EF1α Promoter Research Articles

Lentiviral Gene Therapy of Chronic Granulomatous Disease (CGD) - Functional Assessment of Universal and Tissue-specific Promoters.

Chronic granulomatous disease (CGD) is a rare congenital immunodeficiency characterized by a defect in nicotinamide adenine dinucleotide phosphate (NADPH) oxidase required for phagocytosis. Hematopoietic stem cell (HSC) transplantation is currently the only curative treatment but it is ladened with morbidities and mortality. Gene therapy is a promising treatment for CGD. However, if not properly designed, the gene therapy approach may not be successful. We engineered lentiviral vectors (LVs) carrying a universal promoter (EF1a) and two myeloid-specific promoters (miR223 and CD68) to drive the expression of green fluorescent protein (GFP) or CYBB, one of the key defective genes causing CGD. Tissue-specific LV expression was investigated in vitro and in a CGD mouse model. We compared GFP expression in both myeloid differentiated and undifferentiated HSCs. The CGD mice were transplanted with LV-modified mouse HSCs to investigate expression of CYBB and restoration of reactive oxygen species (ROS). The LV promoters were further compared under low and high transgenic conditions to assess safety and therapeutic efficacy. A pneumonia disease model based on pathogenic Staphylococcus aureus (S. aureus) challenge was established to assess the survival rate and body weight change. All three promoters demonstrated ectopic CYBB expression in vitro and in vivo. The EF1a promoter showed the highest expression of GFP or CYBB in transduced cells including HSCs without cytotoxicity, whereas the LV-miR223 showed the highest transgene delivery efficiency with high myeloid-specificity. Importantly, under low transgenic condition, only the LV-EF1a-CYBB showed high anti-bacterial activity in vivo.

Differentiation of Human Adipose-Derived Mesenchymal Stromal/Stem Cells into Insulin-Producing Cells with A Single Tet-Off Lentiviral Vector System.

Human adipose-derived mesenchymal stromal/stem cells (hASC) constitute an attractive source of stem cells for cell-based therapies in regenerative medicine and tissue engineering as they are easy to acquire from lipoaspirate, expansion, and genetic modification ex vivo. The combination of Pdx-1, MafA, and NeuroD1 has been indicated to possess the ability to reprogram various types of cells into insulin-producing cells. The aim of this study is to investigate whether MafA and NeuroD1 would cooperate with Pdx-1 in the differentiation of hASC into insulin-producing cells. In this experimental study, we generated polycistronic expression vectors expressing Pdx1 and MafA/NeuroD1 with a reporter from a human EF-1α promoter using 2A peptides in a single tet-off lentiviral vector system. Briefly, hASC were transduced with the lentiviral vectors and allowed to differentiate into insulin-producing cells in vitro and in vivo. Thereafter, RNA expression, dithizone staining, and immunofluorescent analysis were conducted. Cleaved transcriptional factors from a single tet-off lentiviral vector were functionally equivalent to their native proteins and strictly regulated by doxycycline (Dox). Insulin gene expression in hASC transduced with Pdx1, Pdx1/ MafA, and Pdx1/NeuroD1 in differentiation medium were successfully increased by 1.89 ± 0.39, 4.81 ± 0.98, 5.51 ± 0.63, respectively, compared to venus-transduced, control hASC. These cells could form dithizone-positive cell clusters in vitro and were found to express insulin in vivo. Using our single tet-off lentiviral vector system, Pdx-1 and MafA/NeuroD1 could be simultaneously expressed in the absence of Dox. Further, this system allowed the differentiation of hASC into insulin-producing cells.

