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D T Scadden

Publications and source records attributed to D T Scadden.

At least 37 records · Page 2Linked to original sources
PubMed2000

Active movement of T cells away from a chemokine.

Movement towards or away from a given stimulus guides the directional migration of prokaryotes, simple eukaryotes and neurons. As bi-directional cues may influence entry and exit of immune effector cells from tissue sites, we evaluated the migratory responses of T-cell subsets to varying concentrations of the chemokine stromal cell derived factor-1 (SDF-1). There was selective repulsion of subpopulations of T cells at high concentrations of recombinant SDF-1 or naturally occurring bone marrow-derived SDF-1, which could be inhibited by pertussis toxin and antibody against the chemokine receptor CXCR4. Distinct sensitivity profiles to genistein, herbimycin and 8-Br-cAMP biochemically distinguished movement of cells towards or away from an SDF-1 gradient. In vivo, antigen-induced T-cell recruitment into the peritoneal cavity was reversed by high but not low concentrations of SDF-1. The phenomenon of movement away from a chemokine represents a previously unknown mechanism regulating the localization of mature T cells. It adds to the functional repertoire of chemokines that may participate in immune physiology and may be applied therapeutically to alter the immune response.

Adult↗
PubMed2000

Efficient generation of human T cells from a tissue-engineered thymic organoid.

Biocompatible inorganic matrices have been used to enhance bone repair by integrating with endogenous bone architecture. Hypothesizing that a three-dimensional framework might support reconstruction of other tissues as well, we assessed the capacity of a tantalum-coated carbon matrix to support reconstitution of functioning thymic tissue. We engineered a thymic organoid by seeding matrices with murine thymic stroma. Co-culture of human bone marrow-derived hematopoietic progenitor cells within this xenogeneic environment generated mature functional T cells within 14 days. The proportionate T-cell yield from this system was highly reproducible, generating over 70% CD3+ T cells from either AC133+ or CD34+ progenitor cells. Cultured T cells expressed a high level of T-cell receptor excision circles (TREC), demonstrating de novo T lymphopoiesis, and function of fully mature T cells. This system not only facilitates analysis of the T-lymphopoietic potential of progenitor cell populations; it also permits ex vivo genesis of T cells for possible applications in treatment of immunodeficiency.

AC133 Antigen↗
PubMed2000

Pulsed electric fields for selection of hematopoietic cells and depletion of tumor cell contaminants.

Purging of tumor cells and selection of stem cells are key technologies for enabling stem cell transplantation and stem cell gene therapy. Here we report a strategy for cell selection based on physical properties of the cells. Exposing cells to an external pulsed electric field (PEF) increases the natural potential difference across the cell membrane until a critical threshold is reached and pore formation occurs, resulting in fatal perturbation of cell physiology. Attaining this threshold is a function of the applied field intensity and cell size, with larger cells porated at lower field intensities than smaller cells. Since hematopoietic stem cells are smaller than other hematopoietic cells and tumor cells, we found that exposure of peripheral blood mononuclear cells (PBMCs) to PEFs caused stepwise elimination of monocytes without affecting the function of smaller lymphocyte populations. Mobilized peripheral blood exposed to PEFs was enriched for CD34+/CD38- cells and stem cell function was preserved. Furthermore, PEF treatment was able to selectively purge blood preparations of tumor cells and eradicate transplantable tumor.

ADP-ribosyl Cyclase↗
PubMed2000

Stem cell repopulation efficiency but not pool size is governed by p27(kip1).

