Central Nervous System Gene Therapy Research Articles

An AAV capsid reprogrammed to bind human transferrin receptor mediates brain-wide gene delivery.

Developing vehicles that efficiently deliver genes throughout the human central nervous system (CNS) will broaden the range of treatable genetic diseases. We engineered an adeno-associated virus (AAV) capsid, BI-hTFR1, that binds human transferrin receptor (TfR1), a protein expressed on the blood-brain barrier. BI-hTFR1 was actively transported across human brain endothelial cells and, relative to AAV9, provided 40 to 50 times greater reporter expression in the CNS of human TFRC knockin mice. The enhanced tropism was CNS-specific and absent in wild-type mice. When used to deliver GBA1, mutations of which cause Gaucher disease and are linked to Parkinson's disease, BI-hTFR1 substantially increased brain and cerebrospinal fluid glucocerebrosidase activity compared with AAV9. These findings establish BI-hTFR1 as a potential vector for human CNS gene therapy.

Miniaturization of hiPSC-derived 3D neural cultures in stirred-tank bioreactors for parallelized preclinical assessment of rAAV.

Introduction: Engineered 3D models employing human induced pluripotent stem cell (hiPSC) derivatives have the potential to recapitulate the cell diversity and structure found in the human central nervous system (CNS). Therefore, these complex cellular systems offer promising human models to address the safety and potency of advanced therapy medicinal products (ATMPs), such as gene therapies. Specifically, recombinant adeno-associated viruses (rAAVs) are currently considered highly attractive for CNS gene therapy due to their broad tropism, low toxicity, and moderate immunogenicity. To accelerate the clinical translation of rAAVs, in-depth preclinical evaluation of efficacy and safety in a human setting is primordial. The integration of hiPSC-derived CNS models in rAAV development will require, amongst other factors, robust, small-scale, high-throughput culture platforms that can feed the preclinical trials. Methods: Herein, we pioneer the miniaturization and parallelization of a 200mL stirred-tank bioreactor-based 3D brain cell culture derived from hiPSCs. We demonstrate the applicability of the automated miniaturized Ambr® 15 Cell Culture system for the maintenance of hiPSC-derived neurospheroids (iNSpheroids), composed of neuronal and glial cells. Critical process parameters were optimized, namely, cell density and agitation mode. Results: Under optimized conditions, stable iNSpheroid cultures were attained in the microbioreactors for at least 15days, with high cell viability and astrocytic and neuronal phenotype maintenance. This culture setup allowed the parallelization of different rAAVs, in different multiplicity of infections (MOIs), to address rAAV-host interactions at a preclinical scale. The iNSpheroids were exposed to rAAV2- and rAAV9-eGFP in the microbioreactors. Transgene expression was detected 14days post-transduction, revealing different astrocyte/neuron tropism of the two serotypes. Discussion: We advocate that the iNSpheroid cultures in miniaturized bioreactors are reliable and reproducible screening tools for addressing rAAV transduction and tropism, compatible with preclinical demands.

Development of adenoviral vectors that transduce Purkinje cells and other cerebellar cell-types in the cerebellum of a humanized mouse model

Viral vector gene therapy has immense promise for treating central nervous system (CNS) disorders. Although adeno-associated virus vectors (AAVs) have had success, their small packaging capacity limits their utility to treat the root cause of many CNS disorders. Adenoviral vectors (Ad) have tremendous potential for CNS gene therapy approaches. Currently, the most common vectors utilize the Group C Ad5 serotype capsid proteins, which rely on the Coxsackievirus-Adenovirus receptor (CAR) to infect cells. However, these Ad5 vectors are unable to transduce many neuronal cell types that are dysfunctional in many CNS disorders. The human CD46 (hCD46) receptor is widely expressed throughout the human CNS and is the primary attachment receptor for many Ad serotypes. Therefore, to overcome the current limitations of Ad vectors to treat CNS disorders, we created chimeric first generation Ad vectors that utilize the hCD46 receptor. Using a "humanized" hCD46 mouse model, we demonstrate these Ad vectors transduce cerebellar cell types, including Purkinje cells, that are refractory to Ad5 transduction. Since Ad vector transduction properties are dependent on their capsid proteins, these chimeric first generation Ad vectors open new avenues for high-capacity helper-dependent adenovirus (HdAd) gene therapy approaches for cerebellar disorders and multiple neurological disorders.

