Genome editing: a tool for research and therapy: targeted genome editing hits the clinic

Baboon Envelope Pseudotyped "Nanoblades" Carrying Cas9/gRNA Complexes Allow Efficient Genome Editing in Human T, B, and CD34+ Cells and Knock-in of AAV6-Encoded Donor DNA in CD34+ Cells

Programmable nucleases have enabled rapid and accessible genome engineering in eukaryotic cells and living organisms. However, their delivery into human blood cells can be challenging. Here, we have utilized "nanoblades," a new technology that delivers a genomic cleaving agent into cells. These are modified murine leukemia virus (MLV) or HIV-derived virus-like particle (VLP), in which the viral structural protein Gag has been fused to Cas9. These VLPs are thus loaded with Cas9 protein complexed with the guide RNAs. Highly efficient gene editing was obtained in cell lines, IPS and primary mouse and human cells. Here, we showed that nanoblades were remarkably efficient for entry into human T, B, and hematopoietic stem and progenitor cells (HSPCs) thanks to their surface co-pseudotyping with baboon retroviral and VSV-G envelope glycoproteins. A brief incubation of human T and B cells with nanoblades incorporating two gRNAs resulted in 40 and 15% edited deletion in the Wiskott-Aldrich syndrome (WAS) gene locus, respectively. CD34⁺ cells (HSPCs) treated with the same nanoblades allowed 30-40% exon 1 drop-out in the WAS gene locus. Importantly, no toxicity was detected upon nanoblade-mediated gene editing of these blood cells. Finally, we also treated HSPCs with nanoblades in combination with a donor-encoding rAAV6 vector resulting in up to 40% of stable expression cassette knock-in into the WAS gene locus. Summarizing, this new technology is simple to implement, shows high flexibility for different targets including primary immune cells of human and murine origin, is relatively inexpensive and therefore gives important prospects for basic and clinical translation in the area of gene therapy.

Gene therapy using haematopoietic stem and progenitor cells

Haematopoietic stem and progenitor cell (HSPC) gene therapy has emerged as an effective treatment modality for monogenic disorders of the blood system such as primary immunodeficiencies and β-thalassaemia. Medicinal products based on autologous HSPCs corrected using lentiviral and gammaretroviral vectors have now been approved for clinical use, and the site-specific genome modification of HSPCs using gene editing techniques such as CRISPR-Cas9 has shown great clinical promise. Preclinical studies have shown engineered HSPCs could also be used to cross-correct non-haematopoietic cells in neurodegenerative metabolic diseases. Here, we review the most recent advances in HSPC gene therapy and discuss emerging strategies for using HSPC gene therapy for a range of diseases.

Targeted Integration and High-Level Transgene Expression in AAVS1 Transgenic Mice after In Vivo HSC Transduction with HDAd5/35++ Vectors

Our goal is the development of in vivo hematopoietic stem cell (HSC) transduction technology with targeted integration. To achieve this, we modified helper-dependent HDAd5/35++ vectors to express a CRISPR/Cas9 specific to the "safe harbor" adeno-associated virus integration site 1 (AAVS1) locus and to provide a donor template for targeted integration through homology-dependent repair. We tested the HDAd-CRISPR + HDAd-donor vector system in AAVS1 transgenic mice using a standard ex vivo HSC gene therapy approach as well as a new in vivo HSC transduction approach that involves HSC mobilization and intravenous HDAd5/35++ injections. In both settings, the majority of treated mice had transgenes (GFP or human γ-globin) integrated into the AAVS1 locus. On average, >60% of peripheral blood cells expressed the transgene after in vivo selection with low-dose O⁶BG/bis-chloroethylnitrosourea (BCNU). Ex vivo and in vivo HSC transduction and selection studies with HDAd-CRISPR + HDAd-globin-donor resulted in stable γ-globin expression at levels that were significantly higher (>20% γ-globin of adult mouse globin) than those achieved in previous studies with a SB100x-transposase-based HDAd5/35++ system that mediates random integration. The ability to achieve therapeutically relevant transgene expression levels after in vivo HSC transduction and selection and targeted integration make our HDAd5/35++-based vector system a new tool in HSC gene therapy.

