Adenovirus-mediated gene transfer and expression of human beta-glucuronidase gene in the liver, spleen, and central nervous system in mucopolysaccharidosis type VII mice

Gene Therapy for Lysosomal Storage Disorders: Ongoing Studies and Clinical Development

Rare monogenic disorders such as lysosomal diseases have been at the forefront in the development of novel treatments where therapeutic options are either limited or unavailable. The increasing number of successful pre-clinical and clinical studies in the last decade demonstrates that gene therapy represents a feasible option to address the unmet medical need of these patients. This article provides a comprehensive overview of the current state of the field, reviewing the most used viral gene delivery vectors in the context of lysosomal storage disorders, a selection of relevant pre-clinical studies and ongoing clinical trials within recent years.

C-Type Natriuretic Peptide Restores Growth Impairment Under Enzyme Replacement in Mice With Mucopolysaccharidosis VII

Growth impairment in mucopolysaccharidoses (MPSs) is an unresolved issue as it is resistant to enzyme replacement therapy (ERT) and growth hormone therapy. C-type natriuretic peptide (CNP) is a promising agent that has growth-promoting effects. Here we investigate the effects of CNP on growth impairment of MPSs using Gusbmps-2J mice, a model for MPS type VII, with combination therapy of CNP and ERT by hydrodynamic gene delivery. Although monotherapies were not sufficient to restore short statures of treated mice, combination therapy resulted in successful restoration. The synergistic effects of CNP and ERT were not only observed in skeletal growth but also in growth plates. ERT reduced cell swelling in the resting zone and increased cell number by accelerating proliferation or inhibiting apoptosis. CNP thickened the proliferative and hypertrophic zones. Regarding changes in the bone, ERT restored bone sclerosis through decreased bone formation and increased bone resorption, and CNP did not adversely affect this process. In addition, improvement of joint deformation by ERT was suggested by analyses of joint spaces and articular cartilage. CNP additively provided restoration of the short stature of MPS VII mice in combination with ERT, which improved abnormalities of growth plates and bone metabolism.

Dose-Dependent Prevention of Metabolic and Neurologic Disease in Murine MPS II by ZFN-Mediated In Vivo Genome Editing

Mucopolysaccharidosis type II (MPS II) is an X-linked recessive lysosomal disorder caused by deficiency of iduronate 2-sulfatase (IDS), leading to accumulation of glycosaminoglycans (GAGs) in tissues of affected individuals, progressive disease, and shortened lifespan. Currently available enzyme replacement therapy (ERT) requires lifelong infusions and does not provide neurologic benefit. We utilized a zinc finger nuclease (ZFN)-targeting system to mediate genome editing for insertion of the human IDS (hIDS) coding sequence into a "safe harbor" site, intron 1 of the albumin locus in hepatocytes of an MPS II mouse model. Three dose levels of recombinant AAV2/8 vectors encoding a pair of ZFNs and a hIDS cDNA donor were administered systemically in MPS II mice. Supraphysiological, vector dose-dependent levels of IDS enzyme were observed in the circulation and peripheral organs of ZFN+donor-treated mice. GAG contents were markedly reduced in tissues from all ZFN+donor-treated groups. Surprisingly, we also demonstrate that ZFN-mediated genome editing prevented the development of neurocognitive deficit in young MPS II mice (6-9 weeks old) treated at high vector dose levels. We conclude that this ZFN-based platform for expression of therapeutic proteins from the albumin locus is a promising approach for treatment of MPS II and other lysosomal diseases.

Skeletal response to lentiviral mediated gene therapy in a mouse model of MPS VII

Mucopolysaccharidosis VII (MPS VII) is an autosomal recessive, lysosomal storage disorder caused by β-glucuronidase (GUSB) deficiency, resulting in the accumulation of glycosaminoglycans (GAGs), in a variety of cell types. Severe, progressive skeletal pathology, termed dysostosis multiplex, is a prominent clinical feature of MPS VII. We have evaluated a gene therapy protocol for its efficacy in preventing the development and progression of bone pathology in MPS VII mice treated with a lentiviral vector at birth or at 7 weeks. Two weeks after injections, high levels of vector expression were observed in liver, spleen and bone marrow and to a lesser extent in kidney, lung and heart. Widespread clearance of GAG storage was observed in somatic tissues of both groups and some clearance of neuronal storage was observed in mice treated from birth. Micro-CT analysis demonstrated a significant decrease in vertebral and femoral bone mineral volume, trabecular number, bone surface density and cortical bone thickness in both treatment groups. Lumbar and femoral bone lengths were significantly decreased in untreated MPS VII mice, while growth plate heights were increased and these parameters did not change upon treatment. Small improvements in performance in the open field and rotarod behaviour tests were noted. Overall, systemic lentiviral-mediated gene therapy results in a measurable improvement in parameters of bone mass and architecture as well as biochemical and enzymatic correction. Conversely, growth plate chondrocytes were not responsive to treatment, as evidenced by the lack of improvement in vertebral and femoral bone length and growth plate height.

Emerging therapies for neurodegenerative lysosomal storage disorders - from concept to reality

Lysosomal storage disorders are inherited metabolic diseases in which a mutation in a gene encoding a lysosomal enzyme or lysosome-related protein results in the intra-cellular accumulation of substrate and reduced cell/tissue function. Few patients with neurodegenerative lysosomal storage disorders have access to safe and effective treatments although many therapeutic strategies have been or are presently being studied in vivo thanks to the availability of a large number of animal models. This review will describe the comparative advancement of a variety of therapeutic strategies through the 'research pipeline'. Our goal is to provide information for clinicians, researchers and patients/families alike on the leading therapeutic candidates at this point in time, and also to provide information on emerging approaches that may provide a safe and effective treatment in the future. The length of the pipeline represents the significant and sustained effort required to move a novel concept from the laboratory into the clinic.

Gene therapy for lysosomal storage disorders

INTRODUCTION

Lysosomal storage disorders (LSDs) encompass more than 50 distinct diseases, caused by defects in various aspects of lysosomal function. Neurodegeneration and/or dysmyelination are the hallmark of roughly 70% of LSDs. Gene therapy represents a promising approach for the treatment of CNS manifestations in LSDs, as it has the potential to provide a permanent source of the deficient enzyme, either by direct injection of vectors or by transplantation of gene-corrected cells. In this latter approach, the biology of neural stem/progenitor cells and hematopoietic cells might be exploited.

AREAS COVERED

Based on an extensive literature search up until March 2011, the author reviews and discusses the progress, the crucial aspects and the major challenges towards the development of novel gene therapy strategies aimed to target the CNS, with particular attention to direct intracerebral gene delivery and transplantation of neural stem/progenitor cells.

EXPERT OPINION

The implementation of viral vector delivery systems with specific tropism, regulated transgene expression, low immunogenicity and low genotoxic risk and the improvement in isolation and manipulation of relevant cell types to be transplanted, are fundamental challenges to the field. Also, combinatorial strategies might be required to achieve full correction in LSDs with neurological involvement.