Intracranial Gene Delivery Mediated by Albumin-Based Nanobubbles and Low-Frequency Ultrasound

Research in the field of high-intensity focused ultrasound (HIFU) for intracranial gene therapy has greatly progressed over the years. However, limitations of conventional HIFU still remain. That is, genes are required to cross the blood-brain barrier (BBB) in order to reach the neurological disordered lesion. In this study, we introduce a novel direct intracranial gene delivery method, bypassing the BBB using human serum albumin-based nanobubbles (NBs) injected through a less invasive intrathecal route via lumbar puncture, followed by intracranial irradiation with low-frequency ultrasound (LoFreqUS). Focusing on both plasmid DNA (pDNA) and messenger RNA (mRNA), our approach utilizes LoFreqUS for deeper tissue acoustic penetration and enhancing gene transfer efficiency. This drug delivery method could be dubbed as the “Spinal Back-Door Approach”, an alternative to the “front door” BBB opening method. Experiments showed that NBs effectively responded to LoFreqUS, significantly improving gene transfer in vitro using U-87 MG cell lines. In vivo experiments in mice demonstrated significantly increased gene expression with pDNA; however, we were unable to obtain conclusive results using mRNA. This novel technique, combining albumin-based NBs and LoFreqUS offers a promising, efficient, targeted, and non-invasive solution for central nervous system gene therapy, potentially transforming the treatment landscape for neurological disorders.

Central Nervous System Gene Therapy: Present Developments and Emerging Trends Accelerating Industry-Academia Pathways.

The recent success of first central nervous system gene therapies has reinvigorated the growing community of gene therapy researchers and strengthened the field's market position. We are witnessing an increase of clinical trials with long-term efficiency mainly for neurometabolic, neurodegenerative, and neurodevelopmental diseases caused by loss-of-function mutations. The ever-expanding knowledge and accessibility to the most advanced tools allow enrichment of applications to more complex diseases. This gradually contributes toward sealing the gap between top diseases impacting current global health and those toward which gene therapy development is currently aimed. In this study, we highlight innovative therapeutic approaches that have reached the clinics and outline the latest improvements of vector design and targeting. Finally, we address the pressing challenges faced by clinical trials and the direction they are heading.

2021 Workshop: Neurodegenerative Diseases in the Gut-Brain Axis—Parkinson's Disease

2021 Workshop: Neurodegenerative Diseases in the Gut-Brain Axis—Parkinson's Disease

Seven-year follow-up of durability and safety of AAV CNS gene therapy for a lysosomal storage disorder in a large animal

Delivery of adeno-associated viral vectors (AAVs) to cerebrospinal fluid (CSF) has emerged as a promising approach to achieve widespread transduction of the central nervous system (CNS) and peripheral nervous system (PNS), with direct applicability to the treatment of a wide range of neurological diseases, particularly lysosomal storage diseases. Although studies in small animal models have provided proof of concept and experiments in large animals demonstrated feasibility in bigger brains, there is not much information on long-term safety or durability of the effect. Here, we report a 7-year study in healthy beagle dogs after intra-CSF delivery of a single, clinically relevant dose (2 × 1013 vg/dog) of AAV9 vectors carrying the canine sulfamidase, the enzyme deficient in mucopolysaccharidosis type IIIA. Periodic monitoring of CSF and blood, clinical and neurological evaluations, and magnetic resonance and ultrasound imaging of target organs demonstrated no toxicity related to treatment. AAV9-mediated gene transfer resulted in detection of sulfamidase activity in CSF throughout the study. Analysis at tissue level showed widespread sulfamidase expression and activity in the absence of histological findings in any region of encephalon, spinal cord, or dorsal root ganglia. Altogether, these results provide proof of durability of expression and long-term safety for intra-CSF delivery of AAV-based gene transfer vectors encoding therapeutic proteins to the CNS.

