Effect of voxelotor on murine bone marrow and peripheral blood with hematopoietic progenitor cell mobilization for gene therapy of sickle cell disease

In preparation for hematopoietic stem cell mobilization and collection, current ex vivo gene therapy protocols for sickle cell disease require patients to undergo several months of chronic red cell transfusion. For health care equity, alternatives to red cell transfusion should be available. We examined whether treatment with GBT1118, the murine analog of voxelotor, could be a safe and feasible alternative to red cell transfusion. We found that 3 weeks of treatment with GBT1118 increased the percentage of bone marrow hematopoietic stem cells and upon plerixafor mobilization, the percentage of peripheral blood hematopoietic stem cells. Our data suggest that voxelotor should be further explored for its potential safety and utility as preparation for hematopoietic stem cell mobilization and collection.

Hemolysis dictates monocyte differentiation via two distinct pathways in sickle cell disease vaso-occlusion

Sickle cell disease (SCD) is a hereditary hemoglobinopathy characterized by painful vaso-occlusive crises (VOC) and chronic hemolysis. The mononuclear phagocyte system is pivotal to SCD pathophysiology, but the mechanisms governing monocyte/macrophage differentiation remain unknown. This study examined the influence of hemolysis on circulating monocyte trajectories in SCD. We discovered that hemolysis stimulated CSF-1 production, partly by endothelial cells via Nrf2, promoting classical monocyte (CMo) differentiation into blood patrolling monocytes (PMo) in SCD mice. However, hemolysis also upregulated CCL-2 through IFN-I, inducing CMo transmigration and differentiation into tissue monocyte-derived macrophages. Blocking CMo transmigration by anti-P selectin antibody in SCD mice increased circulating PMo, corroborating that CMo-to-tissue macrophage differentiation occurs at the expense of CMo-to-blood PMo differentiation. We observed a positive correlation between plasma CSF-1/CCL-2 ratios and blood PMo levels in patients with SCD, underscoring the clinical significance of these two opposing factors in monocyte differentiation. Combined treatment with CSF-1 and anti-P selectin antibody more effectively increased PMo numbers and reduced stasis compared with single-agent therapies in SCD mice. Altogether, these data indicate that monocyte fates are regulated by the balance between two heme pathways, Nrf2/CSF-1 and IFN-I/CCL-2, and suggest that the CSF-1/CCL-2 ratio may present a diagnostic and therapeutic target in SCD.

How do I initiate and maintain a mobile apheresis service in the era of cellular therapy

BACKGROUND

Mobile delivery of apheresis services is an increasingly important component of health care equity, as patients should not have to transfer care providers or travel far distances to receive critical therapeutic apheresis procedures or cell therapy-based treatments. Therefore, the availability of such services should be expanded.

STUDY DESIGN AND METHODS

In this "How Do I" article, we provide a detailed overview of the elements necessary to initiate and maintain a successful mobile apheresis service, including challenges and potential solutions.

RESULTS

Safe and efficient operation of a mobile apheresis service must consider acquisition of physical assets, such as apheresis sites, personnel, equipment and supplies, communication devices, and transportation vehicles, and optimize organizational aspects, such as staff responsibilities, service partnerships, logistics management, case scheduling and triage, and billing. In the era of cellular therapy, additional critical considerations include regulatory compliance and facility accreditation.

DISCUSSION

To our knowledge, no previous publication provides the extensive details described herein to set up and maintain a successful mobile apheresis service, and thus will be very helpful to those facilities wishing to initiate or expand mobile apheresis services.

Umbilical cord blood: an undervalued and underutilized resource in allogeneic hematopoietic stem cell transplant and novel cell therapy applications

PURPOSE OF REVIEW

The purpose of this review is to primarily discuss the unwarranted decline in the use of umbilical cord blood (UCB) as a source of donor hematopoietic stem cells (HSC) for hematopoietic cell transplantation (HCT) and the resulting important implications in addressing healthcare inequities, and secondly to highlight the incredible potential of UCB and related birthing tissues for the development of a broad range of therapies to treat human disease including but not limited to oncology, neurologic, cardiac, orthopedic and immunologic conditions.

RECENT FINDINGS

When current best practices are followed, unrelated donor umbilical cord blood transplant (CBT) can provide superior quality of life-related survival compared to other allogeneic HSC donor sources (sibling, matched or mismatched unrelated, and haploidentical) through decreased risks of relapse and chronic graft vs. host disease. Current best practices include improved UCB donor selection criteria with consideration of higher resolution human leukocyte antigen (HLA) typing and CD34+ cell dose, availability of newer myeloablative but reduced toxicity conditioning regimens, and rigorous supportive care in the early posttransplant period with monitoring for known complications, especially related to viral and other infections that may require intervention. Emerging best practice may include the use of ex vivo expanded single-unit CBT rather than double-unit CBT (dCBT) or 'haplo-cord' transplant, and the incorporation of posttransplant cyclophosphamide as with haploidentical transplant and/or incorporation of novel posttransplant therapies to reduce the risk of relapse, such as NK cell adoptive transfer. Novel, non-HCT uses of UCB and birthing tissue include the production of UCB-derived immune effector cell therapies such as unmodified NK cells, chimeric antigen receptor-natural killer cells and immune T-cell populations, the isolation of mesenchymal stem cells for immune modulatory treatments and derivation of induced pluripotent stem cells haplobanks for regenerative medicine development and population studies to facilitate exploration of drug development through functional genomics.

