Lentiviral vectors, two decades later

Gene therapy and genome editing for primary immunodeficiency diseases

In past two decades the gene therapy using genetic modified autologous hematopoietic stem cells (HSCs) transduced with the viral vector has become a promising alternative option for treating primary immunodeficiency diseases (PIDs). Despite of some pitfalls at early stage clinical trials, the field of gene therapy has advanced significantly in the last decade with improvements in viral vector safety, preparatory regime for manufacturing high quality virus, automated CD34 cell purification. Hence, the overall outcome from the clinical trials for the different PIDs has been very encouraging. In addition to the viral vector based gene therapy, the recent fast moving forward developments in genome editing using engineered nucleases in HSCs has provided a new promising platform for the treatment of PIDs. This review provides an overall outcome and progress in gene therapy clinical trials for SCID-X, ADA-SCID, WAS, X- CGD, and the recent developments in genome editing technology applied in HSCs for developing potential therapy, particular in the key studies for PIDs.

Viral Transduction of DRG Neurons

The manipulation of gene expression is an essential tool to study the function of genes or signaling pathways. Uniform and robust gene manipulation is crucial for successful assays. However, neuronal cells are generally difficult-to-transfect cells with conventional DNA/RNA transfection reagents. Therefore, virus-mediated gene delivery is a primary choice for the studies of gene functions in neurons. In this chapter, we will describe the methods for lentivirus-mediated gene expression or knockdown in DRG neurons.

Lentiviral Vector Production in Suspension Culture Using Serum-Free Medium for the Transduction of CAR-T Cells

The production of lentiviral vectors (LVs) in human embryonic kidney 293 (HEK293) cells using serum-free medium in a suspension culture for the transduction of chimeric antigen receptor T-cells (CAR-T) can be achieved by different methods. This chapter describes LV production by transient transfection, induction of stable packaging cell lines, and induction of stable producer cell lines.

Silencing of GFP expression in human mesenchymal stem cells using quaternary polyplexes of siRNA-PEI with glycosaminoglycans and albumin

In recent years evidence has been mounting for a role for mesenchymal stem cells (MSCs) in immunomodulation, anti-inflammatory processes, and paracrine signaling via secreted extracellular vesicles. In order to exploit these biological functions, systems to efficiently deliver genetic material into MSCs would therefore be highly desirable. In this study, efficient silencing of GFP expression by combining high N/P ratio siRNA and branched PEI (bPEI) polyplexes (siRNA-bPEI) polyplexes with glycosaminoglycans (GAGs), namely hyaluronic acid (HA), chondroitin sulfate (CS) and heparin sulfate (HS), and human serum albumin (HSA) is reported. These quaternary systems were characterized using surface charge, size and morphology and applied to MSCs, which represent a challenge due to their typically low transfection efficiency. The quaternary polyplexes promoted efficient charge shielding and release of siRNA in the cytoplasm with reduced toxicity. A high silencing efficiency of >90% (i.e., less than 10% remaining GFP expression) was achieved with noticeably reduced cellular toxicity, especially with siRNA-bPEI polyplexes modified with HA and HA + HSA. In general addition of GAGs led to more compact polyplexes. Endocytosis studies point to improved endosomal escape at high N/P ratios as a reason for high transfection efficiency and a role for hyaluronic acid in the uptake mechanism likely via CD44 interactions. Co-localization studies showed the polyplexes are stable in the cytosol over time, which correlates with a proper disassembly and subsequent silencing of GFP. Furthermore, GAG containing polyplexes were frequently co-localized with the nucleus. These findings in sum suggest that PEI/HSA/GAG based quaternary polyplexes are promising as transfection agents for MSCs. STATEMENT OF SIGNIFICANCE: Since mesenchymal stem cells (MSCs) are recruited to the site of tissue repair and play a role in immunomodulation, anti-inflammatory processes, and paracrine signaling, they present an excellent target for genetic engineering. However, delivery of genetic material into MSCs is challenging. In this study, >97% silencing of constitutive green fluorescent protein expression in human MSCs (hMSCs) using high N/P ratio polyplexes of branched-PEI-siRNA incorporating glycosaminoglycan as a charge neutralizer and human serum albumin as co-complexing agent is demonstrated. In addition to possessing good cytocompatibility and excellent cytosolic stability; polyplexes incorporating GAGs also showed altered endocytic uptake, with incorporation of hyaluronic acid promoting caveolae-mediated entry. Our system highlights the importance of physiologically derived macromolecules in delivery of genetic material into hMSCs.

