Biomedical subjects

Cynthia R Giver

Publications and source records attributed to Cynthia R Giver.

5 recordsLinked to original sources

PubMed2006

Graft engineering using ex vivo methods to limit GVHD: fludarabine treatment generates superior GVL effects in allogeneic BMT.

OBJECTIVE: To compare the abilities of different ex vivo methods of treating donor lymphocytes to inhibit graft-vs-host disease (GVHD) while preserving graft-vs-leukemia (GVL) activity in murine models of allogeneic bone marrow transplantation. METHODS: Donor/recipient pairs included MHC fully mismatched, MHC haplomismatched, and MiHA mismatched strain combinations. T cell-depleted BM (TCD-BM) was transplanted in combination with untreated, fludarabine-treated, 7.5-Gy gamma-irradiated, or psoralen/UVA (PUVA)-treated splenocytes. GVL activity was studied by adding a lethal number of recipient-type lymphoma cells. Posttransplant survival was determined, and GVHD and GVL activity were assessed by clinical and pathological scoring. Hematopoietic chimerism and donor T-cell expansion were analyzed by flow cytometry of peripheral blood samples at 30 and 60 days posttransplant. RESULTS: Allogeneic splenocytes treated with fludarabine, 7.5 Gy gamma-irradiation, or PUVA had significantly diminished GVHD activity, and all treated donor T cells facilitated engraftment by low-dose TCD-BM. Allogeneic splenocytes treated with fludarabine and, to a lesser extent, PUVA retained GVL activity and contributed more to donor T-cell chimerism compared to gamma-irradiated donor splenocytes. CONCLUSION: Among ex vivo methods of treating donor T cells to limit their proliferative capacity, fludarabine exposure had the greatest differential ability to inhibit the GVHD activity of allogeneic lymphocytes, while preserving their GVL activity and ability to engraft recipients. Thus, ex vivo treatment with fludarabine was superior to gamma-irradiation or PUVA in separating GVL from GVHD activity in murine models of allogeneic bone marrow transplantation.

Animals↗

PubMed2005

Risk factors and kinetics of thrombocytopenia associated with bortezomib for relapsed, refractory multiple myeloma.

Bortezomib, a proteasome inhibitor with efficacy in multiple myeloma, is associated with thrombocytopenia, the cause and kinetics of which are different from those of standard cytotoxic agents. We assessed the frequency, kinetics, and mechanism of thrombocytopenia following treatment with bortezomib 1.3 mg/m2 in 228 patients with relapsed and/or refractory myeloma in 2 phase 2 trials. The mean platelet count decreased by approximately 60% during treatment but recovered rapidly between treatments in a cyclic fashion. Among responders, the pretreatment platelet count increased significantly during subsequent cycles of therapy. The mean percent reduction in platelets was independent of baseline platelet count, M-protein concentration, and marrow plasmacytosis. Plasma thrombopoietin levels inversely correlated with platelet count. Murine studies demonstrated a reduction in peripheral platelet count following a single bortezomib dose without negative effects on megakaryocytic cellularity, ploidy, or morphology. These data suggest that bortezomib-induced thrombocytopenia is due to a reversible effect on megakaryocytic function rather than a direct cytotoxic effect on megakaryocytes or their progenitors. The exact mechanism underlying bortezomib-induced thrombocytopenia remains unknown but it is unlikely to be related to marrow injury or decreased thrombopoietin production.

Adult↗

PubMed2004

Reconstructing immunity after allogeneic transplantation.

A major goal of our research is to reduce the graft-vs-host disease (GVHD) activity of allogeneic donor T cells in bone marrow transplantation (BMT), while preserving graft-vs-tumor (GVT) effects. Using ex vivo immunosuppressive strategies and cell-separation techniques to modulate the graft prior to transplantation, we examined the roles of different donor immune cells on GVHD and GVT effects in allogeneic mouse models. Our results demonstrate that donor-memory CD4 T cells facilitate posttransplant immunological reconstitution without causing GVHD, whereas transplantation of equal numbers of donor naïve CD4 T cells leads to fatal GVHD. The initial events of donor T cells interacting with antigen-presenting cells (APCs) in the transplant recipient appear to be critical to the development of GVT, GVHD, or anergy to alloantigens. In the setting of clinical BMT, increased numbers of donor type 2 dendritic cells (DCs) were associated with an increased rate of posttransplant relapse, and decreased rates of chronic GVHD. In a mouse transplant model, manipulation of the DC content of bone marrow grafts was achieved by depletion of CD11b+ cells. Mice transplanted with CD11b- depleted marrow showed enhanced posttransplant expansion of memory T cells with markedly improved GVT activity and limited GVHD compared to recipients of unmanipulated marrow. A model that differentiates GVT from GVHD based on interaction of T-cell subsets with DC subsets is proposed.

