Isolation of CD34+ progenitor cells from peripheral blood by use of an automated immunomagnetic selection system: factors affecting the results

Gene therapies for transfusion dependent β-thalassemia: Current status and critical criteria for success

Thalassemia is one of the most prevalent monogenic diseases usually caused by quantitative defects in the production of β-globin leading to severe anemia. Technological advances in genome sequencing, stem cell selection, viral vector development, transduction and gene editing strategies now allow for efficient exvivo genetic manipulation of human stem cells that can lead to production of hemoglobin, leading to a meaningful clinical benefit in thalassemia patients. In this review, the status of the gene-therapy approaches available for transfusion dependent thalassemia are discussed, along with the critical criteria that affect efficacy and lessons that have been learned from the early phase clinical trials. Salient steps necessary for the clinical development, manufacturing, and regulatory approvals of gene therapies for thalassemia are also highlighted, so that the potential of these therapies can be realized. It is highly anticipated that gene therapies will soon become a treatment option for patients lacking compatible donors for hematopoietic stem cell transplant and will offer an alternative for definitive treatment of β-thalassemia.

Chemistry, manufacturing and controls for gene modified hematopoietic stem cells

Gene modification of hematopoietic stem cells is increasingly becoming popular as a therapeutic approach, given the recent approvals and the number of new applications for clinical trials targeting monogenetic and immunodeficiency disorders. Technological advances in stem cell selection, culture, transduction and gene editing now allow for efficient ex vivo genetic manipulation of stem cells. Gene-addition techniques using viral vectors (mainly retrovirus- and lentivirus-based) and gene editing using various targeted nuclease platforms (e.g., Zinc finger, TALEN and Crispr/Cas9) are being applied to the treatment of multiple genetic and immunodeficiency disorders. Herein, the current state of the art in manufacturing and critical assays that are required for ex vivo manipulation of stem cells are addressed. Important quality control and safety assays that need to be planned early in the process development phase of these products for regulatory approval are also highlighted.

The prognostic impact of peripheral blood progenitor cell dose following high-dose therapy and autologous stem cell transplant for hematologic malignancies

High-dose chemotherapy (HDT) followed by autologous peripheral blood progenitor cell transplant (PBPCT) has become a standard intervention in certain clinical settings of hematologic malignancies, particularly multiple myeloma and relapsed/refractory lymphoma. While the minimal required PBPCs infused, as defined by number of CD34 + cells, has been relatively well delineated for adequate hematopoietic recovery post-HDT, optimal PBPC dose has not been clearly defined. This is particularly relevant in the context of retrospective data suggesting improved survival outcomes with increased PBPC doses. The potential confounding of these data as they relate to disease risk is discussed within this review. Additionally, other retrospective data have suggested that enhanced quantitative lymphocyte subset reconstitution post-HDT-PBPCT may confer progression-free and overall survival advantage. These reported series herein reviewed may inform discussion of future, prospective clinical trials with the intent of defining optimal autologous PBPC dose following HDT, especially as it may relate to metrics beyond hematopoietic recovery.

THERMOSENSITIVE NANOPARTICLES CONJUGATING WITH CD34 ANTIBODY AND ITS SOLUTION PEROPERTIES

Poly N-isopropylacrylamide (PNIPAAm) is a well-known temperature-sensitive polymer. When the temperature is higher than the lower critical solution temperature (LCST), PNIPAAm aquous solution is cloudy (phase separation occurred). In contrast, when the temperature is lower than the LCST, PNIPAAm is soluble in water (a homogeneous solution). The lower critical solution temperature (LCST) in aqueous solution of PNIPAAm was about 32~33°C. We prepared nano-scaled PNIPAAm particles containing carboxylic group on their surfaces by introducing acrylic acid monomer. The carboxylic groups were applied to conjugate with the amino group of the CD34 antibody. This immuno-conjugate can be applied on targeting the human CD34 positive cells, peripheral blood progenitor cells included, for cell purification and drug controlled release. In order to the active responding of controlled release of the conjugate in the body influenced by temperature, we hope to estimate the shifting of the gel-collapse temperature or cloud point of the immuno-conjugates by dynamic light scattering (DLS) and UV absorption. The results show that the gel-collapse temperature of the nano-particle was not significantly affected by the content of AA between 1.5~5 mol%. However, cloud point of the solution was elevated by the conjugation of CD34 antibody to 37°C. When CD34-conjugated particle was subsequently incorporated with recombinant FLT3-ligand, which is a smaller molecule compare to CD34 antibody, cloud point of the solution was not affected.

