High-level transduction and gene expression in hematopoietic repopulating cells using a human immunodeficiency [correction of imunodeficiency] virus type 1-based lentiviral vector containing an internal spleen focus forming virus promoter

Three dimensional in vitro models of cancer: Bioprinting multilineage glioblastoma models

Three dimensional (3D) bioprinting of multiple cell types within optimised extracellular matrices has the potential to more closely model the 3D environment of human physiology and disease than current alternatives. In this study, we used a multi-nozzle extrusion bioprinter to establish models of glioblastoma made up of cancer and stromal cells printed within matrices comprised of alginate modified with RGDS cell adhesion peptides, hyaluronic acid and collagen-1. Methods were developed using U87MG glioblastoma cells and MM6 monocyte/macrophages, whilst more disease relevant constructs contained glioblastoma stem cells (GSCs), co-printed with glioma associated stromal cells (GASCs) and microglia. Printing parameters were optimised to promote cell-cell interaction, avoiding the 'caging in' of cells due to overly dense cross-linking. Such printing had a negligible effect on cell viability, and cells retained robust metabolic activity and proliferation. Alginate gels allowed the rapid recovery of printed cell protein and RNA, and fluorescent reporters provided analysis of protein kinase activation at the single cell level within printed constructs. GSCs showed more resistance to chemotherapeutic drugs in 3D printed tumour constructs compared to 2D monolayer cultures, reflecting the clinical situation. In summary, a novel 3D bioprinting strategy is developed which allows control over the spatial organisation of tumour constructs for pre-clinical drug sensitivity testing and studies of the tumour microenvironment.

Rare missense variants in the human cytosolic antibody receptor preserve antiviral function

The genetic basis of most human disease cannot be explained by common variants. One solution to this ‘missing heritability problem’ may be rare missense variants, which are individually scarce but collectively abundant. However, the phenotypic impact of rare variants is under-appreciated as gene function is normally studied in the context of a single ‘wild-type’ sequence. Here, we explore the impact of naturally occurring missense variants in the human population on the cytosolic antibody receptor TRIM21, using volunteer cells with variant haplotypes, CRISPR gene editing and functional reconstitution. In combination with data from a panel of computational predictors, the results suggest that protein robustness and purifying selection ensure that function is remarkably well-maintained despite coding variation.

TRIM69 Inhibits Vesicular Stomatitis Indiana Virus

Vesicular stomatitis Indiana virus (VSIV) is a veterinary pathogen that is also used as a backbone for many oncolytic and vaccine strategies. In natural and therapeutic settings, viral infections like VSIV are sensed by the host, and as a result the host cells make proteins that can protect them from viruses. In the case of VSIV, these antiviral proteins constrain viral replication and protect most healthy tissues from virus infection. In order to understand how VSIV causes disease and how healthy tissues are protected from VSIV-based therapies, it is crucial that we identify the proteins that inhibit VSIV. Here, we show that TRIM69 is an antiviral defense that can potently and specifically block VSIV infection.

Vesicular stomatitis Indiana virus (VSIV), formerly known as vesicular stomatitis virus (VSV) Indiana (VSV_IND), is a model virus that is exceptionally sensitive to the inhibitory action of interferons (IFNs). Interferons induce an antiviral state by stimulating the expression of hundreds of interferon-stimulated genes (ISGs). These ISGs can constrain viral replication, limit tissue tropism, reduce pathogenicity, and inhibit viral transmission. Since VSIV is used as a backbone for multiple oncolytic and vaccine strategies, understanding how ISGs restrict VSIV not only helps in understanding VSIV-induced pathogenesis but also helps us evaluate and understand the safety and efficacy of VSIV-based therapies. Thus, there is a need to identify and characterize the ISGs that possess anti-VSIV activity. Using arrayed ISG expression screening, we identified TRIM69 as an ISG that potently inhibits VSIV. This inhibition was highly specific as multiple viruses, including influenza A virus, HIV-1, Rift Valley fever virus, and dengue virus, were unaffected by TRIM69. Indeed, just one amino acid substitution in VSIV can govern sensitivity/resistance to TRIM69. Furthermore, TRIM69 is highly divergent in human populations and exhibits signatures of positive selection that are consistent with this gene playing a key role in antiviral immunity. We propose that TRIM69 is an IFN-induced inhibitor of VSIV and speculate that TRIM69 could be important in limiting VSIV pathogenesis and might influence the specificity and/or efficacy of vesiculovirus-based therapies.

IMPORTANCE Vesicular stomatitis Indiana virus (VSIV) is a veterinary pathogen that is also used as a backbone for many oncolytic and vaccine strategies. In natural and therapeutic settings, viral infections like VSIV are sensed by the host, and as a result the host cells make proteins that can protect them from viruses. In the case of VSIV, these antiviral proteins constrain viral replication and protect most healthy tissues from virus infection. In order to understand how VSIV causes disease and how healthy tissues are protected from VSIV-based therapies, it is crucial that we identify the proteins that inhibit VSIV. Here, we show that TRIM69 is an antiviral defense that can potently and specifically block VSIV infection.

A Composite Hydrogel Scaffold Permits Self-Organization and Matrix Deposition by Cocultured Human Glomerular Cells

3D scaffolds provide cells with a spatial environment that more closely resembles that of in vivo tissue, when compared to 2D culture on a plastic substrate. However, many scaffolding materials commonly used in tissue engineering tend to exhibit anisotropic morphologies that exhibit a narrow range of fiber diameters and pore sizes, which do not recapitulate extracellular matrices. In this study, a fibrin hydrogel is formed within the interstitial spaces of an electrospun poly(glycolic) acid (PGA) monolith to generate a composite, bimodal scaffold for the coculture of kidney glomerular cell lines. This new scaffold exhibits multiple fiber morphologies, containing both PGA microfibers (14.5 ± 2 µm) and fibrin gel nanofibers (0.14 ± 0.09 µm), which increase the compressive Young's modulus beyond that of either of the constituents. The composite structure provides an enhanced 3D environment that increases proliferation and adhesion of immortalized human podocytes and glomerular endothelial cells. Moreover, the micro/nanoscale fibrous morphology promotes motility and reorganization of the glomerular cells into glomerulus-like structures, resulting in the deposition of organized collagen IV; the primary component of the glomerular basement membrane (GBM).

Pacemaker cell characteristics of differentiated and HCN4-transduced human mesenchymal stem cells

AIMS

Cell-based biological pacemakers aim to overcome limitations and side effects of electronic pacemaker devices. We here developed and tested different approaches to achieve nodal-type differentiation using human adipose- and bone marrow-derived mesenchymal stem cells (haMSC, hbMSC).

MAIN METHODS

haMSC and hbMSC were differentiated using customized protocols. Quantitative RT-PCR was applied for transcriptional pacemaker-gene profiling. Protein membrane expression was analyzed by immunocytochemistry. Pacemaker current (I_f) was studied in haMSC with and without lentiviral HCN4-transduction using patch clamp recordings. Functional characteristics were evaluated by co-culturing with neonatal rat ventricular myocytes (NRVM).

KEY FINDINGS

Culture media-based differentiation for two weeks generated cells with abundant transcription of ion channel genes (Ca_v1.2, NCX1), transcription factors (TBX3, TBX18, SHOX2) and connexins (Cx31.9 and Cx45) characteristic for cardiac pacemaker tissue, but lack adequate HCN transcription. haMSC-derived cells revealed transcript levels, which were closer related to sinoatrial nodal cells than hbMSC-derived cells. To substitute for the lack of I_f, we performed lentiviral HCN4-transduction of haMSC resulting in stable I_f. Co-culturing with NRVM demonstrated that differentiated haMSC expressing HCN4 showed earlier onset of spontaneous contractions and higher beating regularity, synchrony and rate compared to co-cultures with non-HCN4-transduced haMSC or HCN4-transduced, non-differentiated haMSC. Confocal imaging indicated increased membrane expression of cardiac gap junctional proteins in differentiated haMSC.

SIGNIFICANCE

By differentiation haMSC, rather than hbMSC attain properties favorable for cardiac pacemaking. In combination with lentiviral HCN4-transduction, a cellular phenotype was generated that sustainably controls and stabilizes rate in co-culture with NRVM.

