Unstimulated leukapheresis in patients and donors: comparison of two apheresis systems

A guide to the collection of T-cells by apheresis for ATMP manufacturing-recommendations of the GoCART coalition apheresis working group

Autologous chimeric antigen receptor-modified T-cells (CAR-T) provide meaningful benefit for otherwise refractory malignancies. As clinical indications for CAR-T cells are expanding, hospitals hitherto not active in the field of immune effector cell therapy will need to build capacity and expertise. The GoCART Coalition seeks to disseminate knowledge and skills to facilitate the introduction of CAR-T cells and to standardize management and documentation of CAR-T cell recipients, in order to optimize outcomes and to be able to benchmark clinical results against other centers. Apheresis generates the starting material for CAR-T cell manufacturing. This guide provides some initial suggestions for patient's apheresis readiness and performance to collect starting material and should thus facilitate the implementation of a CAR-T-starting material apheresis facility. It cannot replace, of course, the extensive training needed to perform qualitative apheresis collections in compliance with national and international regulations and assess their cellular composition and biological safety.

Leukapheresis and Hyperleukocytosis, Past and Future

Hyperleukocytosis is a hematologic crisis caused by excessive proliferation of leukemic cells and has a relatively high early mortality due to a series of severe complications. Therefore, prompt and effective intervention is required. Leukapheresis performed using apheresis equipment to separate leukocytes from peripheral blood, at the same time returns autologous plasma, platelets and erythrocytes to the patient, is applied clinically for the treatment of hyperleukocytosis. Leukapheresis not only removes excessive leukocytes rapidly and corrects metabolic abnormalities but also alleviates the symptoms of leukostasis. In addition, the procedure of leukapheresis is generally well tolerated. Leukapheresis has become one of the most imperative adjuvant therapies to treat hyperleukocytosis, especially in the patient who was not inappropriate to cytoreduce with Ara-C or hydroxyurea. In this review, we present the background of leukapheresis development and highlight its clinical application in hyperleukocytic leukemia patients.

Unstimulated apheresis for chimeric antigen receptor manufacturing in pediatric/adolescent acute lymphoblastic leukemia patients

Autologous unstimulated leukapheresis product serves as starting material for a variety of innovative cell therapy products, including chimeric antigen receptor (CAR)-modified T-cells. Although it may be reasonable to assume feasibility and efficiency of apheresis for CAR-T cell manufacture, several idiosyncrasies of these patients warrant their separate analysis: target cells (mononuclear cells [MNC] and T-cells) are relatively few which may instruct the selection of apheresis technology, low body weight, and, hence, low total blood volume (TBV) can restrict process and product volume, and patients may be in compromised health. We here report outcome data from 46 consecutive leukaphereses in 33 unique pediatric patients performed for the purpose of CD19-CAR-T-cell manufacturing. Apheresis targets of 2×10⁹ MNC/1×10⁹ T-cells were defined by marketing authorization holder specification. Patient weight was 8 to 84 kg; TBV was 0.6 to 5.1 L. Spectra Optia apheresis technology was used. For 23 patients, a single apheresis sufficed to generate enough cells and manufacture CAR-T-cells, the remainder required two aphereses to meet target dose and/or two apheresis series because of production failure. Aphereses were technically feasible and clinically tolerable without serious adverse effects. The median collection efficiencies for MNC and T-cells were 53% and 56%, respectively. In summary, CAR apheresis in pediatric patients, including the very young, is feasible, safe and efficient, but the specified cell dose targets can be challenging in smaller children. Continuous monitoring of apheresis outcomes is advocated in order to maintain quality.

