Search

Since HIV requires CD4 and a co-receptor, most commonly C-C chemokine receptor 5 (CCR5), for cellular entry, targeting CCR5 expression is an attractive approach for therapy of HIV infection. Treatment of CD4(+) T cells with zinc-finger protein nucleases (ZFNs) specifically disrupting chemokine receptor CCR5 coding sequences induces resistance to HIV infection in vitro and in vivo. A chimeric Ad5/F35 adenoviral vector encoding CCR5-ZFNs permitted efficient delivery and transient expression following anti-CD3/anti-CD28 costimulation of T lymphocytes. We present data showing CD3/CD28 costimulation substantially improved transduction efficiency over reported methods for Ad5/F35 transduction of T lymphocytes. Modifications to the laboratory scale process, incorporating clinically compatible reagents and methods, resulted in a robust ex vivo manufacturing process capable of generating10(10) CCR5 gene-edited CD4+ T cells from healthy and HIV+ donors. CD4+ T-cell phenotype, cytokine production, and repertoire were comparable between ZFN-modified and control cells. Following consultation with regulatory authorities, we conducted in vivo toxicity studies that showed no detectable ZFN-specific toxicity or T-cell transformation. Based on these findings, we initiated a clinical trial testing the safety and feasibility of CCR5 gene-edited CD4+ T-cell transfer in study subjects with HIV-1 infection.

Selective inhibition of disease-related proteins underpins the majority of successful drug–target interactions. However, development of effective antagonists is often hampered by targets that are not druggable using conventional approaches. Here, we apply engineered zinc-finger protein transcription factors (ZFP TFs) to the endogenous phospholamban (PLN) gene, which encodes a well validated but recalcitrant drug target in heart failure. We show that potent repression of PLN expression can be achieved with specificity that approaches single-gene regulation. Moreover, ZFP-driven repression of PLN increases calcium reuptake kinetics and improves contractile function of cardiac muscle both in vitro and in an animal model of heart failure. These results support the development of the PLN repressor as therapy for heart failure, and provide evidence that delivery of engineered ZFP TFs to native organs can drive therapeutically relevant levels of gene repression in vivo. Given the adaptability of designed ZFPs for binding diverse DNA sequences and the ubiquity of potential targets (promoter proximal DNA), our findings suggest that engineered ZFP repressors represent a powerful tool for the therapeutic inhibition of disease-related genes, therefore, offering the potential for therapeutic intervention in heart failure and other poorly treated human diseases.

Amyotrophic lateral sclerosis (ALS) is characterized by motor neuron loss leading to paralysis and death. Vascular endothelial growth factor (VEGF) has angiogenic, neurotrophic, and neuroprotective properties, and has preserved neuromuscular function and protected motor neurons in rats engineered to overexpress the human gene coding the mutated G93A form of the superoxide dismutase-1 (SOD1). We assessed the effects of intramuscular administration of a plasmid that encodes a zinc finger protein transcription factor (ZFP-TF) engineered to induce VEGF expression in the SOD1 rat model of ALS. Weekly injections of the plasmid preserved ipsilateral hindlimb grip strength and markedly improved rotarod performance in SOD1 rats compared to the vehicle-treated group. The number of motor neurons and the proportion of innervated neuromuscular junctions were similar in both groups. In conclusion, our data suggest that administration of the VEGF-ZFP-TF may be neuroprotective and has potential as a safe and practical approach for the management of motor disability in ALS.

Background— Therapeutic angiogenesis seeks to promote blood vessel growth to improve tissue perfusion. Vascular endothelial growth factor (VEGF) exists in multiple isoforms. We investigated an engineered zinc finger–containing transcription factor plasmid designed to activate the endogenous VEGF gene (ZFP-VEGF). Methods and Results— New Zealand White rabbits (n=56) underwent unilateral femoral artery ligation and excision. At day 10 postoperatively, the ischemic muscle received ZFP treatment (500 μg ZFP-VEGF plasmid) or no ZFP treatment (β-galactosidase, empty, or no plasmid). Group 1 (n=13) was harvested 3 days after injection to examine VEGF mRNA by real-time polymerase chain reaction and protein by ELISA. Groups 2 (n=13) and 3 (n=10) were harvested 11 days after injection. Group 2 was studied by histology and group 3, by histology and changes in blood flow. Groups 4 and 5 (n=10 each) were harvested 22 and 32 days after injection, respectively, and studied for changes in blood flow. In group 1, VEGF mRNA copy numbers were significantly higher for VEGF 121 , VEGF 165 , VEGF 189 , and protein in the ZFP-VEGF-treatment versus no-ZFP-treatment arms. In groups 2 and 3, capillary density and proliferating cells were significantly greater and apoptosis significantly lower in the treatment versus no-treatment arms. Changes in the blood flow ratio of the ischemic to the nonischemic limb were significantly greater in the treatment versus no-ZFP-treatment groups (6.57±1.52% versus 3.38±0.87%, P P P Conclusions— This engineered ZFP-VEGF–activating transcription factor may provide a novel approach to treat peripheral arterial disease.