Rational targeting of a NuRD subcomplex guided by comprehensive in situ mutagenesis

Developmental silencing of fetal globins serves as both a paradigm of spatiotemporal gene regulation and an opportunity for therapeutic intervention of β-hemoglobinopathy. The nucleosome remodeling and deacetylase (NuRD) chromatin complex participates in γ-globin repression. We used pooled CRISPR screening to disrupt NuRD protein coding sequences comprehensively in human adult erythroid precursors. Essential for fetal hemoglobin (HbF) control is a non-redundant subcomplex of NuRD protein family paralogs, whose composition we corroborated by affinity chromatography and proximity labeling mass spectrometry proteomics. Mapping top functional guide RNAs identified key protein interfaces where in-frame alleles resulted in loss-of-function due to destabilization or altered function of subunits. We ascertained mutations of CHD4 that dissociate its requirement for cell fitness from HbF repression in both primary human erythroid precursors and transgenic mice. Finally we demonstrated that sequestering CHD4 from NuRD phenocopied these mutations. These results indicate a generalizable approach to discover protein complex features amenable to rational biochemical targeting.

Expression Cloning of Host Factors Required for the HCV Replication Cycle

Chronic infection with the hepatitis C virus (HCV) is a common cause of chronic liver disease, cirrhosis, and liver cancer. Like most viruses, HCV depends of a number of factors encoded by its host cell to execute its replication cycle and create. Expression cloning is one of several possible approaches that have been employed to identify novel host factors essential for the HCV replication cycle. It involves generation of a cDNA library from a cell type with a desired trait (such as ability to bind E2 or being susceptible to HCV infection), expression of that library in a different cell type missing the trait of interest, and selection for cell clones that have acquired that trait through expression of a specific cDNA. This chapter describes an expression cloning approach similar to the one that was used to identify the tight junction component claudin-1 as an essential HCV cell entry factor.

The AAA+ATPase RUVBL2 is essential for the oncogenic function of c-MYB in acute myeloid leukemia

Subtype-specific leukemia oncogenes drive aberrant gene expression profiles that converge on common essential mediators to ensure leukemia self-renewal and inhibition of differentiation. The transcription factor c-MYB functions as one such mediator in a diverse range of leukemias. Here we show for the first time that transcriptional repression of myeloid differentiation associated c-MYB target genes in AML is enforced by the AAA+ ATPase RUVBL2. Silencing RUVBL2 expression resulted in increased binding of c-MYB to these loci and their transcriptional activation. RUVBL2 inhibition resulted in AML cell apoptosis and severely impaired disease progression of established AML in engrafted mice. In contrast, such inhibition had little impact on normal hematopoietic progenitor differentiation. These data demonstrate that RUVBL2 is essential for the oncogenic function of c-MYB in AML by governing inhibition of myeloid differentiation. They also indicate that targeting the control of c-MYB function by RUVBL2 is a promising approach to developing future anti-AML therapies.

Exosomes-mediated transmission of foot-and-mouth disease virus in vivo and in vitro

Exosomes are small membrane-enclosed vesicles that participate in intercellular communication between cells. Numerous evidences suggested that exosomes derived from virus-infected cells can mediate virus transmission or/and regulate immune response. Foot-and-mouth disease virus (FMDV) is the prototype member of the Aphthovirus genus of the Picornaviridae family. It can cause highly infectious disease of cloven-hoofed livestock and significantly increase public awareness. However, the role of exosomes in the transmission of FMDV has still remained unknown. In this study, full length of FMDV genomic RNA and partial viral proteins were identified in purified exosomes isolated from FMDV-infected PK-15 cells with qRT-PCR and /MS. Exosomes from FMDV-infected cells were capable of transmitting infection to naive PK-15 cells and suckling mice. Furthermore, exosome-mediated infection cannot be fully blocked by FMDV-specific neutralizing antibodies. This finding highlights that FMDV transmission by exosomes as a potential immune evasion mechanism.

ER intrabody-mediated inhibition of interferon α secretion by mouse macrophages and dendritic cells

Interferon α (IFNα) counteracts viral infections by activating various IFNα-stimulated genes (ISGs). These genes encode proteins that block viral transport into the host cell and inhibit viral replication, gene transcription and translation. Due to the existence of 14 different, highly homologous isoforms of mouse IFNα, an IFNα knockout mouse has not yet been established by genetic knockout strategies. An scFv intrabody for holding back IFNα isoforms in the endoplasmic reticulum (ER) and thus counteracting IFNα secretion is reported. The intrabody was constructed from the variable domains of the anti-mouse IFNα rat monoclonal antibody 4EA1 recognizing the 5 isoforms IFNα1, IFNα2, IFNα4, IFNα5, IFNα6.

A soluble form of the intrabody had a K_D of 39 nM to IFNα4. It could be demonstrated that the anti-IFNα intrabody inhibits clearly recombinant IFNα4 secretion by HEK293T cells. In addition, the secretion of IFNα4 was effectively inhibited in stably transfected intrabody expressing RAW 264.7 macrophages and dendritic D1 cells. Colocalization of the intrabody with IFNα4 and the ER marker calnexin in HEK293T cells indicated complex formation of intrabody and IFNα4 inside the ER. Intracellular binding of intrabody and antigen was confirmed by co-immunoprecipitation. Complexes of endogenous IFNα and intrabody could be visualized in the ER of Poly (I:C) stimulated RAW 264.7 macrophages and D1 dendritic cells. Infection of macrophages and dendritic cells with the vesicular stomatitis virus VSV-AV2 is attenuated by IFNα and IFNβ. The intrabody increased virus proliferation in RAW 264.7 macrophages and D1 dendritic cells under IFNβ-neutralizing conditions. To analyze if all IFNα isoforms are recognized by the intrabody was not in the focus of this study. Provided that binding of the intrabody to all isoforms was confirmed, the establishment of transgenic intrabody mice would be promising for studying the function of IFNα during viral infection and autoimmune diseases.

ADAM17-dependent proteolysis of L-selectin promotes early clonal expansion of cytotoxic T cells

L-selectin on T-cells is best known as an adhesion molecule that supports recruitment of blood-borne naïve and central memory cells into lymph nodes. Proteolytic shedding of the ectodomain is thought to redirect activated T-cells from lymph nodes to sites of infection. However, we have shown that activated T-cells re-express L-selectin before lymph node egress and use L-selectin to locate to virus-infected tissues. Therefore, we considered other roles for L-selectin proteolysis during T cell activation. In this study, we used T cells expressing cleavable or non-cleavable L-selectin and determined the impact of L-selectin proteolysis on T cell activation in virus-infected mice. We confirm an essential and non-redundant role for ADAM17 in TCR-induced proteolysis of L-selectin in mouse and human T cells and show that L-selectin cleavage does not regulate T cell activation measured by CD69 or TCR internalisation. Following virus infection of mice, L-selectin proteolysis promoted early clonal expansion of cytotoxic T cells resulting in an 8-fold increase over T cells unable to cleave L-selectin. T cells unable to cleave L-selectin showed delayed proliferation in vitro which correlated with lower CD25 expression. Based on these results, we propose that ADAM17-dependent proteolysis of L-selectin should be considered a regulator of T-cell activation at sites of immune activity.

Formation of three-dimensional tubular endothelial cell networks under defined serum-free cell culture conditions in human collagen hydrogels

Implementation of tubular endothelial cell networks is a prerequisite for 3D tissue engineering of constructs with clinically relevant size as nourishment of cells is challenged by the diffusion limit. In vitro generation of 3D networks is often achieved under conditions using serum containing cell culture medium and/or animal derived matrices. Here, 3D endothelial cell networks were generated by using human umbilical vein endothelial cells (HUVECs) in combination with human adipose tissue derived stromal cells (hASCs) employing human collagen I as hydrogel and decellularized porcine small intestinal submucosa as starter matrix. Matrigel/rat tail collagen I hydrogel was used as control. Resulting constructs were cultivated either in serum-free medium or in endothelial growth medium-2 serving as control. Endothelial cell networks were quantified, tested for lumen formation, and interaction of HUVECs and hASCs. Tube diameter was slightly larger in constructs containing human collagen I compared to Matrigel/rat tail collagen I constructs under serum-free conditions. All other network parameters were mostly similar. Thereby, the feasibility of generating 3D endothelial cell networks under serum-free culture conditions in human collagen I as hydrogel was demonstrated. In summary, the presented achievements pave the way for the generation of clinical applicable constructs.

