Sex Difference Leads to Differential Gene Expression Patterns and Therapeutic Efficacy in Mucopolysaccharidosis IVA Murine Model Receiving AAV8 Gene Therapy

Intrathecal or intravenous AAV9-IDUA/RGX-111 at minimal effective dose prevents cardiac, skeletal and neurologic manifestations of murine MPS I

Mucopolysaccharidosis type I (MPS I) is a rare metabolic disorder caused by deficiency of α-L-iduronidase (IDUA), resulting in glycosaminoglycan (GAG) accumulation and multisystemic disease. Current treatments include hematopoietic stem cell transplantation and enzyme replacement therapy, but these do not address all manifestations of the disease. We infused MPS I mice with an adeno-associated virus 9 (AAV9)-IDUA vector (RGX-111) at doses from 107 to 1010 vector genomes (vg) via intrathecal (IT), intravenous (IV), and intrathecal+intravenous (IT+IV) routes of administration. In mice administered doses ≤109 vg IT or ≤108 vg IV, there was no therapeutic benefit, while in mice administered 109 vg IV, there was a variable increase in IDUA activity with inconclusive neurocognitive and cardiac assessments. However, at the 1010 vg dose, we observed substantial metabolic correction, with restored IDUA levels and normalized tissue GAGs for all treatment groups. Aortic insufficiency was mostly normalized, neurologic deficit was prevented, and microcomputed tomography (micro-CT) analysis showed normalization of skeletal parameters. Histologic analysis showed minimal GAG storage and lysosomal pathology. We thus report a minimal effective dose of 1010 vg (5 × 1011 per kg) RGX-111 for IV and IT routes of administration in MPS I mice, which prevented neurocognitive deficit, cardiac insufficiency, and skeletal manifestations, as a model for genetic therapy of human MPS I.

Adeno-Associated Virus Gene Transfer Ameliorates Progression of Skeletal Lesions in Mucopolysaccharidosis IVA Mice

Mucopolysaccharidosis type IVA (MPS IVA) is an autosomal congenital metabolic lysosomal disease caused by a deficiency of the N-acetyl-galactosamine-6-sulfate sulfatase (GALNS) gene, leading to severe skeletal dysplasia. The available therapeutics for patients with MPS IVA, enzyme replacement therapy and hematopoietic stem cell transplantation, revealed limitations in the impact of skeletal lesions. Our previous study, a significant leap forward in MPS IVA research, showed that liver-targeted adeno-associated virus (AAV) gene transfer of human GALNS (hGALNS) restored GALNS enzymatic activity in blood and multiple tissues and partially improved the aberrant accumulation of storage materials. This promising approach was further validated in our current study, where we delivered AAV8 vectors expressing hGALNS, under the control of a liver-specific or ubiquitous promoter, into MPS IVA murine disease models. The results were highly encouraging, with both AAV8 vectors leading to supraphysiological enzymatic activity in plasma and improved cytoplasmic vacuolization of chondrocytes in bone lesions of MPS IVA mice. Notably, the ubiquitous promoter constructs, a potential game-changer, resulted in significantly greater enzyme activity levels in bone and improved pathological findings of cartilage lesions in these mice than in a liver-specific one during the 12-week monitoring period, reinforcing the positive outcomes of our research in MPS IVA treatment.

AAV-mediated co-expression of an immunogenic transgene plus PD-L1 enables sustained expression through immunological evasion

Adeno-associated virus (AAV) vectors can mediate long-term expression of immunogenic transgenes in vivo through transduction of tolerogenic cells in the liver. Tissue-targeted AAV vectors allow transduction of non-hepatic cells, but this necessitates development of strategies to minimize transgene immunogenicity. Here, we first validated that AAV capsids with tissue-specific tropism and transgene promoters enabled expression of the immunogenic protein, firefly luciferase, in liver, muscle, or adipose tissue. Cellular immunity was detectable in animals where luciferase was expressed in muscle or adipose, but not liver tissue. With the objective of enhancing tolerance of transduced non-hepatic cells, AAV vectors were engineered to co-express luciferase plus the immune checkpoint protein, PD-L1. In animals where transduced cells expressed luciferase but not PD-L1, there was incremental depletion of transduced cells over time. By contrast, the bioluminescent signal increased incrementally over the study, and was significantly greater, in the muscle and adipose tissue of animals where PD-L1 was co-expressed with luciferase. Our data demonstrate that PD-L1 co-expression facilitates persistent, tissue-targeted expression of immunogenic transgenes without transducing tolerogenic hepatic cells. Our strategy of PD-L1 co-expression may provide a versatile platform for sustained expression of immunogenic transgenes in gene and cell therapies.

