Self-inactivating lentivirus vector for safe and efficient in vivo gene delivery

Mechanisms and Delivery of tRNA Therapeutics

Transfer ribonucleic acid (tRNA) therapeutics will provide personalized and mutation specific medicines to treat human genetic diseases for which no cures currently exist. The tRNAs are a family of adaptor molecules that interpret the nucleic acid sequences in our genes into the amino acid sequences of proteins that dictate cell function. Humans encode more than 600 tRNA genes. Interestingly, even healthy individuals contain some mutant tRNAs that make mistakes. Missense suppressor tRNAs insert the wrong amino acid in proteins, and nonsense suppressor tRNAs read through premature stop signals to generate full length proteins. Mutations that underlie many human diseases, including neurodegenerative diseases, cancers, and diverse rare genetic disorders, result from missense or nonsense mutations. Thus, specific tRNA variants can be strategically deployed as therapeutic agents to correct genetic defects. We review the mechanisms of tRNA therapeutic activity, the nature of the therapeutic window for nonsense and missense suppression as well as wild-type tRNA supplementation. We discuss the challenges and promises of delivering tRNAs as synthetic RNAs or as gene therapies. Together, tRNA medicines will provide novel treatments for common and rare genetic diseases in humans.

Recent Therapeutic Gene Editing Applications to Genetic Disorders

Recent years have witnessed unprecedented progress in therapeutic gene editing, revolutionizing the approach to treating genetic disorders. In this comprehensive review, we discuss the progression of milestones leading to the emergence of the clustered regularly interspaced short palindromic repeats (CRISPR)-based technology as a powerful tool for precise and targeted modifications of the human genome. CRISPR-Cas9 nuclease, base editing, and prime editing have taken center stage, demonstrating remarkable precision and efficacy in targeted ex vivo and in vivo genomic modifications. Enhanced delivery systems, including viral vectors and nanoparticles, have further improved the efficiency and safety of therapeutic gene editing, advancing their clinical translatability. The exploration of CRISPR-Cas systems beyond the commonly used Cas9, such as the development of Cas12 and Cas13 variants, has expanded the repertoire of gene editing tools, enabling more intricate modifications and therapeutic interventions. Outstandingly, prime editing represents a significant leap forward, given its unparalleled versatility and minimization of off-target effects. These innovations have paved the way for therapeutic gene editing in a multitude of previously incurable genetic disorders, ranging from monogenic diseases to complex polygenic conditions. This review highlights the latest innovative studies in the field, emphasizing breakthrough technologies in preclinical and clinical trials, and their applications in the realm of precision medicine. However, challenges such as off-target effects and ethical considerations remain, necessitating continued research to refine safety profiles and ethical frameworks.

Non-esterified fatty acid palmitate facilitates oxidative endoplasmic reticulum stress and apoptosis of β-cells by upregulating ERO-1α expression

Adipose tissue-derived non-esterified saturated long-chain fatty acid palmitate (PA) decisively contributes to β-cell demise in type 2 diabetes mellitus in part through the excessive generation of hydrogen peroxide (H2O2). The endoplasmic reticulum (ER) as the primary site of oxidative protein folding could represent a significant source of H2O2. Both ER-oxidoreductin-1 (ERO-1) isoenzymes, ERO-1α and ERO-1β, catalyse oxidative protein folding within the ER, generating equimolar amounts of H2O2 for every disulphide bond formed. However, whether ERO-1-derived H2O2 constitutes a potential source of cytotoxic luminal H2O2 under lipotoxic conditions is still unknown. Here, we demonstrate that both ERO-1 isoforms are expressed in pancreatic β-cells, but interestingly, PA only significantly induces ERO-1α. Its specific deletion significantly attenuates PA-mediated oxidative ER stress and subsequent β-cell death by decreasing PA-mediated ER-luminal and mitochondrial H2O2 accumulation, by counteracting the dysregulation of ER Ca2+ homeostasis, and by mitigating the reduction of mitochondrial membrane potential and lowered ATP content. Moreover, ablation of ERO-1α alleviated PA-induced hyperoxidation of the ER redox milieu. Importantly, ablation of ERO-1α did not affect the insulin secretory capacity, the unfolded protein response, or ER redox homeostasis under steady-state conditions. The involvement of ERO-1α-derived H2O2 in PA-mediated β-cell lipotoxicity was corroborated by the overexpression of a redox-active ERO-1α underscoring the proapoptotic activity of ERO-1α in pancreatic β-cells. Overall, our findings highlight the critical role of ERO-1α-derived H2O2 in lipotoxic ER stress and β-cell failure.

RANBP17 Overexpression Restores Nucleocytoplasmic Transport and Ameliorates Neurodevelopment in Induced DYT1 Dystonia Motor Neurons

DYT1 dystonia is a debilitating neurological movement disorder, and it represents the most frequent and severe form of hereditary primary dystonia. There is currently no cure for this disease due to its unclear pathogenesis. In our previous study utilizing patient-specific motor neurons (MNs), we identified distinct cellular deficits associated with the disease, including a deformed nucleus, disrupted neurodevelopment, and compromised nucleocytoplasmic transport (NCT) functions. However, the precise molecular mechanisms underlying these cellular impairments have remained elusive. In this study, we revealed the genome-wide changes in gene expression in DYT1 MNs through transcriptomic analysis. We found that those dysregulated genes are intricately involved in neurodevelopment and various biological processes. Interestingly, we identified that the expression level of RANBP17, a RAN-binding protein crucial for NCT regulation, exhibited a significant reduction in DYT1 MNs. By manipulating RANBP17 expression, we further demonstrated that RANBP17 plays an important role in facilitating the nuclear transport of both protein and transcript cargos in induced human neurons. Excitingly, the overexpression of RANBP17 emerged as a substantial mitigating factor, effectively restoring impaired NCT activity and rescuing neurodevelopmental deficits observed in DYT1 MNs. These findings shed light on the intricate molecular underpinnings of impaired NCT in DYT1 neurons and provide novel insights into the pathophysiology of DYT1 dystonia, potentially leading to the development of innovative treatment strategies.

Combining CRISPR-Cas9 and TCR exchange to generate a safe and efficient cord blood-derived T cell product for pediatric relapsed AML

BACKGROUND

Hematopoietic cell transplantation (HCT) is an effective treatment for pediatric patients with high-risk, refractory, or relapsed acute myeloid leukemia (AML). However, a large proportion of transplanted patients eventually die due to relapse. To improve overall survival, we propose a combined strategy based on cord blood (CB)-HCT with the application of AML-specific T cell receptor (TCR)-engineered T cell therapy derived from the same CB graft.

METHODS

We produced CB-CD8+ T cells expressing a recombinant TCR (rTCR) against Wilms tumor 1 (WT1) while lacking endogenous TCR (eTCR) expression to avoid mispairing and competition. CRISPR-Cas9 multiplexing was used to target the constant region of the endogenous TCRα (TRAC) and TCRβ (TRBC) chains. Next, an optimized method for lentiviral transduction was used to introduce recombinant WT1-TCR. The cytotoxic and migration capacity of the product was evaluated in coculture assays for both cell lines and primary pediatric AML blasts.

RESULTS

The gene editing and transduction procedures achieved high efficiency, with up to 95% of cells lacking eTCR and over 70% of T cells expressing rWT1-TCR. WT1-TCR-engineered T cells lacking the expression of their eTCR (eTCR-/- WT1-TCR) showed increased cell surface expression of the rTCR and production of cytotoxic cytokines, such as granzyme A and B, perforin, interferon-γ (IFNγ), and tumor necrosis factor-α (TNFα), on antigen recognition when compared with WT1-TCR-engineered T cells still expressing their eTCR (eTCR+/+ WT1-TCR). CRISPR-Cas9 editing did not affect immunophenotypic characteristics or T cell activation and did not induce increased expression of inhibitory molecules. eTCR-/- WT1-TCR CD8+ CB-T cells showed effective migratory and killing capacity in cocultures with neoplastic cell lines and primary AML blasts, but did not show toxicity toward healthy cells.

CONCLUSIONS

In summary, we show the feasibility of developing a potent CB-derived CD8+ T cell product targeting WT1, providing an option for post-transplant allogeneic immune cell therapy or as an off-the-shelf product, to prevent relapse and improve the clinical outcome of children with AML.