Genetically engineered CAR NK cells display selective cytotoxicity against FLT3-positive B-ALL and inhibit in vivo leukemia growth

Chimeric antigen receptor (CAR)-engineered natural killer (NK) cells represent a promising effector cell type for adoptive cancer immunotherapy. Both, genetically modified donor-derived NK cells as well as continuously expanding NK-92 cells are currently under clinical development. To enhance their therapeutic utility for the treatment of pre-B-cell acute lymphoblastic leukemia (B-ALL), we engineered NK-92 cells by lentiviral gene transfer to express a FMS-like tyrosine kinase 3 (FLT3)-specific CAR that contains a composite CD28-CD3ζ signaling domain. FLT3 has primarily been described as a therapeutic target for acute myeloid leukemia, but overexpression of FLT3 has also been reported in B-ALL. Exposure of FLT3-positive targets to CAR NK-92 cells resulted in conjugate formation between NK and leukemia cells, NK-cell degranulation and selective cytotoxicity toward established B-ALL cell lines and primary blasts that were resistant to parental NK-92. In a SEM B-ALL xenograft model in NOD-SCID IL2R γ^null mice, treatment with CAR NK-92 but not parental NK-92 cells markedly inhibited disease progression, demonstrating high antileukemic activity in vivo. As FLT3 is known to be also expressed on precursor cells, we assessed the feasibility of incorporating an inducible caspase-9 (iCasp9) suicide switch to enhance safety of our approach. Upon addition of the chemical dimerizer AP20187 to NK-92 cells coexpressing the FLT3-specific CAR and iCasp9, rapid iCasp9 activation was observed, precluding further CAR-mediated cytotoxicity. Our data demonstrate that B-ALL can be effectively targeted by FLT3-specific CAR NK cells which may complement CD19-directed immunotherapies, particularly in cases of inherent or acquired resistance to the latter.

Tolerizing CTL by Sustained Hepatic PD-L1 Expression Provides a New Therapy Approach in Mouse Sepsis

Cytotoxic T lymphocyte (CTL) activation contributes to liver damage during sepsis, but the mechanisms involved are largely unknown. Understanding the underlying principle will permit interference with CTL activation and thus, provide a new therapeutic option. Methods: To elucidate the mechanism leading to CTL activation we used the Hepa1-6 cell line in vitro and the mouse model of in vivo polymicrobial sepsis, following cecal-ligation and -puncture (CLP) in wildtype, myeloid specific NOX-2, global NOX2 and NOX4 knockout mice, and their survival as a final readout. In this in vivo setting, we also determined hepatic mRNA and protein expression as well as clinical parameters of liver damage - aspartate- and alanine amino-transaminases. Hepatocyte specific overexpression of PD-L1 was achieved in vivo by adenoviral infection and transposon-based gene transfer using hydrodynamic injection. Results: We observed downregulation of PD-L1 on hepatocytes in the murine sepsis model. Adenoviral and transposon-based gene transfer to restore PD-L1 expression, significantly improved survival and reduced the release of liver damage, as PD-L1 is a co-receptor that negatively regulates T cell function. Similar protection was observed during pharmacological intervention using recombinant PD-L1-Fc. N-acetylcysteine blocked the downregulation of PD-L1 suggesting the involvement of reactive oxygen species. This was confirmed in vivo, as we observed significant upregulation of PD-L1 expression in NOX4 knockout mice, following sham operation, whereas its expression in global as well as myeloid lineage NOX2 knockout mice was comparable to that in the wild type animals. PD-L1 expression remained high following CLP only in total NOX2 knockouts, resulting in significantly reduced release of liver damage markers. Conclusion: These results suggest that, contrary to common assumption, maintaining PD-L1 expression on hepatocytes improves liver damage and survival of mice during sepsis. We conclude that administering recombinant PD-L1 or inhibiting NOX2 activity might offer a new therapeutic option in sepsis.

A single cycle influenza virus coated in H7 haemagglutinin generates neutralizing antibody responses to haemagglutinin and neuraminidase glycoproteins and protection from heterotypic challenge

A non-replicating form of pseudotyped influenza virus, inactivated by suppression of the haemagglutinin signal sequence (S-FLU), can act as a broadly protective vaccine. S-FLU can infect for a single round only, and induces heterotypic protection predominantly through activation of cross-reactive T cells in the lung. Unlike the licensed live attenuated virus, it cannot reassort a pandemic haemagglutinin (HA) into seasonal influenza. Here we present data on four new forms of S-FLU coated with H7 HAs from either A/Anhui/1/2013, A/Shanghai/1/2013, A/Netherlands/219/2003 or A/New York/107/2003 strains of H7 virus. We show that intranasal vaccination induced a strong local CD8 T cell response and protected against heterosubtypic X31 (H3N2) virus and highly virulent PR8 (H1N1), but not influenza B virus. Intranasal vaccination also induced a strong neutralizing antibody response to the encoded neuraminidase. If given at higher dose in the periphery with intraperitoneal administration, H7 S-FLU induced a specific neutralizing antibody response to H7 HA coating the particle. Polyvalent intraperitoneal vaccination with mixed H7 S-FLU induced a broadly neutralizing antibody response to all four H7 strains. S-FLU is a versatile vaccine candidate that could be rapidly mobilized ahead of a new pandemic threat.

The sterol-responsive RNF145 E3 ubiquitin ligase mediates the degradation of HMG-CoA reductase together with gp78 and Hrd1

Mammalian HMG-CoA reductase (HMGCR), the rate-limiting enzyme of the cholesterol biosynthetic pathway and the therapeutic target of statins, is post-transcriptionally regulated by sterol-accelerated degradation. Under cholesterol-replete conditions, HMGCR is ubiquitinated and degraded, but the identity of the E3 ubiquitin ligase(s) responsible for mammalian HMGCR turnover remains controversial. Using systematic, unbiased CRISPR/Cas9 genome-wide screens with a sterol-sensitive endogenous HMGCR reporter, we comprehensively map the E3 ligase landscape required for sterol-accelerated HMGCR degradation. We find that RNF145 and gp78 independently co-ordinate HMGCR ubiquitination and degradation. RNF145, a sterol-responsive ER-resident E3 ligase, is unstable but accumulates following sterol depletion. Sterol addition triggers RNF145 recruitment to HMGCR via Insigs, promoting HMGCR ubiquitination and proteasome-mediated degradation. In the absence of both RNF145 and gp78, Hrd1, a third UBE2G2-dependent E3 ligase, partially regulates HMGCR activity. Our findings reveal a critical role for the sterol-responsive RNF145 in HMGCR regulation and elucidate the complexity of sterol-accelerated HMGCR degradation.

Editorial note

This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

The IS2 Element Improves Transcription Efficiency of Integration-Deficient Lentiviral Vector Episomes

Integration-defective lentiviral vectors (IDLVs) have become an important alternative tool for gene therapy applications and basic research. Unfortunately, IDLVs show lower transgene expression as compared to their integrating counterparts. In this study, we aimed to improve the expression levels of IDLVs by inserting the IS2 element, which harbors SARs and HS4 sequences, into their LTRs (SE-IS2-IDLVs). Contrary to our expectations, the presence of the IS2 element did not abrogate epigenetic silencing by histone deacetylases. In addition, the IS2 element reduced episome levels in IDLV-transduced cells. Interestingly, despite these negative effects, SE-IS2-IDLVs outperformed SE-IDLVs in terms of percentage and expression levels of the transgene in several cell lines, including neurons, neuronal progenitor cells, and induced pluripotent stem cells. We estimated that the IS2 element enhances the transcriptional activity of IDLV LTR circles 6- to 7-fold. The final effect the IS2 element in IDLVs will greatly depend on the target cell and the balance between the negative versus the positive effects of the IS2 element in each cell type. The better performance of SE-IS2-IDLVs was not due to improved stability or differences in the proportions of 1-LTR versus 2-LTR circles but probably to a re-positioning of IS2-episomes into transcriptionally active regions.

Development of lipopolyplexes for gene delivery: A comparison of the effects of differing modes of targeting peptide display on the structure and transfection activities of lipopolyplexes

The design, synthesis and formulation of non-viral gene delivery vectors is an area of renewed research interest. Amongst the most efficient non-viral gene delivery systems are lipopolyplexes, in which cationic peptides are co-formulated with plasmid DNA and lipids. One advantage of lipopolyplex vectors is that they have the potential to be targeted to specific cell types by attaching peptide targeting ligands on the surface, thus increasing both the transfection efficiency and selectivity for disease targets such as cancer cells. In this paper, we have investigated two different modes of displaying cell-specific peptide targeting ligands at the surface of lipopolyplexes. Lipopolyplexes formulated with bimodal peptides, with both receptor binding and DNA condensing sequences, were compared with lipopolyplexes with the peptide targeting ligand directly conjugated to one of the lipids. Three EGFR targeting peptide sequences were studied, together with a range of lipid formulations and maleimide lipid structures. The biophysical properties of the lipopolyplexes and their transfection efficiencies in a basal-like breast cancer cell line were investigated using plasmid DNA bearing genes for the expression of firefly luciferase and green fluorescent protein. Fluorescence quenching experiments were also used to probe the macromolecular organisation of the peptide and pDNA components of the lipopolyplexes. We demonstrated that both approaches to lipopolyplex targeting give reasonable transfection efficiencies, and the transfection efficiency of each lipopolyplex formulation is highly dependent on the sequence of the targeting peptide. To achieve maximum therapeutic efficiency, different peptide targeting sequences and lipopolyplex architectures should be investigated for each target cell type.

