55. Aquaporins and CSF Flux Are Critical Determinants of AAV Mediated CNS Gene Transfer

The central nervous system (CNS) lacks conventional lymphatics for solute clearance. Convective currents of interstitial fluid (ISF) shunt macromolecules across the brain parenchyma into cerebrospinal fluid (CSF) compartments. Here the cargo is either reabsorbed into CNS via subarachnoid ducts or disseminated into the blood or peripheral lymph vessels. Recent studies have identified that flow of water via aquaporin (AQP) channels at the astroglial endfeet enables exchange of biomaterials between ISF and CSF. Conversely, loss of AQP expression due to aging or disease is correlated with ineffective clearance of neurodegenerative accumulations such as Amyloid β and tau. AAV mediated gene therapy of CNS disorders requires a deeper understanding of such factors and their effects on transduction efficiency and biodistribution/clearance. Here, we demonstrate that AQP mediated water transport dictates various aspects of AAV gene transfer in the CNS. We compared the CNS spread, transduction profile and systemic leakage of clinically relevant AAV vectors in wildtype (WT) or AQP knockout (AQP-/-) mice. Within minutes following intracerebroventricular (ICV) administration, AQP-/- mice exhibited highly restricted spread of fluorophore labeled AAVs when compared to wild type mice. Transgene expression was markedly increased from AAV administrations in AQP-/- mice. Further, systemic leakage and off-target transgene expression in peripheral tissues were markedly reduced for some AAV serotypes in AQP-/- mice when compared to WT mice. These results suggest that AQP-mediated water transport plays a critical role in determining the spread, transduction efficiency and systemic leakage of AAV vectors following CNS administration. We hypothesize that altered CSF flux under conditions pertinent to aging and CNS disease, can impact the residence time of AAV vectors and consequently gene transfer efficiency. Further results evaluating the CNS transport properties of AAV in mouse models of aging and disease will be presented.