Optimised protocols to generate high titre lentiviral vectors using a novel transfection agent enabling extended HEK293T culture following transient transfection and suspension culture

HIV-1 based lentiviral viruses are considered powerful and versatile gene therapy vectors to deliver therapeutic genes to patients with hereditary or acquired diseases. These vectors can efficiently transduce a variety of cell types when dividing or non-dividing to provide permanent delivery and long-term gene expression. Demand for scalable manufacturing protocols able to generate enough high titre vector for widespread use of this technology is increasing and considerable efforts to improve vector production cost-effectively, is ongoing. Current methods for LV production mainly use transient transfection of producer cell lines. Cells can be grown at scale, either in 2D relying on culturing producer cells in multi-tray flask cell culture factories or in roller bottles or can be adapted to grow in 3D suspensions in large batch fermenters. This suits rapid production and testing of new vector constructs pre-clinically for their efficacy, particle titre and safety. In this study, we sought to improve lentiviral titre over time by testing two alternative commercially available transfection reagents Fugene® 6 and Genejuice® with the commonly used polycation, polyethyleneimine. Our aim was to identify less cytotoxic transfection reagents that could be used to generate LV particles at high titre past the often used 72 h period when vector is usually collected before producer cell death is caused due to post transfection cytotoxicity. We show that LV could be produced in extended culture using Genejuice® and even by transfected cells in glass flasks in suspension. Because this delivery agent is less toxic to 293 T producer cells, following optimisation of transfection we found that LV can be harvested for more than 10 days at high titre. Using our protocol, titres of 109 TU/ml and 108 TU/ml were routinely reached via traditional monolayer conditions or suspension cultures, respectively. We propose, this simple change in vector production enables large volumes of high titre vector to be produced, cost effectively for non-clinical in vivo and in vitro applications or for more stringent downstream clinical grade vector purification.

Microglia cells treated with synthetic vasoactive intestinal peptide or transduced with LentiVIP protect neuronal cells against degeneration

A common pathological hallmark of neurodegenerative disorders is neuronal cell death, accompanied by neuroinflammation and oxidative stress. The vasoactive intestinal peptide (VIP) is a pleiotropic peptide that combines neuroprotective and immunomodulatory actions. The gene therapy field shows long-term promise for treating a wide range of neurodegenerative diseases (ND). In this study, we aimed to investigate the in vitro efficacy of transduction of microglia using lentiviral gene therapy vectors encoding VIP (LentiVIP). Additionally, we tested the protective effects of the secretome derived from LentiVIP-infected "immortalized human" microglia HMC3 cells, and cells treated with Synthetic VIP (SynVIP), against toxin-induced neurodegeneration. First, LentiVIP, which stably expresses VIP, was generated and purified. VIP secretion in microglial conditioned media (MG CM) for LentiVIP-infected HMC3 microglia cells was confirmed. Microglia cells were activated with lipopolysaccharide, and groups were formed as follows: 1) Control, 2) SynVIP-treated, or 3) LentiVIP-transduced. These MG CM were applied on an in vitro neurodegenerative model formed by differentiated (d)-SH-SY5Y cells. Then, cell survival analysis and apoptotic nuclear staining, besides measurement of oxidative/inflammatory parameters in CM of cells were performed. Activated MG CM reduced survival rates of both control and toxin-applied (d)-SH-SY5Y cells, whereas LentiVIP-infected MG CM and SynVIP-treated ones exhibited better survival rates. These findings were supported by apoptotic nuclear evaluations of (d)-SH-SY5Y cells, alongside oxidative/inflammatory parameters in their CM. LentiVIP seems worthy of further studies for the treatment of ND because of the potential of gene therapy to treat diseases effectively with a single injection.

Altered vacuole membrane protein 1 (VMP1) expression is associated with increased NLRP3 inflammasome activation and mitochondrial dysfunction

BACKGROUND

Altered expression of vacuole membrane protein 1 (VMP1) has recently been observed in the context of multiple sclerosis and Parkinson's disease (PD). However, how changes in VMP1 expression may impact pathogenesis has not been explored.

OBJECTIVE

This study aimed to characterize how altered VMP1 expression affects NLRP3 inflammasome activation and mitochondrial function.

METHODS

VMP1 expression was depleted in a monocytic cell line using CRISPR-Cas9. The effect of VMP1 on NLRP3 inflammasome activation was examined by stimulating cells with LPS and ATP or α-synuclein fibrils. Inflammasome activation was determined by caspase-1 activation using both a FLICA assay and a biosensor as well as by the release of proinflammatory molecules measured by ELISA. RNA-sequencing was utilized to define global gene expression changes resulting from VMP1 deletion. SERCA activity and mitochondrial function were investigated using various fluorescence microscopy-based approaches including a novel method that assesses the function of individual mitochondria in a cell.

RESULTS

Here, we report that genetic deletion of VMP1 from a monocytic cell line resulted in increased NLRP3 inflammasome activation and release of proinflammatory molecules. Examination of the VMP1-dependent changes in these cells revealed that VMP1 deficiency led to decreased SERCA activity and increased intracellular [Ca2+]. We also observed calcium overload in mitochondria in VMP1 depleted cells, which was associated with mitochondrial dysfunction and release of mitochondrial DNA into the cytoplasm and the extracellular environment.

CONCLUSIONS

Collectively, these studies reveal VMP1 as a negative regulator of inflammatory responses, and we postulate that decreased expression of VMP1 can aggravate the inflammatory sequelae associated with neurodegenerative diseases like PD.

Targeting pediatric cancers via T-cell recognition of the monomorphic MHC class I-related protein MR1

Human leukocyte antigen (HLA) restriction of conventional T-cell targeting introduces complexity in generating T-cell therapy strategies for patients with cancer with diverse HLA-backgrounds. A subpopulation of atypical, major histocompatibility complex-I related protein 1 (MR1)-restricted T-cells, distinctive from mucosal-associated invariant T-cells (MAITs), was recently identified recognizing currently unidentified MR1-presented cancer-specific metabolites. It is hypothesized that the MC.7.G5 MR1T-clone has potential as a pan-cancer, pan-population T-cell immunotherapy approach. These cells are irresponsive to healthy tissue while conferring T-cell receptor(TCR) dependent, HLA-independent cytotoxicity to a wide range of adult cancers. Studies so far are limited to adult malignancies. Here, we investigated the potential of MR1-targeting cellular therapy strategies in pediatric cancer. Bulk RNA sequencing data of primary pediatric tumors were analyzed to assess MR1 expression. In vitro pediatric tumor models were subsequently screened to evaluate their susceptibility to engineered MC.7.G5 TCR-expressing T-cells. Targeting capacity was correlated with qPCR-based MR1 mRNA and protein overexpression. RNA expression of MR1 in primary pediatric tumors varied widely within and between tumor entities. Notably, embryonal tumors exhibited significantly lower MR1 expression than other pediatric tumors. In line with this, most screened embryonal tumors displayed resistance to MR1T-targeting in vitro MR1T susceptibility was observed particularly in pediatric leukemia and diffuse midline glioma models. This study demonstrates potential of MC.7.G5 MR1T-cell immunotherapy in pediatric leukemias and diffuse midline glioma, while activity against embryonal tumors was limited. The dismal prognosis associated with relapsed/refractory leukemias and high-grade brain tumors highlights the promise to improve survival rates of children with these cancers.

Trans-lesion synthesis and mismatch repair pathway crosstalk defines chemoresistance and hypermutation mechanisms in glioblastoma

Almost all Glioblastoma (GBM) are either intrinsically resistant to the chemotherapeutical drug temozolomide (TMZ) or acquire therapy-induced mutations that cause chemoresistance and recurrence. The genome maintenance mechanisms responsible for GBM chemoresistance and hypermutation are unknown. We show that the E3 ubiquitin ligase RAD18 (a proximal regulator of TLS) is activated in a Mismatch repair (MMR)-dependent manner in TMZ-treated GBM cells, promoting post-replicative gap-filling and survival. An unbiased CRISPR screen provides an aerial map of RAD18-interacting DNA damage response (DDR) pathways deployed by GBM to tolerate TMZ genotoxicity. Analysis of mutation signatures from TMZ-treated GBM reveals a role for RAD18 in error-free bypass of O6mG (the most toxic TMZ-induced lesion), and error-prone bypass of other TMZ-induced lesions. Our analyses of recurrent GBM patient samples establishes a correlation between low RAD18 expression and hypermutation. Taken together we define molecular underpinnings for the hallmark tumorigenic phenotypes of TMZ-treated GBM.