Comprehensive evaluation of pathogenic protein accumulation in fibroblasts from all subtypes of Sanfilippo disease patients

Sanfilippo disease is a lysosomal storage disorder from the group of mucopolysaccharidoses (MPS), characterized by storage of glycosaminoglycans (GAGs); thus, it is also called MPS type III. The syndrome is divided into 4 subtypes (MPS III A, B, C and D). Despite the storage of the same GAG, heparan sulfate (HS), the course of these subtypes can vary considerably. Here, we comprehensively evaluated the levels of protein aggregates (APP, β-amyloid, p-tau, α-synuclein, TDP43) in fibroblasts derived from patients with all MPS III subtypes, and tested whether lowering GAG levels results in a decrease in the levels of the investigated proteins and the number of aggregates they form. Elevated levels of APP, β-amyloid, tau, and TDP43 proteins were evident in all MPS III subtypes, and elevated levels of p-tau and α-synuclein were demonstrated in all subtypes except MPS IIIC. These findings were confirmed in the neural tissue of MPS IIIB mice. Fluorescence microscopy studies also indicated a high number of protein aggregates formed by β-amyloid and tau in all cell lines tested, and a high number of aggregates of p-tau, TDP43, and α-synuclein in all lines except MPS IIIC. Reduction of GAG levels by genistein led to the decrease of levels of all tested proteins and their aggregates except α-synuclein, indicating a relationship between GAG levels and those of some protein aggregates. This work describes for the first time the problem of deposited protein aggregates in all subtypes of Sanfilippo disease and suggests that GAGs are partly responsible for the formation of protein aggregates.

A Comprehensive Atlas of AAV Tropism in the Mouse

Gene therapy with Adeno-Associated Viral (AAV) vectors requires knowledge of their tropism within the body. Here we analyze the tropism of ten naturally occurring AAV serotypes (AAV3B, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, AAVrh8, AAVrh10 and AAVrh74) following systemic delivery into male and female mice. A transgene expressing ZsGreen and Cre recombinase was used to identify transduction in a cell-dependent manner based on fluorescence. Cre-driven activation of tdTomato fluorescence offered superior sensitivity for transduced cells. All serotypes except AAV3B and AAV4 had high liver tropism. Fluorescence activation revealed transduction of unexpected tissues, including adrenals, testes and ovaries. Rare transduced cells within tissues were also readily visualized. Biodistribution of AAV genomes correlated with fluorescence, except in immune tissues. AAV4 was found to have a pan-endothelial tropism while also targeting pancreatic beta cells. This public resource enables selection of the best AAV serotypes for basic science and preclinical applications in mice.

Recombinant Adeno-Associated Virus Vectors for Gene Therapy of the Central Nervous System: Delivery Routes and Clinical Aspects

The Central Nervous System (CNS) is vulnerable to a range of diseases, including neurodegenerative and oncological conditions, which present significant treatment challenges. The blood-brain barrier (BBB) restricts molecule penetration, complicating the achievement of therapeutic concentrations in the CNS following systemic administration. Gene therapy using recombinant adeno-associated virus (rAAV) vectors emerges as a promising strategy for treating CNS diseases, demonstrated by the registration of six gene therapy products in the past six years and 87 ongoing clinical trials. This review explores the implementation of rAAV vectors in CNS disease treatment, emphasizing AAV biology and vector engineering. Various administration methods-such as intravenous, intrathecal, and intraparenchymal routes-and experimental approaches like intranasal and intramuscular administration are evaluated, discussing their advantages and limitations in different CNS contexts. Additionally, the review underscores the importance of optimizing therapeutic efficacy through the pharmacokinetics (PK) and pharmacodynamics (PD) of rAAV vectors. A comprehensive analysis of clinical trials reveals successes and challenges, including barriers to commercialization. This review provides insights into therapeutic strategies using rAAV vectors in neurological diseases and identifies areas requiring further research, particularly in optimizing rAAV PK/PD.