Sustained blood cell production requires preservation of a quiescent, multipotential stem cell pool that intermittently gives rise to progenitors with robust proliferative potential. The ability of cells to shift from a highly constrained to a vigorously active proliferative state is critical for maintaining stem cells while providing the responsiveness necessary for host defense. The cyclin-dependent kinase inhibitor (CDKI), p21(cip1/waf1) (p21) dominates stem cell kinetics. Here we report that another CDKI, p27(kip1) (p27), does not affect stem cell number, cell cycling, or self-renewal, but markedly alters progenitor proliferation and pool size. Therefore, distinct CDKIs govern the highly divergent stem and progenitor cell populations. When competitively transplanted, p27-deficient stem cells generate progenitors that eventually dominate blood cell production. Modulating p27 expression in a small number of stem cells may translate into effects on the majority of mature cells, thereby providing a strategy for potentiating the impact of transduced cells in stem cell gene therapy.

Animals↗
PubMed2000

Haematological aspects of HIV infection.

Multiple interacting factors contribute to the haematological manifestations of HIV disease. The effects of HIV-1 infection influence all haemopoietic cell lineages resulting in a spectrum of haematological abnormalities. Even in the absence of other pathological processes, bone marrow morphology is invariably abnormal, and anaemia, neutropenia and thrombocytopenia are all common during the course of disease. Intercurrent opportunistic infections may cause bone marrow suppression or induce specific cytopenias. Therapies used to treat HIV and its complications are frequently implicated as the cause of haematological dysfunction, and many have significant myelotoxic side-effects. Insights into the molecular basis for many of these abnormalities have permitted a clearer understanding of the pathophysiology of HIV-1 infection. Recombinant human growth factors that may be used to treat isolated cytopenias or to ameliorate the myelotoxic effects of other essential therapies. Lymph opoietic growth factors and the use of gene modified cells provide future therapeutic strategies that may alter the course of HIV disease.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Extracellular cyclic ADP-ribose increases intracellular free calcium concentration and stimulates proliferation of human hemopoietic progenitors.

Cyclic ADP-ribose (cADPR) is a universal second messenger that regulates many calcium-related cellular events by releasing calcium from intracellular stores. Since these events include enhanced cell proliferation and since the bone marrow harbors both ectoenzymes that generate cADPR from NAD(+) (CD38 and BST-1), we investigated the effects of extracellular cADPR on human hemopoietic progenitors (HP). Exposure of HP to 100 microM cADPR for 24 h induced a significant increase in colony output (P<0.01) and colony size (P<0.003). A horizontal expansion of HP, as demonstrated by a markedly increased replating efficiency in semisolid medium (up to 700 times compared to controls), was also observed, indicating that cADPR priming can affect cell growth for multiple generations over several weeks after exposure. Influx of extracellular cADPR into the cells was demonstrated, and a causal relationship between the functional effects and the increase of intracellular free calcium concentration induced by cADPR on HP was established through the use of specific antagonists. Similar effects on HP were produced by nanomolar concentrations of the nonhydrolyzable cADPR analog 3-deaza-cADPR. These data demonstrate that extracellular cADPR behaves as a cytokine enhancing the proliferation of human HP, a finding that may have biomedical applications for the ex vivo expansion of hemopoietic cells.

Adenosine Diphosphate Ribose↗
PubMed2000

Extracellular calcium elicits a chemokinetic response from monocytes in vitro and in vivo.

Recruitment of macrophages to sites of cell death is critical for induction of an immunologic response. Calcium concentrations in extracellular fluids vary markedly, and are particularly high at sites of injury or infection. We hypothesized that extracellular calcium participates in modulating the immune response, perhaps acting via the seven-transmembrane calcium-sensing receptor (CaR) on mature monocytes/macrophages. We observed a dose-dependent increase in monocyte chemotaxis in response to extracellular calcium or the selective allosteric CaR activator NPS R-467. In contrast, monocytes derived from mice deficient in CaR lacked the normal chemotactic response to a calcium gradient. Notably, CaR activation of monocytes bearing the receptor synergistically augmented the transmigration response of monocytes to the chemokine MCP-1 in association with increased cell-surface expression of its cognate receptor, CCR2. Conversely, stimulation of monocytes with MCP-1 or SDF-1alpha reciprocally increased CaR expression, suggesting a dual-enhancing interaction of Ca(2+) with chemokines in recruiting inflammatory cells. Subcutaneous administration in mice of Ca(2+), MCP-1, or (more potently) the combination of Ca(2+) and MCP-1, elicited an inflammatory infiltrate consisting of monocytes/macrophages. Thus extracellular calcium functions as an ionic chemokinetic agent capable of modulating the innate immune response in vivo and in vitro by direct and indirect actions on monocytic cells. Calcium deposition may be both consequence and cause of chronic inflammatory changes at sites of injury, infection, and atherosclerosis.