Research on the establishment of a TPM3 monoclonal stable transfected PANC-1 cell line and the experiment of the EMT occurrence in human pancreatic cancer

Background: Pancreatic cancer is one of the most aggressive human malignancies that is associated with early metastasis and chemoresistance. Tropomyosin (TPM) is an indispensable regulatory protein for muscle contraction, Abnormal expressions of TPM gene are closely related to the carcinogenesis and metastasis of malignant tumors.

Purpose: In this experiment, a monoclonal stable transfected cell line was established by the knock-down of TMP3 expression in PANC-1 cells with the lentivirus method, and the impacts of the downregulated TPM3 gene expression on the EMT-related molecules and biological behaviors of PANC-1 cells were explored.

Methods: Based on the TPM3 gene sequence, we designed the RNA interference sequence, constructed and screened out the recombinant plasmid segment TPM3-shRNA with the optimal silencing effect, and carried out lentivirus titer determination and packaging. The recombinant lentiviral interference vector LV-TPM3-shRNA was transfected into PANC-1 cells; the transfection efficiency was then evaluated to screen out the monoclonal stable transfected PANC-1 cell line with downregulated TPM3 expression. The qRT-PCR and Western blot were used to detect the changes in the gene- and protein-levels expressions of EMT-related transcription factors in the target cell line and to respectively test the variations of the invasion and proliferation capacities.

Results: It is shown that the monoclonal stable transfected PANC-1 cell line with downregulated TPM3 expression was successfully established with the recombinant lentiviral vector. After knocking down the expression of TPM3 gene in PANC-1 cells, EMT occurred in the cells; the cell phenotype showed malignant transformation, and the in vitro biological behaviors of the cells (such as proliferation and invasion) were enhanced to different degrees.

Conclusion: It is indicated that the TPM3 gene can be a potential target spot for the treatment of pancreatic cancer.

CD46 Null Packaging Cell Line Improves Measles Lentiviral Vector Production and Gene Delivery to Hematopoietic Stem and Progenitor Cells

Lentiviral vectors (LVs) pseudotyped with the measles virus hemagglutinin (H) and fusion (F) glycoproteins have been reported to more efficiently transduce hematopoietic stem and progenitor cells (HSPCs) compared with vesicular stomatitis virus glycoprotein (VSV-G) pseudotyped LVs. However, a limit to H/F LV use is the low titer of produced vector. Here we show that measles receptor (CD46) expression on H/F transfected HEK293T vector-producing cells caused adjacent cell membrane fusion, resulting in multinucleate syncytia formation and death prior to peak vector production, leading to contaminating cell membranes that co-purified with LV. H/F LVs produced in CD46 null HEK293T cells, generated by CRISPR/Cas9-mediated knockout of CD46, produced 2-fold higher titer vector compared with LVs produced in CD46+ HEK293T cells. This resulted in approximately 2- to 3-fold higher transduction of HSPCs while significantly reducing target cell cytotoxicity caused by producer cell contaminates. Improved H/F LV entry into HSPCs and distinct entry mechanisms compared with VSV-G LV were also observed by confocal microscopy. Given that vector production is a major source of cost and variability in clinical trials of gene therapy, we propose that the use of CD46 null packaging cells may help to address these challenges.

Aberrant Clonal Hematopoiesis following Lentiviral Vector Transduction of HSPCs in a Rhesus Macaque

Lentiviral vectors (LVs) are used for delivery of genes into hematopoietic stem and progenitor cells (HSPCs) in clinical trials worldwide. LVs, in contrast to retroviral vectors, are not associated with insertion site-associated malignant clonal expansions and, thus, are considered safer. Here, however, we present a case of markedly abnormal dysplastic clonal hematopoiesis affecting the erythroid, myeloid, and megakaryocytic lineages in a rhesus macaque transplanted with HSPCs that were transduced with a LV containing a strong retroviral murine stem cell virus (MSCV) constitutive promoter-enhancer in the LTR. Nine insertions were mapped in the abnormal clone, resulting in overexpression and aberrant splicing of several genes of interest, including the cytokine stem cell factor and the transcription factor PLAG1. This case represents the first clear link between lentiviral insertion-induced clonal expansion and a clinically abnormal transformed phenotype following transduction of normal primate or human HSPCs, which is concerning, and suggests that strong constitutive promoters should not be included in LVs.