The relationship between the structure of zinc-finger protein (ZFP) transcription factors and DNA sequence binding specificity has been extensively studied. Advances in this field have made it possible to design ZFPs de novo that will bind to specific targeted DNA sequences. It has been proposed that such designed ZFPs may eventually be useful in gene therapy. A principal advantage of this approach is that activation of an endogenous gene ensures expression of the natural array of splice variants. Preliminary studies in tissue culture have validated the feasibility of this approach. The studies reported here were intended to test whether engineered transcription factors are effective in a whole-organism model. ZFPs were designed to regulate the endogenous gene encoding vascular endothelial growth factor-A (Vegfa). Expression of these new ZFPs in vivo led to induced expression of the protein VEGF-A, stimulation of angiogenesis and acceleration of experimental wound healing. In addition, the neovasculature resulting from ZFP-induced expression of Vegfa was not hyperpermeable as was that produced by expression of murine Vegfa(164) cDNA. These data establish, for the first time, that specifically designed transcription factors can regulate an endogenous gene in vivo and evoke a potentially therapeutic biophysiologic effect.

We have mapped conserved regions of enhanced DNase I accessibility within the endogenous chromosomal locus of vascular endothelial growth factor A (VEGF-A). Synthetic zinc finger protein (ZFP) transcription factors were designed to target DNA sequences contained within the DNase I-hypersensitive regions. These ZFPs, when fused to either VP16 or p65 transcriptional activation domains, were able to activate expression of the VEGF-A gene as assayed by mRNA accumulation and VEGF-A protein secretion through a range exceeding that induced by hypoxic stress. Importantly, multiple splice variants of VEGF-A mRNA with defined physiological functions were induced by a single engineered ZFP transcription factor. We present evidence for an enhanced activation of VEGF-A gene transcription by ZFP transcription factors fused to VP16 and p65 targeted to two distinct chromosomal sites >500 base pairs upstream or downstream of the transcription start site. Our strategy provides a novel approach for dissecting the requirements for gene regulation at a distance without altering the DNA sequence of the endogenous target locus.

We have targeted the activation of an endogenous chromosomal locus including the human erythropoietin gene using synthetic transcription factors. These transcription factors are targeted to particular DNA sequences in the 5′-flanking region of the erythropoietin gene through engineering of a zinc finger DNA binding domain. The DNA binding domain is linked to a VP16 transcriptional activation domain. We find that these synthetic transcription factors invariably activate transiently transfected templates in which sequences within the 5′ flank of the erythropoietin gene are fused to a luciferase reporter. The efficiency of activation under these circumstances at a defined site is dependent on DNA binding affinity. In contrast, only a subset of these same zinc finger proteins is able to activate the endogenous chromosomal locus. The activity of these proteins is influenced by their capacity to gain access to their recognition elements within the chromatin infrastructure. Zinc finger transcription factors will provide a powerful tool to probe the determinants of chromatin accessibility and remodeling within endogenous chromosomal loci.

