Factors governing the transduction efficiency of adeno-associated virus in the retinal ganglion cells following intravitreal injection

Efficient transduction of the retinal ganglion cells (RGCs) is a prerequisite to maximize therapeutic outcomes in any form of gene therapy for optic neuropathies. Whereas subretinal injection of adeno-associated virus 2 (AAV2) has been well-characterized, the serotype, viral load, and promoter combinations that govern RGC transduction efficiency following intravitreal injection remains poorly understood. We evaluated the transduction efficiency of seven AAV2 serotypes (AAV2/1, AAV2/2, AAV2/4, AAV2/5, AAV2/6, AAV2/8, and AAV2/9) for the RGCs at 4 weeks following intravitreal injection in C57BL/6J mice. Intravitreal injection of 1 x 10(9) vg of AAV2/2 with eGFP driven by the CMV promoter attained a higher transduction efficiency for the RGCs (60.0 +/- 4.2%) compared with the six other AAV2 serotypes with eGFP driven by the same promoter injected at the same viral load (< 3.0%). Reporter driven by the CAG promoter had a lower transduction efficiency (up to 42.0 +/- 5.8%) compared with that driven by the CMV reporter (60.0 +/- 4.2%, p <= 0.024). There was a viral dose-dependent transduction effect of AAV2/2-CMV-eGFP and the transduction efficiency was 40.2 +/- 3.9%, 16.6 +/- 4.2%, and 2.6 +/- 0.2% when the viral load decreased to 5 x 10(8) vg, 1 x 10(8) vg, and 1 x 10(7) vg, respectively. Optimizing viral serotype, viral load, and promoter construct of AAV2 is important to maximize transgene expression in RGC-targeted gene therapy.