Gene Therapy for Optic nerve stroke (AION)

Abstract

Abstract: : Purpose: ICP10PK is a live attenuated herpesvirus–2 (HSV2) mutant virus, which has the RR domain of the chimeric ICP10 protein deleted, maintaining the active protein kinase domain (Aurelian, 2001). ICP10PK is neuroprotective in vitro and in vivo in a number of systems (Aurelian et al, 2000). Rodent ischemic optic neuropathy (rAION) is a recently developed optic nerve stroke model that can be used to directly evaluate potential neuroprotective therapies for clinical AION treatment. We wanted to determine whether ICP10PK injection is pathologic to the retina, and whether ICP10PK can be used to prevent or reduce post–rAION induced retinal ganglion cell (RGC) death. Methods: Male Sprague–Dawley rats (120–150g) were used. 1X106 units ICP10PK (1X106 PFU) were injected into the vitreous chamber of four animals for virus–associated retinopathy studies, and six animals for initial rAION studies. Virus–associated retinopathy study animals were euthanized at 7,10,14 and 21 days post–injection. For retinopathy studies, retinae were examined histologically using H&E and stained for microglia/macrophage activation using biotinylated lectin probe. Six additional animals were sham treated with intravitreal injection of 2ul of Dulbeccos minimal essential medium (DMEM). Four days post–injection, we induced rAION in ICP10PK and sham–treated animals using published methods (Bernstein et al, 2003). rAION animals were evaluated 2 days post–rAION induction, and euthanized at 15 days post–induction. Stereologic RGC counts were performed and RGC apoptotic death assayed using TUNEL assay Results: ICP10PK–injected animals maintained normal appearing retinae, without overt retinopathy. There was a possible slight increase in RGC cellularity 4 days post–ICP10PK injection (12.0 RGC/INL v. control; 10.1 RGC/INL). RGC numbers 21 days post ICP10 injection were normal (10.6± 0.3 RGC/INL v. control; 9.3± 0.9 RGC/INL). There were no increased numbers of lectin–stained macrophages. Following rAION induction, ICP10PK reduced post–rAION damage and reduced RGC layer loss. There were fewer TUNEL (+) cells in ICP10PK treated animals compared with sham treated controls. Conclusions:ICP10PK may be neuroprotective in reducing RGC damage and death post–optic nerve stroke. This gene therapy method may be useful in treating clinical AION during early presentation stages prior to actual RGC loss, to reduce post–AION RGC death and associated permanent visual loss.

Keywords: gene transfer/gene therapy • ischemia