Current Challenges in Providing Good Leukapheresis Products for Manufacturing of CAR-T Cells for Patients with Relapsed/Refractory NHL or ALL

Background: T lymphocyte collection through leukapheresis is an essential step for chimeric antigen receptor T (CAR-T) cell therapy. Timing of apheresis is challenging in heavily pretreated patients who suffer from rapid progressive disease and receive T cell impairing medication. Methods: A total of 75 unstimulated leukaphereses were analyzed including 45 aphereses in patients and 30 in healthy donors. Thereof, 41 adult patients with Non-Hodgkin’s lymphoma (85%) or acute lymphoblastic leukemia (15%) underwent leukapheresis for CAR-T cell production. Results: Sufficient lymphocytes were harvested from all patients even from those with low peripheral lymphocyte counts of 0.18/nL. Only four patients required a second leukapheresis session. Leukapheresis products contained a median of 98 × 10⁸ (9 - 341 × 10⁸) total nucleated cells (TNC) with 38 × 10⁸ (4 - 232 × 10⁸) CD3+ T cells. Leukapheresis products from healthy donors as well as from patients in complete remission were characterized by high TNC and CD3+ T lymphocyte counts. CAR-T cell products could be manufactured for all but one patient. Conclusions: Sufficient yield of lymphocytes for CAR-T cell production is feasible also for patients with low peripheral blood counts. Up to 12–15 L blood volume should be processed in patients with absolute lymphocyte counts ≤ 1.0/nL.

Progressive multifocal leukoencephalopathy in a patient post allo-HCT successfully treated with JC virus specific donor lymphocytes

BACKGROUND

Progressive multifocal leukoencephalopathy is a demyelinating CNS disorder. Reactivation of John Cunningham virus leads to oligodendrocyte infection with lysis and consequent axonal loss due to demyelination. Patients usually present with confusion and seizures. Late diagnosis and lack of adequate therapy options persistently result in permanent impairment of brain functions. Due to profound T cell depletion, impairment of T-cell function and potent immunosuppressive factors, allogeneic hematopoietic cell transplantation recipients are at high risk for JCV reactivation. To date, PML is almost universally fatal when occurring after allo-HCT.

METHODS

To optimize therapy specificity, we enriched JCV specific T-cells out of the donor T-cell repertoire from the HLA-identical, anti-JCV-antibody positive family stem cell donor by unstimulated peripheral apheresis [1]. For this, we selected T cells responsive to five JCV peptide libraries via the Cytokine Capture System technology. It enables the enrichment of JCV specific T cells via identification of stimulus-induced interferon gamma secretion.

RESULTS

Despite low frequencies of responsive T cells, we succeeded in generating a product containing 20 000 JCV reactive T cells ready for patient infusion. The adoptive cell transfer was performed without complication. Consequently, the clinical course stabilized and the patient slowly went into remission of PML with JCV negative CSF and containment of PML lesion expansion.

CONCLUSION

We report for the first time feasibility of generating T cells with possible anti-JCV activity from a seropositive family donor, a variation of virus specific T-cell therapies suitable for the post allo transplant setting. We also present the unusual case for successful treatment of PML after allo-HCT via virus specific T-cell therapy.

Automated mononuclear cell collection: a feasibility study employing a new software for extracorporeal photopheresis

BACKGROUND AND OBJECTIVES

Very recently, Fresenius Kabi, improved the software (autoMNC lymphocytes, SW 04.03.08) for mononuclear cells (MNCs) collection with the aim to ameliorate the quality of harvest, employing the automated autoMNC lymphocytes software SW 04.03.09. Herein, we report the results of an observational study evaluating the feasibility of MNCs collection in patients undergoing extracorporeal photopheresis (ECP) at our centre, using the new COM.TEC software 04.03.08c for MNC collection, afterwards integrated in the software 04.03.09, available on the market since November 2018.

MATERIALS AND METHODS

Thirty adult patients (21 males and 9 females) with GvHD, Chronic Lung Allograft Dysfunction or renal rejection, were consecutively enrolled to undergo 1 ECP procedure by the offline technique, according to our internal protocol, processing 1·5 blood volumes. Feasibility of collection was defined as: Hct in collection bag ≤5%, MNCs purity (percentage of MNCs/bag) ≥80%, MNCs collection efficiency (CE2) ≥60%, patient's platelet depletion ≤50%.

