Abstract
The brain vasculature forms an immense network such that most neural cells are in contact with a microvessel. Here we tested the hypothesis that endothelia lining these vessels can be harnessed to create a cellular reservoir of enzyme replacement therapy to diseased brain. As a model system, we used mice with central nervous system (CNS) deficits due to lysosomal storage disease (LSD mice). The basic premise of this work is that recombinant enzyme expressed in, and secreted from, the vascular endothelia will be endocytosed by underlying neurons and glia, decreasing neuropathology. We screened a phage library in vivo by panning to identify peptides that bound the vascular endothelia in diseased and wild-type mice. Epitopes binding diseased brain were distinct from those panned from normal brain. Moreover, different epitopes were identified in two distinct LSD disease models, implying a unique vascular signature imparted by the disease state. Presentation of these epitopes on the capsid of adeno-associated virus (AAV) expanded the biodistribution of intravenously injected AAV from predominantly liver to include the CNS. Peripheral injection of the epitope-modified AAVs expressing the enzymes lacking in LSD mice reconstituted enzyme activity throughout the brain and improved disease phenotypes in two distinct disease models.