Tropism and Retinal Transduction Efficiency of Adeno-Associated Virus Serotypes in Mice

Adeno-associated viruses (AAVs) have become the preferred vector for gene therapy in ophthalmology. However, requirements for specific cell surface receptors limit AAV-mediated retinal cell transduction efficiency. This led to the need to engineer novel AAV vectors for widespread retinal transduction and transgene expression. However, no comparative analyses of these novel AAV serotypes have been reported. Here, we compare the retinal transduction efficiency of four novel AAV serotypes in wild-type mice retina after intravitreal and subretinal injections.

In total, 1.0 µL each of the four different AAV/cytomegalovirus/enhanced green fluorescent protein (EGFP) synthetic serotypes (1 × 109 genome copies [GC]/eye) was delivered by intravitreal or subretinal injection into mouse eyes. Tropism of each serotype to efficiently transduce photoreceptor (PR) and retinal pigment epithelial (RPE) cells was examined by EGFP expression using fundoscopy and immunolabeling 1 and 2 months after administration. Retinal function was evaluated using electroretinography and optomotor kinetics.

Fundoscopy and immunolabeling of EGFP in both subretinally and intravitreally injected AAV/DJ and AAV/DJ8 retinas showed the highest transduction efficiency. Compared to intravitreal delivery, all serotypes successfully transduced PR and RPE cells after subretinal injections. However, only intravitreally delivered AAV27m8, AAV/DJ, and AAV/DJ8 efficiently transduce PRs. AAV/DJ8 exhibited the highest PR and RPE transduction of the four serotypes. Visual function was unaffected, and adverse immunologic responses were not observed between the serotype and the PBS-injected eye.

Synthetic AAV serotypes differentially transduced PR and RPE cells depending on the delivery route. AAV/DJ8 exhibited the most efficient transduction of PR and RPE cells when injected intravitreally.