Gene therapy: progress and predictions

Bioreversible Anionic Cloaking Enables Intracellular Protein Delivery with Ionizable Lipid Nanoparticles

Protein-based therapeutics comprise a rapidly growing subset of pharmaceuticals, but enabling their delivery into cells for intracellular applications has been a longstanding challenge. To overcome the delivery barrier, we explored a reversible, bioconjugation-based approach to modify the surface charge of protein cargos with an anionic "cloak" to facilitate electrostatic complexation and delivery with lipid nanoparticle (LNP) formulations. We demonstrate that the conjugation of lysine-reactive sulfonated compounds can allow for the delivery of various protein cargos using FDA-approved LNP formulations of the ionizable cationic lipid DLin-MC3-DMA (MC3). We apply this strategy to functionally deliver RNase A for cancer cell killing as well as a full-length antibody to inhibit oncogenic β-catenin signaling. Further, we show that LNPs encapsulating cloaked fluorescent proteins distribute to major organs in mice following systemic administration. Overall, our results point toward a generalizable platform that can be employed for intracellular delivery of a wide range of protein cargos.

Exploring modified chitosan-based gene delivery technologies for therapeutic advancements

One of the critical steps in gene therapy is the successful delivery of the genes. Immunogenicity and toxicity are major issues for viral gene delivery systems. Thus, non-viral vectors are explored. A cationic polysaccharide like chitosan could be used as a nonviral gene delivery vector owing to its significant interaction with negatively charged nucleic acid and biomembrane, providing effective cellular uptake. However, the native chitosan has issues of targetability, unpacking ability, and solubility along with poor buffer capability, hence requiring modifications for effective use in gene delivery. Modified chitosan has shown that the "proton sponge effect" involved in buffering the endosomal pH results in osmotic swelling owing to the accumulation of a greater amount of proton and chloride along with water. The major challenges include limited exploration of chitosan as a gene carrier, the availability of high-purity chitosan for toxicity reduction, and its immunogenicity. The genetic drugs are in their infancy phase and require further exploration for effective delivery of nucleic acid molecules as FDA-approved marketed formulations soon.

Deep Learning-Predicted Dihydroartemisinin Rescues Osteoporosis by Maintaining Mesenchymal Stem Cell Stemness through Activating Histone 3 Lys 9 Acetylation

Maintaining the stemness of bone marrow mesenchymal stem cells (BMMSCs) is crucial for bone homeostasis and regeneration. However, in vitro expansion and bone diseases impair BMMSC stemness, limiting its functionality in bone tissue engineering. Using a deep learning-based efficacy prediction system and bone tissue sequencing, we identify a natural small-molecule compound, dihydroartemisinin (DHA), that maintains BMMSC stemness and enhances bone regeneration. During long-term in vitro expansion, DHA preserves BMMSC stemness characteristics, including its self-renewal ability and unbiased differentiation. In an osteoporosis mouse model, oral administration of DHA restores the femur trabecular structure, bone density, and BMMSC stemness in situ. Mechanistically, DHA maintains BMMSC stemness by promoting histone 3 lysine 9 acetylation via GCN5 activation both in vivo and in vitro. Furthermore, the bone-targeted delivery of DHA by mesoporous silica nanoparticles improves its therapeutic efficacy in osteoporosis. Collectively, DHA could be a promising therapeutic agent for treating osteoporosis by maintaining BMMSC stemness.

Local Delivery of Immunomodulatory Antibodies for Gastrointestinal Tumors

Cancer therapy has experienced a breakthrough with the use of immune checkpoint inhibitors (ICIs) based on monoclonal antibodies (mAbs), which are able to unleash immune responses against tumors refractory to other therapies. Despite the great advancement that ICIs represent, most patients with gastrointestinal tumors have not benefited from this therapy. In addition, ICIs often induce adverse effects that are related to their systemic use. Local administration of ICIs in tumors could concentrate their effect in the malignant tissue and provide a higher safety profile. A new and attractive approach for local delivery of ICIs is the use of gene therapy vectors to express these blocking antibodies in tumor cells. Several vectors have been evaluated in preclinical models of gastrointestinal tumors to express ICIs against PD-1, PD-L1, and CTLA-4, among other immune checkpoints, with promising results. Vectors used in these settings include oncolytic viruses, self-replicating RNA vectors, and non-replicative viral and non-viral vectors. The use of viral vectors, especially when they have replication capacity, provides an additional adjuvant effect that has been shown to enhance antitumor responses. This review covers the most recent studies involving the use of gene therapy vectors to deliver ICIs to gastrointestinal tumors.

Enhancing the expression of a key mitochondrial enzyme at the inception of ischemia-reperfusion injury can boost recovery and halt the progression of acute kidney injury

Hydrodynamic fluid delivery has shown promise in influencing renal function in disease models. This technique provided pre-conditioned protection in acute injury models by upregulating the mitochondrial adaptation, while hydrodynamic injections of saline alone have improved microvascular perfusion. Accordingly, hydrodynamic mitochondrial gene delivery was applied to investigate the ability to halt progressive or persistent renal function impairment following episodes of ischemia-reperfusion injuries known to induce acute kidney injury (AKI). The rate of transgene expression was approximately 33% and 30% in rats with prerenal AKI that received treatments 1 (T1hr) and 24 (T24hr) hours after the injury was established, respectively. The resulting mitochondrial adaptation via exogenous IDH2 (isocitrate dehydrogenase 2 (NADP+) and mitochondrial) significantly blunted the effects of injury within 24 h of administration: decreased serum creatinine (≈60%, p < 0.05 at T1hr; ≈50%, p < 0.05 at T24hr) and blood urea nitrogen (≈50%, p < 0.05 at T1hr; ≈35%, p < 0.05 at T24hr) levels, and increased urine output (≈40%, p < 0.05 at T1hr; ≈26%, p < 0.05 at T24hr) and mitochondrial membrane potential, Δψm, (≈ by a factor of 13, p < 0.001 at T1hr; ≈ by a factor of 11, p < 0.001 at T24hr), despite elevated histology injury score (26%, p < 0.05 at T1hr; 47%, p < 0.05 at T24hr). Therefore, this study identifies an approach that can boost recovery and halt the progression of AKI at its inception.