Challenges in cardiac tissue engineering

Cardiac tissue engineering aims to create functional tissue constructs that can reestablish the structure and function of injured myocardium. Engineered constructs can also serve as high-fidelity models for studies of cardiac development and disease. In a general case, the biological potential of the cell-the actual "tissue engineer"-is mobilized by providing highly controllable three-dimensional environments that can mediate cell differentiation and functional assembly. For cardiac regeneration, some of the key requirements that need to be met are the selection of a human cell source, establishment of cardiac tissue matrix, electromechanical cell coupling, robust and stable contractile function, and functional vascularization. We review here the potential and challenges of cardiac tissue engineering for developing therapies that could prevent or reverse heart failure.

Viral purging of haematological autografts: should we sneeze on the graft?

High-dose cytotoxic chemotherapy followed by autologous haematopoietic stem cell transplantation (ASCT) is extensively used for the treatment of many haematopoietic, as well as several epithelial cancers. Disease relapse may be the result of tumour contamination within autograft as evidenced by gene marking studies. The multiple purging strategies that have been described to date have not proven effective in most ASCT settings. This review addresses the possibility of using oncolytic viruses as a novel purging strategy. DNA viruses such as genetically engineered adenoviral vectors have widely been used to deliver either a prodrug-activating enzyme or express wild-type p53 selectively in tumour cells in ex vivo purging protocols. In addition, conditionally replicating adenoviruses that selectively replicate in tumour cells and herpes simplex virus type 1 are other DNA viruses that have been tested as ex vivo purging agents under laboratory conditions. Vesicular stomatitis virus (VSV) and reovirus are naturally occurring RNA viruses that appear to hold promise as purging agents under ex vivo and in vivo settings. Preclinical data demonstrate reovirus's purging potential against breast, monocytic and myeloma cell lines as well as patient-derived tumours of diffuse large B-cell lymphoma, chronic lymphocytic leukaemia, Waldenstrom macroglobulinemia and small lymphocytic lymphoma. In addition, VSV has shown effective killing of leukaemic cell lines and multiple myeloma patient specimens. Given the increasing interest in the utilization of viruses as purging agents, the following review provides a timely summary of the potential and the challenges of oncolytic viruses as purging modalities during ASCT.

Intermittent exposure of primitive quiescent chronic myeloid leukemia cells to granulocyte-colony stimulating factor in vitro promotes their elimination by imatinib mesylate

PURPOSE

Primitive quiescent chronic myeloid leukemia (CML) cells are biologically resistant to imatinib mesylate, an inhibitor of the p210(BCR-ABL) kinase. The present study was designed to investigate whether either continuous or intermittent exposure of these cells to granulocyte-colony stimulating factor (G-CSF) in vitro can overcome this limitation to the effectiveness of imatinib mesylate therapy.

EXPERIMENTAL DESIGN

CD34(+) leukemic cells were isolated from six newly diagnosed chronic phase CML patients and cultured for 12 days in serum-free medium with or without G-CSF and/or imatinib mesylate present either continuously or intermittently (three cycles of G-CSF for 0, 1, or 4 days +/- imatinib mesylate for 0, 3, or 4 days). Every 4 days, the number of residual undivided viable cells and the total number of viable cells present were measured.

RESULTS

Intermittent but not continuous exposure to G-CSF significantly accelerated the disappearance in vitro of initially quiescent CD34(+) CML cells. This resulted in 3- and 5-fold fewer of these cells remaining after 8 and 12 days, respectively, relative to continuous imatinib mesylate alone (P < 0.04). Cultures containing imatinib mesylate and intermittently added G-CSF also showed the greatest reduction in the total number of cells present after 12 days (5-fold more than imatinib mesylate alone).

CONCLUSION

Intermittent exposure to G-CSF can enhance the effect of imatinib mesylate on CML cells by specifically targeting the primitive quiescent leukemic elements. A protocol for treating chronic-phase CML patients with imatinib mesylate that incorporates intermittent G-CSF exposure may offer a novel strategy for obtaining improved responses in vivo.

