Engineered AAV2.7m8 serotype shows significantly higher transduction efficiency of ARPE-19 and HEK293 cell lines compared to AAV2/5, 2/8 and 2/9 serotypes

The level of transduction efficiency of target retinal cells affects the choice of AAV serotype and the outcome of gene replacement therapy for inherited retinal diseases (IRDs). While AAV2 serotype was used in the first approved ocular gene therapy Luxturna, AAV2/8 and AAV2/5 capsids later demonstrated high tropism to retina cells. This study focused on tropism, efficacy and rate of viral invasion of rAAV 2.7m8, 2/5, 2/8 and 2/9 expressing GFP in ARPE-19 and HEK293 cell lines. GFP expression was assessed bi-hourly by live imaging microscopy IncuCyte S3. Within 12 hours, AAV2.7m8 demonstrated highest transduction efficiency at four viral concentrations (1×10⁴, 3×10⁴, 6×10⁴ and 8×10⁴ VG/cell) in dose-dependent manner followed by AAV2/5 in ARPE-19 and AAV2/9 in HEK293 cells. The efficiency by AAV2.7m8 at the dose of 6×10⁴ VG/cell was 20, 201 and 323 times higher in ARPE-19 cells and 324, 99 and 52 times higher in HEK293 cells than that of AAV2/5, AAV2/8 and AAV2/9, respectively. This trend remained for 4.5 days at all viral concentrations as additionally shown by flow cytometry. At the dose of 6×10⁴ VG/cell, AAV2.7m8 (63% GFP⁺ cells) was nearly 3 and 10 times as efficient as AAV2/5 (22% GFP⁺ cells) and AAV2/9 or AAV2/8 (10% and 8%), respectively, in ARPE-19 cells. Thirty-three percent of HEK293 cells transduced by AAV2.7m8 were GFP⁺, followed by AAV2/9 (10%), AAV2/8 (9%) and AAV2/5 (3%). Thus, AAV2.7m8 demonstrated itself as the most efficient delivery tool which should be utilised for such IRDs treatment as RDH12-associated retinopathy.