Structure and Function of Cationic and Ionizable Lipids for Nucleic Acid Delivery

Hereditary genetic diseases, cancer, and infectious diseases are affecting global health and become major health issues, but the treatment development remains challenging. Gene therapies using DNA plasmid, RNAi, miRNA, mRNA, and gene editing hold great promise. Lipid nanoparticle (LNP) delivery technology has been a revolutionary development, which has been granted for clinical applications, including mRNA vaccines against SARS-CoV-2 infections. Due to the success of LNP systems, understanding the structure, formulation, and function relationship of the lipid components in LNP systems is crucial for design more effective LNP. Here, we highlight the key considerations for developing an LNP system. The evolution of structure and function of lipids as well as their LNP formulation from the early-stage simple formulations to multi-components LNP and multifunctional ionizable lipids have been discussed. The flexibility and platform nature of LNP enable efficient intracellular delivery of a variety of therapeutic nucleic acids and provide many novel treatment options for the diseases that are previously untreatable.

Digital Technologies: Advancing Individualized Treatments through Gene and Cell Therapies, Pharmacogenetics, and Disease Detection and Diagnostics

Digital technologies are shifting the paradigm of medicine in a way that will transform the healthcare industry. Conventional medical approaches focus on treating symptoms and ailments for large groups of people. These approaches can elicit differences in treatment responses and adverse reactions based on population variations, and are often incapable of treating the inherent pathophysiology of the medical conditions. Advances in genetics and engineering are improving healthcare via individualized treatments that include gene and cell therapies, pharmacogenetics, disease detection, and diagnostics. This paper highlights ways that artificial intelligence can help usher in an age of personalized medicine.

Tumor microenvironment responsive nanocarriers for gene therapy

Stimuli responsive nanocarriers are important non-viral gene carriers for gene therapy. We discuss the stimulus conditions and then highlight various stimuli responsive nanocarriers in the tumor microenvironment for cancer gene therapy. We hope that this review will inspire readers to develop more effective stimuli responsive nanocarriers for delivering genes.

Application Perspectives of Nanomedicine in Cancer Treatment

Cancer is a disease that seriously threatens human health. Based on the improvement of traditional treatment methods and the development of new treatment modes, the pattern of cancer treatment is constantly being optimized. Nanomedicine plays an important role in these evolving tumor treatment modalities. In this article, we outline the applications of nanomedicine in three important tumor-related fields: chemotherapy, gene therapy, and immunotherapy. According to the current common problems, such as poor targeting of first-line chemotherapy drugs, easy destruction of nucleic acid drugs, and common immune-related adverse events in immunotherapy, we discuss how nanomedicine can be combined with these treatment modalities, provide typical examples, and summarize the advantages brought by the application of nanomedicine.

Gene Therapy in Orthopaedics: Progress and Challenges in Pre-Clinical Development and Translation

In orthopaedics, gene-based treatment approaches are being investigated for an array of common -yet medically challenging- pathologic conditions of the skeletal connective tissues and structures (bone, cartilage, ligament, tendon, joints, intervertebral discs etc.). As the skeletal system protects the vital organs and provides weight-bearing structural support, the various tissues are principally composed of dense extracellular matrix (ECM), often with minimal cellularity and vasculature. Due to their functional roles, composition, and distribution throughout the body the skeletal tissues are prone to traumatic injury, and/or structural failure from chronic inflammation and matrix degradation. Due to a mixture of environment and endogenous factors repair processes are often slow and fail to restore the native quality of the ECM and its function. In other cases, large-scale lesions from severe trauma or tumor surgery, exceed the body’s healing and regenerative capacity. Although a wide range of exogenous gene products (proteins and RNAs) have the potential to enhance tissue repair/regeneration and inhibit degenerative disease their clinical use is hindered by the absence of practical methods for safe, effective delivery. Cumulatively, a large body of evidence demonstrates the capacity to transfer coding sequences for biologic agents to cells in the skeletal tissues to achieve prolonged delivery at functional levels to augment local repair or inhibit pathologic processes. With an eye toward clinical translation, we discuss the research progress in the primary injury and disease targets in orthopaedic gene therapy. Technical considerations important to the exploration and pre-clinical development are presented, with an emphasis on vector technologies and delivery strategies whose capacity to generate and sustain functional transgene expression in vivo is well-established.

Testing preexisting antibodies prior to AAV gene transfer therapy: rationale, lessons and future considerations

Given the increasing number of gene transfer therapy studies either completed or underway, there is growing attention to the importance of preexisting adaptive immunity to the viral vectors used. The recombinant viral vectors developed for gene transfer therapy share structural features with naturally occurring wild-type virus. Antibodies generated against viral vectors obtained through a previous exposure to wild-type virus can potentially compromise transgene expression by blocking transduction, thereby limiting the therapeutic efficacy of the gene transfer therapy; they may also pose potential safety concerns. Therefore, systemic gene transfer delivery requires testing patients for preexisting antibodies. Two different assays have been used: (1) binding assays that focus on total antibodies (both neutralizing and non-neutralizing) and (2) neutralizing assays that detect neutralizing antibodies. In this review we focus on adeno-associated virus-based gene therapies, describing the immune response that occurs to naturally occurring adeno-associated viruses, the implications for patients with this exposure, the assays used to detect preexisting immune responses, and strategies to circumvent preexisting adaptive immunity to expand the patient base that could benefit from such therapies.

Evaluation of a D-Octaarginine-linked polymer as a transfection tool for transient and stable transgene expression in human and murine cell lines

Poly(N-vinylacetamide-co-acrylic acid) coupled with d-octaarginine (VP-R8) promotes the cellular uptake of peptides/proteins in vitro; however, details of the transfection efficacy of VP-R8, such as the cell types possessing high gene transfer, are not known. Herein, we compared the ability of VP-R8 to induce the cellular uptake of plasmid DNA in mouse and human cell lines from different tissues and organs. A green fluorescent protein (GFP)-expression plasmid was used as model genetic material, and fluorescence as an indicator of uptake and plasmid-derived protein expression. Three mouse and three human cell lines were incubated with a mixture of plasmid and VP-R8, and fluorescence analysis were performed two days after transfection. To confirm stable transgene expression, we performed drug selection three days after transfection. A commercially available polymer-based DNA transfection reagent (PTR) was used as the transfection control and standard for comparing transgene expression efficiency. In the case of transient transgene expression, slight-to-moderate GFP expression was observed in all cell lines transfected with plasmid via VP-R8; however, transfection efficiency was lower using the PTR for gene delivery. In the case of stable transgene expression, VP-R8 promoted drug-resistance acquisition more efficiently than the PTR did. Cells that developed drug resistance after VP-R8‒mediated gene transfection expressed GFP more efficiently than cells that developed drug resistance after transfection with the PTR. Thus, VP-R8 shows potential as an in vitro or ex vivo nonviral transfection tool for generating cell lines with stable transgene expression.