Gene therapy for adenosine deaminase severe combined immune deficiency-An unexpected journey of four decades

Severe combined immune deficiency due to adenosine deaminase deficiency (ADA SCID) is an inborn error of immunity with pan-lymphopenia, due to accumulated cytotoxic adenine metabolites. ADA SCID has been treated using gene therapy with a normal human ADA gene added to autologous hematopoietic stem cells (HSC) for over 30 years. Iterative improvements in vector design, HSC processing methods, and clinical HSC transplant procedures have led nearly all ADA SCID gene therapy patients to achieve consistently beneficial immune restoration with stable engraftment of ADA gene-corrected HSC over the duration of observation (as long as 20 years). One gene therapy for ADA SCID is approved by the European Medicines Agency (EMA) in the European Union (EU) and another is being advanced to licensure in the U.S. and U.K. Despite the clear-cut benefits and safety of this curative gene and cell therapy, it remains challenging to achieve sustained availability and access, especially for rare disorders like ADA SCID.

Advances in HIV Gene Therapy

Early gene therapy studies held great promise for the cure of heritable diseases, but the occurrence of various genotoxic events led to a pause in clinical trials and a more guarded approach to progress. Recent advances in genetic engineering technologies have reignited interest, leading to the approval of the first gene therapy product targeting genetic mutations in 2017. Gene therapy (GT) can be delivered either in vivo or ex vivo. An ex vivo approach to gene therapy is advantageous, as it allows for the characterization of the gene-modified cells and the selection of desired properties before patient administration. Autologous cells can also be used during this process which eliminates the possibility of immune rejection. This review highlights the various stages of ex vivo gene therapy, current research developments that have increased the efficiency and safety of this process, and a comprehensive summary of Human Immunodeficiency Virus (HIV) gene therapy studies, the majority of which have employed the ex vivo approach.

Engineering an Autonucleolytic Mammalian Suspension Host Cell Line to Reduce DNA Impurity Levels in Serum-Free Lentiviral Process Streams

We engineered HEK293T cells with a transgene encoding tetracycline-inducible expression of a Staphylococcus aureus nuclease incorporating a translocation signal. We adapted the unmodified and nuclease-engineered cell lines to grow in suspension in serum-free media, generating the HEK293TS and NuPro-2S cell lines, respectively. Transient transfection yielded 1.19 × 106 lentiviral transducing units per milliliter (TU/mL) from NuPro-2S cells and 1.45 × 106 TU/mL from HEK293TS cells. DNA ladder disappearance revealed medium-resident nuclease activity arising from NuPro-2S cells in a tetracycline-inducible manner. DNA impurity levels in lentiviral material arising from NuPro-2S and HEK293TS cells were undetectable by SYBR Safe agarose gel staining. Direct measurement by PicoGreen reagent revealed DNA to be present at 636 ng/mL in lentiviral material from HEK293TS cells, an impurity level reduced by 89% to 70 ng/mL in lentiviral material from NuPro-2S cells. This reduction was comparable to the 23 ng/mL achieved by treating HEK293TS-derived lentiviral material with 50 units/mL Benzonase.

Gene therapy for heart failure: A novel treatment for the age old disease

Across the globe, cardiovascular disease (CVD) is the leading cause of mortality. According to reports, around 6.2 million people in the United states have heart failure. Current standards of care for heart failure can delay but not prevent progression of disease. Gene therapy is one of the novel treatment modalities that promises to fill this limitation in the current standard of care for Heart Failure. In this paper we performed an extensive search of the literature on various advances made in gene therapy for heart failure till date. We review the delivery methods, targets, current applications, trials, limitations and feasibility of gene therapy for heart failure. Various methods have been employed till date for administering gene therapies including but not limited to arterial and venous infusion, direct myocardial injection and pericardial injection. Various strategies such as AC6 expression, S100A1 protein upregulation, VEGF-B and SDF-1 gene therapy have shown promise in recent preclinical trials. Furthermore, few studies even show that stimulation of cardiomyocyte proliferation such as through cyclin A2 overexpression is a realistic avenue. However, a considerable number of obstacles need to be overcome for gene therapy to be part of standard treatment of care such as definitive choice of gene, gene delivery systems and a suitable method for preclinical trials and clinical trials on patients. Considering the challenges and taking into account the recent advances in gene therapy research, there are encouraging signs to indicate gene therapy for heart failure to be a promising treatment modality for the future. However, the time and feasibility of this option remains in a situation of balance.

Development of a pseudo-typed virus particle based method to determine the efficacy of virucidal agents

The ongoing Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic has highlighted the threat that viral outbreaks pose to global health. A key tool in the arsenal to prevent and control viral disease outbreaks is disinfection of equipment and surfaces with formulations that contain virucidal agents (VA). However, assessment of the efficacy of virus inactivation often requires live virus assays or surrogate viruses such as Modified Vaccinia Virus Ankara (MVA), which can be expensive, time consuming and technically challenging. Therefore, we have developed a pseudo-typed virus (PV) based approach to assess the inactivation of enveloped viruses with a fast and quantitative output that can be adapted to emerging viruses. Additionally, we have developed a method to completely remove the cytotoxicity of virucidal agents while retaining the required sensitivity to measure PV infectivity. Our results indicated that the removal of cytotoxicity was an essential step to accurately measure virus inactivation. Further, we demonstrated that there was no difference in susceptibility to virus inactivation between PVs that express the envelopes of HIV-1, SARS-CoV-2, and Influenza A/Indonesia. Therefore, we have developed an effective and safe alternative to live virus assays that enables the rapid assessment of virucidal activity for the development and optimization of virucidal reagents.

Ultrasensitive quantification of HIV-1 cell-to-cell transmission in primary human CD4+ T cells measures viral sensitivity to broadly neutralizing antibodies

IMPORTANCE

HIV-1 can efficiently transmit from one cell to another but accurate quantification of this mode of transmission is still challenging. Here, we developed an ultrasensitive assay to measure HIV-1 transmission between cells and to evaluate HIV-1 escape from broadly neutralizing antibodies in primary human T cells. This assay will contribute to understanding the fundamental mechanisms of HIV-1 cell-to-cell transmission, allow evaluation of pre-existing or acquired HIV-1 resistance in clinical trials, and can be adapted to study the biology of other retroviruses.

CRISPR/sgRNA-directed synergistic activation mediator (SAM) as a therapeutic tool for Parkinson´s disease

Parkinson`s disease (PD) is the second most prevalent neurodegenerative disease, and different gene therapy strategies have been used as experimental treatments. As a proof-of-concept for the treatment of PD, we used SAM, a CRISPR gene activation system, to activate the endogenous tyrosine hydroxylase gene (th) of astrocytes to produce dopamine (DA) in the striatum of 6-OHDA-lesioned rats. Potential sgRNAs within the rat th promoter region were tested, and the expression of the Th protein was determined in the C6 glial cell line. Employing pseudo-lentivirus, the SAM complex and the selected sgRNA were transferred into cultures of rat astrocytes, and gene expression and Th protein synthesis were ascertained; furthermore, DA release into the culture medium was determined by HPLC. The DA-producing astrocytes were implanted into the striatum of 6-OHDA hemiparkinsonian rats. We observed motor behavior improvement in the lesioned rats that received DA-astrocytes compared to lesioned rats receiving astrocytes that did not produce DA. Our data indicate that the SAM-induced expression of the astrocyte´s endogenous th gene can generate DA-producing astrocytes that effectively reduce the motor asymmetry induced by the lesion.

