Development of an innovative immune stealth gene transfer platform to escape the activation of host’s immunity to AAV vectors – ESCAPE

In vivo gene therapy using recombinant adeno-associated viral vectors (rAAV) showed promising benefits for the treatment of genetic disorders as illustrated by Luxturna®, Glybera® and Zolgensma® FDA and EMA approvals. However, there are still scientific locks to overcome for a successful clinical translation of such innovative biotherapies such as their immunogenicity in patients. Indeed, since protocols evolved from local to systemic delivery of high doses of vector, adverse events related to the immune system activation have been reported in treated patients, resulting in some cases in regulatory holds of clinical trials. In this study, we aim at understanding, predicting and preventing these immune responses through the development of an innovative immune stealth AAV gene transfer platform able to escape the activation of host’s immunity. So far, the cellular immune response to AAV capsid is determined by measuring IFN? secretion after lymphocyte restimulation. Here, we will perform a multiparametric cytokine analysis and immune cell phenotyping on a large cohort of healthy donors towards AAV serotypes used in current clinical trials. This screening will allow the collection of an unprecedent data set to determine the immune signature of these cells. Using this data collection, we also aim at developing modelling algorithms to help predicting the impact of the immune response after gene transfer based on patient’s HLA type and phenotype of preexisting T cells. In addition, we will engineer rAAV immune stealth vectors by adding DNA-based immunomodulatory sequences to the vector genome and evaluate this approach in vitro and in vivo in relevant humanized rodent models of AAV immunogenicity generated in the lab. Development of such immunomodulation strategies will increase the efficacy and safety of AAV gene therapy products by preventing the initiation of deleterious immune responses while avoiding the administration of immunosuppressive nonspecific drugs.