Strategies to optimize hepatic transduction of the gene therapy vector AAVAnc80

Abstract

The efficiency of recombinant adeno-associated virus (AAV) vectors transducing host cells is very low, limiting their therapeutic potential in patients. There are several cellular pathways interacting and interfering with the journey of the AAV from the cell surface to the nucleus, opening the possibility to enhance AAV transduction by modifying these interactions. In this study, we explored the results of AAV hepatic transduction when different mammalian Target of Rapamycin (mTOR) inhibitors, Rapamycin, MLN0128, RapaLink-1, were used in HepaRG spheroids and preconditioned infant, juvenile and adult mice. We found that maturation degree of hepatocytes affects the effect of the drugs. On the one hand, we observed that mTOR inhibition with any of the drugs is able to improve AAVAnc80 transduction in infant mice, although the effect is more robust when both mTOR complexes, mTORC1 and mTORC2, are blocked. On the other hand, we found Rapamycin as the only AAV hepatic transduction enhancer in juvenile and adult mice, whereas MLN0128 and RapaLink-1 interfered with AAV transduction. Therefore, our results show a complex interaction between the mTOR pathway and AAV-mediated hepatic transduction and indicate that mTOR inhibition is not a straightforward strategy for improving AAV transduction. Besides, as Rapamycin positive effect was found to be serotype-specific, we explored DDR disruption as an alternative to enhance AAV8 transduction and found that KU-55933-mediated ATM inhibition is able to transiently improve AAV8 transduction in a gender-derived manner. All these results expose that a better knowledge of the factors that restrict AAV cellular stabilization and regulate encoded transgene expression is essential to develop more potent AAV vectors able to achieve higher therapeutic effects and easier to translate into the clinic.