Adeno-associated Virus Serotype Research Articles

Activation of AMPKα2 attenuated doxorubicin-induced cardiotoxicity via inhibiting lipid peroxidation associated ferroptosis

Ferroptosis has been suggested to involve in doxorubicin (DOX)-induced cardiotoxicity. However, the underlying mechanisms and regulatory targets of cardiomyocyte ferroptosis remains to be understood. This study demonstrated that the up-regulation of ferroptosis associated proteins genes were accompanied with the down-regulation of AMPKα2 phosphorylation in DOX treated mouse heart or neonatal rat cardiomyocytes (NRCMs). AMPKα2 knockout (AMPKα2−/−) significantly exacerbated mouse cardiac dysfunction, increased mortality, promoting ferroptosis associated mitochondrial injuries, enhanced ferroptosis associated proteins and genes expression, and lead to accumulation of lactate dehydrogenase (LDH) and malondialdehyde (MDA) in mouse serum and hearts respectively. Ferrostatin-1 administration markedly improved cardiac function, decreased mortality, inhibited mitochondrial injuries and ferroptosis associated proteins and genes expression, and depressed accumulation of LDH and MDA in DOX treated AMPKα2−/− mouse. Moreover, Adeno-associated virus serotype 9 AMPKα2 (AAV9-AMPKα2) or AICAR treatment mediated AMPKα2 activation could significantly improve cardiac function and depress ferroptosis in mouse. AMPKα2 activation or silence could also inhibit or promote ferroptosis associated injuries in DOX treated NRCMs respecitively. Mechanistically, AMPKα2/ACC mediated lipid metabolism has been suggested to involve in regulating DOX-treatment induced ferroptosis other than mTORC1 or autophagy dependent pathway. The metabolomics analysis exhibited that AMPKα2−/− significantly enhanced accumulation of polyunsaturated fatty acids (PFAs), oxidized lipid, and phosphatidylethanolamine (PE). Finally, this study also demonstrated that metformin (MET) treatment could inhibit ferroptosis and improve cardiac function via activating AMPKα2 phosphorylation. The metabolomics analysis exhibited that MET treatment significantly depressed PFAs accumulation in DOX treated mouse hearts. Collectively, this study suggested that AMPKα2 activation might protect against anthracycline chemotherapeutic drugs mediated cardiotoxicity via inhibiting ferroptosis.

Analysis of Adeno-Associated Virus Serotype 8 (AAV8)-antibody complexes using epitope mapping by molecular imprinting leads to the identification of Fab peptides that potentially evade AAV8 neutralisation

Gene therapy is a promising approach for treating genetic disorders by delivering therapeutic genes to replace or correct malfunctioning genes. However, the introduced gene therapy vector can trigger an immune response, leading to reduced efficacy and potential harm to the patient. To improve the efficiency and safety of gene therapy, preventing the immune response to the vector is crucial. This can be achieved through the use of immunosuppressive drugs, vector engineering to evade the immune system, or delivery methods that bypass the immune system altogether. By reducing the immune response, gene therapy can deliver therapeutic genes more effectively and potentially cure genetic diseases. In this study, a novel molecular imprinting technique, combined with mass-spectrometry and bioinformatics, was used to identify four antigen-binding fragments (Fab) sequences of Adeno-Associated Virus (AAV) - neutralising antibodies capable of binding to AAV. The identified Fab peptides were shown to prevent AAV8's binding to antibodies, demonstrating their potential to improve gene therapy efficiency by preventing the immune response.

Gene therapy ameliorates spontaneous seizures associated with cortical neuron loss in a Cln2R207X mouse model.

