Enzymatic correction and cross-correction of mucopolysaccharidosis type I fibroblasts by adeno-associated virus-mediated transduction of the alpha-L-iduronidase gene

Mucopolysaccharidoses type I gene therapy

Mucopolysaccharidoses type I (MPS I) is an inherited metabolic disease characterized by a malfunction of the α-l-iduronidase (IDUA) enzyme leading to the storage of glycosaminoglycans in the lysosomes. This disease has longtime been studied as a therapeutic target for those studying gene therapy and many studies have been done using various vectors to deliver the IDUA gene for corrective treatment. Many vectors have difficulties with efficacy and insertional mutagenesis concerns including adeno-associated viral (AAV) vectors. Studies of AAV vectors treating MPS I have seemed promising, but recent deaths in gene therapy clinical trials for other inherited diseases using AAV vectors have left questions about their safety. Additionally, the recent modifications to adenoviral vectors leading them to target the vascular endothelium minimizing the risk of hepatotoxicity could lead to them being a viable option for MPS I gene therapy when coupled with gene editing technologies like CRISPR/Cas9.

Pre-clinical Mouse Models of Neurodegenerative Lysosomal Storage Diseases

There are over 50 lysosomal hydrolase deficiencies, many of which cause neurodegeneration, cognitive decline and death. In recent years, a number of broad innovative therapies have been proposed and investigated for lysosomal storage diseases (LSDs), such as enzyme replacement, substrate reduction, pharmacologic chaperones, stem cell transplantation, and various forms of gene therapy. Murine models that accurately reflect the phenotypes observed in human LSDs are critical for the development, assessment and implementation of novel translational therapies. The goal of this review is to summarize the neurodegenerative murine LSD models available that recapitulate human disease, and the pre-clinical studies previously conducted. We also describe some limitations and difficulties in working with mouse models of neurodegenerative LSDs.

Neonatal nonviral gene editing with the CRISPR/Cas9 system improves some cardiovascular, respiratory, and bone disease features of the mucopolysaccharidosis I phenotype in mice

Mucopolysaccharidosis type I (MPS I) is caused by deficiency of alpha-L-iduronidase (IDUA), leading to multisystemic accumulation of glycosaminoglycans (GAG). Untreated MPS I patients may die in the first decades of life, mostly due to cardiovascular and respiratory complications. We previously reported that the treatment of newborn MPS I mice with intravenous administration of lipossomal CRISPR/Cas9 complexes carrying the murine Idua gene aiming at the ROSA26 locus resulted in long-lasting IDUA activity and GAG reduction in various tissues. Following this, the present study reports the effects of gene editing in cardiovascular, respiratory, bone, and neurologic functions in MPS I mice. Bone morphology, specifically the width of zygomatic and femoral bones, showed partial improvement. Although heart valves were still thickened, cardiac mass and aortic elastin breaks were reduced, with normalization of aortic diameter. Pulmonary resistance was normalized, suggesting improvement in respiratory function. In contrast, behavioral abnormalities and neuroinflammation still persisted, suggesting deterioration of the neurological functions. The set of results shows that gene editing performed in newborn animals improved some manifestations of the MPS I disorder in bone, respiratory, and cardiovascular systems. However, further studies will be imperative to find better delivery strategies to reach "hard-to-treat" tissues to ensure better systemic and neurological effects.

Gene editing of MPS I human fibroblasts by co-delivery of a CRISPR/Cas9 plasmid and a donor oligonucleotide using nanoemulsions as nonviral carriers

