Dexamethasone Transiently Enhances Transgene Expression in the Liver When Administered at Late-Phase Post Long-Term Adeno-Associated Virus Transduction

Gene Therapy in the Light of Lifestyle Diseases: Budesonide, Acetaminophen and Simvastatin Modulates rAAV Transduction Efficiency

Recombinant AAV (rAAV) vectors are increasingly favored for gene therapy due to their useful features of vectorology, such as transfection of dividing and nondividing cells, the presence of tissue-specific serotypes, and biosafety considerations. This study investigates the impact of commonly used therapeutic drugs-acetaminophen, budesonide, and simvastatin-on rAAV transduction efficiency in HEK-293 cells. Cells were transduced with an AAV mosaic vector under the control of a cytomegalovirus (CMV) promoter encoding green fluorescent protein (GFP). Transduction efficiency was assessed by qPCR and fluorescent microscopy. Analysis of functional interactions between genes potentially involved in rAAV transduction in drug-exposed cells was also performed. This study showed a clear effect of drugs on rAAV transmission. Notably, acetaminophen enhanced transduction efficiency by 9-fold, while budesonide and simvastatin showed 2-fold and 3-fold increases, respectively. The gene analysis illustrates the possible involvement of genes related to cell membranes in the potentiation of rAAV transduction induced by the drugs under investigation. Attention should be paid to S100A8, which is a common drug-modified gene for drugs showing anti-inflammatory effects (budesonide and simvastatin), demonstrating an interaction with the gene encoding the receptor for AAV (HGFR). This study underscores the significance of assessing rAAV pharmacokinetics/pharmacodynamics (PKs/PDs) and drug-gene therapy interactions in optimizing gene therapy protocols.

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.

An investigation of the immune epitopes of adeno-associated virus capsid-derived peptides among hemophilia patients

Adeno-associated virus (AAV) is an optimal gene vector for monogenic disorders. However, neutralizing antibodies (Nabs) against AAV hinder its widespread application in gene therapy. In this study, we biosynthesized peptides recognized by the binding antibodies (Babs) from the sera containing high Nab titers against AAV2. We established four immunological methods to detect immune epitopes of the AAV2-derived peptides, including a Bab assay, Nab assay, B cell receptor (BCR) detecting assay, and immunoglobin-producing B cell enzyme-linked immunosorbent spot (B cell ELISpot) assay. Correlations among the epitopes determined by these four methods were analyzed using the serum samples and peripheral blood mononuclear cells (PBMC) from 89 patients with hemophilia A/B. As decoys, the peptides' ability to block the Nab of AAV2 particles was assessed using AAV transduction models both in vitro and in vivo. Overall, we provide insights into AAV2-capsid-derived peptide immune epitopes, involving the Nab, Bab, BCR, and B cell ELISpot assays, offering alternative immunological evaluation approaches and strategies to overcome Nab barriers in AAV-mediated gene therapy.

Enhanced transgene expression from single-stranded AAV vectors in human cells in vitro and in murine hepatocytes in vivo

We identified that distal 10 nucleotides in the D-sequence in AAV2 inverted terminal repeat (ITR) share partial sequence homology to 1/2 binding site of glucocorticoid receptor-binding element (GRE). Here, we describe that (1) purified GR binds to AAV2 D-sequence, and the D-sequence competes with GR binding to its cognate binding site; (2) dexamethasone-mediated activation of GR pathway significantly increases the transduction efficiency of AAV2 vectors in human cells; (3) human osteosarcoma cells, U2OS, which lack expression of GR, are poorly transduced by AAV2 vectors, but stable transfection with a GR expression plasmid restores vector-mediated transgene expression; (4) replacement of the distal 10 nucleotides in the D-sequence of the AAV2 ITR with a full-length GRE consensus sequence significantly enhances transgene expression in human cells in vitro and in murine hepatocytes in vivo; and (5) none of the ITRs in AAV1, AAV3, AAV4, AAV5, and AAV6 genomes contains the GRE 1/2 binding site, and insertion of a full-length GRE consensus sequence in the AAV6-ITR also significantly enhances transgene expression from AAV6 vectors, both in vitro and in vivo. These novel vectors, termed generation Y AAV vectors, which are serotype, transgene, or promoter agnostic, should be useful in human gene therapy.