Although a disease-modifying therapy for classic late infantile neuronal ceroid lipofuscinosis (CLN2 disease) exists, poor understanding of cellular pathophysiology has hampered the development of more effective and persistent therapies. Here, we investigated the nature and progression of neurological and underlying neuropathological changes in Cln2R207X mice, which carry one of the most common pathogenic mutations in human patients but are yet to be fully characterized. Long-term electroencephalography recordings revealed progressive epileptiform abnormalities, including spontaneous seizures, providing a robust, quantifiable, and clinically relevant phenotype. These seizures were accompanied by the loss of multiple cortical neuron populations, including those stained for interneuron markers. Further histological analysis revealed early localized microglial activation months before neuron loss started in the thalamocortical system and spinal cord, which was accompanied by astrogliosis. This pathology was more pronounced and occurred in the cortex before the thalamus or spinal cord and differed markedly from the staging seen in mouse models of other forms of neuronal ceroid lipofuscinosis. Neonatal administration of adeno-associated virus serotype 9-mediated gene therapy ameliorated the seizure and gait phenotypes and prolonged the life span of Cln2R207X mice, attenuating most pathological changes. Our findings highlight the importance of clinically relevant outcome measures for judging preclinical efficacy of therapeutic interventions for CLN2 disease.

Efficient Adeno-associated Virus-mediated Transgenesis in Alveolar Stem Cells and Associated Niches.

Targeted delivery of transgenes to tissue-resident stem cells and related niches offers avenues for interrogating pathways and editing endogenous alleles for therapeutic interventions. Here, we survey multiple adeno-associated virus (AAV) serotypes, administered via intranasal and retroorbital routes in mice, to target lung alveolar stem cell niches. We found that AAV5, AAV4, and AAV8 efficiently and preferentially transduce alveolar type-2 stem cells (AT2s), endothelial cells, and PDGFRA+ fibroblasts, respectively. Notably, some AAVs show different cell tropisms depending on the route of administration. Proof-of-concept experiments reveal the versatility of AAV5-mediated transgenesis for AT2-lineage labeling, clonal cell tracing after cell ablation, and conditional gene inactivation in both postnatal and adult mouse lungs invivo. AAV6, but not AAV5, efficiently transduces both mouse and human AT2s in alveolar organoid cultures. Furthermore, AAV5 and AAV6 can be used to deliver guide RNAs and transgene cassettes for homologous recombination invivo and ex vivo, respectively. Using this system coupled with clonal derivation of AT2 organoids, we demonstrate efficient and simultaneous editing of multiple loci, including targeted insertion of a payload cassette in AT2s. Taken together, our studies highlight the powerful utility of AAVs for interrogating alveolar stem cells and other specific cell types both invivo and ex vivo.

Hepatocyte NLRP3 interacts with PKCε to drive hepatic insulin resistance and steatosis

Hepatic insulin resistance (IR), as a downstream sequela of nonalcoholic fatty liver disease (NAFLD), is strongly associated with liver steatosis. Despite numerous mechanism advancements, the molecular underpinnings and pathogenesis of hepatic IR, especially regarding the pattern recognition receptors in hepatocytes, remain elusive. Here, we identified hepatocyte NLRP3 as a direct and previously-unresolved driver of hepatic IR to promote steatosis response. Under the model of NAFLD, we identified hepatocyte NLRP3 as a crucial inducer of hepatic IR by undertaking multilayer transcriptomic searches and further confirmed that its expression was increased in the liver tissues from NAFLD patients and mouse models (high-fat diet (HFD), leptin-receptor-deficient (db/db) mice), and in palmitic acid (PA)-induced hepatocytes. Loss- or gain-of-function of hepatocyte-specific NLRP3 in HFD-induced mice ameliorated or exacerbated hepatic IR and steatosis, respectively. Mechanistically, NLRP3 directly bound to and promoted protein kinase C epsilon (PKCε) activation to impair insulin signaling and increase liver steatosis, while inhibition of PKCε activation dampened the beneficial effects seen in HFD-induced NLRP3-deficient mice. Moreover, we performed screening and discovered that the transcription factor Yin Yang 1 (YY1) positively controlled NLRP3 expression. In translational potential, adeno-associated virus serotype 8 (AAV8)-mediated NLRP3 knockdown in the liver alleviated hepatic IR and steatosis in db/db mice, and pharmacological inhibition of NLRP3 markedly alleviated diet-induced metabolic disorders. This finding reveals a previously-unexpected regulatory axis from YY1 to PKCε via NLRP3 induction for metabolic diseases and establishes the YY1-NLRP3-PKCε axis as a potential therapeutic target for NAFLD.

