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Biomedical subjects

W F Anderson

Publications and source records attributed to W F Anderson.

At least 199 records · Page 11Linked to original sources
PubMed1990

Retroviral vectors expressing soluble CD4: a potential gene therapy for AIDS.

Retroviral vectors have been developed which produce a secreted form of the helper/inducer T-cell antigen, CD4. Amphotropically packaged vectors were used to transduce cells, and these cells were shown to express the secreted CD4 (sCD4) gene product. The sCD4 produced by the viral vectors is immunoprecipitated by monoclonal antibodies against CD4, which specifically block human immunodeficiency virus (HIV) infection of helper/inducer T cells. A direct physical interaction of vector-produced sCD4 and HIV-1 gp120 was demonstrated by coprecipitation of sCD4/gp120 with antiserum directed against HIV gp120. Furthermore, transduced cells producing sCD4 can protect HIV-susceptible cells from infection by HIV. These data suggest that gene therapy is a potential approach for the treatment of AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Amphotropic murine leukemia retrovirus is not an acute pathogen for primates.

The in vivo fate of amphotropic murine leukemia retrovirus was studied in five rhesus monkeys. Retrovirus infused intravenously into 3 normal animals and 1 immunosuppressed animal was cleared rapidly from the circulation and subsequent viremia has not been detected (mean follow-up of 27.4 months). A fifth monkey was immunosuppressed and transplanted with virus-producing autologous fibroblasts in addition to an intraperitoneal injection of virus. This animal was viremic for 2 days and its lymph node cells and peripheral blood mononuclear cells were shown to be producing virus for up to 22 days post-inoculation, but subsequently has been negative after 17.0 months of analysis. In the 5 animals studied (combined mean follow-up of 25.7 months), clinical illness has not been identified at any time. Therefore, murine amphotropic retroviruses do not appear to pose an acute health risk.

AIDS-Related Complex↗
PubMed1990

What's the rush?

Explore the source record for details and available documents.

Animals↗
PubMed1990

Applications of the polymerase chain reaction in retroviral-mediated gene transfer and the analysis of gene-marked human TIL cells.

The polymerase chain reaction (PCR), a widely used new technology, was applied to several aspects of retroviral-mediated gene transfer. Ten oligonucleotide primer pairs were analyzed for their ability to amplify specific regions of a retroviral vector, including the long terminal repeat (LTR), and a NeoR selectable marker gene. By using the appropriate oligonucleotide primers, cells transduced by retroviral vectors could readily be detected and analyzed for deletions in proviral sequences by PCR, without Southern blotting. In combination with a simplified RNA isolation/reverse transcription protocol, an approximate titer of vector producer cell lines could be estimated by PCR in a single day, eliminating the need for time-consuming transductions and biological selection. Quantification of data obtained from PCR dilution experiment indicates that, under appropriate conditions, amplification is linear with respect to the amount of input DNA, permitting estimations of gene dosage in unknown samples. Specific PCR procedures have been developed as part of a protocol involving the transfer of retroviral-marked human tumor infiltrating lymphocytes (TIL) to cancer patients undergoing TIL cell cancer therapy. To augment biological safety testing methods, PCR has been used to detect the presence of possible amphotropic helper virus genomes at a sensitivity of one marked cell in 10(5) unmarked cells. The further use of PCR technology in the TIL cell human gene transfer protocol is demonstrated by the ability to detect small numbers of transduced TIL cells in the presence of hundreds of thousands of untransduced TIL.

Base Sequence↗
PubMed1990

In vivo expression and survival of gene-modified T lymphocytes in rhesus monkeys.

Lymphocytes can be readily transduced with retroviral vectors and the gene-modified lymphocytes will stably express the inserted genes in vitro for long periods. As a prelude to studies in humans, we evaluated the survival of gene-modified T lymphocytes and the expression of the introduced genes in nonhuman primate T lymphocytes both in vitro and in vivo to determine if lymphocytes could be a potential cellular gene therapy vehicle. Rhesus peripheral blood T-lymphocytes and/or lymph node lymphocytes were transduced with a retroviral vector that contained a bacterial neomycin resistance (NeoR) gene or both NeoR and the human adenosine deaminase (hADA) genes. The cells were then selected for NeoR expression by growth in the neomycin analogue G418 and the autologous gene-modified T cells were reintroduced into the donor animals. T lymphocytes were periodically regrown from the blood and selected in G418. Gene-modified cells persisted in 1 animal for 727 days as detected by analysis for vector DNA by polymerase chain reaction (PCR). Evidence for expression of the human ADA or NeoR genes has also been detected up to 727 days after cell infusion. These findings suggest that gene-modified T lymphocytes can survive and circulate for long periods in vivo and can continue to express the introduced genes.