RESULTS

Thirty ECP procedures were evaluated. Feasibility (defined by the four parameters previously described) of MNCs collection was observed in 1 out of the 30 harvests analysed. Median Hct in the product was 3·45% (IQR: 2·6-5·0), and median MNCs purity was 97·2% (IQR 89·1-98·6). Median CE2 for MNCs was 21·4% (IQR: 11·9-41·2), and median patient's platelet depletion was 36·2% (IQR 21·9-51·4).

CONCLUSION

The autoMNC lymphocytes software SW 04.03.08c for MNCs collection in ECP setting demonstrated to collect a good quality product in terms of purity and RBC contamination even if the collection efficiency and platelet contamination must be improved.

Factors affecting lymphocyte collection efficiency for the manufacture of chimeric antigen receptor T cells in adults with B-cell malignancies

BACKGROUND

The clinical and procedural parameters that affect the optimal collection of lymphocytes for the production of chimeric antigen receptor (CAR) T cells remain undefined but are increasingly important, as commercial products are now available. We evaluated determinants of low lymphocyte collection efficiency (CE) and the rate of successful CAR T-cell manufacture in middle-aged and older adults with advanced B-cell malignancies.

STUDY DESIGNS AND METHODS

Mononuclear cell collections using two apheresis platforms (COBE Spectra and Spectra Optia, Terumo BCT) from patients participating in a CD19-directed CAR T-cell therapy trial were reviewed. Patient- and disease-specific factors, peripheral blood counts, apheresis parameters, and product cell counts were analyzed to determine effects on lymphocyte CE.

RESULTS

Ninety-two apheresis events from patients with acute lymphocytic leukemia (ALL) (n = 28), chronic lymphocytic leukemia (n = 18), and non-Hodgkin lymphoma (n = 46) were available for analysis. Forty-one collections (45%) had a lymphocyte CE of <40%. On multivariable analysis, age (every 10-year increase, odds ratio [OR] = 1.51; p = 0.034), disease type (chronic lymphocytic leukemia vs. ALL, OR = 0.24; p = 0.052; non-Hodgkin lymphoma vs. ALL, OR = 0.20; p = 0.009) and precollection platelets (every 10 × 10³ /μL increase, OR = 1.07; p = 0.005) were appreciably associated with a lymphocyte CE of <40%. No major apheresis complications occurred.

CONCLUSIONS

Lymphocyte collection at our center was well tolerated and 100% successful in manufacturing CD19-directed CAR T cells from adult patients with B-cell malignancies despite low CE in some patients. A diagnosis of ALL, advancing age, and higher preapheresis platelet counts were observed to be associated with low CE.

Manufacturing chimeric antigen receptor T cells: issues and challenges

Clinical trials of adoptively transferred CD19 chimeric antigen receptor (CAR) T cells have delivered unprecedented responses in patients with relapsed refractory B-cell malignancy. These results have prompted Food and Drug Administration (FDA) approval of two CAR T-cell products in this high-risk patient population. The widening range of indications for CAR T-cell therapy and increasing patient numbers present a significant logistical challenge to manufacturers aiming for reproducible delivery systems for high-quality clinical CAR T-cell products. This review discusses current and novel CAR T-cell processing methodologies and the quality control systems needed to meet the increasing clinical demand for these exciting new therapies.

Low-Volume Leukapheresis in Non-Cytokine-Stimulated Donors for the Collection of Mononuclear Cells

Background

There is an increasing demand for products containing mononuclear cells (MNCs) for cellular immune therapy. Hence, leukapheresis is increasingly performed in healthy volunteer donors.

Methods

We evaluated 147 low-volume leukapheresis procedures from 77 healthy non-cytokine-stimulated donors. Complete blood counts (CBCs) of the donors were measured before and directly after the procedures as well as from the MNC products. Follow-up CBCs were collected from donors within 21 days.

Results

The product hematocrit within a range from 1.2 to 6.0% did not correlate with the collection efficiency of any cell population or the granulocyte and platelet yield. There was a strong correlation between the CBC values before leukapheresis and the cell yield of lymphocytes and monocytes as well as a perfect negative correlation between cell recruitment and cell loss in all cell populations. Furthermore, we observed a significant decrease in the CBC values in all cell populations directly after leukapheresis, which recovered within a mean of 16.1 days (SD ± 2.1 days) and even showed a significant increase in granulocytes and platelets.