Insights and future directions of potential genetic therapy for Apert syndrome: A systematic review

Apert syndrome is a genetic disorder characterised by craniosynostosis and structural discrepancy of the craniofacial region as well as the hands and feet. This condition is closely linked with fibroblast growth factor receptor-2 (FGFR2) gene mutations. Gene therapies are progressively being tested in advanced clinical trials, leading to a rise of its potential clinical indications. In recent years, research has made great progress in the gene therapy of craniosynostosis syndromes and several studies have investigated its influences in preventing/diminishing the complications of Apert syndrome. This article reviewed and exhibited different techniques of gene therapy and their influences in Apert syndrome progression. A systematic search was executed using electronic bibliographic databases including PubMed, EMBASE, ScienceDirect, SciFinder and Web of Science for all studies of gene therapy for Apert syndrome. The primary outcomes measurements vary from protein to gene expressions. According to the findings of included studies, we conclude that the gene therapy using FGF in Apert syndrome was critical in the regulation of suture fusion and patency, occurred via alterations in cellular proliferation. The superior outcome could be brought by biological therapies targeting the FGF/FGFR signalling. More studies in molecular genetics in Apert syndrome are recommended. This study reviews the current literature and provides insights to future possibilities of genetic therapy as intervention in Apert syndrome.

A Small Virus to Deliver Small Antibodies: New Targeted Therapies Based on AAV Delivery of Nanobodies

Nanobodies are camelid-derived single-domain antibodies that present some advantages versus conventional antibodies, such as a smaller size, and higher tissue penetrability, stability, and hydrophilicity. Although nanobodies can be delivered as proteins, in vivo expression from adeno-associated viral (AAV) vectors represents an attractive strategy. This is due to the fact that AAV vectors, that can provide long-term expression of recombinant genes, have shown an excellent safety profile, and can accommodate genes for one or several nanobodies. In fact, several studies showed that AAV vectors can provide sustained nanobody expression both locally or systemically in preclinical models of human diseases. Some of the pathologies addressed with this technology include cancer, neurological, cardiovascular, infectious, and genetic diseases. Depending on the indication, AAV-delivered nanobodies can be expressed extracellularly or inside cells. Intracellular nanobodies or “intrabodies” carry out their function by interacting with cell proteins involved in disease and have also been designed to help elucidate cellular mechanisms by interfering with normal cell processes. Finally, nanobodies can also be used to retarget AAV vectors, when tethered to viral capsid proteins. This review covers applications in which AAV vectors have been used to deliver nanobodies, with a focus on their therapeutic use.

Decorating Bacteria with a Therapeutic Nanocoating for Synergistically Enhanced Biotherapy

Disorders in the gut microbiota have been implicated in various diseases, such as inflammatory bowel diseases, diabetes, and cancers. Oral microecologics are of great importance due to their ability to directly intervene the gut microbiome as well as their noninvasiveness and low side effects, while have suffered from low bioavailability and a single therapeutic effect. Here, probiotics are coated with a therapeutic nanocoating for synergistically enhanced biotherapy, a method inspired by the robust protective and therapeutic effectiveness of silkworm cocoon. With its transition from a random coil to β-sheet conformation, silk fibroin can self-assemble onto the surface of bacteria. By a simple layer-by-layer procedure, an entire nanocoating can be formed along with a near quantitative coating ratio and almost uninfluenced bacterial viability. Thanks to its protective barrier role and innate pharmaceutical activity, silk fibroin nanocoating endows the coated bacteria with a markedly improved survival against gastric insults and a synergistically enhanced therapeutic effect in a murine model of intestinal mucositis. This work demonstrates how therapeutic elements can be combined with probiotics via a simple coating strategy and proposes an alternative to enhance bioavailability and treatment efficacy of oral microecologics.

Primary cilia in retinal pigment epithelium development and diseases

Retinal pigment epithelium (RPE) is a highly polarized epithelial monolayer lying between the photoreceptor layer and the Bruch membrane. It is essential for vision through participating in many critical activities, including phagocytosis of photoreceptor outer segments, recycling the visual cycle‐related compounds, forming a barrier to control the transport of nutrients, ions, and water, and the removal of waste. Primary cilia are conservatively present in almost all the vertebrate cells and acts as a sensory organelle to control tissue development and homeostasis maintenance. Numerous studies reveal that abnormalities in RPE lead to various retinal diseases, such as age‐related macular degeneration and diabetic macular oedema, but the mechanism of primary cilia in these physiological and pathological activities remains to be elucidated. Herein, we summarize the functions of primary cilia in the RPE development and the mutations of ciliary genes identified in RPE‐related diseases. By highlighting the significance of primary cilia in regulating the physiological and pathological processes of RPE, we aim to provide novel insights for the treatment of RPE‐related retinal diseases.

Recent Progress of Machine Learning in Gene Therapy

With new developments in biomedical technology, it is now a viable therapeutic treatment to alter genes with techniques like CRISPR. At the same time, it is increasingly cheaper to do whole genome sequencing, resulting in rapid advancement in gene therapy and editing in precision medicine. Thus, understanding the current industry and academic applications of gene therapy provides an important backdrop to future scientific developments. Additionally, machine learning and artificial intelligence techniques allow for the reduction of time and money spent in the development of new gene therapy products and techniques. In this paper, we survey the current progress of gene therapy treatments for several diseases and explore machine learning applications in gene therapy. We also discuss the ethical implications of gene therapy and the use of machine learning in precision medicine. Machine learning and gene therapy are both topics gaining popularity in various publications, and we conclude that there is still room for continued research and application of machine learning techniques in the gene therapy field.

Design and Validation of Liposomal ApoE2 Gene Delivery System to Evade Blood-Brain Barrier for Effective Treatment of Alzheimer's Disease

Targeting gene-based therapeutics to the brain is a strategy actively sought to treat Alzheimer's disease (AD). Recent findings discovered the role of apolipoprotein E (ApoE) isoforms in the clearance of toxic amyloid beta proteins from the brain. ApoE2 isoform is beneficial for preventing AD development, whereas ApoE4 is a major contributing factor to the disease. In this paper, we demonstrated efficient brain-targeted delivery of ApoE2 encoding plasmid DNA (pApoE2) using glucose transporter-1 (glut-1) targeted liposomes. Liposomes were surface-functionalized with a glut-1 targeting ligand mannose (MAN) and a cell-penetrating peptide (CPP) to enhance brain-targeting and cellular internalization, respectively. Among various CPPs, rabies virus glycoprotein peptide (RVG) or penetratin (Pen) was selected as a cell-penetration enhancer. Dual (RVGMAN and PenMAN)-functionalized liposomes were cytocompatible at 100 nM phospholipid concentration and demonstrated significantly higher expression of ApoE2 in bEnd.3 cells, primary neurons, and astrocytes compared to monofunctionalized and unmodified (plain) liposomes. Dual-modified liposomes also showed ∼2 times higher protein expression than other formulation controls in neurons cultured below the in vitro BBB model. These results translated well to in vivo efficacy study with significantly higher transfection of pApoE2 in the C57BL/6 mice brain following single tail vein administration of RVGMAN and PenMAN functionalized liposomes without any noticeable signs of toxicity. These results illustrate the potential of surface-modified liposomes for safe and brain-targeted delivery of the pApoE2 gene for effective AD therapy.