Allele-specific gene-editing approach for vision loss restoration in RHO-associated retinitis pigmentosa.

Mutant RHO is the most frequent genetic cause of autosomal dominant retinitis pigmentosa (adRP). Here, we developed an allele-specific gene-editing therapeutic drug to selectively target the human T17M RHO mutant allele while leaving the wild-type RHO allele intact for the first time. We identified a Staphylococcus aureus Cas9 (SaCas9) guide RNA that was highly active and specific to the human T17M RHO allele. In vitro experiments using HEK293T cells and patient-specific induced pluripotent stem cells (iPSCs) demonstrated active nuclease activity and high specificity. Subretinal delivery of a single adeno-associated virus serotype 2/8 packaging SaCas9 and single guide RNA (sgRNA) to the retinas of the RHO humanized mice showed that this therapeutic drug targeted the mutant allele selectively, thereby downregulating the mutant RHO mRNA expression. Administration of this therapeutic drug resulted in a long-term (up to 11 months after treatment) improvement of retinal function and preservation of photoreceptors in the heterozygous mutant humanized mice. Our study demonstrated a dose-dependent therapeutic effect in vivo. Unwanted off-target effects were not observed at the whole-genome sequencing level. Our study provides strong support for the further development of this effective therapeutic drug to treat RHO-T17M-associated adRP, also offers a generalizable framework for developing gene-editing medicine. Furthermore, our success in restoring the vision loss in the suffering RHO humanized mice verifies the feasibility of allele-specific CRISPR/Cas9-based medicines for other autosomal dominant inherited retinal dystrophies.

P.072 Alberta Spinal Muscular Atrophy Newborn Screening (SMA-NBS) – 2022 results

Background: Spinal muscular atrophy (SMA) is a progressive neuromuscular disease caused by biallelic mutations of the survival motor neuron 1 (SMN1) gene. Early diagnosis via newborn screening and presymptomatic treatment are essential to optimize health outcomes for affected individuals. Methods: We developed a multiplex real-time polymerase chain reaction assay using dried blood spot samples for the detection of homozygous deletion of exon 7 of the SMN1 gene. Newborns who were screened positive were seen urgently for clinical evaluations. Copy numbers of SMN1 and SMN2 genes were determined by multiplex ligation-dependent probe amplication for confirmatory testing. Results: From February 28, 2022 to December 31, 2022, 42,450 newborns were screened in Alberta. Four infants had abnormal screen results and were subsequently confirmed to have SMA. No false positive newborns were detected. Three infants received adeno-associated virus serotype 9 (AAV9)-mediated SMN1 gene replacement therapy <31 days of age. One infant received SMN2-splicing modulator treatment due to maternally-transferred AAV9 neutralizing antibodies prior to gene therapy at 3 months of age. Conclusions: The estimated incidence of SMA in Alberta is 9.4 (95% CI: 2.5 – 24.1) per 100,000 live-births. During the first year of the SMA-NBS program, 4 asymptomatic infants received treatment and demonstrated excellent developmental progress to date.

Extracellular vesicles enhance pulmonary transduction of stably associated adeno-associated virus following intratrachealadministration.