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.

A Library-Based Screening Strategy for the Identification of DARPins as Ligands for Receptor-Targeted AAV and Lentiviral Vectors

Delivering genes selectively to the therapeutically relevant cell type is among the prime goals of vector development. Here, we present a high-throughput selection and screening process that identifies designed ankyrin repeat proteins (DARPins) optimally suited for receptor-targeted gene delivery using adeno-associated viral (AAV) and lentiviral (LV) vectors. In particular, the process includes expression, purification, and in situ biotinylation of the extracellular domains of target receptors as Fc fusion proteins in mammalian cells and the selection of high-affinity binders by ribosome display from DARPin libraries each covering more than 1012 variants. This way, DARPins specific for the glutamate receptor subunit GluA4, the endothelial surface marker CD105, and the natural killer cell marker NKp46 were generated. The identification of DARPins best suited for gene delivery was achieved by screening small-scale vector productions. Both LV and AAV particles displaying the selected DARPins transduced only cells expressing the corresponding target receptor. The data confirm that a straightforward process for the generation of receptor-targeted viral vectors has been established. Moreover, biochemical analysis of a panel of DARPins revealed that their functional cell-surface expression as fusion proteins is more relevant for efficient gene delivery by LV particles than functional binding affinity.

Validating the RedMIT/GFP-LC3 Mouse Model by Studying Mitophagy in Autosomal Dominant Optic Atrophy Due to the OPA1Q285STOP Mutation

Background: Autosomal dominant optic atrophy (ADOA) is usually caused by mutations in the essential gene, OPA1. This encodes a ubiquitous protein involved in mitochondrial dynamics, hence tissue specificity is not understood. Dysregulated mitophagy (mitochondria recycling) is implicated in ADOA, being increased in OPA1 patient fibroblasts. Furthermore, autophagy may be increased in retinal ganglion cells (RGCs) of the OPA1Q285STOP mouse model. Aims: We developed a mouse model for studying mitochondrial dynamics in order to investigate mitophagy in ADOA. Methods: We crossed the OPA1Q285STOP mouse with our RedMIT/GFP-LC3 mouse, harboring red fluorescent mitochondria and green fluorescent autophagosomes. Colocalization between mitochondria and autophagosomes, the hallmark of mitophagy, was quantified in fluorescently labeled organelles in primary cell cultures, using two high throughput imaging methods Imagestream (Amnis) and IN Cell Analyzer 1000 (GE Healthcare Life Sciences). We studied colocalization between mitochondria and autophagosomes in fixed sections using confocal microscopy. Results: We validated our imaging methods for RedMIT/GFP-LC3 mouse cells, showing that colocalization of red fluorescent mitochondria and green fluorescent autophagosomes is a useful indicator of mitophagy. We showed that colocalization increases when lysosomal processing is impaired. Further, colocalization of mitochondrial fragments and autophagosomes is increased in cultures from the OPA1Q285STOP/RedMIT/GFP-LC3 mice compared to RedMIT/GFP-LC3 control mouse cells that were wild type for OPA1. This was apparent in both mouse embryonic fibroblasts (MEFs) using IN Cell 1000 and in splenocytes using ImageStream imaging flow cytometer (Amnis). We confirmed that this represents increased mitophagic flux using lysosomal inhibitors. We also used microscopy to investigate the level of mitophagy in the retina from the OPA1Q285STOP/RedMIT/GFP-LC3 mice and the RedMIT/GFP-LC3 control mice. However, the expression levels of fluorescent proteins and the image signal-to-background ratios precluded the detection of colocalization so we were unable to show any difference in colocalization between these mice. Conclusions: We show that colocalization of fluorescent mitochondria and autophagosomes in cell cultures, but not fixed tissues from the RedMIT/GFP-LC3, can be used to detect mitophagy. We used this model to confirm that mitophagy is increased in a mouse model of ADOA. It will be useful for cell based studies of diseases caused by impaired mitochondrial dynamics.

Itaconic acid mediates crosstalk between macrophage metabolism and peritoneal tumors

Control of cellular metabolism is critical for efficient cell function, although little is known about the interplay between cell subset–specific metabolites in situ, especially in the tumor setting. Here, we determined how a macrophage-specific (Mϕ-specific) metabolite, itaconic acid, can regulate tumor progression in the peritoneum. We show that peritoneal tumors (B16 melanoma or ID8 ovarian carcinoma) elicited a fatty acid oxidation–mediated increase in oxidative phosphorylation (OXPHOS) and glycolysis in peritoneal tissue–resident macrophages (pResMϕ). Unbiased metabolomics identified itaconic acid, the product of immune-responsive gene 1–mediated (Irg1-mediated) catabolism of mitochondrial cis-aconitate, among the most highly upregulated metabolites in pResMϕ of tumor-bearing mice. Administration of lentivirally encoded Irg1 shRNA significantly reduced peritoneal tumors. This resulted in reductions in OXPHOS and OXPHOS-driven production of ROS in pResMϕ and ROS-mediated MAPK activation in tumor cells. Our findings demonstrate that tumors profoundly alter pResMϕ metabolism, leading to the production of itaconic acid, which potentiates tumor growth. Monocytes isolated from ovarian carcinoma patients’ ascites fluid expressed significantly elevated levels of IRG1. Therefore, IRG1 in pResMϕ represents a potential therapeutic target for peritoneal tumors.

Analysis of the effect of promoter type and skin pretreatment on antigen expression and antibody response after gene gun-based immunization

Monoclonal antibodies (mAbs) have enabled numerous basic research discoveries and therapeutic approaches for many protein classes. However, there still exist a number of target classes, such as multi-pass membrane proteins, for which antibody discovery is difficult, due in part to lack of high quality, recombinant protein. Here we describe the impact of several parameters on antigen expression and the development of mAbs against human claudin 4 (CLDN4), a potential multi-indication cancer target. Using gene gun-based DNA delivery and bioluminescence imaging, we optimize promoter type by comparing expression profiles of four robust in vivo promoters. In addition, we observe that most vectors rapidly lose expression, ultimately reaching almost background levels by three days post-delivery. Recognizing this limitation, we next explored skin pretreatment strategies as an orthogonal method to further boost the efficiency of mAb generation. We show that SDS pretreatment can boost antigen expression, but fails to significantly increase mAb discovery efficiency. In contrast, we find that sandpaper pretreatment yields 5-fold more FACS⁺ anti-CLDN4 hybridomas, without impacting antigen expression. Our findings coupled with other strategies to improve DNA immunizations should improve the success of mAb discovery against other challenging targets and enable the generation of critical research tools and therapeutic candidates.

Long Terminal Repeat CRISPR-CAR-Coupled "Universal" T Cells Mediate Potent Anti-leukemic Effects

Gene editing can be used to overcome allo-recognition, which otherwise limits allogeneic T cell therapies. Initial proof-of-concept applications have included generation of such "universal" T cells expressing chimeric antigen receptors (CARs) against CD19 target antigens combined with transient expression of DNA-targeting nucleases to disrupt the T cell receptor alpha constant chain (TRAC). Although relatively efficient, transgene expression and editing effects were unlinked, yields variable, and resulting T cell populations heterogeneous, complicating dosing strategies. We describe a self-inactivating lentiviral "terminal" vector platform coupling CAR expression with CRISPR/Cas9 effects through incorporation of an sgRNA element into the ΔU3 3' long terminal repeat (LTR). Following reverse transcription and duplication of the hybrid ΔU3-sgRNA, delivery of Cas9 mRNA resulted in targeted TRAC locus cleavage and allowed the enrichment of highly homogeneous (>96%) CAR+ (>99%) TCR- populations by automated magnetic separation. Molecular analyses, including NGS, WGS, and Digenome-seq, verified on-target specificity with no evidence of predicted off-target events. Robust anti-leukemic effects were demonstrated in humanized immunodeficient mice and were sustained longer than by conventional CAR+TCR+ T cells. Terminal-TRAC (TT) CAR T cells offer the possibility of a pre-manufactured, non-HLA-matched CAR cell therapy and will be evaluated in phase 1 trials against B cell malignancies shortly.

Cytokine-induced interleukin-1 receptor antagonist protein expression in genetically engineered equine mesenchymal stem cells for osteoarthritis treatment

BACKGROUND

A combination of tissue engineering methods employing mesenchymal stem cells (MSCs) together with gene transfer takes advantage of innovative strategies and highlights a new approach for targeting osteoarthritis (OA) and other cartilage defects. Furthermore, the development of systems allowing tunable transgene expression as regulated by natural disease-induced substances is highly desirable.