SUMMARY

The potential of allogeneic UCB for HCT and novel cell-based therapies is undervalued and underutilized. The inventory of high-quality UCB units available from public cord blood banks (CBB) should be expanding rather than contracting in order to address ongoing healthcare inequities and to maintain a valuable source of cellular starting material for cell and gene therapies and regenerative medicine approaches. The expertise in Good Manufacturing Practice-grade manufacturing provided by CBB should be supported to effectively partner with groups developing UCB for novel cell-based therapies.

Prognostic factors associated with COVID-19 related severity in sickle cell disease

BACKGROUND

Equipoise exists regarding sickle cell disease (SCD) as a risk factor for COVID-19 disease severity and variables that increase risk of COVID-19 severity in SCD. Given our health system's large SCD patient catchment, we analyzed our own experience in this regard.

STUDY METHODS

Retrospective analysis of the clinical course and factors associated with need for hospitalization and ICU admission of SCD patients diagnosed with COVID-19 through the Northwell Health system from March 1 to Dec 31, 2020.

RESULTS

Of 1098 patients with SCD, 3.3% were diagnosed with COVID-19. Overall rates of hospitalization, ICU admission, cohort mortality, and in-hospital mortality were 80%, 19%, 2.5%,and 3.1%, respectively. By multivariable analysis, hospitalization risk was decreased by 60% for every 1 g/dL increase in admission Hb. ICU admission risk was increased by 84% as a health care worker; increased by 45% for every 1000/uL increase in admission immature granulocyte count; and decreased by 17% with hydroxyurea use.

DISCUSSION

High hospitalization rates are compatible with worsened severity upon COVID-19 infection in SCD compared to the general population. Patients should be placed on hydroxyurea to increase their Hb and perhaps lower their neutrophil counts. Health care workers with SCD may warrant special safety precautions.

Further evidence for the benefit of therapeutic plasma exchange for acute multi-organ failure syndrome refractory to red cell exchange in sickle cell disease

Acute multiorgan failure syndrome (MOFS) remains a significant cause of mortality in sickle cell disease (SCD) patients despite red cell exchange (RCE). In small case series and reports, therapeutic plasma exchange (TPE) has shown benefit in MOFS. As further support for consideration of this modality, we present two patients with SCD and MOFS refractory to RCE who were subsequently treated with TPE. Fresh frozen plasma was used as the replacement fluid. Despite estimated hospital mortality of 40% at the time of intensive care unit admission, both patients showed marked clinical improvement with TPE treatment. Our cases add to the evidence supporting the potential inclusion of MOFS secondary to acute SCD as an indication for TPE in the next edition of the American Society of Apheresis Guidelines on the Use of Therapeutic Apheresis in Clinical Practice.

Process and procedural adjustments to improve CD34+ collection efficiency of hematopoietic progenitor cell collections in sickle cell disease

BACKGROUND

Adequate CD34+ collection efficiency (CE) is critical to achieve target CD34+ cell doses in hematopoietic progenitor cell (HPC) collections. Autologous HPC collection in sickle cell disease (SCD) is associated with unstable collection interfaces and low CD34+ CEs. We hypothesized that variables specific to SCD, activation of blood cells and elevated viscosity, might contribute to these issues and made adjustments to the collection process and procedure to address our hypothesis.

STUDY DESIGN AND METHODS

In two patients with SCD undergoing autologous HPC collection on our clinical trial (NCT02193191), we therefore implemented adjustments to the process and procedure in the following areas: proximity of RBC exchange to HPC collection, the type of anticoagulation, and the packing factor setting.

RESULTS

There was no collection interface instability. Our CD34+ CE1s were high at 70% and 51%, and granulocyte CE, platelet CE, and product granulocyte % were remarkably low. Product hematocrits were not as high as previously reported to be required to obtain adequate CEs. Interestingly, one HPC product showed a hemoglobin S (HbS) of 91% at the same time that the peripheral blood (PB) showed a HbS of 22%.

DISCUSSION

Adjustments to the HPC collection process and procedure were associated with adequate CD34+ CEs and low granulocyte and platelet contamination in HPC products from SCD patients. Given the discrepancy in the percentage of sickle RBCs in the product versus the PB, we hypothesize that CD34+ cells and RBCs may aggregate. Our interventions and hypothesis should be further investigated in larger studies.