Animals↗
PubMed2000

Results of a randomized study of IM862 nasal solution in the treatment of AIDS-related Kaposi's sarcoma.

PURPOSE: Although advances have been made in the treatment of AIDS-related Kaposi's sarcoma (AIDS-KS) with systemic chemotherapy, less toxic therapies are needed. IM862 is a naturally occurring peptide with antiangiogenic properties and was thus studied in patients with AIDS-KS. PATIENTS AND METHODS: IM862 was given as intranasal drops at a dose of 5 mg. Patients were randomized to two dosing schedules given in repeated cycles until disease progression or unacceptable toxicity: 5 days of therapy followed by 5 days off (n = 18) and every other day dosing (n = 26). RESULTS: Forty-two male patients and two female patients with a median age of 38 years (range, 22 to 53 years) were accrued. Twenty-one patients (47%) had more than 50 mucocutaneous lesions, 14 (32%) had lymphedema, and none had visceral involvement. Thirty-three patients (75%) had received prior systemic chemotherapy. Twenty-four patients (55%) had CD4(+) lymphocyte count </= 200/mm(3). All but five patients were being treated with concurrent protease inhibitor(s), for a median of 10 months (range, 0 to 24 months). Major responses were documented in 36%, with five complete and 11 partial remissions, occurring after a median of 6 weeks (range, 3 to 26 weeks) and lasting a median of 33+ weeks (range, 12+ to 95+ weeks). Twenty-one patients had stable disease for periods of 7 to 72+ weeks. Adverse effects to IM862 were limited to mild and transient headache, fatigue, tingling, and nausea. No hematologic adverse effects attributed to treatment were reported. CONCLUSION: IM862 given as intranasal drops is well tolerated and has antitumor activity in patients with AIDS-KS. A randomized double-blinded study to define the activity of IM862 in patients with AIDS-KS is in progress.

AIDS-Related Opportunistic Infections↗
PubMed1999

Inhibition of human immunodeficiency virus replication and growth advantage of CD4+ T cells and monocytes derived from CD34+ cells transduced with an intracellular antibody directed against human immunodeficiency virus type 1 Tat.

Current clinical gene therapy protocols for the treatment of human immunodeficiency virus type 1 (HIV-1) infection involve the ex vivo transduction and expansion of CD4+ T cells derived from HIV-positive patients at a late stage in their disease (CD4+ cell count <400 cells/mm3). We examined the efficiency of transduction and transgene expression in adult bone marrow (BM)- and umbilical cord blood (UCB)-derived CD34+ cells induced to differentiate into T cells and monocytes in vitro with an MuLV-based vector encoding the neomycin resistance gene and an intracellular antibody directed against the Tat protein of HIV-1 (sFvtat1-Ckappa). The expression of the marker gene and the effects of antiviral construct on subsequent challenge with monocytotropic and T cell-tropic HIV-1 isolates were monitored in vitro in purified T cells and monocytes generated in culture from the transduced CD34+ cells. Transduction efficiencies of CD34+ cells ranged between 22 and 27%. Differentiation of CD34+ cells into T cells or monocytes was not significantly altered by the transduction process. HIV-1 replication in monocytes and CD4+ T cells derived from CD34+ cells transduced with the intracellular antibody gene was significantly reduced in comparison with the degree of HIV replication seen in monocytes and CD4+ T cells derived from CD34+ cells transduced with the neomycin resistance gene alone. Further, T cells and monocytes derived from CD34+ cells transduced with the intracellular antibody gene were demonstrated to express the sFvtat1-Ckappa transgene by RT-PCR and had a selective growth advantage in cultures that had been challenged with HIV-1. These data demonstrate that sFvtat1-Ckappa inhibits HIV-1 replication in T cells and monocytes developing from CD34+ cells and supports the continuing development of a stem cell gene therapy for the treatment of HIV-1 infection.