Exploring nutrient supplementation and bioprocess optimization to improve the production of lentiviral vectors in serum-free medium suspension cultures

The use of lentiviral vectors (LV) in gene therapy has been growing in recent years. To meet the increasing clinical demand, LV production platforms will benefit from improved productivity and scalability to enable cost-effective manufacture of LV-based therapies. Here we report the adaptation of 293T cells to serum-free suspension cultures and the improvement of LV yields through transfection parameters optimization, process intensification and medium supplementation with nutrient boosters. Cells were sequentially adapted to different serum-free culture media, transfection parameters were optimized and the two best-performing conditions were selected to explore process intensification by increasing cell density at the time of transfection. LV production at higher cell densities increased volumetric titers up to 12-fold and lipid supplementation was the most efficient metabolic optimization strategy further enhancing LV productivity by 3-fold. Furthermore, cell concentration was identified and validated as an important source of transfection variability impairing cellular uptake of DNA polyplexes, impacting transfection efficiency and reducing LV titers down to 6-fold. This work contributes to improving LV-based gene therapy by establishing new scalable manufacturing platforms and providing key metabolic insights, unveiling important bioreaction parameters to improve vector yields.

Pseudotyped zoonotic thogotoviruses exhibit broad entry range in mammalian cells

Viruses in the thogotovirus genus of the family Orthomyxoviridae are much less well-understood than influenza viruses despite documented zoonotic transmission and association with human disease. This study therefore developed a cell-cell fusion assay and three pseudotyping tools and used them to assess envelope function and cell tropism. Envelope glycoproteins of Dhori (DHOV), Thogoto (THOV), Bourbon, and Sinu viruses were all revealed to exhibit pH-dependent triggering of membrane fusion. Lentivirus vectors were robustly pseudotyped with these glycoproteins while influenza virus vectors showed pseudotyping compatibility, albeit at lower efficiencies. Replication-competent vesicular stomatitis virus expressing DHOV or THOV glycoproteins were also successfully generated. These pseudotyped viruses mediated entry into a wide range of mammalian cell lines, including human primary cells. The promiscuousness of these viruses suggests the use of a relatively ubiquitous receptor and their entry into numerous mammalian cells emphasize their high potential as veterinary and zoonotic diseases.

Third-generation lentiviral gene therapy rescues function in a mouse model of Usher 1B

Usher syndrome 1B (USH1B) is a devastating genetic disorder with congenital deafness, loss of balance, and blindness caused by mutations in the myosin-VIIa (MYO7A) gene, for which there is currently no cure. We developed a gene therapy approach addressing the vestibulo-cochlear deficits of USH1B using a third-generation, high-capacity lentiviral vector system capable of delivering the large 6,645-bp MYO7A cDNA. Lentivirally delivered MYO7A and co-encoded dTomato were successfully expressed in the cochlear cell line HEI-OC1. In normal-hearing mice, both cochlea and the vestibular organ were efficiently transduced, and ectopic MYO7A overexpression did not show any adverse effects. In Shaker-1 mice, an USH1B disease model based on Myo7a mutation, cochlear and vestibular hair cells, the main inner ear cell types affected in USH1B, were successfully transduced. In homozygous mutant mice, delivery of MYO7A at postnatal day 16 resulted in a trend for partial recovery of auditory function and in strongly reduced balance deficits. Heterozygous mutant mice were found to develop severe hearing loss at 6 months of age without balance deficits, and lentiviral MYO7A gene therapy completely rescued hearing to wild-type hearing thresholds. In summary, this study demonstrates improved hearing and balance function through lentiviral gene therapy in the inner ear.

Viral Vectors in Gene Replacement Therapy

Throughout the years, several hundred million people with rare genetic disorders have been receiving only symptom management therapy. However, research and development efforts worldwide have led to the development of long-lasting, highly efficient, and safe gene therapy for a wide range of hereditary diseases. Improved viral vectors are now able to evade the preexisting immunity and more efficiently target and transduce therapeutically relevant cells, ensuring genome maintenance and expression of transgenes at the relevant levels. Hematological, ophthalmological, neurodegenerative, and metabolic therapeutic areas have witnessed successful treatment of hemophilia and muscular dystrophy, restoration of immune system in children with immunodeficiencies, and restoration of vision. This review focuses on three leading vector platforms of the past two decades: adeno-associated viruses (AAVs), adenoviruses (AdVs), and lentiviruses (LVs). Special attention is given to successful preclinical and clinical studies that have led to the approval of gene therapies: six AAV-based (Glybera® for lipoprotein lipase deficiency, Luxturna® for retinal dystrophy, Zolgensma® for spinal muscular atrophy, Upstaza® for AADC, Roctavian® for hemophilia A, and Hemgenix® for hemophilia B) and three LV-based (Libmeldy® for infantile metachromatic leukodystrophy, Zynteglo® for β-thalassemia, and Skysona® for ALD). The review also discusses the problems that arise in the development of gene therapy treatments, which, nevertheless, do not overshadow the successes of already developed gene therapies and the hope these treatments give to long-suffering patients and their families.

Drug Delivery to the Brain: Recent Advances and Unmet Challenges

Brain cancers and neurodegenerative diseases are on the rise, treatments for central nervous system (CNS) diseases remain limited. Despite the significant advancement in drug development technology with emerging biopharmaceuticals like gene therapy or recombinant protein, the clinical translational rate of such biopharmaceuticals to treat CNS disease is extremely poor. The blood-brain barrier (BBB), which separates the brain from blood and protects the CNS microenvironment to maintain essential neuronal functions, poses the greatest challenge for CNS drug delivery. Many strategies have been developed over the years which include local disruption of BBB via physical and chemical methods, and drug transport across BBB via transcytosis by targeting some endogenous proteins expressed on brain-capillary. Drug delivery to brain is an ever-evolving topic, although there were multiple review articles in literature, an update is warranted due to continued growth and new innovations of research on this topic. Thus, this review is an attempt to highlight the recent strategies employed to overcome challenges of CNS drug delivery while emphasizing the necessity of investing more efforts in CNS drug delivery technologies parallel to drug development.

Malignancy-associated immune responses: Lessons from human inborn errors of immunity

It is widely understood that cancer is a significant cause of morbidity and mortality worldwide. Despite numerous available treatments, prognosis for many remains poor, thus, the development of novel therapies remains essential. Given the incredible success of many immunotherapies in this field, the important contribution of the immune system to the control, and elimination, of malignancy is clear. While many immunotherapies target higher-order pathways, for example, through promoting T-cell activation via immune checkpoint blockade, the potential to target specific immunological pathways is largely not well researched. Precisely understanding how immunity can be tailored to respond to specific challenges is an exciting idea with great potential, and may trigger the development of new therapies for cancer. Inborn Errors of Immunity (IEI) are a group of rare congenital disorders caused by gene mutations that result in immune dysregulation. This heterogeneous group, spanning widespread, multisystem immunopathology to specific immune cell defects, primarily manifest in immunodeficiency symptoms. Thus, these patients are particularly susceptible to life-threatening infection, autoimmunity and malignancy, making IEI an especially complex group of diseases. While precise mechanisms of IEI-induced malignancy have not yet been fully elucidated, analysis of these conditions can highlight the importance of particular genes, and downstream immune responses, in carcinogenesis and may help inform mechanisms which can be utilised in novel immunotherapies. In this review, we examine the links between IEIs and cancer, establishing potential connections between immune dysfunction and malignancy and suggesting roles for specific immunological mechanisms involved in preventing carcinogenesis, thus, guiding essential future research focused on cancer immunotherapy and providing valuable insight into the workings of the immune system in both health and disease.

Optimal delivery of RNA interference by viral vectors for cancer therapy

In recent years, there has been a surge in the innovative modification and application of the viral vector-based gene therapy field. Significant and consistent improvements in the engineering, delivery, and safety of viral vectors have set the stage for their application as RNA interference (RNAi) delivery tools. Viral vector-based delivery of RNAi has made remarkable breakthroughs in the treatment of several debilitating diseases and disorders (e.g., neurological diseases); however, their novelty has yet to be fully applied and utilized for the treatment of cancer. This review highlights the most promising and emerging viral vector delivery tools for RNAi therapeutics while discussing the variables limiting their success and suitability for cancer therapy. Specifically, we outline different integrating and non-integrating viral platforms used for gene delivery, currently employed RNAi targets for anti-cancer effect, and various strategies used to optimize the safety and efficacy of these RNAi therapeutics. Most importantly, we provide great insight into what challenges exist in their application as cancer therapeutics and how these challenges can be effectively navigated to advance the field.