Intracellular Delivery by Membrane Disruption: Mechanisms, Strategies, and Concepts

Intracellular delivery is a key step in biological research and has enabled decades of biomedical discoveries. It is also becoming increasingly important in industrial and medical applications ranging from biomanufacture to cell-based therapies. Here, we review techniques for membrane disruption-based intracellular delivery from 1911 until the present. These methods achieve rapid, direct, and universal delivery of almost any cargo molecule or material that can be dispersed in solution. We start by covering the motivations for intracellular delivery and the challenges associated with the different cargo types-small molecules, proteins/peptides, nucleic acids, synthetic nanomaterials, and large cargo. The review then presents a broad comparison of delivery strategies followed by an analysis of membrane disruption mechanisms and the biology of the cell response. We cover mechanical, electrical, thermal, optical, and chemical strategies of membrane disruption with a particular emphasis on their applications and challenges to implementation. Throughout, we highlight specific mechanisms of membrane disruption and suggest areas in need of further experimentation. We hope the concepts discussed in our review inspire scientists and engineers with further ideas to improve intracellular delivery.

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.

Genetic engineering in primary human B cells with CRISPR-Cas9 ribonucleoproteins

Genome editing in human cells with targeted nucleases now enables diverse experimental and therapeutic genome engineering applications, but extension to primary human B cells remains limited. Here we report a method for targeted genetic engineering in primary human B cells, utilizing electroporation of CRISPR-Cas9 ribonucleoproteins (RNPs) to introduce gene knockout mutations at protein-coding loci with high efficiencies that in some cases exceeded 80%. Further, we demonstrate knock-in editing of targeted nucleotides with efficiency exceeding 10% through co-delivery of oligonucleotide templates for homology directed repair. We delivered Cas9 RNPs in two distinct in vitro culture systems to achieve editing in both undifferentiated B cells and activated B cells undergoing differentiation, reflecting utility in diverse experimental conditions. In summary, we demonstrate a powerful and scalable research tool for functional genetic studies of human B cell biology that may have further applications in engineered B cell therapeutics.

Cure for thalassemia major - from allogeneic hematopoietic stem cell transplantation to gene therapy

Allogeneic hematopoietic stem cell transplantation has been well established for several decades as gene replacement therapy for patients with thalassemia major, and now offers very high rates of cure for patients who have access to this therapy. Outcomes have improved tremendously over the last decade, even in high-risk patients. The limited data available suggests that the long-term outcome is also excellent, with a >90% survival rate, but for the best results, hematopoietic stem cell transplantation should be offered early, before any end organ damage occurs. However, access to this therapy is limited in more than half the patients by the lack of suitable donors. Inadequate hematopoietic stem cell transplantation services and the high cost of therapy are other reasons for this limited access, particularly in those parts of the world which have a high prevalence of this condition. As a result, fewer than 10% of eligible patients are actually able to avail of this therapy. Other options for curative therapies are therefore needed. Recently, gene correction of autologous hematopoietic stem cells has been successfully established using lentiviral vectors, and several clinical trials have been initiated. A gene editing approach to correct the β-globin mutation or disrupt the BCL11A gene to increase fetal hemoglobin production has also been reported, and is expected to be introduced in clinical trials soon. Curative possibilities for the major hemoglobin disorders are expanding. Providing access to these therapies around the world will remain a challenge.

Hereditary Angioedema as a Metabolic Liver Disorder: Novel Therapeutic Options and Prospects for Cure

Hereditary angioedema (HAE) is a rare autosomal dominant disorder caused by mutations of the SERPING1 or the Factor 12 genes. It is potentially fatal, particularly if not identified at an early stage. Apart from androgens, which are contraindicated in children and in pregnant women, a range of effective, albeit very expensive treatments have recently become available for HAE patients. The cost of these new treatments is beyond the reach of most developing countries. At this time, there is no cure for the disorder. In spite of mutations of the SERPING1 gene, autoimmunity and infections are not prominent features of the condition. Here, we present the argument that HAE should be viewed primarily as a metabolic liver disorder. This conceptual paradigm shift will stimulate basic research and may facilitate new therapeutic approaches to HAE outlined in this paper. We suggest several novel potential treatment options for HAE from the perspectives of clinical immunology, molecular biology, and liver transplantation. Many of these offer the prospect of curing the disorder. The effectiveness of these options is rapidly improving in many cases, and their risks are decreasing. Given the very high costs of treating HAE, some of these curative options may become feasible in the next decade.

