Abstract
Purpose: :
Three promoters that included, a 500 bp of the proximal mouse opsin promoter (mOp500), the human G-protein couple receptor protein kinase 1 promoter (hGRK1), and the cytomegalovirus immediate early enhancer combined with the chicken beta actin proximal promoter CBA), were evaluated for their specificity and robustness in driving the expression of the green fluorescent protein (GFP) reporter gene in rods, when packaged in a recombinant Adeno-associated viral vector of serotype 5 (AAV5), and delivered via subretinal injection to the normal adult canine retina.
Methods: :
Retinas injected with different concentrations of the 3 viral vector constructs were processed for conventional histology and immunohistochemistry to assess location and intensity of GFP expression.
Results: :
Photoreceptor specific promoters (mOP500, hGRK1) targeted robust GFP expression to rods, while the ubiquitously expressed CBA promoter led to transgene expression in the retinal pigment epithelium, rods, cones and rare Müller, horizontal and ganglion cells. Late onset inflammation was frequently observed both clinically and histologically with all three constructs when the highest viral titers were injected (~ 1012-1013 vg/ml). A peculiar finding observed with both the hGRK1 and CBA promoters was the occurrence of cone loss in the injected regions of the retinas that received the highest titers.
Conclusions: :
Efficient and specific rod transduction, together with preservation of retinal structure was achieved with both mOP500 and hGRK1 promoters when viral titers in the order of 1011 vg/ml were delivered.
Keywords: gene transfer/gene therapy • retina • photoreceptors