RETROVIRUS-MEDIATED SUICIDE GENE TRANSDUCTION IN THE VITREOUS CAVITY OF THE EYE - FEASIBILITY IN PREVENTION OF PROLIFERATIVE VITREORETINOPATHY

In proliferative vitreoretinopathy (PVR), retinal pigment epithelial c ells, fibroblasts, or other proliferating cells form contractile membr anes in the vitreous cavity of the eye, resulting in traction retinal detachment. Retroviral vector-mediated transfer is a suitable method t o transduce the herpes simplex virus thymidine kinase (HSV-tk) gene in to proliferating cells in PVR, allowing for the selective killing of t hese cells. To determine the potential of gene transduction in the env ironment of the vitreous cavity, we evaluated the effect of vitreous h umor on retroviral vector-mediated gene transduction of rabbit dermal fibroblasts in vitro and studied in vivo transduction in rabbit experi mental PVR with retroviral vector G1BgSvNa. In addition, we studied th e bystander effect in vitro and in vivo in a rabbit model of PVR, with low percentages of HSV-tk-positive cells. Finally, we evaluated the e fficacy of intravitreal administration of HSV-tk retroviral vector G1T kSvNa followed by ganciclovir (GCV) in the prevention of experimental PVR. Vitreous humor reduced gene transfer efficiency in vitro in a dos e-dependent manner. LacZ expression was found in cells of preretinal o r intravitreal membranes of animals of both in vivo and in vitro trans duction groups; however, in vivo transduction resulted in a decreased number of transduced cells, with a relative transduction efficiency of approximately 2%. Transduction of HSV-tk was associated with a powerf ul bystander effect both in vitro and in vivo with significant effects even when HSV-tk-positive cells represented only 1% of the population . In vivo transduction with G1TkSvNa followed by GCV significantly inh ibited the development of PVR (p < 0.05). These results suggest that r etroviral vector-mediated transfer of HSV-tk into the proliferating ce lls in PVR may be feasible and may provide a novel therapeutic strateg y for this disease.