Evidence for continued dose escalation of plerixafor for hematopoietic progenitor cell collections in sickle cell disease

We present data from our study of plerixafor mobilization (NCT02193191) relevant to the question of whether further dose escalation of plerixafor can address inconsistent adequacy of CD34+ mobilization for gene therapy of sickle cell disease (SCD). We found that, in the same patient, higher plerixafor dosing was associated with higher fold increases in PB CD34+ count, but not necessarily higher absolute CD34+ counts. Variation in pre-apheresis absolute CD34+ counts was related to intra-individual variation in baseline PB CD34+ counts and inter-individual variation in responsiveness to plerixafor. Overall, our results support further studies of continued dose escalation of plerixafor for autologous HPC collection in SCD.

Characteristics of coronavirus disease 19 convalescent plasma donors and donations in the New York metropolitan area

Background

Convalescent plasma (CP) is an important initial treatment in pandemics and the New York (NY) metropolitan area is likely to remain a hotspot for collection and distribution of such units. This study reports characteristics of coronavirus disease 19 CP (CCP) donors and their donations to the New York Blood Center (NYBC).

Study design and methods

All CCP data from our first day of collection on March 26th through July 7th, 2020 are included in this retrospective analysis. Donor and donation data were extracted from NYBC electronic databases. SARS‐CoV‐2 antibody testing was initially performed by the NY State Department of Health, and later by NYBC using Ortho and Abbott platforms.

Results

CCP donor age and ABO distributions were consistent with reported lower COVID‐19 susceptibility in O blood types. CCP versus whole blood donors had similar on‐site deferrals, but higher post‐donation deferral rates. CCP versus routine plasmapheresis donations had higher vasovagal reactions but similar product rejection rates. Changes in antibody (Ab) test platforms resulted in significant changes in the percent of donors regarded as antibody positive. Donor correlates with higher anti‐spike total Ig S/CO ratios were Hispanic ethnicity, overweight body mass index, and longer symptom duration; and with higher anti‐nucleocapsid IgG S/CO ratios were male gender, older age, Hispanic ethnicity, and fewer days between symptom onset and first donation.

Discussion

We identify donor characteristics not previously reported to correlate with Ab titer. Our analysis should assist with donor outreach strategies, blood center operating logistics, and recruitment of high titer donors.

Potentially modifiable predictors of cell collection efficiencies and product characteristics of allogeneic hematopoietic progenitor cell collections

BACKGROUND

Hematopoietic progenitor cell (HPC) and immune effector cell (IEC) therapies often require high doses of mononuclear cells (MNCs), whether CD34+ cells, lymphocytes, or monocytes. Cells for IEC can be sourced from HPC products. We thus examined potentially modifiable variables affecting collection efficiencies (CEs) of MNC subsets in HPC collection and also of the typically undesired cell types of platelets, granulocytes, and red cells, which hinder downstream processing. Finally, we sought to confirm previously indeterminate studies of the effect of an adjusted collect flow rate (CFR) on CD34+ CE.

STUDY DESIGN AND METHODS

We performed univariate and multivariate regression analyses of all 135 National Marrow Donor Program (NMDP) HPC collections in 2019 and compared these fixed CFR procedures to previous NMDP collections using adjusted CFRs.

RESULTS

Target cell CEs decreased with increasing peripheral blood (PB) concentration and were associated with different cell type locations within the MNC layer. CEs of undesired cell types varied with standard procedural parameters (inlet flow rate, whole blood processed, etc.). Interestingly, some CEs increased with preapheresis hematocrit. Finally, adjusting the CFR by PB MNC count improved MNC CE but not CD34+ CE.

CONCLUSION

Correlation of target cell CEs with their PB concentration and different cell type locations by depth within the MNC layer indicates the importance of investigating the compensatory fine-tuning of procedure variables to improve CE. Correlation of CEs with PB hematocrit, and CFR adjustment by a modified PB MNC and/or PB CD34 algorithm should be further explored. Adjusting standard procedural parameters may reduce product contamination.

Safety and benefits of automated red cell depletion-exchange compared to standard exchange in patients with sickle cell disease undergoing chronic transfusion

BACKGROUND

The Spectra Optia allows automated performance of red blood cell reduction and isovolemic hemodilution (IHD) prior to standard red cell exchange (RCE), and is primarily intended for patients with sickle cell disease (SCD) undergoing chronic RCE. Data on the safety of inducing transient further anemia and the benefits of IHD-RCE is limited and occasionally contradictory.

STUDY DESIGN AND METHODS

In this retrospective crossover analysis of six patients with SCD who underwent chronic exchange with standard RCE (Cobe Spectra) followed by IHD-RCE (Spectra Optia), we compared safety and benefit outcomes with IHD-RCE vs standard RCE.

RESULTS

There were statistically but not clinically significant drops in blood pressure in the post-IHD phase. With IHD-RCE, there were significant reductions in red blood cell (RBC) usage and/or lower fraction of cells and significant increases in postprocedure hematocrit (Hct) associated with increased preprocedure Hct. There were no differences achieved in the time interval between procedures or in the net RBC gain with IHD-RCE. Overall, there were also no significant differences in pre- and postprocedure percentage of hemoglobin S, reticulocyte count, interval daily hemoglobin A decrement, or postprocedure white blood cell, neutrophil, or platelet counts.

