Abstract
Purpose :
Most retinal degenerative diseases, including retinitis pigmentosa and age-related macular degeneration, are characterized by a progressive loss of photoreceptors. Various adeno-associated virus (AAV)-based gene therapies to prevent or slow down retinal degeneration target the photoreceptor cells. Typically, AAVs are injected subretinally. This restricts therapeutic intervention to the injection site and often results in a decrease in retinal thickness and visual acuity. Intravitreal injection is a safer method and targets cells along the entire width of the retina. Therefore, AAV vectors are developed that possess the ability to penetrate through the retina when applied intravitreally.
Methods :
To develop AAV2 vectors with good retinal penetration abilities following intravitreal delivery, we applied an in vivo directed evolution strategy using a novel peptide display design that enabled us to iteratively enrich AAV2 variants with the desired properties. After four selection rounds we determined and ranked the receptor-binding motifs of the converged library by next-generation sequencing.
Results :
Fifteen synthetic capsids containing the top-ranked motifs were subsequently analysed for their transduction fingerprints following intravitreal injection into wildtype C57/BL6 mouse eyes. For evaluation, a transgene encoding the green fluorescent protein mCitrine under the ubiquitous CMV and EF1a promoters was packaged into the novel capsids. The in vivo expression screen resulted in three synthetic AAV capsids with much improved transretinal penetration abilities compared to wildtype AAV2, mediating panretinal mCitrine expression.
Conclusions :
Our novel synthetic AAV2 capsids may have clinical relevance for the implementation of photoreceptor-targeted gene therapies, but also optogenetic approaches targeting dormant photoreceptors or inner retinal cells.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.