Cryopreservation of hematopoietic progenitor cells from apheresis at high cell concentrations does not impair the hematopoietic recovery after transplantation

BACKGROUND

The high number of nuclear cells (NCs) from hematopoietic progenitor cells-apheresis (HPC-A) requires cryopreservation in large volumes or at high NC concentrations. The effect of NC concentration during cryopreservation has yet to be examined.

STUDY DESIGN AND METHODS

In the experimental arm (n = 610, Protocol B), the first HPC-A sample from the patient was cryopreserved in two cryobags and subsequent collections in one cryobag, resulting in high NC concentrations (>100 x 10(6) NCs/mL) in most cases. The effect of NC concentrations at freezing in NC recovery after thawing and engraftment kinetics was analyzed and compared with a group of HPC-A cryopreserved at standard NC concentrations (n = 455, Protocol A).

RESULTS

The mean (SD) NC concentration at freezing was 78 (28) x 10(6) per mL (median, 82 x 10(6)/mL; range, 12 x 10(6)-156 x 10(6)/mL) and 183 (108) x 10(6) per mL (median, 156 x 10(6)/mL; range, 16 x 10(6)-678 x 10(6)/mL), for HPC-A cryopreserved according to Protocols A and B, respectively. The NC viabilities of the test vials and HPC-A components after thawing were 88 percent versus 85 percent and 85 percent versus 82 percent, and the cloning efficiency was 49 percent versus 33 percent for Protocols A and B, respectively (p < 0.001). Significant differences were not observed in the recovery of NCs. Days to neutrophil and platelet engraftment were not different between patients transplanted in the standard- (n = 143) or high-cell-concentration group (n = 238).

CONCLUSION

The cryopreservation of HPC-A at higher than standard NC concentrations has no adverse impact on hematopoietic reconstitution after transplantation.

Impact of leukapheresis cell composition on immunomagnetic cell selection with the Baxter Isolex 300i device: a statistical analysis

Immunomagnetic cell selection (ICS) of CD34(+) cells is increasingly adopted in allogeneic and autologous transplant settings. Because many variables can affect the final results of ICS, we focused our study toward the influence exerted by the leukapheresis (LKF) cell composition on recovery, purity, and log of T and B depletion of the immunoselected cells. A total of 39 consecutive CD34(+) ICS were performed with the Isolex 300i (Baxter) device on 39 LKF from 9 HLA haploidentical donors and 20 patients. Flow cytometric analysis was performed both on the leukapheresis content and on the immunoselected cells. The statistical analysis was performed utilizing the Pearson's correlation test and the Mann-Whitney U test. The median purity and recovery of the immunoselected CD34(+) cells were 95.3% (IR: 93.0-99.0) and 55.1% (IR: 41.8-68.2), respectively. The median log of T and B depletion were 3.87 (IR: 3.5-4.3) and 2.9 (IR: 2.5-3.5), respectively. Our data indicate that not only the CD34(+) cell load but also the ratio among the cells belonging to the starting fraction can influence the results of ICS. LKF collection protocols have to be addressed to collect an high number of CD34(+) cells (>500 x 10(6)) without taking care of the contaminating cells when the Baxter Isolex 300i device is employed.

Real-time process/quality control for HPC processing

BACKGROUND

JACIE Standards (FACT Standards in the USA) have been implemented in Europe since 1999. An on-site accreditation inspection took place at our center in January 2004. The purpose of this work was to develop a real-time process/quality control system meeting the JACIE Standards for HPC release.

METHODS

Data from 194 HPC processing procedures for autologous transplantation performed over a 5-year period were analyzed. The results of different processing methods applied at our facility were compared: (1) cryopreservation without washing cells (n=50), (2) washing cells (n=87), (3) cell-density separation (n=12) and (4) positive CD34 selection (n=45).

RESULTS

Four critical control points were set for the validation of HPC processing: (a) number of lost CD34(+) cells during processing, (b) contamination, (c) viability of the cells after thawing and (d) ability to reconstitute hematopoiesis after transplantation. On the basis of statistical analysis, ranges of acceptable values were defined for each critical control point and for each processing method. Those acceptable values were used for cell release and real-time quality control.