Conclusion

Low-volume leukapheresis is feasible for the collection of MNCs in which the product hematocrit is negligible for the collection efficiency, cell yield, or contamination of residual cells under operational settings recommended by the manufacturer. Our data suggests that cell recruitment is regulated by the number of cells removed, which may also be the stimulus to induce granulo- and thrombopoiesis within the first days after leukapheresis.

Evolution of MNC and lymphocyte collection settings employing different Spectra Optia® Leukapheresis systems

BACKGROUND AND OBJECTIVES

The Spectra Optia^® continuous mononuclear cell (CMNC apheresis) system has emerged as the preferred device in peripheral blood stem cell collections over the original two-step Spectra Optia^® mononuclear cell (MNC apheresis) system. Until now, no comparative data were available for non-stimulated MNC collections that are required for immunotherapy.

MATERIALS AND METHODS

We compared collection parameters and product composition for Spectra Optia MNC- as well as CMNC-apheresis systems in non-stimulated MNC collections from 35 registry donors intended for donor lymphocyte infusions. In a subsequent analysis, different centrifugation forces (determined as packing factor or PF) were investigated regarding target cell yield and contamination in 61 collections using the CMNC device only.

RESULTS

Comparable collection efficiencies as well as target cell yields could be achieved with the Spectra Optia MNC- versus CMNC program. Similar numbers of MNC, T, B and NK cells could be collected with both devices. This led to a more than twofold lymphocyte recruitment from lymphatic tissue into the blood during apheresis. However, significantly more blood had to be processed with longer procedure time using the MNC program resulting in larger product volumes compared to the CMNC setting. Red blood cell and platelet (PLT) contamination were similar. Lowering the centrifugation force from PF4·5 to PF4·0 significantly reduced PLT contamination without affecting target cell yield in the product.

CONCLUSION

The Spectra Optia^® CMNC device using lower centrifugal force (PF4·0) showed similar target cell yield and composition as well as collection efficiencies with superior performance parameters and lower PLT contamination compared to the MNC setting.

Erythrocyte depletion from bone marrow: performance evaluation after 50 clinical-scale depletions with Spectra Optia BMC

BACKGROUND

Red blood cell (RBC) depletion is a standard graft manipulation technique for ABO-incompatible bone marrow (BM) transplants. The BM processing module for Spectra Optia, "BMC", was previously introduced. We here report the largest series to date of routine quality data after performing 50 clinical-scale RBC-depletions.

METHODS

Fifty successive RBC-depletions from autologous (n = 5) and allogeneic (n = 45) BM transplants were performed with the Spectra Optia BMC apheresis suite. Product quality was assessed before and after processing for volume, RBC and leukocyte content; RBC-depletion and stem cell (CD34+ cells) recovery was calculated there from. Clinical engraftment data were collected from 26/45 allogeneic recipients.

RESULTS

Median RBC removal was 98.2% (range 90.8-99.1%), median CD34+ cell recovery was 93.6%, minimum recovery being 72%, total product volume was reduced to 7.5% (range 4.7-23.0%). Products engrafted with expected probability and kinetics. Performance indicators were stable over time.

DISCUSSION

Spectra Optia BMC is a robust and efficient technology for RBC-depletion and volume reduction of BM, providing near-complete RBC removal and excellent CD34+ cell recovery.

