Comparison of treatment efficacy in the hypoglossal motor system of AAV‐DES‐coGAA and novel vector AAV‐DES‐IGFIIcoGAA in Gaa−/− mice

Abstract

Pompe disease is a neuromuscular disorder characterized by a systemic lack of the glycogen metabolizing enzyme acid‐alpha glucosidase. The result is extensive intracellular lysosomal glycogen accumulation and disruption of cellular architecture and function. The hypoglossal (XII) motor system is particularly susceptible to pathology in Pompe disease and both tongue and XII motoneurons show substantial pathology early in the disease progression. Patients often present with macroglossia and tongue weakness, and animal models show pathology in tongue muscles and XII motoneurons. Initial clinical testing indicates that intramuscular gene therapy with adeno‐associated virus (AAV) is safe in Pompe patients and recent work in animal models demonstrates that AAV serotype 9 (AAV9) can produce persistent transgene expression in both tongue muscle and XII motoneurons following a single tongue injection. In ongoing studies, we are using Pompe mice (Gaa−/−) to evaluate the impact of a modified GAA protein with expression being driven by the Desmin promoter. The GAA protein has been modified to allow for IGFII receptor mediated uptake (IGFIIcoGAA) to improve cellular and lysosomal uptake. Initial tests in Gaa−/− mice indicate increased GAA activity without a concomitant increase in antibody response following AAV9‐IGFIIcoGAA delivery to the tibialis anterior muscle. To determine if the new vector offers improved efficacy in the tongue motor system, adult Gaa−/− mice were injected into the base of the tongue with 7μL (1e11 vg/μL) of AAV9‐DES‐coGAA or AAV9‐DES‐IGFIIcoGAA, diluted to 20 μL in lactated ringers (LR), or an equivalent sham injection (20 μL LR). Tongue, medulla and XII nerve tissues were harvested 3‐mo post‐injection. Tissues were paraffin embedded, cut at 7μm and stained with Periodic acid‐Schiff (PAS) to visualize glycogen. Initial qualitative evaluation of tongue histology confirms that both vectors achieved significant clearance of glycogen from tongue myofibers. This was illustrated by the absence of PAS staining at the site of injection and the absence of the prototypical Gaa−/− muscle histopathology characterized by vacuolization and disrupted cellular architecture. Ongoing work is focused on evaluating XII nerve and motoneurons for quantitative comparison of tissues from the three treatment groups.Support or Funding Information2R01HD052682‐06A1 (DDF and BJB)