Ahad A. Rahim

Mitochondria and Quality Control Defects in a Mouse Model of Gaucher Disease—Links to Parkinson’s Disease

Summary Mutations in the glucocerebrosidase (gba) gene cause Gaucher disease (GD), the most common lysosomal storage disorder, and increase susceptibility to Parkinson’s disease (PD). While the clinical and pathological features of idiopathic PD and PD related to gba (PD-GBA) mutations are very similar, cellular mechanisms underlying neurodegeneration in each are unclear. Using a mouse model of neuronopathic GD, we show that autophagic machinery and proteasomal machinery are defective in neurons and astrocytes lacking gba. Markers of neurodegeneration—p62/SQSTM1, ubiquitinated proteins, and insoluble α-synuclein—accumulate. Mitochondria were dysfunctional and fragmented, with impaired respiration, reduced respiratory chain complex activities, and a decreased potential maintained by reversal of the ATP synthase. Thus a primary lysosomal defect causes accumulation of dysfunctional mitochondria as a result of impaired autophagy and dysfunctional proteasomal pathways. These data provide conclusive evidence for mitochondrial dysfunction in GD and provide insight into the pathogenesis of PD and PD-GBA.

Efficient gene delivery to the adult and fetal CNS using pseudotyped non-integrating lentiviral vectors

Non-integrating lentiviral vectors show considerable promise for gene therapy applications as they persist as long-term episomes in non-dividing cells and diminish risks of insertional mutagenesis. In this study, non-integrating lentiviral vectors were evaluated for their use in the adult and fetal central nervous system of rodents. Vectors differentially pseudotyped with vesicular stomatitis virus, rabies and baculoviral envelope proteins allowed targeting of varied cell populations. Efficient gene delivery to discrete areas of the brain and spinal cord was observed following stereotactic administration. Furthermore, after direct in utero administration (E14), sustained and strong expression was observed 4 months into adulthood. Quantification of transduction and viral copy number was comparable when using non-integrating lentivirus and conventional integrating vector. These data support the use of non-integrating lentiviral vectors as an effective alternative to their integrating counterparts in gene therapy applications, and highlight their potential for treatment of inherited and acquired neurological disorders.

Nuclear Localisation Sequence Templated Nonviral Gene Delivery Vectors: Investigation of Intracellular Trafficking Events of LMD and LD Vector Systems†

The impact of a peptide that contains a nuclear localisation sequence (NLS) on intracellular DNA trafficking was studied. We used the adenoviral core peptide mu and an SV40 NLS peptide to condense plasmid DNA (pDNA) prior to formulation with 3β‐[N‐(N′, N′‐dimethylaminoethane)carbamoyl]cholesterol/dioleoyl‐L‐α‐phosphatidyl ethanolamine (DC‐Chol/DOPE) liposomes to give LMD and LND vectors, respectively. Fluorescent‐labelled lipid and peptides plus dye‐labelled pDNA components were used to investigate gene delivery in dividing and S‐phase growth‐arrested cells. Confocal microscopic analyses reveal little difference in intracellular trafficking events. Strikingly, mu peptide associates with nuclei and nucleoli of cells within less than 15 mins incubation of LMD with cells, which suggests that mu peptide has an NLS function. These NLS properties were confirmed by cloning of a mu‐β‐galactosidase fusion protein that localises in the nuclei of cells after cytosolic translation. In dividing cells both LMD and LND deliver pDNA(Cy3) to nuclei within 30–45 min incubation with cells. By contrast, pDNA is detected only in the cytoplasm in growth‐arrested cells over the period of time investigated, and not in the nuclei. LD systems prepared from DC‐Chol/DOPE cationic liposomes and pDNA(Cy3) behave similarly to LMD systems, which suggests that mu peptide is unable to influence trafficking events in this current LMD formulation, in spite of its strong NLS capacity. We further describe the effect of polyethyleneglycol (PEG) on cellular uptake. “Stealth” systems obtained by post‐coating LMD particles with fluorescent‐labelled PEG molecules (0.5, 5 and 10 mol % fluorescein‐PEG5000‐N‐hydroxysuccinimide) were prepared and shown to be internalised rapidly (mins) by cells, without detectable transgene expression. This result indicates that PEG blocks intracellular trafficking of pDNA.

