RBP3 and coinfection: To assess if the weak PR transduction observed with the IRBP promoter was due to poor transcriptional activity of the promoter in the PRs or limited recombination upon co-infection of the three vectors, we compared the expression of the ED protein encoded by the triple AAV vectors to the expression by a single AAV vector containing the same expression cassette (Figures 5D and 5E; Figures S3 and S4).