METHODS

Bone marrow-derived equine MSCs were transduced with a lentiviral vector expressing interleukin-1 receptor antagonist (IL-1Ra) gene under the control of an inducible nuclear factor-kappa B-responsive promoter and IL-1Ra production upon pro-inflammatory cytokine stimulation [tumor necrosis factor (TNF)α, interleukin (IL)-1β] was analysed. To assess the biological activity of the IL-1Ra protein that was produced and the therapeutic effect of IL-1Ra-expressing MSCs (MSC/IL-1Ra), cytokine-based two- and three-dimensional in vitro models of osteoarthritis using equine chondrocytes were established and quantitative real-time polymerase chain reaction (PCR) analysis was used to measure the gene expression of aggrecan, collagen IIA1, interleukin-1β, interleukin-6, interleukin-8, matrix metalloproteinase-1 and matrix metalloproteinase-13.

RESULTS

A dose-dependent increase in IL-1Ra expression was found in MSC/IL-1Ra cells upon TNFα administration, whereas stimulation using IL-1β did not lead to IL-1Ra production above the basal level observed in nonstimulated cells as a result of the existing feedback loop. Repeated cycles of induction allowed on/off modulation of transgene expression. In vitro analyses revealed that IL-1Ra protein present in the conditioned medium from MSC/IL-1Ra cells blocks OA onset in cytokine-treated equine chondrocytes and co-cultivation of MSC/IL-1Ra cells with osteoarthritic spheroids alleviates the severity of the osteoarthritic changes.

CONCLUSIONS

Thus, pro-inflammatory cytokine induced IL-1Ra protein expression from genetically modified MSCs might represent a promising strategy for osteoarthritis treatment.

Leukaemic alterations of IKZF1 prime stemness and malignancy programs in human lymphocytes

Somatic cells acquire stem cell-like properties during cancerous transformation; however, mechanisms through which committed cells develop stemness and malignancy remain largely unknown. Here we uncovered upregulated stem cell program in leukaemic lymphoblasts of patients with IKZF1 alterations by analysing the archived gene-expression profiling datasets. We then used a frequent IKZF1 deletion, IK6, as a model via transduction into human primitive haematopoietic cells, followed by xenotransplantation in mice. Immunophenotypically defined stem, pro-B, and immature/mature (IM/M)-B cells were collected from primary recipients for functional assay and transcriptome profiling. Successful reconstitution in secondary recipient mice revealed the stemness of IK6⁺ pro-B and IM/M-B cells. Upregulated stemness and malignancy programs in IK6⁺ cells confirmed IK6 effects. Interestingly, these programs corresponded to distinct canonical pathways. Remarkably, the pathway profile mapped in the modelled cells well mirrored that in patients’ leukaemic cells; therefore, our study provides a seminal insight into the cancerous reprogramming of somatic cells.

MARCH6 and TRC8 facilitate the quality control of cytosolic and tail-anchored proteins

Misfolded or damaged proteins are typically targeted for destruction by proteasome-mediated degradation, but the mammalian ubiquitin machinery involved is incompletely understood. Here, using forward genetic screens in human cells, we find that the proteasome-mediated degradation of the soluble misfolded reporter, mCherry-CL1, involves two ER-resident E3 ligases, MARCH6 and TRC8. mCherry-CL1 degradation is routed via the ER membrane and dependent on the hydrophobicity of the substrate, with complete stabilisation only observed in double knockout MARCH6/TRC8 cells. To identify a more physiological correlate, we used quantitative mass spectrometry and found that TRC8 and MARCH6 depletion altered the turnover of the tail-anchored protein heme oxygenase-1 (HO-1). These E3 ligases associate with the intramembrane cleaving signal peptide peptidase (SPP) and facilitate the degradation of HO-1 following intramembrane proteolysis. Our results highlight how ER-resident ligases may target the same substrates, but work independently of each other, to optimise the protein quality control of selected soluble and tail-anchored proteins.

The transcription factor MEF2A plays a key role in the differentiation/maturation of rat neural stem cells into neurons

Neural stem cells (NSCs) are self-renewing multipotent stem cells that can be proliferated in vitro and differentiated into neuronal and/or glial lineages, making them an ideal model to study the processes involved in neuronal differentiation. Here we have used NSCs to investigate the role of the transcription factor MEF2A in neuronal differentiation and development in vitro. We show that although MEF2A is present in undifferentiated NSCs, following differentiation it is expressed at significantly higher levels in a subset of neuronal compared to non-neuronal cells. Furthermore, shRNA-mediated knockdown of MEF2A reduces the number of NSC-derived neurons compared to non-neuronal cells after differentiation. Together, these data indicate that MEF2A participates in neuronal differentiation/maturation from NSCs.

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Undifferentiated and differentiated neural stem cells (NSCs) express MEF2A in vitro.

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NSC-derived neurons express more MEF2A than NSC-derived glia.

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Ablating MEF2A reduces NSC differentiation into neurons.

NKG2H-Expressing T Cells Negatively Regulate Immune Responses

The biology and function of NKG2H receptor, unlike the better characterized members of the NKG2 family NKG2A, NKG2C, and NKG2D, remains largely unclear. Here, we show that NKG2H is able to associate with the signaling adapter molecules DAP12 and DAP10 suggesting that this receptor can signal for cell activation. Using a recently described NKG2H-specific monoclonal antibody (mAb), we have characterized the expression and function of lymphocytes that express this receptor. NKG2H is expressed at the cell surface of a small percentage of peripheral blood mononuclear cell (PBMC) and is found more frequently on T cells, rather than NK cells. Moreover, although NKG2H is likely to trigger activation, co-cross-linking of this receptor with an NKG2H-specific mAb led to decreased T cell activation and proliferation in polyclonal PBMC cultures stimulated by anti-CD3 mAbs. This negative regulatory activity was seen only after cross-linking with NKG2H, but not NKG2A- or NKG2C-specific monoclonal antibodies. The mechanism underlying this negative effect is as yet unclear, but did not depend on the release of soluble factors or recognition of MHC class I molecules. These observations raise the intriguing possibility that NKG2H may be a novel marker for T cells able to negatively regulate T cell responses.

Human adipose tissue-derived stromal cells in combination with exogenous stimuli facilitate three-dimensional network formation of human endothelial cells derived from various sources

In natural tissues, the nutrition of cells and removal of waste products is facilitated by a dense capillary network which is generated during development. This perfusion system is also indispensable for tissue formation in vitro. Nutrition depending solely on diffusion is not sufficient to generate tissues of clinically relevant dimensions, which is a core aim in tissue engineering research. In this study, the establishment of a vascular network was investigated in a self-assembling approach employing endothelial and mural cells. The process of vascularization was analyzed in constructs based on a carrier matrix of decellularized porcine small intestinal submucosa (SIS). A three-dimensional hydrogel containing Matrigel™, collagen, and respective cells was casted on top of the SIS. Various types of human endothelial cells (hECs), e.g. HUVECs, cardiac tissue ECs (hCECs), pulmonary artery ECs (hPAECs), and iPSC-derived ECs, were co-cultured with human adipose tissue-derived stromal cells (hASCs) within the hydrogel. Analyzed hECs were able to self-assemble and form three-dimensional networks harboring small caliber lumens within the hydrogel constructs in the presence of hASCs as supporting cells. Additionally, microvessel assembling required exogenous growth factor supplementation. This study demonstrates the development of stable vascularized hydrogels applying hASCs as mural cells in combination with various types of hECs, paving the way for the generation of clinically applicable tissue engineered constructs.

Modular cell-based platform for high throughput identification of compounds that inhibit a viral interferon antagonist of choice

Viral interferon (IFN) antagonists are a diverse class of viral proteins that counteract the host IFN response, which is important for controlling viral infections. Viral IFN antagonists are often multifunctional proteins that perform vital roles in virus replication beyond IFN antagonism. The critical importance of viral IFN antagonists is highlighted by the fact that almost all viruses encode one of these proteins. Inhibition of viral IFN antagonists has the potential to exert pleiotropic antiviral effects and thus this important protein class represents a diverse plethora of novel therapeutic targets. To exploit this, we have successfully developed and executed a novel modular cell-based platform that facilitates the safe and rapid screening for inhibitors of a viral IFN antagonist of choice. The platform is based on two reporter cell-lines that provide a simple method to detect activation of IFN induction or signaling via an eGFP gene placed under the control of the IFNβ or an ISRE-containing promoter, respectively. Expression of a target IFN antagonist in the appropriate reporter cell-line will block the IFN response and hence eGFP expression. We hypothesized that addition of a compound that inhibits IFN antagonist function will release the block imposed on the IFN response and hence restore eGFP expression, providing a measurable parameter for high throughput screening (HTS). We demonstrate assay proof-of-concept by (i) exploiting hepatitis C virus (HCV) protease inhibitors to inhibit NS3-4A's capacity to block IFN induction and (ii) successfully executing two HTS targeting viral IFN antagonists that block IFN signaling; NS2 and IE1 from human respiratory syncytial virus (RSV) and cytomegalovirus (CMV) respectively, two clinically important viruses for which vaccine development has thus far been unsuccessful and new antivirals are required. Both screens performed robustly and Z' Factor scores of >0.6 were achieved. We identified (i) four hit compounds that specifically inhibit RSV NS2's ability to block IFN signaling by mediating STAT2 degradation and exhibit modest antiviral activity and (ii) two hit compounds that interfere with IE1 transcription and significantly impair CMV replication. Overall, we demonstrate assay proof-of-concept as we target viral IFN antagonists from unrelated viruses and demonstrate its suitability for HTS.