CONCLUSIONS

Our study supports that IHD-RCE can be safely used in patients with stroke risk and compared to standard RCE, results in benefits of lower RBC usage and/or fraction of cells remaining and higher postprocedure Hct associated with higher preprocedure Hct. These findings support wider use of IHD-RCE, especially in the current environment with reduced availability of minority units.

Hemolysis inhibits humoral B-cell responses and modulates alloimmunization risk in patients with sickle cell disease

Red blood cell alloimmunization remains a barrier for safe and effective transfusions in sickle cell disease (SCD), but the associated risk factors remain largely unknown. Intravascular hemolysis, a hallmark of SCD, results in the release of heme with potent immunomodulatory activity, although its effect on SCD humoral response, specifically alloimmunization, remains unclear. Here, we found that cell-free heme suppresses human B-cell plasmablast and plasma cell differentiation by inhibiting the DOCK8/STAT3 signaling pathway, which is critical for B-cell activation, as well as by upregulating heme oxygenase 1 (HO-1) through its enzymatic byproducts, carbon monoxide and biliverdin. Whereas nonalloimmunized SCD B cells were inhibited by exogenous heme, B cells from the alloimmunized group were nonresponsive to heme inhibition and readily differentiated into plasma cells. Consistent with a differential B-cell response to hemolysis, we found elevated B-cell basal levels of DOCK8 and higher HO-1-mediated inhibition of activated B cells in nonalloimmunized compared with alloimmunized SCD patients. To overcome the alloimmunized B-cell heme insensitivity, we screened several heme-binding molecules and identified quinine as a potent inhibitor of B-cell activity, reversing the resistance to heme suppression in alloimmunized patients. B-cell inhibition by quinine occurred only in the presence of heme and through HO-1 induction. Altogether, these data suggest that hemolysis can dampen the humoral B-cell response and that B-cell heme responsiveness maybe a determinant of alloimmunization risk in SCD. By restoring B-cell heme sensitivity, quinine may have therapeutic potential to prevent and inhibit alloimmunization in SCD patients.

Red cell exchange for patients with sickle cell disease: an international survey of current practices

INTRODUCTION

Red cell exchange (RCE) therapy is increasingly used to treat patients with acute or chronic manifestations of sickle cell disease (SCD). However, little is known regarding the most safe and effective practice parameters associated with this particular therapy.

METHODS

A SCD subcommittee of members of the American Society for Apheresis (ASFA) developed a 122-question survey and administered it via email to other ASFA members. The survey inquired about clinical indications for treatment, practice patterns, and transfusion policies for RCE when used for patients with SCD.

RESULTS

Ninety-nine distinct institutions completed the survey. Twenty-one (21%) were from outside of the US. Twenty-two (22%) provided chronic transfusion therapy to >10 patients, and both adult (25%) and pediatric-focused services (20%) were represented. Common acute indications for RCE included acute chest syndrome, acute ischemic stroke, and pre-surgical prophylaxis. Common chronic indications included primary stroke prophylaxis, secondary stroke prophylaxis, and recurrent acute chest syndrome. Respondents most commonly set a post-RCE treatment target of 30% for the hematocrit and hemoglobin S levels, regardless of the therapeutic indication. Units for RCE were phenotypically matched in 95% of cases. About 40% of respondents reported using isovolemic hemodilution.

CONCLUSIONS

This survey solicited the current practice variations in RCE from a diverse range of practice sites. Many sites reported similar practice patterns and challenges but some variations emerged. To our knowledge, this survey represents the largest and most in-depth investigation of the use of RCE for patients with SCD, and could inform future studies in the field.

American Society of Hematology 2020 guidelines for sickle cell disease: transfusion support

BACKGROUND

Red cell transfusions remain a mainstay of therapy for patients with sickle cell disease (SCD), but pose significant clinical challenges. Guidance for specific indications and administration of transfusion, as well as screening, prevention, and management of alloimmunization, delayed hemolytic transfusion reactions (DHTRs), and iron overload may improve outcomes.

OBJECTIVE

Our objective was to develop evidence-based guidelines to support patients, clinicians, and other healthcare professionals in their decisions about transfusion support for SCD and the management of transfusion-related complications.

METHODS

The American Society of Hematology formed a multidisciplinary panel that was balanced to minimize bias from conflicts of interest and that included a patient representative. The panel prioritized clinical questions and outcomes. The Mayo Clinic Evidence-Based Practice Research Program supported the guideline development process. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to form recommendations, which were subject to public comment.

RESULTS

The panel developed 10 recommendations focused on red cell antigen typing and matching, indications, and mode of administration (simple vs red cell exchange), as well as screening, prevention, and management of alloimmunization, DHTRs, and iron overload.

CONCLUSIONS

The majority of panel recommendations were conditional due to the paucity of direct, high-certainty evidence for outcomes of interest. Research priorities were identified, including prospective studies to understand the role of serologic vs genotypic red cell matching, the mechanism of HTRs resulting from specific alloantigens to inform therapy, the role and timing of regular transfusions during pregnancy for women, and the optimal treatment of transfusional iron overload in SCD.

