Equine infectious anemia virus (EIAV) is a nonprimate lentivirus that does not cause human disease. Subretinal injection into mice of a recombinant EIAV lentiviral vector in which lacZ is driven by a CMV promoter (EIAV CMV LacZ) resulted in rapid and strong expression of LacZ in retinal pigmented epithelial (RPE) cells and some other cells including ganglion cells, resulting in the presence of 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside within the optic nerve. Substitution of the RPE-specific promoter from the vitelliform macular dystrophy (VMD2) gene for the CMV promoter resulted in prolonged (at least 1 year) expression of LacZ that was restricted to RPE cells, albeit reduced 6- to 10-fold compared with the CMV promoter. Similarly, the amount of FLAG-tagged endostatin detected in eyes injected with the EIAV VMD2 Endo(FLAG) vector was similar to that seen in eyes injected with a vector that expressed both endostatin and angiostatin [EIAV VMD2 Endo(FLAG)/Angio]; expression was approximately 6-fold lower than with identical vectors in which the CMV promoter drove expression. Compared with murine eyes treated with a control EIAV vector, subretinal injection of EIAV vectors expressing murine endostatin alone or in combination with angiostatin driven by either the CMV or VMD2 promoter caused significant suppression of choroidal neovascularization (NV) at laser-induced rupture sites in Bruch's membrane. These data support proceeding toward clinical studies with EIAV-based gene therapy for choroidal NV, using the VMD2 promoter to selectively drive expression of a combination of endostatin and angiostatin in RPE cells.