The HIV-derived protein Vpr52-96 has anti-glioma activity in vitro and in vivo

Patients with actively replicating human immunodeficiency virus (HIV) exhibit adverse reactions even to low irradiation doses. High levels of the virus-encoded viral protein R (Vpr) are believed to be one of the major underlying causes for increased radiosensitivity. As Vpr efficiently crosses the blood-brain barrier and accumulates in astrocytes, we examined its efficacy as a drug for treatment of glioblastoma multiforme (GBM).

In vitro, four glioblastoma-derived cell lines with and without methylguanine-DNA methyltransferase (MGMT) overexpression (U251, U87, U251-MGMT, U87-MGMT) were exposed to Vpr, temozolomide (TMZ), conventional photon irradiation (2 to 6 Gy) or to combinations thereof. Vpr showed high rates of acute toxicities with median effective doses of 4.0±1.1 μM and 15.7±7.5 μM for U251 and U87 cells, respectively. Caspase assays revealed Vpr-induced apoptosis in U251, but not in U87 cells. Vpr also efficiently inhibited clonogenic survival in both U251 and U87 cells and acted additively with irradiation. In contrast to TMZ, Vpr acted independently of MGMT expression.

Dose escalation in mice (n=12) was feasible and resulted in no evident renal or liver toxicity. Both, irradiation with 3×5 Gy (n=8) and treatment with Vpr (n=5) delayed intracerebral tumor growth and prolonged overall survival compared to untreated animals (n=5; p_{3×5 Gy}<0.001 and p_Vpr=0.04; log-rank test).

Our data show that the HIV-encoded peptide Vpr exhibits all properties of an effective chemotherapeutic drug and may be a useful agent in the treatment of GBM.

Characterization of Influenza Virus Pseudotyped with Ebolavirus Glycoprotein

We have produced a new Ebola virus pseudotype, E-S-FLU, that can be handled in biosafety level 1/2 containment for laboratory analysis. The E-S-FLU virus is a single-cycle influenza virus coated with Ebolavirus glycoprotein, and it encodes enhanced green fluorescence protein as a reporter that replaces the influenza virus hemagglutinin. MDCK-SIAT1 cells were transduced to express Ebolavirus glycoprotein as a stable transmembrane protein for E-S-FLU virus production. Infection of cells with the E-S-FLU virus was dependent on the Niemann-Pick C1 protein, which is the well-characterized receptor for Ebola virus entry at the late endosome/lysosome membrane. The E-S-FLU virus was neutralized specifically by an anti-Ebolavirus glycoprotein antibody and a variety of small drug molecules that are known to inhibit the entry of wild-type Ebola virus. To demonstrate the application of this new Ebola virus pseudotype, we show that a single laboratory batch was sufficient to screen a library (LOPAC¹²⁸⁰; Sigma) of 1,280 pharmacologically active compounds for inhibition of virus entry. A total of 215 compounds inhibited E-S-FLU virus infection, while only 22 inhibited the control H5-S-FLU virus coated in H5 hemagglutinin. These inhibitory compounds have very dispersed targets and mechanisms of action, e.g., calcium channel blockers, estrogen receptor antagonists, antihistamines, serotonin uptake inhibitors, etc., and this correlates with inhibitor screening results obtained with other pseudotypes or wild-type Ebola virus in the literature. The E-S-FLU virus is a new tool for Ebola virus cell entry studies and is easily applied to high-throughput screening assays for small-molecule inhibitors or antibodies.

IMPORTANCE Ebola virus is in the Filoviridae family and is a biosafety level 4 pathogen. There are no FDA-approved therapeutics for Ebola virus. These characteristics warrant the development of surrogates for Ebola virus that can be handled in more convenient laboratory containment to study the biology of the virus and screen for inhibitors. Here we characterized a new surrogate, named E-S-FLU virus, that is based on a disabled influenza virus core coated with the Ebola virus surface protein but does not contain any genetic information from the Ebola virus itself. We show that E-S-FLU virus uses the same cell entry pathway as wild-type Ebola virus. As an example of the ease of use of E-S-FLU virus in biosafety level 1/2 containment, we showed that a single production batch could provide enough surrogate virus to screen a standard small-molecule library of 1,280 candidates for inhibitors of viral entry.

Inflammation-induced transgene expression in genetically engineered equine mesenchymal stem cells

BACKGROUND

Osteoarthritis, a chronic and progressive degenerative joint disorder, ranks amongst the top five causes of disability. Given the high incidence, associated socioeconomic costs and the absence of effective disease-modifying therapies of osteoarthritis, cell-based treatments offer a promising new approach. Owing to their paracrine, differentiation and self-renewal abilities, mesenchymal stem cells (MSCs) have great potential for regenerative medicine, which might be further enhanced by targeted gene therapy. Hence, the development of systems allowing transgene expression, particularly when regulated by natural disease-dependent occuring substances, is of high interest.

METHODS

Bone marrow-isolated equine MSCs were stably transduced with an HIV-1 based lentiviral vector expressing the luciferase gene under control of an inducible nuclear factor κB (NFκB)-responsive promoter. Marker gene expression was analysed by determining luciferase activity in transduced cells stimulated with different concentrations of interleukin (IL)-1β or tumour necrosis factor (TNF)α.

RESULTS

A dose-dependent increase in luciferase expression was observed in transduced MSCs upon cytokine stimulation. The induction effect was more potent in cells treated with TNFα compared to those treated with IL-1β. Maximum transgene expression was obtained after 48 h of stimulation and the same time was necessary to return to baseline luciferase expression levels after withdrawal of the stimulus. Repeated cycles of induction allowed on-off modulation of transgene expression without becoming refractory to induction. The NFκB-responsive promoter retained its inducibility also in chondrogenically differentiated MSC/Luc cells.

CONCLUSIONS

The results of the present study demonstrate that on demand transgene expression from the NFκB-responsive promoter using naturally occurring inflammatory cytokines can be induced in undifferentiated and chondrogenically differentiated equine MSCs. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Antigen-specific oncolytic MV-based tumor vaccines through presentation of selected tumor-associated antigens on infected cells or virus-like particles

Recombinant vaccine strain-derived measles virus (MV) is clinically tested both as vaccine platform to protect against other pathogens and as oncolytic virus for tumor treatment. To investigate the potential synergism in anti-tumoral efficacy of oncolytic and vaccine properties, we chose Ovalbumin and an ideal tumor antigen, claudin-6, for pre-clinical proof of concept. To enhance immunogenicity, both antigens were presented by retroviral virus-like particle produced in situ during MV-infection. All recombinant MV revealed normal growths, genetic stability, and proper expression and presentation of both antigens. Potent antigen-specific humoral and cellular immunity were found in immunized MV-susceptible IFNAR^-/--CD46Ge mice. These immune responses significantly inhibited metastasis formation or increased therapeutic efficacy compared to control MV in respective novel in vivo tumor models using syngeneic B16-hCD46/mCLDN6 murine melanoma cells. These data indicate the potential of MV to trigger selected tumor antigen-specific immune responses on top of direct tumor lysis for enhanced efficacy.

