Efficient gene transfer into retinal cells using adenoviral vectors: dependence on receptor expression

A number of ocular diseases are potentially amenable to gene therapy interventions if appropriate vectors for the targeted administration of therapeutic genes can be identified. In vitro and in vivo transduction efficiency of a Group C serotype 5 adenoviral vector containing the fiber domain derived from a Group B serotype 35 adenovirus and the gene encoding green fluorescent protein (AdV5/F35-GFP) was compared to an AdV5-GFP vector for transgene delivery to human retinoblastoma and to human and murine retinas.

The distribution of the adenoviral receptors CAR and CD46 on normal and malignant retinal tissues was determined using immunohistochemistry. Human retinoblastoma cells were incubated with either AdV5-GFP or AdV5/F35-GFP, and the expression of the reporter protein was compared using quantitative fluorescence and fluorescent-activated cell sorting. Mice were given a single subretinal injection of either viral vector, and eyes were enucleated at specified times after injection for histopathologic examination. Human cadaver eyes were similarly examined ex vivo.

CAR was expressed in retina except in photoreceptor outer segments. CD46 was expressed in photoreceptor inner and outer segments. Both vectors efficiently transduced the human retinoblastoma cells in vitro. However, the amount of the transgene expressed using AdV5/F35-GFP was more than sixfold greater than that when AdV5-GFP was used. In vivo, AdV5/F35-GFP at doses as low as 10(5) infectious units (IU) transduced cells in all layers of the retina especially photoreceptors and occasional neuronal cells, and Müller cells as well as retinal pigment epithelial cells, whereas AdV5-GFP transduced only retinal pigment epithelial cells and occasional photoreceptors and Müller cells.

AdV5/F35 chimeric vectors may be superior to AdV5 for gene therapy applications targeting the photoreceptor.