Lentiviral Vectors for the Treatment and Prevention of Cystic Fibrosis Lung Disease

Despite the continued development of cystic fibrosis transmembrane conductance regulator (CFTR) modulator drugs for the treatment of cystic fibrosis (CF), the need for mutation agnostic treatments remains. In a sub-group of CF individuals with mutations that may not respond to modulators, such as those with nonsense mutations, CFTR gene transfer to airway epithelia offers the potential for an effective treatment. Lentiviral vectors are well-suited for this purpose because they transduce nondividing cells, and provide long-term transgene expression. Studies in primary cultures of human CF airway epithelia and CF animal models demonstrate the long-term correction of CF phenotypes and low immunogenicity using lentiviral vectors. Further development of CF gene therapy requires the investigation of optimal CFTR expression in the airways. Lentiviral vectors with improved safety features have minimized insertional mutagenesis safety concerns raised in early clinical trials for severe combined immunodeficiency using γ-retroviral vectors. Recent clinical trials using improved lentiviral vectors support the feasibility and safety of lentiviral gene therapy for monogenetic diseases. While work remains to be done before CF gene therapy reaches the bedside, recent advances in lentiviral vector development reviewed here are encouraging and suggest it could be tested in clinical studies in the near future.

Genetic engineering of hematopoiesis: current stage of clinical translation and future perspectives

Here I review the scientific background, current stage of development and future perspectives that I foresee in the field of genetic manipulation of hematopoietic stem cells with a special emphasis on clinical applications.

Lentiviral transduction of mammalian cells for fast, scalable and high-level production of soluble and membrane proteins

Structural, biochemical and biophysical studies of eukaryotic soluble and membrane proteins require their production in milligram quantities. Although large-scale protein expression strategies based on transient or stable transfection of mammalian cells are well established, they are associated with high consumable costs, limited transfection efficiency or long and tedious selection of clonal cell lines. Lentiviral transduction is an efficient method for the delivery of transgenes to mammalian cells and unifies the ease of use and speed of transient transfection with the robust expression of stable cell lines. In this protocol, we describe the design and step-by-step application of a lentiviral plasmid suite, termed pHR-CMV-TetO2, for the constitutive or inducible large-scale production of soluble and membrane proteins in HEK293 cell lines. Optional features include bicistronic co-expression of fluorescent marker proteins for enrichment of co-transduced cells using cell sorting and of biotin ligase for in vivo biotinylation. We demonstrate the efficacy of the method for a set of soluble proteins and for the G-protein-coupled receptor (GPCR) Smoothened (SMO). We further compare this method with baculovirus transduction of mammalian cells (BacMam), using the type-A γ-aminobutyric acid receptor (GABAAR) β3 homopentamer as a test case. The protocols described here are optimized for simplicity, speed and affordability; lead to a stable polyclonal cell line and milligram-scale amounts of protein in 3-4 weeks; and routinely achieve an approximately three- to tenfold improvement in protein production yield per cell as compared to transient transduction or transfection.

Gene therapy for mucopolysaccharidoses: in vivo and ex vivo approaches

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by a deficiency in lysosomal enzymes catalyzing the stepwise degradation of glycosaminoglycans (GAGs). The current therapeutic strategies of enzyme replacement therapy and allogeneic hematopoietic stem cell transplantation have been reported to reduce patient morbidity and to improve their quality of life, but they are associated with persistence of residual disease burden, in particular at the neurocognitive and musculoskeletal levels. This indicates the need for more efficacious treatments capable of effective and rapid enzyme delivery to the affected organs, especially the brain and the skeleton. Gene therapy (GT) strategies aimed at correcting the genetic defect in patient cells could represent a significant improvement for the treatment of MPS when compared with conventional approaches. While in-vivo GT strategies foresee the administration of viral vector particles directly to patients with the aim of providing normal complementary DNA to the affected cells, ex-vivo GT approaches are based on the ex-vivo transduction of patient cells that are subsequently infused back. This review provides insights into the state-of-art accomplishments made with in vivo and ex vivo GT-based approaches in MPS and provide a vision for the future in the medical community.