Optimizing peripheral blood stem cells transplantation outcome through amend relapse and graft failure: a review of current literature

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been considered as a valuable approach in treatment of numerous malignant and none malignant hematologic disorders. However, relapse and poor graft function (PGF) after allo-SCT remain to be controversial issues which may affect the transplantation outcome. Relevant articles were searched in MEDLINE database (2000–2016) using keywords and phrases: donor lymphocyte infusions, allogeneic stem cells transplantation, relapsed hematologic malignancies, booster schedules, cell dose, laboratory monitoring protocols and technical aspects of apheresis. Relapse of disease and PGF could be reduced via noting some main points such as choosing the suitable time and patient for donor lymphocyte infusion (DLI) and also determination of patients who ought to candidate for second allogeneic HSCT or for the use of stem cell boost. DLI and stem cell booster are promising treatment strategies noted in this review. Finally, this paper discusses indications and technical aspects of DLI and stem cell booster in hematological malignancies and emphasizes their therapeutic or pre-emptive potentials.

A method for the quantification of 8-methoxypsoralen by mass spectrometry for offline extracorporeal photopheresis

An LC-MS/MS assay for analysis of 8-methoxypsoralene was developed as assay to monitor extracorporeal photopheresis. This allows quantification of 8-MOP adhering to plastic surface and of the UV light-dependent decay constant.

Donor lymphocyte infusion after allogeneic stem cell transplantation

Allogeneic stem cell transplantation (allo-SCT) is considered the cornerstone in the treatment of several malignant and not malignant hematological diseases. However, relapse of hematological disease after allo-SCT is considered the most challenging point in the field. The risk can be reduced through optimal patients, donor and disease selection before allo-SCT, but harnessing donor immune system is an appealing way to treat or avoid disease relapse. Donor lymphocyte infusion (DLI) is a simple and effective therapy after allo-SCT. In this paper, the efficacy of DLI will be analyzed in different hematological diseases, focusing also on their therapeutic or pre-emptive use.

CAR-T Cell Therapies From the Transfusion Medicine Perspective

The use of chimeric antigen receptor (CAR)-T cell therapy for the treatment of hematologic malignancies has generated significant excitement over the last several years. From a transfusion medicine perspective, the implementation of CAR-T therapy as a potential mainstay treatment for not only hematologic but also solid-organ malignancies represents a significant opportunity for growth and expansion. In this review, we will describe the rationale for the development of genetically redirected T cells as a cancer therapeutic, the different elements that are required to engineer these cells, as well as an overview of the process by which patient cells are harvested and processed to create and subsequently validate CAR-T cells. Finally, we will briefly describe some of the toxicities and clinical efficacy of CAR-T cells in the setting of patients with advanced malignancy.

Automation of cellular therapy product manufacturing: results of a split validation comparing CD34 selection of peripheral blood stem cell apheresis product with a semi-manual vs. an automatic procedure

Background

Automation of cell therapy manufacturing promises higher productivity of cell factories, more economical use of highly-trained (and costly) manufacturing staff, facilitation of processes requiring manufacturing steps at inconvenient hours, improved consistency of processing steps and other benefits. One of the most broadly disseminated engineered cell therapy products is immunomagnetically selected CD34+ hematopoietic “stem” cells (HSCs).

Methods

As the clinical GMP-compliant automat CliniMACS Prodigy is being programmed to perform ever more complex sequential manufacturing steps, we developed a CD34+ selection module for comparison with the standard semi-automatic CD34 “normal scale” selection process on CliniMACS Plus, applicable for 600 × 10⁶ target cells out of 60 × 10⁹ total cells. Three split-validation processings with healthy donor G-CSF-mobilized apheresis products were performed; feasibility, time consumption and product quality were assessed.

Results

All processes proceeded uneventfully. Prodigy runs took about 1 h longer than CliniMACS Plus runs, albeit with markedly less hands-on operator time and therefore also suitable for less experienced operators. Recovery of target cells was the same for both technologies. Although impurities, specifically T- and B-cells, were 5 ± 1.6-fold and 4 ± 0.4-fold higher in the Prodigy products (p = ns and p = 0.013 for T and B cell depletion, respectively), T cell contents per kg of a virtual recipient receiving 4 × 10⁶ CD34+ cells/kg was below 10 × 10³/kg even in the worst Prodigy product and thus more than fivefold below the specification of CD34+ selected mismatched-donor stem cell products. The products’ theoretical clinical usability is thus confirmed.