Mucopolysaccharidosis type I (MPS I) is an inherited disease caused by the deficiency of alpha-L-iduronidase (IDUA). This study shows the use of nanoemulsions co-complexed with the plasmid of CRISPR/Cas9 system and a donor oligonucleotide aiming at MPS I gene editing in vitro. Nanoemulsions composed of MCT, DOPE, DOTAP, DSPE-PEG, and water were prepared by high-pressure homogenization. The DNA was complexed by adsorption (NA) or encapsulation (NE) of preformed DNA/DOTAP complexes with nanoemulsions at +4/-1 charge ratio. The incubation in pure DMEM or supplemented with serum showed that the complexation with DNA was stable after 1 h of incubation, but the complexes tended to release the adsorbed DNA after 24 h of incubation, while the encapsulated DNA remained complexed in the oil core of the nanoemulsions even 48 h after incubation with DMEM. The treatment of MPS I patient's fibroblasts homozygous for the p.Trp402^∗ mutation led to a significant increase in IDUA activity at 2, 15, and 30 days when compared to MPS I untreated fibroblasts. Flow cytometry and confocal microscopy demonstrated that there was a reduction in the area of lysosomes to values similar to normal, an indicator of correction of the cellular phenotype. These results show that the nanoemulsions co-complexed with the CRISPR/Cas9 system and a donor oligonucleotide could effectively transfect MPS I p.Trp402^∗ patient's fibroblasts, as well as enable the production of IDUA, and represent a potential new treatment option for MPS I.

Comparison of Endovascular and Intraventricular Gene Therapy With Adeno-Associated Virus-α-L-Iduronidase for Hurler Disease

BACKGROUND

Hurler disease (mucopolysaccharidosis type I [MPS-I]) is an inherited metabolic disorder characterized by deficiency of the lysosomal enzyme α-L-iduronidase (IDUA). Currently, the only therapies for MPS-I, enzyme replacement and hematopoietic stem cell transplantation, are generally ineffective for central nervous system manifestations.

OBJECTIVE

To test whether brain-targeted gene therapy with recombinant adeno-associated virus (rAAV5)-IDUA vectors in an MPS-I transgenic mouse model would reverse the pathological hallmarks.

METHODS

Gene therapy approaches were compared using intraventricular or endovascular delivery with a marker (rAAV5-green fluorescent protein) or therapeutic (rAAV5-IDUA) vector. To improve the efficiency of brain delivery, we tested different applications of hyperosmolar mannitol to disrupt the blood-brain barrier or ependymal-brain interface.

RESULTS

Intraventricular delivery of 1 × 10 viral particles of rAAV5-IDUA with systemic 5 g/kg mannitol co-administration resulted in IDUA expression throughout the brain, with global enzyme activity >200% of the baseline level in age-matched, wild-type mice. Endovascular delivery of 1 × 10 viral particles of rAAV5-IDUA to the carotid artery with 29.1% mannitol blood-brain barrier disruption resulted in mainly ipsilateral brain IDUA expression and ipsilateral brain enzyme activity 42% of that in wild-type mice. Quantitative assays for glycosaminoglycans showed a significant decrease in both hemispheres after intraventricular delivery and in the ipsilateral hemisphere after endovascular delivery compared with untreated MPS-I mice. Immunohistochemistry for ganglioside GM3, another disease marker, showed reversal of neuronal inclusions in areas with IDUA co-expression in both delivery methods.

CONCLUSION

Physiologically relevant biochemical correction is possible with neurosurgical or endovascular gene therapy approaches for MPS-I. Intraventricular or endovascular delivery of rAAV5-IDUA was effective in reversing brain pathology, but in the latter method, effects were limited to the ipsilateral hemisphere.

Sustained correction of motoneuron histopathology following intramuscular delivery of AAV in pompe mice

Pompe disease is an autosomal recessive disorder caused by mutations in the acid-α glucosidase (GAA) gene. Lingual dysfunction is prominent but does not respond to conventional enzyme replacement therapy (ERT). Using Pompe (Gaa(-/-)) mice, we tested the hypothesis that intralingual delivery of viral vectors encoding GAA results in GAA expression and glycogen clearance in both tongue myofibers and hypoglossal (XII) motoneurons. An intralingual injection of an adeno-associated virus (AAV) vector encoding GAA (serotypes 1 or 9; 1 × 10(11) vector genomes, CMV promoter) was performed in 2-month-old Gaa(-/-) mice, and tissues were harvested 4 months later. Both serotypes robustly transduced tongue myofibers with histological confirmation of GAA expression (immunochemistry) and glycogen clearance (Period acid-Schiff stain). Both vectors also led to medullary transgene expression. GAA-positive motoneurons did not show the histopathologic features which are typical in Pompe disease and animal models. Intralingual injection with the AAV9 vector resulted in approximately threefold more GAA-positive XII motoneurons (P < 0.02 versus AAV1); the AAV9 group also gained more body weight over the course of the study (P < 0.05 versus AAV1 and sham). We conclude that intralingual injection of AAV1 or AAV9 drives persistent GAA expression in tongue myofibers and motoneurons, but AAV9 may more effectively target motoneurons.

