Abstract TMP116: AAV-sFLT: A Potential Therapeutic Agent for the Treatment of Brain Angiogenic Diseases

Abstract

Background and Purpose: The soluble vascular endothelial growth factor (VEGF) receptor 1 (sFLT) has been tested in both animals and humans for anti-angiogenic therapy, e.g., age-related macular degeneration. We hypothesized that adeno-associated viral vector (AAV)-mediated sFLT expression could be used to treat brain angiogenic diseases, such as brain arteriovenous malformation (bAVM). We tested the anti-angiogenic effect of sFLT and the feasibility of using AAV serotype 9 to deliver AAV-sFLT by intravenous injection (IV) to brain angiogenic lesions. Methods: AAV vectors were packaged in AAV serotypes 1 and 2 (stereotactic injection) and 9 (IV-injection). Angiogenic model was induced in adult wildtype (WT) mice through stereotactic injection of AAV1-VEGF (2×10 9 genome copies (gcs)). Brain AVM model was induced in adult mice with floxed Alk1 (a causative gene for hereditary hemorrhagic telangiectasia that causes AVMs in multiple organs) through co-injection of AAV1-VEGF and Ad-Cre. AAV2-sFLT (2×10 9 gcs) was co-injected with AAV1-VEGF to inhibit brain angiogenesis. Gene expression in the brain by IV-delivered AAV9 was tested using intra-jugular vein injection of AAV9-LacZ or AAV9-GFP (1×10 11 gcs). We then compared gene expression mediated by stereotactic injection of AAV1 and by 2 packaged AAV-LacZ vectors. Results: Co-injection of AAV2-sFLT with AAV1-VEGF completely abolished VEGF-angiogenic effect (320±30/mm 2 vs 434±86 p=0.01). The vessel density around the injection sites was similar to AAV1-LacZ-injected control mice (p=0.84). AAV2-EV (empty virus) had no effect. Intravenous injection of AAV9-LacZ or AAV9-GFP resulted in a higher level of gene expression in the angiogenic foci or bAVM than in normal brain tissues. Gene expression mediated by AAV1 was about 5 times higher than AAV2. Conclusion: AAV mediated sFLT expression inhibited VEGF-induced brain angiogenesis. The sFLT anti-angiogenic effect can be achieved at about 1 to 5 molar ratio of sFLT vs. VEGF. Intravenously injected AAV9 can mediate effective transgene expression in brain angiogenic lesions.