DISCUSSION

This study describes a model for the validation of HPC processing and for a real-time process/quality control system for HPC release. Optimization of processing techniques, standardization of methods and comparison between facilities will open the way towards external quality controls and quality improvement.

Allogeneic peripheral blood stem cell transplantation from two- or three-loci-mismatched related donors in adult Japanese patients with high-risk hematologic malignancies

With the increasing frequency of haploidentical transplantation, it is becoming more important to establish the degree of HLA mismatch that can be accepted. We retrospectively analyzed clinical data of 50 adult Japanese patients with high-risk hematologic malignancies who underwent allogeneic peripheral blood stem cell transplantation (PBSCT) from two- or three-loci-mismatched related donors with HLA class I and II gene disparities in the graft-versus-host direction. They were treated at 20 transplant centers between 1996 and 2002. In all, 18 patients received unmanipulated PBSC, while 32 received purified CD34+ blood cells. Conventional (n=31) or reduced-intensity (n=19) conditioning regimens were used. Of the 39 patients (78%) who survived for > or =28 days after transplant, 37 (95%) achieved neutrophil engraftment, while graft failure and rejection occurred in two of 39 (5%) and three of 37 (8%) patients, respectively. Stepwise Cox regression analysis revealed a significantly lower incidence of grades II-IV acute GVHD in patients receiving purified CD34+ cells (hazard ratio 0.32; 95% CI 0.12-0.84; P=0.022). By 1 year post transplant, 28 patients (56%) had died of transplant-related problems, including infectious complications (30%). Although the number of patients is small, our data suggest that transplant-related problems, particularly infectious complications, are major obstacles to the success of this therapy.

Strategies to reduce transplant-related mortality after allogeneic stem cell transplantation in elderly patients: Comparison of reduced-intensity conditioning and unmanipulated peripheral blood stem cells vs a myeloablative regimen and CD34+ cell selection

OBJECTIVES

The aim of this study was to compare two approaches used to reduce transplant-related mortality (TRM) after allogeneic peripheral blood stem cell transplantation (allo-PBSCT) in elderly patients.

PATIENTS AND METHODS

Data from 50 patients, 45 years of age or older, consecutively treated with an HLA-identical sibling allo-PBSCT at the Hospital de Sant Pau were analyzed. We have compared the outcome of patients treated with conventional myeloablative regimens and CD34(+)-selected cells (CD34(+) group; n=23) with those receiving reduced-intensity conditioning regimens, consisting of fludarabine (150 mg/m(2)) plus an alkylating agent, followed by unmanipulated grafts (RIC group; n=27). Patient characteristics were well balanced between the two groups, although patients in the RIC group were slightly older.

RESULTS

The incidence of acute graft-vs-host disease (GVHD) was similar in both groups. The 1-year cumulative incidence of extensive chronic GVHD was 38% in the RIC group and 17% in the CD34(+) group (p=0.2). After a median follow-up of 28 months, there were no differences in the relapse rate. Patients in the RIC group had a lower TRM, with a cumulative incidence of 7% vs 30% at 6 months and 15% vs 39% at 1 year (p=0.05). The Kaplan-Meier estimates of PFS at 2 years was 67% in the RIC group and 43% in the CD34(+) group (p=0.09) and the OS was 69% vs 43% (p=0.05), respectively.

CONCLUSION

CD34(+) cell selection reduced the risk of extensive cGVHD but was associated with a higher TRM. Although the number of patients is limited, our study suggests that this approach should be restricted to relatively young patients, as better outcomes can be achieved in elderly patients using RIC strategies.

Isolex 300i CD34-selected cells to support multiple cycles of high-dose therapy

BACKGROUND

We have previously reported that repeated cycles of high-dose therapy (HDT), can be supported by unmanipulated autologous PBPC. Here we investigate whether purified CD34+ cells, obtained by immunomagnetic separation using the Isolex 300i device, can support such therapy.

METHODS

Twenty-nine consecutive patients with metastatic breast cancer had PBPC mobilized and harvested following chemotherapy and G-CSF (10 microg/kg per day). Patients with > 4.0 x 10(6)/kg CD34+ cells in the apheresis product underwent CD34-selection using the Isolex 300i (v2.0) device. All cells collected were equally divided into three aliquots and cryopreserved. Patients who did not achieve this threshold had unmanipulated cells collected and stored. Patients subsequently received three cycles of HDT with paclitaxel (175 mg/m2), thiotepa (300 mg/m2) and either ifosfamide (10 g/m2) or cyclophosphamide (4 g/m2). It was intended for patients to receive CD34-selected cells to support each of the three cycles of HDT (i.e 1/3 for each cycle) and to compare hemopoietic recovery between patients receiving CD34-selected cells or unmanipulated cells.