Trans-Lesion Synthesis and Mismatch Repair Pathway Crosstalk Defines Chemoresistance and Hypermutation Mechanisms in Glioblastoma

Almost all Glioblastoma (GBM) are either intrinsically resistant to the chemotherapeutical drug temozolomide (TMZ) or acquire therapy-induced mutations that cause chemoresistance and recurrence. The genome maintenance mechanisms responsible for GBM chemoresistance and hypermutation are unknown. We show that the E3 ubiquitin ligase RAD18 (a proximal regulator of TLS) is activated in a Mismatch repair (MMR)-dependent manner in TMZ-treated GBM cells, promoting post-replicative gap-filling and survival. An unbiased CRISPR screen provides a new aerial map of RAD18-interacting DNA damage response (DDR) pathways deployed by GBM to tolerate TMZ genotoxicity. Analysis of mutation signatures from TMZ-treated GBM reveals a role for RAD18 in error-free bypass of O6mG (the most toxic TMZ-induced lesion), and error-prone bypass of other TMZ-induced lesions. Our analyses of recurrent GBM patient samples establishes a correlation between low RAD18 expression and hypermutation. Taken together we define novel molecular underpinnings for the hallmark tumorigenic phenotypes of TMZ-treated GBM.

Trans-Lesion Synthesis and Mismatch Repair Pathway Crosstalk Defines Chemoresistance and Hypermutation Mechanisms in Glioblastoma

Almost all Glioblastoma (GBM) are either intrinsically resistant to the chemotherapeutical drug temozolomide (TMZ) or acquire therapy-induced mutations that cause chemoresistance and recurrence. The genome maintenance mechanisms responsible for GBM chemoresistance and hypermutation are unknown. We show that the E3 ubiquitin ligase RAD18 (a proximal regulator of TLS) is activated in a Mismatch repair (MMR)-dependent manner in TMZ-treated GBM cells, promoting post-replicative gap-filling and survival. An unbiased CRISPR screen provides a new aerial map of RAD18-interacting DNA damage response (DDR) pathways deployed by GBM to tolerate TMZ genotoxicity. Analysis of mutation signatures from TMZ-treated GBM reveals a role for RAD18 in error-free bypass of O6mG (the most toxic TMZ-induced lesion), and error-prone bypass of other TMZ-induced lesions. Our analyses of recurrent GBM patient samples establishes a correlation between low RAD18 expression and hypermutation. Taken together we define novel molecular underpinnings for the hallmark tumorigenic phenotypes of TMZ-treated GBM.

Current avenues of gene therapy in Pompe disease

PURPOSE OF REVIEW

Pompe disease is a rare, inherited, devastating condition that causes progressive weakness, cardiomyopathy and neuromotor disease due to the accumulation of glycogen in striated and smooth muscle, as well as neurons. While enzyme replacement therapy has dramatically changed the outcome of patients with the disease, this strategy has several limitations. Gene therapy in Pompe disease constitutes an attractive approach due to the multisystem aspects of the disease and need to address the central nervous system manifestations. This review highlights the recent work in this field, including methods, progress, shortcomings, and future directions.

RECENT FINDINGS

Recombinant adeno-associated virus (rAAV) and lentiviral vectors (LV) are well studied platforms for gene therapy in Pompe disease. These products can be further adapted for safe and efficient administration with concomitant immunosuppression, with the modification of specific receptors or codon optimization. rAAV has been studied in multiple clinical trials demonstrating safety and tolerability.

SUMMARY

Gene therapy for the treatment of patients with Pompe disease is feasible and offers an opportunity to fully correct the principal pathology leading to cellular glycogen accumulation. Further work is needed to overcome the limitations related to vector production, immunologic reactions and redosing.

Packaging defects in pestiviral NS4A can be compensated by mutations in NS2 and NS3

The non-structural (NS) proteins of the Flaviviridae members play a dual role in genome replication and virion morphogenesis. For pestiviruses, like bovine viral diarrhea virus, the NS2-3 region and its processing by the NS2 autoprotease is of particular importance. While uncleaved NS2-3 in complex with NS4A is essential for virion assembly, it cannot replace free NS3/4A in the viral replicase. Furthermore, surface interactions between NS3 and the C-terminal cytosolic domain of NS4A were shown to serve as a molecular switch between RNA replication and virion morphogenesis. To further characterize the functionality of NS4A, we performed an alanine-scanning mutagenesis of two NS4A regions, a short highly conserved cytoplasmic linker downstream of the transmembrane domain and the C-terminal domain. NS4A residues critical for polyprotein processing, RNA replication, and/or virion morphogenesis were identified. Three double-alanine mutants, two in the linker region and one close to the C-terminus of NS4A, showed a selective effect on virion assembly. All three packaging defective mutants could be rescued by a selected set of two second-site mutations, located in NS2 and NS3, respectively. This phenotype was additionally confirmed by complementation studies providing the NS2-3/4A packaging molecules containing the rescue mutations in trans. This indicates that the linker region and the cytosolic C-terminal part of NS4A are critical for the formation of protein complexes required for virion morphogenesis. The ability of the identified sets of second-site mutations in NS2-3 to compensate for diverse NS4A defects highlights a surprising functional flexibility for pestiviral NS proteins. IMPORTANCE Positive-strand RNA viruses have a limited coding capacity due to their rather small genome size. To overcome this constraint, viral proteins often exhibit multiple functions that come into play at different stages during the viral replication cycle. The molecular basis for this multifunctionality is often unknown. For the bovine viral diarrhea virus, the non-structural protein (NS) 4A functions as an NS3 protease cofactor, a replicase building block, and a component in virion morphogenesis. Here, we identified the critical amino acids of its C-terminal cytosolic region involved in those processes and show that second-site mutations in NS2 and NS3 can compensate for diverse NS4A defects in virion morphogenesis. The ability to evolve alternative functional solutions by gain-of-function mutations highlights the astounding plasticity of the pestiviral system.

A lentiviral vector for the production of T cells with an inducible transgene and a constitutively expressed tumour-targeting receptor

Vectors that facilitate the engineering of T cells that can better harness endogenous immunity and overcome suppressive barriers in the tumour microenvironment would help improve the safety and efficacy of T-cell therapies for more patients. Here we report the design, production and applicability, in T-cell engineering, of a lentiviral vector leveraging an antisense configuration and comprising a promoter driving the constitutive expression of a tumour-directed receptor and a second promoter enabling the efficient activation-inducible expression of a genetic payload. The vector allows for the delivery of a variety of genes to human T cells, as we show for interleukin-2 and a microRNA-based short hairpin RNA for the knockdown of the gene coding for haematopoietic progenitor kinase 1, a negative regulator of T-cell-receptor signalling. We also show that a gene encoded under an activation-inducible promoter is specifically expressed by tumour-redirected T cells on encountering a target antigen in the tumour microenvironment. The single two-gene-encoding vector can be produced at high titres under an optimized protocol adaptable to good manufacturing practices.

Development of a perfusion process for continuous lentivirus production using stable suspension producer cell lines

The large-scale production of clinical-grade lentiviral vectors (LVs) for gene therapy applications is a remaining challenge. The use of adherent cell lines and methods like transient transfection are cost-intensive and hamper process scalability as well as reproducibility. This study describes the use of two suspension-adapted stable packaging cell lines, called GPRGs and GPRTGs, for the development of a scalable and serum-free LV production process. Both stable packaging cell lines are based on an inducible Tet-off system, thus requiring doxycycline removal for initiation of the virus production. Therefore, we compared different methods for doxycycline removal and inoculated three independent 5 L bioreactors using a scalable induction method by dilution, an acoustic cell washer and manual centrifugation. The bioreactors were inoculated with a stable producer cell line encoding for a LV carrying a clinically relevant gene. LV production was performed in perfusion mode using a cell retention device based on acoustic wave separation. Comparable cell-specific productivities were obtained with all three methods and cumulative functional yields up to 6.36 × 1011 transducing units per bioreactor were generated in a 234-h long process, demonstrating the usability of stable Tet-off cell lines for an easily scalable suspension process. Remarkably, cell viabilities >90% were maintained at high cell densities without compromising productivity throughout the whole process, allowing to further extend the process time. Given its low effects of toxicity during virus production, the presented cell lines are excellent candidates to develop a fully continuous LV production process to overcome the existing bottlenecks in LV manufacturing.