In vivo generation of human CD19-CAR T cells results in B-cell depletion and signs of cytokine release syndrome

Chimeric antigen receptor (CAR) T cells brought substantial benefit to patients with B-cell malignancies. Notwithstanding, CAR T-cell manufacturing requires complex procedures impeding the broad supply chain. Here, we provide evidence that human CD19-CAR T cells can be generated directly in vivo using the lentiviral vector CD8-LV specifically targeting human CD8+ cells. Administration into mice xenografted with Raji lymphoma cells and human peripheral blood mononuclear cells led to CAR expression solely in CD8+ T cells and efficacious elimination of CD19+ B cells. Further, upon injection of CD8-LV into mice transplanted with human CD34+ cells, induction of CAR T cells and CD19+ B-cell depletion was observed in 7 out of 10 treated animals. Notably, three mice showed elevated levels of human cytokines in plasma. Tissue-invading CAR T cells and complete elimination of the B-lymphocyte-rich zones in spleen were indicative of a cytokine release syndrome. Our data demonstrate the feasibility of in vivo reprogramming of human CD8+ CAR T cells active against CD19+ cells, yet with similar adverse effects currently notorious in the clinical practice.

Versatile targeting system for lentiviral vectors involving biotinylated targeting molecules

Conjugating certain types of lentiviral vectors with targeting ligands can redirect the vectors to specifically transduce desired cell types. However, extensive genetic and/or biochemical manipulations are required for conjugation, which hinders applications for targeting lentiviral vectors for broader research fields. We developed envelope proteins fused with biotin-binding molecules to conjugate the pseudotyped vectors with biotinylated targeting molecules by simply mixing them. The envelope proteins fused with the monomeric, but not tetrameric, biotin-binding molecules can pseudotype lentiviral vectors and be conjugated with biotinylated targeting ligands. The conjugation is stable enough to redirect lentiviral transduction in the presence of serum, indicating their potential in in vivo . When a signaling molecule is conjugated with the vector, the conjugation facilitates transduction and signaling in a receptor-specific manner. This simple method of ligand conjugation and ease of obtaining various types of biotinylated ligands will make targeted lentiviral transduction easily applicable to broad fields of research.

Immune Cell Hacking: Challenges and Clinical Approaches to Create Smarter Generations of Chimeric Antigen Receptor T Cells

T cells equipped with chimeric antigen receptors (CAR T cells) have recently provided promising advances as a novel immunotherapeutic approach for cancer treatment. CAR T cell therapy has shown stunning results especially in B-cell malignancies; however, it has shown less success against solid tumors, which is more supposed to be related to the specific characteristics of the tumor microenvironment. In this review, we discuss the structure of the CAR, current clinical advantages from finished and ongoing trials, adverse effects, challenges and controversies, new engineering methods of CAR, and clinical considerations that are associated with CAR T cell therapy both in hematological malignancies and solid tumors. Also, we provide a comprehensive description of recently introduced modifications for designing smarter models of CAR T cells. Specific hurdles and problems that limit the optimal function of CAR T cells, especially on solid tumors, and possible solutions according to new modifications and generations of CAR T cells have been introduced here. We also provide information of the future directions on how to enhance engineering the next smarter generations of CAR T cells in order to decrease the adverse effects and increase the potency and efficacy of CAR T cells against cancer.