Adenosine Deaminase↗
PubMed1990

A genetic therapy for familial hypercholesterolemia.

The WHHL rabbit serves as an animal model for the human genetic disease, familial hypercholesterolemia. In initial studies aimed at the development of a genetic therapy for familial hypercholesterolemia (i.e., introduction of a normal LDL receptor gene), WHHL rabbit skin fibroblasts were transduced with a retroviral vector expressing a normal human LDL receptor. Correction of the WHHL rabbit genetic defect in vitro was confirmed. Autologous fibroblasts expressing LDL receptors were reimplanted in donor rabbits and were found to survive and express the recombinant receptor in vivo for up to 4 weeks. In vivo LDL receptor expression by autologous cells stably transduced with functioning LDL receptors is possible. Transduction of greater numbers of cells along with increased cell survival in vivo may eventually lead to a specific and effective genetic therapy for familial hypercholesterolemia.

Animals↗
PubMed1990

Increased efficiency of gene transfer with retroviral vectors in neonatal hematopoietic progenitor cells.

The retroviral vector N2, which is derived from the Moloney murine leukemia retrovirus, was used to transfer the bacterial NeoR gene (conferring resistance to the neomycin analogue G418) into hematopoietic progenitor cells from fetal, neonatal, and adult dogs and cats. Infection of canine and feline bone marrow cells with the N2 vector resulted in resistance of granulocyte-macrophage colony-forming units (CFU-GM) to G418. Approximately 2%-4% of fetal liver, fetal bone marrow, and adult bone marrow day-7 CFU-GM were resistant to 1.75 mg/ml G418, a dose toxic to cells not expressing the NeoR gene, after infection with the N2 retrovirus. In sharp contrast to the low rate of infectivity of both fetal and adult marrow samples, the mean +/- SD of G418-resistant CFU-GM was 11.7% +/- 14.1% and 14.0% +/- 18.1% for neonatal dog and cat marrow samples, respectively. The neomycin phosphotransferase enzyme activity was detected in G418-resistant CFU-GM, confirming that G418-resistant CFU-GM expressed the NeoR gene. The increased efficiency of retroviral vector-mediated gene transfer into neonatal hematopoietic progenitor cells was not due to an increased fraction of actively dividing cells, as determined by tritiated thymidine suicide. Understanding the basis for increased gene transfer into neonatal hematopoietic progenitor cells may be helpful in designing effective retroviral vectors/gene transfer protocols for gene therapy.

Animals↗
PubMed1989

Establishment and characterization of adenosine deaminase-deficient human T cell lines.

We have established long term cell lines from a patient with adenosine deaminase (ADA)-deficient severe combined immunodeficiency by stimulation of blood and bone marrow cells with PHA and IL-2 followed by transformation of the activated cells with the human retrovirus HTLV-I. Despite the absence of detectable T cells in the patients blood, cell lines grew that carried the phenotype of mature activated T cells. TJF-2, the line established from blood, was characterized in detail. The concentration of ADA in TJF-2 cells was less than 1% of normal (3.2 U vs 413.0 U). Studies with pharmacologic inhibitors of ADA suggest that the residual adenosine deaminating activity of TJF-2 is from an enzyme distinct from true ADA, a nonspecific aminohydrolyase. Growth of TJF-2 cells was hypersensitive to inhibition by 2'-deoxyadenosine compared to normal T cells (ID50, 55 microM vs greater than 1000 microM). Analysis of 2'-deoxyadenosine-challenged cells showed that TJF-2 cells accumulated significant levels of deoxyadenosine triphosphate, whereas normal T cells did not unless they were also incubated with the ADA inhibitor deoxycoformycin. Southern and Northern blot analysis of these cells revealed a grossly intact ADA gene that produced a normal size ADA mRNA. Yet, despite ADA deficiency, cells of the TJF-2 line were otherwise indistinguishable from HTLV-I-transformed T cells derived from normal donors with respect to dependence on exogenous IL-2 for growth, clonal rearrangement patterns of TCR beta-chain genes, response to PHA, and rapid restoration of cellular volume after hypotonic challenge. The TJF-2 line thus represents a unique HTLV-I-transformed human T cell line exhibiting ADA deficiency and its expected metabolic consequences.