The ependymal route for insulin-like growth factor-1 gene therapy in the brain

I.c.v. administration of the peptide insulin-like growth factor-1 (IGF-1) has been shown to be an effective neuroprotective strategy in the brain of different animal models, a major advantage being the achievement of high concentrations of IGF-1 in the brain without altering serum levels of the peptide. In order to exploit this therapeutic approach further, we used high performance recombinant adenoviral (RAd) vectors expressing their transgene under the control of the potent mouse cytomegalovirus immediate early (mCMV) promoter, to transduce brain ependymal cells with high efficiency and to achieve effective release of transgenic IGF-1 into the cerebrospinal fluid (CSF). We constructed RAd vectors expressing either a chimeric green fluorescent protein fused to HSV-1 thymidine kinase (TK/GFP)(fus), or the cDNA encoding rat IGF-1, both driven by the mCMV promoter. The vectors were injected into the lateral ventricles of young rats and chimeric GFP expression in brain sections was assessed by fluorescence microscopy. The ependymal cell marker vimentin was detected by immunofluorescence and nuclei were labeled with the DNA dye 4',6-diamidino-2-phenylindole. Blood and CSF samples were drawn at different times post-vector injection. In all cerebral ventricles, vimentin immunoreactive cells of the ependyma were predominantly transduced by RAd-(TK/GFP)(fus), showing nuclear and cytoplasmic expression of the transgene. For tanycytes (TK/GFP)(fus) expression was evident in their cytoplasmic processes as they penetrated deep into the hypothalamic parenchyma. I.c.v. injection of RAd-IGF-1 induced high levels of IGF-1 in the CSF but not in serum. We conclude that the ependymal route constitutes an effective approach for implementing experimental IGF-1 gene therapy in the brain.

Large animal models of neurological disorders for gene therapy

he development of therapeutic interventions for genetic disorders and diseases that affect the central nervous system (CNS) has proven challenging. There has been significant progress in the development of gene therapy strategies in murine models of human disease, but gene therapy outcomes in these models do not always translate to the human setting. Therefore, large animal models are crucial to the development of diagnostics, treatments, and eventual cures for debilitating neurological disorders. This review focuses on the description of large animal models of neurological diseases such as lysosomal storage diseases, Parkinsons disease, Huntingtons disease, and neuroAIDS. The review also describes the contributions of these models to progress in gene therapy research.

CNS-directed gene therapy for lysosomal storage diseases

Lysosomal storage diseases (LSDs) are a group of inherited metabolic disorders usually caused by deficient activity of a single lysosomal enzyme. As most lysosomal enzymes are ubiquitously expressed, a deficiency in a single enzyme can affect multiple organ systems, including the central nervous system (CNS). At least 75% of all LSDs have a significant CNS component. Approaches such as bone marrow transplantation (BMT) or enzyme replacement therapy (ERT) can effectively treat the systemic disease associated with LSDs in some patients. However, CNS disease remains a major challenge. Gene therapy represents a promising approach for the treatment of CNS disease as it has the potential to provide a permanent source of the deficient enzyme. Direct intracranial injection of viral gene transfer vectors has resulted in reduced lysosomal storage and functional improvement in certain small (rodent) and large (canine and feline) animal models of LSDs. The addition of protein transduction domains (PTDs) to the recombinant enzymes increased the distribution of enzyme and the extent of correction. Therapeutic levels of lysosomal enzymes can also be delivered to distant sites in the brain by anterograde and retrograde axonal transport. Finally, combining disparate approaches such as BMT and CNS-directed gene therapy can increase treatment efficacy in LSDs with severe CNS disease that are refractory to more conventional approaches.

CONCLUSION

The development of gene transfer vectors that mediate persistent expression in vivo, the addition of PTDs, a better understanding of lysosomal enzyme trafficking and combining different therapies provide hope that the CNS component of LSDs can be effectively treated.

Transduction of brain by herpes simplex virus vectors

An imposing obstacle to gene therapy is the inability to transduce all of the necessary cells in a target organ. This certainly applies to gene transfer to the brain, especially when one considers the challenges involved in scaling up transduction from animal models to use in the clinic. Non-neurotropic viral gene transfer vectors (e.g., adenovirus, adeno-associated virus, and lentivirus) do not spread very far in the nervous system, and consequently these vectors transduce brain regions mostly near the injection site in adult animals. This indicates that numerous, well-spaced injections would be required to achieve widespread transduction in a large brain with these vectors. In contrast, herpes simplex virus type 1 (HSV-1) is a promising vector for widespread gene transfer to the brain owing to the innate ability of the virus to spread through the nervous system and form latent infections in neurons that last for the lifetime of the infected individual. In this review, we summarize the published literature of the transduction patterns produced by attenuated HSV-1 vectors in small animals as a function of the injection site, and discuss the implications of the distribution for widespread gene transfer to the large animal brain.

Gene therapy for mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are due to deficiencies in activities of lysosomal enzymes that degrade glycosaminoglycans. Some attempts at gene therapy for MPS in animal models have involved intravenous injection of vectors derived from an adeno-associated virus (AAV), adenovirus, retrovirus or a plasmid, which primarily results in expression in liver and secretion of the relevant enzyme into blood. Most vectors can correct disease in liver and spleen, although correction in other organs including the brain requires high enzyme activity in the blood. Alternative approaches are to transduce hematopoietic stem cells, or to inject a vector locally into difficult-to-reach sites such as the brain. Gene therapy holds great promise for providing a long-lasting therapeutic effect for MPS if safety issues can be resolved.

Adeno-associated virus type 5 reduces learning deficits and restores glutamate receptor subunit levels in MPS VII mice CNS

A major challenge in treating lysosomal storage diseases with enzyme therapy is correcting symptoms in the central nervous system (CNS). This study used a murine model of mucopolysaccharidosis type VII (MPS VII) to test whether pathological and functional CNS defects could be corrected by expressing beta-glucuronidase via bilateral intrastriatal injection of adeno-associated virus type 5 (AAV5betagluc) vectors. After injecting AAV5betagluc, different brain regions expressed active beta-glucuronidase, which corrected lysosomal storage defects. Compared to age-matched littermates, adult MPS VII mice were impaired in spatial learning and memory, as measured by the repeated acquisition and performance chamber (RAPC) assay. AAV5betagluc-treated MPS VII mice improved significantly in the RAPC assay, relative to saline-injected littermates. Moreover, our studies reveal that cognitive changes in MPS VII mice correlate with decreased N-methyl-d-aspartate and alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid receptor expression. Importantly, AAV5betagluc delivery restored glutamate receptor levels. Together, these data demonstrate that AAV5 vectors deliver a therapeutically effective beta-glucuronidase gene to the CNS and further suggest a possible mechanism underlying spatial learning defects in MPS VII mice.

