Did Dendritic Cell Activation, Induced by Adenovirus-Antibody Complexes, Play a Role in the Death of Jesse Gelsinger?

Next-generation biological vector platforms for in vivo delivery of genome editing agents

CRISPR-based genome editing holds promise for addressing genetic disease, infectious disease, and cancer and has rapidly advanced from primary research to clinical trials in recent years. However, the lack of safe and potent in vivo delivery methods for CRISPR components has limited most ongoing clinical trials to ex vivo gene therapy. Effective CRISPR in vivo genome editing necessitates an effective vehicle ensuring target cell transduction while minimizing off-target effects, toxicity, and immune reactions. In this review, we examine promising biological-derived platforms to deliver DNA editing agents in vivo and the engineering thereof, encompassing potent viral-based vehicles, flexible protein nanocages, and mammalian-derived particles.

Viral vectors for gene delivery to the central nervous system

Brain diseases with a known or suspected genetic basis represent an important frontier for advanced therapeutics. The central nervous system (CNS) is an intricate network in which diverse cell types with multiple functions communicate via complex signaling pathways, making therapeutic intervention in brain-related diseases challenging. Nevertheless, as more information on the molecular genetics of brain-related diseases becomes available, genetic intervention using gene therapeutic strategies should become more feasible. There remain, however, several significant hurdles to overcome that relate to (i) the development of appropriate gene vectors and (ii) methods to achieve local or broad vector delivery. Clearly, gene delivery tools must be engineered for distribution to the correct cell type in a specific brain region and to accomplish therapeutic transgene expression at an appropriate level and duration. They also must avoid all toxicity, including the induction of inflammatory responses. Over the last 40 years, various types of viral vectors have been developed as tools to introduce therapeutic genes into the brain, primarily targeting neurons. This review describes the most prominent vector systems currently approaching clinical application for CNS disorders and highlights both remaining challenges as well as improvements in vector designs that achieve greater safety, defined tropism, and therapeutic gene expression.

Development of oncolytic and gene therapy vectors based on adenovirus serotype 4 as an alternative to adenovirus serotype 5

BACKGROUND

Adenoviral vectors are among the most frequently used vectors for gene therapy and cancer treatment. Most vectors are derived from human adenovirus (Ad) serotype 5 despite limited applicability caused by pre-existing immunity and unfavorable liver tropism, whereas the other more than 100 known human serotypes remain largely unused. Here, we screened a library of human Ad types and identified Ad4 as a promising candidate vector.

METHODS

Reporter-gene-expressing viruses representative of the natural human Ad diversity were used to transduce an array of muscle cell lines and two- or three-dimensional tumor cultures. The time-course of transgene expression was monitored by fluorescence or luminescence measurements. To generate replication-deficient Ad4 vector genomes, successive homologous recombination was applied.

RESULTS

Ad4, 17 and 50 transduced human cardiomyocytes more efficiently than Ad5, whereas Ad37 was found to be superior in rhabdomyocytes. Despite its moderate transduction efficiency, Ad4 showed efficient and long-lasting gene expression in papillomavirus (HPV) positive tumor organoids. Therefore, we aimed to harness the potential of Ad4 for improved muscle transduction or oncolytic virotherapy of HPV-positive tumors. We deleted the E1 and E3 transcription units to produce first generation Ad vectors for gene therapy. The E1- and E1/E3-deleted vectors were replication-competent in HEK293 cells stably expressing E1 but not in the other cell lines tested. Furthermore, we show that the Ad5 E1 transcription unit can complement the replication of E1-deleted Ad4 vectors.

CONCLUSIONS

Our Ad4-based gene therapy vector platform contributes to the development of improved Ad vectors based on non-canonical serotypes for a broad range of applications.

Public Attitudes About the Use of Gene Therapy in Mainland China

Importance

In addition to technical barriers, public attitudes about the use of gene therapy have an important association with the clinical implementation of gene therapy.

Objective

To investigate the factors associated with public acceptance of gene therapy among individuals in China.

Design, Setting, and Participants

This cross-sectional study used data from a survey conducted among 21 880 individuals in mainland China from June 20 to August 31, 2022.