HHIP Overexpression Suppresses Human Gastric Cancer Progression and Metastasis by Reducing Its CpG Island Methylation

Human hedgehog-interacting protein (HHIP), a negative regulator of hedgehog (HH) signaling pathway, has been reported to be dysregulated in many types of cancer, including gastric cancer. However, the inhibitory role of HHIP as well as the underlying molecular mechanism of HHIP regulation in gastric cancer haven't been fully elucidated yet. In this study, we demonstrated that HHIP overexpression significantly suppressed the proliferation and invasion of AGS cells evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and transwell assays, respectively. Interestingly, methylation-specific polymerase chain reaction (MS-PCR, MSP) showed that HHIP overexpression dramatically decreased its de novo promoter methylation levels in AGS cells. Furthermore, HHIP expression was higher in adjacent non-cancerous tissue compared to matched gastric cancer tissue. High HHIP level was negatively correlated with metastasis (p = 0.035) but not local recurrence (p = 0.58). Taken together, our study suggested that HHIP can modulate gastric cancer progression and metastasis via regulation of its de novo promoter methylation levels in a feedback manner. Lower HHIP levels is positively associated with gastric cancer metastasis, which not only indicates HHIP could be served as a protective marker for gastric cancer, but also suggests restoring HHIP expression might be a potential therapeutic strategy for clinical treatment.

Gene Replacement Therapy: A Primer for the Health-system Pharmacist

PURPOSE

Comprehensive review of gene replacement therapy with guidance and expert opinion on handling and administration for pharmacists.

SUMMARY

There are currently ∼2600 gene therapy clinical trials worldwide and 4 Food and Drug Administration (FDA)-approved gene therapy products available in the United States. Gene therapy and its handling are different from other drugs; however, there is a lack of guidance from the National Institutes of Health (NIH), FDA, Centers for Disease Control and Prevention (CDC), World Health Organization (WHO), and professional associations regarding their pharmaceutical application. Although the NIH stratifies the backbone biologicals of viral vectors in gene therapies into risk groups, incomplete information regarding minimization of exposure and reduction of risk exists. In the absence of defined guidance, individual institutions develop their own policies and procedures, which often differ and are often outdated. This review provides expert opinion on the role of pharmacists in institutional preparedness, as well as gene therapy handling and administration. A suggested infrastructural model for gene replacement therapy handling is described, including requisite equipment acquisition and standard operating procedure development. Personnel, patient, and caregiver education and training are discussed.

CONCLUSION

Pharmacists have a key role in the proper handling and general management of gene replacement therapies, identifying risk level, establishing infrastructure, and developing adequate policies and protocols, particularly in the absence of consensus guidelines for the handling and transport of gene replacement therapies.

Redox stimulus disulfide conjugated polyethyleneimine as a shuttle for gene transfer

Redox-responsive cationic polymers have gained considerable attention in gene delivery due to low cytotoxicity and spatio-temporal release of DNA into the cells. Here, we reported the synthesis of reducible disulfide conjugated polyethyleneimine (1.8 kDa) (denoted as SS-PEI) and its application to transfer pEGFP-ZNF580 plasmid (pZNF580) into EA.hy926 cell. This reducible SS-PEI polymer was prepared by one-step polycondensation reaction of low molecular weight PEI with bis-(p-nitrophenyl)-3,3'-dithiodipropionate. The SS-PEI successfully condensed pZNF580 into nano-sized complexes (170 ± 1.5 nm to 255 ± 1.6 nm) with zeta potentials of 3 ± 0.4 mV to 17 ± 0.9 mV. The complexes could be triggered to release pZNF580 when exposed to the reducing environment of 5 mM dithiothreitol. Besides, the SS-PEI exhibited low cytotoxicity. In vitro transfection results showed that SS-PEI exhibited good transfection efficiency comparable to PEI25kDa. Thus, the SS-PEI could act as an reducible gene carrier with good transfection efficiency and low cytotoxicity.

Modulating gene regulation to treat genetic disorders

Over a thousand diseases are caused by mutations that alter gene expression levels. The potential of nuclease-deficient zinc fingers, TALEs or CRISPR fusion systems to treat these diseases by modulating gene expression has recently emerged. These systems can be applied to modify the activity of gene-regulatory elements - promoters, enhancers, silencers and insulators, subsequently changing their target gene expression levels to achieve therapeutic benefits - an approach termed cis-regulation therapy (CRT). Here, we review emerging CRT technologies and assess their therapeutic potential for treating a wide range of diseases caused by abnormal gene dosage. The challenges facing the translation of CRT into the clinic are discussed.

Externally-Controlled Systems for Immunotherapy: From Bench to Bedside

Immunotherapy is a very promising therapeutic approach against cancer that is particularly effective when combined with gene therapy. Immuno-gene therapy approaches have led to the approval of four advanced therapy medicinal products (ATMPs) for the treatment of p53-deficient tumors (Gendicine and Imlygic), refractory acute lymphoblastic leukemia (Kymriah) and large B-cell lymphomas (Yescarta). In spite of these remarkable successes, immunotherapy is still associated with severe side effects for CD19+ malignancies and is inefficient for solid tumors. Controlling transgene expression through an externally administered inductor is envisioned as a potent strategy to improve safety and efficacy of immunotherapy. The aim is to develop smart immunogene therapy-based-ATMPs, which can be controlled by the addition of innocuous drugs or agents, allowing the clinicians to manage the intensity and durability of the therapy. In the present manuscript, we will review the different inducible, versatile and externally controlled gene delivery systems that have been developed and their applications to the field of immunotherapy. We will highlight the advantages and disadvantages of each system and their potential applications in clinics.