Adult↗
PubMed1999

Isolation and transduction of CD34+ cells from small quantities of peripheral blood from HIV-1-infected patients not treated with hemopoietic growth factors.

A proposed hemopoietic stem cell gene therapy for treatment for HIV infection would involve transduction of CD34+ hemopoietic stem cells with vectors encoding anti-HIV constructs. Peripheral blood has proved to be a useful source of these hemopoietic stem cells and this study exploits this finding. Small quantities of peripheral blood were obtained from HIV-negative patients and HIV-positive patients who were and were not receiving hemopoietic growth factors (HGFs). CD34+ cells were obtained from these samples using a simple technique and scored for frequency of colony type. This demonstrated that HIV-negative patients had the highest frequency of colony-forming units (CFUs). HIV-positive patients not treated with HGFs had a lower frequency of CFUs, but the same colony type distribution as HIV-negative patients. HIV-positive patients treated with HGFs had the lowest frequency of CFUs, but their colony type distribution demonstrated that they had responded to treatment. CD34+ cells selected in this way were also transduced with the murine retroviral MFG vector using a technique that demonstrated transduction efficiencies ranging from 2% to 16% (median, 11.5%). This study simplifies the experimental requirements for development of a hemopoietic stem cell gene therapy for HIV infection and offers the possibility that longitudinal studies could be performed on peripheral blood CD34+ cells from HIV-positive or HIV-negative patients without the need for granulocyte colony-stimulating factor mobilization.

Adult↗
PubMed1999

Normal development in porcine thymus grafts and specific tolerance of human T cells to porcine donor MHC.

The induction of T cell tolerance is likely to play an essential role in successful xenotransplantation in humans. In this study, we show that porcine thymus grafts in immunodeficient mice support normal development of polyclonal, functional human T cells. These T cells were specifically tolerant to MHC Ags of the porcine thymus donor and responded to nondonor porcine xenoantigens and alloantigens. Exogenous IL-2 did not abolish tolerance, suggesting central clonal deletion rather than anergy as the likely tolerance mechanism. Our study suggests that the thymic transplantation approach to achieving tolerance with restoration of immunocompetence may be applicable to xenotransplantation of pig tissues to humans.

Animals↗
PubMed1999

Notch1-induced delay of human hematopoietic progenitor cell differentiation is associated with altered cell cycle kinetics.

Hematopoiesis is a balance between proliferation and differentiation that may be modulated by environmental signals. Notch receptors and their ligands are highly conserved during evolution and have been shown to regulate cell fate decisions in multiple developmental systems. To assess whether Notch1 signaling may regulate human hematopoiesis to maintain cells in an immature state, we transduced a vesicular stomatitis virus G-protein (VSV-G) pseudo-typed bicistronic murine stem cell virus (MSCV)-based retroviral vector expressing a constitutively active form of Notch1 (ICN) and green fluorescence protein into the differentiation competent HL-60 cell line and primary cord blood-derived CD34(+) cells. In addition, we observed endogenous Notch1 expression on the surface of both HL-60 cells and primary CD34(+) cells, and therefore exposed cells to Notch ligand Jagged2, expressed on NIH3T3 cells. Both ligand-independent and ligand-dependent activation of Notch resulted in delayed acquisition of differentiation markers by HL-60 cells and cord blood CD34(+) cells. In addition, primary CD34(+) cells retained their ability to form immature colonies, colony-forming unit-mix (CFU-mix), whereas control cells lost this capacity. Activation of Notch1 correlated with a decrease in the fraction of HL-60 cells that were in G0/G1 phase before acquisition of a mature cell phenotype. This enhanced progression through G1 was noted despite preservation of the proliferative rate of the cells and the overall length of the cell cycle. These findings show that Notch1 activation delays human hematopoietic differentiation and suggest a link of Notch differentiation effects with altered cell cycle kinetics.

