Feline immunodeficiency virus vectors. Gene transfer to mouse retina following intravitreal injection

Background: Transduction of the murine retinal pigmented epithelium (RPE) with adenovirus vectors requires technically difficult and invasive subretinal injections. This study tested the hypothesis that recombinant vectors based on feline immunodeficiency virus (FIV) could access the retina following intravitreal injection.

Methods: FIV vectors expressing E. coli beta-galactosidase (FIVbetagal) were injected alone, or in combination with adenovirus vectors expressing eGFP, into the vitreous of normal mice and eyes evaluated for transgene expression. In further studies, the utility of FIV-mediated gene transfer to correct lysosomal storage defects in the anterior and posterior chambers of eyes was tested using recombinant FIV vectors expressing beta-glucuronidase. FIVbetagluc vectors were injected into beta-glucuronidase-deficient mice, an animal model of mucopolysacharridoses type VII.

Results: The results of this study show that similar to adenovirus, both corneal endothelium and cells of the iris could be transduced following intravitreal injection of FIVbetagal. However, in contrast to adenovirus, intravitreal injection of FIVbetagal also resulted in transduction of the RPE. Immunohistochemistry following an intravitreal injection of an AdeGFP (adenovirus expressing green fluorescent protein) and FIVbetagal mixture confirmed that both viruses mediated transduction of corneal endothelium and cells of the iris, while only FIVbetagal transduced cells in the retina. Using the beta-glucuronidase-deficient mouse, the therapeutic efficacy of intravitreal injection of FIVbetagluc (FIV expressing beta-glucuronidase) was tested. Intravitreal injection of FIVbetagluc to the eyes of beta-glucuronidase-deficient mice resulted in rapid reduction (within 2 weeks) of the lysosomal storage defect within the RPE, corneal endothelium, and the non-pigmented epithelium of the ciliary process. Transgene expression and correction of the lysosomal storage defect remained for at least 12 weeks, the latest time point tested.

Conclusion: These studies demonstrate that intravitreal injection of FIV-based vectors can mediate efficient and lasting transduction of cells in the cornea, iris, and retina.