UM171 Enhances Lentiviral Gene Transfer and Recovery of Primitive Human Hematopoietic Cells

Enhanced gene transfer efficiencies and higher yields of transplantable transduced human hematopoietic stem cells are continuing goals for improving clinical protocols that use stemcell-based gene therapies. Here, we examined the effect of the HSC agonist UM171 on these endpoints in both in vitro and in vivo systems. Using a 22-hr transduction protocol, we found that UM171 significantly enhances both the lentivirus-mediated transduction and yield of CD34⁺ and CD34⁺CD45RA^- hematopoietic cells from human cord blood to give a 6-fold overall higher recovery of transduced hematopoietic stem cells, including cells with long-term lympho-myeloid repopulating activity in immunodeficient mice. The ability of UM171 to enhance gene transfer to primitive cord blood hematopoietic cells extended to multiple lentiviral pseudotypes, gamma retroviruses, and non-integrating lentiviruses and to adult bone marrow cells. UM171, thus, provides an interesting reagent for improving the ex vivo production of gene-modified cells and for reducing requirements of virus for a broad range of applications.

Hematopoietic stem cell transplantation in its 60s: A platform for cellular therapies

Over the last 60 years, more than a million patients received hematopoietic cell transplantation. Having incorporated multiple changes in clinical practices, it remains a complex procedure facing a dual challenge: cure of the underlying disease and prevention of relapse while controlling potentially severe complications. Improved understanding of underlying biological processes resulted in the design of innovative therapies engineered from defined cell populations and testing of these therapies as addition or substitution at virtually every step of the procedure. This review provides an overview of these developments, many of them now applied outside the historical field of hematopoietic cell transplantation.

GDNF-expressing macrophages mitigate loss of dopamine neurons and improve Parkinsonian symptoms in MitoPark mice

Glial cell line-derived neurotrophic factor (GDNF) is the most potent neuroprotective agent tested in cellular and animal models of Parkinson's disease (PD). However, CNS delivery of GDNF is restricted by the blood-brain barrier (BBB). Using total body irradiation as transplant preconditioning, we previously reported that hematopoietic stem cell (HSC) transplantation (HSCT)-based macrophage-mediated gene therapy could deliver GDNF to the brain to prevent degeneration of nigrostriatal dopamine (DA) neurons in an acute murine neurotoxicity model. Here, we validate this therapeutic approach in a chronic progressive PD model - the MitoPark mouse, with head shielding to avoid inducing neuroinflammation and compromising BBB integrity. Bone marrow HSCs were transduced ex vivo with a lentiviral vector expressing macrophage promoter-driven GDNF and transplanted into MitoPark mice exhibiting well developed PD-like impairments. Transgene-expressing macrophages infiltrated the midbrains of MitoPark mice, but not normal littermates, and delivered GDNF locally. Macrophage GDNF delivery markedly improved both motor and non-motor symptoms, and dramatically mitigated the loss of both DA neurons in the substantia nigra and tyrosine hydroxylase-positive axonal terminals in the striatum. Our data support further development of this HSCT-based macrophage-mediated GDNF delivery approach in order to address the unmet need for a disease-modifying therapy for PD.

Integrated Method for Purification and Single-Particle Characterization of Lentiviral Vector Systems by Size Exclusion Chromatography and Tunable Resistive Pulse Sensing

Elements derived from lentiviral particles such as viral vectors or virus-like particles are commonly used for biotechnological and biomedical applications, for example in mammalian protein expression, gene delivery or therapy, and vaccine development. Preparations of high purity are necessary in most cases, especially for clinical applications. For purification, a wide range of methods are available, from density gradient centrifugation to affinity chromatography. In this study we have employed size exclusion columns specifically designed for the easy purification of extracellular vesicles including exosomes. In addition to viral marker protein and total protein analysis, a well-established single-particle characterization technology, termed tunable resistive pulse sensing, was employed to analyze fractions of highest particle load and purity and characterize the preparations by size and surface charge/electrophoretic mobility. With this study, we propose an integrated platform combining size exclusion chromatography and tunable resistive pulse sensing for monitoring production and purification of viral particles.

The Pharmacology of T Cell Therapies

Adoptive cellular therapy using T cells with tumor specificity derived from either natural T cell receptors (TCRs) or an artificial chimeric antigen receptor (CAR) has reached late phase clinical testing, with two CAR T cell therapies achieving regulatory approval within the United States in 2017. The effective use of these therapies depends upon an understanding of their pharmacology, which is quite divergent from traditional small molecule or biologic drugs. We review the different types of T cell therapy under clinical development, the factors affecting cellular kinetics following infusion, and the relationship between these cellular kinetics and anti-cancer activity. We also discuss the toxicity associated with T cell therapies, with an emphasis on cytokine release syndrome and neurotoxicity, and the gaps in knowledge regarding these frequent and unique adverse effects.