Background Recombinant adeno-associated viral (rAAV) vectors are capable of long-term expression of secreted and intracellular proteins following delivery to muscle, liver, and the central nervous system. In this study, we have evaluated subcutaneous injection of rAAV encoding a variety of transgenes as an alternative route of administration for the systemic delivery of therapeutic proteins. Methods rAAV vectors encoding the human factor IX, human interferon-α2a, murine erythropoietin (epo), and Escherichia coli lacZ genes were used for subcutaneous delivery into mature immunocompetent mice. Expression of factor IX and interferon in mouse serum was measured by ELISA. Expression of Epo was monitored by an increase in hemotocrit and by RIA. The tissue tropism of AAV transduction was determined by histochemistry following administration of the lacZ vector. Results Long-term protein expression (at least one year) is demonstrated in the serum of immunocompetent mice following subcutaneous delivery of AAV vectors encoding the human factor IX and interferon genes. The murine epo gene delivered via this route resulted in levels of Epo that correlate with increased hematocrits of up to 90% for a duration of nine months. rAAV encoding the lacZ gene revealed that the panniculus carnosus, a skeletal muscle layer of the skin, was transduced upon subcutaneous administration. Conclusions This study shows that long-term expression of secreted proteins can be achieved using rAAV vectors injected subcutaneously as a single administration. The observation that the panniculus carnosus is the primary tissue transduced by rAAV illustrates the high tropism of rAAV for skeletal muscle. Copyright © 1999 John Wiley & Sons, Ltd.

CCR5 is the major coreceptor for human immunodeficiency virus (HIV). We investigated whether site-specific modification of the gene ("gene editing")--in this case, the infusion of autologous CD4 T cells in which the CCR5 gene was rendered permanently dysfunctional by a zinc-finger nuclease (ZFN)--is safe.We enrolled 12 patients in an open-label, nonrandomized, uncontrolled study of a single dose of ZFN-modified autologous CD4 T cells. The patients had chronic aviremic HIV infection while they were receiving highly active antiretroviral therapy. Six of them underwent an interruption in antiretroviral treatment 4 weeks after the infusion of 10 billion autologous CD4 T cells, 11 to 28% of which were genetically modified with the ZFN. The primary outcome was safety as assessed by treatment-related adverse events. Secondary outcomes included measures of immune reconstitution and HIV resistance.One serious adverse event was associated with infusion of the ZFN-modified autologous CD4 T cells and was attributed to a transfusion reaction. The median CD4 T-cell count was 1517 per cubic millimeter at week 1, a significant increase from the preinfusion count of 448 per cubic millimeter (P0.001). The median concentration of CCR5-modified CD4 T cells at 1 week was 250 cells per cubic millimeter. This constituted 8.8% of circulating peripheral-blood mononuclear cells and 13.9% of circulating CD4 T cells. Modified cells had an estimated mean half-life of 48 weeks. During treatment interruption and the resultant viremia, the decline in circulating CCR5-modified cells (-1.81 cells per day) was significantly less than the decline in unmodified cells (-7.25 cells per day) (P=0.02). HIV RNA became undetectable in one of four patients who could be evaluated. The blood level of HIV DNA decreased in most patients.CCR5-modified autologous CD4 T-cell infusions are safe within the limits of this study. (Funded by the National Institute of Allergy and Infectious Diseases and others; ClinicalTrials.gov number, NCT00842634.).

Following spinal cord injury (SCI) there are drastic changes that occur in the spinal microvasculature, including ischemia, hemorrhage, endothelial cell death and blood-spinal cord barrier disruption. Vascular endothelial growth factor-A (VEGF-A) is a pleiotropic factor recognized for its pro-angiogenic properties; however, VEGF has recently been shown to provide neuroprotection. We hypothesized that delivery of AdV-ZFP-VEGF – an adenovirally delivered bio-engineered zinc-finger transcription factor that promotes endogenous VEGF-A expression – would result in angiogenesis, neuroprotection and functional recovery following SCI. This novel VEGF gene therapy induces the endogenous production of multiple VEGF-A isoforms; a critical factor for proper vascular development and repair. Briefly, female Wistar rats – under cyclosporin immunosuppression – received a 35 g clip-compression injury and were administered AdV-ZFP-VEGF or AdV-eGFP at 24 hours post-SCI. qRT-PCR and Western Blot analysis of VEGF-A mRNA and protein, showed significant increases in VEGF-A expression in AdV-ZFP-VEGF treated animals (p