RESULTS

Thirteen of the 29 patients (45%) did not mobilize sufficient CD34+ cells to undergo CD34-selection. The remaining 16 patients underwent CD34-selection with a median purity of 84.3% (range: 16.3-96.1%) and yield of 34% (range: 1-60%). Fifteen of these patients proceeded to HDT and 42 of the planned 45 cycles were administered. Nine patients had all three HDT cycles supported by CD34-selected cells. The median number of CD34-selected cells (x 10(6)/kg) infused per cycle was 1.5 (range: 0.04-3.01). Three of the 15 patients required infusion of 'back-up' unmanipulated cells because of delayed neutrophil recovery. Of the 13 patients whose PBPCs did not undergo CD34+ cell selection, 11 proceeded to HDT with a median of 3.2 x 10(6)/kg (range: 2.0-4.4) unselected cells infused per cycle and 31 of 33 planned cycles were delivered. When hemopoietic recovery was compared between cycles of HDT supported by CD34-selected (n = 34) and unmanipulated cells (n = 31), there was a modest slowing in the patients receiving CD34-selected cells; time to ANC > 1.0 x 10(9)/L = 11 days versus 10 days (P = 0.0122) and platelets > 20 x 10(9)/L = 14 days versus 13 days (P = 0.0009). No difference in recovery to 50 x 10(9)/L was observed (P = 0.54).

CONCLUSION

We have demonstrated that Isolex 300i CD34-selected cells are capable of supporting multiple cycles of HDT. However, we were unable to acquire sufficient CD34+ cells to perform this processing in 45% (13/29) of patients and further improvements in yield are required to overcome the modest delay in neutrophil and platelet recovery.

CD34+-enriched peripheral blood progenitor cells from unrelated donors for allografting of adult patients: high risk of graft failure, infection and relapse despite donor lymphocyte add-back

Fifty-one adults with haematological malignancies were transplanted with CD34+-selected peripheral blood progenitor cells (PBPC) from unrelated donors. The conditioning protocol contained total body irradiation (n = 17) or combinations of busulphan and other alkylating agents (n = 34). Antithymocyte globulin was infused in all patients. The median number of CD3+ T cells infused with the graft after purification with the Isolex 300 system in the first cohort of 18 patients was 2.1 x 10(5)/kg. Prophylactic donor lymphocyte infusion (DLI) containing 1 x 10(5) CD3+ T cells was performed on d 21 in the following 33 patients who had received PBPC purified by the CliniMACS system. Early graft failure occurred in 8/51 patients (16%). After a median follow-up of 31 months (range 8-60), the probability of disease-free survival (DFS) was 36% for the whole group. Reasons for death were opportunistic infections (n = 15), graft-versus-host disease (GvHD, n = 7) and relapse (n = 4). Pre-transplant factors with significant impact on DFS were cytomegalovirus status and risk category of underlying disease. The occurrence of graft failure or GvHD was associated with poor outcome. Recipients of CD34+-selected PBPC from unrelated donors are at high risk of infectious complications, relapse and graft failure which cannot be prevented by early reinfusion of unmodified donor lymphocytes.

Variable product purity and functional capacity after CD34 selection: a direct comparison of the CliniMACS (v2.1) and Isolex 300i (v2.5) clinical scale devices

The two clinical scale devices currently available for CD34+ cell selection from peripheral blood stem cells (PBSC) apheresis products, the CliniMACS and the Isolex 300i, were compared directly by pooling and splitting two PBSC harvests collected on sequential days from 10 patients and processing half of each pooled harvest on each device. The CliniMACS product had significantly higher median CD34+ purity (90%vs 78%; P = 0.004) and lower median T-cell content (0.06%vs 0.44%; P = 0.003) compared with the Isolex 300i product. The median CD34+ yields were similar (64% and 60% respectively). However, when the functional capacities of the products were compared, the median recovery of colony-forming units was significantly greater from the Isolex 300i product (48%vs 38%; P = 0.035), as was expansion of cells in either erythroid or granulocytic lineage-specific liquid culture (2.1-fold more erythroid and 1.5-fold more granulocytic lineage progenitors on d 9 (P = 0.03 and 0.03 respectively). This was due to a higher proportion of apoptotic cells in the CliniMACS product (28%vs 18%; P = 0.007, annexin V binding). Hence, although the CliniMACS device yielded a higher purity product with fewer T cells, the Isolex 300i product contained fewer apoptotic cells and consequently had greater functional capacity in culture.

