.2 ± 0.27 mg and 16.9 ± 0.90 mg in Groups 1B and 2B, respectively. Release of dexamethasone from RBCs in vivo peaked at 1 hour, and a sustained release of dexamethasone could be detected until 35 days after the single intravenous infusion in Group 2B. The mean RBC in vivo recovery for DSP-loaded processed cells compares similarly to the 24-hour recovery of regulated RBC products intended for transfusion. There was a minimal but acceptable adverse impact on the survival of EDS-processed RBCs. DSP-loaded autologous RBCs, prepared using the EDS, delivered a sustained dose of dexamethasone in vivo.

Apheresis buffy coat collection without photoactivation has no effect on apoptosis, cell proliferation, and total viability of mononuclear cells collected using photopheresis systems

BACKGROUND

Extracorporeal photopheresis (ECP) has been approved for the treatment of advanced cutaneous T-cell lymphoma since 1988. While the precise mechanisms resulting in clinical effects are not fully understood, the photoactivation of mononuclear cells (MNCs) using ultraviolet A (UVA) light and methoxsalen is believed to be the predominant initiating process. The effects of MNC passage through the instrument without photoactivation are unknown. The objective of this study was to evaluate the effect of cell processing through the photopheresis instruments on MNCs.

STUDY DESIGN AND METHODS

Fourteen healthy male subjects underwent one simulated ECP procedure without reinfusion of buffy coats (BCs) in a two-center, open-label, prospective trial. Baseline peripheral blood BC, apheresis-separated untreated BC (BC1), and photoactivated BC (BC2) were evaluated in culture for viability by dye exclusion, apoptosis by annexin V binding, and cell proliferation response to phytohemagglutinin (PHA) stimulation by bromodeoxyuridine (BrdU) incorporation.

RESULTS

Photoactivation (BC2) resulted in 88% expression of annexin V by Day 1 of culture compared with 37 and 39% for baseline and untreated BC1. Cell viability by propidium iodide exclusion was reduced to 10% in BC2 on Day 1 versus 65 and 60% for baseline and BC1. The proliferative response to PHA stimulation was 97% inhibited in the photoactivated BC2.

CONCLUSIONS

These results demonstrate that the mechanical processes used for cell separation and processing of the BC in the absence of photoactivation do not induce a significant amount of apoptosis compared to the standard ECP with methoxsalen and UVA photoactivation.

Red blood cell metabolic responses to refrigerated storage, rejuvenation, and frozen storage

BACKGROUND

Storage of red blood cells (RBCs) under blood bank conditions promotes metabolic modulation within the RBC. This "metabolic storage lesion" may affect the quality and safety of the transfused RBCs. The aim of this study is to determine the metabolic changes in stored RBCs over 42 days of routine storage followed by a US Food and Drug Administration-approved method of rejuvenation, freezing, and preparation for transfusion.

STUDY DESIGN AND METHODS

We exploited a mass spectrometry-based metabolomics approach to monitor 42-day-stored citrate phosphate dextrose/AS-1 RBCs (n = 29) that were rejuvenated, glycerolized and frozen, then thawed and deglycerolized, and held for 24 hours at 1 to 6ºC in saline-glucose.

RESULTS

Previously reported metabolic alterations were confirmed in 42-day-old RBCs. In this study, in total, 181 (62%) of the biochemical compounds exhibited significant (p ≤ 0.05) change compared with Day 0 values. Rejuvenation restored adenosine triphosphate and 2,3-diphosphoglycerate levels, replenished purine reservoirs, up regulated glycolysis, increased levels of pentose phosphate pathway intermediates, and partially rescued glutathione biosynthesis. Increased levels of lysophospholipid in rejuvenated RBCs suggests the activation of recycling pathways of damaged membrane lipids, in which a total of 167 (57%) biochemical compounds showed significant change compared with Day 42 values.