Appropriate Delivery of the CRISPR/Cas9 System through the Nonlysosomal Route: Application for Therapeutic Gene Editing

The development of gene delivery has attracted increasing attention, especially when the introduction and application of the CRISPR/Cas9 gene editing system appears promising for gene therapy. However, ensuring biosafety and high gene editing efficiency at the same time poses a great challenge for its in vivo applications. Herein, a pardaxin peptide (PAR)-modified cationic liposome (PAR-Lipo) is developed. The results are indicative that significantly enhanced gene editing efficiency can be obtained through the mediation of PAR-Lipos compared to non-Lipos (non-PAR-modified liposomes) and Lipofectamine 2000, owing to its protection toward carried nucleotide by the prevention of lysosomal capture, prolongation of retention time in cells through the accumulation in the endoplasmic reticulum (ER), and more importantly, facilitation of the nuclear access via an ER-nucleus route. Accumulation of PAR-Lipos in the ER may improve the binding of Cas9 and sgRNA, thus further contributing to the eventually enhanced gene editing efficiency. Given their high biosafety, PAR-Lipos are used to mediate the knockout of the oncogene CDC6 in vivo, which results in significant tumor growth inhibition. This work may provide a useful reference for enhancing the delivery of gene editing systems, thus improving the potential for their future clinical applications.

Gene therapies for high-grade gliomas: from the bench to the bedside

Background:

Gene therapy is the most attractive therapeutic approach against high-grade gliomas (HGGs). This is because of its theoretical capability to rework gene makeup in order to yield oncolytic effects. However, some factors still limit the upgrade of these therapies at a clinical level of evidence. We report an overview of glioblastoma gene therapies, mainly focused on the rationale, classification, advances and translational challenges.

Methods:

An extensive review of the online literature on gene therapy for HGGs was carried out. The PubMed/MEDLINE and ClinicalTrials.gov websites were the main sources. Articles in English published in the last five years were sorted according to the best match with the multiple relevant keywords chosen. A descriptive analysis of the clinical trials was also reported.

Results:

A total of 85 articles and 45 clinical trials were selected. The main types of gene therapies are the suicide gene, tumor suppressor gene, immunomodulatory gene and oncolytic therapies (virotherapies). The transfer of genetic material entails replication-deficient and replication-competent oncolytic viruses and nanoparticles, such as liposomes and cationic polymers, each of them having advantages and drawbacks. Forty-eight clinical trials were collected, mostly phase I/II.

Conclusion:

Gene therapies constitute a promising approach against HGGs. The selection of new and more effective target genes, the implementation of gene-delivery vectors capable of greater and safer spreading capacity, and the optimization of the administration routes constitute the main translational challenges of this approach. (www.actabiomedica.it)

GLUT-1: An Effective Target To Deliver Brain-Derived Neurotrophic Factor Gene Across the Blood Brain Barrier

Alzheimer's disease (AD), the most common cause of dementia, inflicts enormous suffering to patients and their family members. It is the third deadliest disease, affecting 46.8 million people worldwide. Brain-derived neurotrophic factor (BDNF) is involved in the development, maintenance, and plasticity of the central nervous system. This crucial protein is significantly reduced in AD patients leading to reduced plasticity and neuronal death. In this study, we demonstrate the targeted delivery of the BDNF gene to the brain using liposome nanoparticles. These liposomes were surface modified with glucose transporter-1 targeting ligand (mannose) and cell penetrating peptides (penetratin or rabies virus glycoprotein) to promote selective and enhanced delivery to the brain. Surface modified liposomes showed significantly higher transfection of BDNF in primary astrocytes and neurons, compared to unmodified (plain) liposomes. BDNF transfection via dual modified liposomes resulted in an increase in presynaptic marker synaptophysin protein in primary neuronal cells, which is usually found to be reduced in AD patients. Liposomes surface modified with mannose and cell penetrating peptides demonstrated ∼50% higher transport across the in vitro blood brain barrier (BBB) model and showed significantly higher transfection efficiency in primary neuronal cells compared to plain liposomes. These results were correlated with significantly higher transport of surface modified liposomes (∼7% of injected dose/gram of tissue) and BDNF transfection (∼1.7 times higher than baseline level) across BBB following single intravenous administration in C57BL/6 mice without any signs of inflammation or toxicity. Overall, this study suggests a safe and targeted strategy to increase BDNF protein in the brain, which has the potential to reverse AD pathophysiology.

Targeted Delivery of Recombinant Heat Shock Protein 27 to Cardiomyocytes Promotes Recovery from Myocardial Infarction

Ischemic heart disease, especially myocardial infarction (MI), is the leading cause of death worldwide. Apoptotic mechanisms are thought to play a significant role in cardiomyocyte death after MI. Increased production of heat shock proteins (Hsps) in cardiomyocytes is a normal response to promote tolerance and to reduce cell damage. Hsp27 is considered to be a therapeutic option for the treatment of ischemic heart disease due to its protective effects on hypoxia-induced apoptosis. Despite its antiapoptotic effects, the lack of strategies to deliver Hsp27 to the heart tissue in vivo limits its clinical applicability. In this study, we utilized an antibody against the angiotensin II type 1 (AT1) receptor, which is expressed immediately after ischemia/reperfusion in the heart of MI rats. To achieve cardiomyocyte-targeted Hsp27 delivery after ischemia/reperfusion, we employed the immunoglobulin-binding dimer ZZ, a modified domain of protein A, in conjunction with the AT1 receptor antibody. Using the AT1 receptor antibody, we achieved systemic delivery of ZZ-TAT-GFP fusion protein into the heart of MI rats. This approach enabled selective delivery of Hsp27 to cardiomyocytes, rescued cells from apoptosis, reduced the area of fibrosis, and improved cardiac function in the rat MI model, thus suggesting its applicability as a cardiomyocyte-targeted protein delivery system to inhibit apoptosis induced by ischemic injury.

The role of hypoxia-inducible factors in neovascular age-related macular degeneration: a gene therapy perspective

Understanding the mechanisms that underlie age-related macular degeneration (AMD) has led to the identification of key molecules. Hypoxia-inducible transcription factors (HIFs) have been associated with choroidal neovascularization and the progression of AMD into the neovascular clinical phenotype (nAMD). HIFs regulate the expression of multiple growth factors and cytokines involved in angiogenesis and inflammation, hallmarks of nAMD. This knowledge has propelled the development of a new group of therapeutic strategies focused on gene therapy. The present review provides an update on current gene therapies in ocular angiogenesis, particularly nAMD, from both basic and clinical perspectives.