Little is known about the potential for engraftment of autologous hematopoietic stem cells in human adults not subjected to myeloablative conditioning regimens. Five adult patients with the p47 phox deficiency form of chronic granulomatous disease received intravenous infusions of autologous CD34 + peripheral blood stem cells (PBSCs) that had been transduced ex vivo with a recombinant retrovirus encoding normal p47 phox . Although marrow conditioning was not given, functionally corrected granulocytes were detectable in peripheral blood of all five patients. Peak correction occurred 3–6 weeks after infusion and ranged from 0.004 to 0.05% of total peripheral blood granulocytes. Corrected cells were detectable for as long as 6 months after infusion in some individuals. Thus, prolonged engraftment of autologous PBSCs and continued expression of the transduced gene can occur in adults without conditioning. This trial also piloted the use of animal protein-free medium and a blood-bank-compatible closed system of gas-permeable plastic containers for culture and transduction of the PBSCs. These features enhance the safety of PBSCs directed gene therapy.

The goal of this work was to determine whether a stable 293 amphotropic packaging line, which we have designated 293-SPA, is useful for the production of high-titer stable virus by comparison to the murine psiCRIP line. Here, we report our unexpected findings that particles derived from the 293-SPA line transduce target cells (both NIH-3T3 cells and primary melanoma cells) with greatly enhanced efficiencies (at least 10-fold) compared to particles derived from the psiCRIP packaging line. We show that the presence of a transferable inhibitor in the psiCRIP line at least partially accounts for this dramatic difference in transduction efficiency. This work has important implications for improving the efficiency of retrovirus-mediated gene transfer in general as well as in the design of new packaging cell lines.

The p47phox−/− mouse exhibits a phenotype similar to that of human chronic granulomatous disease (CGD) and, thus, is an excellent model for the study of gene transfer technology. Using the Moloney murine leukemia virus–based retroviral vector MFG-S encoding the human form of p47phox, we performed ex vivo gene transfer into Sca-1+ p47phox−/− marrow progenitor cells without conditioning of donors with 5-fluorouracil. Transduced progenitors were transplanted into moderately irradiated (500 cGy), G-CSF preconditioned sibling p47phox−/− mice. Using the fluorescent probe dihydrorhodamine 123 (DHR), in vivo biochemical correction of the superoxide-generating NADPH oxidase system was detected by flow cytometry in 12.3% ± 0.9% of phorbol myristate acetate–stimulated peripheral blood neutrophils at 4 weeks and 2.6% ± 1.0% at 14 weeks after transplantation. Following gene therapy, mice were challenged with the CGD pathogen Burkholderia (formerly Pseudomonas) cepacia and bacteremia levels were assessed at 24 hours and 7 days after inoculation. At both time points, bacteremia levels in gene corrected p47phox−/− mice were significantly lower than untreated p47phox−/− mice (0.89 ± 0.30 colonies v 237.7 ± 83.6 colonies at 24 hours, P < .02; 4.0 ± 2.0 colonies v 110.2 ± 26.5 colonies at 7 days, P < .0014). More importantly, Kaplan-Meier survival analysis showed a significant survival advantage of gene corrected versus untreated p47phox−/− mice (P < .001). Thus, stem-cell–directed ex vivo gene therapy is capable of restoring phagocyte oxidant-dependent host-defense function in this mouse model of a human immune-system disorder.

Vascular endothelial growth factor (VEGF) plays a role in angiogenesis and has been shown to be neuroprotective following central nervous system trauma. In the present study we evaluated the pro-angiogenic and neuroprotective effects of an engineered zinc-finger protein transcription factor transactivator targeting the vascular endothelial growth factor A (VEGF-ZFP). We used two virus delivery systems, adeno-virus and adeno-associated virus, to examine the effects of early and delayed VEGF-A upregulation after brain trauma, respectively. Male Sprague-Dawley rats were subject to a unilateral fluid percussion injury (FPI) of moderate severity (2.2-2.5 atm) followed by intracerebral microinjection of either adenovirus vector (Adv) or an adeno-associated vector (AAV) carrying the VEGF-ZFP construct. Adv-VEGF-ZFP-treated animals had significantly fewer TUNEL positive cells in the injured penumbra of the cortex (p0.001) and hippocampus (p=0.001) relative to untreated rats at 72 h post-injury. Adv-VEGF-ZFP treatment significantly improved fEPSP values (p=0.007) in the CA1 region relative to injury alone. Treatment with AAV2-VEGF-ZFP resulted in improved post-injury microvascular diameter and improved functional recovery on the balance beam and rotarod task at 30 days post-injury. Collectively, the results provide supportive evidence for the concept of acute and delayed treatment following TBI using VEGF-ZFP to induce angiogenesis, reduce cell death, and enhance functional recovery.

