Recombinant AAV-mediated delivery of a tet-inducible reporter gene to the rat retina

Viral delivery of neurotrophins or other therapeutic genes is an attractive option for treating retinal degeneration. Regulated expression of these ge nes in the retina is needed to aid in dose delivery and to promote safety. To evaluate whether tetracycline (tet)-inducible transgenes encapsidated in recombinant adeno-associated viruses (rAAV) can provide controlled gene ex pression in vitro and in the rat retina, two viruses were constructed: a si lencer/activator vector and an inducible doxycycline (dox)-responsive GFP v ector. Combinations of these two viruses were subretinally injected into wi ld-type rats and dox was orally administered through the drinking water. Re tinal GFP expression was monitored in vivo with a noninvasive fluorescence imaging method. Eyes were also examined by histology, Western analysis, and electroretinography. Subretinal injection of rAAV efficiently delivers ind ucible genes to both photoreceptors and retinal pigment epithelial cells. G FP expression was initially observed 1 week postinduction, and GFP protein was undetectable after removal of dox. In uninduced animals, GFP expression was negligible. The dox dosage was varied in vivo and showed a correlation to the level of GFP expression. Thus, transduction of retinal cells with t et-inducible vectors allows for tight regulation of gene expression.