Clinical development on the frontier: gene therapy for duchenne muscular dystrophy

Introduction: The development of adeno-associated virus (AAV) vectors as safe vehicles for in vivo delivery of therapeutic genes has been a major milestone in the advancement of gene therapy, enabling a promising strategy for ameliorating a wide range of diseases, including Duchenne muscular dystrophy (DMD).Areas covered: Based on experience with the development of a gene transfer therapy agent for DMD, we discuss ways in which gene therapy for rare disease challenges traditional clinical development paradigms, and recommend a step-wise approach for design and evaluation to support broader applicability of gene therapy.Expert opinion: The gene therapy development approach should intentionally design the therapeutic construct and the clinical study to systematically evaluate agent delivery, safety, and efficacy. Rigorous preclinical work is essential for establishing an effective gene delivery platform and determining the efficacious dose. Clinical studies should thoroughly evaluate transduction, on-target transgene expression at the tissue and cellular level, and functional efficacy.

AA, Lukashev AN. Emerging Concepts and Challenges in Rheumatoid Arthritis Gene Therapy

Rheumatoid arthritis (RA) is a systemic inflammatory joint disease affecting about 1% of the population worldwide. Current treatment approaches do not ensure a cure for every patient. Moreover, classical regimens are based on nontargeted systemic immune suppression and have significant side effects. Biological treatment has advanced considerably but efficacy and specificity issues remain. Gene therapy is one of the potential future directions for RA therapy, which is rapidly developing. Several gene therapy trials done so far have been of moderate success, but experimental and genetics studies have yielded novel targets. As a result, the arsenal of gene therapy tools keeps growing. Currently, both viral and nonviral delivery systems are used for RA therapy. Herein, we review recent approaches for RA gene therapy.

Episomal vectors based on S/MAR and the β-globin Replicator, encoding a synthetic transcriptional activator, mediate efficient γ-globin activation in haematopoietic cells

We report the development of episomal vectors for the specific γ-globin transcription activation in its native position by activator Zif-VP64, based on the Scaffold/Matrix Attachment Region (S/MAR) for episomal retention and the β-globin Replicator, the DNA replication-Initiation Region from the β-globin locus. Vector Zif-VP64-Ep1 containing transcription cassettes CMV- Zif-VP64 and CMV-eGFP-S/MAR transfected a)K562 cells; b)murine β-YAC bone marrow cells (BMC); c)human haematopoietic progenitor CD34⁺ cells, with transfection efficiencies of 46.3 ± 5.2%, 23.0 ± 2.1% and 24.2 ± 2.4% respectively. K562 transfections generated stable cell lines running for 28 weeks with and without selection, with increased levels of γ-globin mRNA by 3.3 ± 0.13, of γ-globin protein by 6.75 ± 3.25 and HbF protein by 2 ± 0.2 fold, while the vector remained episomal and non integrated. In murine β-YAC BMCs the vector mediated the activation of the silent human γ-globin gene and in CD34⁺ cells, increased γ-globin mRNA, albeit only transiently. A second vector Zif-VP64-Ep2, with both transcription cassettes carrying promoter SFFV instead of CMV and the addition of β-globin Replicator, transferred into CD34⁺ cells, produced CD34⁺ eGFP⁺ cells, that generated colonies in colony forming cell cultures. Importantly, these were 100% fluorescent, with 2.11 ± 0.13 fold increased γ-globin mRNA, compared to non-transfected cells. We consider these episomal vectors valid, safer alternatives to viral vectors.

Generation of a caged lentiviral vector through an unnatural amino acid for photo-switchable transduction

Application of viral vectors in gene delivery is attracting widespread attention but is hampered by the absence of control over transduction, which may lead to non-selective transduction with adverse side effects. To overcome some of these limitations, we proposed an unnatural amino acid aided caging–uncaging strategy for controlling the transduction capability of a viral vector. In this proof-of-principle study, we first expanded the genetic code of the lentiviral vector to incorporate an azido-containing unnatural amino acid (Nϵ-2-azidoethyloxycarbonyl-l-lysine, NAEK) site specifically within a lentiviral envelope protein. Screening of the resultant vectors indicated that NAEK incorporation at Y77 and Y116 was capable of inactivating viral transduction upon click conjugation with a photo-cleavable chemical molecule (T1). Exposure of the chimeric viral vector (Y77-T1) to UVA light subsequently removed the photo-caging group and restored the transduction capability of lentiviral vector both in vitro and in vivo. Our results indicate that the use of the photo-uncage activation procedure can reverse deactivated lentiviral vectors and thus enable regulation of viral transduction in a switchable manner. The methods presented here may be a general approach for generating various switchable vectors that respond to different stimulations and adapt to different viral vectors.

Thermosensitive Hydrogel Delivery of Human Periodontal Stem Cells Overexpressing Platelet-Derived Growth Factor-BB Enhances Alveolar Bone Defect Repair

Alveolar bone defects can arise as a consequence of trauma, infection, periodontal disease, or congenital alveolar fenestration. Many approaches have been employed in an effort to treat or overcome such defects, but the ability to effectively achieve alveolar regeneration remains elusive. Platelet-derived growth factor-BB (PDGF-BB) has been shown to serve as a key factor capable of orchestrating cell proliferation, angiogenesis, and chemoattraction in the context of osteogenic processes. Exactly how PDGF-BB affects human periodontal ligament stem cells (hPDLSCs), however, requires further exploration. In this report, we utilized a lentiviral construct to achieve PDGF-BB overexpression in hPDLSCs, allowing us to establish that this gene was able to enhance the proliferation of these cells and to mediate osteogenic gene upregulation therein. In addition, we established a rat model of alveolar defects that were implanted using different complexes, and then monitored through histological and micro-CT analyses 4 and 8 weeks postsurgery to assess bone repair outcomes. These analyses revealed that a thermosensitive hydrogel was an effective 3D cell culture scaffold, while PDLSCs overexpressing PDGF-BB enhanced bone growth in the context of alveolar bone defects. Together, these results thus indicate that PDGF-BB represents a potent means of promoting stem cell-based alveolar bone tissue regeneration.

Spleen selective enhancement of transfection activities of plasmid DNA driven by octaarginine and an ionizable lipid and its implications for cancer immunization

Efficiently delivering plasmid DNA (pDNA) to the spleen is particularly significant for DNA immunization. However, increasing the efficiency of gene expression in spleen cells for achieving a therapeutic effect remains a serious challenge. An ideal spleen-targeted system should avoid liver uptake and should efficiently transfect specific functional spleen cells. Here, we report on pDNA nanocarriers with enhanced transfection in spleen cells driven by synergism between an octaarginine (R8) peptide and YSK05; a pH-responsive ionizable lipid. A double-coating design is essential for enhancing spleen selective transfection which is significantly affected by the total amount of lipid and the composition of the outer coat. The optimized R8/YSK system shows a high gene expression in the spleen with a high spleen/liver ratio and a surprising ability to target spleen B cells. Compared to other organs, the high spleen activity cannot be explained based on the amount of pDNA delivered to each organ, indicating that the system is extremely efficient in transfecting spleen cells. The system can be used in cancer immunization where a strong anti-tumor effect was observed in mice immunized with the R8/YSK system encapsulating antigen-encoding pDNA. The R8/YSK system holds great promise for future applications in the field of DNA vaccination.