Adeno-associated virus (AAV) vector has shown multiple clinical breakthroughs, but its clinical implementation in inhaled gene therapy remains elusive due to difficulty in transducing lung airway cells. We demonstrate here AAV serotype 6 (AAV6) associated with extracellular vesicles (EVs) and secreted from vector-producing HEK-293 cells during vector preparation (EVAAV6) as a safe and highly efficacious gene delivery platform for inhaled gene therapy applications. Specifically, we discovered that EVAAV6 provided markedly enhanced reporter transgene expression in mucus-covered air-liquid interface (ALI) cultures of primary human bronchial and nasal epithelial cells as well as in mouse lung airways compared to standard preparations of AAV6 alone. Of note, AAV6 has been previously shown to outperform other clinically tested AAV serotypes, including those approved by the FDA for treating non-lung diseases, in transducing ALI cultures of primary human airway cells. We provide compelling experimental evidence that the superior performance of EVAAV6 is attributed to the ability of EV to facilitate mucus penetration and cellular entry/transduction of AAV6. The tight and stable linkage between AAV6 and EVs appears essential to exploit the benefits of EVs given that a physical mixture of individually prepared EVs and AAV6 failed to mediate EV-AAV6 interactions or to enhance gene transfer efficacy.

Genetic modulation of the HTR2A gene reduces anxiety-related behavior in mice.

The expanding field of precision gene editing using CRISPR/Cas9 has demonstrated its potential as a transformative technology in the treatment of various diseases. However, whether this genome-editing tool could be used to modify neural circuits in the central nervous system (CNS), which are implicated in complex behavioral traits, remains uncertain. In this study, we demonstrate the feasibility of noninvasive, intranasal delivery of adeno-associated virus serotype 9 (AAV9) vectors containing CRISPR/Cas9 cargo within the CNS resulting in modification of the HTR2A receptor gene. In vitro, exposure to primary mouse cortical neurons to AAV9 vectors targeting the HT2RA gene led to a concentration-dependent decrease in spontaneous electrical activity following multielectrode array (MEA) analysis. In vivo, at 5 weeks postintranasal delivery in mice, analysis of brain samples revealed single base pair deletions and nonsense mutations, leading to an 8.46-fold reduction in mRNA expression and a corresponding 68% decrease in the 5HT-2A receptor staining. Our findings also demonstrate a significant decrease in anxiety-like behavior in treated mice. This study constitutes the first successful demonstration of a noninvasive CRISPR/Cas9 delivery platform, capable of bypassing the blood-brain barrier and enabling modulation of neuronal 5HT-2A receptor pathways. The results of this study targeting the HTR2A gene provide a foundation for the development of innovative therapeutic strategies for a broad range of neurological disorders, including anxiety, depression, attentional deficits, and cognitive dysfunction.

Enrichment of adeno-associated virus serotype 5 full capsids by anion exchange chromatography with dual salt elution gradients.

Adeno-associated virus-based gene therapies have demonstrated substantial therapeutic benefit for the treatment of genetic disorders. In manufacturing processes, viral capsids are produced with and without the encapsidated gene of interest. Capsids devoid of the gene of interest, or "empty" capsids, represent a product-related impurity. As a result, a robust and scalable method to enrich full capsids is crucial to provide patients with as much potentially active product as possible. Anion exchange chromatography has emerged as a highly utilized method for full capsid enrichment across many serotypes due to its ease of use, robustness, and scalability. However, achieving sufficient resolution between the full and empty capsids is not trivial. In this work, anion exchange chromatography was used to achieve empty and full capsid resolution for adeno-associated virus serotype 5. A salt gradient screen of multiple salts with varied valency and Hofmeister series properties was performed to determine optimal peak resolution and aggregate reduction. Dual salt effects were evaluated on the same product and process attributes to identify any synergies with the use of mixed ion gradients. The modified process provided as high as ≥75% AAV5 full capsids (≥3-fold enrichment based on the percent full in the feed stream) with near baseline separation of empty capsids and achieved an overall vector genome step yield of >65%.

Biochemical Correction of GM2 Ganglioside Accumulation in AB-Variant GM2 Gangliosidosis.