Metabolic correction in oligodendrocytes derived from metachromatic leukodystrophy mouse model by using encapsulated recombinant myoblasts

In an effort to develop an encapsulated cell-based system to deliver arylsulfatase A (ARSA) to the central nervous system of metachromatic leukodystrophy (MLD) patients, we engineered C2C12 mouse myoblasts with a retroviral vector containing a full-length human ARSA cDNA and evaluated the efficacy of the recombinant secreted enzyme to revert the MLD phenotype in oligodendrocytes (OL) of the As2-/- mouse model. After transduction, C2C12 cells showed a fifteen-fold increase in intracellular ARSA activity and five-fold increase in ARSA secretion. The secreted hARSA collected from transduced cells encapsulated in polyether-sulfone polymer, was taken up by enzyme-deficient OL derived from MLD mice and normally sorted to the lysosomal compartment, where transferred enzyme reached 80% of physiological levels, restoring the metabolism of sulfatide. To evaluate whether secreted enzyme could restore metabolic function in the brain, encapsulated cells and secreted ARSA were shown to be stable in CSF in vitro. Further, to test cell viability and enzyme release in vivo, encapsulated cells were implanted subcutaneously on the dorsal flank of DBA/2J mice. One month later, all retrieved implants released hARSA at rates similar to unencapsulated cells and contained well preserved myoblasts, demonstrating that encapsulation maintains differentiation of C2C12 cells, stable transgene expression and long-term cell viability in vivo. Thus, these results show the promising potential of developing an ARSA delivery system to the CNS based on the use of a polymer-encapsulated transduced xenogenic cell line for gene therapy of MLD.

Sphingolipid metabolism diseases

Human diseases caused by alterations in the metabolism of sphingolipids or glycosphingolipids are mainly disorders of the degradation of these compounds. The sphingolipidoses are a group of monogenic inherited diseases caused by defects in the system of lysosomal sphingolipid degradation, with subsequent accumulation of non-degradable storage material in one or more organs. Most sphingolipidoses are associated with high mortality. Both, the ratio of substrate influx into the lysosomes and the reduced degradative capacity can be addressed by therapeutic approaches. In addition to symptomatic treatments, the current strategies for restoration of the reduced substrate degradation within the lysosome are enzyme replacement therapy (ERT), cell-mediated therapy (CMT) including bone marrow transplantation (BMT) and cell-mediated "cross correction", gene therapy, and enzyme-enhancement therapy with chemical chaperones. The reduction of substrate influx into the lysosomes can be achieved by substrate reduction therapy. Patients suffering from the attenuated form (type 1) of Gaucher disease and from Fabry disease have been successfully treated with ERT.

Use of nonviral promoters in adenovirus-mediated gene therapy: reduction of lysosomal storage in the aspartylglucosaminuria mouse

BACKGROUND

Aspartylglucosaminuria (AGU) is a lysosomal storage disease with severe neurodegenerative clinical features resulting from the deficiency of lysosomal aspartylglucosaminidase (AGA). The AGU knockout mouse is a good model to test different therapy strategies, as it mimics well the human pathogenesis of the disease exhibiting storage vacuoles in all tissues. In this study we investigated the efficiency of nonviral promoters in adenovirus-mediated gene therapy.

METHODS

The deficient corrective enzyme, AGA, was expressed using two tissue-specific promoters, neuron-specific enolase (NSE), astrocyte-specific (GFAP) and the endogenous AGA promoter. An intrastriatal injection site was chosen due to its wide connections in the central nervous system (CNS). The expression of AGA was analyzed 1 week, 2 weeks, 4 weeks, 2 months and 4 months after the virus injection by lysosomal AGA-specific immunostaining. A correction of the lysosomal storage in the brain of treated mice was also studied using toluidine blue stained thin sections.

RESULTS

The overexpressed AGA enzyme was detected in addition to the injection site, also in the ipsilateral parietal cortex indicating migration of AGA in the brain tissue. Duration of AGA expression was markedly longer with all the viruses used compared to the green fluorescent protein (GFP) expression driven by the viral cytomegalovirus (CMV) promoter. In most animals the storage was decreased by at least 50% as compared to untreated AGU mouse brains. Remarkably, >90% correction of storage at the ipsilateral cortex was found with the NSE promoter at 4 weeks and 2 months after injection. Additionally, partial clearance of storage was demonstrated also in the contralateral side of the brain.

CONCLUSIONS

These data implicate that tissue-specific promoters are especially useful in virus-mediated gene therapy aiming at long-term gene expression.

Ex vivo cell-mediated gene therapy for metachromatic leukodystrophy using neurospheres

Metachromatic leukodystrophy (MLD) is an autosomal recessive disease caused by mutations in the gene encoding the lysosomal enzyme arylsulfatase A (ASA). In MLD, accumulation of the substrate, sulfated glycoprotein, in the central and peripheral nervous systems results in progressive motor and mental deterioration. Neural progenitor cells are thought to be useful for cell replacement therapy and for cell-mediated gene therapy in neurodegenerative diseases. In the present study, we examined the feasibility of ex vivo gene therapy for MLD using neural progenitor cells. Neural progenitor cells (neurospheres) were prepared from the striatum of E14 embryo MLD knockout mice or GFP transgenic mice and were transduced with the VSV pseudotyped HIV vector carrying the ASA gene (HIV-ASA). For in vivo study, neurospheres from GFP mice were transduced with HIV-ASA and inoculated into the brain parenchyma of adult MLD mice. HIV vector-transduced progenitor cells retained the potential for differentiation into neurons, astrocytes and oligodendrocytes in vitro. Expression of ASA in neurospheres transduced with HIV-ASA was confirmed by spectrophotometric enzyme assay and Western blotting. In vivo, GFP-positive cells were detectable 1 month after injection. These cells included GFAP- and MAP2-positive cells. Immunohistochemistry using anti-ASA antibody demonstrated localization of ASA in both GFP-positive and -negative cells. Partial clearance of accumulated sulfatide was confirmed in vivo in MLD knockout mice. The present findings suggest that ASA enzyme is released from migrated neurospheres and is able to digest sulfatide in surrounding cells. Our results suggest the potential of genetically engineered neural progenitor cells (neurospheres) for ex vivo therapy in MLD.

Gene therapy for lysosomal storage diseases

Lysosomal storage diseases (LSDs) comprise a diverse group of monogenetic disorders with complex clinical phenotypes that include both systemic and central nervous system pathologies. In recent years, the identification or development of mouse models recapitulating the clinical course of the LSDs has been instrumental in evaluating therapeutic strategies. Here, we review the various gene replacement strategies for target organs affected in many LSDs and describe briefly the various vector systems employed to test how best to accomplish long-lasting therapies for these fatal disorders.

Encapsulation Cell Therapy for Mucopolysaccharidosis Type VII Using Genetically Engineered Immortalized Human Amniotic Epithelial Cells

Mucopolysaccharidosis type VII (MPSVII) is a lysosomal storage disease resulted from a deficiency of the enzyme beta-glucuronidase (GUSB), which is necessary for degradation of glycosaminoglycans (GAGs). The deficiency of GUSB causes progressive accumulation of GAGs and subsequent lysosomal distension in multiple tissues, including the central nervous system (CNS). In murine experiments, bone marrow transplant, enzyme replacement, viral vectors, and genetically modified cells were successfully used for correction of the visceral accumulation of GAGs, but little improvement was seen in the brain, because these therapeutic agents cannot cross the blood-brain barrier (BBB). Although direct intracerebral injection of GUSB-encoding viral vectors has been developed to bypass the BBB, the possibility of tumor formation and the toxicity of over-expressed GUSB have been reported. In this study, we generated immortalized human amniotic epithelial (IHAE) cells to maintain the effect of implantation, and encapsulated these cells to prevent harmful immunological response and tumor formation and to regulate the level of GUSB expression within the host. Moreover, we generated IHAE cells that over-express and secrete human GUSB following transduction with an adenoviral vector encoding human GUSB. Therapeutic efficacy for MPSVII was evaluated in and ex vivo experiments using these encapsulated genetically engineered GUSB-encoding IHAE cells. We confirmed that encapsulated genetically engineered IHAE cells could secrete significant amounts of GUSB outside the capsule in vitro and into the cerebral parenchyma of C3H mice seven days after the capsule implantation. Thus, encapsulation cell therapy using genetically engineered IHAE cells is an effective armamentarium for the treatment of MPSVII.

