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

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.

Targeting gene expression to cones with human cone opsin promoters in recombinant AAV

“…31,32 For example, transduction of both RPE and photoreceptor cells can be achieved by subretinal injection of either AAV2 or AAV5; however, the efficiency of transduction appears much greater with AAV5, especially in photoreceptors. 33,34 The aim of this project was to evaluate various human cone opsin promoters for their specificity and efficacy to target gene expression to the canine cone photoreceptors. We were able to successfully target gene expression to the canine L/M cones using the human red cone opsin promoter PR2.1 in rAAV5.…”

Recombinant AAV-mediated gene transfer to the retina: gene therapy perspectives

“…19 A recent study has shown that in primates, rAAV-5/5 also has preferential tropism for rod photoreceptors. 29 For chimeric vectors rAAV-2/5 and rAAV-2/4, subretinal injection in dogs results in stable expression of GFP for more than 18 months (Rolling et al, data not shown), with the tropism being identical to the one observed in the rat: transduction of RPE and photoreceptor cells with type 5 and exclusive transduction of RPE with type 4. 26 …”

Gene Therapy for Choroideremia Using an Adeno-Associated Viral (AAV) Vector

“…There may also be promoter-serotype interactions. AAV5, for example, does not transduce macaque primate cones effectively with the CMV promoter (Lotery et al 2003), but it is effective in cones of the squirrel monkey when using a cone-specific promoter (Mancuso et al 2007). It is impossible to precisely predict whether AAV2 will limit photoreceptor gene expression exclusively to rod photoreceptors in any given human retinal degeneration; however, it is probably safe to say that AAV2 will target rods more effectively than cones in humans.…”