Animals↗

PubMed2003

Ex vivo fludarabine exposure inhibits graft-versus-host activity of allogeneic T cells while preserving graft-versus-leukemia effects.

Allogeneic donor T cells in bone marrow transplantation (BMT) can contribute to beneficial graft-versus-leukemia (GVL) effects but can also cause detrimental graft-versus-host disease (GVHD). A successful method for the ex vivo treatment of donor T cells to limit their GVHD potential while retaining GVL activity would have broad clinical applications for patients undergoing allogeneic hematopoietic cell transplantation for malignant diseases. We hypothesized that donor lymphocyte infusions treated with fludarabine, an immunosuppressive nucleoside analog, would have reduced GVHD potential in a fully major histocompatibility complex-mismatched C57BL/6 --> B10.BR mouse BMT model. Recipients of fludarabine-treated donor lymphocyte infusions (F-DLI) had significantly reduced GVHD mortality, reduced histopathologic evidence of GVHD, and lower inflammatory serum cytokine levels than recipients of untreated DLI. Combined comparisons of GVHD incidence and donor-derived hematopoietic chimerism indicated that F-DLI had a therapeutic index superior to that of untreated DLI. Furthermore, adoptive immunotherapy of lymphoblastic lymphoma using F-DLI in the C57BL/6 --> B10.BR model demonstrated a broad therapeutic index with markedly reduced GVHD activity and preservation of GVL activity compared with untreated allogeneic T cells. Fludarabine exposure markedly reduced the CD4+CD44(low)-naive donor T-cell population within 48 hours of transplantation and altered the relative representation of cytokine-producing CD4+ T cells, consistent with T-helper type 2 polarization. However, proliferation of fludarabine-treated T cells in allogeneic recipient spleens was equivalent to that of untreated T cells. The results suggest that fludarabine reduces the GVHD potential of donor lymphocytes through effects on a CD4+CD44(low) T-cell population, with less effect on alloreactive T cells and CD4+CD44(high) memory T cells that are able to mediate GVL effects. Thus, F-DLI represents a novel method of immune modulation that may be useful to enhance immune reconstitution among allograft recipients with reduced risk of GVHD while retaining beneficial GVL effects.

Animals↗

PubMedDate not supplied

Facilitating T-cell immune reconstitution after haploidentical transplantation in adults.

Delayed reconstitution of cellular immunity following T-cell-depleted, CD34-enriched, allogeneic hematopoietic progenitor cell transplantation (HPCT) is the major cause of morbidity and mortality following haploidentical transplantation in adults. This is illustrated in our recent study of 28 high-risk adult patients (median age 31) who were treated with conditioning regimens containing antithymocyte globulin (ATG) before T-cell-depleted, CD34-enriched allogeneic HPCT. Overall mortality was 93% (26/28 patients) with a median survival of 4 months posttransplant. Poor cellular immune reconstitution contributed to death of 21/28 patients, with eight deaths due to opportunistic infections and seven deaths due to relapse. While recovery of normal numbers of circulating NK cells and B-cells occurred within the first 1-2 months posttransplant, recovery of normal numbers of blood T-cells was suppressed for more than 1 year. The mean half-life of active ATG levels in serum was 6 days; rapid clearance suggested that residual ATG did not contribute to the delay of posttransplant T-cell reconstitution. Rapid T-cell reconstitution was seen only in younger patients, indicating that poor thymic function and the absence of T-cells in the graft are the major causes of delayed recovery of cellular immunity. Improved cellular immunity after T-cell-depleted haploidentical HPCT will thus require novel strategies to adoptively transfer antigen specific donor T-cells without inducing lethal graft-versus-host disease (GvHD). This problem has been addressed in a preclinical murine model of MHC-mismatched bone marrow transplantation. Donor T-cells treated ex vivo with fludarabine or a UVA light-activated psoralen compound (amotosalen) have a markedly reduced ability to induce GvHD, yet the treated T-cells confer protection against murine cytomegalovirus and an infused leukemic cell line. Polyclonal donor T-cells reconstituted the blood and lymphoid compartments posttransplant and expanded in vivo. Derivatives of ex-vivo-treated donor T-cells retained the ability to produce cytokines and proliferate in response to antigen challenge. The mechanism of reduced GvHD potential of ex-vivo-treated T-cells appears to be selection of a subset of memory donor T-cells that do not initially home to secondary lymphoid organs and have reduced capacity for producing inflammation in the immediate posttransplant period. Direct selection of the memory subset by high-speed FACS confirmed the improved therapeutic index in the murine model system. Preclinical data indicate the feasibility of treating human T-cells with fludarabine, psoralen, or direct selection based upon the memory phenotype to efficiently produce a population of polyclonal donor T-cells with reduced GvHD activity. A planned clinical phase 1 trial of adoptive therapy utilizing ex vivo psoralen-treated donor T-cells in recipients of T-cell-depleted haploidentical HPCT is presented.

Adult↗