GM2 gangliosidosis is a group of genetic disorders that result in the accumulation of GM2 ganglioside (GM2) in brain cells, leading to progressive central nervous system (CNS) atrophy and premature death in patients. AB-variant GM2 gangliosidosis (ABGM2) arises from loss-of-function mutations in the GM2 activator protein (GM2AP), which is essential for the breakdown of GM2 in a key catabolic pathway required for CNS lipid homeostasis. In this study, we show that intrathecal delivery of self-complementary adeno-associated virus serotype-9 (scAAV9) harbouring a functional human GM2A transgene (scAAV9.hGM2A) can prevent GM2 accumulation in in GM2AP-deficient mice (Gm2a-/- mice). Additionally, scAAV9.hGM2A efficiently distributes to all tested regions of the CNS within 14 weeks post-injection and remains detectable for the lifespan of these animals (up to 104 weeks). Remarkably, GM2AP expression from the transgene scales with increasing doses of scAAV9.hGM2A (0.5, 1.0 and 2.0 × 1011 vector genomes (vg) per mouse), and this correlates with dose-dependent correction of GM2 accumulation in the brain. No severe adverse events were observed, and comorbidities in treated mice were comparable to those in disease-free cohorts. Lastly, all doses yielded corrective outcomes. These data indicate that scAAV9.hGM2A treatment is relatively non-toxic and tolerable, and biochemically corrects GM2 accumulation in the CNS-the main cause of morbidity and mortality in patients with ABGM2. Importantly, these results constitute proof-of-principle for treating ABGM2 with scAAV9.hGM2A by means of a single intrathecal administration and establish a foundation for future preclinical research.

Safety and Efficacy of Intravenous and Intrathecal Delivery of AAV9-Mediated ARSA in Minipigs.

Metachromatic leukodystrophy (MLD) is a hereditary neurodegenerative disease characterized by demyelination and motor and cognitive impairments due to deficiencies of the lysosomal enzyme arylsulfatase A (ARSA) or the saposin B activator protein (SapB). Current treatments are limited; however, gene therapy using adeno-associated virus (AAV) vectors for ARSA delivery has shown promising results. The main challenges for MLD gene therapy include optimizing the AAV dosage, selecting the most effective serotype, and determining the best route of administration for ARSA delivery into the central nervous system. This study aims to evaluate the safety and efficacy of AAV serotype 9 encoding ARSA (AAV9-ARSA) gene therapy when administered intravenously or intrathecally in minipigs, a large animal model with anatomical and physiological similarities to humans. By comparing these two administration methods, this study contributes to the understanding of how to improve the effectiveness of MLD gene therapy and offers valuable insights for future clinical applications.

A circular RNA produced by LRBA promotes cirrhotic mouse liver regeneration through facilitating the ubiquitination degradation of p27.

Accumulating circular RNAs (circRNAs) play important roles in tissue repair and organ regeneration. However, the biological effects of circRNAs on liver regeneration remain largely unknown. This study aims to systematically elucidate the functions and mechanisms of circRNAs derived from lipopolysaccharide-responsive beige-like anchor protein (LRBA) in regulating liver regeneration. CircRNAs derived from mouse LRBA gene were identified using CircBase. In vivo and in vitro experiments were conducted to confirm the effects of circLRBA on liver regeneration. RNA pull-down and RNA immunoprecipitation assays were used to investigate the underlying mechanisms. Clinical samples and cirrhotic mouse models were used to evaluate the clinical significance and transitional value of circLRBA. Eight circRNAs derived from LRBA were registered in CircBase. The circRNA mmu_circ_0018031 (circLRBA) was significantly upregulated in the liver tissues after 2/3 partial hepatectomy (PHx). Adeno-associated virus serotype 8 (AAV8)-mediated knockdown of circLRBA markedly inhibited mouse liver regeneration after 2/3 PHx. In vitro experiments confirmed that circLRBA exerted its growth-promoting function mainly through liver parenchymal cells. Mechanistically, circLRBA acted as a scaffold for the interaction between E3 ubiquitin-protein ligase ring finger protein 123 and p27, facilitating the ubiquitination degradation of p27. Clinically, circLRBA was lowly expressed in cirrhotic liver tissues and negatively correlated with perioperative levels of total bilirubin. Furthermore, overexpression of circLRBA enhanced cirrhotic mouse liver regeneration after 2/3 PHx. We conclude that circLRBA is a novel growth promoter in liver regeneration and a potential therapeutic target related to deficiency of cirrhotic liver regeneration.

