1. ¹Institut National de la Santé et de la Recherche Médicale (INSERM), S UMR 787, Groupe Myologie, INSERM-Université Pierre et Marie Curie–Paris VI, Paris, France
2. ²Centre National de la Recherche Scientifique UMR 8115, Genethon, Evry, France
3. ³INSERM U580, Hôpital Necker-Enfants Malades, Paris, France
4. ⁴Department of Physiology, Anatomy and Genetics, Henry Wellcome Centre for Gene Function, University of Oxford, Oxford, UK
5. ⁵INSERM U781, Hôpital Necker-Enfants Malades, Paris, France

Correspondence: Luis Garcia, INSERM, S UMR 787, Groupe Myologie, INSERM-Université Pierre et Marie Curie–Paris VI, 75634 Paris Cedex 13, France. E-mail: luis.garcia@chups.jussieu.fr

The first two authors contributed equally to the work.

Received 15 June 2007; Accepted 15 November 2007; Published online 8 January 2008.

Abstract

Exon-skipping AAV1-U7-associated therapy is a promising treatment for Duchenne muscular dystrophy (DMD). We have shown earlier that the newly rescued dystrophin protein is stably expressed for months in mice and dogs, and does not induce immune rejection of transduced fibers. In this study, we used the dystrophic mdx mouse as a preclinical model to characterize the immune response to the adeno-associated virus 1 (AAV1) vector, and tested the feasibility of administering multiple AAV1 injections to extend the treatment to several muscles. We found that re-injections of AAV1 vector are compromised as early as 3 days after the first injection, coincident with a rapid increase in AAV1-specific immunoglobulin M (IgM) and IgG in the serum. Adoptive transfer of immune sera confirmed the rapid appearance of an AAV1 neutralization activity, and experiments with immunoglobulin-deficient (KO) mice proved that antibodies (Abs) are the only effectors responsible for AAV1-U7 elimination. It is important to note, however, that the AAV2 vector still generated an adverse immune response in KO mice. By blocking the T-B crosstalk with anti-CD40 Abs and CTLA4/Fc fusion protein, we found that a mere 5 days of immunomodulation treatment was sufficient to totally abrogate the formation of anti-AAV1 Abs and to allow for the correction of muscular dystrophy in multiple muscles, provided the treatment was administered during each challenge.