Design and optimization of lentiviral vectors for transfer of GALC expression in Twitcher brain

BACKGROUND

Demyelination in globoid cell leukodystrophy (GLD) is due to a deficiency of galactocerebrosidase (GALC) activity. Up to now, in vivo brain viral gene transfer of GALC showed modest impact on disease development in Twitcher mice, an animal model for GLD. Lentiviral vectors, which are highly efficient to transfer the expression of therapeutic genes in neurons and glial cells, have not been evaluated for direct cerebral therapy in GLD mice.

METHODS

Lentiviral vectors containing the untagged cDNA or the hemagglutinin (HA)-tagged cDNA for the full-length mouse GALC sequence were generated and validated in vitro. In vivo therapeutic efficacy of these vectors was evaluated by histology, biochemistry and electrophysiology after transduction of ependymal or subependymal layers in young Twitcher pups.

RESULTS

Both GALC lentiviral vectors transduced neurons, oligodendrocytes and astrocytes with efficiencies above 75% and conferred high levels of enzyme activity. GALC accumulated in lysosomes of transduced cells and was also secreted to the extracellular medium. Conditioned GALC medium was able to correct the enzyme deficiency when added to non-transduced Twitcher glial cultures. Mice that received intraventricular injections of GALC vector showed accumulation of GALC in ependymal cells but no diffusion of the enzyme from the ependymal ventricular tree into the cerebral parenchyma. Significant expression of GALC-HA was detected in neuroglioblasts when GALC-HA lentiviral vectors were injected in the subventricular zone of Twitcher mice. Life span and motor conduction in both groups of treated Twitcher mice were not significantly ameliorated.

CONCLUSIONS

Lentiviral vectors showed to be efficient for reconstitution of the GALC expression in Twitcher neural cells. GALC was able to accumulate in lysosomes as well as to enter the secretory pathway of lysosomal enzymes, two fundamental aspects for gene therapy of lysosomal storage diseases. Our in vivo results, while showing the capacity of lentiviral vectors to transfer expression of therapeutic GALC in the Twitcher brain, did not limit progression of disease in Twitchers and highlight the need to evaluate other routes of administration.

Axons mediate the distribution of arylsulfatase A within the mouse hippocampus upon gene delivery

Axonal transport of the lysosomal enzyme arylsulfatase A (ARSA) may be an additional mechanism of enzyme distribution after in vivo brain gene transfer in an animal model of metachromatic leukodystrophy (MLD). Direct molecular demonstration of the movement of this lysosomal enzyme within axonal networks was missing. We generated lentiviral vectors carrying the ARSA cDNA tagged with hemagglutinin or the green fluorescent protein and examined the subcellular localization and anatomical distribution of the tagged enzymes within the MLD hippocampus after in vivo lentiviral gene transfer. The use of tagged ARSA allowed direct real-time observation and tracking of axon-dendritic transport of the enzyme after lentiviral gene therapy. Tagged ARSA was expressed in transduced pyramidal, granule, and hilar neurons within the lentiviral-injected side and was robustly contained in vesicles within ipsilateral axon-dendritic processes as well as in vesicles associated with contralateral axons and commissural axons of the ventral hippocampal commissure. Axonal transport of tagged ARSA led to the correction of hippocampal defects in long-term treated MLD mice, which was accompanied by enzyme uptake in nontransduced contralateral neurons, enzyme accumulation within the lysosomal compartment, and clearance of sulfatide storage deposits in this region of the MLD brain. These results contribute to the understanding of the mechanisms of distribution of lysosomal enzymes within the mammalian brain after direct gene therapy, demonstrating the use of neural processes for enzyme transport.

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.

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.