CONCLUSION

Rejuvenation reversed over one-half of the metabolic biochemical compounds evaluated compared with Day 42 values, and the compounds were stable through frozen storage and preparation for transfusion. Rejuvenation promoted significant metabolic reprogramming, including the reactivation of energy-generating and antioxidant pathways (the pentose phosphate pathway and glutathione homeostasis), salvage reactions, cofactor reservoirs, and membrane lipid recycling.

International validation of a dithiothreitol (DTT)-based method to resolve the daratumumab interference with blood compatibility testing

BACKGROUND

Daratumumab (DARA) consistently interferes with routine blood bank serologic testing by directly binding to CD38 expressed on reagent red blood cells (RBCs). Treating RBCs with dithiothreitol (DTT) eliminates the DARA interference. We conducted an international, multicenter, blinded study aimed at validating the DTT method for use by blood bank laboratories worldwide.

STUDY DESIGN AND METHODS

Paired plasma sample unknowns were sent to 25 participating blood bank laboratories. Sample 1 was spiked with DARA only (10 µg/mL), and Sample 2 with DARA plus a clinically significant RBC antibody (anti-D [n = 6], anti-Fya [n = 9], or anti-s [n = 10]). Sites were instructed to perform an antibody screen with and without DTT-treated RBCs and to use a DTT-treated RBC panel for antibody identification. Qualitative data about the DTT method were collected by online survey. The primary outcome was the proportion of study sites able to identify the antibody unknown in the presence of DARA.

RESULTS

All sites observed the DARA interference with the antibody screen. The DARA interference was seen with all testing methods (gel, tube, or solid phase). Using the DTT method, 25 of 25 sites (100%) successfully identified the antibody unknown in the presence of DARA. Feedback on the DTT method was positive, with 17 of 19 (90%) sites responding to the survey indicating that they planned to use the DTT method to test clinical samples from DARA-treated patients.

CONCLUSION

The DTT method is robust and reproducible and can be implemented by transfusion services worldwide to help provide safe blood products to patients treated with DARA.

Metabolic pathways that correlate with post-transfusion circulation of stored murine red blood cells

Transfusion of red blood cells is a very common inpatient procedure, with more than 1 in 70 people in the USA receiving a red blood cell transfusion annually. However, stored red blood cells are a non-uniform product, based upon donor-to-donor variation in red blood cell storage biology. While thousands of biological parameters change in red blood cells over storage, it has remained unclear which changes correlate with function of the red blood cells, as opposed to being co-incidental changes. In the current report, a murine model of red blood cell storage/transfusion is applied across 13 genetically distinct mouse strains and combined with high resolution metabolomics to identify metabolic changes that correlated with red blood cell circulation post storage. Oxidation in general, and peroxidation of lipids in particular, emerged as changes that correlated with extreme statistical significance, including generation of dicarboxylic acids and monohydroxy fatty acids. In addition, differences in anti-oxidant pathways known to regulate oxidative stress on lipid membranes were identified. Finally, metabolites were identified that differed at the time the blood was harvested, and predict how the red blood cells perform after storage, allowing the potential to screen donors at time of collection. Together, these findings map out a new landscape in understanding metabolic changes during red blood cell storage as they relate to red blood cell circulation.

Metabolomics in transfusion medicine

Biochemical investigations on the regulatory mechanisms of red blood cell (RBC) and platelet (PLT) metabolism have fostered a century of advances in the field of transfusion medicine. Owing to these advances, storage of RBCs and PLT concentrates has become a lifesaving practice in clinical and military settings. There, however, remains room for improvement, especially with regard to the introduction of novel storage and/or rejuvenation solutions, alternative cell processing strategies (e.g., pathogen inactivation technologies), and quality testing (e.g., evaluation of novel containers with alternative plasticizers). Recent advancements in mass spectrometry-based metabolomics and systems biology, the bioinformatics integration of omics data, promise to speed up the design and testing of innovative storage strategies developed to improve the quality, safety, and effectiveness of blood products. Here we review the currently available metabolomics technologies and briefly describe the routine workflow for transfusion medicine-relevant studies. The goal is to provide transfusion medicine experts with adequate tools to navigate through the otherwise overwhelming amount of metabolomics data burgeoning in the field during the past few years. Descriptive metabolomics data have represented the first step omics researchers have taken into the field of transfusion medicine. However, to up the ante, clinical and omics experts will need to merge their expertise to investigate correlative and mechanistic relationships among metabolic variables and transfusion-relevant variables, such as 24-hour in vivo recovery for transfused RBCs. Integration with systems biology models will potentially allow for in silico prediction of metabolic phenotypes, thus streamlining the design and testing of alternative storage strategies and/or solutions.