Intravenous administration of AAV2/9 to the fetal and neonatal mouse leads to differential targeting of CNS cell types and extensive transduction of the nervous system

Several diseases of the nervous system are characterized by neurodegeneration and death in childhood. Conventional medicine is ineffective, but fetal or neonatal gene therapy may provide an alternative route to treatment. We evaluated the ability of single‐stranded and self‐complementary adeno‐associated virus pseudotype 2/9 (AAV2/9) to transduce the nervous system and target gene expression to specific neural cell types following intravenous injection into fetal and neonatal mice, using control uninjected age‐matched mice. Fetal and neonatal administration produced global delivery to the central (brain, spinal cord, and all layers of the retina) and peripheral (myenteric plexus and innervating nerves) nervous system but with different expression profiles within the brain; fetal and neonatal administration resulted in expression in neurons and protoplasmic astrocytes, respectively. Neither single‐stranded nor self‐complementary AAV2/9 triggered a microglia‐mediated immune response following either administration. In summary, intravenous AAV2/9 targets gene expression to specific neural cell types dependent on developmental stage. This represents a powerful tool for studying nervous system development and disease. Furthermore, it may provide a therapeutic strategy for treatment of early lethal genetic diseases, such as Gaucher disease, and for disabling neuropathies, such as preterm brain injury.—Rahim, A. A., Wong, A. M. S., Hoefer, K., Buckley, S. M. K., Mattar, C. N., Cheng, S. H., Chan, J. K. Y., Cooper, J. D., Waddington, S. N. Intravenous administration of AAV2/9 to the fetal and neonatal mouse leads to differential targeting of central nervous system cell types and extensive transduction of the nervous system. FASEB J. 25, 3505–3518 (2011). www.fasebj.org

Influence of Coagulation Factor X on In Vitro and In Vivo Gene Delivery by Adenovirus (Ad) 5, Ad35, and Chimeric Ad5/Ad35 Vectors

The binding of coagulation factor X (FX) to the hexon of adenovirus (Ad) 5 is pivotal for hepatocyte transduction. However, vectors based on Ad35, a subspecies B Ad, are in development for cancer gene therapy, as Ad35 utilizes CD46 (which is upregulated in many cancers) for transduction. We investigated whether interaction of Ad35 with FX influenced vector tropism using Ad5, Ad35, and Ad5/Ad35 chimeras: Ad5/fiber(f)35, Ad5/penton(p)35/f35, and Ad35/f5. Surface plasmon resonance (SPR) revealed that Ad35 and Ad35/f5 bound FX with approximately tenfold lower affinities than Ad5 hexon-containing viruses, and electron cryomicroscopy (cryo-EM) demonstrated a direct Ad35 hexon:FX interaction. The presence of physiological levels of FX significantly inhibited transduction of vectors containing Ad35 fibers (Ad5/f35, Ad5/p35/f35, and Ad35) in CD46-positive cells. Vectors were intravenously administered to CD46 transgenic mice in the presence and absence of FX-binding protein (X-bp), resulting in reduced liver accumulation for all vectors. Moreover, Ad5/f35 and Ad5/p35/f35 efficiently accumulated in the lung, whereas Ad5 demonstrated poor lung targeting. Additionally, X-bp significantly reduced lung genome accumulation for Ad5/f35 and Ad5/p35/f35, whereas Ad35 was significantly enhanced. In summary, vectors based on the full Ad35 serotype will be useful vectors for selective gene transfer via CD46 due to a weaker FX interaction compared to Ad5.

Systemic delivery of scAAV9 in fetal macaques facilitates neuronal transduction of the central and peripheral nervous systems

Correction of perinatally lethal neurogenetic diseases requires efficient transduction of several cell types within the relatively inaccessible CNS. Intravenous AAV9 delivery in mouse has achieved development stage-specific transduction of neuronal cell types, with superior neuron-targeting efficiency demonstrated in prenatal compared with postnatal recipients. Because of the clinical relevance of the non-human primate (NHP) model, we investigated the ability of AAV9 to transduce the NHP CNS following intrauterine gene therapy (IUGT). We injected two macaque fetuses at 0.9 G with 1 × 1013 vg scAAV9-CMV-eGFP through the intrahepatic continuation of the umbilical vein. Robust green fluorescent protein (GFP) expression was observed for up to 14 weeks in the majority of neurons (including nestin-positive cells), motor neurons and oligodendrocytes throughout the CNS, with a significantly lower rate of transduction in astrocytes. Photoreceptors and neuronal cell bodies in the plexiform and ganglionic retinal layers were also transduced. In the peripheral nervous system (PNS), widespread transduction of neurons was observed. Tissues harvested at 14 weeks showed substantially lower vector copy number and GFP levels, although the percentage of GFP-expressing cells remained stable. Thus, AAV9-IUGT in late gestation efficiently transduces both the CNS and PNS with neuronal predilection, of translational relevance to hereditary disorders characterized by perinatal onset of neuropathology.

