5 years of successful inducible transgene expression following locoregional AAV delivery in nonhuman primates with no detectable immunity.

Anti-transgene immune responses elicited after intramuscular (IM) delivery of recombinant Adeno-Associated Viruses (rAAV) have been shown to hamper long-term transgene expression in large animal models of rAAV-mediated gene transfer. To overcome this hurdle, we and others described an alternative mode of delivery of rAAV vectors in nonhuman primate muscles: the locoregional intravenous route of administration (LR). Using this injection mode, we previously reported in cynomolgus monkeys a persistent inducible transgene expression for at least 1 year under the control of the tetracycline-inducible TetON system, with no immunity against the rtTA transgene product. The present study shows the long-term follow-up of these animals. We report that LR delivery of a rAAV2/1 vector allows long term inducible expression up to at least 5 years post-gene transfer with no any detectable host immune response against the transactivator rtTA despite its immunogenicity following IM gene transfer. This study shows for the first time a long-term regulation of muscle gene expression using TetON-inducible system in a large animal model. Moreover, these findings further confirm that rAAV LR delivery route is efficient and immunologically safe, allowing long-term skeletal muscle gene transfer.