Validation of Promoters and Codon Optimization on CRISPR/Cas9-Engineered Jurkat Cells Stably Expressing αRep4E3 for Interfering with HIV-1 Replication

Persistent and efficient therapeutic protein expression in the specific target cell is a significant concern in gene therapy. The controllable integration site, suitable promoter, and proper codon usage influence the effectiveness of the therapeutic outcome. Previously, we developed a non-immunoglobulin scaffold, alpha repeat protein (αRep4E3), as an HIV-1 RNA packaging interference system in SupT1 cells using the lentiviral gene transfer. Although the success of anti-HIV-1 activity was evidenced, the integration site is uncontrollable and may not be practical for clinical translation. In this study, we use the CRISPR/Cas9 gene editing technology to precisely knock-in αRep4E3 genes into the adeno-associated virus integration site 1 (AAVS1) safe harbor locus of the target cells. We compare the αRep4E3 expression under the regulation of three different promoters, including cytomegalovirus (CMV), human elongation factor-1 alpha (EF1α), and ubiquitin C (UbC) promoters with and without codon optimization in HEK293T cells. The results demonstrated that the EF1α promoter with codon-optimized αRep4E3mCherry showed higher protein expression than other promoters with non-optimized codons. We then performed a proof-of-concept study by knocking in the αRep4E3mCherry gene at the AAVS1 locus of the Jurkat cells. The results showed that the αRep4E3mCherry-expressing Jurkat cells exhibited anti-HIV-1 activities against HIV-1NL4-3 strain as evidenced by decreased capsid (p24) protein levels and viral genome copies as compared to the untransfected Jurkat control cells. Altogether, our study demonstrates that the αRep4E3 could interfere with the viral RNA packaging and suggests that the αRep4E3 scaffold protein could be a promising anti-viral molecule that offers a functional cure for people living with HIV-1.

Improved Lentiviral In Vivo Gene Therapy for Chronic Granulomatous Disease

Background: Chronic granulomatous disease (CGD) is a congenital immunodeficiency characterized by severe life-threatening infections. CGD patients lack reactive oxygen species (ROS) in phagocytic leukocytes and often develop widespread tissue granulomas. The current treatment for CGD is lifelong antibiotic prophylaxis or hematopoietic stem cell transplantation (HSCT). However, most patients cannot find matched donors, and HSCT is known to have increased risk in CGD patients. Gene therapy has become a promising treatment for CGD. At present, "ex vivo" HSC gene therapy is the widely applied strategy. "In vivo" gene therapy is based on direct delivery of gene therapy vectors into patients, which could overcome the difficulties in HSCT. Methods: We have developed an in vivo CGD gene therapy strategy by intravenous (iv) injection of lentiviral vectors (LVs) carrying an universal EF1a promoter or a myeloid-specific miR223 promoter driving the expression of CYBB (cytochrome B-245 beta chain, or p91-phox) in X-CGD mice (X-CGD; B6.129S-Cybbtm1Din/J). Each mouse received 1x109 transduction units (TU) of LV-CYBB via iv injection after non-myeloablative conditioning. A second injection of 1x109 TU of LV-CYBB after re-conditioning was given 12 weeks later. Results: We developed a chemotherapy conditioning regimen to improve gene delivery efficiency by using busulfan, cyclophosphamide and dexamethasone. The X-CGD mice received two iv injections of LVs, and the expression and function of the LV-CYBB gene were analyzed by intracellular gp91-phox staining and DHR123 assay 4 weeks after each injection. Based on flow cytometry, we detected gp91-phox positive cells in the blood as the following, EF1a: 1.14-5.18% and 5.27-14.36%, and miR223: 1.65-5.17% and 4.59-17.89% after the first and the second injections, respectively, as compared with the WT mice: 79.9-87.6%. Functional analyses of ROS showed the following, EF1a: 1.93-5.2% and 2.39-18.51%, miR223: 2.65-6.67% and 3.75-19.8%, after the first and the second injections respectively, as compared with WT: 72.6-85.31% (Figure A). The LV vector copy number (VCN) in the peripheral blood mononuclear cells was detected by qPCR as the following, EF1a: 1.11-2.32% and 1.35-9.32%, and miR223: 1.01-2.39% and 2.71-8.51% after the first and the second injections, respectively. These results indicated that iv LV injection effectively delivered and expressed the LV-CYBB gene in vivo, and repeated injection of the LVs could increase the gene transfer efficiency in the CGD mice. Importantly, after the second injection, we found no antibody response to the LV particle-associated protein p24. However, after 3-12 months, markedly reduced VCN was found in the blood of the treated mice, suggesting exhaustion of the transgenes in the somatic cells. To improve the gene delivery into HSCs, we treated the mice with AMD3100 to mobilize HSCs into peripheral blood. The mice were treated with chemo-conditioning and AMD3100 prior to LV ivinjection. After four weeks, the gp91-phox positive HSCs of total Sca1+ HSCs in blood with or without (+/-) AMD3100 treatment were examined by flow cytometry, and the results showed the following, EF1a: (-) 9.52-15.43%, (+) 16.1-29.4%, and miR223: (-) 4.49-10.35% and (+) 7.06-16.84%. To confirm stem cell gene transfer, we transplanted the bone marrow cells from the LV-CYBB-treated CGD mice into untreated CGD mice. The VCN in blood was examined before (donor mice) and 4 weeks after (recipient mice) the HSCT, and the results showed the following, EF1a: before 4.49% (in the donor) and after 1.05-2.57% (in the recipients), and miR223: before 4.91% (in the donor) and after 1.04-2.69% (in the recipients) (Figure B). This transplantation study confirmed that the AMD3100 treatment effectively increased iv LV gene delivery into HSCs. Conclusion: We have developed an improved LV iv gene delivery strategy by applying chemo-conditioning and AMD3100 mobilization prior to the injection of the LVs into CGD mice. This in vivo LV gene therapy strategy could potentially be translated into future CGD gene therapy applications. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Gene delivery available in molluscan cells by strong promoter discovered from bivalve-infectious virus