Main Outcomes and Measures

Stepwise linear regression was used to analyze factors associated with public acceptance of gene therapy in 5 key areas: basic personal information (gender, region, age, and educational level), family situation (marital status, children, and cousins), economic status (assets, debts, and insurance coverage), health knowledge (health literacy score and media use), and physical health status (chronic illness, cancer, European Quality of Life 5-Dimension 5-Level version [EQ-5D-5L] score, and Brief Illness Perception Questionnaire [BIPQ] score). Acceptance scores were calculated based on a visual analog scale (range, 0-100, with higher scores indicating higher acceptance of gene therapy). Further subgroup analysis was carried out in different age subgroups and populations with or without chronic diseases.

Results

A total of 21 880 participants (mean [SD] age, 39.4 [18.9] years; 10 947 female participants [50.0%]; 10 933 male participants [50.0%]) were analyzed in this study. The mean (SD) acceptance score of gene therapy in the survey was 60.56 (27.60). Compared with people aged 60 years or older, those aged 12 to 18 years had higher acceptance of gene therapy (β = 1.48 [95% CI, 0.09-2.88]), while groups aged 19 to 30 years (β = -3.43 [95% CI, -4.80 to -2.07]), 31 to 44 years (β = -1.44 [95% CI, -2.76 to -0.12]), and 45 to 59 years (β = -2.05 [95% CI, -3.27 to -0.83]) had lower acceptance. Compared with people living in Eastern China, those in Central China had lower acceptance of gene therapy (β = -1.58 [95% CI, -2.54 to -0.62]), while those in Western China had higher acceptance (β = 0.92 [95% CI, 0.09-1.76]). Higher educational level (undergraduate or above vs junior high or below) was associated with higher acceptance of gene therapy (β = 1.56 [95% CI, 0.49-2.63]). Number of properties owned was also associated with higher acceptance of gene therapy (2 vs 0: β = 2.38 [95% CI, 1.04-3.72]; ≥3 vs 0: β = 4.66 [95% CI, 2.92-6.39]). Diagnosis of chronic disease was associated with lower acceptance of gene therapy (β = -17.86 [95% CI, -20.49 to -15.24]), while diagnosis of cancer was associated with higher acceptance (β = 6.99 [95% CI, 1.84-12.14]). Higher BIPQ score (β = 0.40 [95% CI, 0.34-0.45]), higher health literacy score (β = 0.70 [95% CI, 0.62-0.78]), and media use (β = 0.49 [95% CI, 0.41-0.57]) were all associated with high acceptance of gene therapy, while a higher EQ-5D-5L score was associated with lower acceptance (β = -0.29 [95% CI, -0.47 to -0.11]). For older people, being in debt, not having health insurance, and the EQ-5D-5L score were uniquely relevant factors. For people with chronic disease, having an undergraduate degree or higher, a diagnosis of cancer, and the BIPQ score were uniquely relevant factors.

Conclusions and Relevance

These results suggest that basic personal information, economic status, health knowledge, and physical health status were the main factors associated with the acceptance of gene therapy. Improving the health literacy of the population and promoting trust in gene therapy may be effective ways to increase the acceptance of gene therapy. Poorer economic levels and worse disease states may reduce the public's willingness to accept gene therapy.

The Promise and the Hope of Gene Therapy

It has been over 30 years since visionary scientists came up with the term "Gene Therapy," suggesting that for certain indications, mostly monogenic diseases, substitution of the missing or mutated gene with the normal allele via gene addition could provide long-lasting therapeutic effect to the affected patients and consequently improve their quality of life. This notion has recently become a reality for certain diseases such as hemoglobinopathies and immunodeficiencies and other monogenic diseases. However, the therapeutic wave of gene therapies was not only applied in this context but was more broadly employed to treat cancer with the advent of CAR-T cell therapies. This review will summarize the gradual advent of gene therapies from bench to bedside with a main focus on hemopoietic stem cell gene therapy and genome editing and will provide some useful insights into the future of genetic therapies and their gradual integration in the everyday clinical practice.