Widespread gene transduction to the central nervous system by adenovirus in utero: implication for prenatal gene therapy to brain involvement of lysosomal storage disease

BACKGROUND

In some lysosomal storage diseases, considerable alterations of the central nervous system (CNS) occur prior to birth and neurodegeneration progresses rapidly soon after birth causing early death in patients. No effective treatment is available after birth. Treatment may need to be initiated before birth to prevent the onset or progression of neurological changes and thereby irreversible brain damage. The aim of this study is to investigate the feasibility and effectiveness of brain-directed prenatal gene therapy for lysosomal storage diseases.

METHODS

Recombinant adenovirus encoding the lacZ gene was injected into the lateral ventricles of mouse embryos and the pattern of gene transduction to the CNS was investigated. In the therapeutic experiment, adenovirus expressing beta-glucuronidase was injected into the cerebral ventricles of the embryos of mucopolysaccharidosis VII mice and the therapeutic effects on the brain were evaluated.

RESULTS

Injection of adenoviral vectors to the cerebral ventricles of mouse embryos led to widespread gene transduction throughout the brain and the spinal cord and transgene expression persisted over 10 months in those surviving the procedure. The prenatal transduction of the therapeutic gene to the brain of the mucopolysaccharidosis VII mouse efficiently prevented lysosomal storage in most brain cells before birth until 4 months after birth.

CONCLUSIONS

Brain-directed in utero gene therapy through an intra-ventricular route would be an effective strategy to treat some lysosomal storage diseases with early and severe CNS alterations.

Widespread correction of lysosomal storage following intrahepatic injection of a recombinant adeno-associated virus in the adult MPS VII mouse

Mucopolysaccharidosis type VII is a lysosomal storage disease caused by deficiency of the acid hydrolase beta-glucuronidase. MPS VII mice develop progressive lysosomal accumulation of glycosaminoglycans within multiple organs, including the brain. Using this animal model, we investigated whether gene transfer mediated by a recombinant adeno-associated virus (rAAV) type 2 vector is capable of reversing the progression of storage in adult mice. We engineered an rAAV2 vector to carry the murine beta-glucuronidase cDNA under the transcriptional direction of the human elongation factor-1alpha promoter. Intrahepatic administration of this vector in adult MPS VII mice resulted in stable hepatic beta-glucuronidase expression (473 +/- 254% of that found in wild-type mouse liver) for at least 1 year postinjection. There was widespread distribution of vector genomes and beta-glucuronidase within extrahepatic organs. The level of enzyme activity was sufficient to reduce lysosomal storage within the liver, spleen, kidney, heart, lung, and brain. Within selected regions of the brain, neuronal, glial, and perivascular cells had histopathologic evidence of reduced storage. Also, brain alpha-galactosidase and beta-hexosaminidase enzyme levels, secondarily elevated by the storage abnormality, were normalized. These data demonstrate that peripheral administration of an rAAV2 vector in adult MPS VII mice can lead to transgene expression levels sufficient for improvements in both the peripheral and the central manifestations of this disease.

Development of MPS IVA mouse (Galnstm(hC79S.mC76S)slu) tolerant to human N-acetylgalactosamine-6-sulfate sulfatase

Mucopolysaccharidosis IVA (MPS IVA) is an autosomal recessive disease caused by N-acetylgalactosamine-6-sulfate sulfatase (GALNS) deficiency. In recent studies of enzyme replacement therapy for animal models with lysosomal storage diseases, cellular and humoral immune responses to the injected enzymes have been recognized as major impediments to effective treatment. To study the long-term effectiveness and side effects of therapies in the absence of immune responses, we have developed an MPS IVA mouse model, which has many similarities to human MPS IVA and is tolerant to human GALNS protein. We used a construct containing both a transgene (cDNA) expressing inactive human GALNS in intron 1 and an active site mutation (C76S) in adjacent exon 2 and thereby introduced both the inactive cDNA and the C76S mutation into the murine Galns by targeted mutagenesis. Affected homozygous mice have no detectable GALNS enzyme activity and accumulate glycosaminoglycans in multiple tissues including visceral organs, brain, cornea, bone, ligament and bone marrow. At 3 months, lysosomal storage is marked within hepatocytes, reticuloendothelial Kupffer cells, and cells of the sinusoidal lining of the spleen, neurons and meningeal cells. The bone storage is also obvious, with lysosomal distention in osteoblasts and osteocytes lining the cortical bone, in chondrocytes and in the sinus lining cells in bone marrow. Ubiquitous expression of the inactive human GALNS was also confirmed by western blot using the anti-GALNS monoclonal antibodies newly produced, which resulted in tolerance to immune challenge with human enzyme. The newly generated MPS IVA mouse model should provide a good model to evaluate long-term administration of enzyme replacement.

Gene therapy for lysosomal storage diseases

The lysosomal storage diseases are a family of inherited disorders usually caused by a deficiency in a single lysosomal enzyme, and are characterised by progressive intralysosomal storage in multiple cell types. Although individual syndromes can be uncommon, as a whole this family of diseases affects approximately 1 in 3,000 live births. The severity of disease can be variable, ranging from minimal evidence of lysosomal storage to widespread multi-system involvement and early mortality. Although the enzymatic defects responsible for most of these diseases are known, treatment options for the majority of these disorders are limited to supportive care and genetic counselling. Knowledge of the genetic defects underlying these diseases, coupled with advances in the fields of gene transfer and expression, provide an opportunity to utilise gene therapy strategies in order to treat these disorders. Here we provide a description of the biochemical and molecular basis of gene therapy for lysosomal storage diseases, as well as an overview of some of the in vitro and in vivo studies that have been performed.

Correction of metabolic, craniofacial, and neurologic abnormalities in MPS I mice treated at birth with adeno-associated virus vector transducing the human alpha-L-iduronidase gene

Murine models of lysosomal storage diseases provide an opportunity to evaluate the potential for gene therapy to prevent systemic manifestations of the disease. To determine the potential for treatment of mucopolysaccharidosis type I using a gene delivery approach, a recombinant adeno-associated virus (AAV) vector, vTRCA1, transducing the human iduronidase (IDUA) gene was constructed and 1 x 10(10) particles were injected intravenously into 1-day-old Idua(-/-) mice. High levels of IDUA activity were present in the plasma of vTRCA1-treated animals that persisted for the 5-month duration of the study, with heart and lung of this group demonstrating the highest tissue levels of gene transfer and enzyme activity overall. vTRCA1-treated Idua(-/-) animals with measurable plasma IDUA activity exhibited histopathological evidence of reduced lysosomal storage in a number of tissues and were normalized with respect to urinary GAG excretion, craniofacial bony parameters, and body weight. In an open field test, vTRCA1-treated Idua(-/-) animals exhibited a significant reduction in total squares covered and a trend toward normalization in rearing events and grooming time compared to control-treated Idua(-/-) animals. We conclude that AAV-mediated transduction of the IDUA gene in newborn Idua(-/-) mice was sufficient to have a major curative impact on several of the most important parameters of the disease.