Luciferin Detection After Intranasal Vector Delivery Is Improved by Intranasal Rather Than Intraperitoneal Luciferin Administration

In vivo bioimaging of transgenic luciferase in the lung and nose is an expedient method by which to continually measure expression of this marker gene after gene transduction. Its substrate, luciferin, is typically injected into the peritoneal cavity before bioimaging. Here we demonstrate that, compared with intraperitoneal injection, intranasal instillation of luciferin confers approximately an order of magnitude increase in luciferase bioluminescence detection in both lung and nose. This effect was observed after administration of viral vectors based on adenovirus type 5, adeno-associated virus type 8, and gp64-pseudotyped HIV lentivirus and, to a lesser extent, after nonviral polyethylenimine (PEI)-DNA delivery. Detection increased relative to the concentration of luciferin; however, a standard concentration of 15 mg/ml was well beyond the saturation point. Compared with intraperitoneal injection, intranasal instillation yields about a 10-fold increase in sensitivity with an approximate 30-fold reduction in luciferin usage when bioimaging in the nasal and pulmonary airways of mice.

Current therapies for the soluble lysosomal forms of neuronal ceroid lipofuscinosis

The NCLs (neuronal ceroid lipofuscinoses) are the most common inherited paediatric neurodegenerative disorder. Although genetically distinct, NCLs can be broadly divided into two categories: one in which the mutation results in a defect in a transmembrane protein, and the other where the defect lies in a soluble lysosomal enzyme. A number of therapeutic approaches are applicable to the soluble lysosomal forms of NCL based on the phenomenon of cross-correction, whereby the ubiquitously expressed mannose 6-phosphate/IGF (insulin-like growth factor) II receptor provides an avenue for endocytosis, trafficking and lysosomal processing of extracellularly delivered enzyme. The present review discusses therapeutic utilization of cross-correction by enzyme-replacement therapy, gene therapy and stem cell therapy for the NCLs, along with an overview of the recent progress in translating these treatments into the clinic.

In utero administration of Ad5 and AAV pseudotypes to the fetal brain leads to efficient, widespread and long-term gene expression

The efficient delivery of genetic material to the developing fetal brain represents a powerful research tool and a means to supply therapy in a number of neonatal lethal neurological disorders. In this study, we have delivered vectors based upon adenovirus serotype 5 (Ad5) and adeno-associated virus (AAV) pseudotypes 2/5, 2/8 and 2/9 expressing green fluorescent protein to the E16 fetal mouse brain. One month post injection, widespread caudal to rostral transduction of neural cells was observed. In discrete areas of the brain these vectors produced differential transduction patterns. AAV2/8 and 2/9 produced the most extensive gene delivery and had similar transduction profiles. All AAV pseudotypes preferentially transduced neurons whereas Ad5 transduced both neurons and glial cells. None of the vectors elicited any significant microglia-mediated immune response when compared with control uninjected mice. Whole-body imaging and immunohistological evaluation of brains 9 months post injection revealed long-term expression using these non-integrating vectors. These data will be useful in targeting genetic material to discrete or widespread areas of the fetal brain with the purpose of devising therapies for early neonatal lethal neurodegenerative disease and for studying brain development.

In vivo bioimaging with tissue-specific transcription factor activated luciferase reporters

The application of transcription factor activated luciferase reporter cassettes in vitro is widespread but potential for in vivo application has not yet been realized. Bioluminescence imaging enables non-invasive tracking of gene expression in transfected tissues of living rodents. However the mature immune response limits luciferase expression when delivered in adulthood. We present a novel approach of tissue-targeted delivery of transcription factor activated luciferase reporter lentiviruses to neonatal rodents as an alternative to the existing technology of generating germline transgenic light producing rodents. At this age, neonates acquire immune tolerance to the conditionally responsive luciferase reporter. This simple and transferrable procedure permits surrogate quantitation of transcription factor activity over the lifetime of the animal. We show principal efficacy by temporally quantifying NFκB activity in the brain, liver and lungs of somatotransgenic reporter mice subjected to lipopolysaccharide (LPS)-induced inflammation. This response is ablated in Tlr4−/− mice or when co-administered with the anti-inflammatory glucocorticoid analogue dexamethasone. Furthermore, we show the malleability of this technology by quantifying NFκB-mediated luciferase expression in outbred rats. Finally, we use somatotransgenic bioimaging to longitudinally quantify LPS- and ActivinA-induced upregulation of liver specific glucocorticoid receptor and Smad2/3 reporter constructs in somatotransgenic mice, respectively.