Sodium Chloride and Potassium Chloride Mediate Log-increase in AAV Viral Vector Particle and Infectious Titers in a Specific and Timely Manner when Using the HSV Production Platform

Abstract The increasing demand for adeno-associated viral vectors, a result from the surging interest for their potential to cure human genetic diseases by gene transfer, tumbled on low performing production systems. Innovative improvements to increase both yield and quality of the vector produced has become a priority undertaking in the field. In a previous study, we showed that adding a specific concentration of sodium chloride to the production medium resulted in a dramatic increase of AAV vector particle and infectious titers when using the HSV production system, both in adherent or suspension platforms. In this work, we studied additional salts and their impact on AAV vector production. We found that potassium chloride, or a combination of potassium and sodium chloride resulted in the highest increase in AAV vector production. We determined that the salt-mediated effect was the most impactful when the salt was present between eight to approximately sixteen hours post-infection, with the highest rate increase occurring within the first 24 hours of the production cycle. We showed that the AAV vector yield increase did not result from an increase in cell growth, size or viability. Further we demonstrated that the impact on AAV vector production was specifically mediated by NaCl and KCl independently of their impact on the osmolality of the production media. Our findings convincingly showed that NaCl and KCl were uniquely efficacious to promote up to 10-fold increase in the production of highly infectious AAV vectors when produced in the presence of HSV. We believe this study will provide unique, novel and important new insights in AAV biology toward the establishment of more successful production protocols.