Validation of simple prediction algorithms to consistently achieve CD3+ and postselection CD34+ targets with leukapheresis

BACKGROUND

Cellular therapies using engineered T cells, haploidentical transplants, and autologous gene therapy are increasing. Specified CD3+ or high CD34+ doses are typically required for subsequent manufacturing, manipulation, or CD34+ selection. Simple, practical, and reliable lymphocyte and hematopoietic progenitor cell (HPC) collection algorithms accounting for subsequent CD34+ selection have not been published.

STUDY DESIGN AND METHODS

In this analysis of 15 haploidentical donors undergoing tandem lymphocyte and HPC collections, we validated one-step, practical prediction algorithms (Appendix S1, available as supporting information in the online version of this paper) that use conservative facility-specific collection efficiencies, CD34+ selection efficiency, and donor-specific peripheral counts to reliably achieve the target CD3+ and CD34+ product doses. These algorithms expand on our previously published work regarding predictive HPC collection algorithms.

RESULTS

Ninety-three percent of lymphocyte and 93% of CD34+ collections achieved the final target CD3+ and CD34+ product dose when our algorithm-calculated process volumes were used. Linear regression analysis of our algorithms for CD3+, preselection CD34+, and postselection CD34+ showed statistically significant models with R² of 0.80 (root mean square error [RMSE], 31.3), 0.72 (RMSE, 385.7), and 0.56 (RMSE, 326.0), respectively, all with p values less than 0.001.

CONCLUSION

Because achievement of CD3+ or CD34+ dose targets may be critical for safety and efficacy of cell therapies, these simple, practical, and reliable prediction algorithms for lymphocyte and HPC collections should be very useful for collection facilities.

Emerging roles of adjunct therapies in acquired thrombotic thrombocytopenia purpura

Acquired thrombotic thrombocytopenia purpura (aTTP) is caused by autoantibody-mediated severe deficiency of the von Willebrand factor (vWF) cleaving protease ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13), with subsequent accumulation of ultra-large vWF-multimers that spontaneously form platelet-VWF complexes and microthrombi within the microcirculation. Therapeutic plasma exchange (TPE), by removing autoantibodies and excess ultra-large vWF multimers and replenishing ADAMTS13 activity, remains the urgent primary initial treatment. Although heterogeneity in treatment exists, most centers add upfront immunosuppression with steroids, and many also add upfront rituximab. Refractoriness, exacerbation and relapse are commonly treated with adjunct rituximab. Despite adjunct steroids and rituximab, TTP refractoriness, exacerbation, relapse, morbidity, and mortality remain problematic. Newer adjunct therapies include suppression of ADAMTS13 autoantibody production via plasma cell depletion, inhibition of vWF-platelet interaction, and replenishment of ADAMTS13 function with recombinant ADAMTS13 protein.

Safety and efficacy of plerixafor dose escalation for the mobilization of CD34+ hematopoietic progenitor cells in patients with sickle cell disease: interim results

Gene therapy for sickle cell disease is limited by the yield of hematopoietic progenitor cells that can be harvested for transduction or gene editing. We therefore performed a phase I dose-escalation study of the hematopoietic progenitor cell mobilizing agent plerixafor to evaluate the efficacy and safety of standard dosing on peripheral blood CD34⁺ cell mobilization. Of 15 patients enrolled to date, only one was chronically transfused and ten were on hydroxyurea. Of eight patients who achieved a CD34⁺ cell concentration >30 cells/μL, six were on hydroxyurea. There was no clear dose response to increasing plerixafor dosage. There was a low rate of serious adverse events; two patients developed vaso-occlusive crises, at the doses of 80 μg/kg and 240 μg/kg. Hydroxyurea may have contributed to the limited CD34⁺ mobilization by affecting baseline peripheral blood CD34 counts, which correlated strongly with peak peripheral blood CD34 counts. Plerixafor administration did not induce significant increases in the fraction of activated neutrophils, monocytes, or platelets. However, increased neutrophils positive for activated β2 integrin and Mac-1 were associated with serious adverse events. In summary, plerixafor was well tolerated but did not achieve consistent CD34⁺ cell mobilization in this cohort of patients, most of whom were being actively treated with hydroxyurea and only one was chronically transfused. The study will continue with escalation of the dose of plerixafor and modification of hydroxyurea administration. Clinicaltrials.gov identifier: NCT02193191.

Sustained treatment of sickle cell mice with haptoglobin increases HO-1 and H-ferritin expression and decreases iron deposition in the kidney without improvement in kidney function

There is growing evidence that extracellular haemoglobin and haem mediate inflammatory and oxidative damage in sickle cell disease. Haptoglobin (Hp), the scavenger for free haemoglobin, is depleted in most patients with sickle cell disease due to chronic haemolysis. Although single infusions of Hp can ameliorate vaso-occlusion in mouse models of sickle cell disease, prior studies have not examined the therapeutic benefits of more chronic Hp dosing on sickle cell disease manifestations. In the present study, we explored the effect of Hp treatment over a 3-month period in sickle mice at two dosing regimens: the first at a moderate dose of 200 mg/kg thrice weekly and the second at a higher dose of 400 mg/kg thrice weekly. We found that only the higher dosing regimen resulted in increased haem-oxygenase-1 and heavy chain ferritin (H-ferritin) expression and decreased iron deposition in the kidney. Despite the decreased kidney iron deposition following Hp treatment, there was no significant improvement in kidney function. However, there was a nearly significant trend towards decreased liver infarction.