Beta-subunit-eliminated eHAP expression (BeHAPe) cells reveal subunit regulation of the cardiac voltage-gated sodium channel

Voltage-gated sodium (NaV) channels drive the upstroke of the action potential and are comprised of a pore-forming α-subunit and regulatory β-subunits. The β-subunits modulate the gating, trafficking, and pharmacology of the α-subunit. These functions are routinely assessed by ectopic expression in heterologous cells. However, currently available expression systems may not capture the full range of these effects since they contain endogenous β-subunits. To better reveal β-subunit functions, we engineered a human cell line devoid of endogenous NaV β-subunits and their immediate phylogenetic relatives. This new cell line, β-subunit-eliminated eHAP expression (BeHAPe) cells, were derived from haploid eHAP cells by engineering inactivating mutations in the β-subunits SCN1B, SCN2B, SCN3B, and SCN4B, and other subfamily members MPZ (myelin protein zero(P0)), MPZL1, MPZL2, MPZL3, and JAML. In diploid BeHAPe cells, the cardiac NaV α-subunit, NaV1.5, was highly sensitive to β-subunit modulation and revealed that each β-subunit and even MPZ imparted unique gating properties. Furthermore, combining β1 and β2 with NaV1.5 generated a sodium channel with hybrid properties, distinct from the effects of the individual subunits. Thus, this approach revealed an expanded ability of β-subunits to regulate NaV1.5 activity and can be used to improve the characterization of other α/β NaV complexes.

The negative adipogenesis regulator Dlk1 is transcriptionally regulated by Ifrd1 (TIS7) and translationally by its orthologue Ifrd2 (SKMc15)

Delta-like homolog 1 (Dlk1), an inhibitor of adipogenesis, controls the cell fate of adipocyte progenitors. Experimental data presented here identify two independent regulatory mechanisms, transcriptional and translational, by which Ifrd1 (TIS7) and its orthologue Ifrd2 (SKMc15) regulate Dlk1 levels. Mice deficient in both Ifrd1 and Ifrd2 (dKO) had severely reduced adipose tissue and were resistant to high-fat diet-induced obesity. Wnt signaling, a negative regulator of adipocyte differentiation, was significantly upregulated in dKO mice. Elevated levels of the Wnt/β-catenin target protein Dlk1 inhibited the expression of adipogenesis regulators Pparg and Cebpa, and fatty acid transporter Cd36. Although both Ifrd1 and Ifrd2 contributed to this phenotype, they utilized two different mechanisms. Ifrd1 acted by controlling Wnt signaling and thereby transcriptional regulation of Dlk1. On the other hand, distinctive experimental evidence showed that Ifrd2 acts as a general translational inhibitor significantly affecting Dlk1 protein levels. Novel mechanisms of Dlk1 regulation in adipocyte differentiation involving Ifrd1 and Ifrd2 are based on experimental data presented here.

TGFβ Inhibitor A83-01 Enhances Murine HSPC Expansion for Gene Therapy

Murine hematopoietic stem and progenitor cells (HSPCs) are commonly used as model systems during gene therapeutic retroviral vector development and preclinical biosafety assessment. Here, we developed cell culture conditions to maintain stemness and prevent differentiation during HSPC culture. We used the small compounds A83-01, pomalidomide, and UM171 (APU). Highly purified LSK SLAM cells expanded in medium containing SCF, IL-3, FLT3-L, and IL-11 but rapidly differentiated to myeloid progenitors and mast cells. The supplementation of APU attenuated the differentiation and preserved the stemness of HSPCs. The TGFβ inhibitor A83-01 was identified as the major effector. It significantly inhibited the mast-cell-associated expression of FcεR1α and the transcription of genes regulating the formation of granules and promoted a 3800-fold expansion of LSK cells. As a functional readout, we used expanded HSPCs in state-of-the-art genotoxicity assays. Like fresh cells, APU-expanded HSPCs transduced with a mutagenic retroviral vector developed a myeloid differentiation block with clonal restriction and dysregulated oncogenic transcriptomic signatures due to vector integration near the high-risk locus Mecom. Thus, expanded HSPCs might serve as a novel cell source for retroviral vector testing and genotoxicity studies.

Increase in SARS-CoV-2 Seroprevalence in UK Domestic Felids Despite Weak Immunogenicity of Post-Omicron Variants

Throughout the COVID-19 pandemic, SARS-CoV-2 infections in domestic cats have caused concern for both animal health and the potential for inter-species transmission. Cats are known to be susceptible to the Omicron variant and its descendants, however, the feline immune response to these variants is not well defined. We aimed to estimate the current seroprevalence of SARS-CoV-2 in UK pet cats, as well as characterise the neutralising antibody response to the Omicron (BA.1) variant. A neutralising seroprevalence of 4.4% and an overall seroprevalence of 13.9% was observed. Both purebred and male cats were found to have the highest levels of seroprevalence, as well as cats aged between two and five years. The Omicron variant was found to have a lower immunogenicity in cats than the B.1, Alpha and Delta variants, which reflects previous reports of immune and vaccine evasion in humans. These results further underline the importance of surveillance of SARS-CoV-2 infections in UK cats as the virus continues to evolve.

Mapping the neutralizing specificity of human anti-HIV serum by deep mutational scanning

Understanding the specificities of human serum antibodies that broadly neutralize HIV can inform prevention and treatment strategies. Here, we describe a deep mutational scanning system that can measure the effects of combinations of mutations to HIV envelope (Env) on neutralization by antibodies and polyclonal serum. We first show that this system can accurately map how all functionally tolerated mutations to Env affect neutralization by monoclonal antibodies. We then comprehensively map Env mutations that affect neutralization by a set of human polyclonal sera that neutralize diverse strains of HIV and target the site engaging the host receptor CD4. The neutralizing activities of these sera target different epitopes, with most sera having specificities reminiscent of individual characterized monoclonal antibodies, but one serum targeting two epitopes within the CD4-binding site. Mapping the specificity of the neutralizing activity in polyclonal human serum will aid in assessing anti-HIV immune responses to inform prevention strategies.

SLC5A1 Variants in Turkish Patients with Congenital Glucose-Galactose Malabsorption

Congenital glucose-galactose malabsorption is a rare autosomal recessive disorder caused by mutations in SLC5A1 encoding the apical sodium/glucose cotransporter SGLT1. We present clinical and molecular data from eleven affected individuals with congenital glucose-galactose malabsorption from four unrelated, consanguineous Turkish families. Early recognition and timely management by eliminating glucose and galactose from the diet are fundamental for affected individuals to survive and develop normally. We identified novel SLC5A1 missense variants, p.Gly43Arg and p.Ala92Val, which were linked to disease in two families. Stable expression in CaCo-2 cells showed that the p.Ala92Val variant did not reach the plasma membrane, but was retained in the endoplasmic reticulum. The p.Gly43Arg variant, however, displayed processing and plasma membrane localization comparable to wild-type SGLT1. Glycine-43 displays nearly invariant conservation in the relevant structural family of cotransporters and exchangers, and localizes to SGLT1 transmembrane domain TM0. p.Gly43Arg represents the first disease-associated variant in TM0; however, the role of TM0 in the SGLT1 function has not been established. In summary, we are expanding the mutational spectrum of this rare disorder.

Challenges in HIV-1 Latent Reservoir and Target Cell Quantification in CAR-T Cell and Other Lentiviral Gene Modifying HIV Cure Strategies

Gene-modification therapies are at the forefront of HIV-1 cure strategies. Chimeric antigen receptor (CAR)-T cells pose a potential approach to target infected cells during antiretroviral therapy or following analytical treatment interruption (ATI). However, there are technical challenges in the quantification of HIV-1-infected and CAR-T cells in the setting of lentiviral CAR gene delivery and also in the identification of cells expressing target antigens. First, there is a lack of validated techniques to identify and characterize cells expressing the hypervariable HIV gp120 in both ART-suppressed and viremic individuals. Second, close sequence homology between lentiviral-based CAR-T gene modification vectors and conserved regions of HIV-1 creates quantification challenges of HIV-1 and lentiviral vector levels. Consideration needs to be taken into standardizing HIV-1 DNA/RNA assays in the setting of CAR-T cell and other lentiviral vector-based therapies to avoid these confounding interactions. Lastly, with the introduction of HIV-1 resistance genes in CAR-T cells, there is a need for assays with single-cell resolution to determine the competence of the gene inserts to prevent CAR-T cells from becoming infected in vivo. As novel therapies continue to arise in the HIV-1 cure field, resolving these challenges in CAR-T-cell therapy will be crucial.