CNS Transduction Benefits of AAV-PHP.eB over AAV9 Are Dependent on Administration Route and Mouse Strain

Adeno-associated viral (AAV) vectors are attractive tools for central nervous system (CNS) gene therapy because some vectors can cross the blood-brain barrier (BBB), allowing them to be used as minimally invasive treatments. A novel AAV vector recently evolved in vivo, AAV-PHP.eB, has been reported to cross the BBB more effectively than the existing gold standard AAV9, but not under all conditions. Here, we compared the efficacy of single-stranded AAV-PHP.eB and AAV9 in targeting mouse CNS and peripheral tissues after administration via various routes, in two different mouse strains (C57BL/6J and B6C3), and after packaging AAV-PHP.eB with a self-complementary genome. We found that AAV-PHP.eB produced higher CNS transduction than AAV9 after intravenous injection, but only in C57BL/6J and not in B6C3 mice. AAV-PHP.eB and AAV9 produced similar CNS transduction when the administration route did not require the vectors to cross the BBB. Packaging AAV-PHP.eB with a self-complementary genome increased overall CNS transduction, but at the expense of strong neuronal tropism. AAV-PHP.eB resulted in less transduction of liver tissue than AAV9 under all conditions. Taken together, these results suggest the potential for AAV-PHP.eB as a vector for CNS gene therapy applications, but consideration will be required for translation beyond mouse models.

Intravenous injection of AAV-PHP.eB across the blood-brain barrier in the adult mouse for central nervous system gene therapy*

Abstract Objective To verify the neurotypicality of AAV-PHP.eB after tail vein injection in adult mice and its efficiency in crossing the blood-brain barrier (BBB). Methods The rAAV-SYN-GFP plasmid was constructed, and adult C57BL mice were injected with AAV-PHP. eB: SYN-GFP in the tail vein (300 nL, virus titer 3 × 109 vg) and in the prefrontal lobe (50 L, virus titer 5 × 1011 vg). The green fluorescent protein (GFP) signal in the brain was observed at two weeks, while the GFP signal in the peripheral organs was observed at four weeks. Results Two weeks after tail vein injection, GFP expression was observed throughout the brain, especially in the cortex, hippocampus, and geniculate nucleus. No GFP signal was observed or detected by western blotting in the peripheral organs after four weeks. GFP signal was observed mainly at the local site after prefrontal lobe injection. Conclusion AAV-PHP.eB: SYN-GFP can effectively cross the BBB in adult mice. Using a neuron-specific promoter allows exogenous gene expression in neurons; therefore, AAV-PHP.eB can be used as an effective carrier for studying diseases in the central nervous system (CNS).

In Vivo Selection Yields AAV-B1 Capsid for Central Nervous System and Muscle Gene Therapy.

Adeno-associated viral (AAV) vectors have shown promise as a platform for gene therapy of neurological disorders. Achieving global gene delivery to the central nervous system (CNS) is key for development of effective therapies for many of these diseases. Here we report the isolation of a novel CNS tropic AAV capsid, AAV-B1, after a single round of in vivo selection from an AAV capsid library. Systemic injection of AAV-B1 vector in adult mice and cat resulted in widespread gene transfer throughout the CNS with transduction of multiple neuronal subpopulations. In addition, AAV-B1 transduces muscle, β-cells, pulmonary alveoli, and retinal vasculature at high efficiency. This vector is more efficient than AAV9 for gene delivery to mouse brain, spinal cord, muscle, pancreas, and lung. Together with reduced sensitivity to neutralization by antibodies in pooled human sera, the broad transduction profile of AAV-B1 represents an important improvement over AAV9 for CNS gene therapy.