Molecular therapy and nucleic acid adeno-associated virus-based gene therapy delivering combinations of two growth-associated genes to MPS IVA mice

Mucopolysaccharidosis type IVA (MPS IVA) is caused by a deficiency of the galactosamine (N-acetyl)-6-sulfatase (GALNS) enzyme responsible for the degradation of specific glycosaminoglycans (GAGs). The progressive accumulation of GAGs leads to various skeletal abnormalities (short stature, hypoplasia, tracheal obstruction) and several symptoms in other organs. To date, no treatment is effective for patients with bone abnormalities. To improve bone pathology, we propose a novel combination treatment with the adeno-associated virus (AAV) vectors expressing GALNS enzyme and a natriuretic peptide C (CNP; NPPC gene) as a growth-promoting agent for MPS IVA. In this study, an MPS IVA mouse model was treated with an AAV vector expressing GALNS combined with another AAV vector expressing NPPC gene, followed for 12 weeks. After the combination therapy, bone growth in mice was induced with increased enzyme activity in tissues (bone, liver, heart, lung) and plasma. Moreover, there were significant changes in bone morphology in CNP-treated mice with increased CNP activity in plasma. Delivering combinations of CNP and GALNS gene therapies enhanced bone growth in MPS IVA mice more than in GALNS gene therapy alone. Enzyme expression therapy alone fails to reach the bone growth region; our results indicate that combining it with CNP offers a potential alternative.

Comparative dose effectiveness of intravenous and intrathecal AAV9.CB7.hIDS, RGX-121, in mucopolysaccharidosis type II mice

Mucopolysaccharidosis type II (MPS II) is an X-linked recessive lysosomal disease caused by iduronate-2-sulfatase (IDS) deficiency, leading to accumulation of glycosaminoglycans (GAGs) and the emergence of progressive disease. Enzyme replacement therapy is the only currently approved treatment, but it leaves neurological disease unaddressed. Cerebrospinal fluid (CSF)-directed administration of AAV9.CB7.hIDS (RGX-121) is an alternative treatment strategy, but it is unknown if this approach will affect both neurologic and systemic manifestations. We compared the effectiveness of intrathecal (i.t.) and intravenous (i.v.) routes of administration (ROAs) at a range of vector doses in a mouse model of MPS II. While lower doses were completely ineffective, a total dose of 1 × 109 gc resulted in appreciable IDS activity levels in plasma but not tissues. Total doses of 1 × 1010 and 1 × 1011 gc by either ROA resulted in supraphysiological plasma IDS activity, substantial IDS activity levels and GAG reduction in nearly all tissues, and normalized zygomatic arch diameter. In the brain, a dose of 1 × 1011 gc i.t. achieved the highest IDS activity levels and the greatest reduction in GAG content, and it prevented neurocognitive deficiency. We conclude that a dose of 1 × 1010 gc normalized metabolic and skeletal outcomes, while neurologic improvement required a dose of 1 × 1011 gc, thereby suggesting the prospect of a similar direct benefit in humans.

Infusion reactions to adeno-associated virus (AAV)-based gene therapy: Mechanisms, diagnostics, treatment and review of the literature

The use of adeno-associated virus (AAV) vectors in gene therapy has demonstrated great potential in treating genetic disorders. However, infusion-associated reactions (IARs) pose a significant challenge to the safety and efficacy of AAV-based gene therapy. This review provides a comprehensive summary of the current understanding of IARs to AAV therapy, including their underlying mechanisms, clinical presentation, and treatment options. Toll-like receptor activation and subsequent production of pro-inflammatory cytokines are associated with IARs, stimulating neutralizing antibodies (Nabs) and T-cell responses that interfere with gene therapy. Risk factors for IARs include high titers of pre-existing Nabs, previous exposure to AAV, and specific comorbidities. Clinical presentation ranges from mild flu-like symptoms to severe anaphylaxis and can occur during or after AAV administration. There are no established guidelines for pre- and postadministration tests for AAV therapies, and routine laboratory requests are not standardized. Treatment options include corticosteroids, plasmapheresis, and supportive medications such as antihistamines and acetaminophen, but there is no consensus on the route of administration, dosage, and duration. This review highlights the inadequacy of current treatment regimens for IARs and the need for further research to improve the safety and efficacy of AAV-based gene therapy.