Cementum protein 1 gene-modified adipose-derived mesenchymal stem cell sheets enhance periodontal regeneration in osteoporosis rat

BACKGROUND AND OBJECTIVES

Osteoporosis (OP) and periodontitis are both diseases with excessive bone resorption, and the number of patients who suffer from these diseases is expected to increase. OP has been identified as a risk factor that accelerates the pathological process of periodontitis. Achieving effective and safe periodontal regeneration in OP patients is a meaningful challenge. This study aimed to assess the efficacy and biosecurity of human cementum protein 1 (hCEMP1) gene-modified cell sheets for periodontal fenestration defect regeneration in an OP rat model.

MATERIALS AND METHODS

Rat adipose-derived mesenchymal stem cells (rADSCs) were isolated from Sprague-Dawley rats. After primary culture, rADSCs were subjected to cell surface analysis and multi-differentiation assay. And rADSCs were transduced with hCEMP1 by lentiviral vector, and hCEMP1 gene-modified cell sheets were generated. The expression of hCEMP1 was evaluated by reverse transcription polymerase chain reaction and immunocytochemistry staining, and transduced cell proliferation was evaluated by Cell Counting Kit-8. The hCEMP1 gene-modified cell sheet structure was detected by histological analysis and scanning electron microscopy. Osteogenic and cementogenic-associated gene expression was evaluated by real-time quantitative polymerase chain reaction. In addition, an OP rat periodontal fenestration defect model was used to evaluate the regeneration effect of hCEMP1 gene-modified rADSC sheets. The efficacy was assessed with microcomputed tomography and histology, and the biosecurity of gene-modified cell sheets was evaluated by histological analysis of the spleen, liver, kidney and lung.

RESULTS

The rADSCs showed a phenotype of mesenchymal stem cells and possessed multi-differentiation capacity. The gene and protein expression of hCEMP1 through lentiviral transduction was confirmed, and there was no significant effect on rADSC proliferation. Overexpression of hCEMP1 upregulated osteogenic and cementogenic-related genes such as runt-related transcription factor 2, bone morphogenetic protein 2, secreted phosphoprotein 1 and cementum attachment protein in the gene-modified cell sheets. The fenestration lesions in OP rats treated with hCEMP1 gene-modified cell sheets exhibited complete bone bridging, cementum and periodontal ligament formation. Furthermore, histological sections of the spleen, liver, kidney and lung showed no evident pathological damage.

CONCLUSION

This pilot study demonstrates that hCEMP1 gene-modified rADSC sheets have a marked ability to enhance periodontal regeneration in OP rats. Thus, this approach may represent an effective and safe strategy for periodontal disease patients with OP.

Genetic engineering meets hematopoietic stem cell biology for next-generation gene therapy

The growing clinical success of hematopoietic stem/progenitor cell (HSPC) gene therapy (GT) relies on the development of viral vectors as portable "Trojan horses" for safe and efficient gene transfer. The recent advent of novel technologies enabling site-specific gene editing is broadening the scope and means of GT, paving the way to more precise genetic engineering and expanding the spectrum of diseases amenable to HSPC-GT. Here, we provide an overview of state-of-the-art and prospective developments of the HSPC-GT field, highlighting how advances in biological characterization and manipulation of HSPCs will enable the design of the next generation of these transforming therapeutics.

Gene-based delivery of immune-activating cytokines for cancer treatment

Tumors evolve together with the tumor microenvironment (TME) and reshape it towards immunosuppression. Immunostimulating cytokines can be used to revert this state leading to effective antitumor immune responses, but their exploitation as anticancer drugs has been hampered by severe toxicity associated with systemic administration. Local, TME-targeted delivery of immune activating cytokines can deploy their antitumoral function more effectively than systemic administration while, at the same time, avoiding exposure of healthy organs and limiting toxicity. Here, we review different gene and cell therapy platforms developed for tumor-directed cytokine delivery highlighting their potential for clinical translation.

Mapping the neutralizing specificity of human anti-HIV serum by deep mutational scanning

Understanding the specificities of human serum antibodies that broadly neutralize HIV can inform prevention and treatment strategies. Here we describe a deep mutational scanning system that can measure the effects of combinations of mutations to HIV envelope (Env) on neutralization by antibodies and polyclonal serum. We first show that this system can accurately map how all functionally tolerated mutations to Env affect neutralization by monoclonal antibodies. We then comprehensively map Env mutations that affect neutralization by a set of human polyclonal sera known to target the CD4-binding site that neutralize diverse strains of HIV. The neutralizing activities of these sera target different epitopes, with most sera having specificities reminiscent of individual characterized monoclonal antibodies, but one sera targeting two epitopes within the CD4 binding site. Mapping the specificity of the neutralizing activity in polyclonal human serum will aid in assessing anti-HIV immune responses to inform prevention strategies.

Gene therapy strategies for glaucoma from IOP reduction to retinal neuroprotection: progress towards non-viral systems

Glaucoma is the result of the gradual death of retinal ganglion cells (RGCs) whose axons form the optic nerve. Elevated intraocular pressure (IOP) is a major risk factors thatcontributes to RGC apoptosis and axonal loss at the lamina cribrosa, resulting in progressive reduction and eventual anterograde-retrograde transport blockade of neurotrophic factors. Current glaucoma management mainly focuses on pharmacological or surgical lowering of IOP, to manage the only modifiable risk factor. Although IOP reduction delays disease progression, it does not address previous and ongoing optic nerve degeneration. Gene therapy is a promising direction to control or modify genes involved in the pathophysiology of glaucoma. Both viral and non-viral gene therapy delivery systems are emerging as promising alternatives or add-on therapies to traditional treatments for improving IOP control and provide neuroprotection. The specific spotlight on non-viral gene delivery systems shows further progress towards improving the safety of gene therapy and implementing neuroprotection by targeting specific tissues and cells in the eye and specifically in the retina.

A pseudovirus system enables deep mutational scanning of the full SARS-CoV-2 spike

A major challenge in understanding SARS-CoV-2 evolution is interpreting the antigenic and functional effects of emerging mutations in the viral spike protein. Here, we describe a deep mutational scanning platform based on non-replicative pseudotyped lentiviruses that directly quantifies how large numbers of spike mutations impact antibody neutralization and pseudovirus infection. We apply this platform to produce libraries of the Omicron BA.1 and Delta spikes. These libraries each contain ∼7,000 distinct amino acid mutations in the context of up to ∼135,000 unique mutation combinations. We use these libraries to map escape mutations from neutralizing antibodies targeting the receptor-binding domain, N-terminal domain, and S2 subunit of spike. Overall, this work establishes a high-throughput and safe approach to measure how ∼105 combinations of mutations affect antibody neutralization and spike-mediated infection. Notably, the platform described here can be extended to the entry proteins of many other viruses.

High-capacity adenovector delivery of forced CRISPR-Cas9 heterodimers fosters precise chromosomal deletions in human cells

Genome editing based on dual CRISPR-Cas9 complexes (multiplexes) permits removing specific genomic sequences in living cells leveraging research on functional genomics and genetic therapies. Delivering the required large and multicomponent reagents in a synchronous and stoichiometric manner remains, however, challenging. Moreover, uncoordinated activity of independently acting CRISPR-Cas9 multiplexes increases the complexity of genome editing outcomes. Here, we investigate the potential of fostering precise multiplexing genome editing using high-capacity adenovector particles (AdVPs) for the delivery of Cas9 ortholog fusion constructs alone (forced Cas9 heterodimers) or together with their cognate guide RNAs (forced CRISPR-Cas9 heterodimers). We demonstrate that the efficiency and accuracy of targeted chromosomal DNA deletions achieved by single AdVPs encoding forced CRISPR-Cas9 heterodimers is superior to that obtained when the various components are delivered separately. Finally, all-in-one AdVP delivery of forced CRISPR-Cas9 heterodimers triggers robust DMD exon 51 splice site excision resulting in reading frame restoration and selection-free detection of dystrophin in muscle cells derived from Duchenne muscular dystrophy patients. In conclusion, AdVPs promote precise multiplexing genome editing through the integrated delivery of forced CRISPR-Cas9 heterodimer components, which, in comparison with split conventional CRISPR-Cas9 multiplexes, engage target sequences in a more coordinated fashion.