Hepatic p38α MAPK controls gluconeogenesis via FOXO1 phosphorylation at S273 during glucagon signalling in mice.

Hyperglucagonaemia-stimulated hepatic glucose production (HGP) contributes to hyperglycaemia during type 2 diabetes. A better understanding of glucagon action is important to enable efficient therapies to be developed for the treatment of diabetes. Here, we aimed to investigate the role of p38 MAPK family members in glucagon-induced HGP and determine the underlying mechanisms by which p38 MAPK regulates glucagon action. p38α, β, γ and δ MAPK siRNAs were transfected into primary hepatocytes, followed by measurement of glucagon-induced HGP. Adeno-associated virus serotype 8 carrying p38α MAPK short hairpin RNA (shRNA) was injected into liver-specific Foxo1 knockout, liver-specific Irs1/Irs2 double knockout and Foxo1S273D knockin mice. Foxo1S273A knockin mice were fed a high-fat diet for 10 weeks. Pyruvate tolerance tests, glucose tolerance tests, glucagon tolerance tests and insulin tolerance tests were carried out in mice, liver gene expression profiles were analysed and serum triglyceride, insulin and cholesterol levels were measured. Phosphorylation of forkhead box protein O1 (FOXO1) by p38α MAPK in vitro was analysed by LC-MS. We found that p38α MAPK, but not the other p38 isoforms, stimulates FOXO1-S273 phosphorylation and increases FOXO1 protein stability, promoting HGP in response to glucagon stimulation. In hepatocytes and mouse models, inhibition of p38α MAPK blocked FOXO1-S273 phosphorylation, decreased FOXO1 levels and significantly impaired glucagon- and fasting-induced HGP. However, the effect of p38α MAPK inhibition on HGP was abolished by FOXO1 deficiency or a Foxo1 point mutation at position 273 from serine to aspartic acid (Foxo1S273D) in both hepatocytes and mice. Moreover, an alanine mutation at position 273 (Foxo1S273A) decreased glucose production, improved glucose tolerance and increased insulin sensitivity in diet-induced obese mice. Finally, we found that glucagon activates p38α through exchange protein activated by cAMP 2 (EPAC2) signalling in hepatocytes. This study found that p38α MAPK stimulates FOXO1-S273 phosphorylation to mediate the action of glucagon on glucose homeostasis in both health and disease. The glucagon-induced EPAC2-p38α MAPK-pFOXO1-S273 signalling pathway is a potential therapeutic target for the treatment of type 2 diabetes.

Evaluation of an AAV9-mini-dystrophin gene therapy candidate in a rat model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked disease caused by loss-of-function mutations in the dystrophin gene and is characterized by muscle wasting and early mortality. Adeno-associated virus-mediated gene therapy is being investigated as a treatment for DMD. In the nonclinical study documented here, we determined the effective dose of fordadistrogene movaparvovec, a clinical candidate adeno-associated virus serotype 9 vector carrying a human mini-dystrophin transgene, after single intravenous injection in a dystrophin-deficient (DMDmdx) rat model of DMD. Overall, we found that transduction efficiency, number of muscle fibers expressing the human mini-dystrophin polypeptide, improvement of the skeletal and cardiac muscle tissue architecture, correction of muscle strength and fatigability, and improvement of diastolic and systolic cardiac function were directly correlated with the amount of vector administered. The effective dose was then tested in older DMDmdx rats with a more dystrophic phenotype similar to the pathology observed in older patients with DMD. Except for a less complete rescue of muscle function in the oldest cohort, fordadistrogene movaparvovec was also found to be therapeutically effective in older DMDmdx rats, suggesting that this product may be appropriate for evaluation in patients with DMD at all stages of disease.

AAV6-Mediated Gene Therapy Prevents Developmental Dentin Defects in a Dentinogenesis Imperfecta Type Ⅲ Mouse Model.

