Adeno-Associated Virus serotype 6 (AAV6) appears to be related to AAV1 by sequence analysis and shows the best transduction efficiency in pancreatic beta-cells compared to other AAV serotypes.These AAV6 particles constitutively express the firefly (Photinus pyralis) luciferase and mCherry genes connected via a T2A linker, under the control of a CMV promoter. The T2A self-cleaving peptide (derived from Thosea asigna virus 2A) leads to the efficient cleavage of the transcript and expression of luciferase and mCherry as two separate proteins.