IgG-Complexed Adenoviruses Induce Human Plasmacytoid Dendritic Cell Activation and Apoptosis

Following repeat exposure to many human adenoviruses (HAdVs), most adults harbour long-lived B- and T-cell responses. Combined, this response typically protects us for years from re-infection by the same HAdV type. In spite of these immune responses, some HAdV types are associated with persistent infections that constitute a life-threatening risk when an individual's T-cell response is compromised. By contrast, patients with B-cell deficiencies do not appear to be at a greater risk of HAdV disease. This dichotomy begs the question of the secondary role of anti-HAdV antibodies during host defence. In this study, we explored IgG-complexed (IC)-HAdV5 and primary human plasmacytoid dendritic cell (pDC) interactions. We found that IC-HAdV5 are efficiently internalized in pDCs, stimulate their activation through TLR9 signalling, and cause apoptosis. These data may help reconcile the enigma of robust immune response to HAdVs, while concurrently allowing persistence.

Intravenous delivery of adeno-associated viral gene therapy in feline GM1 gangliosidosis

GM1 gangliosidosis is a fatal neurodegenerative disease caused by a deficiency of lysosomal β-galactosidase. In its most severe form, GM1 gangliosidosis causes death by 4 years of age, and no effective treatments exist. Previous work has shown that injection of the brain parenchyma with an adeno-associated viral vector provides pronounced therapeutic benefit in a feline GM1 model. To develop a less invasive treatment for the brain and increase systemic biodistribution, intravenous injection of AAV9 was evaluated. AAV9 expressing feline β-galactosidase was intravenously administered at 1.5x1013 vector genomes/kilogram body weight to six GM1 cats at approximately 1 month of age. The animals were divided into two cohorts: 1) a long-term group, which was followed to humane endpoint, and 2) a short-term group, which was analyzed 16-weeks post treatment. Clinical assessments included neurological exams, cerebrospinal fluid and urine biomarkers, and 7-Telsa magnetic resonance imaging and spectroscopy. Postmortem analysis included β-galactosidase and virus distribution, histological analysis, and ganglioside content. Untreated GM1 animals survived 8.0 ± 0.6 months while intravenous treatment increased survival to an average of 3.5 years (n = 2) with substantial improvements in quality of life and neurologic function. Neurological abnormalities, which in untreated animals progress to the inability to stand and debilitating neurological disease by 8 months of age, were mild in all treated animals. Cerebrospinal fluid biomarkers were normalized, indicating decreased central nervous system cell damage in the treated animals. Urinary glycosaminoglycans decreased to normal levels in the long-term cohort. Magnetic resonance imaging and spectroscopy showed partial preservation of the brain in treated animals, which was supported by postmortem histological evaluation. β-galactosidase activity was increased throughout the central nervous system, reaching carrier levels in much of the cerebrum and normal levels in the cerebellum, spinal cord and cerebrospinal fluid. Ganglioside accumulation was significantly reduced by treatment. Peripheral tissues such as heart, skeletal muscle, and sciatic nerve also had normal β-galactosidase activity in treated GM1 cats. GM1 histopathology was largely corrected with treatment. There was no evidence of tumorigenesis or toxicity. Restoration of β-galactosidase activity in the central nervous system and peripheral organs by intravenous gene therapy led to profound increases in lifespan and quality of life in GM1 cats. This data supports the promise of intravenous gene therapy as a safe, effective treatment for GM1 gangliosidosis.

Adenovirus-Extracellular Protein Interactions and Their Impact on Innate Immune Responses by Human Mononuclear Phagocytes

The aim of this review is to highlight how, in a syngeneic system, human mononuclear phagocytes respond to environments containing human adenovirus (HAdV) and soluble extracellular proteins that influence their innate immune response. Soluble extracellular proteins, including immunoglobulins, blood clotting factors, proteins of the complement system, and/or antimicrobial peptides (AMPs) can exert direct effects by binding to a virus capsid that modifies interactions with pattern recognition receptors and downstream signaling. In addition, the presence, generation, or secretion of extracellular proteins can indirectly influence the response to HAdVs via the activation and recruitment of cells at the site of infection.