Virus-Mediated Transduction of Murine Retina with Adeno-Associated Virus: Effects of Viral Capsid and Genome Size

Abstract

Gene therapy vectors based on adeno-associated viruses (AAVs) show promise for the treatment of retinal degenerative diseases. In prior work, subretinal injections of AAV2, AAV5, and AAV2 pseudotyped with AAV5 capsids (AAV2/5) showed variable retinal pigmented epithelium (RPE) and photoreceptor cell transduction, while AAV2/1 predominantly transduced the RPE. To more thoroughly compare the efficiencies of gene transfer of AAV2, AAV3, AAV5, and AAV6, we quantified, using stereological methods, the kinetics and efficiency of AAV transduction to mouse photoreceptor cells. We observed persistent photoreceptor and RPE transduction by AAV5 and AAV2 up to 31 weeks and found that AAV5 transduced a greater volume than AAV2. AAV5 containing full-length or half-length genomes and AAV2/5 transduced comparable numbers of photoreceptor cells with similar rates of onset of expression. Compared to AAV2, AAV5 transduced significantly greater numbers of photoreceptor cells at 5 and 15 weeks after surgery (greater than 1,000 times and up to 400 times more, respectively). Also, there were 30 times more genome copies in eyes injected with AAV2/5 than in eyes injected with AAV2. Comparing AAVs with half-length genomes, AAV5 transduced only four times more photoreceptor cells than AAV2 at 5 weeks and nearly equivalent numbers at 15 weeks. The enhancement of transduction was seen at the DNA level, with 50 times more viral genome copies in retinas injected with AAV having short genomes than in retinas injected with AAV containing full-length ones. Subretinal injection of AAV2/6 showed only RPE transduction at 5 and 15 weeks, while AAV2/3 did not transduce retinal cells. We conclude that varying genome length and AAV capsids may allow for improved expression and/or gene transfer to specific cell types in the retina.

Adeno-associated virus terminal repeat (TR) mutant generates self-complementary vectors to overcome the rate-limiting step to transduction in vivo

“…A recent report has corroborated the efficiency of the scAAV vector in mouse retinal pigmented epithelium, where higher levels of transduction and faster onset were also reported. 9 In this report, we demonstrate the enhanced transduction potential of the scAAV vector in the liver and other tissues. A single injection of scAAV results in 25-50% transduction of liver cells.…”

Cellular tropism and transduction properties of seven adeno-associated viral vector serotypes in adult retina after intravitreal injection

“…3,6,8,12,24,25 Robust photoreceptor transduction has been reported after subretinal injection of many vector types; however, photoreceptors are only infrequently transduced after intravitreal injection of the serotypes tested to date. 3,4,[6][7][8]11,12,26 Intravitreal vector delivery is a less invasive technique compared with subretinal delivery. A larger vector volume can be delivered and this approach also allows repeated injections, and can thus be combined with the delivery of other pharmacotherapeutic agents.…”

Targeted ablation of Crb2 in photoreceptor cells induces retinitis pigmentosa

“…For photoreceptor-specific transduction via the subretinal route, an AAV2-based vector was packaged in AAV5 capsid (AAV2/5) (22). The AAV-Cre vectors were tested for potential toxicity by delivery of different numbers of genome copies (10 8 , 10 9 , 10 10 ) of AAV into wild-type retinas.…”