No evidence for cell activation or brain vaso-occlusion with plerixafor mobilization in sickle cell mice

Gene therapy for sickle cell disease is currently in active trials. Collecting hematopoietic progenitor cells safely and effectively is challenging, however, because granulocyte colony stimulating factor, the drug used most commonly for mobilization, can cause life-threatening vaso-occlusion in patients with sickle cell disease, and bone marrow harvest requires general anesthesia and multiple hip bone punctures. Plerixafor is an inhibitor of the CXCR4 chemokine receptor on hematopoietic progenitor cells, blocking its binding to SDF-1 (CXCL12) on bone marrow stroma. In support of a clinical trial in patients with sickle cell disease of plerixafor mobilization (NCT02193191), we administered plerixafor to sickle cell mice and found that it mobilizes hematopoietic progenitor cells without evidence of concomitant cell activation or brain vaso-occlusion.

Single-dose intravenous gammaglobulin can stabilize neutrophil Mac-1 activation in sickle cell pain crisis

Intravenous immunoglobulin (IVIG) decreases neutrophil adhesion to endothelium and red blood cell-neutrophil interactions in sickle cell mice undergoing vaso-occlusion. In this Phase I clinical trial of sickle cell anemia (SCA) patients admitted with pain crisis, we evaluated the status of adhesion molecules on neutrophils in control and IVIG-treated subjects pre- and post-infusion up to 800 mg/kg, the same dose used in murine studies. Mac-1 function significantly decreased from baseline in the low-dose IVIG (200-400 mg/kg) cohorts. IVIG-related adverse events may have occurred in the high-dose (600-800 mg/kg) cohorts. There were no significant increases in neutrophil and leukocyte counts, suggesting that IVIG may more selectively inhibit Mac-1 function as opposed to neutrophil adhesion. This study provides the first in-human validation of pre-clinical murine studies that IVIG can decrease Mac-1 function.

Retrospective analysis of community hospital red blood cell recovery procedures: improved utilization needed for effectiveness

BACKGROUND

Perioperative blood recovery (PBR) is an important component of patient blood management. We analyzed our experience providing PBR for community hospitals to determine procedure types and clinical variables associated with efficacy and cost-effectiveness.

STUDY DESIGN AND METHODS

PBR cases (>25,000) from January 2008 through December 2012 were analyzed. For each procedure type, the median number of returned red blood cell units (rRBCs) and ratio of cases with at least 1 to less than 1 rRBC unit were calculated. Clinical predictors of rRBC were identified by linear and logistic regression.

RESULTS

The overall median rRBC was 0.29 units despite median estimated blood loss (EBL) of 350 mL. Only three of 31 common procedure types had ≥1:<1 rRBC ratios near to or higher than 1. In nine of 31 common procedure types, at least 50% of cases had no rRBC return. Linear regression demonstrated significant association of rRBCs with increased EBL, longer operative duration, surgeon, PBR device type (autoLog vs. CS5), and decreasing age. EBL, autoLog use, high surgeon case volume, vascular procedures, and emergent versus elective procedures associated with higher odds of at least 1 rRBC.

CONCLUSION

Discrepancy between rRBC and EBL and high percentages of cases with no rRBC suggests that PBR technique and case selection need optimization. Identification of procedure types and variables associated with PBR efficacy (≥1 rRBC) should improve utilization of PBR. Association of autoLog use with higher rRBC warrants further investigation.

Prospective study of mobilization kinetics up to 18 hours after late-afternoon dosing of plerixafor

BACKGROUND

The current FDA-approved time interval between plerixafor dosing and apheresis initiation is approximately 11 hours, but this time interval is impractical for most care providers. Few studies have examined mobilization kinetics beyond 11 hours in multiple myeloma (MM) and non-Hodgkin's lymphoma (NHL) patients. Therefore, this study's intent was to analyze an interval of 17 to 18 hours between plerixafor dosing and apheresis initiation.

STUDY DESIGN AND METHODS

In 11 patients with MM or NHL, 240 μg/kg plerixafor was administered at 5 p.m. on Day 4 of granulocyte-colony-stimulating factor (G-CSF) mobilization. Peripheral blood (PB) CD34+ and CD34+CD38- concentrations were enumerated every 2 hours until 7 a.m. and immediately before apheresis on Day 5, for a total interval time of 17 to 18 hours after plerixafor. Data were analyzed using mixed-model analysis of repeated measures and paired t testing.