Transduction of the Choroid Plexus and Ependyma in Neonatal Mouse Brain by Vesicular Stomatitis Virus Glycoprotein-Pseudotyped Lentivirus and Adeno-Associated Virus Type 5 Vectors

Evaluation of gene transfer into the developing mouse brain has shown that when adeno-associated virus serotype 1 (AAV1) or AAV2 vectors are injected into the cerebral lateral ventricles at birth, widespread parenchymal transduction occurs. Lentiviral vectors have not been tested by this route. In this study, we found that injection of lentiviral vectors pseudotyped with vesicular stomatitis virus glycoprotein (VSV-G) resulted in targeted transduction of the ependymal cells lining the ventricular system and the choroid plexus along the entire rostrocaudal axis of the brain, whereas a Mokola pseudotype transduced only a few cells after injection into the neonatal ventricle. In contrast, when lentiviral vectors pseudotyped with either VSV-G or Mokola glycoprotein are injected into the adult mouse brain, they transduce similar patterns of cells. An Ebola-Zaire-pseudotyped vector did not transduce any neonatal CNS cells, as was also the case for adult parenchymal injections. Long-term gene expression (12 months) occurred with a constitutively active mammalian promoter and a self-inactivating long terminal repeat (LTR), whereas the cytomegalovirus promoter in a vector with an intact LTR was expressed only in short-term experiments. We found that an AAV5 vector also targeted the ependymal and choroid plexus cells throughout the ventricular system. This vector exhibited limited penetration from the ventricle to other structures, which was significantly different from the previously reported patterns of transduction after intraventricular injection of AAV1 and AAV2 vectors.

AAV-mediated intravitreal gene therapy reduces lysosomal storage in the retinal pigmented epithelium and improves retinal function in adult MPS VII mice

The beta-glucuronidase-deficient mucopolysaccharidosis type VII (MPS VII) mouse accumulates partially degraded glycosaminoglycans in many cell types, including retinal pigmented epithelial (RPE) cells in the eye. This lysosomal storage in RPE cells leads to progressive retinal degeneration and reduced function as measured by flash electroretinography (ERG). The impact of AAV-mediated intraocular gene therapy on pathology and retinal function was examined in normal and MPS VII mice treated at 4 weeks of age, when lysosomal storage is evident but functional impairment is minimal in affected animals. At 16 weeks, an age at which untreated MPS VII mice have advanced histologic lesions and significantly reduced ERG amplitudes, treated eyes had nearly normal levels of beta-glucuronidase activity, preservation of cells in the outer nuclear layer of the retina, and decreased lysosomal storage within the RPE. The AAV-treated MPS VII mice also had significantly increased dark-adapted ERG amplitudes compared to untreated MPS VII mice. Although retinal function was improved, the efficacy of the treatment depended heavily on parameters related to the injection procedure, such as the injection volume, injection site, and vector dose. These data suggest that intraocular AAV-mediated therapy may be efficacious for treating the retinal disease associated with certain lysosomal storage diseases.

Liver-Directed Adenoviral Gene Transfer in Murine Succinate Semialdehyde Dehydrogenase Deficiency

Murine succinate semialdehyde dehydrogenase (SSADH) deficiency (OMIM 271980; EC 1.2.1.24), a model of the corresponding human disorder, displays 100% mortality at weeks 3-4 of life, associated with lethal tonic-clonic seizures. The biochemical hallmark, gamma-hydroxybutyrate (GHB), accumulates in both human and murine disorders. In the current study we evaluated rescue of the murine model with liver-directed gene therapy using the E1-deleted adenoviral vector AD:pAD-RSV-humanSSADH. Our working hypotheses were: (1) liver expresses considerable SSADH activity and therefore represents a major source of GHB output, (2) correction of liver enzyme deficiency will reduce GHB load both peripherally and in the central nervous system, and (3) SSADH expression will improve survival. SSADH(-/-) and SSADH(+/+) mice were treated under two protocols: (A) intraperitoneal injection of 10(8)-10(11) viral particles by day 10 of life or (B) retro-orbital injection of 10(11) viral particles at day 13 of life. Intravenous administration was prohibited by the small size and fragility of the mice. Maximal survival (39%; P<0.001) was achieved with intraperitoneal administration (10(8) particles) at day 10; intraperitoneal (10(10) and 10(11) particles) and retro-orbital administration (10(11) particles) yielded lower survival of 11-25% (P<0.02). Under both protocols, the maximal hepatic SSADH enzyme activity was approximately 20% of SSADH(+/+) liver activity (retro-orbital > ip). At various time points postinjection, ip-treated animals (10(8) viral particles) demonstrated upward of 80% reduction in liver GHB concentrations, with little impact on brain or serum GHB levels except at 48-72 h posttreatment (approximately 50% reduction for both tissues). Accordingly, we harvested retro-orbitally treated animals at 72 h and observed significant reductions of 60-70% for GHB in liver, kidney, serum, and brain extracts. Histochemical analysis of liver from retro-orbitally treated mutants demonstrated substantial SSADH staining, but with variability both within tissues and between animals. Our studies provide proof-of-principle that liver-mediated gene therapy has efficacy in treating SSADH deficiency and that hepatic tissue contributes significantly to the pool of GHB within the CNS.

Gene transfer to the nervous system: prospects for novel treatments directed at diseases of the aging nervous system

In the past 3 decades, gene therapy has moved from a theoretical construct to an active field of basic research, animal studies, and clinical trials. In this article, we describe the conceptual basis underlying the use of gene therapy for diseases of the aging nervous system, the principal techniques used for gene delivery, and review preclinical animal studies in 4 different classes of neurologic dysfunction: 1) focal neuronal degeneration in the central nervous system; 2) global neuronal dysfunction in the central nervous system; 3) degenerative disease affecting components of the peripheral nervous system; and 4) intractable focal pain. The full potential of this approach will not be established until the human trials are completed.

Improvement of skeletal lesions in mice with mucopolysaccharidosis type VII by neonatal adenoviral gene transfer

Neonatal gene transfer using adenovirus vectors expressing human beta-glucuronidase (AxCAhGUS) resulted in pathological improvement in multiple visceral organs of mice with mucopolysaccharidosis type VII (MPSVII). However, the therapeutic effect on skeletal deformities and growth retardation, the major clinical symptoms in MPSVII, was not fully investigated by biochemical and histopathological analyses. In this study, we injected AxCAhGUS into a murine model of MPSVII (B6/MPSVII) within 24 h of birth and evaluated the therapeutic effects on skeletal deformities and growth retardation. High levels of beta-glucuronidase (GUSB) activity (approximately threefold higher than normal GUSB activity) were observed in the articular cartilage of the mice 30 days after the treatment. Histopathological study in the knee joints showed elimination of vacuole cells in the articular cartilage and growth plate. Subchondral bone near the articular surface was almost normal in the treated MPSVII mice. Long-term observation (for 140 days after treatment) indicated that characteristic phenotypes such as flattened face, hunched stature, and shortening of bone length in the treated mice were almost normal. These results demonstrate that a single injection of adenovirus vector into neonatal MPSVII mice is sufficient for long-term normalization of skeletal deformities and effective in pathological correction of the articular cartilage and growth plate.