Recent studies have identified anti-apoptotic functions for vascular endothelial growth factor (VEGF) in the central nervous system (CNS). However, VEGF therapy has been hampered by a tendency to promote vascular permeability, edema, and inflammation. Recently, engineered zinc finger proteins (ZFPs) that upregulate multiple forms of VEGF in their natural biological ratios, have been developed to overcome these negative side effects. We used retinal trauma and ischemia models, and a cortical pial strip ischemia model to determine if VEGF upregulating ZFPs are neuroprotective in the adult CNS. Optic nerve transection and ophthalmic artery ligation lead to the apoptotic degeneration of retinal ganglion cells (RGCs) and are, respectively, two highly reproducible models for CNS trauma or ischemia. Adeno-associated vectors (AAV) vectors encoding VEGF-ZFPs (AAV-VEGF-ZFP) significantly increased RGC survival by ∼twofold at 14 days after optic nerve transection or ophthalmic artery ligation. Furthermore, AAV-VEGF-ZFP enhanced recovery of the pupillary light reflex. RECA-1 immunostaining demonstrated no appreciable differences between retinas treated with AAV-VEGF-ZFP and controls, suggesting that AAV-VEGF-ZFP treatment did not affect retinal vasculature. Following pial strip of the forelimb motor cortex, brains treated with an adenovirus encoding VEGF ZFPs (AdV-ZFP) showed higher neuronal survival, accelerated wound contraction, and reduced lesion volume between 1 and 6 weeks after injury. Behavioral testing using the cylinder test for vertical exploration showed that AdV-VEGF-ZFP treatment enhanced contralateral forelimb function within the first 2 weeks after injury. Our results indicate that VEGF ZFP therapy is neuroprotective following traumatic injury or stroke in the adult mammalian CNS.

OBJECTIVE The objectives of the study were to evaluate retrograde axonal transport of vascular endothelial growth factor A (VEGF-A) protein to sensory neurons after intramuscular administration of an engineered zinc finger protein activator of endogenous VEGF-A (VZ+434) in an experimental model of diabetes, and to characterize the VEGF-A target neurons. RESEARCH DESIGN AND METHODS We compared the expression of VEGF-A in lumbar (L)4/5 dorsal root ganglia (DRG) of control rats and VZ+434-treated and untreated streptozotocin (STZ)-induced diabetic rats. In addition, axonal transport of VEGF-A, activation of signal transduction pathways in the DRG, and mechanical sensitivity were assessed. RESULTS VEGF-A immunoreactivity (IR) was detected in small- to medium-diameter neurons in DRG of control rats. Fewer VEGF-A-IR neurons were observed in DRG from STZ-induced diabetic rats; this decrease was confirmed and quantified by Western blotting. VZ+434 administration resulted in a significant increase in VEGF-A protein expression in ipsilateral DRG, 24 h after injection. VEGF-A was axonally transported to the DRG via the sciatic nerve. VZ+434 administration resulted in significant activation of AKT in the ipsilateral DRG by 48 h that was sustained for 1 week after injection. VZ+434 protected against mechanical allodynia 8 weeks after STZ injection. CONCLUSIONS Intramuscular administration of VZ+434 increases VEGF-A protein levels in L4/5 DRG, correcting the deficit observed after induction of diabetes, and protects against mechanical allodynia. Elevated VEGF-A levels result from retrograde axonal transport and are associated with altered signal transduction, via the phosphatidylinositol 3′-kinase pathway. These data support a neuroprotective role for VEGF-A in the therapeutic actions of VZ+434 and suggest a mechanism by which VEGF-A exerts this activity.