CO2 -dependent metabolic modulation in red blood cells stored under anaerobic conditions

BACKGROUND

Anaerobic red blood cell (RBC) storage reduces oxidative damage, maintains adenosine triphosphate (ATP) and 2,3-diphosphoglycerate (DPG) levels, and has superior 24-hour recovery at 6 weeks compared to standard storage. This study will determine if removal of CO2 during O2 depletion by gas exchange may affect RBCs during anaerobic storage.

STUDY DESIGN AND METHODS

This is a matched three-arm study (n = 14): control, O2 and CO2 depleted with Ar (AN), and O2 depleted with 95%Ar/5%CO2 (AN[CO2 ]). RBCs in additives AS-3 or OFAS-3 were evenly divided into three bags, and anaerobic conditions were established by gas exchange. Bags were stored at 1 to 6°C in closed chambers under anaerobic conditions or ambient air, sampled weekly for up to 9 weeks for a panel of in vitro tests. A full metabolomics screening was conducted for the first 4 weeks of storage.

RESULTS

Purging with Ar (AN) results in alkalization of the RBC and increased glucose consumption. The addition of 5% CO2 to the purging gas prevented CO2 loss with an equivalent starting and final pH and lactate to control bags (p > 0.5, Days 0-21). ATP levels are higher in AN[CO2 ] (p < 0.0001). DPG was maintained beyond 2 weeks in the AN arm (p < 0.0001). Surprisingly, DPG was lost at the same rate in both control and AN[CO2 ] arms (p = 0.6).

CONCLUSION

Maintenance of ATP in the AN[CO2 ] arm demonstrates that ATP production is not solely a function of the pH effect on glycolysis. CO2 in anaerobic storage prevented the maintenance of DPG, and DPG production appears to be pH dependent. CO2 as well as O2 depletion provides metabolic advantage for stored RBCs.

Red blood cell storage in additive solution-7 preserves energy and redox metabolism: a metabolomics approach

BACKGROUND

Storage and transfusion of red blood cells (RBCs) has a huge medical and economic impact. Routine storage practices can be ameliorated through the implementation of novel additive solutions (ASs) that tackle the accumulation of biochemical and morphologic lesion during routine cold liquid storage in the blood bank, such as the recently introduced alkaline solution AS-7. Here we hypothesize that AS-7 might exert its beneficial effects through metabolic modulation during routine storage.

STUDY DESIGN AND METHODS

Apheresis RBCs were resuspended either in control AS-3 or experimental AS-7, before ultrahigh-performance liquid chromatography-mass spectrometry metabolomics analysis.

RESULTS

Unambiguous assignment and relative quantitation was achieved for 229 metabolites. AS-3 and AS-7 results in many similar metabolic trends over storage, with AS-7 RBCs being more metabolically active in the first storage week. AS-7 units had faster fueling of the pentose phosphate pathway, higher total glutathione pools, and increased flux through glycolysis as indicated by higher levels of pathway intermediates. Metabolite differences are especially observed at 7 days of storage, but were still maintained throughout 42 days.

CONCLUSION

AS-7 formulation (chloride free and bicarbonate loading) appears to improve energy and redox metabolism in stored RBCs in the early storage period, and the differences, though diminished, are still appreciable by Day 42. Energy metabolism and free fatty acids should be investigated as potentially important determinants for preservation of RBC structure and function. Future studies will be aimed at identifying metabolites that correlate with in vitro and in vivo circulation times.