Recent advances in the targeting of systemically administered non-viral gene delivery systems

Introduction: Systemically administered non-viral gene delivery systems face multiple biological barriers that decrease their efficiency. These systems are rapidly cleared from the circulation and sufficient concentrations do not accumulate in diseased tissues. A number of targeting strategies can be used to provide for sufficient accumulation in the desired tissues to achieve a therapeutic effect. Areas covered: We discuss recent advances in the targeting of non-viral gene delivery systems to different tissues after systemic administration. We compare passive and active targeting applied for tumor delivery and propose some strategies that can be used to overcome the drawbacks of each case. We also discuss targeting the liver and lungs as two particularly important organs in gene therapy. Expert opinion: There is currently no optimum non-viral gene delivery system for targeting genes to specific tissues. The dose delivered to tumor tissues using passive targeting is low and shows a high patient variation. Although active targeting can enhance binding to specific cells, only a few reports are available to support its value in vivo. The design of smart nanocarriers for promoting active targeting is urgently needed and targeting the endothelium is a promising strategy for gene delivery to tumors as well as other organs.

The Landscape of Cellular and Gene Therapy Products: Authorization, Discontinuations, and Cost

Background: Cell and gene therapy products belong to a diverse class of biopharmaceuticals known as advanced therapy medicinal products. Cell and gene therapy products are used for the treatment and prevention of diseases that until recently were only managed chronically. The objective of this study was to examine the characteristics of market authorizations, discontinuations, and prices of cellular and gene therapy products worldwide. Data and Methods: We conducted an electronic search of authorized cell, tissue-engineered, and gene therapy products from the databases of the main drug regulatory agencies. The analysis excluded hematopoietic progenitor cell cord blood products authorized by the U.S. Food and Drug Administration. Price information was derived from the Red Book (Truven Health Analytics) for the United States, health technology assessment agencies for Europe, and other public sector sources and company news for other countries. We also searched the scientific literature for authorizations, discontinuations, and price information using MEDLINE/PubMed, Cochrane Library, Google Scholar, and EMBASE databases. All cost data were converted to U.S. dollars. Descriptive analysis was conducted in this study. Results: There were 52 different cell, tissue engineering and gene therapy products with 69 market authorizations in the world as of December 31, 2018. The products included 18 (34%) cell therapies, 23 (43.4%) tissue engineered products, and 12 (22.6%) gene therapies. There were 21 (30.4% of all authorizations) cell therapy, 26 (37.7%) tissue-engineered, and 22 (31.9%) gene therapy market authorizations. The EMA withdrew the authorization for two tissue engineering products, one cell therapy and one gene therapy, and New Zealand lapsed approval of one cell therapy. Most products were first authorized after 2010, including 10 (83.3%) gene therapies, 13 (72.2%) cell therapies, and 13 (56.5%) tissue-engineered products. The treatment price for four allogenic cell therapies varied from $2,150 in India to $200,000 in Canada. The treatment price for three autologous cell therapies ranged from $61,500 in the United Kingdom to a listed price of $169,206 in the United States. Tissue-engineered treatment prices varied from $400 in South Korea to $123,154 in Japan. Gene therapy treatment prices ranged from $5,501 for tonogenchoncel-L in South Korea to $1,398,321 for alipogene tiparvovec in Germany. Conclusions: A significant number of new cell, tissue, and gene therapies have been approved in the past decade. Most products were conditionally authorized and targeted rare cancers, genetic diseases, and other debilitating diseases. However, there are also products approved for cosmetic reasons. Cell, tissue, and gene therapies are among the most expensive therapies available. Healthcare systems are not prepared to assume the cost of future therapies for a myriad of rare diseases and common diseases of epidemic proportions.

Effects of gene therapy on cardiovascular symptoms of lysosomal storage diseases

Lysosomal storage diseases (LSDs) are inherited conditions caused by impaired lysosomal function and consequent substrate storage, leading to a range of clinical manifestations, including cardiovascular disease. This may lead to significant symptoms and even cardiac failure, which is an important cause of death among patients. Currently available treatments do not completely correct cardiac involvement in the LSDs. Gene therapy has been tested as a therapeutic alternative with promising results for the heart disease. In this review, we present the results of different approaches of gene therapy for LSDs, mainly in animal models, and its effects in the heart, focusing on protocols with cardiac functional analysis.

The Collaborative Cross: A Systems Genetics Resource for Studying Host-Pathogen Interactions

Host genetic variation has a major impact on infectious disease susceptibility. The study of pathogen resistance genes, largely aided by mouse models, has significantly advanced our understanding of infectious disease pathogenesis. The Collaborative Cross (CC), a newly developed multi-parental mouse genetic reference population, serves as a tractable model system to study how pathogens interact with genetically diverse populations. In this review, we summarize progress utilizing the CC as a platform to develop improved models of pathogen-induced disease and to map polymorphic host response loci associated with variation in susceptibility to pathogens.

Gene Therapy: An Outstanding Technique For Diseases

Nearly three decades ago, the first clinical trial based on gene therapy revolutionized the scientific field by demonstrating that it was possible to genetically modify harmful or defective cells and therapeutically improve patient conditions. Since then, this technique has been implemented for the study and treatment of different diseases, many of them fatal, with the hope of achieving a "cure". Several genetic editing tools have been developed and continue to be studied to improve the effectiveness of gene therapy, in addition to a more exhaustive analysis for choosing the type of vector, which is the main cause of adverse effects. In this review, we present characteristics of the gene therapy mechanism along with the types of vectors that are used in this procedure, followed by the most important applications in the medical field and briefly we describe some limitations and prospects to study in the future.