Conclusions

This split validation exercise of a relatively short and simple process exemplifies the potential of automatic cell manufacturing. Automation will further gain in attractiveness when applied to more complex processes, requiring frequent interventions or handling at unfavourable working hours, such as re-targeting of T-cells.

An alternative mini buffy coat preparation method for adult patients with extracorporeal photopheresis contraindications

BACKGROUND

Extracorporeal photopheresis (ECP) is an important cell-based therapy for various diseases but is limited to patients eligible for apheresis. We developed an alternative mini buffy coat (BC) preparation method using the Spectra Optia® apheresis system and compared its efficacy of white blood cell (WBC) recovery with the standard mini BC preparation method already established for pediatric patients.

METHODS

Whole blood (450 ± 45 mL) samples were collected from 30 randomly selected healthy volunteer blood donors and divided into two groups. In the first group, WBCs were separated with a fully automated separator device (Compomat G4^® ). In the second group, BCs were separated with the bone marrow processing program of the Spectra Optia apheresis system.

RESULTS

There were no significant differences in total leukocyte counts per product between the two groups. In contrast, lymphocyte counts per product were significantly higher (P < 0.001) in BCs separated from apheresis.

CONCLUSION

Our novel technique resulted in similar WBC yields but higher lymphocyte yields than the standard mini BC preparation method. This method can serve as an alternative to WBC collection in conventional ECP for adult patients with apheresis contraindications. J. Clin. Apheresis 32:12-15, 2017. © 2016 Wiley Periodicals, Inc.

Clinical-scale isolation of the total Aspergillus fumigatus-reactive T-helper cell repertoire for adoptive transfer

BACKGROUND AIMS

Evidence of the criticality of the adaptive immune response for controlling invasive aspergillosis has been provided. This observation is supported by the fact that invasive aspergillosis, a grave complication of allogeneic stem cell transplantation, occurs long after myeloid reconstitution in patients with low T-cell engraftment and/or on immunosuppressants. Adoptive T-cell transfer might be beneficial, but idiosyncrasies of Aspergillus fumigatus and the anti-Aspergillus immune response render established selection technologies ineffective.

METHODS

We developed a Good Manufacturing Practice (GMP)-compliant protocol for preparation of A. fumigatus-specific CD4+ cells by sequentially depleting regulatory and cytotoxic T cells, activating A. fumigatus-specific T-helper cells with GMP-grade A. fumigatus lysate, and immuno-magnetically isolating them via the transiently up-regulated activation marker, CD137.

RESULTS

In 13 full-scale runs, we demonstrate robustness and feasibility of the approach. From 2 × 10(9) peripheral blood mononuclear cells, we isolated 27 × 10(3)-318 × 10(3)Aspergillus-specific T-helper cells. Frequency among total T cells was increased, on average, by 200-fold. Specific studies indicate specificity and functionality: After non-specific in vitro expansion and re-stimulation with different antigens, we observed strong cytokine responses to A. fumigatus and some other fungi including Candida albicans, but none to unrelated antigens.

DISCUSSION

Our technology isolates naturally occurring Aspergillus-specific T-helper cells within 2 days of identifying the clinical indication. Rapid adoptive transfer of Aspergillus-specific T cells may be quite feasible; the clinical benefit remains to be demonstrated. A manufacturing license as an advanced-therapy medicinal product was received and a clinical trial in post-transplantation invasive aspergillosis patients approved. The product is dosed at 5 × 10E3/kg T cells (single intravenous injection), of which at least 10% must be A. fumigatus-specific.

Automated isolation of primary antigen-specific T cells from donor lymphocyte concentrates: results of a feasibility exercise

BACKGROUND

The safety and clinical efficacy of adoptive transfer of prospectively isolated antigen-specific T cells are well established. Several competing selection methods are available, one of which is based on immunomagnetic enrichment of T cells secreting IFNγ after incubation with the relevant antigen. The proprietary, GMP-conforming selection technology, called 'cytokine capture system' (CCS) is established in many laboratories for the CliniMACS Plus system. It is robust and efficient, but labour-intensive and incompatible with a single-shift working schedule. An automatic immunomagnetic cell processing system, CliniMACS Prodigy ('Prodigy'), including a protocol for fully automatic CCS execution was recently released.