Gene therapy comes of age

After almost 30 years of promise tempered by setbacks, gene therapies are rapidly becoming a critical component of the therapeutic armamentarium for a variety of inherited and acquired human diseases. Gene therapies for inherited immune disorders, hemophilia, eye and neurodegenerative disorders, and lymphoid cancers recently progressed to approved drug status in the United States and Europe, or are anticipated to receive approval in the near future. In this Review, we discuss milestones in the development of gene therapies, focusing on direct in vivo administration of viral vectors and adoptive transfer of genetically engineered T cells or hematopoietic stem cells. We also discuss emerging genome editing technologies that should further advance the scope and efficacy of gene therapy approaches.

Gene Therapy and Genome Editing

The β-thalassemias are inherited blood disorders that result from insufficient production of the β-chain of hemoglobin. More than 200 different mutations have been identified. β-Thalassemia major requires life-long transfusions. The only cure for severe β-thalassemia is to provide patients with hematopoietic stem cells. Globin gene therapy promises a curative autologous stem cell transplantation without the immunologic complications of allogeneic transplantation. The future directions of gene therapy include enhancement of lentiviral vector-based approaches, fine tuning of the conditioning regimen, and the design of safer vectors. Progress in genetic engineering bodes well for finding a cure for severe globin disorders.

High-efficiency transduction of spinal cord motor neurons by intrauterine delivery of integration-deficient lentiviral vectors

Integration-deficient lentiviral vectors (IDLVs) are promising gene delivery tools that retain the high transduction efficiency of standard lentiviral vectors, yet fail to integrate as proviruses and are instead converted into episomal circles. These episomes are metabolically stable and support long-term expression of transgenes in non-dividing cells, exhibiting a decreased risk of insertional mutagenesis. We have embarked on an extensive study to compare the transduction efficiency of IDLVs pseudotyped with different envelopes (vesicular stomatitis, Rabies, Mokola and Ross River viral envelopes) and self-complementary adeno-associated viral vectors, serotype-9 (scAAV-9) in spinal cord tissues after intraspinal injection of mouse embryos (E16). Our results indicate that IDLVs can transduce motor neurons (MNs) at extremely high efficiency regardless of the envelope pseudotype while scAAV9 mediates gene delivery to ~ 40% of spinal cord motor neurons, with other non-neuronal cells also transduced. Long-term expression studies revealed stable gene expression at 7 months post-injection. Taken together, the results of this study indicate that IDLVs may be efficient tools for in utero cord transduction in therapeutic strategies such as for treatment of inherited early childhood neurodegenerative diseases.

Gene Editing and CRISPR Therapeutics: Strategies Taught by Cell and Gene Therapy

A few years ago, we assisted in the demonstration for the first time of the revolutionary idea of a type of adaptive-immune system in the bacteria kingdom. This system, named CRISPR, and variants engineered in the lab, have been demonstrated as functional with extremely high frequency and fidelity in almost all eukaryotic cells studied to date. The capabilities of this RNA-guided nuclease have added to the interest that was announced with the advent of previous technologies for genome editing tools, such as ZFN and TALEN. The capabilities exhibited by these gene editors, opens up a novel scenario that indicates the promise of a next-generation medicine based on precision and personalized objectives, mostly due to the change in the paradigm regarding gene-surgery. This has certainly attracted, like never before, the attention of the biotech business and investor community. This chapter offers a brief overview of some of the factors that have contributed to a rapid entry into the biotech and pharmaceutical company's pipeline, focusing on how cell and gene therapies (CGT), collectively known as advanced therapies, have become the driving forces toward the therapeutic uses of gene editing technology. The sum of all those efforts for more than 30years has contributed to the new paradigm of considering genes as medicines.