Understanding gene functions in marine invertebrates has been limited, largely due to the lack of suitable assay systems. Such a system requires investigative methods that are reproducible and can be quantitatively evaluated, such as a cell line, and a strong promoter that can drive high expression of a transgene. In this study, we established primary cell culture from a marine bivalve mollusc, Mizuhopecten yessoensis. Using scallop primary cells, we optimized electroporation conditions for transfection and carried out a luciferase-based promoter activity assay to identify strong promoter sequences that can drive expression of a gene of interest. We evaluated potential promoter sequences from genes of endogenous and exogenous origin and discovered a strong viral promoter derived from a bivalve-infectious virus, ostreid herpesvirus-1 (OsHV-1). This promoter, we termed OsHV-1 promoter, showed 24.7-fold and 16.1-fold higher activity than the cytomegalovirus immediate early (CMV IE) promoter and the endogenous EF1α promoter, the two most commonly used promoters in bivalves so far. Our GFP assays showed that the OsHV-1 promoter is active not only in scallop cells but also in HEK293 cells and zebrafish embryos. The OsHV-1 promoter practically enables functional analysis of marine molluscan genes, which can contribute to unveiling gene-regulatory networks underlying astonishing regeneration, adaptation, reproduction, and aging in marine invertebrates.

A synthetic transcription platform for programmable gene expression in mammalian cells

Precise, scalable, and sustainable control of genetic and cellular activities in mammalian cells is key to developing precision therapeutics and smart biomanufacturing. Here we create a highly tunable, modular, versatile CRISPR-based synthetic transcription system for the programmable control of gene expression and cellular phenotypes in mammalian cells. Genetic circuits consisting of well-characterized libraries of guide RNAs, binding motifs of synthetic operators, transcriptional activators, and additional genetic regulatory elements express mammalian genes in a highly predictable and tunable manner. We demonstrate the programmable control of reporter genes episomally and chromosomally, with up to 25-fold more activity than seen with the EF1α promoter, in multiple cell types. We use these circuits to program the secretion of human monoclonal antibodies and to control T-cell effector function marked by interferon-γ production. Antibody titers and interferon-γ concentrations significantly correlate with synthetic promoter strengths, providing a platform for programming gene expression and cellular function in diverse applications.

