1. ¹Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA
2. ²Center for Molecular Medicine, University of Cologne, Cologne, Germany
3. ³Division of Gene Therapy, University of Ulm, Ulm, Germany
4. ⁴Neurology Service, Department of Veterans Affairs Medical Center, Pittsburgh, PA, USA

Correspondence: Dr PR Clemens, Department of Neurology, University of Pittsburgh, Room S-520 Biomedical Science Tower, Pittsburgh, PA 15213, USA

⁵These authors contributed equally to this work

Received 20 February 2004; Accepted 27 August 2004; Published online 14 October 2004.

Abstract

In utero gene delivery could offer the advantage of treatment at an early stage for genetic disorders such as Duchenne muscular dystrophy (DMD) in which the inevitable process of muscle degeneration is already initiated at birth. Furthermore, treatment of fetal muscle with adenoviral (Ad) vectors is attractive because of a high density of Ad receptors, easy vector accessibility due to immaturity of the basal lamina and the possibility of treating stem cells. Previously, we demonstrated the efficient transduction of fetal muscle by high-capacity Ad (HC-Ad) vectors. In this study, we compared HC-Ad and first-generation Ad (FG-Ad) vectors for longevity of lacZ transgene expression, toxicity and induction of immunity after direct vector-mediated in utero gene delivery to fetal C57BL/6 mice muscle 16 days after conception (E-16). The total amount of -galactosidase (gal) expressed from the HC-Ad vector remained stable for the 5 months of the study, although the concentration of gal decreased due to muscle growth. Higher survival rates that reflect lower levels of toxicity were observed in those mice transduced with an HC-Ad vector as compared to an FG-Ad vector. The toxicity induced by FG-Ad vector gene delivery was dependent on mouse strain and vector dose. Animals treated with either HC-Ad and FG-Ad vectors developed non-neutralizing antibodies against Ad capsid and antibodies against gal, but these antibodies did not cause loss of vector genomes from transduced muscle. In a mouse model of DMD, dystrophin gene transfer to muscle in utero using an HC-Ad vector restored the dystrophin-associated glycoproteins. Our results demonstrate that long-term transgene expression can be achieved by HC-Ad vector-mediated gene delivery to fetal muscle, although strategies of vector integration may need to be considered to accommodate muscle growth.