Dentin is a major type of hard tissue of teeth and plays essential roles for normal tooth function. Odontoblasts are responsible for dentin formation. Mutations or deficiency in various genes affect the differentiation of odontoblasts, leading to irreversible dentin developmental defects in animals and humans. Whether such dentin defects can be reversed by gene therapy for odontoblasts remains unknown. In this study, we compare the infection efficiencies of six commonly used adeno-associated virus (AAV) serotypes (AAV1, AAV5, AAV6, AAV8, AAV9, and AAVDJ) in cultured mouse odontoblast-like cells (OLCs). We show that AAV6 serotype infects OLCs with the highest efficiency among the six AAVs. Two cellular receptors, which are able to recognize AAV6, AAV receptor (AAVR), and epidermal growth factor receptor (EGFR), are strongly expressed in the odontoblast layer of mouse teeth. After local administration to mouse molars, AAV6 infects the odontoblast layer with high efficiency. Furthermore, AAV6-Mdm2 was successfully delivered to teeth and prevents the defects in odontoblast differentiation and dentin formation in Mdm2 conditional knockout mice (a mouse model of dentinogenesis imperfecta type Ⅲ). These results suggest that AAV6 can serve as a reliable and efficient vehicle for gene delivery to odontoblasts through local injection. In addition, human OLCs were also successfully infected by AAV6 with high efficiency, and both AAVR and EGFR are strongly expressed in the odontoblast layer of extracted human developing teeth. These findings suggest that AAV6-mediated gene therapy through local injection may be a promising treatment approach for hereditary dentin disorders in humans.

Efficient adeno-associated virus serotype 5 capture with affinity functionalized nanofiber adsorbents.

Adeno-associated viruses (AAVs) are one of the most promising tools for gene therapy applications. These vectors are purified using affinity and ion exchange chromatography, typically using packed beds of resin adsorbents. This leads to diffusion and pressure drop limitations that affect process productivity. Due to their high surface area and porosity, electrospun nanofiber adsorbents offer mass transfer and flow rate advantages over conventional chromatographic media. The present work investigated the use of affinity cellulose-based nanofiber adsorbents for adeno-associated virus serotype 5 (AAV5) capture, evaluating dynamic binding capacity, pressure drop, and AAV5 recovery at residence times (RT) less than 5s. The dynamic binding capacity was found to be residence time-dependent, but nevertheless higher than 1.0 × 1014TP mL-1 (RT = 1.6s), with a pressure drop variation of 0.14MPa obtained after loading more than 2,000 column volumes of clarified AAV5 feedstock. The single affinity chromatography purification step using these new affinity adsorbents resulted in 80% virus recovery, with the removal of impurities comparable to that of bead-based affinity adsorbents. The high binding capacity, virus recovery and reduced pressure drop observed at residence times in the sub-minute range can potentially eliminate the need for prior concentration steps, thereby reducing the overall number of unit operations, process time and costs.

Clinical applications of gene therapy for rare diseases: A review.

Rare diseases collectively exact a high toll on society due to their sheer number and overall prevalence. Their heterogeneity, diversity, and nature pose daunting clinical challenges for both management and treatment. In this review, we discuss recent advances in clinical applications of gene therapy for rare diseases, focusing on a variety of viral and non-viral strategies. The use of adeno-associated virus (AAV) vectors is discussed in the context of Luxturna, licenced for the treatment of RPE65 deficiency in the retinal epithelium. Imlygic, a herpes virus vector licenced for the treatment of refractory metastatic melanoma, will be an example of oncolytic vectors developed against rare cancers. Yescarta and Kymriah will showcase the use of retrovirus and lentivirus vectors in the autologous ex vivo production of chimeric antigen receptor T cells (CAR-T), licenced for the treatment of refractory leukaemias and lymphomas. Similar retroviral and lentiviral technology can be applied to autologous haematopoietic stem cells, exemplified by Strimvelis and Zynteglo, licenced treatments for adenosine deaminase-severe combined immunodeficiency (ADA-SCID) and β-thalassaemia respectively. Antisense oligonucleotide technologies will be highlighted through Onpattro and Tegsedi, RNA interference drugs licenced for familial transthyretin (TTR) amyloidosis, and Spinraza, a splice-switching treatment for spinal muscular atrophy (SMA). An initial comparison of the effectiveness of AAV and oligonucleotide therapies in SMA is possible with Zolgensma, an AAV serotype 9 vector, and Spinraza. Through these examples of marketed gene therapies and gene cell therapies, we will discuss the expanding applications of such novel technologies to previously intractable rare diseases.