CT-167 Using the Sodium Iodide Symporter to Visualize CAR-T Cell Trafficking

Chimeric antigen receptor T (CAR-T) cell therapy revolutionized the treatment of refractory B cell malignancies, but relapses occur through a variety of incompletely understood mechanisms. Currently, tracking CAR-T expansion and persistence in patients is limited to peripheral blood sampling, but this approach provides no insights into how and where CAR-T cells traffic beyond the peripheral blood or how cellular localization may impact persistence and efficacy. Furthermore, costimulatory endodomains that are known to influence CAR-T cell phenotype have unclear downstream effects on how CAR-T cells traffic. The sodium iodide symporter (NIS) is a plasma membrane glycoprotein that actively uptakes iodide and its analogs, and it can be transduced into various cell types in preclinical models allowing sensitive and specific PET/SPECT imaging. Coexpression of NIS with CAR on T cells would allow real-time, in vivo imaging of CAR-T cells and aid in understanding CAR-T cell biology and trafficking. Using Golden Gate modular vector construction, multiple anti-CD20 CAR constructs with specificity for both human and non-human primate (NHP) CD20 antigens were generated. Each construct included one of several costimulatory domains (4-1BB, CD28, or CD27), a standard CD3-zeta signaling domain, and either the rhesus-NIS reporter or truncated EGFR following a short ribosomal skip sequence peptide, allowing transduction under control of the same EF1a promoter. CAR was effectively cotransduced with NIS in both human and NHP primary T cells with no effect of NIS on CAR-T cell-mediated cytotoxicity against CD20-expressing Raji cells in vitro compared to control. Cytotoxicity was antigen-specific as no difference was seen against CD20- control cells. Functional iodide and [18F]-TFB, an iodide analog, uptake via NIS was specific to NIS-transduced cells and was appropriately inhibited by coincubation with KClO4. An NSG mouse xenograft model will be used to track the localization, expansion, efficacy, and persistence of CAR-T constructs against Raji lymphoma cells. Different costimulatory domains appear to elicit only slight differences in cytokine production in vitro but will be further studied for differences in efficacy and trafficking in vivo in mice and later in a syngeneic NHP model.

Multimodal analyses of a non-human primate model harboring mutant amyloid precursor protein transgenes driven by the human EF1α promoter.

Alzheimer’s disease (AD) is the leading cause of dementia which afflicts tens of millions of people worldwide. Despite many scientific progresses to dissect the AD’s molecular basis from studies on various mouse models, it has been suffered from evolutionary species differences. Here, we report generation of a non-human primate (NHP), common marmoset model ubiquitously expressing Amyloid-beta precursor protein (APP) transgenes with the Swedish (KM670/671NL) and Indiana (V717F) mutations. The transgene integration of generated two transgenic marmosets (TG1&TG2) was thoroughly investigated by genomic PCR, whole-genome sequencing, and fluorescence in situ hybridization. By reprogramming, we confirmed the validity of transgene expression in induced neurons in vitro. Moreover, we discovered structural changes in specific brain regions of transgenic marmosets by magnetic resonance imaging analysis, including in the entorhinal cortex and hippocampus. In immunohistochemistry, we detected increased Aβ plaque-like structures in TG1 brain at 7 years old, although evident neuronal loss or glial inflammation was not observed. Thus, this study summarizes our attempt to establish an NHP AD model. Although the transgenesis approach alone seemed not sufficient to fully recapitulate AD in NHPs, it may be beneficial for drug development and further disease modeling by combination with other genetically engineered models and disease-inducing approaches.

The human EF1a promoter does not provide expression of the transgene in mice.