Adenosine Deaminase↗
PubMed1989

High-level recombinant gene expression in rabbit endothelial cells transduced by retroviral vectors.

By virtue of its immediate contact with the circulating blood, the endothelium provides an attractive target for retroviral vector transduction for the purpose of gene therapy. To see whether efficient gene transfer and expression was feasible, rabbit aortic endothelial cells were infected with three Moloney murine leukemia virus-derived retroviral vectors. Two of these vectors carry genes encoding products that are not secreted: N2, containing only the selectable marker gene neoR, and SAX, containing both neoR gene and an SV40-promoted adenosine deaminase (ADA) gene. The third vector, G2N, contains a secretory rat growth hormone (rGH) gene and an SV40-promoted neoR gene. Infection with all three vectors resulted in expression of the respective genes. A high level of human ADA expression was observed in infected endothelial cell populations both before and after selection in G418. G2N-infected rabbit aortic endothelial cells that were grown on a synthetic vascular graft continued to secrete rGH into the culture medium. These studies suggest that endothelial cells may serve as vehicles for the introduction in vivo of functioning recombinant genes.

Adenosine Deaminase↗
PubMed1989

Gene expression in implanted rat hepatocytes following retroviral-mediated gene transfer.

An hepatocyte transplantation-gene transfer protocol has been developed whereby liver cells containing an expressing NeoR gene can be successfully implanted in vivo. Adult primary cultures of rat hepatocytes, after infection with the retroviral vector N2, were grown on a floating solid support (coated with purified collagen IV) in a serum-free hormonally defined medium designed for hepatocytes that also contained G418. Under these conditions, normal adult hepatocytes expressing the NeoR gene could be grown to high density. The solid supports holding the gene-engineered hepatocytes were then implanted into adult rats into subcutaneous and intraperitoneal sites. After one to two weeks, the supports were removed and shown to still contain the gene-engineered hepatocytes expressing the NeoR gene. These results suggest that cells from solid organs, such as the liver, are potential targets for gene transfer and expression studies in vivo.

Animals↗
PubMed1989

Protamine sulfate as an effective alternative to polybrene in retroviral-mediated gene-transfer: implications for human gene therapy.

The polycation protamine sulfate was compared to polybrene, the usual agent employed, for its ability to increase the efficiency of retroviral infection. The murine retroviral vector SAX, which contains the neoR gene and the human adenosine deaminase (ADA) cDNA, was used as a marker of cell infection. SAX viral supernate was titered on NIH 3T3 cells in varying concentrations of polycation. The highest infection efficiency for protamine was seen at 5 micrograms/ml and was 7-fold greater than infections performed in the absence of polycation. Infection efficiency using protamine averaged 92% +/- 11 (SEM) of the highest efficiency obtained with polybrene. Total ADA activity attained when human-ADA deficient T cells were exposed to SAX supernate in the presence of protamine was 83% of that attained with polybrene. The infection rate of mouse bone marrow early progenitor cells (CFU-S) was similar with each polycation. In summary, for supernate infections, concentrations of 5-10 micrograms/ml of protamine provided essentially the same infection efficiency as polybrene with low toxicity on a range of cell types. Since protamine is approved for human use by the U.S. Food and Drug Administration it provides an effective alternative to polybrene when developing human gene therapy protocols.

Animals↗
PubMed1989

Gene transfer into primates and prospects for gene therapy in humans.