157. High-Field In Vivo Neuroimaging to Determine CNS Gene Therapy Outcome and Probe Disease Pathomechanism

Gene therapy targeting the central nervous system (CNS) is one of the most challenging gene therapies due to the blood-brain barrier (BBB). However, recombinant adeno-associated virus (rAAV) has proved to be an excellent tool to target the CNS. Another obstacle in the setting of CNS gene therapy is the non-invasive evaluation of therapeutic outcome. While biopsies and sections of the CNS are the gold-standard to assess brain pathology and response to CNS gene therapy, the invasiveness and potentially associated complications limit its frequent use in pre-clinical as well as clinical studies. Thus, it is of no surprise that non-invasive monitoring of CNS gene therapy in vivo holds great promise for longitudinal and functional assessment of treatment response. We used high-field in vivo neuroimaging to monitor intravenously (i.v.) and intracerebroventricularly (i.c.v.) administered rAAV based CNS directed gene therapy in a mouse model of Canavan disease (CD). Characteristically, Canavan disease presents with a very high NAA peak detected by magnet resonance spectrometry (MRS) and hyper intensity on T2-weighted anatomic images using magnet resonance imaging (MRI). Consequently, we first determined the efficacy of our i.v. and i.c.v. gene therapy by those two means. In congruence with motor function and pathology data, both MRI and MRS alterations have been entirely normalized by gene therapy. Another characteristic neuropathological change on Canavan brain sections is the loss of white matter tracts, which is thought to explain neurological symptoms seen in Canavan disease patients. Thus, we hypothesized that diffusion tensor imaging (DTI) enables the assessment of white matter tract degeneration and recovery upon gene therapy without brain biopsies. Selecting thalamus and corpus callosum as regions of interest (ROI), DTI indeed shows a recovery of brain white matter integrity when utilizing 3rd generation Canavan gene therapy. Furthermore, our 3rd generation gene therapy converts this CD mouse model with the severest phenotype into “supermouse”, outperforming wild-type mouse on motor function testing. We hypothesized that functional connectivity identifies brain regions that not only show response to treatment but also indicates possible explanations for this enhanced phenotype. Using resting-state functional MRI (rs-fMRI), we show that treated CD mice have a functional connectivity pattern that is more similar to or even enhanced beyond what is seen in WT brain. This suggests facilitated inter-brain-region functional connectivity, which might provide a neural mechanism that sub-serves the observed enhanced motor function. Currently, we are investigating how the identified brain regions can promote increased motor function, and how high-field brain imaging can provide biomarkers to track the disorder and treatment response in a manner that would help facilitate the prediction of CNS directed gene therapy outcome. In summary, our data show that high-field in vivo neuroimaging is a valuable tool to monitor pre-clinical CNS gene therapy and pathology in detail, that it can provide insights into pathophysiology and that it has potential implications for the use in clinical trial outcome prediction and assessment.

Neonatal Systemic AAV Induces Tolerance to CNS Gene Therapy in MPS I Dogs and Nonhuman Primates

The potential host immune response to a nonself protein poses a fundamental challenge for gene therapies targeting recessive diseases. We demonstrate in both dogs and nonhuman primates that liver-directed gene transfer using an adeno-associated virus (AAV) vector in neonates induces a persistent state of immunological tolerance to the transgene product, substantially improving the efficacy of subsequent vector administration targeting the central nervous system (CNS). We applied this approach to a canine model of mucopolysaccharidosis type I (MPS I), a progressive neuropathic lysosomal storage disease caused by deficient activity of the enzyme α-l-iduronidase (IDUA). MPS I dogs treated systemically in the first week of life with a vector expressing canine IDUA did not develop antibodies against the enzyme and exhibited robust expression in the CNS upon intrathecal AAV delivery at 1 month of age, resulting in complete correction of brain storage lesions. Newborn rhesus monkeys treated systemically with AAV vector expressing human IDUA developed tolerance to the transgene, resulting in high cerebrospinal fluid (CSF) IDUA expression and no antibody induction after subsequent CNS gene therapy. These findings suggest that inducing tolerance to the transgene product during a critical period in immunological development can improve the efficacy and safety of gene therapy.