In this work, we set out to create mice susceptible to the SARS-CoV-2 coronavirus. To ensure the ubiquitous expression of the human ACE2 gene we used the human EF1a promoter. Using pronuclear microinjection of the transgene construct, we obtained six founders with the insertion of the EF1a-hACE2 transgene, from which four independent mouse lines were established. Unfortunately, only one line had low levels of hACE2 expression in some organs. In addition, we did not detect the hACE2 protein in primary lung fibroblasts from any of the transgenic lines. Bisulfite sequencing analysis revealed that the EF1a promoter was hypermethylated in the genomes of transgenic animals. Extensive analysis of published works about transgenic animals indicated that EF1a transgenic constructs are frequently inactive. Thus, our case cautions against using the EF1a promoter to generate transgenic animals, as it is prone to epigenetic silencing.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11248-022-00319-5.

The application of lentiviral vectors for the establishment of TGFβ2-induced ocular hypertension in C57BL/6J mice

Elevated levels of TGFβ2 in the aqueous humor is associated with the pathological changes in the trabecular meshwork (TM). These changes lead to ocular hypertension (OHT), the most important risk factor for the development and progression of primary open angle glaucoma (POAG), a leading cause of blindness worldwide. Therefore, TGFβ2 is frequently used to develop OHT models including in perfusion cultured eyes and in mouse eyes. Adenovirus-mediated overexpression of human mutant TGFβ2 has demonstrated great success in increasing intraocular pressure (IOP) in mouse eyes. However, adenoviruses have limited capacity for a foreign gene, induce transient expression, and may cause ocular inflammation. Here, we explored the potential of using lentiviral vectors carrying the mutant human TGFβ2C226S/C228S (ΔhTGFβ2C226S/C228S) gene expression cassette for the induction of OHT in C57BL/6J mice. Lentiviral vectors using CMV or EF1α promoter to drive the expression of ΔhTGFβ2C226S/C228S were injected into one of the mouse eyes and the fellow eye was injected with the same vector but expressing GFP/mCherry as controls. Both intravitreal and intracameral injection routes were tested in male and female mice. We did not observe significant IOP changes using either promoter or injection route at the dose of 8 × 105 PFU/eye. Immunostaining showed normal anterior chamber angle structures and a slight increase in TGFβ2 expression in the TM of the eyes receiving intracameral viral injection but not in those receiving intravitreal viral injection. At the dose of 2 × 106 PFU/eye, intracameral injection of the lentiviral vector with the CMV-ΔhTGFβ2C226S/C228S cassette induced significant IOP elevation and increased the expression of TGFβ2 and fibronectin isoform EDA in the TM. Our data suggest that lentiviral doses are important for establishing the TGFβ2-induced OHT model in the C57BL/6J strain.

CD19/22 CAR T cells in children and young adults with B-ALL: phase 1 results and development of a novel bicistronic CAR

AbstractRemission durability following single-antigen targeted chimeric antigen receptor (CAR) T-cells is limited by antigen modulation, which may be overcome with combinatorial targeting. Building upon our experiences targeting CD19 and CD22 in B-cell acute lymphoblastic leukemia (B-ALL), we report on our phase 1 dose-escalation study of a novel murine stem cell virus (MSCV)-CD19/CD22-4-1BB bivalent CAR T-cell (CD19.22.BBζ) for children and young adults (CAYA) with B-cell malignancies. Primary objectives included toxicity and dose finding. Secondary objectives included response rates and relapse-free survival (RFS). Biologic correlatives included laboratory investigations, CAR T-cell expansion and cytokine profiling. Twenty patients, ages 5.4 to 34.6 years, with B-ALL received CD19.22.BBζ. The complete response (CR) rate was 60% (12 of 20) in the full cohort and 71.4% (10 of 14) in CAR-naïve patients. Ten (50%) developed cytokine release syndrome (CRS), with 3 (15%) having ≥ grade 3 CRS and only 1 experiencing neurotoxicity (grade 3). The 6- and 12-month RFS in those achieving CR was 80.8% (95% confidence interval [CI]: 42.4%-94.9%) and 57.7% (95% CI: 22.1%-81.9%), respectively. Limited CAR T-cell expansion and persistence of MSCV-CD19.22.BBζ compared with EF1α-CD22.BBζ prompted laboratory investigations comparing EF1α vs MSCV promoters, which did not reveal major differences. Limited CD22 targeting with CD19.22.BBζ, as evaluated by ex vivo cytokine secretion and leukemia eradication in humanized mice, led to development of a novel bicistronic CD19.28ζ/CD22.BBζ construct with enhanced cytokine production against CD22. With demonstrated safety and efficacy of CD19.22.BBζ in a heavily pretreated CAYA B-ALL cohort, further optimization of combinatorial antigen targeting serves to overcome identified limitations (www.clinicaltrials.gov #NCT03448393).

