Abstract
The development of high efficiency, central nervous system (CNS) targeting AAV-based gene therapies is necessary to address challenges in both pre-clinical and clinical investigations. The engineered capsids, AAV.PHP.B and AAV.PHP.eB, show vastly improved blood-brain barrier penetration compared to their parent serotype, AAV9, but with variable effect depending on animal system, strain, and delivery route. As most characterizations of AAV.PHP variants have been performed in mice, it is currently unknown whether AAV.PHP variants improve CNS targeting when delivered intrathecally in rats. We evaluated the comparative transduction efficiencies of equititer doses (6 × 1011vg) of AAV.PHP.eB-CAG-GFP and AAV9-CAG-GFP when delivered into the cisterna magna of 6–9-month old rats. Using both quantitative and qualitative assessments, we observed consistently superior biodistribution of GFP+ cells and fibers in animals treated with AAV.PHP.eB compared to those treated with AAV9. Enhanced GFP signal was uniformly observed throughout rostrocaudal brain regions in AAV.PHP.eB-treated animals with matching GFP protein expression detected in the forebrain, midbrain, and cerebellum. Collectively, these data illustrate the benefit of intracisternal infusions of AAV.PHP.eB as an optimal system to distribute CNS gene therapies in preclinical investigations of rats, and may have important translational implications for the clinical CNS targeting.
Highlights
AAV9-GFP-treated animals feature sparse staining with minimal generalized fiber staining and greater GFP expression in the cerebellum and nuclei proximal to the cisterna magna (CM) (Fig. 1b, c)
Several lines of evidence have shown that intrathecal delivery of viral vectors can enhance central nervous system (CNS) penetration and optimize the ratio of CNS/peripheral transduction [6, 15, 16]
Intrathecal delivery of AAV9-gene therapies has been employed in clinical trials for the treatment of giant axonal neuropathy [7] and spinal muscular atrophy [17]
Summary
The use of adeno-associated viruses (AAV) for the targeting of the central nervous system (CNS) has revolutionized gene therapy for neurological disorders. AAV-vectors still face significant challenges in achieving broad and efficient CNS biodistribution and transduction. Currently in clinical use, AAV9-mediated gene delivery requires high viral load to achieve relatively limited transduction throughout the CNS. Recent development of a Credependent in vivo platform for the selection of targetspecific AAV capsids led to the discovery of novel engineered AAV9-derived variants, AAV.PHP.eB and AAV. The pre-clinical efficiency of CNS targeting with both variants is highly variable depending on the animal strain [3], promoter selection [4], viral titer [1, 2, 5], or species [3, 6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