Adeno-associated virus as a delivery vector for gene therapy of human diseases

Adeno-associated virus (AAV) has emerged as a pivotal delivery tool in clinical gene therapy owing to its minimal pathogenicity and ability to establish long-term gene expression in different tissues. Recombinant AAV (rAAV) has been engineered for enhanced specificity and developed as a tool for treating various diseases. However, as rAAV is being more widely used as a therapy, the increased demand has created challenges for the existing manufacturing methods. Seven rAAV-based gene therapy products have received regulatory approval, but there continue to be concerns about safely using high-dose viral therapies in humans, including immune responses and adverse effects such as genotoxicity, hepatotoxicity, thrombotic microangiopathy, and neurotoxicity. In this review, we explore AAV biology with an emphasis on current vector engineering strategies and manufacturing technologies. We discuss how rAAVs are being employed in ongoing clinical trials for ocular, neurological, metabolic, hematological, neuromuscular, and cardiovascular diseases as well as cancers. We outline immune responses triggered by rAAV, address associated side effects, and discuss strategies to mitigate these reactions. We hope that discussing recent advancements and current challenges in the field will be a helpful guide for researchers and clinicians navigating the ever-evolving landscape of rAAV-based gene therapy.

Immunosuppression reduces rAAV2.5T neutralizing antibodies that limit efficacy following repeat dosing to ferret lungs

The efficacy of redosing the recombinant adeno-associated virus (rAAV) vector rAAV2.5T to ferret lung is limited by AAV neutralizing antibody (NAb) responses. While immunosuppression strategies have allowed for systemic rAAV repeat dosing, their utility for rAAV lung-directed gene therapy is largely unexplored. To this end, we evaluated two immunosuppression (IS) strategies to improve repeat dosing of rAAV2.5T to ferret lungs: (1) a combination of three IS drugs (Tri-IS) with broad coverage against cellular and humoral responses (methylprednisolone [MP], azathioprine, and cyclosporine) and (2) MP alone, which is typically used in systemic rAAV applications. Repeat dosing utilized AAV2.5T-SP183-fCFTRΔR (recombinant ferret CFTR transgene), followed 28 days later by AAV2.5T-SP183-gLuc (for quantification of transgene expression). Both the Tri-IS and MP strategies significantly improved transgene expression following repeat dosing and reduced AAV2.5T NAb responses in the bronchioalveolar lavage fluid (BALF) and plasma, while AAV2.5T binding antibody subtypes and cellular immune responses by ELISpot were largely unchanged by IS. One exception was the reduction in plasma AAV2.5T binding immunoglobulin G (IgG) in both IS groups. Only the Tri-IS strategy significantly suppressed splenocyte expression of IFNA (interferon α [IFN-α]) and IL4. Our studies suggest that IS strategies may be useful in clinical application of rAAV targeting lung genetic diseases such as cystic fibrosis.

Ex Vivo Gene Delivery to Porcine Cardiac Allografts Using a Myocardial-Enhanced Adeno-Associated Viral Vector

Transplantation, the gold standard intervention for organ failure, is a clinical field that is ripe for applications of gene therapy. One of the major challenges in applying gene therapy to this field is the need for a method that achieves consistent and robust gene delivery to allografts. Normothermic ex vivo perfusion is a growing organ preservation method and a device for cardiac preservation was recently approved by the Food and Drug Administration (FDA) (Organ Care System, OCS™; TransMedics, Inc., Andover, MA); this device maintains donor hearts in a near physiologic state while they are transported from the donor to the recipient. This study describes the administration of recombinant adeno-associated viral vectors (rAAVs) during ex vivo normothermic perfusion for the delivery of transgenes to porcine cardiac allografts. We utilized a myocardial-enhanced AAV3b variant, SASTG, assessing its transduction efficiency in the OCS perfusate relative to other AAV serotypes. We describe the use of normothermic ex vivo perfusion to deliver SASTG carrying the Firefly Luciferase transgene to porcine donor hearts in four heterotopic transplant procedures. Durable and dose-dependent transgene expression was achieved in the allografts in 30 days, with no evidence of off-target transgene expression. This study demonstrates the feasibility and efficiency of delivering genes to a large animal allograft utilizing AAV vectors during ex vivo perfusion. These findings support the idea of gene therapy interventions to enhance transplantation outcomes.