510. Synergistic Efficacy from Gene Therapy with Pompe Disease Using Anti-CD4 mAb and a Beta-Agonist, Clenbuterol
Authors: Sang-oh Han, Songtao Li, Andrew Bird, Dwight Koeberl
Journal: Molecular Therapy (2015)

Pompe disease is a lysosomal storage disorder caused by deficiency of acid α-glucosidase (GAA), and makes weakness in many organs and tissues including cardiac and skeletal muscles. An adeno-associated virus (AAV) vector containing a muscle specific-expression promoter, AAV-MHCK7hGAApA, showed elevated GAA expression levels in cardiac and skeletal muscles in GAA knockout (KO) mice. Efficacy of Pompe gene therapy is minimized by at least 2 serious obstacles; 1) low expression of cationic-independent mannose-6-phosphate receptor (CI-MPR) which mediates uptake and trafficking of GAA from blood stream to lysosomes, 2) immune responses against introduced GAA especially in cross-reactive immunological material (CRIM)-negative patients. According to our previous studies, the level of CI-MPR in skeletal muscles could be increased by treatment of β-agonists (clenbuterol and albuterol), and immune responses could be blocked by a single injection of anti-CD4 mAb.herefore, we were interested in a combined treatment of clenbuterol and anti-CD4 mAb in Pompe gene therapy to reach the sufficient efficacy for clinical application. We injected 20 mg/mouse anti-CD4 mAb at one day before the injection of AAV-MHCK7hGAApA, and treated 6 mg/ml clenbuterol in drinking water for 13 weeks. In measurement of physical conditions, latency time on the Rotarod was increased by treatment of anti-CD4 mAb but not by clenbuterol. Meanwhile, the latency time with wirehang was increased by clenbuterol treatment. As the latency on Rotarod related to the mice's neuromuscular abilities, injection of anti-CD4 mAb might enhance the physical condition of AAV-treated GAA-KO mice, and clenbuterol might enhance muscle strength of GAA-KO mice. Encouragingly, the combined treatment showed a further enhancement in the both tests (p<0.05, p<0.01, respectively). We also measured GAA level and glycogen clearance in several tissues to evaluate the effect of combinational treatment in biochemical corrections. We found that GAA activity was correlated with glycogen clearance in cardiac muscle but not in skeletal muscles. Glycogen clearance was mainly correlated the effect of beta-agonist in skeletal muscles (p<0.01). Importantly, the combinationed treatment Pompe gene therapy showed clear synergistic effect for the clearance of glycogen in both cardiac (p<0.001) and skeletal muscles (p<0.001 in quadriceps, and p<0.01 in gastrocnemius). The combined treatment also showed the synergic effect in gaining of body weight. From this study, we concluded that therapeutic effects of Pompe gene therapy including glycogen clearance and muscle strength was not only by GAA activity but also by other lysosomal functions such as β-adrenergic receptor-mediated endocytosis. In addition, drug effects were shown to be different between cardiac and skeletal muscles. Together, the results demonstrate that an optimizing clinical outcome could be achieved by the combined treatment with stimulation of β-adrenergic receptor and suppression of immune response.