RESULTS

Ten of the 11 subjects achieved a CD34+ product count of more than 2 × 10(6) /kg with a single leukapheresis procedure. All 10 had a preplerixafor PB CD34+ concentration ([CD34+]) of at least 10/μL. PB [CD34+] was not different between 10 and 18 hours after plerixafor (p = 0.8). In contrast, PB CD34+CD38- concentrations significantly increased from 10 to 18 hours after plerixafor (p = 0.03).

CONCLUSIONS

In MM and NHL patients with adequate preplerixafor [CD34+], leukapheresis initiated 14 to 18 hours after plerixafor and G-CSF mobilization may not impair adequate CD34+ collection and may increase more primitive CD34+CD38- collection. In this subset of patients, late-afternoon dosing of plerixafor at 5 p.m. with initiation of next-day apheresis as late as 11 a.m. appears feasible without loss of efficacy.

Results of lookback for Chagas disease since the inception of donor screening at New York Blood Center

BACKGROUND

Chagas disease is a parasitic infection by Trypanosoma cruzi, typically transmitted via infected triatomine bug fecal contamination of bite sites. Other routes of infection include congenital, oral, organ transplantation, and blood product transmission.

STUDY DESIGN AND METHODS

From 2007 until 2011, New York Blood Center screened donations for the presence of T. cruzi antibodies using a Food and Drug Administration-approved test. Confirmatory testing was performed and recipients of units donated by confirmed-positive donors were investigated via lookback.

RESULTS

A total of 204 donors were T. cruzi antibody positive representing 0.019% of all donors during this time period (1,066,516 unique donors screened). Of the enzyme-linked immunosorbent assay-reactive donors, 77 were confirmed positive by radioimmunoprecipitation assay (0.007%). At least 154 units from 29 of the confirmed-positive donors had been transfused to 141 recipients. At the time of lookback, 48 of the 141 recipients were alive and seven underwent T. cruzi screening. Two recipients were found to be immunofluorescence assay (IFA) positive. Both IFA-positive recipients received a leukoreduced apheresis platelet unit (two separate donations) from the same confirmed positive donor, a 72-year-old immigrant from Argentina.

CONCLUSIONS

Lookback analysis was able to identify the first two cases of probable transfusion-transmitted T. cruzi infection since implementation of the national screening program, which increases the total number of reported cases in the United States to 8.

Prospective cohort study of the circadian rhythm pattern in allogeneic sibling donors undergoing standard granulocyte colony-stimulating factor mobilization

Introduction

Prior in vivo murine studies suggest circadian oscillations for hematopoietic stem cell release, which are maintained following administration of granulocyte colony-stimulating factor (G-CSF) or plerixafor. Furthermore, retrospective data analysis of healthy donors who underwent G-CSF-induced mobilization demonstrated significantly increased CD34⁺ cell yields when collected in the afternoon compared with the morning.

Methods

A prospective study was conducted to directly examine the number of peripheral blood CD34⁺ and CD34⁺CD38^– progenitor/stem cells at baseline and then every 6 hours for 24 hours on days 4 to 5 of G-CSF (10 μg/kg/day in the morning) mobilization in 11 allogeneic donors. Data were analyzed using mixed-model analysis of repeated measures.

Results

Whereas we observed a significant increase in CD34⁺ cell counts toward the evening, counts were then sustained on the morning of day 5. The correlation between CD34⁺CD38^– cell counts and the less defined CD34⁺ populations was weak.

Conclusions

Our results suggest that the pharmacodynamic activity and timing of G-CSF may alter endogenous progenitor rhythms. Donor age, medical history, and medications may also impact circadian rhythm. Further studies should examine the circadian rhythm at the peak of G-CSF mobilization and should consider potential confounders such as the time of G-CSF administration and the age of the subjects.

Successful split liver-kidney transplant for factor H associated hemolytic uremic syndrome

BACKGROUND AND OBJECTIVES

A male infant with a family history of thrombotic microangiopathy developed atypical hemolytic uremic syndrome (aHUS).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Case report.

RESULTS

Genetic analysis demonstrated a heterozygous mutation (S1191L) of CFH, the gene coding complement factor H (CFH). The child suffered many episodes of HUS, each treated with plasma exchange. In time, despite initiation of a prophylactic regimen of plasma exchange, his renal function declined significantly. At the age of 4 yr he received a (split liver) combined liver-kidney transplant (LKT) with preoperative plasma exchange and enoxaparin anticoagulation. Initial function of both grafts was excellent and is maintained for nearly 2 yr.

CONCLUSIONS

This report adds to the small but growing number of individuals in whom LKT has provided a favorable outcome for aHUS associated with CFH mutation, expands the technique of using a split liver graft, and describes the unique histologic features of subclinical liver disease in HUS.

