Positive and negative regulation of EAAT2 by NF-κB: a role for N-myc in TNFα-controlled repression

The glutamate transporter gene, EAAT2/GLT-1, is induced by epidermal growth factor (EGF) and downregulated by tumor necrosis factor α (TNFα). While TNFα is generally recognized as a positive regulator of NF-κB-dependent gene expression, its ability to control transcriptional repression is not well characterized. Additionally, the regulation of NF-κB by EGF is poorly understood. Herein, we demonstrate that both TNFα-mediated repression and EGF-mediated activation of EAAT2 expression require NF-κB. We show that EGF activates NF-κB independently of signaling to IκB. Furthermore, TNFα can abrogate IKKβ- and p65-mediated activation of EAAT2. Our results suggest that NF-κB can intrinsically activate EAAT2 and that TNFα mediates repression through a distinct pathway also requiring NF-κB. Consistently, we find that N-myc is recruited to the EAAT2 promoter with TNFα and that N-myc-binding sites are required for TNFα-mediated repression. Moreover, N-myc overexpression inhibits both basal and p65-induced activation of EAAT2. Our data highlight the remarkable specificity of NF-κB activity to regulate gene expression in response to diverse cellular signals and have implications for glutamate homeostasis and neurodegenerative disease

Safe, long-term hepatic expression of anti-HCV shRNA in a nonhuman primate model

The hepatitis C virus (HCV) chronically infects 2% of the world population and effective treatment is limited by long duration and significant side-effects. Here, we describe a novel drug, intended as a “single-shot ” therapy, which expresses three short hairpin RNAs (shRNAs) that simultaneously target multiple conserved regions of the HCV genome as confirmed in vitro by knockdown of an HCV replicon system. Using a recombinant adeno-associated virus (AAV) serotype 8 vector for delivery, comprehensive transduction of hepatocytes was achieved in vivo in a nonhuman primate (NHP) model following a single intravenous injection. However, dose ranging studies performed in 13 NHP resulted in high-expression levels of shRNA from wild-type (wt) Pol III promoters and dose-dependent hepatocellular toxicity, the first demonstration of shRNA-related toxicity in primates, establishing that the hepatotoxicity arises from highly conserved features of the RNA interference (RNAi) pathway. In the second generation drug, each promoter was re-engineered to reduce shRNA transcription to levels that circumvent toxicity but still inhibit replicon activity. In vivo testing of this modified construct in 18 NHPs showed conservation of hepatocyte transduction but complete elimination of hepatotoxicity, even with sustained shRNA expression for 50 days. These data support progression to a clinical study for treatment of HCV infection

Safety and efficacy of gene transfer for Leber's congenital amaurosis.

Leber's congenital amaurosis (LCA) is a group of inherited blinding diseases with onset during childhood. One form of the disease, LCA2, is caused by mutations in the retinal pigment epithelium-specific 65-kDa protein gene (RPE65). We investigated the safety of subretinal delivery of a recombinant adeno-associated virus (AAV) carrying RPE65 complementary DNA (cDNA) (ClinicalTrials.gov number, NCT00516477). Three patients with LCA2 had an acceptable local and systemic adverse-event profile after delivery of AAV2.hRPE65v2. Each patient had a modest improvement in measures of retinal function on subjective tests of visual acuity. In one patient, an asymptomatic macular hole developed, and although the occurrence was considered to be an adverse event, the patient had some return of retinal function. Although the follow-up was very short and normal vision was not achieved, this study provides the basis for further gene therapy studies in patients with LCA

Age-dependent effects of RPE65 gene therapy for Leber's congenital amaurosis: a phase 1 dose-escalation trial.

Background Gene therapy has the potential to reverse disease or prevent further deterioration of vision in patients with incurable inherited retinal degeneration. We therefore did a phase 1 trial to assess the effect of gene therapy on retinal and visual function in children and adults with Leber's congenital amaurosis.Methods We assessed the retinal and visual function in 12 patients (aged 8-44 years) with RPE65-associated Leber's congenital amaurosis given one subretinal injection of adeno-associated virus (AAV) containing a gene encoding a protein needed for the isomerohydrolase activity of the retinal pigment epithelium (AAV2-hRPE65v2) in the worst eye at low (1.5x10(10) vector genomes), medium (4.8x10(10) vector genomes), or high dose (1.5x10(11) vector genomes) for up to 2 years.Findings AAV2-hRPE65v2 was well tolerated and all patients showed sustained improvement in subjective and objective measurements of vision (ie, dark adaptometry, pupillometry, electroretinography, nystagmus, and ambulatory behaviour). Patients had at least a 2 log unit increase in pupillary light responses, and an 8-year-old child had nearly the same level of light sensitivity as that in age-matched normal-sighted individuals. The greatest improvement was noted in children, all of whom gained ambulatory vision. The study is registered with ClinicalTrials.gov, number NCT00516477.Interpretation The safety, extent, and stability of improvement in vision in all patients support the use of AAV mediated gene therapy for treatment of inherited retinal diseases, with early intervention resulting in the best potential gain.Background: Gene therapy has the potential to reverse disease or prevent further deterioration of vision in patients with incurable inherited retinal degeneration. We therefore did a phase 1 trial to assess the effect of gene therapy on retinal and visual function in children and adults with Leber's congenital amaurosis. Methods: We assessed the retinal and visual function in 12 patients (aged 8-44 years) with RPE65-associated Leber's congenital amaurosis given one subretinal injection of adeno-associated virus (AAV) containing a gene encoding a protein needed for the isomerohydrolase activity of the retinal pigment epithelium (AAV2-hRPE65v2) in the worst eye at low (1·5×1010 vector genomes), medium (4·8×1010 vector genomes), or high dose (1·5×1011 vector genomes) for up to 2 years. Findings: AAV2-hRPE65v2 was well tolerated and all patients showed sustained improvement in subjective and objective measurements of vision (ie, dark adaptometry, pupillometry, electroretinography, nystagmus, and ambulatory behaviour). Patients had at least a 2 log unit increase in pupillary light responses, and an 8-year-old child had nearly the same level of light sensitivity as that in age-matched normal-sighted individuals. The greatest improvement was noted in children, all of whom gained ambulatory vision. The study is registered with ClinicalTrials.gov, number NCT00516477. Interpretation: The safety, extent, and stability of improvement in vision in all patients support the use of AAV-mediated gene therapy for treatment of inherited retinal diseases, with early intervention resulting in the best potential gain. Funding: Center for Cellular and Molecular Therapeutics at the Children's Hospital of Philadelphia, Foundation Fighting Blindness, Telethon, Research to Prevent Blindness, F M Kirby Foundation, Mackall Foundation Trust, Regione Campania Convenzione, European Union, Associazione Italiana Amaurosi Congenita di Leber, Fund for Scientific Research, Fund for Research in Ophthalmology, and National Center for Research Resources. © 2009 Elsevier Ltd. All rights reserved

Characterization of a Recombinant Adeno-Associated Virus Type 2 Reference Standard Material

Here, the AAV Reference Standard Working Group presents the results of their international collaboration to produce and characterize a recombinant AAV serotype 2 Reference Standard Material. The purpose of this material is to provide a universal standard for particle titer, vector genome titer, and infectious titer for AAV2 gene transfer vectors