Genome-edited skin epidermal stem cells protect mice from cocaine-seeking behaviour and cocaine overdose

Cocaine addiction is associated with compulsive drug-seeking, and exposure to the drug or to drug-associated cues leads to relapse, even after long periods of abstention. A variety of pharmacological targets and behavioral interventions have been explored to counteract cocaine addiction, but to date no market-approved medications for treating cocaine addiction or relapse exist, and effective interventions for acute emergencies resulting from cocaine overdose are lacking. We recently demonstrated that skin epidermal stem cells can be readily edited by using CRISPR (clustered regularly interspaced short palindromic repeats) and then transplanted back into the donor mice. Here, we show that the transplantation, into mice, of skin cells modified to express an enhanced form of butyrylcholinesterase, an enzyme that hydrolyzes cocaine, enables the long-term release of the enzyme and efficiently protects the mice from cocaine-seeking behavior and cocaine overdose. Cutaneous gene therapy through skin transplants that elicit drug elimination may offer a therapeutic option to address drug abuse.

Biomaterial substrate modifications that influence cell-material interactions to prime cellular responses to nonviral gene delivery

IMPACT STATEMENT

This review summarizes how biomaterial substrate modifications (e.g. chemical modifications like natural coatings, ligands, or functional side groups, and/or physical modifications such as topography or stiffness) can prime the cellular response to nonviral gene delivery (e.g. affecting integrin binding and focal adhesion formation, cytoskeletal remodeling, endocytic mechanisms, and intracellular trafficking), to aid in improving gene delivery for applications where a cell-material interface might exist (e.g. tissue engineering scaffolds, medical implants and devices, sensors and diagnostics, wound dressings).

Cationic Niosomes as Non-Viral Vehicles for Nucleic Acids: Challenges and Opportunities in Gene Delivery

Cationic niosomes have become important non-viral vehicles for transporting a good number of small drug molecules and macromolecules. Growing interest shown by these colloidal nanoparticles in therapy is determined by their structural similarities to liposomes. Cationic niosomes are usually obtained from the self-assembly of non-ionic surfactant molecules. This process can be governed not only by the nature of such surfactants but also by others factors like the presence of additives, formulation preparation and properties of the encapsulated hydrophobic or hydrophilic molecules. This review is aimed at providing recent information for using cationic niosomes for gene delivery purposes with particular emphasis on improving the transportation of antisense oligonucleotides (ASOs), small interference RNAs (siRNAs), aptamers and plasmids (pDNA).

Genetic Strategies for HIV Treatment and Prevention

Conventional HIV gene therapy approaches are based on engineering HIV target cells that are non-permissive to viral replication. However, expansion of gene-modified HIV target cells has been limited in patients. Alternative genetic strategies focus on generating gene-modified producer cells that secrete antiviral proteins (AVPs). The secreted AVPs interfere with HIV entry, and, therefore, they extend the protection against infection to unmodified HIV target cells. Since any cell type can potentially secrete AVPs, hematopoietic and non-hematopoietic cell lineages can function as producer cells. Secretion of AVPs from non-hematopoietic cells opens the possibility of using a genetic approach for HIV prevention. Another strategy aims at modifying cytotoxic T cells to selectively target and eliminate infected cells. This review provides an overview of the different genetic approaches for HIV treatment and prevention.

Cationic cell penetrating peptide modified SNARE protein VAMP8 as free chains for gene delivery

Previously, our group carried out a series of studies using branched polyethyleneimine with 25 000 g mol-1 molar mass (bPEI-25k) as a gene delivery vector and came up with the theory that free cationic chains un-complexed with plasmid DNA (pDNA) can greatly increase the gene transfection efficiency and influence the intracellular delivery process. These free chains can penetrate the membrane quickly, with some of them embedded inside the lipid bi-layers. The "stuck-out" cationic chain ends would shield the signal protein, prevent/delay the development of the later endolysosomes and enhance the efficiency of gene delivery. To mimic the effect of cationic polymers, we selected to use vesicle associated membrane protein-8 (VAMP8) and modified its N-terminus with different cationic cell penetrating peptides (CPPs). The modified fusion proteins are expressed in an Escherichia coli system and purified after extraction. These modified VAMP8 proteins are used as free chains for gene transfection, while using bPEI-25k to condense the pDNA. The results show that the gene transfection efficiency of bPEI-25k/pDNA polyplexes is obviously enhanced in the 293 T cell line. Furthermore, the gene sequences encoding these modified VAMP8 proteins are sub-cloned to pcDNA-3.1 vector and then transferred to 293 T before the treatment with bPEI-25k/pDNA polyplexes. From the result, the transfection efficiency of bPEI-25k/pDNA complexes is enhanced at a similar level to that using modified VAMP8 as free chains. Our current results prove that free cationic chains are probably embedded with the membrane and influence intracellular trafficking, pointing out a new idea to design an effective non-viral gene delivery system.

Digital PCR detection of plasmid DNA administered to the skeletal muscle of a microminipig: a model case study for gene doping detection

Objective

Doping control is an important and indispensable aspect of fair horse racing; genetic doping has been recently included to this. In this study, we aimed to develop a detection method of gene doping. A plasmid cloned with human erythropoietin gene (p.hEPO, 250 μg/head) was intramuscularly injected into a microminipig. Subsequently, p.hEPO was extracted from 1 mL of plasma and detected by droplet digital polymerase chain reaction.

Results

The results confirmed that the maximum amount of plasmid was detected at 15 min after administration and the majority of the plasmid was degraded in the bloodstream within 1–2 days after administration. In contrast, low amounts of p.hEPO were detected at 2–3 weeks after administration. These results suggest that the proposed method to detect gene doping can help obtain information for experiments using horses.

Lentivector Producer Cell Lines with Stably Expressed Vesiculovirus Envelopes

Retroviral and lentiviral vectors often use the envelope G protein from the vesicular stomatitis virus Indiana strain (VSVind.G). However, lentivector producer cell lines that stably express VSVind.G have not been reported, presumably because of its cytotoxicity, preventing simple scale-up of vector production. Interestingly, we showed that VSVind.G and other vesiculovirus G from the VSV New Jersey strain (VSVnj), Cocal virus (COCV), and Piry virus (PIRYV) could be constitutively expressed and supported lentivector production for up to 10 weeks. All G-enveloped particles were robust, allowing concentration and freeze-thawing. COCV.G and PIRYV.G were resistant to complement inactivation, and, using chimeras between VSVind.G and COCV.G, the determinant for complement inactivation of VSVind.G was mapped to amino acid residues 136-370. Clonal packaging cell lines using COCV.G could be generated; however, during attempts to establish LV producer cells, vector superinfection was observed following the introduction of a lentivector genome. This could be prevented by culturing the cells with the antiviral drug nevirapine. As an alternative countermeasure, we demonstrated that functional lentivectors could be reconstituted by admixing supernatant from stable cells producing unenveloped virus with supernatant containing envelopes harvested from cells stably expressing VSVind.G, COCV.G, or PIRYV.G.