In situ regeneration of retinal pigment epithelium by gene transfer of E2F2: a potential strategy for treatment of macular degenerations

The retinal pigment epithelium (RPE) interacts closely with photoreceptors to maintain visual function. In degenerative diseases such as Stargardt disease and age-related macular degeneration, the leading cause of blindness in the developed world, RPE cell loss is followed by photoreceptor cell death. RPE cells can proliferate under certain conditions, suggesting an intrinsic regenerative potential, but so far this has not been utilised therapeutically. Here, we used E2F2 to induce RPE cell replication and thereby regeneration. In both young and old (2 and 18 month) wildtype mice, subretinal injection of non-integrating lentiviral vector expressing E2F2 resulted in 47% of examined RPE cells becoming BrdU positive. E2F2 induced an increase in RPE cell density of 17% compared with control vector-treated and 14% compared with untreated eyes. We also tested this approach in an inducible transgenic mouse model of RPE loss, generated through activation of diphtheria toxin-A gene. E2F2 expression resulted in a 10-fold increase in BrdU uptake and a 34% increase in central RPE cell density. Although in mice this localised rescue is insufficiently large to be demonstrable by electroretinography, a measure of massed retinal function, these results provide proof-of-concept for a strategy to induce in situ regeneration of RPE for the treatment of RPE degeneration.

Targeting acute myeloid leukemia by drug-induced c-MYB degradation

Despite advances in our understanding of the molecular basis for particular subtypes of acute myeloid leukemia (AML), effective therapy remains a challenge for many individuals suffering from this disease. A significant proportion of both pediatric and adult AML patients cannot be cured and since the upper limits of chemotherapy intensification have been reached, there is an urgent need for novel therapeutic approaches. The transcription factor c-MYB has been shown to play a central role in the development and progression of AML driven by several different oncogenes, including mixed lineage leukemia (MLL)-fusion genes. Here, we have used a c-MYB gene expression signature from MLL-rearranged AML to probe the Connectivity Map database and identified mebendazole as a c-MYB targeting drug. Mebendazole induces c-MYB degradation via the proteasome by interfering with the heat shock protein 70 (HSP70) chaperone system. Transient exposure to mebendazole is sufficient to inhibit colony formation by AML cells, but not normal cord blood-derived cells. Furthermore, mebendazole is effective at impairing AML progression in vivo in mouse xenotransplantation experiments. In the context of widespread human use of mebendazole, our data indicate that mebendazole-induced c-MYB degradation represents a safe and novel therapeutic approach for AML.

Actin-based protrusions of migrating neutrophils are intrinsically lamellar and facilitate direction changes

Leukocytes and other amoeboid cells change shape as they move, forming highly dynamic, actin-filled pseudopods. Although we understand much about the architecture and dynamics of thin lamellipodia made by slow-moving cells on flat surfaces, conventional light microscopy lacks the spatial and temporal resolution required to track complex pseudopods of cells moving in three dimensions. We therefore employed lattice light sheet microscopy to perform three-dimensional, time-lapse imaging of neutrophil-like HL-60 cells crawling through collagen matrices. To analyze three-dimensional pseudopods we: (i) developed fluorescent probe combinations that distinguish cortical actin from dynamic, pseudopod-forming actin networks, and (ii) adapted molecular visualization tools from structural biology to render and analyze complex cell surfaces. Surprisingly, three-dimensional pseudopods turn out to be composed of thin (<0.75 µm), flat sheets that sometimes interleave to form rosettes. Their laminar nature is not templated by an external surface, but likely reflects a linear arrangement of regulatory molecules. Although we find that Arp2/3-dependent pseudopods are dispensable for three-dimensional locomotion, their elimination dramatically decreases the frequency of cell turning, and pseudopod dynamics increase when cells change direction, highlighting the important role pseudopods play in pathfinding.

Peptides derived from evolutionarily conserved domains in Beclin-1 and Beclin-2 enhance the entry of lentiviral vectors into human cells

Autophagy-related proteins such as Beclin-1 are involved in an array of complex processes, including antiviral responses, and may also modulate the efficiency of gene therapy viral vectors. The Tat-Beclin-1 (TB1) peptide has been reported as an autophagy-inducing factor inhibiting the replication of pathogens such as HIV, type 1 (HIV-1). However, autophagy-related proteins are also essential for the early steps of HIV-1 infection. Therefore, we examined the effects of the Beclin-1 evolutionarily conserved domain in TB1 on viral transduction and autophagy in single-round HIV infection or with nonreplicative HIV-1-derived lentiviral vectors. TB1 enhanced transduction with various pseudotypes but without inducing the autophagy process. TB1 augmented the transduction of human CD34+ hematopoietic stem/progenitor cells while maintaining their capacity to engraft in vivo into humanized mice. TB1 was as effective as other transduction additives and functioned by enhancing the adhesion and fusion of viral particles with target cells but not their aggregation. We also found that the N-terminal L1 loop was critical for TB1 transduction-enhancing activity. Interestingly, the Tat-Beclin-2 (TB2) peptide, derived from the human Beclin-2 protein, was even more potent than TB1 in promoting viral transduction and infection. Taken together, our findings suggest that the TB1 and TB2 peptides enhance the viral entry step. Tat-Beclin peptides therefore represent a new family of viral transduction enhancers for potential use in gene therapy.

Transplanted fibroblasts proliferate in host bronchial tissue and enhance bronchial anastomotic healing in a rodent model

INTRODUCTION

Healing of airway anastomoses after preoperative irradiation can be a significant clinical problem. The augmentation of bronchial anastomoses with a fibroblast-seeded human acellular dermis (hAD) was shown to be beneficial, although the underlying mechanism remained unclear. Therefore, in this study we investigated the fate of the fibroblasts transplanted to the scaffold covering the anastomosis.

MATERIAL AND METHODS

32 Fisher rats underwent surgical anastomosis of the left main bronchus. In a 2 × 2 factorial design, they were randomized to receive preoperative irradiation of 20 Gy and augmentation of the anastomosis with a fibroblast-seeded transplant. Fibroblasts from subcutaneous fat of Fischer-344 rat were transduced retrovirally with tdTomato for cell tracking. After 7 and 14 days, animals were sacrificed and cell concentration of transplanted and nontransplanted fibroblasts in the hAD as well as in the bronchial tissue was measured using RT-PCR.

RESULTS

Migration of transplanted fibroblasts from dermis to bronchus were demonstrated in both groups, irradiated and nonirradiated. In the irradiated groups, there was a cell count of 7 × 104 ± 1 × 104 tomato+-fibroblasts in the bronchial tissue at day 7, rising to 1 × 105 ± 1 × 104 on day 14 (p <0.0001). Tomato+-cell concentration in hAD increased from 6 × 103 ± 1 × 103 at day 7 to 6 × 104 ± 1 × 104 at day 14 (p <0.0001). In the nonirradiated groups, tomato+-cell concentration in bronchus was 4 × 103 ± 1 × 103 on day 7 and 4 × 103 ± 1 × 103 at day 14. In the hAD tomato+ cell concentration rising from 1 × 104 ± 1 × 103 at day 7 to 2 × 104 ± 3 × 103 cells at day 14 (p = 0.0028).

CONCLUSIONS

Transplanted fibroblasts in the irradiated groups proliferate and migrate into the irradiated host bronchial tissue, but not in the nonirradiated groups.

Analysis of the recovery of CD247 expression in a PID patient: insights into the spontaneous repair of defective genes

The propensity of genes to mutate influences the probability of spontaneous reversion of genetic defects in PID.

Interaction between von Hippel-Lindau Protein and Fatty Acid Synthase Modulates Hypoxia Target Gene Expression

Hypoxia-inducible factors (HIFs) play a central role in the transcriptional response to changes in oxygen availability. Stability of HIFs is regulated by multi-step reactions including recognition by the von Hippel-Lindau tumour suppressor protein (pVHL) in association with an E3 ligase complex. Here we show that pVHL physically interacts with fatty acid synthase (FASN), displacing the E3 ubiquitin ligase complex. This results in HIF-α protein stabilization and activation of HIF target genes even in normoxia such as during adipocyte differentiation. 25-hydroxycholesterol (25-OH), an inhibitor of FASN expression, also inhibited HIF target gene expression in cultured cells and in mouse liver. Clinically, FASN is frequently upregulated in a broad variety of cancers and has been reported to have an oncogenic function. We found that upregulation of FASN correlated with induction of many HIF target genes, notably in a malignant subtype of prostate tumours. Therefore, pVHL-FASN interaction plays a regulatory role for HIFs and their target gene expression.

Generation and characterization of ErbB2-CAR-engineered cytokine-induced killer cells for the treatment of high-risk soft tissue sarcoma in children

Pediatric patients with recurrent, refractory or advanced soft tissue sarcoma (STS) who are simultaneously showing signs of cumulative treatment toxicity are in need of novel therapies. In this preclinical analysis, we identified ErbB2 as a targetable antigen on STS cells and used cytokine-induced killer (CIK) cells transduced with the lentiviral 2^nd-generation chimeric antigen receptor (CAR) vector pS-5.28.z-IEW to target ErbB2-positive tumors. Solely CIK cell subsets with the CD3⁺ T cell phenotype showed up to 85% cell surface expression of the respective CAR. A comparison of wildtype (WT), mock-vector and ErbB2-CAR-CIK cells showed, that engineered cells exhibited diminished in vitro expansion, retained WT CIK cell phenotype with higher percentages of differentiated effector memory/effector cells. Activating natural killer (NK) cell receptor NKG2D-restricted target cell recognition and killing of WT and ErbB2-CAR-CIK cells was maintained against ErbB2-negative tumors, while ErbB2-CAR-CIK cells demonstrated significantly increased cytotoxicity against ErbB2-positive targets, including primary tumors. ErbB2-CAR- but not WT CIK cells proliferated, infiltrated and efficiently lysed tumor cell monolayers as well as 3D tumor spheroids.