MATERIAL AND METHODS

Feasibility of clinical-scale CMV-specific T-cell selection using Prodigy was evaluated using leukoapheresis products from five healthy CMV sero-positive volunteers. Clinical reagents and consumables were used throughout.

RESULTS

The process required no operator input beyond set-up and QC-sample collection, that is, feasibility was given. An IFNγ-secreting target T-cell population was detectable after stimulation, and >2 log-scale relative depletion of not CMV-reactive T cells in the target population was achieved. Purity, that is the frequency of CMV-reactive T cells among all CD3(+) cells ranged between 64 and 93%.

CONCLUSION

The CCS protocol on Prodigy is unrestrictedly functional. It runs fully automatically beyond set-up and thus markedly reduces labour. The quality of the products generated is similar to products generated with CliniMACS Plus. The automatic system is thus suitable for routine clinical application.

Red blood cell depletion from bone marrow and peripheral blood buffy coat: a comparison of two new and three established technologies

BACKGROUND

Red blood cell (RBC) depletion is a standard technique for preparation of ABO-incompatible bone marrow transplants (BMTs). Density centrifugation or apheresis are used successfully at clinical scale. The advent of a bone marrow (BM) processing module for the Spectra Optia (Terumo BCT) provided the initiative to formally compare our standard technology, the COBE2991 (Ficoll, manual, "C") with the Spectra Optia BMP (apheresis, semiautomatic, "O"), the Sepax II NeatCell (Ficoll, automatic, "S"), the Miltenyi CliniMACS Prodigy density gradient separation system (Ficoll, automatic, "P"), and manual Ficoll ("M"). C and O handle larger product volumes than S, P, and M.

STUDY DESIGN AND METHODS

Technologies were assessed for RBC depletion, target cell (mononuclear cells [MNCs] for buffy coats [BCs], CD34+ cells for BM) recovery, and cost/labor. BC pools were simultaneously purged with C, O, S, and P; five to 18 BM samples were sequentially processed with C, O, S, and M.

RESULTS

Mean RBC removal with C was 97% (BCs) or 92% (BM). From both products, O removed 97%, and P, S, and M removed 99% of RBCs. MNC recovery from BC (98% C, 97% O, 65% P, 74% S) or CD34+ cell recovery from BM (92% C, 90% O, 67% S, 70% M) were best with C and O. Polymorphonuclear cells (PMNs) were depleted from BCs by P, S, and C, while O recovered 50% of PMNs. Time savings compared to C or M for all tested technologies are considerable.

CONCLUSION

All methods are in principle suitable and can be selected based on sample volume, available technology, and desired product specifications beyond RBC depletion and MNC and/or CD34+ cell recovery.

Leukocytapheresis for the treatment of hyperleukocytosis secondary to acute leukemia

Patients presenting with new or recurrent acute leukemia, particularly of the myeloid lineage, with WBC counts exceeding 100 × 109/L are often considered for leukocytapheresis, especially if they are experiencing symptoms of leukostasis. These symptoms are thought to occur because of blast aggregates and WBC thrombi in the circulation, which reduce blood flow. Leukostasis may cause various complications, including hyperviscosity syndrome, vascular occlusion resulting in intracranial hemorrhages and respiratory failure, and perivascular leukemic infiltrates. Leukostasis occurs more commonly with a high WBC count and with leukemias of monocytoid lineage such as acute myelomonocytic leukemia, which is a reflection of the nature of the leukemic blasts. Leukocytapheresis is used in an effort to quickly decrease a patient's circulating blast count, which can both prevent the development of leukostasis and provide symptomatic relief of leukostasis. However, the impact of leukocytapheresis on early- and long-term mortality is controversial, with several studies producing conflicting results. In this chapter, the pathophysiology of leukostasis, performance of leukocytapheresis, and efficacy of this treatment are reviewed.