Mobilized hematopoietic stem cell yield depends on species-specific circadian timing

Endogenous rhythmicity likely evolved as a mechanism allowing organisms to anticipate predictable daily changes in the environment (Rutter et al., 2002). Under homeostasis, murine hematopoietic stem cell (HSC) egress is orchestrated by rhythmic beta 3 adrenergic signals delivered by the sympathetic nervous system (SNS) that regulate Cxcl12 expression in stromal cells (Mendez-Ferrer et al., 2008). Here, we show that CXCR4 is also regulated under circadian control whose rhythm is synchronized with its ligand, CXCL12, to optimize HSC trafficking. These circadian oscillations are inverted in humans compared to the mouse and continue to influence the yield even when stem cell mobilization is enforced. Our results suggest that the human HSC yield for clinical transplantation might be significantly greater if patients were harvested during the evening compared to the morning.

In vivo gene marking of rhesus macaque long-term repopulating hematopoietic cells using a VSV-G pseudotyped versus amphotropic oncoretroviral vector

BACKGROUND

Gene transfer efficiency into primitive hematopoietic cells may be limited by their expression of surface receptors allowing vector entry. Vectors pseudotyped with the vesicular stomatitis virus (VSV-G) envelope do not need receptors to enter cells, and therefore may provide superior transduction efficiency.

METHODS

Using a competitive repopulation model in the rhesus macaque, we examined in vivo gene marking levels of blood cells transduced with two vectors: (i) a VSV-G pseudotyped retrovirus and (ii) a conventional amphotropic retrovirus. The VSV-G vector, containing the human glucose-6-phosphate dehydrogenase (G6PD) gene, was constructed for treatment of severe hemolytic anemia caused by G6PD deficiency. Three myeloablated animals were transplanted with peripheral blood CD34+ cells, half of which were transduced with the VSV-G vector and the other half with the amphotropic vector.

RESULTS

In all animals post-transplantation, levels of in vivo marking in circulating granulocytes and mononuclear cells were similar: 1% or less with both vectors. In one animal, the human G6PD enzyme transferred by the VSV-G vector was expressed in erythrocytes, early after transplantation, at a level of 45% of the endogenous rhesus G6PD protein.

CONCLUSIONS

In a clinically relevant animal model, we found similar in vivo marking with a VSV-G pseudotyped and a standard amphotropic oncoretroviral vector. Amphotropic receptor expression may not be a limiting factor in transduction efficiency, but VSV-G pseudotypes possess other practical advantages that may make them advantageous for clinical use.

Genetic marking as an approach to studying in vivo hematopoiesis: progress in the non-human primate model

Retroviral insertion site analysis following transplantation of marked hematopoietic stem cells (HSCs) is a powerful method for studying hematopoiesis in vivo. High-level gene transfer efficiency was achieved in murine models in the late 1980s, but early human gene transfer protocols into hematopoietic stem and progenitor cells using the murine methodology showed consistently poor results. The utility of non-human primates as pre-clinical models has since become apparent. Modifications in retroviral transduction conditions have resulted in stable long-term gene transfer efficiency as high as 15-20% to primitive repopulating cells in non-human primate models. This has permitted, for the first time in a large animal model, tracking of individual stem and progenitor cell clones via insertion site analysis, an advantage over competitive transplantation studies, which cannot firmly evaluate the number or life span of individual clones contributing to hematopoiesis. Retroviral tracking studies in mice suggest that stable hematopoiesis may be dominated by a small number of clones, but these studies have been limited by insensitive detection methods, low numbers of transplanted stem cells, and limited life span of immunodeficient mice. Autologous transplantation studies in non-human primates have just begun and have the potential to shed light on controversial issues such as the number of clones contributing to stable hematopoiesis, clonal succession, and lineage commitment, as well as the effect of clinically relevant manipulations such as cytokines, chemotherapy, and radiation on hematopoiesis. These approaches will have significant impact in studying various aspects of stem cell biology including the phenomenon of stem cell plasticity.

Assessment of rapid remobilization intervals with G-CSF and SCF in murine and rhesus macaque models

BACKGROUND

Defining the optimum regimen and time for repeat peripheral blood progenitor cell mobilization would have important clinical applications.

STUDY DESIGN AND METHODS

Remobilization with SCF and G-CSF at 2 weeks after an initial mobilization in mice and at 2 or 4 weeks after an initial mobilization in nonhuman primates was examined. In mice, competitive repopulation assays were used to measure long-term progenitor cell-repopulating activity. In monkeys, mobilization of hematopoietic progenitor CFUs was used as a surrogate marker for progenitor cell-repopulating ability.

RESULTS

Efficacy of progenitor cell remobilization differed in the two animal species. In mice, peripheral blood progenitor cell-repopulating ability with repeat mobilization at 2 weeks was 70 percent of that with the initial mobilization. In monkeys, there was no significant difference in peripheral blood progenitor cell mobilization between the initial and the repeat mobilizations at 2 weeks. In mobilizations separated by 4 weeks, however, peripheral blood progenitor cell mobilization was higher than that with initial mobilizations.

CONCLUSION

In animal models, mobilization of peripheral blood progenitor cells with remobilization after a 2-week interval is similar to or moderately decreased from that with the initial mobilization. Progenitor cell collection at this time point may be useful in certain clinical circumstances. A 4-week interval between remobilizations may be preferable. Clinical trials in humans would be useful to clarify these issues.