Allogeneic peripheral blood stem cell transplantation following CD34+ enrichment by density gradient separation

Multi-site evaluation of the BD Stem Cell Enumeration Kit for CD34(+) cell enumeration on the BD FACSCanto II and BD FACSCalibur flow cytometers

BACKGROUND AIMS

Evaluation of the BD Stem Cell Enumeration Kit was conducted at four clinical sites with flow cytometry CD34(+) enumeration to assess agreement between two investigational methods: (i) the BD FACSCanto II and BD FACSCalibur systems and (ii) the predicate method (Beckman Coulter StemKit and StemTrol, Immunotech SAS, Beckman Coulter, Marseille Cedex 9, France).

METHODS

Leftover and delinked specimens (n = 1032) from clinical flow cytometry testing were analyzed on the BD FACSCanto II (n = 918) and BD FACSCalibur (n = 905) in normal and mobilized blood, frozen and thawed bone marrow and leucopheresis and cord blood anticoagulated with citrate phosphate dextrose, anticoagulant citrate dextrose-solution A, heparin and ethylenediaminetetraacetate, alone or in combination. Fresh leucopheresis analysis addressed site equivalency for sample preparation, testing and analysis.

RESULTS

The mean relative bias showed agreement within predefined parameters for the BD FACSCanto II (-2.81 to 4.31 ±7.1) and BD FACSCalibur (-2.69 to 5.2 ±7.9). Results are reported as absolute and relative differences compared with the predicate for viable CD34(+), percentage of CD34(+) in CD45(+) and viable CD45(+) populations (or gates). Bias analyses of the distribution of the predicate low, mid and high bin values were done using BD FACSCanto II optimal gating and BD FACSCalibur manual gating for viable CD34(+), percentage of CD34(+) in CD45(+) and viable CD45(+). Bias results from both investigational methods show agreement. Deming regression analyses showed a linear relationship with R(2) > 0.92 for both investigational methods.

DISCUSSION

In conclusion, the results from both investigational methods demonstrated agreement and equivalence with the predicate method for enumeration of absolute viable CD34(+), percentage of viable CD34(+) in CD45(+) and absolute viable CD45(+) populations.

A novel high throughput immunomagnetic cell sorting system for potential clinical scale depletion of T cells for allogeneic stem cell transplantation

OBJECTIVE

To develop an immunomagnetic cell separation system for allogeneic hematopoietic stem cell (HSC) transplantations, which can achieve a high level of T-cell depletion (at least 4.0 log(10)), high level of recovery of hematopoietic stem cells (>90%), with a high throughput (>10(6) cells/second).

METHODS

Peripheral blood leukocytes (PBLs) from buffy coats were spiked with CD34-expressing cells (KG1a) to mimic a leukaphoresis product containing stimulated HSCs. T cells were labeled with anti-CD3(+) Dynabeads and separated in a quadrupole magnetic cell sorter (QMS). The performance of the system with respect to T-cell depletion and recovery of non-T cells and spiked KG1a was determined using four-color, flow cytometry analysis, with the aid of Trucount cell-concentration calibration beads. Limiting dilution assays were also performed to quantify the log(10) depletion of clonable T cells.

RESULTS

While the general performance of the QMS system is governed by proven theoretical principles, significant system variability exist, not all of which can be explained by our current understanding. Consequently, a factorial design was employed, guided by JMP software, to optimize the labeling conditions and operation of the QMS focused on maximizing the depletion of T cell, and recovery of unlabeled cells including KG1a cells. From these studies, an optimized, no wash, immunomagnetic labeling protocol and optimized QMS operating conditions were developed. For an average initial cell concentration of 1.7 x 10(8) total cells, an average 3.96 +/- 0.33 log(10) depletion (range, 3.53-4.34) of CD3(+)CD45(+) cells with a mean 99.43% +/- 4.23% recovery of CD34(+)CD45(+) cells (range, 94.38-104.90%) was achieved at a sorting speed of 10(6) cells/s (n = 6). Limiting dilution assays on the T-cell depleted fractions, which gave a log(10) depletion of 3.51 for the clonable T cells.

CONCLUSION

We suggest that this system will provide superior performance with respect to T-cell depletion and CD34(+) recovery for clinical allogeneic bone marrow transplants. Ongoing studies, on a clinical scale, are being conducted to demonstrate this claim.

Cell separation between mesenchymal progenitor cells through porous polymeric membranes

This study investigates the separation of two types of marrow stromal cells, KUSA-A1 osteoblasts and H-1/A preadipocytes, by filtration through various porous polymeric membranes. It was found that KUSA-A1 permeates better than H-1/A cells through 12-microm polyurethane foaming membranes. This appears to be due to the relatively smaller cell size of KUSA-A1 cells. In addition, when feed solutions containing suspensions of either cell type or a mixture of the two were used, the permeation ratio was relatively low (< 6%) through polyurethane and surface-modified polyurethane foaming membranes. It was also found that there was some degree of separation between KUSA-A1 and H-1/A cells (separation factor = 1.8) with nylon-net filter membranes, but no separation was obtained when filters made of nonwoven fabrics or silk screens were used. This ability of the nylon-net filter membranes to separate the two cell types was due to a sieving effect that results from an optimal pore size. Finally, permeation of a solution of human serum albumin through the membrane following filtration of the cells did not result in a separation of cells in the recovery solution.

Peripheral blood stem cells for allogeneic transplantation: a review

Peripheral blood stem cells (PBSCs) have become increasingly popular for use in hematopoietic stem cell transplantation. PBSCs are readily collected by continuous-flow apheresis from patients and healthy donors after the administration of s.c. recombinant colony-stimulating factors with only minimal morbidity and discomfort. Although the precise identification of PBSCs remains elusive, they can be phenotypically identified as a subset of all circulating CD34(+) cells. There are important phenotypic and biologic distinctions between PBSCs and bone marrow (BM)-derived progenitor cells. PBSCs express more lineage-specific antigens but are less metabolically active than their BM-derived counterparts. The use of PBSCs for allogeneic transplantation has been compared to BM in several randomized trials and cohort studies. The use of PBSCs in leukemia, myeloma, non-Hodgkin's lymphoma, and myelodysplasia has resulted in shorter times to neutrophil and platelet engraftment at the expense of increased rates of chronic graft-versus-host disease. The increase in graft-versus-host disease is mainly due to a log-fold increase in donor T cells transferred with the graft. Relapse rates after transplantation may be lower after PBSC transplantation but a convincing survival advantage has not been demonstrated overall. It is possible that a stronger graft-versus-tumor effect may exist with PBSCs when compared with BM although the mechanisms leading to this effect are not clear.