603. Novel DNA-Shuffled AAV Capsids Show Robust and Unique Gene Delivery and Expression Profiles in the CNS Via Intrathecal Injection

Aim: Adeno-associated virus (AAV) has great potential for treatment of central nervous system (CNS) diseases. Currently, a few AAV serotypes including AAV9 effectively deliver genes in the CNS. We aimed to screen more AAV serotypes for expression in CNS and compare them to AAV9.Material and methods: Using an existing library containing shuffled capsid genes of AAV serotypes 1 through 9, we characterized a few novel capsids for high expression in the CNS in vivo. Three novel serotypes, AAVH43, AAVH48, and AAVHH67 containing the reporter gene lacZ driven by a CMV promoter were injected in C57BL/6 mice and AAV9 was included as a positive control group (n=4 per group). Prior to vector injection, 25% mannitol solution 200μl was given by tail vein to deduce intracranial pressure. Twenty minutes later, 10μl of virus vectors (1×1011 vg) were slowly injected into the cerebrospinal fluid (CSF) at the intervertenral space between lumbar vertebrae L3 and L4 by a 33-gauge needle connected to a 50μl Hamilton syringe with PE10 tubing. Two weeks later, tissue samples were harvested for lacZ staining and immunostaining.Results: LacZ gene delivered by AAVH43, AAVH48, and AAVHH67 vectors expressed efficiently and similarly to AAV9 in the spinal cord by intrathecal injection. The entire spinal cord from the lumbar up to cervical region showed gene expression. The infected cells were mainly distributed in the posterior funiculus and gray matter. In addition, all 4 vectors infected dorsal root ganglia neurons very efficiently. Immunostaining showed AAVH43, AAVH48 and AAVHH67 vectors with a CMV promoter infected mainly neurons but not glial cells, similar to AAV9. In addition, AAVH43 and AAVH48 had some common characteristics and infected cerebellar cortex much more efficiently than AAV9. Those neurons showed distinctive morphology as Purkinje cells. Further confirmation with cell-type specific antibodies is needed.Conclusion: The AAVH43, AAVH48 and AAVHH67 vectors have similar ability to infect the spinal cord and dorsal root ganglia, equivalent to AAV9, when delivered by intrathecal injection. Moreover, the cerebellar cortex is more susceptible to AAVH43 and AAVH48 infection. With further investigation, the three novel AAV serotypes could be suitable alternative candidates for CNS gene delivery and therapy.

545. Strong Cortico-Spinal Transduction After AAV5 Delivery into the Central Nervous System of Nonhuman Primates

Widespread distribution of gene products at clinically relevant levels throughout the central nervous system (CNS) without involving peripheral organs is still a challenge. Previous work demonstrated that infusion of adeno-associated virus (AAV) serotypes 9 (AAV9) and 7 (AAV7) into the cerebrospinal fluid (CSF) via cisterna magna of nonhuman primates (NHP) resulted in widespread transduction throughout cortex and spinal cord. Adeno-associated virus serotype 5 (AAV5) is also a potential candidate for CNS gene therapy when delivered into brain parenchyma but its performance in CSF has not been described. In the present work, we compared transduction patterns after CSF and parenchymal delivery of AAV5-GFP. For CSF delivery, we injected various doses of AAV5 (1E+14, 1E+13 and 1E+12 vg/mL) into CSF via lumbar routes in naive NHP and studied vector distribution and cellular transduction 4 weeks after CSF delivery. We found a dose-dependent increase in transduction with strong levels of cell transduction and distribution throughout cortex and along the spinal cord at the highest doses and no signal in the low-dose group. These results suggest a dose threshold when delivering into CSF, most likely due to a dilution of the viral particles. Both astrocytes and neurons were transduced by AAV5 when infused either in CSF or directly into brain parenchyma.Parenchymal delivery of AAV5-GFP was analyzed 8 weeks after surgery. Interestingly, when infused into the thalamus and the contralateral putamen, AAV5 resulted in higher levels of expression in cortical and subcortical structures than those observed in high-dose CSF animals. Surprisingly, thalamic injection directed spinal cord transduction throughout the cortico-bulbar axis. These results suggest not only that smaller volumes of AAV5 infused directly into the thalamus can result in robust and widespread cellular transduction in the brain but also to spinal cord. Our results confirm AAV5 as a powerful viral vector for gene transfer in the CNS and underscore its translational potential for treating neurological disorders of the brain and spinal cord.

Genetic modification of neurons to express bevacizumab for local anti-angiogenesis treatment of glioblastoma.

