Adeno-Associated Virus Type 5: Transduction Efficiency and Cell-Type Specificity in the Primate Retina

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Abstract
Gene transfer using adeno-associated viruses (AAVs) has been effective for treating inherited retinal diseases in animal models. Further evaluation in primates must be performed prior to clinical application, however, because of the difference between the retina of the primate and those of other animals. Prior work has shown that AAV2 can transduce rod-photoreceptor and RPE cells in the non-human primate retina and that AAV5 is more efficient at transducing photoreceptor cells than AAV2 in the rodent retina. In this study, we evaluated the efficiency of AAV5 in the non-human primate retina after subretinal injections of the vector to distinct anatomic retinal regions (superior, inferior, nasal, macula, temporal). rAAV5 led to a rapid onset of transgene expression (within 2 weeks), with expression persisting up to 10 months. Postoperative electrophysiology studies showed that global retinal function was preserved following gene transfer. Quantitative analysis of gene transfer demonstrated a maximum transduction efficiency of 22% in the injected areas. Evaluation of cell types using confocal microscopy and cone-specific antibodies revealed that AAV5, expressing reporter genes from the cytomegalovirus (CMV) promoter/enhancer, preferentially transduced rods. No significant differences were found in the regional tropism of AAV5 among the five areas injected despite variation in retinal topography. Immunohistochemical studies revealed that the AAV5 receptor, PDGFR-A, is localized to the outer segments of rods but not cones providing a basis for the observed tropism. Our results support the utility of AAV5 for rod photoreceptor degeneration therapies.