Assessment of Residual Full-Length SV40 Large T Antigen in Clinical-Grade Adeno-Associated Virus Vectors Produced in 293T Cells.

Efficient production of adeno-associated virus (AAV) vectors is a significant challenge. Human embryonic kidney HEK293T cells are widely used in good manufacturing practice facilities, producing higher yield of AAV vectors for clinical applications than HEK293 through the addition of a constitutive expression of SV40 large T antigen (SV40T), which stimulates Rep expression. However, the theoretical potential for tumorigenic consequences of a clinical AAV product containing residual DNA encoding SV40T, which may inhibit p53 growth suppressive functions is a safety concern. Although the risk is theoretical, to assure a low risk/high confidence of safety for clinical drug development, we have established a sensitive assay for assessment of functional full-length transcription competent SV40T DNA in HEK293T cell-produced AAV vectors. Using HEK293T generated 8, 9, and rh.10 serotype AAV vectors, the presence of SV40T in purified vector was assessed in vitro using quantitative polymerase chain reaction (qPCR) targeting a 129 bp amplicon combined with nested PCR targeting full-length SV40T DNA. Although low levels of the smaller amplicon were present in each AAV serotype, the full-length SV40T was undetectable. No transcription competent full-length SV40T DNA was observed by reverse transcription-quantitative polymerase chain reaction using an in vivo amplification of signal in mouse liver administered (2-10 × 1010 gc) 129 bp amplicon-positive AAV vectors. As a control for gene transfer, high levels of expressed transgene mRNAs were observed from each serotype AAV vector, yet, SV40T mRNA was undetectable. In vivo assessment of these three liver-tropic AAV serotypes, each with amplicon-positive qPCR SV40T DNA, demonstrated high transgene mRNA expression but no SV40T mRNA, that is, detection of small segments of SV40T DNA in 293T cell produced AAV inappropriately leads to the conclusion of residuals with the potential to express SV40T. This sensitive assay can be used to assess the level, if any, of SV40T antigen contaminating AAV vectors generated by HEK293T cells. ClinicalTrials.gov identifier: NCT03634007; NCT05302271; NCT01414985; NCT01161576.

A novel dual-plasmid platform provides scalable transfection yielding improved productivity and packaging across multiple AAV serotypes and genomes

Transient transfection of mammalian cells using plasmid DNA is a standard method to produce adeno-associated virus (AAV) vectors allowing for flexible and scalable manufacture. Typically, three plasmids are used to encode the necessary components to facilitate vector production; however, a dual-plasmid system, termed pDG, was introduced over 2 decades ago demonstrating two components could be combined resulting in comparable productivity to triple transfection. We have developed a novel dual-plasmid system, pOXB, with an alternative arrangement of sequences that results in significantly increased AAV vector productivity and percentage of full capsids packaged in comparison to the pDG dual design and triple transfection. Here, we demonstrate the reproducibility of these findings across seven recombinant AAV genomes and multiple capsid serotypes as well as the scalability of the pOXB dual-plasmid transfection at 50-L bioreactor scale. Purified drug substance showed a consistent product quality profile in line with triple-transfected vectors, except for a substantial improvement in intact genomes packaged using the pOXB dual- transfection system. Furthermore, pOXB dual- and triple-transfection-based vectors performed consistently invivo. The pOXB dual plasmid represents an innovation in AAV manufacturing resulting in significant process gains while maintaining the flexibility of a transient transfection platform.