1. Measles Virus Glycoprotein Pseudotyped Lentiviral Vectors Transduce Cytokine Stimulated and Resting Hematopoietic Stem Cells at an Efficiency Without Precedent

Abstract

Immune responses against recombinant AAV (rAAV) capsid are a major concern in clinical trials. It was first described in hemophilic patients injected by intrahepatic delivery that AAV capsids elicited a cytotoxic lymphocyte response leading to clearance of transduced hepatocytes. On the other hand, intramuscular delivery of rAAV1 in humans induced a tolerogenic response against rAAV capsid mediated by regulatory T cells leading to stable expression in patients for more than 3 years. Several parameters could modulate this response and among them the mode of delivery. While transfer to the intact CNS has been shown to elicit a minimal T cell-mediated response without a salient plasma cell-mediated immune response in preclinical animal studies, these data are lacking in primate studies after intrathecal (IT) injection. In our study, African Green primates were injected intrathecally with a serotype 10 AAV vector (AAVrh10), described to transduce efficiently the central nervous system (CNS), expressing artificial miRNAs against superoxide dismutase 1 (SOD1) as a therapy for familial amyotrophic lateral sclerosis (ALS). This vector was administered at a dose of 6e12 viral genomes per kilogram modeled directly off the anticipated dose per patient in the clinical trial and based on IT rAAV delivery in primate studies showing robust cortical and spinal cord transduction. We are currently characterizing what type of immune response is elicited against the AAV capsid after IT delivery. A particular interest will be given to cytokine secretion mediated by restimulated T lymphocytes in vitro and to neutralizing antibodies directed against AAVrh10 and their potential crossreactivity to other serotypes. In addition to the proof-of-concept of knockdown and spread of AAV vector after delivery to the CNS of primates, this study is important for the safety of IT delivery in large animal models before translation to human clinical trials.