Immune response to full-length dystrophin delivered to Dmd muscle by a high-capacity adenoviral vector

Adenoviral vector-mediated gene transfer to skeletal muscle is a promising potential treatment for Duchenne muscular dystrophy. However, the immunological response to viral antigens and the therapeutic protein expressed by the delivered gene could prevent effective treatment. In this study, we investigated the immune response induced by adenoviral and dystrophin antigens presented by high-capacity adenoviral vector-mediated dystrophin and beta-galactosidase delivery to skeletal muscle of a mouse model that is both dystrophin-deficient and lacZ transgenic. Direct intramuscular gene delivery of the high-capacity adenoviral vector encoding full-length murine dystrophin resulted in stable expression of recombinant dystrophin for 5 months in mice treated as neonates and for 4 weeks in mice treated as adults. We observed neutralizing antibody to adenoviral antigens only in mice treated as adults and not in mice treated as neonates. This suggested that adenoviral antigens were only presented at the time of vector administration when the neonatal immune system was not yet mature. In contrast, antibodies to dystrophin were observed both in mice treated as neonates and in mice treated as adults. The development of an anti-dystrophin antibody response in mice treated with the high-capacity adenoviral vector as neonates suggested that dystrophin antigens were presented to the immune system at a time remote from the gene delivery, when the immune system was mature. Interestingly, an antibody response against beta-galactosidase developed late in the course of mice treated with the high-capacity adenoviral vector as neonates, suggesting a loss of tolerance to beta-galactosidase, a self-antigen in these transgenic mice. Our results suggest that future human trials of dystrophin gene delivery will need to address the potential for immunity induced by ongoing segmental degeneration of partially treated muscle fibers and presentation of recombinant dystrophin antigens in the context of a Duchenne muscular dystrophy patient.