Gene transfer strategies for correction of lysosomal storage disorders

Lysosomal storage diseases (LSDs) represent a large group of monogenic disorders of metabolism, which affect approximately 1 in 5000 live births. LSDs result from a single or multiple deficiency of specific lysosomal hydrolases, the enzymes responsible for the luminal catabolization of macromolecular substrates. The consequent accumulation of undigested metabolites in lysosomes leads to polysystemic dysfunction, including progressive neurologic deterioration, mental retardation, visceromegaly, blindness, and early death. In general, the residual amount of functional enzyme in lysosomes determines the severity and age at onset of the clinical symptoms, implying that even modest increases in enzyme activity might affect a cure. A key feature on which therapy for LSDs is based is the ability of soluble enzyme precursors to be secreted by one cell type and reinternalize by neighboring cells via receptor-mediated endocytosis and routed to lysosomes, where they function normally. In principle, somatic gene therapy could be the preferred treatment for LSDs if the patient's own cells could be genetically modified in vitro or in vivo to constitutively express high levels of the correcting enzyme and become the source of the enzyme in the patient. Both ex vivo and in vivo gene transfer methods have been experimented with for gene therapy of lysosomal disorders. Several of these methods have proved efficient for the transfer of genetic material into deficient cells in culture and reconstitution of enzyme activity. However, the same methods applied to humans or animal models have been giving inconsistent results, the bases of which are not fully understood. A broader knowledge of disease pathogenesis, facilitated by available, faithful animal models of LSDs, coupled to the development of better gene transfer systems as well as the understanding of vector host interactions will make somatic gene therapy for these devastating and complex diseases the most suitable therapeutic approach.

Attenuation of ganglioside GM1 accumulation in the brain of GM1 gangliosidosis mice by neonatal intravenous gene transfer

A single intravenous injection with 4 x 10(7) PFU of recombinant adenovirus encoding mouse beta-galactosidase cDNA to newborn mice provided widespread increases of beta-galactosidase activity, and attenuated the development of the disease including the brain at least for 60 days. The beta-galactosidase activity showed 2-4 times as high a normal activity in the liver and lung, and 50 times in the heart. In the brain, while the activity was only 10-20% of normal, the efficacy of the treatment was distinct. At the 30th day after the injection, significant attenuation of ganglioside GM1 accumulation in the cerebrum was shown in three out of seven mice. At the 60th day after the injection, the amount of ganglioside GM1 was above the normal range in all treated mice, which was speculated to be the result of reaccumulation. However, the values were still definitely lower in most of the treated mice than those in untreated mice. In the histopathological study, X-gal-positive cells, which showed the expression of exogenous beta-galactosidase gene, were observed in the brain. It is noteworthy that neonatal administration via blood vessels provided access to the central nervous system because of the incompletely formed blood-brain barrier.

Enzyme replacement therapy in mucopolysaccharidosis type II (Hunter syndrome): a preliminary report

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is an X-linked disease caused by a deficiency of the enzyme iduronate-2-sulphatase (IDS), which results in the lysosomal accumulation of glycosaminoglycans (GAG). This paper describes a knockout mouse model of MPS II which has been used to assess the effect of enzyme replacement therapy. Therapy with IDS results in a marked decrease in urinary GAGs, as well as reduced GAG accumulation in several tissues. These studies have been used to support the first clinical trial of recombinant IDS in patients with Hunter syndrome.

Production of MPS VII mouse (Gus(tm(hE540A x mE536A)Sly)) doubly tolerant to human and mouse beta-glucuronidase

Mucopolysaccharidosis VII (MPS VII, Sly syndrome) is an autosomal recessive lysosomal storage disease caused by beta-glucuronidase (GUS) deficiency. A naturally occurring mouse model of that disease has been very useful for studying experimental approaches to therapy. However, immune responses can complicate evaluation of the long-term benefits of enzyme replacement or gene therapy delivered to adult MPS VII mice. To make this model useful for studying the long-term effectiveness and side effects of experimental therapies delivered to adult mice, we developed a new MPS VII mouse model, which is tolerant to both human and murine GUS. To achieve this, we used homologous recombination to introduce simultaneously a human cDNA transgene expressing inactive human GUS into intron 9 of the murine Gus gene and a targeted active site mutation (E536A) into the adjacent exon 10. When the heterozygote products of germline transmission were bred to homozygosity, the homozygous mice expressed no GUS enzyme activity but expressed inactive human GUS protein highly and were tolerant to immune challenge with human enzyme. Expression of the mutant murine Gus gene was reduced to about 10% of normal levels, but the inactive murine GUS enzyme also conferred tolerance to murine GUS. This MPS VII mouse model should be useful to evaluate therapeutic responses in adult mice receiving repetitive doses of enzyme or mice receiving gene therapy as adults. Heterozygotes expressed only 9.5-26% of wild-type levels of murine GUS instead of the expected 50%, indicating a dominant-negative effect of the mutant enzyme monomers on the activity of GUS tetramers in different tissues. Corrective gene therapy in this model should provide high enough levels of expression of normal GUS monomers to overcome the dominant negative effect of mutant monomers on newly synthesized GUS tetramers in most tissues.

Therapeutic gene transfer to the nervous system using viral vectors

The past few years have been marked by substantial progress in preclinical studies of therapeutic gene transfer for neurologic disease using viral-based vectors. In this article, the authors review the data regarding (1). treatment of focal neuronal degeneration, exemplified by Parkinson disease, ischemia, and trauma models; (2). treatment of global neurologic dysfunction, exemplified by the mucopolysaccharidoses and other storage diseases; (3). peripheral nervous system diseases including motor neuron disease and sensory neuropathies; and (4). the use of vectors expressing neurotransmitters to modulate functional neural activity in the treatment of pain. The results suggest that a number of different viral vectors may be appropriate for gene transfer to the central nervous system for specific disease processes, and that for the peripheral nervous system herpes simplex virus-based vectors appear to have special utility. The results of the first human gene therapy trials for neurologic disease, which are just now beginning, will be crucial in defining the next step in the development of this therapy.

Plasmid-based gene transfer ameliorates visceral storage in a mouse model of Sandhoff disease

Sandhoff disease is a severe neurodegenerative disorder with visceral involvement caused by mutations in the HEXB gene coding for the beta subunit of the lysosomal hexosaminidases A and B. HEXB mutations result in the accumulation of undegraded substrates such as GM2 and GA2 in lysosomes. We evaluated the efficacy of cationic liposome-mediated plasmid gene therapy using the Sandhoff disease mouse, an animal model of a human lysosomal storage disease. The mice received a single intravenous injection of two plasmids, encoding the human alpha and beta subunits of hexosaminidase cDNAs. As a result, 10-35% of normal levels of hexosaminidase expression, theoretically therapeutic levels, were achieved in most visceral organs, but not in the brain, 3 days after injection with decreased levels by day 7. Histochemical staining confirmed widespread enzyme activity in visceral organs. Both GA2 and GM2 were reduced by almost 10% and 50%, respectively, on day 3, and by 60% and 70% on day 7 compared with untreated age-matched Sandhoff disease mice. Consistent with the biochemical results, a reduction in GM2 was observed in liver cells histologically as well. These initial findings support further development of the plasmid gene therapy against lysosomal diseases with visceral pathology.

