Title:
Vector innovation towards gene and cell-based therapies to treat muscular dystrophy

Speaker:
Takashi Okada, M.D., Ph.D.
Professor and Chairman
Department of Biochemistry and Molecular Biology, Nippon Medical School
t-okada(at)nms.ac.jp

Abstract:
The specific characteristics of the recombinant adeno-associated virus (rAAV) with safety and long-term expression have made it an attractive transduction tool for clinical gene therapy of neuromuscular diseases. Although host immune reaction against the vector as well as transgene products has been denoted in the clinical studies of neuromuscular gene therapy, there are accumulating cases of successful clinical studies. However, in vivo gene transduction with the rAAV depends upon laborious procedures for the production of the vector stocks to meet end-product specifications. We developed methods of producing rAAV with scalable purification using the high-performance ion exchange membrane adsorbers for considerable in vivo experimentation and clinical investigation. We adopted our production system to investigate AAV vector-mediated transduction strategy for the treatment of various neuromuscular diseases including Duchenne muscular dystrophy (DMD). Cardiac transduction of mdx dystrophic mice by the rAAV9-microdystrophin successfully improved fibrosis, EKG abnormalities as well as cardiac dysfunction. In contrast, muscle transduction with rAAV in normal Beagles and canine X-linked muscular dystrophy in Japan (CXMDJ) resulted in the transgene expression during a limited period. We initially transduced fetuses of CXMDJ with systemic administration of the rAAV9-microdystrophin to investigate therapeutic benefits of the microdystrophin in the canine model. Transduced dogs demonstrated long-term transgene expression with functional improvement. As a next step to induce acquired immunotolerance, mesenchymal multipotent stromal cells (MSCs) would be effective platform with immune modulation. Interestingly, intravenous injection of MSCs with lower dose of the rAAV9-microdystrophin greatly improved transgene expression as well as locomotive function in CXMDJ. These results suggest that long-term transgene expression with therapeutic benefits in neuromuscular disorders would be achieved by the rAAV-mediated transduction strategy with an adequate regimen to regulate host immure response.

References:
1 Sakai, A. et al., Nat. Commun. 2017, 5:16079
2 Tomono, T. et al., Mol. Ther. Methods Clin. Dev., 2016, 15058
3 Hayashita-Kinoh, H. et al., Mol. Ther., 2015, 23:627-37
4 Nitahara-Kasahara, Y. et al., Hum. Mol. Genet., 2014, 23:3990-4000
5 Arimura, S. et al., Science, 2014, 345:1505-8