A Novel High-Throughput Screening Platform Reveals an Optimized Cytokine Formulation for Human Hematopoietic Progenitor Cell Expansion

The main limitations of hematopoietic cord blood (CB) transplantation, viz, low cell dosage and delayed reconstitution, can be overcome by ex vivo expansion. CB expansion under conventional culture causes rapid cell differentiation and depletion of hematopoietic stem and progenitor cells (HSPCs) responsible for engraftment. In this study, we use combinatorial cell culture technology (CombiCult^®) to identify medium formulations that promote CD133⁺ CB HSPC proliferation while maintaining their phenotypic characteristics. We employed second-generation CombiCult screens that use electrospraying technology to encapsulate CB cells in alginate beads. Our results suggest that not only the combination but also the order of addition of individual components has a profound influence on expansion of specific HSPC populations. Top protocols identified by the CombiCult screen were used to culture human CD133⁺ CB HSPCs on nanofiber scaffolds and validate the expansion of the phenotypically defined CD34⁺CD38^lo/-CD45RA^-CD90⁺CD49f⁺ population of hematopoietic stem cells and their differentiation into defined progeny.

Multilineage polyclonal engraftment of Cal-1 gene-modified cells and in vivo selection after SHIV infection in a nonhuman primate model of AIDS

We have focused on gene therapy approaches to induce functional cure/remission of HIV-1 infection. Here, we evaluated the safety and efficacy of the clinical grade anti-HIV lentiviral vector, Cal-1, in pigtailed macaques (Macaca nemestrina). Cal-1 animals exhibit robust levels of gene marking in myeloid and lymphoid lineages without measurable adverse events, suggesting that Cal-1 transduction and autologous transplantation of hematopoietic stem cells are safe, and lead to long-term, multilineage engraftment following myeloablative conditioning. Ex vivo, CD4+ cells from transplanted animals undergo positive selection in the presence of simian/human immunodeficiency virus (SHIV). In vivo, Cal-1 gene-marked cells are evident in the peripheral blood and in HIV-relevant tissue sites such as the gastrointestinal tract. Positive selection for gene-marked cells is observed in blood and tissues following SHIV challenge, leading to maintenance of peripheral blood CD4+ T-cell counts in a normal range. Analysis of Cal-1 lentivirus integration sites confirms polyclonal engraftment of gene-marked cells. Following infection, a polyclonal, SHIV-resistant clonal repertoire is established. These findings offer strong preclinical evidence for safety and efficacy of Cal-1, present a new method for tracking protected cells over the course of virus-mediated selective pressure in vivo, and reveal previously unobserved dynamics of virus-dependent T-cell selection.

Neurogenethics: An emerging discipline at the intersection of ethics, neuroscience, and genomics

The analysis of ethical, legal, and social implications (ELSI) associated with genetics ("genethics") has focused on traditional concerns in bioethics, such as privacy and informed consent. The analysis of ELSI associated with neuroscience ("neuroethics") has focused on concerns related to personhood, such as free will or cognitive enhancement. With neurogenomics coming of age, this is an appropriate time to attend to the set of novel concerns that arises when we consider the confluence of these two lines of research. I call this area of ethics inquiry "neurogenethics", map out the problem space, and highlight future areas of inquiry related to genome editing and gene therapy, optogenetics and memory manipulation, and genomic identity and online communities.

Innovative therapeutic strategies for recessive dystrophic epidermolysis bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is among the most serious rare skin diseases. It is also the rare skin disease for which most effort has been expended in developing advanced therapeutic interventions. RDEB is caused by collagen VII deficiency resulting from COL7A1 mutations. Therapeutic approaches seek to replenish collagen VII and thus restore dermal-epidermal adhesion. Therapeutic options under development include protein therapy and different cell-based and gene-based therapies. In addition to treating skin defects, some of these therapies may also target internal mucosa. In the coming years, these novel therapeutic approaches should substantially improve the quality of life of patients with RDEB.