Rapid debulking and CD34 enrichment of filgrastim-mobilized peripheral blood stem cells by semiautomated density gradient centrifugation in a closed system

Transplantation with low-density autologous PBSC prepared with BDS60 for women with Stage II, III and IV breast cancer

BACKGROUND

DS60 is a novel buoyant density solution, whose density has been adjusted to enrich PBSC from subjects who have been mobilized with cytokines alone, or cytokines plus chemotherapy. This report describes the use of BDS60 to enrich autologous PBSC that were used for hematological reconstitution after myeloablative chemotherapy in women with breast cancer.

METHODS

Fifty-one consecutive patients with high-risk Stage II or III breast cancer or chemotherapy-sensitive Stage IV breast cancer were enrolled. Forty-seven completed treatment and were evaluable. After mobilization with cyclophosphamide (4.0 g/m(2) i.v. once) and filgrastim (10 microg/kg/day), the patients underwent leukapheresis and the products were enriched with BDS60 using the DACS300 Kit. Myeloablative chemotherapy, given on Day -5 through Day -2, consisted of cyclophosphamide (1.5 g/m(2)/day), thiotepa (150 mg/m(2)/day) and carboplatin (200 mg/m(2)/day).

RESULTS

Forty-one patients underwent a single leukapheresis procedure to achieve the target number of BDS60-enriched CD34+ cells for transplantation (> or = 2 x 10(6)/kg). Five of the other six patients had less than the target number of cells in the leukapheresis product and thus required 2-4 leukapheresis procedures. Median cell recovery was 76.8% for CD34+ cells, 39.1% for nucleated cells, and 17.7% for platelets. Erythrocyte contamination of the final product was negligible. The median time to sustained neutrophil count > 500/mm(3) was 9 days (range: 8-12) and the median time to platelet count > 20 000/mm(3), without transfusion support, was also 9 days (range: 6-15). There were no late graft failures. Infusion-related adverse events were mild and no adverse events were attributed to the use of BDS60 to enrich CD34+ cells.

DISCUSSION

BDS60 is an effective, rapid method for enrichment of CD34+ cells by buoyant density centrifugation and the resulting cell product is safe and effective for engraftment after myeloablative therapy.

Characteristics of human dendritic cells generated in a microgravity analog culture system

Generation of an effective immune response requires that antigens be processed and presented to T lymphocytes by antigen-presenting cells, the most efficient of which are dendritic cells (DC). Because of their influence on both the innate and the acquired arms of immunity, a defect in DC would be expected to result in a broad impairment of immune function, not unlike that observed in astronauts during or after space flight. In the study reported here, we investigated whether DC generation and function are altered in a culture environment that models microgravity, i.e., the rotary-cell culture system (RCCS). We observed that RCCS supported the generation of DC identified by morphology, phenotype (HLA-DR+ and lacking lineage-associated markers), and function (high allostimulatory activity). However, the yield of DC from RCCS was significantly lower than that from static cultures. RCCS-generated DC were less able to phagocytose Aspergillus fumigatus conidia and expressed a lower density of surface HLA-DR. The proportion of DC expressing CD80 was also significantly reduced in RCCS compared to static cultures. When exposed to fungal antigens, RCCS-generated DC produced lower levels of interleukin-12 and failed to upregulate some costimulatory/adhesion molecules involved in antigen presentation. These data suggest that DC generation, and some functions needed to mount an effective immune response to pathogens, may be disturbed in the microgravity environment of space.

Dendritic cell-mediated stimulation of the in vitro lymphocyte response to Aspergillus

Lymphocytes play a major role in host defense against Aspergillus, but little is known about the contribution of dendritic cells (DC) to antifungal immunity in humans. We have observed that DC derived from normal volunteers phagocytose heat-killed A. fumigatus conidia. Following 24 h of exposure to the fungus, DC displayed an increase in the mean fluorescence intensity of HLA-DR, CD80, and CD86, and an increase in the percentage of CD54(+) cells. These DC also displayed increased production of IL-12. DC derived from CD34(+) progenitors or monocytes stimulated autologous lymphocytes to proliferate and produce high levels of interferon-gamma, but not interleukin-10, in response to fungal antigen. DC generated from CD34(+) progenitors collected prior to autologous or allogeneic stem cell transplantation also partially restored the in vitro antifungal proliferative response of lymphocytes obtained from patients 1 month after transplantation. These results suggest that DC are important to host-response to A. fumigatus, and that ex vivo-generated DC might be useful in restoring or enhancing the antifungal immunity after hematopoietic stem cell transplantation.

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

GVHD is a significant cause of morbidity and mortality following allogeneic peripheral blood stem cell transplantation (AlloPBSC). CD34+ cell selection could reduce GVHD by negative selection of T cells. In an attempt to reduce the T cell content of alloPBSC we carried out a trial in which 11 patients with hematologic malignancies received alloPBSC from HLA-matched siblings following density gradient separation using an isotonic colloidal silica solution (BDS 60; Dendreon Corporation). Cyclosporine and methylprednisone were used for GVHD prophylaxis. The mean yield of CD34+ cells was 69 +/- 15.6% with a purity of 2.9 +/- 1.7%. The mean number of CD3+ cells infused was 1.0 +/- 1.2 x 107/kg, representing a 1.3 log depletion. A high risk of acute GVHD was observed: grade II-IV in 7/11 (64%) and grade III-IV GVHD in 5/11 (45%) patients. Nine of the 11 (82%) patients died with a median survival of 68 days. Cytokine expression in PBSC was compared pre and post processing. Interferon-gamma was detected only following density gradient separation while IL-8 expression increased 3- to 6-fold post processing. Therefore, processing with this device may augment production of pro-inflammatory cytokines. Bone Marrow Transplantation (2000) 25, 1223-1228.