Long-term normalization in the central nervous system, ocular manifestations, and skeletal deformities by a single systemic adenovirus injection into neonatal mice with mucopolysaccharidosis VII

Systemic injection of an adenovirus vector into adult mice resulted in pathological improvements in multiple visceral organs of mice with mucopolysaccharidosis VII; however, no therapeutic efficacy was observed for mental retardation, skeletal deformities, corneal clouding, and retinal degeneration. In this study, an adenovirus vector expressing human beta-glucuronidase was injected into mice with mucopolysaccharidosis VII within 24 h of birth, and therapeutic efficacy was evaluated. In the brains of the mice, more than 20% of GUSB activity was maintained for at least 20 weeks after birth, and histopathological analysis showed no obvious lysosomal storage. Furthermore, no vacuolated cells were detected in corneal stroma and retinal pigment epithelium in the eyes of the mice treated in the neonatal period, while pathological improvement was not observed in adult MPSVII mice that received similar treatments. The treated mice also lacked characteristic facial skeletal deformities, and radiographic analysis demonstrated that their facial and cranial bones were morphologically normal. These results indicate that a single systemic adenovirus injection in the neonatal period could prevent the progression of mental retardation, corneal clouding, retinal degeneration, and skeletal deformities, all of which are frequently observed clinical manifestations and difficult to treat in adulthood.

Evaluation of pathological manifestations of disease in mucopolysaccharidosis VII mice after neonatal hepatic gene therapy

Mucopolysaccharidosis VII (MPS VII) is a lysosomal storage disease caused by beta-glucuronidase (GUSB) deficiency. Intravenous injection of a retroviral vector expressing canine GUSB into neonatal MPS VII mice resulted in transduction of 6 to 35% of hepatocytes, which secreted GUSB into blood. Serum GUSB activity was stable for 6 months at 600 (low expression) to 10,000 (high expression) U/ml, and enzyme was modified appropriately with mannose 6-phosphate. The average serum GUSB activity (3531 U/ml) is the highest long-term expression reported for MPS VII mice after gene therapy. Secreted enzyme was taken up by other tissues, as the average enzyme activity was >13% of normal in somatic organs and 2% of normal in brain. Low expression markedly reduced histopathological evidence of lysosomal storage in liver, spleen, kidney, small intestine, neurons, and glial cells. High expression appeared to be more effective than low expression at reducing lysosomal storage in aorta, heart valves, thymus, bronchial epithelium, cornea, and retinal pigmented epithelium. Future experiments will determine if greater pathological improvements will consistently be observed in retrovirus-treated MPS VII mice with higher serum GUSB activity relative to animals with lower activity and if these result in clinical benefits.

Therapeutic neonatal hepatic gene therapy in mucopolysaccharidosis VII dogs

Dogs with mucopolysaccharidosis VII (MPS VII) were injected intravenously at 2-3 days of age with a retroviral vector (RV) expressing canine beta-glucuronidase (cGUSB). Five animals received RV alone, and two dogs received hepatocyte growth factor (HGF) before RV in an attempt to increase transduction efficiency. Transduced hepatocytes expanded clonally during normal liver growth and secreted enzyme with mannose 6-phosphate. Serum GUSB activity was stable for up to 14 months at normal levels for the RV-treated dogs, and for 17 months at 67-fold normal for the HGF/RV-treated dog. GUSB activity in other organs was 1.5-60% of normal at 6 months for two RV-treated dogs, which was likely because of uptake of enzyme from blood by the mannose 6-phosphate receptor. The body weights of untreated MPS VII dogs are 50% of normal at 6 months. MPS VII dogs cannot walk or stand after 6 months, and progressively develop eye and heart disease. RV- and HGF/RV-treated MPS VII dogs achieved 87% and 84% of normal body weight, respectively. Treated animals could run at all times of evaluation for 6-17 months because of improvements in bone and joint abnormalities, and had little or no corneal clouding and no mitral valve thickening. Despite higher GUSB expression, the clinical improvements in the HGF/RV-treated dog were similar to those in the RV-treated animals. This is the first successful application of gene therapy in preventing the clinical manifestations of a lysosomal storage disease in a large animal.

Gene therapy for the central nervous system in the lysosomal storage disorders

Although great promise has been made in the field of gene therapy, a number of difficulties must be solved before successful human studies can be completed. These issues involve safety, immunological reactions to the vectors and their transgene products, persistent transgene expression, and ability to repeat administrations of the vector safely. A major hurdle that must be overcome is the ubiquitous delivery of the transgene throughout the nervous system. Significant gene delivery to the CNS of murine models of LSD has been accomplished, but we await the successful treatment of the nervous system in a larger mammalian model of LSD. As yet there is no perfect vector that can solve all of these problems. It is likely that vector technology will evolve into hybrid vectors also using synthetic components that will increase safety and efficacy of recombinant vectors. The treatment of the CNS remains complicated, but progress is being made in this area. Clinical trials already planned will give us increasing information as to the ideal gene therapy for the CNS.

Critical issues in gene therapy for neurologic disease

Gene therapy for the nervous system is a newly emerging field with special issues related to modes of delivery, potential toxicity, and realistic expectations for treatment of this vital and highly complex tissue. This review focuses on the potential for gene delivery to the brain, as well as possible risks and benefits of these procedures. This includes discussion of appropriate vectors, such as adeno-associated virus, lentivirus, gutless adenovirus, and herpes simplex virus hybrid amplicons, and cell vehicles, such as neuroprogenitor cells. Routes of delivery for focal and global diseases are enumerated, including use of migratory cells, facilitation of vascular delivery across the blood-brain barrier, cerebrospinal fluid delivery, and convection injection. Attention is given to examples of diseases falling into different etiologic types: metabolic deficiency states, including Canavan disease and lysosomal storage disorders; and degenerative conditions, including Parkinson's disease and other neurodegenerative conditions.

Long-term expression of beta-glucuronidase by genetically modified human neural progenitor cells grafted into the mouse central nervous system

Mucopolysaccharidosis type VII (MPS VII) is an inherited disease caused by beta-glucuronidase (beta-glu) deficiency. This deficiency results in the lysosomal accumulation of glycosaminoglycans in all tissues and affects a wide range of organs, including the central nervous system (CNS). Gene transfer is a promising approach to therapy for MPS VII because it allows extensive delivery of the enzyme to the affected tissues. We studied neurotransplantation of primary human cells to supply beta-glucuronidase to the CNS. Human neural progenitor cells (HNPC) were amplified and cotransduced with two lentiviral vectors, one encoding the green fluorescent protein and the other the human beta-glu. We show that these cells strongly expressed both transgenes in culture. When grafted into the mouse striatum, HNPC differentiated into neurons and astrocytes and expressed the two transgenes for at least 6 months. This study therefore paves the way for the treatment of MPS VII by long-term delivery of the appropriate enzyme.

Aquaporin gene delivery to kidney

BACKGROUND

Several aquaporin- (AQP) type water channels are expressed in kidney tubules and microvessels, including AQP1 in proximal tubule, thin descending limb of Henle and vasa recta, AQP2 in collecting duct apical membrane, and AQP3 and AQP4 in collecting duct basolateral membrane. Mice deficient in these aquaporins have distinct phenotypic abnormalities. AQP1 null mice are polyuria and unable to generate a concentrated urine after water deprivation. AQP2-T126M mutant mice and AQP3 null mice manifest nephrogenic diabetes insipidus (NDI) with severe polyuria, whereas AQP4 null mice have only a mild defect in maximal urinary concentrating ability. We reasoned that these mice could serve as useful models for gene replacement because of their predictable and unambiguous phenotypes.

