Abstract: “MAAP” is a naturally-occurring, newly-discovered about 13 KDa adeno-associated vims protein. It is not homologous to known proteins. When AAV producer cells are cultured for more than 24 hours, we found that inactivating translation of the full-length MAAP improves the productivity of the transfected producer cells. The resulting AAV viruses are also of better quality and more stable. Our findings thus provide a way to improve the industrial manufacture of recombinant adeno-associated virus gene therapy vectors.