CD34+-enriched-CD19+-depleted autologous peripheral blood stem cell transplantation for chronic lymphoproliferative disorders: high purging efficiency but increased risk of severe infections

OBJECTIVE

The main objective of this work was to decrease the incidence of relapse after autologous stem cell transplantation with a "double purging" procedure.

METHODS

We used a "positive" (CD34) and "negative" (CD19) double selection method to improve the efficacy of "single purging" of hematopoietic harvests in poor-prognosis lymphoproliferative disorders. All patients included in the study had a positive molecular marker of their disease. Minimal residual disease (MRD) was studied by flow cytometry and PCR techniques during the purging procedure and after transplantation.

RESULTS

Twenty-six patients fulfilled entry criteria. Median age of patients was 50 years (range: 33-66); 17 were male and 9 female. Thirteen (50%) of the patients mobilized an adequate number of CD34+ cells (>or=3 x 10(6)/kg) to proceed with the double-selection protocol. Twelve of the 13 harvests became PCR negative after purging. Ten patients were grafted with the selected products and all but one engrafted without delay. After a median follow-up of 30 months, 2 of 10 patients suffered a molecular relapse at 7 and 19 months respectively. The earlier relapse was observed in the patient who received a MRD+ product. Only one patient experienced a clinical relapse. Three patients died due to obliterans bronchiolitis, pneumococcal sepsis, and septic shock of unknown origin, respectively, and three others presented life-threatening infections.

CONCLUSION

Therefore, CD34+/CD19+ positive/negative selection is an effective purging approach in patients with chronic lymphoproliferative disorders. This favorable effect is, however, counterbalanced by the high frequency of life-threatening infections.

Combined isolation of CD34+ progenitor cells and reduction of B cells from peripheral blood by use of immunomagnetic methods

BACKGROUND

Malignant cells may contribute to relapse after autologous hematopoietic cell transplantation The effectiveness of a double immunomagnetic purging strategy combining CD34-positive with B-negative cell selection to purge peripheral blood progenitor cells (PBPCs) from patients with chronic lymphoproliferative disorders has been analyzed.

STUDY DESIGN AND METHODS

Twenty-two CD34+ cell selections from patients with follicular lymphoma (n = 14), chronic lymphocytic leukemia (n = 6), mantle cell lymphoma (n = 1), and splenic marginal zone lymphoma (n = 1) were performed by use of a magnetic cell selector followed by a negative cell selection step with anti-CD19 monoclonal antibody bound to immunomagnetic beads.

RESULTS

The PBPC components contained median CD34+ cells of 1.24 percent (range, 0.38-3.92%) and CD19+ cells of 1.83 percent (range, 0.06-69.7%). After positive selection (n = 22), 49 percent (range, 16-72%) of CD34+ cells were recovered with a purity of 93 percent (range, 24-99%). The double-positive and -negative selections (n = 20) yielded 57.5 percent of CD34+ cells (range, 33.4-79.4%) with a purity of 95 percent (range, 63-99%). Logarithms of B-cell reduction in the CD34+-cell-enriched B-cell-depleted component had a median value of 3.63 (range, 2.74-4.84 log) and CD19+ and CD5+ cells for chronic lymphocytic leukemia patients with more than 4.56 log (>3.6-5.6 log). Of 13 PBPC components that had a tumor-specific clonal signal, 10 became PCR negative after the double-selection procedure.

CONCLUSION

Combined positive and negative magnetic cell selection achieves a high grade of tumor cell reduction with up to 77 percent of the grafts being negative for tumor-specific clonal signal by PCR analysis. This technique preserves an adequate recovery of progenitor cells able to engraft.

