Therapeutic gene delivery to the whole spinal cord is a major challenge for the treatment of motor neuron (MN) diseases. Systemic administration of viral gene vectors would provide an optimal means for the long-term delivery of therapeutic molecules from blood to the spinal cord but this approach is hindered by the presence of the blood-brain barrier (BBB). Here, we describe the first successful study of MN transduction in adult animals following intravenous (i.v.) delivery of self-complementary (sc) AAV9 vectors (up to 28% in mice). Intravenous MN transduction was achieved in adults without pharmacological disruption of the BBB and transgene expression lasted at least 5 months. Importantly, this finding was successfully translated to large animals, with the demonstration of an efficient systemic scAAV9 gene delivery to the neonate and adult cat spinal cord. This new and noninvasive procedure raises the hope of whole spinal cord correction of MN diseases and may lead to the development of new gene therapy protocols in patients.
Duchenne muscular dystrophy (DMD) is an incurable X-linked muscle-wasting disease caused by mutations in the dystrophin gene. Gene therapy using highly functional microdystrophin genes and recombinant adeno-associated virus (rAAV) vectors is an attractive strategy to treat DMD. Here we show that locoregional and systemic delivery of a rAAV2/8 vector expressing a canine microdystrophin (cMD1) is effective in restoring dystrophin expression and stabilizing clinical symptoms in studies performed on a total of 12 treated golden retriever muscular dystrophy (GRMD) dogs. Locoregional delivery induces high levels of microdystrophin expression in limb musculature and significant amelioration of histological and functional parameters. Systemic intravenous administration without immunosuppression results in significant and sustained levels of microdystrophin in skeletal muscles and reduces dystrophic symptoms for over 2 years. No toxicity or adverse immune consequences of vector administration are observed. These studies indicate safety and efficacy of systemic rAAV-cMD1 delivery in a large animal model of DMD, and pave the way towards clinical trials of rAAV–microdystrophin gene therapy in DMD patients.
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