The retroviral vector family: something for everyone

After 30 years of retroviral vector research it became clear that the parental viruses can be both friend and foe. Especially human immunodeficiency virus sparked a global pandemic, but could be converted into a versatile tool for cell therapy. For all retroviral genera, the way from virus to vector was similar resulting in split-vector systems based on the separation of the genes needed for vector particle formation and transgene expression. The first gene therapy trials, although clinically effective, revealed the genotoxicity of retroviral vectors caused by insertional mutagenesis. This issue was solved using self-inactivating vectors carrying weaker cellular promoters. Further fine-tuning was able to generate inducible systems. The current toolbox also contains vectors for the generation of induced pluripotent stem cells or efficient RNA interference. More recently the application of CRISPR-Cas9-mediated gene editing led to the development of genome-wide small guide RNA libraries targeting all human genes and single lentiviral vectors for an easy delivery of Cas9.

Reconstructing the immune system with lentiviral vectors

Lentiviral vectors (LVs) developed in the past two decades for research and pre-clinical purposes have entered clinical trials with remarkable safety and efficacy performances. Development and clinical testing of LVs for improvement of human immunity showed major advantages in comparison to other viral vector systems. Robust and persisted transduction efficiency of blood cells with LVs, resulted into a broad range of target cells for immune therapeutic approaches: from hematopoietic stem cells and precursor cells for correction of immune deficiencies, up to effector lymphoid and myeloid cells. T cells engineered for expression of chimeric antigen receptors (CARs) or epitope-specific transgenic T cell receptors (TCRs) are in several cancer immune therapy clinical trials worldwide. Development of engineered dendritic cells is primed for clinical trials for cancer and chronic infections. Technological adaptations for ex vivo cell manipulations are here discussed and presented based on properties and uses of the target cell. For future development of off-shelf immune therapies, direct in vivo administration of lentiviral vectors is warranted and intended. Approaches for lentiviral in vivo targeting to maximize immune therapeutic success are discussed.

New frontiers in the therapy of primary immunodeficiency: From gene addition to gene editing

The most severe primary immune deficiency diseases (PIDs) have been successfully treated with allogeneic hematopoietic stem cell transplantation for more than 4 decades. However, such transplantations have the best outcomes when there is a well-matched donor available because immune complications, such as graft-versus-host disease, are greater without a matched sibling donor. Gene therapy has been developed as a method to perform autologous transplantations of a patient's own stem cells that are genetically corrected. Through an iterative bench-to-bedside-and-back process, methods to efficiently add new copies of the relevant gene to hematopoietic stem cells have led to safe and effective treatments for several PIDs, including forms of severe combined immune deficiency, Wiskott-Aldrich syndrome, and chronic granulomatous disease. New methods for gene editing might allow additional PIDs to be treated by gene therapy because they will allow the endogenous gene to be repaired and expressed under its native regulatory elements, which are essential for genes involved in cell processes of signaling, activation, and proliferation. Gene therapy is providing exciting new treatment options for patients with PIDs, and advances are sure to continue.

Gene therapy for lysosomal storage disorders: recent advances for metachromatic leukodystrophy and mucopolysaccaridosis I

Lysosomal storage diseases (LSDs) are rare inherited metabolic disorders characterized by a dysfunction in lysosomes, leading to waste material accumulation and severe organ damage. Enzyme replacement therapy (ERT) and haematopoietic stem cell transplant (HSCT) have been exploited as potential treatments for LSDs but pre-clinical and clinical studies have shown in some cases limited efficacy. Intravenous ERT is able to control the damage of visceral organs but cannot prevent nervous impairment. Depending on the disease type, HSCT has important limitations when performed for early variants, unless treatment occurs before disease onset. In the attempt to overcome these issues, gene therapy has been proposed as a valuable therapeutic option, either ex vivo, with target cells genetically modified in vitro, or in vivo, by inserting the genetic material with systemic or intra-parenchymal, in situ administration. In particular, the use of autologous haematopoietic stem cells (HSC) transduced with a viral vector containing a healthy copy of the mutated gene would allow supra-normal production of the defective enzyme and cross correction of target cells in multiple tissues, including the central nervous system. This review will provide an overview of the most recent scientific advances in HSC-based gene therapy approaches for the treatment of LSDs with particular focus on metachromatic leukodystrophy (MLD) and mucopolysaccharidosis type I (MPS-I).