Combined positive and negative cell selection from allogeneic peripheral blood progenitor cells (PBPC) by use of immunomagnetic methods

Twenty-four mobilized peripheral blood products from healthy donors for allogeneic transplantation were positively selected for CD34(+) cells and depleted of CD4(+) and CD8(+) cells (+/- selection) by combining clinical grade immunomagnetic methods. A sequential, "two-step" strategy combining positive selection of CD34(+) cells by use of the Isolex 300i (versions 1 and 2) device and T cell depletion (TCD) using the MaxSep device and a simultaneous, "one-step" method of CD34(+)cell selection and TCD using the Isolex 300i (software versions 1 and 2) have been investigated. Using these magnetic bead separation systems, two groups of sequential +/- selection (Isolex 300i version 1/MaxSep and Isolex 300i version 2/MaxSep) and two groups of simultaneous +/- selection (Isolex 300i versions 1 and 2) were analysed. In the sequential +/- selection, logarithms of TCD (CD3(+) cell depletion) obtained by the positive selection step had median values of 3.7 with the version 1 (n = 5) and 4.5 with version 2 software of the Isolex 300i (n = 5) (P = 0.07). Version 2 also gave a higher CD34(+) cell purity and yield than did version 1 (92% vs77%, P < 0.05 and 55% vs 34%, P = 0.3, respectively). Additional TCD obtained in the second step with the MaxSep device for the two groups had a median value of 0.9 log and 7% CD34(+)cell losses. In the simultaneous +/- selection, the Isolex 300i version 2 (n = 10) gave a median TCD of 5.1 log and version 1 (n = 4) of 4 log (P < 0.005). Higher CD34(+)cell purity and yield were also obtained with version 2 than with version 1 (97% and 76%, P < 0.005 and 57% and 39%, P = 0.07, respectively). These data indicate that simultaneous, "one-step" +/- selection in the Isolex 300i version 2 achieves a high TCD with a high CD34(+) cell purity and an acceptable CD34(+) cell yield.

Kinetics of PBPC mobilization by cyclophosphamide, as compared with that by epirubicin/paclitaxel followed by G-CSF support: implications for optimal timing of PBPC harvest

BACKGROUND

Limited information is available on the mobilization kinetics of autologous PBPCs after induction with various chemotherapy regimens. With PBPC mobilization in patients with breast cancer used as a model for chemotherapy-induced PBPC recruitment, the kinetics of progenitor cells mobilized either with cyclophosphamide (CY) or epirubicin/paclitaxel (EPI-TAX) followed by the administration of G-CSF was compared.

STUDY DESIGN AND METHODS

The study included a total of 86 patients with breast cancer (stage II-IV) receiving either CY (n = 39) or EPI-TAX (n = 47), both followed by G-CSF support. The progenitor cell content in peripheral blood and apheresis components was monitored by flow cytometric enumeration of CD34+ cells. PBPC collection was started when the threshold of >20 x 10(6) CD34+ cells per L of peripheral blood was reached.

RESULTS

The PBPC collection was begun a median of 9 days after the administration of EPI-TAX followed by G-CSF support, as compared to a median of 13 days after mobilization with CY plus G-CSF. After treatment with CY, the total numbers of PBPCs peaked on Day 1 of apheresis, and they rapidly declined thereafter. In contrast, treatment with EPI-TAX followed by G-CSF administration led to a steady mobilization of CD34+ cells during leukapheresis. The difference in the mobilization patterns with CY and EPI-TAX resulted in a greater yield of CD34+ cells per L of processed blood volume. Compared to EPI-TAX, mobilization with CY required the overall processing of 30 percent less whole-blood volume to reach the target yield of > or = 10 x 10(6) CD34+ cells per kg of body weight. After a median of three apheresis procedures, however, both CY+G-CSF and EPI-TAX+G-CSF were equally effective in obtaining this target yield.

CONCLUSION

These results imply that specific PBPC mobilization as part of a given chemotherapy regimen should be taken into consideration before the planning of a PBPC harvest.

A prospective study of positive/negative ex vivo B-cell depletion in patients with chronic lymphocytic leukemia

OBJECTIVE

Autologous peripheral blood stem cell (PBSC) transplantation is increasingly being used in patients with chronic lymphocytic leukemia (CLL). As the autografts are frequently contaminated with large numbers of tumor cells, we have prospectively investigated the feasibility and efficacy of ex vivo double purging of PBSC grafts in an open, nonrandomized, single-center phase I/II clinical study.

