Retinal transduction profiling of diverse AAV serotypes via intravitreal injection.

Abstract

Optimizing adeno-associated virus (AAV) capsid and dosing selection is critical for the clinical translation of retinal gene therapy. This study aims to provide a comprehensive reference by comparing the transduction efficiency, cellular tropisms, and temporal retinal expression patterns of various AAV serotypes for intravitreal retinal gene therapy. A series of AAV vectors were intravitreally injected into C57BL/6J mice. Retinal tissues were harvested 4 weeks post-injection to evaluate the transgene expression and cellular tropisms by immunostaining. Both ssAAV2.NN and scAAV2.NN vectors at a dose escalation were administered, with similar assessments conducted at 2 and 4 weeks post-injection. Additionally, the early-phase retinal transduction profiles of AAV vectors were detected at multiple time points within 12 weeks following administration. Stronger green fluorescent protein (GFP) fluorescence was observed in retinas intravitreally transduced with AAV2.NN, AAV2.GL, and AAV8 vectors, with AAV2.GL showing greater co-localization with GS⁺ Müller cells and axons. Compared to ssAAV2.NN, scAAV2.NN vectors resulted in higher GFP fluorescence, despite similar transfected cell percentages (except for its increased co-labeling with Calbindin⁺ horizontal cells). A dose-dependent level of GFP fluorescence was noted in scAAV2.NN vectors, with greater co-labeling with Rbpms⁺ retinal ganglion cells at high doses. Interestingly, GFP fluorescence was detectable as early as 3 days post-injection in both ssAAV2.NN and scAAV2.NN vectors, with no prominent differences in the intensity until day 7. AAV2.GL vectors achieved higher transgene expression and broader cellular transduction via the intravitreal route. scAAV2.NN vectors presented stronger transgene expression in a dose-dependent manner. The transgene expression from both ssAAV2.NN and scAAV2.NN vectors can be detected as early as 3 days post-injection. Our study provides key insights for early-stage monitoring and vector and dosage selection in future clinical application for intravitreal gene therapy.

Importance: The retinal transduction efficiency and cellular tropisms of serial AAV serotypes, including AAV2, AAV2.7m8, AAV2.NN, AAV2.GL, AAV8, AAV11, and AAV.SPR, were simultaneously and unbiasedly quantified and compared following intravitreal injection. Transgene fluorescence was detectable in cells as early as 3 days post-injection in retinas intravitreally transduced with both ssAAV2.NN and scAAV2.NN vectors. The timeliness of the onset and level of transgene expression in retinas intravitreally transduced with ssAAV2.NN and scAAV2.NN vectors were characterized during the early phase post-injection. Differences in retinal transduction efficiency and cellular tropisms of scAAV2.NN vectors at varying doses via intravitreal injection are described.