Retroviral vectors infect primate bone marrow cells and express in vivo the transferred genes (the human ADA gene and the bacterial gene for neomycin resistance). The SAX vector appears to express human ADA at normal levels, but the infection efficiency is low (less than 1%) so that the gene product is only detectable in the peripheral blood at low levels. Vector expression disappears after 5 months (except for occasional T cells), presumably due to a failure to infect a renewal stem cell. While the level of ADA expression obtained in primates would not appear to be sufficient to correct outright the disease caused by ADA deficiency, it is possible that T-cell progenitors in the marrow will have a selective advantage. T cells expressing an ADA vector would then able to expand and potentially restore immune function. Unfortunately, this hypothesis will go untested until an animal model for ADA deficiency is found or a human clinical trial is performed. At present, consideration of gene therapy as a treatment for ADA deficiency would only be appropriate if all conventional forms of treatment were unsuccessful. If such a scenario should present itself, the critical question becomes one of safety, to both the patient and those in contact with the patient. We have begun to address the safety issues associated with gene therapy. Five animals exposed to replication-competent retrovirus during bone marrow transplantation show no evidence of helper virus, with a mean follow-up of 18.3 months. Four animals injected with replication-competent helper virus cleared the virus rapidly and, after the initial clearance, have shown no evidence of retroviremia, with a mean follow-up of 5.2 months. Our preliminary findings suggest that murine retorviruses do not cause a productive infection in vivo. These results, combined with the availability of better producer cell lines free of helper virus, are encouraging, and suggest that the risk of clinical disease from murine retrovirus introduced by a gene therapy protocol should be small. Unfortunately, high infection efficiency and long-term vector expression still must be obtained before retroviral-mediated gene transfer can be considered as first-line therapy for ADA deficiency.

Animals↗
PubMed1989

Heparin-binding growth factor 1 induces the formation of organoid neovascular structures in vivo.

One of the promises of modern molecular biology has been the opportunity to use genetically modified human cells in a patient to permanently restore inborn errors of metabolism. Although it has been possible to introduce genes into mammalian cells and to control their expression, it has proven difficult to introduce mammalian cells as carriers of the modified genetic information into hosts. The successful implantation of selective cells cannot be achieved without adequate vascular support, an essential step toward integration and reconstitution of a new biological function. Although a partial solution to this problem has been found by inducing specific site-directed neovessel formation using heparin-binding growth factor 1 (HBGF-1) adsorbed to a collagen matrix, these implants function for only a short period (weeks). We now report the formation of organoid neovascular structures using polytetrafluoroethylene fibers coated with collagen and HBGF-1 implanted in the peritoneal cavity of the rat. The organoid structures contained readily visible vascular lumina and nonvascular structures that resemble nerve tissue. It was also possible to demonstrate that the vascular system on the implant is continuous with the vascular tree of the host. This feature was used to demonstrate that the organoid structures are capable of sustaining the biological function of implanted normal rat hepatocytes over long periods of time (months) in the homozygous Gunn rat, thereby facilitating future applications involving the delivery of new genetic information.

Animals↗
PubMed1989

Human gene therapy: why draw a line?

Despite widespread agreement that it would be ethical to use somatic cell gene therapy to correct serious diseases, there is still uneasiness on the part of the public about this procedure. The basis for this concern lies less with the procedure's clinical risks than with fear that genetic engineering could lead to changes in human nature. Legitimate concerns about the potential for misuse of gene transfer technology justify drawing a moral line that includes corrective germline therapy but excludes enhancement interventions in both somatic and germline contexts.

Beneficence↗
PubMed1989

Infection efficiency of T lymphocytes with amphotropic retroviral vectors is cell cycle dependent.

The role of the host cell cycle in determining the efficiency of infection with amphotropically packaged retroviral vectors was investigated in T lymphocytes and in fibroblasts. For T lymphocytes, the efficiency of infection with a retroviral vector was dependent on the cell cycle distribution of cells in culture at the time of exposure to the vector. When cultures enriched in the G0-G1 phase of the cell cycle (by serum starvation, aphidicolin treatment, or centrifugal elutriation) were exposed to retroviral vectors, the infection efficiency was severalfold lower than that in similar cultures enriched in the S, G2, and M phases. For fibroblasts, the efficiency of infection was not cell cycle dependent. These findings are relevant for studies with retrovirus-mediated gene transfer into hematopoietic tissues.

Animals↗
PubMed1989

The C-terminal domain of the largest subunit of RNA polymerase II and transcription initiation.

Monoclonal antibodies specific for the evolutionarily conserved C-terminal heptapeptide repeat domain of the largest subunit of RNA polymerase II inhibited the initiation of transcription from mammalian promoters in vitro. Since these antibodies did not inhibit elongation and randomly initiated transcription, the heptapeptide repeats may function by binding class II transcription initiation factor(s).

Amino Acid Sequence↗