Enhanced Production of Exosome-Associated AAV by Overexpression of the Tetraspanin CD9.

Research on cell-free vesicles revealed a multitude of characteristics, in particular of microvesicles and exosomes, that range from their potential as biomarkers to a function in horizontal transfer of genetic information from cell to cell and also include supportive functions in viral infection. Exosome-associated adeno-associated viruses (exo-AAVs) are of particular interest for the past couple of years, because they introduced a new source of highly potent recombinant AAVs with improved features, including accelerated transduction rates and more efficient immune escape. However, key factors like the mode of action, efficiency of production, or engineering of exo-AAVs remain elusive to a large extent. Here, we used the established system of CD9 overexpression to boost the exosome output of AAV producing HEK-AAV cells. The CD9-powered high-exosome environment was established during exo-AAV1 production, and we could demonstrate that the yield of exo-AAVs dramatically increased when compared to standard exo-AAVs. Furthermore, we report that exo-AAV-CD9 was more efficient in transduction of cells in the same titer ranges as standard exo-AAVs. Our results provide a technological approach for the generation of exo-AAVs with superior performance.