Enhanced expression of recombinant dystrophin following intramuscular injection of Epstein-Barr virus (EBV)-based mini-chromosome vectors in mdx mice

Gene transfer by direct intramuscular injection of naked plasmid DNA has be en shown to be a safe, simple but relatively inefficient method for gene de livery in vivo. Eukaryotic plasmid expression vectors incorporating the Eps tein-Barr virus (EBV) origin of replication (oriP) and EBNA1 gene have been shown to act as autonomous episomally replicating gene transfer vectors wh ich additionally provide nuclear matrix retention functions. Prolonged expr ession of a LacZ reporter gene and recombinant human dystrophin was shown u sing EBV-based plasmid vectors transfected into C2C12 mouse myoblast and my otube cultures. Intramuscular injection of EBV-based dystrophin expression plasmids into nude/mdx mice resulted in significant enhancement in the numb er of mus-resulted in significant enhancement in the number of muscle fibre s expressing recombinant dystrophin compared with a conventional vector. Th is effect was observed for over 10 weeks after a single administration. The se results indicate the potential advantage of EBV-based expression vectors for focal plasmid-mediated gene augmentation therapy in Duchenne muscular dystrophy (DMD) and a range of other gene therapeutic applications.