The CRISPR/Cas9 system: Their delivery, in vivo and ex vivo applications and clinical development by startups

The CRISPR/Cas9 gene editing system was originally derived from the prokaryotic adaptive immune system mediated by Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated proteins (Cas). The system has been successfully applied to genome editing in eukaryotes and has contributed to remarkable advances in the life sciences, in areas ranging from agriculture to genetic disease therapies. For efficient editing and extending the influence of this system, proper delivery of its components is crucial. Both viral and nonviral delivery methods are reviewed here, along with the advantages and disadvantages of each. In addition, we review ex vivo and in vivo CRISPR/Cas9 applications for disease therapies. Related remarkable studies are highlighted and relevant startup companies and their drug development pipelines are described. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1035-1045, 2017.

Recent development of synthetic nonviral systems for sustained gene delivery

Sustained gene delivery is of particular importance today because it circumvents the need for repeated therapeutic administration and provides spatial and temporal control of the release profile. Better understanding of the genetic basis of diseases and advances in gene therapy have propelled significant research on biocompatible gene carriers for therapeutic purposes. Varied biodegradable polymer-based architectures have been used to create new compositions with unique properties suitable for sustained gene delivery. This review presents the most recent advances in various polymeric systems: hydrogels, microspheres, nanospheres and scaffolds, having complex architectures to encapsulate and deliver functional genes. Through the recombination of different existing polymer systems, the multicomplex systems can be further endowed with new properties for better-targeted biomedical applications.

Nanotherapy for Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a lethal X-linked childhood muscle wasting disease caused by mutations in the dystrophin gene. Nanobiotechnology-based therapies (such as synthetic nanoparticles and naturally existing viral and nonviral nanoparticles) hold great promise to replace and repair the mutated dystrophin gene and significantly change the disease course. While a majority of DMD nanotherapies are still in early preclinical development, several [such as adeno-associated virus (AAV)-mediated systemic micro-dystrophin gene therapy] are advancing for phase I clinical trials. Recent regulatory approval of Ataluren (a nonsense mutation read-through chemical) in Europe and Exondys51 (an exon-skipping antisense oligonucleotide drug) in the United States shall offer critical insight in how to move DMD nanotherapy to human patients. Progress in novel, optimized nano-delivery systems may further improve emerging molecular therapeutic modalities for DMD. Despite these progresses, DMD nanotherapy faces a number of unique challenges. Specifically, the dystrophin gene is one of the largest genes in the genome while nanoparticles have an inherent size limitation per definition. Furthermore, muscle is the largest tissue in the body and accounts for 40% of the body mass. How to achieve efficient bodywide muscle targeting in human patients with nanomedication remains a significant translational hurdle. New creative approaches in the design of the miniature micro-dystrophin gene, engineering of muscle-specific synthetic AAV capsids, and novel nanoparticle-mediated exon-skipping are likely to result in major breakthroughs in DMD therapy. WIREs Nanomed Nanobiotechnol 2018, 10:e1472. doi: 10.1002/wnan.1472 This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Evolving Gene Therapy in Primary Immunodeficiency

Prior to the first successful bone marrow transplant in 1968, patients born with severe combined immunodeficiency (SCID) invariably died. Today, with a widening availability of newborn screening, major improvements in the application of allogeneic procedures, and the emergence of successful hematopoietic stem and progenitor cell (HSC/P) gene therapy, the majority of these children can be identified and cured. Here, we trace key steps in the development of clinical gene therapy for SCID and other primary immunodeficiencies (PIDs), and review the prospects for adoption of new targets and technologies.

Genome Editing Techniques and Their Therapeutic Applications

Fueled by advances in the field of genetics, the methods available to edit DNA sequences in living cells have continued to develop steadily. These technologies directly impact the fields of gene and cell therapy, where changes in the DNA sequence of target cells offer a route to correct genetic diseases and manipulate disorders like cancer. We review here the expanding menu of genome editing techniques and how they are being applied to therapeutic targets. The methods encompass a myriad of approaches to modify the covalent structure of DNA, including the targeted creation of double-strand breaks that can catalyze genomic changes, as well as the use of retroviruses and transposons to mediate gene addition, recombinases for sequence-specific gene addition and deletion, and base repair for direct sequence changes. The continued growth of the exciting field of genome editing is opening new possibilities for therapeutic intervention.