3T3 Cells↗
PubMed1999

Immune reconstitution in AIDS: oncologic implications and hematologic approaches.

Combination anti-retroviral therapy for HIV disease has profoundly altered the nature of the AIDS epidemic. Mitigating the impact of an uncontrollable decline in immune function is no longer the focal point for AIDS therapy, but has evolved to an emphasis on maximizing the potential for immune regeneration. Improved control of HIV replication has diminished, albeit unevenly, the frequency of AIDS-related malignancies and has altered the focus of hematologic and oncologic interventions in HIV disease. Now, with adoptive cellular therapies and the genetic engineering of cells in the clinical arena, the potential for cellular therapeutics in enhancing immune restoration is being tested. These approaches are based on better understanding of the immunobiology of HIV and its impact on hematopoietic tissues.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Intrinsic human immunodeficiency virus type 1 resistance of hematopoietic stem cells despite coreceptor expression.

Interactions of human immunodeficiency virus type 1 (HIV-1) with hematopoietic stem cells may define restrictions on immune reconstitution following effective antiretroviral therapy and affect stem cell gene therapy strategies for AIDS. In the present study, we demonstrated mRNA and cell surface expression of HIV-1 receptors CD4 and the chemokine receptors CCR-5 and CXCR-4 in fractionated cells representing multiple stages of hematopoietic development. Chemokine receptor function was documented in subsets of cells by calcium flux in response to a cognate ligand. Productive infection by HIV-1 via these receptors was observed with the notable exception of stem cells, in which case the presence of CD4, CXCR-4, and CCR-5, as documented by single-cell analysis for expression and function, was insufficient for infection. Neither productive infection, transgene expression, nor virus entry was detectable following exposure of stem cells to either wild-type HIV-1 or lentivirus constructs pseudotyped in HIV-1 envelopes of macrophage-tropic, T-cell-tropic, or dualtropic specificity. Successful entry into stem cells of a vesicular stomatitis virus G protein-pseudotyped HIV-1 construct demonstrated that the resistance to HIV-1 was mediated at the level of virus-cell membrane fusion and entry. These data define the hematopoietic stem cell as a sanctuary cell which is resistant to HIV-1 infection by a mechanism independent of receptor and coreceptor expression that suggests a novel means of cellular protection from HIV-1.

Acquired Immunodeficiency Syndrome↗
PubMed1999

The polysaccharide, PGG-glucan, enhances human myelopoiesis by direct action independent of and additive to early-acting cytokines.

beta-Glucans stimulate leukocyte anti-infective activity, enhance murine hematopoietic recovery following bone marrow injury and mobilize murine progenitor cells from bone marrow. This study evaluated the in vitro hematopoietic potential of the beta-glucan, PGG-glucan, on human bone marrow mononuclear cells (BMMC) and CD34+ BMMC compared with protein cytokines. In the presence of submaximal concentrations of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF; 0.5 ng/ml), PGG-glucan significantly increased BMMC myeloid colony formation comparable to the increase observed with either interleukin-3 (rhIL-3) or stem cell factor (rhSCF). Moreover, the addition of PGG-glucan to cultures containing GM-CSF + IL-3 or GM-CSF + SCF significantly augmented granulocyte-macrophage colony production above baseline, demonstrating that PGG-glucan acts independently of those early-acting cytokines and can enhance their activity in an additive manner. Anti-PGG-glucan monoclonal antibody specifically abrogated the growth-enhancing effect of added PGG-glucan in a saturable manner and other control carbohydrate polymers failed to affect colony formation. Further, PGG-glucan was not associated with induction of IL-6, GM-CSF production and removal of accessory cells by CD34+ cell isolation did not alter the PGG-glucan effect. These data demonstrate that PGG-glucan acts on committed myeloid progenitors to enhance human hematopoietic activity by a mechanism of direct action independent of IL-3 or SCF and independent of secondary cytokine stimulation.