The median survival of glioblastoma multiforme (GBM) approximately 1 yr. Following surgical removal, systemic therapies are limited by the blood-brain barrier. To circumvent this, we developed a method to modify neurons with the genetic sequence for therapeutic monoclonal antibodies using adeno-associated virus (AAV) gene transfer vectors, directing persistent, local expression in the tumor milieu. The human U87MG GBM cell line or patient-derived early passage GBM cells were administered to the striatum of NOD/SCID immunodeficient mice.AAVrh.10BevMab, an AAVrh.10-based vector coding for bevacizumab (Avastin®), an anti-human vascular endothelial growth factor (VEGF) monoclonal antibody, was delivered to the area of the GBM xenograft. Localized expression of bevacizumab was demonstrated by quantitative PCR, ELISA and Western. Immunohistochemistry showed the bevacizumab was expressed in neurons. Concurrent administration of AAVrh.10BevMab with the U87MG tumor reduced tumor blood vessel density, and tumor volume and increased survival. Administration of AAVrh.10BevMab 1 wk after U87MG xenograft reduced growth and increased survival. Studies with patient-derived early passage GBM primary cells showed a reduction in primary tumor burden with an increased survival. This data supports the strategy of AAV-mediated CNS gene therapy to treat GBM, overcoming the blood-brain barrier through local, persistent delivery of an anti-angiogenesis monoclonal antibody.

Global CNS Transduction of Adult Mice by Intravenously Delivered rAAVrh.8 and rAAVrh.10 and Nonhuman Primates by rAAVrh.10

Some recombinant adeno-associated viruses (rAAVs) can cross the neonatal blood-brain barrier (BBB) and efficiently transduce cells of the central nervous system (CNS). However, in the adult CNS, transduction levels by systemically delivered rAAVs are significantly reduced, limiting their potential for CNS gene therapy. Here, we characterized 12 different rAAVEGFPs in the adult mouse CNS following intravenous delivery. We show that the capability of crossing the adult BBB and achieving widespread CNS transduction is a common character of AAV serotypes tested. Of note, rAAVrh.8 is the leading vector for robust global transduction of glial and neuronal cell types in regions of clinical importance such as cortex, caudate-putamen, hippocampus, corpus callosum, and substantia nigra. It also displays reduced peripheral tissue tropism compared to other leading vectors. Additionally, we evaluated rAAVrh.10 with and without microRNA (miRNA)-regulated expressional detargeting from peripheral tissues for systemic gene delivery to the CNS in marmosets. Our results indicate that rAAVrh.8, along with rh.10 and 9, hold the best promise for developing novel therapeutic strategies to treat neurological diseases in the adult patient population. Additionally, systemically delivered rAAVrh.10 can transduce the CNS efficiently, and its transgene expression can be limited in the periphery by endogenous miRNAs in adult marmosets.