MATERIALS AND METHODS

Twenty consecutive patients with poor-risk CLL underwent uniform stem cell mobilization with chemotherapy and granulocyte colony-stimulating factor (G-CSF). Double B-cell depletion of the harvested PBSC products was performed using immunomagnetic CD34(+) cell selection (Isolex300i Nexell, Irvine, CA) followed by a negative step with anti-CD19/20/23/37-labeled immunomagnetic beads. The purified PBSC were reinfused after myeloablative treatment with TBI/CY.

RESULTS

A total of 25 separation runs was accomplished using collection products containing 3.4% (1.1-8.1) CD34(+) cells and 1.2% (0.1-42) CD19(+)CD5(+) CLL cells. After double selection, 33% (15-67) CD34(+) cells were recovered with a purity of 98.8% (89.1-99. 8). CLL cells were undetectable by high-resolution flow cytometry in 15 of 25 final products; median purging efficacy was 5 (4.1-6) log. The CD34(+) content of the 20 final grafts was 4.6 (2.2-6.5) x 10(6)/kg. Rapid and durable engraftment developed in all cases. With a median follow-up of 20 (6-29) months, 17 patients live in complete clinical remission, two have recurrent disease, and one patient died due to pulmonary embolism five months after transplant. Persistence of the leukemic clone on the molecular level was demonstrated by dot blotting with clone-specific CDR3 probes in an additional five patients. Serious or unexpected infectious complications did not occur.

CONCLUSIONS

Positive/negative purging with the Isolex system allows preparation of highly purified CD34(+) fractions and up to six log of tumor cell depletion in patients with B-CLL and can be safety reinfused after myeloablative therapy without affecting hematopoietic engraftment.

Direct immunomagnetic method for CD34+ cell selection from cryopreserved cord blood grafts for ex vivo expansion protocols

BACKGROUND

Cord blood is a useful source of HPCs for allogeneic transplantation. HPC ex vivo expansion of a cord blood graft has been proposed as a way to increase the speed of engraftment and thus to reduce the occurrence of transplantation-related complications.

OBJECTIVE

The purpose of this study was to optimize a method for CD34+ cell selection of thawed cord blood grafts under clinical grade conditions, intended for application in a static, serum-free expansion culture.

MATERIAL AND METHODS

Twelve samples were thawed and washed with dextran, albumin, and rHu-deoxyribo-nuclease I (RHu-DNase) to avoid clumping. CD34+ cells were selected by using a sensitized immunomagnetic bead and 9C5 MoAb complex. A buffer containing rHu-DNase, citrate, albumin, and immunoglobulin in PBS was used during the procedure. CD34+ cells were eluted and detached by using an immunomagnetic cell selection device. Cells from the enriched fraction were cultured for 6 days in serum-free medium supplemented with rHu-SCF, rHu-IL-3, rHu fetal liver tyrosine kinase 3 ligand, and rHu thrombopoietin (50 ng/mL each). Cells were expanded in well plates and in two semipermeable bags.

RESULTS

A mean of 1.94 x 10(6) (+/- 1.55) CD34+ cells was obtained, yielding a CD34+ cell recovery of 52 +/- 12 percent. Nonspecific loss of CD34+ cells was 32 +/- 10 percent. CFU-GM and BFU-E/CFU-Mixed recoveries were 33 +/- 15 percent and 27 +/- 12 percent, respectively. CD34+ cells obtained were functionally comparable with fresh CD34+ cells selected for clonogenic potential. The capacity for expansion was not significantly different in the two types of bags studied. HPCs in wells were expanded 33 +/- 14-fold for CD34+ cells and 42 +/- 19-fold for overall colonies. The expansion rates observed in wells were significantly superior to those obtained in bags.

CONCLUSION

The feasibility of a clinical-scale cord blood selection procedure based on a direct immunomagnetic method after thawing, followed by an ex vivo expansion culture using semipermeable bags, is shown. After 6 days of expansion, it was possible to generate a 9-fold increase in CD34+ cells, a 6-fold increase in CFU-GM and a 13-fold increase in BFU-E/CFU-Mixed colonies.