694. Improved Therapeutic Efficacy Following AAV2/8-Mediated Expression of α-Galactosidase A in Fabry Mice
Authors: R. J. Ziegler, C. M. Barbon, C. Li, S. Bercury, M. Cherry, S. H. Cheng
Journal: Molecular Therapy (2004)

Fabry disease is an inherited disorder that is caused by a deficiency of the lysosomal enzyme α-galactosidase A. This results in the progressive accumulation of the glycosphingolipid, globotriaocylceramide (GL-3) in the lysosomes of endothelial, perithelial and smooth muscle cells. Substrate deposition also occurs in structures of the central, peripheral and autonomic nervous system. Previously, we showed that intravenous administration of 5 × 1011 particles of a recombinant AAV2 vector encoding human α-galactosidase A under the transcriptional control of a liver-restricted enhancer/promoter (DC190) into Fabry mice resulted in expression of therapeutic levels of the enzyme that was sustained for 12 months. Treatment resulted in a reduction of GL-3 in the liver, spleen and heart to basal levels and in the kidney by approximately 40% at 8 weeks. To improve the therapy to the kidney, different AAV serotypes (1, 5, and 8) with reportedly higher hepatic transduction activity were evaluated. A very modest improvement in expression of α-galactosidase A was seen with the AAV pseudotypes 2/1 and 2/5 when compared to 2/2. However, the corresponding AAV2/8 vector generated approximately 100 fold greater levels of the enzyme than the AAV2/2 vector. Moreover, the kinetics of expression from the AAV2/8 vector was more rapid, with α-galactosidase A in the serum detected as early as 1 week post-treatment. Intravenous administration of 5 × 1010 particles of the AAV2/8 virus into Fabry mice resulted in higher levels of expression of the enzyme and more rapid clearance of GL-3 from the affected tissues than with a 10 fold higher dose of the corresponding AAV2/2 vector. Clearance of GL-3 from the AAV2/8-treated tissues including kidney was essentially complete by 4 instead of 8 weeks. Hence a significant improvement in potency was realized with the AAV2/8 pseudotyped vector. In addition to correcting the aberrant GL-3 levels, an improvement in the thermal sensitivity of the treated Fabry mice was also realized. Fabry mice demonstrate a delayed response to placement on a hot plate that is equilibrated to 55°C (as demonstrated by a flick of its hindlimbs) when compared to unaffected normal mice (129/Sv). The response time of untreated Fabry mice became progressively longer over a period of 8 months. In contrast, Fabry mice treated at 5 weeks of age with the AAV2/8 vector demonstrated short response times that were similar to those for age-matched normal 129/Sv mice throughout the study. The hindlimb footpads of the mice, as well as dorsal root ganglia of the spinal cord have been examined histologically to show if the pathology corresponded to the improvement in thermal sensitivity. Finally, we demonstrated that the immune tolerance to α-galactosidase A observed previously using an AAV2/2 vector harboring a liver-restricted promoter also applied to the AAV2/8 vector. Together, these data support the continued development of AAV2/8-mediated gene therapy for Fabry disease.