Novel scFv against Notch Ligand JAG1 Suitable for Development of Cell Therapies toward JAG1-Positive Tumors

The Notch signaling ligand JAG1 is overexpressed in various aggressive tumors and is associated with poor clinical prognosis. Hence, therapies targeting oncogenic JAG1 hold great potential for the treatment of certain tumors. Here, we report the identification of specific anti-JAG1 single-chain variable fragments (scFvs), one of them endowing chimeric antigen receptor (CAR) T cells with cytotoxicity against JAG1-positive cells. Anti-JAG1 scFvs were identified from human phage display libraries, reformatted into full-length monoclonal antibodies (Abs), and produced in mammalian cells. The characterization of these Abs identified two specific anti-JAG1 Abs (J1.B5 and J1.F1) with nanomolar affinities. Cloning the respective scFv sequences in our second- and third-generation CAR backbones resulted in six anti-JAG1 CAR constructs, which were screened for JAG1-mediated T-cell activation in Jurkat T cells in coculture assays with JAG1-positive cell lines. Studies in primary T cells demonstrated that one CAR harboring the J1.B5 scFv significantly induced effective T-cell activation in the presence of JAG1-positive, but not in JAG1-knockout, cancer cells, and enabled specific killing of JAG1-positive cells. Thus, this new anti-JAG1 scFv represents a promising candidate for the development of cell therapies against JAG1-positive tumors.

Delivery challenges for CRISPR-Cas9 genome editing for Duchenne muscular dystrophy

Duchene muscular dystrophy (DMD) is an X-linked neuromuscular disorder that affects about one in every 5000 live male births. DMD is caused by mutations in the gene that codes for dystrophin, which is required for muscle membrane stabilization. The loss of functional dystrophin causes muscle degradation that leads to weakness, loss of ambulation, cardiac and respiratory complications, and eventually, premature death. Therapies to treat DMD have advanced in the past decade, with treatments in clinical trials and four exon-skipping drugs receiving conditional Food and Drug Administration approval. However, to date, no treatment has provided long-term correction. Gene editing has emerged as a promising approach to treating DMD. There is a wide range of tools, including meganucleases, zinc finger nucleases, transcription activator-like effector nucleases, and, most notably, RNA-guided enzymes from the bacterial adaptive immune system clustered regularly interspaced short palindromic repeats (CRISPR). Although challenges in using CRISPR for gene therapy in humans still abound, including safety and efficiency of delivery, the future for CRISPR gene editing for DMD is promising. This review will summarize the progress in CRISPR gene editing for DMD including key summaries of current approaches, delivery methodologies, and the challenges that gene editing still faces as well as prospective solutions.

Correcting inborn errors of immunity: From viral mediated gene addition to gene editing

Allogeneic hematopoietic stem cell transplantation is an effective treatment to cure inborn errors of immunity. Remarkable progress has been achieved thanks to the development and optimization of effective combination of advanced conditioning regimens and use of immunoablative/suppressive agents preventing rejection as well as graft versus host disease. Despite these tremendous advances, autologous hematopoietic stem/progenitor cell therapy based on ex vivo gene addition exploiting integrating γ-retro- or lenti-viral vectors, has demonstrated to be an innovative and safe therapeutic strategy providing proof of correction without the complications of the allogeneic approach. The recent advent of targeted gene editing able to precisely correct genomic variants in an intended locus of the genome, by introducing deletions, insertions, nucleotide substitutions or introducing a corrective cassette, is emerging in the clinical setting, further extending the therapeutic armamentarium and offering a cure to inherited immune defects not approachable by conventional gene addition. In this review, we will analyze the current state-of-the art of conventional gene therapy and innovative protocols of genome editing in various primary immunodeficiencies, describing preclinical models and clinical data obtained from different trials, highlighting potential advantages and limits of gene correction.

Potentiation of Lipotoxicity in Human EndoC-βH1 β-Cells by Glucose is Dependent on the Structure of Free Fatty Acids

SCOPE

Lipotoxicity is a significant element in the development of type 2 diabetes mellitus (T2DM). Since pro-diabetic nutritional patterns are associated with hyperglycemia as well as hyperlipidemia, the study analyzes the effects of combining these lipid and carbohydrate components with a special focus on the structural fatty acid properties such as increasing chain length (C16-C20) and degree of saturation with regard to the role of glucolipotoxicity in human EndoC-βH1 β-cells.

METHODS AND RESULTS

β-cell death induced by saturated FFAs is potentiated by high concentrations of glucose in a chain length-dependent manner starting with stearic acid (C18:0), whereas toxicity remains unchanged in the case of monounsaturated FFAs. Interference with FFA desaturation by overexpression and inhibition of stearoyl-CoA-desaturase, which catalyzes the rate-limiting step in the conversion of long-chain saturated into corresponding monounsaturated FFAs, does not affect the potentiating effect of glucose, but FFA desaturation reduces lipotoxicity and plays an important role in the formation of lipid droplets. Crucial elements underlying glucolipotoxicity are ER stress induction and cardiolipin peroxidation in the mitochondria.

CONCLUSION

In the context of nutrition, the data emphasize the importance of the lipid component in glucolipotoxicity related to the development of β-cell dysfunction and death in the manifestation of T2DM.

VelcroVax: a "Bolt-On" Vaccine Platform for Glycoprotein Display

Having varied approaches to the design and manufacture of vaccines is critical in being able to respond to worldwide needs and newly emerging pathogens. Virus-like particles (VLPs) form the basis of two of the most successful licensed vaccines (against hepatitis B virus [HBV] and human papillomavirus). They are produced by recombinant expression of viral structural proteins, which assemble into immunogenic nanoparticles. VLPs can be modified to present unrelated antigens, and here we describe a universal "bolt-on" platform (termed VelcroVax) where the capturing VLP and the target antigen are produced separately. We utilize a modified HBV core (HBcAg) VLP with surface expression of a high-affinity binding sequence (Affimer) directed against a SUMO tag and use this to capture SUMO-tagged gp1 glycoprotein from the arenavirus Junín virus (JUNV). Using this model system, we have solved the first high-resolution structures of VelcroVax VLPs and shown that the VelcroVax-JUNV gp1 complex induces superior humoral immune responses compared to the noncomplexed viral protein. We propose that this system could be modified to present a range of antigens and therefore form the foundation of future rapid-response vaccination strategies. IMPORTANCE The hepatitis B core protein (HBc) forms noninfectious virus-like particles, which can be modified to present a capturing molecule, allowing suitably tagged antigens to be bound on their surface. This system can be adapted and provides the foundation for a universal "bolt-on" vaccine platform (termed VelcroVax) that can be easily and rapidly modified to generate nanoparticle vaccine candidates.

Artificial extracellular matrix scaffolds of mobile molecules enhance maturation of human stem cell-derived neurons

Human induced pluripotent stem cell (hiPSC) technologies offer a unique resource for modeling neurological diseases. However, iPSC models are fraught with technical limitations including abnormal aggregation and inefficient maturation of differentiated neurons. These problems are in part due to the absence of synergistic cues of the native extracellular matrix (ECM). We report on the use of three artificial ECMs based on peptide amphiphile (PA) supramolecular nanofibers. All nanofibers display the laminin-derived IKVAV signal on their surface but differ in the nature of their non-bioactive domains. We find that nanofibers with greater intensity of internal supramolecular motion have enhanced bioactivity toward hiPSC-derived motor and cortical neurons. Proteomic, biochemical, and functional assays reveal that highly mobile PA scaffolds caused enhanced β1-integrin pathway activation, reduced aggregation, increased arborization, and matured electrophysiological activity of neurons. Our work highlights the importance of designing biomimetic ECMs to study the development, function, and dysfunction of human neurons.