Helper-dependent adenovirus for the gene therapy of proliferative retinopathies: stable gene transfer, regulated gene expression and therapeutic efficacy.
BACKGROUND
Ocular neovascular disorders, such as diabetic retinopathy and age-related macular degeneration, are the principal causes of blindness in developed countries. Current treatments are of limited efficacy, whereas a therapy based on intraocular gene transfer of angiostatic factors represents a promising alternative. For the first time we have explored the potential of helper-dependent adenovirus (HD-Ad), the last generation of Ad vectors, in the therapy of retinal neovascularization.


METHODS
We first analyzed efficiency and stability of intraretinal gene transfer following intravitreous injection in mice. A HD-Ad vector expressing green fluorescent protein (GFP) under the control of the cytomegalovirus (CMV) promoter (HD-Ad/GFP) was compared with a first-generation (E1/E3-deleted) Ad vector carrying an identical GFP expression cassette (FG-Ad/GFP). We also constructed HD-Ad vectors expressing a soluble form of the VEGF receptor (sFlt-1) in a constitutive (HD-Ad/sFlt-1) or doxycycline (dox)-inducible (HD-Ad/S-M2/sFlt-1) manner and tested their therapeutic efficacy upon intravitreous delivery in a rat model of oxygen-induced retinopathy (OIR).


RESULTS
HD-Ad/GFP promoted long-lasting (up to 1 year) transgene expression in retinal Müller cells, in marked contrast with the short-term expression observed with FG-Ad/GFP. Intravitreous injection of HD-Ad vectors expressing sFlt-1 resulted in detectable levels of sFlt-1 and inhibited retinal neovascularization by more than 60% in a rat model of OIR. Notably, the therapeutic efficacy of the inducible vector HD-Ad/S-M2/sFlt-1 was strictly dox-dependent.


CONCLUSIONS
HD-Ad vectors enable stable gene transfer and regulated expression of angiostatic factors following intravitreous injection and thus are attractive vehicles for the gene therapy of neovascular diseases of the retina.
I.R.B.M., Via Pontina Km. 30,600, 00040 Pomezia (Rome), Italy.
Stefania
S
Lamartina
Monica
M
Cimino
Giuseppe
G
Roscilli
Ernesta
E
Dammassa
Domenico
D
Lazzaro
Rossella
R
Rota
Gennaro
G
Ciliberto
Carlo
C
Toniatti
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D004318:Doxycycline / Q000494:pharmacology; D005786:Gene Expression Regulation; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000008:administration & dosage; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006378:Helper Viruses / Q000235:genetics*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D051379:Mice; D023421:Models, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000378:metabolism / Q000473:pathology; D015861:Retinal Neovascularization / Q000628:therapy*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000378:metabolism
D042461:Vascular Endothelial Growth Factor A; D049452:Green Fluorescent Proteins; C501163:Flt1 protein, mouse; D040281:Vascular Endothelial Growth Factor Receptor-1; D004318:Doxycycline