METHODS

In an initial feasibility study, an adenovirus directing the expression of AQP1 was introduced into AQP1 null mice by intravenous infusion.

RESULTS

At 1 week after adenovirus infusion, AQP1 was seen in many proximal tubules and microvessels. Compared with untreated null mice, the treated mice were able to partially concentrate their urine and lost less weight after water deprivation. However, AQP1 transgene expression and functional correction were lost over 3-5 weeks.

CONCLUSION

Although there remain many technical problems to overcome, aquaporin gene replacement has potential applications in hereditary and acquired NDI, and in the transient modulation of renal fluid conservation.

Suppression of tumor growth following intralesional therapy with TRAIL recombinant adenovirus

TRAIL is a member of the tumor necrosis factor superfamily that induces apoptosis in a variety of tumor cell types both in vitro and in vivo, while demonstrating minimal cytotoxicity toward normal tissues. One disadvantage to previous in vivo protocols was the need for large quantities of TRAIL to suppress tumor growth. Here we engineered a replication-deficient adenovirus to encode human TNFSF10 (Ad5-TRAIL) as an alternative to recombinant, soluble TRAIL protein. The results show that TRAIL-sensitive prostate tumor cell targets infected with Ad5-TRAIL undergo apoptosis through the production and expression of TRAIL protein. This activity was limited to TRAIL-sensitive tumor cells, as normal prostate epithelial cells were not killed by Ad5-TRAIL. Furthermore, in vivo administration of Ad5-TRAIL at the site of tumor implantation suppressed the outgrowth of human prostate tumor xenografts in SCID mice. Histologic examination of prostate tumors treated locally with Ad5-TRAIL revealed areas of apoptosis within 24 hours of injection. These results further define Ad5-TRAIL as a novel anti-tumor therapeutic and demonstrate its potential use as a means for treating prostate tumors, as well as other solid tumors, in vivo.

Detection of the exogenous hGDNF in gerbils under the treatment with AxCAhGDNF adenoviral vector

Glial cell line-derived neurotrophic factor (GDNF) is one of the most potent neurotrophic factors and promotes survival in many populations of cells. We examined the neuroprotective effect of an adenoviral vector encoding glial cell line-derived neurotrophic factor (AxCAhGDNF) on the transient global ischemia [Brain Res. 885 (2000) 273-282]. Gerbils received AxCAhGDNF or an adenoviral vector encoding bacterial beta-galactosidase gene (AxCALacZ) through administration into the lateral ventricle. Two days later, occlusion of the common carotid arteries for 5 min bilaterally using aneurysm clips produced transient global forebrain ischemia. Animals showed intense immunolabeling for GDNF in ependymal cells on 2, 4 and 7 days after the operation. The exogenous gene transducted by the adenovirus in the same cells was detected by in situ hybridization. The treatment with AxCAhGDNF significantly prevented the loss of hippocampal CA-1 pyramidal neurons 2 to 7 days after the operation, as compared to AxCALacZ treatment. Also terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick end labeling (TUNEL) staining was markedly reduced in the case with AxCAhGDNF treatment at 7 days after the operation. In this paper, we describe in detail the techniques for the detection of the exogenous gene of hGDNF under the treatment with AxCAhGDNF.

Genetically modified bone marrow continuously supplies anti-inflammatory cells and suppresses renal injury in mouse Goodpasture syndrome

In chronic inflammation, macrophages and neutrophils, which are derived from bone marrow, play a pivotal role. Therefore, reconstitution of bone marrow with anti-inflammatory stem cells may modify inflammation. In this study, transplantation-based gene therapy was applied to glomerular inflammation for a long-lasting suppression of the glomerular damage seen in chronic nephritis. Bone marrow cells were harvested from male donor mice, which had received 5-fluorouracil 3 days previously, and transduced with an interleukin 1 (IL-1) receptor antagonist (IL-1Ra) or a mock gene using a retrovirus vector. After confirmation that transduced cells possessed the transgene at approximately 0.7 copies per cell and secreted recombinant IL-1Ra, these cells were infused into sublethally irradiated (6 Gy) female recipients once daily for 4 consecutive days. These female recipient mice had the male Y antigen in bone marrow, liver, and spleen, and 10% to 20% of their spleen cells possessed the transgene even 8 weeks after transplantation. Glomerulonephritis was then induced in these mice. Renal function and histology were retarded in the mice whose bone marrow was reconstituted with IL-1Ra-producing cells compared with mock transduced cells. In situ hybridization using a Y painting probe revealed that transplanted donor cells were recruited into the glomerulus upon induction of nephritis, suggesting therapeutic effects were channeled through the secretion of IL-1Ra from these cells. Furthermore, the survival rate after a second challenge with nephrotoxic antibody was significantly improved in the IL-1Ra chimera. These results suggest that reconstitution of bone marrow for continuous supply of anti-inflammatory cells may be a useful strategy for the treatment of chronic inflammation.

Tetracycline-regulatable adenovirus vectors: pharmacologic properties and clinical potential

Stringent control of gene expression in human gene therapy strategies is important for both therapeutic and safety reasons. Replication-defective vectors derived from adenoviruses have been shown to be capable of highly efficient in vivo gene delivery to a wide variety of dividing and nondividing human cells. Here, we review the progress in the development of regulatable adenovirus vectors that allow gene expression to be tightly controlled by low concentrations of tetracyclines. As an example of the potential clinical utility of this technology, we highlight our results obtained in an immunotherapy model for prostate cancer with a tetracycline-regulatable adenovirus vector expressing the cytokine interleukin-12. Recombinant adenovirus vectors with tetracycline-regulatable gene expression provide new opportunities and improved safety for gene therapy applications in humans.

Simultaneous, two-color fluorescence detection of total protein profiles and beta-glucuronidase activity in polyacrylamide gel

A dichromatic method for measuring the specific activity of beta-glucuronidase from complex cell homogenates or partially purified protein fractions is presented. Dual fluorescence is achieved by using the green emitting fluorogenic substrate ELF 97 beta-D-glucuronide to detect beta-glucuronidase activity, followed by the red emitting SYPRO Ruby protein gel stain or SYPRO Ruby IEF gel stain to detect the remaining proteins in the electrophoretic profile. Both ELF 97 alcohol, the highly fluorescent hydrolytic product generated from the enzyme substrate, and the SYPRO Ruby total protein stains are maximally excited by ultraviolet illumination. ELF 97 alcohol emits maximally at 525 nm while the SYPRO Ruby dyes emit maximally at 610 nm. Since ELF 97 beta-glucuronide is a precipitating substrate, it allows precise localization of beta-glucuronidase activity with minimal band diffusion. The staining method is simple and direct, without the requirement for ancillary coupling reactions. Dichromatic protein detection is demonstrated after sodium dodecyl sulfate(SDS)-polyacrylamide gel electrophoresis, carrier ampholyte-mediated isoelectric focusing or two-dimensional gel electrophoresis.