Purpose Self-complementary AAV (scAAV) vectors have been developed to circumvent rate-limiting second-strand synthesis in single-stranded AAV vector genomes and to facilitate robust transgene expression at a minimal dose. In this study, the authors investigated the effects of intraocular injections of type 2 scAAV.GFP in mice. Methods Dose-response experiments were performed to compare conventional single-strand AAV type 2 (ssAAV2) vectors with scAAV2 vectors encoding an identical expression cassette. Results Subretinal injection of 5 x 10(8) viral particles (vp) of scAAV.CMV-GFP resulted in green fluorescent protein (GFP) expression in almost all retinal pigment epithelial (RPE) cells within the area of the small detachment caused by the injection by 3 days and strong, diffuse expression by 7 days. Expression was strong in all retinal cell layers by days 14 and 28. In contrast, 3 days after subretinal injection of 5 x 10(8) vp of ssAAV.CMV-GFP, GFP expression was detectable in few RPE cells. Moreover, the ssAAV vector required 14 days for the attainment of expression levels comparable to those observed using scAAV at day 3. Expression in photoreceptors was not detectable until day 28. Dose-response experiments confirmed that onset of GFP expression was more rapid and robust after subretinal injection of scAAV.CMV-GFP than of ssAAV.CMV-GFP, resulting in pronounced expression in photoreceptors and other retinal neurons. Similar results were obtained for intravitreous injections. Conclusions These data suggest that scAAV vectors may be advantageous for ocular gene therapy, particularly in retinal diseases that require rapid and robust transgene expression in photoreceptor cells.

Hemophilia is an attractive target for gene therapy, since activity levels as low as 1% to 2% of normal are beneficial and levels of ~5% prevent spontaneous bleeding. Our goal was to provide a single treatment that permanently enables hepatic production of therapeutic levels of hFIX activity to decrease or potentially eliminate the need for prophylactic treatment in hemophilia B patients. We performed targeted in vivo genome editing using 1) two zinc finger nucleases (ZFNs) targeting intron 1 of the albumin locus, and 2) a human F9 donor template construct. The ZFNs and donor template are encoded on separate hepatotropic adeno-associated virus serotype 2/6 (AAV2/6) vectors injected intravenously, resulting in targeted insertion of a corrected copy of the hF9 gene into the albumin locus in a proportion of liver hepatocytes. The albumin locus was selected as a "safe harbor" as production of this most abundant plasma protein exceeds 10 g/day, and moderate reductions in those levels are well-tolerated. These genome edited hepatocytes produce normal hFIX in therapeutic quantities, rather than albumin, driven by the highly active albumin enhancer/promoter, to treat hemophilia B; the genetic modification is expected to be sustained even in the face of hepatocyte turnover, making this approach attractive for treating young children with hemophilia before the appearance of significant organ damage. Transformed and primary human hepatocytes transduced in vitro with AAV2/6 encoding human albumin ZFNs and a promoterless hF9 transgene were shown to secrete hFIX. Extensive molecular analyses demonstrated that this was due to targeted integration of the hF9 transgene at the albumin locus and splicing of this gene into the albumin transcript. By employing AAV2/6 delivery of murine-specific ZFNs in vivo, stable levels of hFIX were observed in blood of mice injected with the albumin ZFNs and hF9 transgene donor. C57BL/6 mice were administered vehicle (n=20) or AAV2/6 vectors (n=25) encoding mouse surrogate reagents at 1.0 x1013 vector genome (vg)/kg via tail vein injection. ELISA analysis of plasma hFIX in the treated mice showed peak levels of 50-1053 ng/mL that were sustained for the duration of the 6-month study. Analysis of FIX activity from mouse plasma confirmed bioactivity commensurate with expression levels. Next, we report the feasibility of this approach in non-human primates (NHPs), showing that a single intravenous co-infusion of AAV2/6 vectors encoding the NHP targeted albumin-specific ZFNs and a human F9 donor at 1.2x1013 vg/kg (n=5/group) resulted in >50 ng/mL (>1% of normal) in this large animal model. The use of higher AAV2/6 doses (up to 1.5x1014 vg/kg) yielded plasma hFIX levels up to 1000 ng/ml (or 20% of normal) in several animals and up to 2000 ng/ml (or 50% of normal) in a single animal, for the duration of the study (3 months). The treatment was well tolerated in mice and NHPs, with no significant toxicological findings related to AAV2/6 ZFN + donor treatment in either species at therapeutic doses. Together, these data support a clinical trial to determine if a single co-administration of ZFN and donor AAV vectors is sufficient to enable therapeutic and potentially lifelong production of the clotting factor for the treatment of Hemophilia B. Disclosures Wechsler: Sangamo BioSciences: Employment. Meyer:Sangamo Biosciences Inc: Employment. Spratt:Sangamo Biosciences Inc: Employment. Greengard:Sangamo Biosciences Inc: Employment. Santiago:Sangamo Biosciences Inc: Employment. Sproul:Sangamo Biosciences Inc: Employment. Surosky:Sangamo Biosciences Inc: Employment. Paschon:Sangamo Biosciences Inc: Employment. Dubois-Stringfellow:Sangamo Biosciences Inc: Employment. Ando:Sangamo Biosciences Inc: Employment. Nichol:Sangamo Biosciences Inc: Employment. Rebar:Sangamo BioSciences: Employment. Holmes:Sangamo BioSciences: Employment.

