Successful Liver transduction by Re-administration of Different Adeno-Associated Virus Vector Serotypes in Mice

Intravenous administration of adeno-associated virus (AAV) vector is a promising gene therapy approach for monogenic diseases. However, re-administration of the same AAV serotype is impossible due to the induction of anti-AAV neutralizing antibodies (NAbs). Here we examined the feasibility of re-administration of AAV vectors to change the serotypes. We administered AAV3B, AAV5, or AAV8 vectors targeting the liver of C57BL/6 mice intravenously, and then assessed the emergence of NAbs and the transduction efficacy with a second administration. For all serotypes, we confirmed that re-administration with the same serotype was not possible. Although the highest neutralizing activity of NAb was induced by AAV5; however, the NAbs elicited by AAV5 did not react with any other serotypes, resulting in success in re-administration with the other serotypes. The re-administration of AAV5 was also successful in all mice treated with AAV3B and AAV8. The effective secondary administration of AAV3B and AAV8 was observed in most mice treated with AAV8 and AAV3B, respectively. However, few mice developed NAbs cross-reactive with the other serotypes, especially the serotypes with close sequence homology. In summary, AAV vector administration induced NAbs relatively specific to the serotype administrated. Secondary administration of AAVs targeting liver transduction could be successfully achieved by switching AAV serotypes in mice. ### Competing Interest Statement The authors have declared no competing interest.