Activation of Pigment Epithelium–Derived Factor (PEDF) From Silenced Adenovector Genomes––Possible Therapeutic Approach for Prolonged Gene Expression Following Single Intravitreal Administration of AdPEDF

Abstract

Abstract: : Purpose: Transgene expression driven by the human cytomegalovirus (hCMV) promoter from adenovectors following intraocular administration into the eye is characterized by a rapid high–level burst of transgene expression that declines quickly followed by eventual loss of gene expression. We have shown that when marker genes, GFP or luciferase, are used, transgene expression could be reactivated from silenced adenovector genomes. In the current study, we investigate whether the potent antiangiogenic and neuroprotective factor, PEDF, can be re–expressed in the eye of the same animal after a single administration of adenovector containing the PEDF transgene. Methods: In these studies, replication–deficient adenovectors deleted of E1, E3, and E4 that express PEDF from the hCMV promoter were delivered into the eyes of mice by direct intravitreal injection. PEDF expression was monitored using a PEDF ELISA developed at GenVec, Inc. Re–activation of PEDF expression was induced by either systemic delivery of retinoic acid (RA) or administration of non–expressing adenovector particles to the vitreous. Results:Preliminary studies demonstrate that PEDF expression can be re–activated from silenced genomes one month following initial high transient PEDF protein levels by a single systemic administration of RA or intraocular administration of non–expression adenovector particles. Conclusions: These data are the first to our knowledge to demonstrate the re–expression of a potential therapeutic molecule following introduction into the eye and further suggests the use of adenovectors as a means of protein delivery to the eye for prolonged periods of time without re–administration. This approach could potentially provide local pulsatile therapy at the disease site.

Keywords: gene transfer/gene therapy • gene/expression • adenovirus