Here, we demonstrate a potential cell therapeutic approach using ErbB2-CAR-CIK cells for the recognition and elimination of tumor cells expressing ErbB2, which we identified as a targetable antigen on high-risk STS cells.

The power of bioluminescence imaging in understanding host-pathogen interactions

Infectious diseases are one of the leading causes of death worldwide. Modelling and understanding human infection is imperative to developing treatments to reduce the global burden of infectious disease. Bioluminescence imaging is a highly sensitive, non-invasive technique based on the detection of light, produced by luciferase-catalysed reactions. In the study of infectious disease, bioluminescence imaging is a well-established technique; it can be used to detect, localize and quantify specific immune cells, pathogens or immunological processes. This enables longitudinal studies in which the spectrum of the disease process and its response to therapies can be monitored. Light producing transgenic rodents are emerging as key tools in the study of host response to infection. Here, we review the strategies for identifying biological processes in vivo, including the technology of bioluminescence imaging and illustrate how this technique is shedding light on the host-pathogen relationship.

Molecular Effects of Stromal-Selective Targeting by uPAR-Retargeted Oncolytic Virus in Breast Cancer

The tumor microenvironment (TME) is a relevant target for novel biological therapies. MV-m-uPA and MV-h-uPA are fully retargeted, species-specific, oncolytic measles viruses (MV) directed against murine or human urokinase receptor (PLAUR/uPAR), expressed in tumor and stromal cells. The effects of stromal-selective targeting by uPAR-retargeted MVs were investigated. In vitro infection, virus-induced GFP expression, and cytotoxicity by MV-h-uPA and MV-m-uPA were demonstrated in human and murine cancer cells and cancer-associated fibroblasts in a species-specific manner. In a murine fibroblast/human breast cancer 3D coculture model, selective fibroblast targeting by MV-m-uPA inhibited breast cancer cell growth. Systemic administration of murine-specific MV-m-uPA in mice bearing human MDA-MB-231 xenografts was associated with a significant delay in tumor progression and improved survival compared with controls. Experiments comparing tumor (MV-h-uPA) versus stromal (MV-m-uPA) versus combined virus targeting showed that tumor and stromal targeting was associated with improved tumor control over the other groups. Correlative studies confirmed in vivo viral targeting of tumor stroma by MV-m-uPA, increased apoptosis, and virus-induced differential regulation of murine stromal genes associated with inflammatory, angiogenesis, and survival pathways, as well as indirect regulation of human cancer pathways, indicating viral-induced modulation of tumor-stroma interactions. These data demonstrate the feasibility of stromal-selective targeting by an oncolytic MV, virus-induced modulation of tumor-stroma pathways, and subsequent tumor growth delay. These findings further validate the critical role of stromal uPAR in cancer progression and the potential of oncolytic viruses as antistromal agents.Implications: The current report demonstrates for the first time the biological, in vitro, and in vivo antitumor and molecular effects of stromal selective targeting by an oncolytic virus. Mol Cancer Res; 15(10); 1410-20. ©2017 AACR.

WASP and SCAR are evolutionarily conserved in actin-filled pseudopod-based motility

Eukaryotic cells use diverse cellular mechanisms to crawl through complex environments. Fritz-Laylin et al. define α-motility as a mode of migration associated with dynamic, actin-filled pseudopods and show that WASP and SCAR constitute an evolutionarily conserved genetic signature of α-motility.

Diverse eukaryotic cells crawl through complex environments using distinct modes of migration. To understand the underlying mechanisms and their evolutionary relationships, we must define each mode and identify its phenotypic and molecular markers. In this study, we focus on a widely dispersed migration mode characterized by dynamic actin-filled pseudopods that we call “α-motility.” Mining genomic data reveals a clear trend: only organisms with both WASP and SCAR/WAVE—activators of branched actin assembly—make actin-filled pseudopods. Although SCAR has been shown to drive pseudopod formation, WASP’s role in this process is controversial. We hypothesize that these genes collectively represent a genetic signature of α-motility because both are used for pseudopod formation. WASP depletion from human neutrophils confirms that both proteins are involved in explosive actin polymerization, pseudopod formation, and cell migration. WASP and WAVE also colocalize to dynamic signaling structures. Moreover, retention of WASP together with SCAR correctly predicts α-motility in disease-causing chytrid fungi, which we show crawl at >30 µm/min with actin-filled pseudopods. By focusing on one migration mode in many eukaryotes, we identify a genetic marker of pseudopod formation, the morphological feature of α-motility, providing evidence for a widely distributed mode of cell crawling with a single evolutionary origin.

Tropism, intracerebral distribution, and transduction efficiency of HIV- and SIV-based lentiviral vectors after injection into the mouse brain: a qualitative and quantitative in vivo study

Lentiviruses are suitable to transfer potential therapeutic genes into non-replicating cells such as neurons, but systematic in vivo studies on transduction of neural cells within the complete brain are missing. We analysed the distribution of transduced cells with respect to brain structure, virus tropism, numbers of transduced neurons per brain, and influence of the Vpx or Vpr accessory proteins after injection of vectors based on SIVsmmPBj, HIV-2, and HIV-1 lentiviruses into the right striatum of the mouse brain. Transduced cells were found ipsilaterally around the injection canal, in corpus striatum and along corpus callosum, irrespective of the vector type. All vectors except HIV-2SEW transduced also single cells in the olfactory bulb, hippocampus, and cerebellum. Vector HIV-2SEW was the most neuron specific. However, vectors PBjSEW and HIV-1SEW transduced more neurons per brain (means 41,299 and 32,309) than HIV-2SEW (16,102). In the presence of Vpx/Vpr proteins, HIV-2SEW(Vpx) and HIV-1SEW(Vpr) showed higher overall transduction efficiencies (30,696 and 27,947 neurons per brain) than PBjSEW(Vpx) (6636). The distances of transduced cells from the injection canal did not differ among the viruses but correlated positively with the numbers of transduced neurons. The presence of Vpx/Vpr did not increase the numbers of transduced neurons. Parental virus type and the vector equipment seem to influence cellular tropism and transduction efficiency. Thus, precision of injection and choice of virus pseudotype are not sufficient when targeted lentiviral vector transduction of a defined brain cell population is required.

Expression and characterization of a codon-optimized blood coagulation factor VIII

Essentials Recombinant factor VIII (FVIII) is known to be expressed at a low level in cell culture. To increase expression, we used codon-optimization of a B-domain deleted FVIII (BDD-FVIII). This resulted in 7-fold increase of the expression level in cell culture. The biochemical properties of codon-optimized BDD-FVIII were similar to the wild-type protein.

SUMMARY

Background Production of recombinant factor VIII (FVIII) is challenging because of its low expression. It was previously shown that codon-optimization of a B-domain-deleted FVIII (BDD-FVIII) cDNA resulted in increased protein expression. However, it is well recognized that synonymous mutations may affect the protein structure and function. Objectives To compare biochemical properties of a BDD-FVIII variants expressed from codon-optimized and wild-type cDNAs (CO and WT, respectively). Methods Each variant of the BDD-FVIII was expressed in several independent Chinese hamster ovary (CHO) cell lines, generated using a lentiviral platform. The proteins were purified by two-step affinity chromatography and analyzed in parallel by PAGE-western blot, mass spectrometry, circular dichroism, surface plasmon resonance, and chromogenic, clotting and thrombin generation assays. Results and conclusion The average yield of the CO was 7-fold higher than WT, whereas both proteins were identical in the amino acid sequences (99% coverage) and very similar in patterns of the molecular fragments (before and after thrombin cleavage), glycosylation and tyrosine sulfation, secondary structures and binding to von Willebrand factor and to a fragment of the low-density lipoprotein receptor-related protein 1. The CO preparations had on average 1.5-fold higher FVIII specific activity (activity normalized to protein mass) than WT preparations, which was attributed to better preservation of the CO structure as a result of considerably higher protein concentrations during the production. We concluded that the codon-optimization of the BDD-FVIII resulted in significant increase of its expression and did not affect the structure-function properties.