Anti-Infective Agents↗
PubMed1999

Paclitaxel is safe and effective in the treatment of advanced AIDS-related Kaposi's sarcoma.

PURPOSE: Liposomal anthracyclines are the present standard treatment for advanced AIDS-related Kaposi's sarcoma (KS). No effective therapies have been defined for use after treatment failure of these agents. A phase II trial was thus conducted with paclitaxel in patients with advanced KS to assess safety and antitumor activity. MATERIALS AND METHODS: A regimen of paclitaxel at a dose of 100 mg/m(2) was given every 2 weeks to patients with advanced AIDS-related KS. Patients were treated until complete remission, disease progression, or unacceptable toxicity occurred. RESULTS: Fifty-six patients with advanced AIDS-related KS were accrued. Tumor-associated edema was present in 70% of patients and visceral involvement in 45%. Forty patients (71%) had received prior systemic therapy; 31 of these were resistant to an anthracycline. The median entry CD4(+) lymphocyte count was 20 cells/mm(3) (range, 0 to 358). A median of 10 cycles (range, 1 to 54+) of paclitaxel was administered. Fifty-nine percent of patients showed complete (n = 1) or partial response (n = 32) to paclitaxel. The median duration of response was 10.4 months (range, 2.8 to 26.7+ months) and the median survival was 15.4 months. The main side effects of therapy were grade 3 or 4 neutropenia in 61% of patients and mild-to-moderate alopecia in 87%. CONCLUSION: Paclitaxel at 100 mg/m(2) given every 2 weeks is active and well tolerated in the treatment of advanced and previously treated AIDS-related KS. The median duration of response is among the longest observed for any regimen or single agent reported for AIDS-related KS. Paclitaxel at this dosage and schedule is a treatment option for patients with advanced AIDS-related KS, including those who have experienced treatment failure of prior systemic therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Immunotoxin combined with chemotherapy for patients with AIDS-related non-Hodgkin's lymphoma.

BACKGROUND: The objective of this study was to develop and test a combined therapeutic approach for patients with AIDS-related lymphoma (ARL), employing agents with independent mechanisms of action and nonoverlapping toxicity. This study was designed to test the feasibility and tolerance of combining low dose chemotherapy with infusional immunotoxin in the treatment of ARL patients. METHODS: Previously untreated patients received low dose methotrexate, bleomycin, doxorubicin, cyclophosphamide, and vincristine (m-BACOD) on a 21- to 28-day schedule. Patients who did not have progressive disease by Cycle 3 received anti-B4-blocked ricin (anti-B4bR), a murine monoclonal antibody linked to modified ricin, 20 microg/kg/day for 7 days administered by continuous infusion on an outpatient basis. A repeat cycle of anti-B4-bR was administered during Cycle 4 of chemotherapy based on tolerance. Patients received two cycles of chemotherapy beyond complete remission up to eight cycles. Study endpoints were toxicity, development of human antimurine antibody (HAMA) and human antiricin (HARA), tumor response, and survival. RESULTS: Twenty-six of 44 patients received the immunotoxin therapy. Anti-B4-bR infusion was associated with transaminase elevation (Grade 3) in 14 of 26 patients (58%), and flulike symptoms were common. HAMA or HARA was observed in 8 patients (31%). The overall response rate was 57% (13 complete responses and 12 partial responses). The median survival for all patients was 8.9 months. CONCLUSIONS: This study demonstrates the safety and feasibility of using chemotherapy and immunotoxin therapies in combination and supports their further evaluation to improve the outcomes of patients with ARL.

Adult↗