Nanobiotechnology-based Drug Delivery in Brain Targeting

Blood brain barrier (BBB) found to act as rate limiting factor in drug delivery to brain in combating the central nervous system (CNS) disorders. Such limiting physiological factors include the reticuloendothelial system and protein opsonization, which present across BBB, play major role in reducing the passage of drug. Several approaches employed to improve the drug delivery across the BBB. Nanoparticles (NP) are the solid colloidal particle ranges from 1 to 1000 nm in size utilized as career for drug delivery. At present NPs are found to play a significant advantage over the other methods of available drug delivery systems to deliver the drug across the BBB. Nanoparticles may be because of its size and functionalization characteristics able to penetrate and facilitate the drug delivery through the barrier. There are number of mechanisms and strategies found to be involved in this process, which are based on the type of nanomaterials used and its combination with therapeutic agents, such materials include liposomes, polymeric nanoparticles and non-viral vectors of nano-sizes for CNS gene therapy, etc. Nanotechnology is expected to reduce the need for invasive procedures for delivery of therapeutics to the CNS. Some devices such as implanted catheters and reservoirs however will still be needed to overcome the problems in effective drug delivery to the CNS. Nanomaterials are found to improve the safety and efficacy level of drug delivery devices in brain targeting. Nanoegineered devices are found to be delivering the drugs at cellular levels through nono-fluidic channels. Different drug delivery systems such as liposomes, microspheres, nanoparticles, nonogels and nonobiocapsules have been used to improve the bioavailability of the drug in the brain, but microchips and biodegradable polymeric nanoparticulate careers are found to be more effective therapeutically in treating brain tumor. The physiological approaches also utilized to improve the transcytosis capacity of specific receptors expressed across the BBB. It is found that the low density lipoproteins related protein (LPR) with engineered peptide compound (EpiC) formed the platform incorporating the Angiopep peptide as a new effective therapeutics. The current challenges are to design and develop the drug delivery careers, which must be able to deliver the drug across the BBB at a safe and effective manner. Nanoparticles are found to be effective careers in delivery of conventional drugs, recombinant proteins, vaccines as well as nucleotides. Nanoparticlulate drug delivery systems are found to be improving in the pharmacokinetic strategies of the drug molecules such as biodistribution, bioavailability and drug release characteristics in a controlled and effective manner with site specific drug delivery targeting to tissue or cell with reduction in toxic manifestation. Therefore, the use of nanotechnology in the field of pharmaceutical biotechnology helps in improving the drug delivery strategy including the kinetics and therapeutic index to solve the delivery problems of some biotech drugs including the recombinant proteins and oligonucleotides. This review is made to provide an insight to the role of nanobiotechnology in drug delivery and drug targeting to brain and its recent advances in the field of drug delivery systems.

A Single Intravenous rAAV Injection as Late as P20 Achieves Efficacious and Sustained CNS Gene Therapy in Canavan Mice

Canavan's disease (CD) is a fatal pediatric leukodystrophy caused by mutations in aspartoacylase (AspA) gene. Currently, there is no effective treatment for CD; however, gene therapy is an attractive approach to ameliorate the disease. Here, we studied progressive neuropathology and gene therapy in short-lived (≤ 1 month) AspA(-/-) mice, a bona-fide animal model for the severest form of CD. Single intravenous (IV) injections of several primate-derived recombinant adeno-associated viruses (rAAVs) as late as postnatal day 20 (P20) completely rescued their early lethality and alleviated the major disease symptoms, extending survival in P0-injected rAAV9 and rAAVrh8 groups to as long as 2 years thus far. We successfully used microRNA (miRNA)-mediated post-transcriptional detargeting for the first time to restrict therapeutic rAAV expression in the central nervous system (CNS) and minimize potentially deleterious effects of transgene overexpression in peripheral tissues. rAAV treatment globally improved CNS myelination, although some abnormalities persisted in the content and distribution of myelin-specific and -enriched lipids. We demonstrate that systemically delivered and CNS-restricted rAAVs can serve as efficacious and sustained gene therapeutics in a model of a severe neurodegenerative disorder even when administered as late as P20.

Gene Therapy for Canavan's Disease Takes a Step Forward

Gene Therapy for Canavan's Disease Takes a Step Forward

Adeno-associated Virus-mediated, Mifepristone-regulated Transgene Expression in the Brain

Gene therapy, in its current configuration, is irreversible and does not allow control over transgene expression in case of side effects. Only few regulated vector systems are available, and none of these has reached clinical applicability yet. The mifepristone (Mfp)-regulated Gene Switch (GS) system is characterized by promising features such as being composed of mainly human components and an approved small-molecule drug as an inducer. However, it has not yet been evaluated in adeno-associated virus (AAV) vectors, neither has it been tested for applicability in viral vectors in the central nervous system (CNS). Here, we demonstrate that the GS system can be used successfully in AAV vectors in the brain, and that short-term induced glial cell line-derived neurotrophic factor (GDNF) expression prevented neurodegeneration in a rodent model of Parkinson's disease (PD). We also demonstrate repeated responsiveness to the inducer Mfp and absence of immunological tissue reactions in the rat brain. Human equivalent dosages of Mfp used in this study were lower than those used safely for treatment of psychiatric threats, indicating that the inducer could be safely applied in patients. Our results suggest that the GS system in AAV vectors is well suited for further development towards clinical applicability.