In vitro gene therapy of mucopolysaccharidosis type I by lentiviral vectors

Mucopolysaccharidosis type I (MPS I) results from a deficiency in the enzyme alpha-L-iduronidase (IDUA), and is characterized by skeletal abnormalities, hepatosplenomegaly and neurological dysfunction. In this study, we used a late generation lentiviral vector to evaluate the utility of this vector system for the transfer and expression of the human IDUA cDNA in MPS I fibroblasts. We observed that the level of enzyme expression in transduced cells was 1.5-fold the level found in normal cells; the expression persisted for at least two months. In addition, transduced MPS I fibroblasts were capable of clearing intracellular radiolabeled glycosaminoglycan (GAG). Pulse-chase experiments on transduced fibroblasts showed that the recombinant enzyme was synthesized as a 76-kDa precursor form and processed to a 66-kDa mature form; it was released from transduced cells and was endocytosed into a second population of untreated MPS I fibroblasts via a mannose 6-phosphate receptor. These results suggest that the lentiviral vector may be used for the delivery and expression of the IDUA gene to cells in vivo for treatment of MPS I.

Urinary glycosaminoglycan excretion quantified by an automated semimicro method in specimens conveniently transported from around the globe

Current and future treatments for children with mucopolysaccharidosis (MPS) diseases require early, presymptomatic diagnosis, yet existing diagnostic methods to quantitate urinary glycosaminoglycan (GAG) are labor-intensive, and thus not applicable for newborn screening. Direct and rapid quantification of GAG excretion with 1,9-dimethylmethylene blue (DMB) is applicable to small volumes of urine collected, dried, and mailed on a paper matrix (MPS Test). To determine if this assay could be automated, a robotic instrument was programmed to accomplish the procedure; the pilot method simultaneously determined GAG and creatinine concentrations in 10 patient specimens/run. Each analyte is measured in 4 dilutions, thus increasing the operating range to cover a broad spectrum of normal and pathologic levels. Samples and reagents are mixed in a 96-well tray format in approximately 20 min, and densitometric measurements are recorded in less than 60 s. Optical density measurements are electronically transmitted to a desktop computer to select optimal dilutions, identify values above or below the level of reliability, make calculations, and print reports. This automated method was applied to 255 specimens from 101 subjects representing each of the MPS diseases--specifically, types I (n = 126), II (n = 47), III (n = 48), IV (n = 17), VI (n = 14) and VII (n = 3). This method discriminated pathologic elevations of GAG excretion of MPS patients particularly when multiple specimens were available. Patients with non-MPS lysosomal diseases had normal GAG excretion, except for a patient with fucosidosis who had markedly elevated levels. Automation of the direct DMB method provides the key technology necessary for newborn screening for MPS diseases.

In vivo transduction of cerebellar Purkinje cells using adeno-associated virus vectors

We investigated whether adenovirus or adeno-associated virus vectors can transduce cerebellar Purkinje cells (PCs) in vivo. Mice were injected in the deep cerebellar nuclei (DCN) with lacZ-transducing adenovirus (Ad.RSV-betagal) or a recombinant AAV serotype 2 (rAAV2) vector (vTR-CMVbeta) mixed with wild-type adenovirus type 5 (Ad5). One week later, Ad.RSV-betagal transduced cells were found throughout the cerebellar white matter in a dose-dependent manner, but few transduced PCs were evident. In contrast, vTR-CMVbeta with Ad5 transduced several hundred PCs throughout the injected hemisphere. Using an rAAV2 vector transducing a CMV-regulated green fluorescent protein gene, we again found PC transduction, but only with Ad5 coinjection. To assess the effect of injection site and to determine whether the apparent requirement for Ad5 coinfection is observed with other promoters, a beta-actin-regulated vector was injected with or without Ad5 to DCN or cerebellar cortical sites. Thousands of transduced PCs were observed under each condition. Cortical injection yielded greater numbers of transduced cells. Injection of rAAV2 without Ad5 led to greater specificity for PC transduction. We conclude that injection of rAAV2 vectors into the cerebellum is an effective means for transferring genes into substantial numbers of Purkinje cells in vivo.