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B C Engel

Publications and source records attributed to B C Engel.

5 recordsLinked to original sources
PubMed2000

Intrakines--evidence for a trans-cellular mechanism of action.

Human CXCR4 is the receptor for the CXC chemokine SDF-1alpha and also acts as a coreceptor for T lymphotropic HIV-1 strains. Blocking the surface expression of this receptor via an intrakine approach has recently been shown to efficiently prevent HIV-1 infection of T cells. The CXC-chemokine gene is fused to an endoplasmic reticulum retention signal (KDEL) that retains the newly synthesized chemokine and its receptor within the cell, where both are subsequently degraded. We constructed MoMuLV-based vectors containing the SDF-KDEL construct driven by the "MND" long terminal repeat, using eGFP as a marker gene (MND-SDF-KDEL-IRES-eGFP) and a control vector (MND-X-IRES-eGFP). CEM human T lymphoblastic leukemia cells were transduced with the intrakine vector or the control vector. We detected a marked downregulation of CXCR4 expression in the cells transduced with the intrakine vectors as opposed to the cells transduced with the control vector. However, the eGFP-negative fraction of the cells transduced with the intrakine vector displayed the same CXCR4 downregulation as the eGFP-positive fraction, suggesting an effect in trans. The possibility of this being due to eGFP being silenced while SDF-KDEL was still expressed was excluded by Southern and Northern blot analyses. Upon cultivating the control cells with supernatant of the cells transduced with the intrakine vector, we observed a downregulation of CXCR4 expression on the control cells. Experiments using rhSDF-1alpha showed downregulation by the supernatant to be comparable to that achieved by the exogenous addition of 30 ng/ml SDF-1alpha. To assess the bioactivity of the secreted substance in the supernatant, a chemotaxis assay was performed. The transmigration observed was, once again, within the range of that achieved by the addition of 30 ng/ml SDF-1alpha. We conclude that the intrakine SDF-KDEL, apart from acting within the cell, is also in part secreted and causes the downregulation of the receptor by acting like a secreted chemokine.

Blotting, Northern↗
PubMed1999

Stem cell directed gene therapy.

A potential therapeutic approach to HIV-1 infection is the genetic modification of cells of a patient to make them resistant to HIV-1. Hematopoietic stem cells are an attractive target for gene therapy of AIDS because of their ability to generate a broad repertoire of mature T lymphocytes, as well as the monocytic cells (macrophages, dendritic cells and microglia) which are also involved in HIV-1 pathogenesis. A number of synthetic "anti-HIV-1 genes" have been developed which inhibit HIV-1 replication. However, current methods for gene transfer into human hematopoietic stem cells, using retroviral vectors derived from the Moloney murine leukemia virus, have been minimally effective. Clinical trials performed to date in which hematopoietic cells from HIV-1-positive patients have been transduced with retroviral vectors and then reinfused have produced low to undetectable levels of gene-containing peripheral blood leukocytes. New vector delivery systems, such as lentiviral vectors, need to be developed to ensure efficient gene transfer and persistent transgene expression to provide life-long resistance to the cells targeted by HIV-1.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Induction of a CD3+/CD56+ lymphocyte population following gene therapy with transgenic IL-2 secreting fibroblasts in a child with peripheral neuroectodermal malignancy.

BACKGROUND: Adjuvant interleukin-2 (IL-2) therapy after stem cell transplantation can improve the prognosis of patients with Ewing tumors. This has been attributed to stimulation of the immune system and its antineoplastic activity, thus eliminating minimal residual disease. As the side effects of systemic IL-2 limit the dosage, attempts have been made to locally augment the concentration of IL-2 in the proximity of the tumor. To achieve this, fibroblasts and/or tumor cells can be genetically modified to secrete IL-2 and then be injected to generate tumor immunogen. PROCEDURE: In a preliminary clinical trial we assessed whether the administration of transgenic IL-2-secreting fibroblasts was feasible without major toxicity and whether it had any effect regarding the activation of the immune system. We treated an 11-year-old boy with a peripheral neuroectodermal tumor of the left neck in fourth relapse, who was refractory to all available therapy. We transfected fibroblasts of the patient with an IL-2 gene expression vector using a cationic liposome reagent. In 51Cr cytotoxicity assays we obtained lysis of this patient's tumor cells by IL-2-stimulated mononuclear cells (MNCs). Under CT-guidance we intratumorally injected IL-2 transgenic autologous fibroblasts. RESULTS: We observed no local or systemic toxicity. In addition, we found a rise in the CD3+CD56+ lymphocyte population, previously described as cytokine-induced killer cells. No other hematological parameter changed significantly. CONCLUSIONS: Our data suggest that the intratumoral injection of transgenic IL-2-secreting fibroblasts is feasible without major toxicity and may lead to an increase in CD3+CD56+ cells.

CD3 Complex↗
PubMedDate not supplied

Circulating CD34+ cell counts as predictive parameter for the efficacy of peripheral stem cell apheresis in Ewing tumor patients.

The parameters used by different centers for starting peripheral stem cell apheresis following mobilization with chemotherapy and G-CSF are diverse. We retrospectively analysed 62 leukaphereses performed on eleven patients with Ewing Tumors and one patient with Synovial Sarcoma, all after treatment with standardized chemotherapy (according to the EICESS protocol) and subsequent administration of G-CSF. Blood samples, drawn before the apheresis and samples of the apheresis products were analysed by flow cytometry for their content of CD34+ cells, furthermore, the peripheral leukocyte count was determined. Our aim was to define a parameter that reliably predicts the efficacy of leukapheresis in these patients. We found a significant correlation (r = 0.85; p < 0.0001) between the absolute CD34 positive cell count prior to leukapheresis and the yield of CD34+ cells/kg body weight (bw) in the apheresis product. No correlation was observed between the leukocyte count prior to apheresis and CD34+ cells/kg bw in the apheresis product (r = 0.14; p < 0.28). In addition, we found no correlation between the number of CFU-GM in the apheresis product and the CD34+ cells/kg bw (r = 0.22; p < 0.35). Our data indicate that the peripheral CD34 positive cell count prior to leukapheresis is the best parameter for predicting the efficacy of peripheral stem cell apheresis in Ewing Tumor patients after treatment with standardized chemotherapy.

Adolescent↗