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      Correction of Anemia in Uremic Rats by Intramuscular Injection of Lentivirus Carrying an Erythropoietin Gene

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          Background: Anemia is an inevitable consequence of chronic renal failure. Gene therapy using lentiviral vector (LV) would be an effective tool to treat anemia associated with renal failure. Methods: A LV carrying the erythropoietin (EPO) cDNA was administered to skeletal muscle of partially nephrectomized rats, which is a model of uremia. The red blood cell production and serum EPO levels were temporally monitored in these rats. Polymerase chain reaction assays were done to validate the presence of the LV in the experimental rats. Results: After a single intramuscular injection of LV at a dose of 55 µg p24 Gag antigen (∼5 × 10<sup>7</sup> transducing units), blood hematocrit (Hct) levels increased and peaked at 3 weeks (47.8 ± 4.2%, p < 0.01, n = 8) with the levels being maintained for at least 20 weeks (duration of study; 44.9 ± 3.3%, p < 0.01, n = 3). The control rats receiving LV expressing lacZ had Hct levels of 36.9 ± 4.1% (n = 8) at 3 weeks and 33.1 ± 3.7% (n = 4) at 20 weeks, respectively. The serum EPO levels in the rats injected with the LV expression EPO significantly increased (p < 0.01) to 156.3 ± 3.0 mU/ml compared to the control rats (63.9 ± 1.7 mU/ml). Polymerase chain reaction analysis of the isolated genomic DNA from the LV-injected rats showed specific positive detection of the LV in only the skeletal muscle tissue at the site of injection, whereas the other tissues, including the liver, spleen, and kidney, were negative. Conclusions: This study demonstrates that intramuscular injection of LV can produce highly efficient and sustained EPO secretion in uremic rats, and suggests that this approach could be an effective tool to deliver secretable proteins at therapeutic levels in various animal disease models.

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          Most cited references 22

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          Long-term pharmacologically regulated expression of erythropoietin in primates following AAV-mediated gene transfer.

          Gene therapy is a potential route for the delivery of secreted therapeutic proteins, but pharmacologic control of expression will generally be required for optimal safety and efficacy. Previous attempts to achieve regulated expression in large animal models have been thwarted by transient expression or immune responses to regulatory proteins. We evaluated the ability of the dimerizer-regulated gene expression system to achieve controlled, long-term production of erythropoietin (Epo) following intramuscular administration of adeno-associated virus (AAV) vectors to 16 primates. All animals showed dose-responsive and completely reversible elevation of Epo and hematocrit in response to the dimerizer rapamycin, or analogs with reduced immunosuppressive activity, administered intravenously or orally. Animals that received optimized dual vectors showed persistent regulated expression for the duration of the study, with no apparent immune response to Epo or the regulatory proteins. Similar results were obtained with single vectors incorporating both the Epo and regulatory genes, including those packaged into serotype 1 AAV vectors to allow use of lower viral doses. For the longest-studied animal, regulated expression has persisted for more than 6 years and 26 induction cycles. These data indicate that one-time or infrequent gene transfer followed by dimerizer regulation is a promising approach for delivery of therapeutic proteins.
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            Sustained expression of genes delivered directly into liver and muscle by lentiviral vectors.

            Successful gene therapy approaches will require efficient gene delivery and sustained expression of the transgene in recipients. A variety of methods, ranging from direct DNA delivery to infection with recombinant viruses containing foreign genes, have been developed, but they all have some major limitations that restrict their utility. We have described a human lentiviral (HIV)-based vector that can transduce non-dividing cells in vitro and deliver genes in vivo. With this vector, expression of transgenes in the brain has been detected for more than six months--the longest period tested so far. Because lentiviral vectors are pseudotyped with vesicular stomatitis virus G glycoprotein (VSVG; ref. 8), they can transduce a broad range of tissues and cell types. We now describe the ability of lentiviral vectors to introduce genes directly into liver and muscle. Sustained expression of green fluorescent protein (GFP), used as a surrogate for therapeutic protein, can be observed for more than 22 weeks in the liver. Similar long-term expression (more than eight weeks) was observed in transduced muscle. In contrast, little or no GFP could be detected in liver or muscle transduced with the Moloney murine leukaemia virus (M-MLV), a prototypic retroviral based vector. At a minimum, 3-4% of the total liver tissue was transduced by a single injection of 1-3 x 10(7) infectious units (I.U.) of recombinant HIV vector. Furthermore, no inflammation of recruitment of lymphocytes could be detected at the site of injection. Animals previously transduced with a lentiviral vector can be efficiently re-infected with lentiviral vectors. Additionally, we show that the requirement for lentiviral accessory proteins to establish efficient transduction in vivo is tissue dependent.
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              Stable transduction of quiescent CD34(+)CD38(-) human hematopoietic cells by HIV-1-based lentiviral vectors.

              We compared the efficiency of transduction by an HIV-1-based lentiviral vector to that by a Moloney murine leukemia virus (MLV) retroviral vector, using stringent in vitro assays of primitive, quiescent human hematopoietic progenitor cells. Each construct contained the enhanced green fluorescent protein (GFP) as a reporter gene. The lentiviral vector, but not the MLV vector, expressed GFP in nondivided CD34(+) cells (45.5% GFP+) and in CD34(+)CD38(-) cells in G0 (12.4% GFP+), 48 hr after transduction. However, GFP could also be detected short-term in CD34(+) cells transduced with a lentiviral vector that contained a mutated integrase gene. The level of stable transduction from integrated vector was determined after extended long-term bone marrow culture. Both MLV vectors and lentiviral vectors efficiently transduced cytokine-stimulated CD34(+) cells. The MLV vector did not transduce more primitive, quiescent CD34(+)CD38(-) cells (n = 8). In contrast, stable transduction of CD34(+)CD38(-) cells by the lentiviral vector was seen for over 15 weeks of extended long-term culture (9.2 +/- 5.2%, n = 7). GFP expression in clones from single CD34(+)CD38(-) cells confirmed efficient, stable lentiviral transduction in 29% of early and late-proliferating cells. In the absence of growth factors during transduction, only the lentiviral vector was able to transduce CD34(+) and CD34(+)CD38(-) cells (13.5 +/- 2.5%, n = 11 and 12.2 +/- 9.7%, n = 4, respectively). The lentiviral vector is clearly superior to the MLV vector for transduction of quiescent, primitive human hematopoietic progenitor cells and may provide therapeutically useful levels of gene transfer into human hematopoietic stem cells.

                Author and article information

                Am J Nephrol
                American Journal of Nephrology
                S. Karger AG
                September 2006
                15 September 2006
                : 26
                : 4
                : 326-334
                aDepartment of Internal Medicine, Chungbuk National University College of Medicine, Cheongju, Korea; bYanbian University College of Medicine, Yanbian, PR China; and cDepartment of Medicine, Medical College of Wisconsin, Milwaukee, Wisc., USA
                94401 Am J Nephrol 2006;26:326–334
                © 2006 S. Karger AG, Basel

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                Page count
                Figures: 5, References: 31, Pages: 9
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                Original Report: Laboratory Investigation


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