Low-Dose Liver-Targeted Gene Therapy for Pompe Disease Enhances Therapeutic Efficacy of ERT via Immune Tolerance Induction

Abstract

Pompe disease results from acid α-glucosidase (GAA) deficiency, and enzyme replacement therapy (ERT) with recombinant human (rh) GAA has clinical benefits, although its limitations include the short half-life of GAA and the formation of antibody responses. The present study compared the efficacy of ERT against gene transfer with an adeno-associated viral (AAV) vector containing a liver-specific promoter. GAA knockout (KO) mice were administered either a weekly injection of rhGAA (20 mg/kg) or a single injection of AAV2/8-LSPhGAA (8 × 1011 vector genomes [vg]/kg). Both treatments significantly reduced glycogen content of the heart and diaphragm. Although ERT triggered anti-GAA antibody formation, there was no detectable antibody response following AAV vector administration. The efficacy of three lower dosages of AAV2/8-LSPhGAA was evaluated in GAA-KO mice, either alone or in combination with ERT. The minimum effective dose (MED) identified was 8 × 1010 vg/kg to reduce glycogen content in the heart and diaphragm of GAA-KO mice. A 3-fold higher dose was required to suppress antibody responses to ERT. Efficacy from liver gene therapy was slightly greater in male mice than in female mice. Vector dose correlated inversely with anti-GAA antibody formation, whereas higher vector doses suppressed previously formed anti-GAA antibodies as late as 25 weeks after the start of ERT and achieved biochemical correction of glycogen accumulation. In conclusion, we identified the MED for effective AAV2/8-LSPhGAA-mediated tolerogenic gene therapy in Pompe disease mice.

Targeted delivery of acid alpha-glucosidase corrects skeletal muscle phenotypes in Pompe disease mice

“…The 1e11vg AAV GAA, 1e10vg AAV α-hCD63SC:GAA, and 1e11vg AAV α-hCD63SC:GAA groups had titers in the 10 4 -10 5 range, but these did not reach statistical significance versus control mice. These results agree with previous studies showing there is a serum level threshold that must be reached in order to induce tolerance to GAA 25 .…”

Pompe Disease: From Basic Science to Therapy

“…The appeal of this approach, termed Bimmunomodulatory gene therapy^ [152], is twofold: it induces immune tolerance to GAA by activating regulatory T cells and can provide a stable expression of GAA in liver, thus converting liver into a depot for continuous secretion of GAA and cross-correction in distant organs. Preclinical studies have demonstrated that the secreted GAA is taken up by cardiac and skeletal muscles leading to glycogen reduction and improved muscle function [141,153]. A clinical trial which is scheduled to begin in the fall 2018 will explore the safety of liver-targeted gene therapy.…”

The Respiratory Phenotype of Pompe Disease Mouse Models

“…Gaa −/− mice on both the B6/129 and the pure 129SVE background lack GAA protein and GAA activity in the diaphragm [51][52][53][54][55]. As a result, the diaphragms of these Gaa −/− mice and the mice created by Bijvoet et al have significant glycogen accumulation as demonstrated by positive periodic acid-Schiff (PAS+) staining and mass spectrometry [39,40,51,52,[54][55][56][57][58][59][60]. Mass spectrometry provides evidence that Gaa −/− mice are born with glycogen accumulation in the diaphragm that progressively increases throughout life [56].…”