Zinc-finger protein transcription factors (ZFP TFs) can be designed to control the expression of any desired target gene, and thus provide potential therapeutic tools for the study and treatment of disease. Here we report that a ZFP TF can repress target gene expression with single-gene specificity within the human genome. A ZFP TF repressor that binds an 18-bp recognition sequence within the promoter of the endogenous CHK2 gene gives a >10-fold reduction in CHK2 mRNA and protein. This level of repression was sufficient to generate a functional phenotype, as demonstrated by the loss of DNA damage-induced CHK2-dependent p53 phosphorylation. We determined the specificity of repression by using DNA microarrays and found that the ZFP TF repressed a single gene ( CHK2 ) within the monitored genome in two different cell types. These data demonstrate the utility of ZFP TFs as precise tools for target validation, and highlight their potential as clinical therapeutics.

Improper calcium handling of the heart is a hallmark of patients with congestive heart failure (CHF). Because calcium is critical for cardiac contractility, proteins that regulate calcium homeostasis are potential targets treating CHF. Phospholamban (PLN) decreases contractility by inhibiting the activity of Sarcoplasmic Reticulum Ca2+ ATPase 2 isoform A (SERCA2a); an increased PLN/SERCA2a ratio is often found in CHF patients. Recent studies have demonstrated that ablation or inhibition of PLN function can improve cardiac contractile properties in animal models of CHF, suggesting that down-regulation of PLN may improve cardiac function in CHF patients. Importantly, inhibition of PLN enhances calcium handling without activating b-adrenergic pathways, which is known to have many side-effects and increase mortality. The development of small-molecule inhibitors of PLN function has so far been unsuccessful, largely due to the difficulty of inhibiting protein-protein interactions (such as that between PLN and SERCA2a) using small molecules. On the other hand, approaches that aim to block the expression of PLN may provide a superior means of achieving the desired therapeutic effect.

Phospholamban (PLN) is a critical regulator of cardiac calcium homeostasis and muscle contractility. Recent studies have demonstrated that ablation or inhibition of PLN function can improve cardiac contractile properties in animal models of congestive heart failure (CHF), suggesting that PLN is an attractive target for treatment of CHF. Because of its use of a large, relatively flat interaction surface when docking with its regulation target (Sarcoplasmic Reticulum Ca2+ ATPase 2 isoform A (SERCA2a)), the development of small-molecule inhibitors of PLN function is expected to be extremely challenging. Therefore, approaches that aim to block the expression of PLN may provide a superior means of achieving the desired therapeutic effect.

Zinc finger protein transcription factors (ZFP TFs) can be designed to regulate the expression of any endogenous gene, and thus provide a powerful platform for drug target validation and human therapeutics development. To deliver ZFP TFs into target cells that are difficult to transfect and for long-term expression of therapeutic ZFP TFs in mammalian tissues, we produced adeno-associated viral (AAV) vectors that express ZFP TFs using the triple plasmid transfection method. Crude AAV lysates were used to infect a range of cell types including a human osteosarcoma cell line (U2OS), human primary uterine smooth muscle cells (UtSMC) and rat primary cardiomyoctes. We show here that AAV vectors are capable of efficiently delivering ZFP TFs that cause the down-regulation of the checkpoint kinase 2 (CHK2) or phospholamban gene in these cells. Our results indicate that AAV vectors are effective vehicles for delivering therapeutic ZFP TFs and provide a convenient tool for functional screening of ZFP TFs in hard-to-transfect cells. The AAV vector that expresses a phospholamban-repressing ZFP TF validated here is currently being tested in pre-clinical animal models of congestive heart failure.