Functional genome-wide short hairpin RNA library screening identifies key molecules for extracellular vesicle secretion from microglia

SUMMARYActivated microglia release extracellular vesicles (EVs) as modulators of brain homeostasis and innate immunity. However, the molecules critical for regulating EV production from microglia are poorly understood. Here we establish a murine microglial cell model to monitor EV secretion by measuring the fluorescence signal of tdTomato, which is linked to tetraspanin CD63. Stimulation of tdTomato+ cells with ATP induces rapid secretion of EVs and a reduction in cellular tdTomato intensity, reflecting EV secretion. We generate a GFP+ tdTomato+ cell library expressing TurboGFP and barcoded short hairpin RNAs for genome-wide screening using next-generation sequencing. We identify Mcfd2, Sepp1, and Sdc1 as critical regulators of ATP-induced EV secretion from murine microglia. Small interfering RNA (siRNA-based) silencing of each of these genes suppresses lipopolysaccharide- and ATP-induced inflammasome activation, as determined by interleukin-1β release from primary cultured murine microglia. These molecules are critical for microglial EV secretion and are potential therapeutic targets for neuroinflammatory disorders.

3D-organoid culture supports differentiation of human CAR+ iPSCs into highly functional CAR Tcells.

Unlimited generation of chimeric antigen receptor (CAR) Tcells from human-induced pluripotent stem cells (iPSCs) is an attractive approach for "off-the-shelf" CAR Tcell immunotherapy. Approaches to efficiently differentiate iPSCs into canonical αβ Tcell lineages, while maintaining CAR expression and functionality, however, have been challenging. We report that iPSCs reprogramed from CD62L+ naive and memory Tcells followed by CD19-CAR engineering and 3D-organoid system differentiation confers products with conventional CD8αβ-positive CAR Tcell characteristics. Expanded iPSC CD19-CAR Tcells showed comparable antigen-specific activation, degranulation, cytotoxicity, and cytokine secretion compared with conventional CD19-CAR Tcells and maintained homogeneous expression of the TCR derived from the initial clone. iPSC CD19-CAR Tcells also mediated potent antitumor activity invivo, prolonging survival of mice with CD19+ human tumor xenografts. Our study establishes feasible methodologies to generate highly functional CAR Tcells from iPSCs to support the development of "off-the-shelf" manufacturing strategies.

CRISPR/Cas9 editing of directly reprogrammed myogenic progenitors restores dystrophin expression in a mouse model of muscular dystrophy.

SummaryGenetic mutations in dystrophin manifest in Duchenne muscular dystrophy (DMD), the most commonly inherited muscle disease. Here, we report on reprogramming of fibroblasts from two DMD mouse models into induced myogenic progenitor cells (iMPCs) by MyoD overexpression in concert with small molecule treatment. DMD iMPCs proliferate extensively, while expressing myogenic stem cell markers including Pax7 and Myf5. Additionally, DMD iMPCs readily give rise to multinucleated myofibers that express mature skeletal muscle markers; however, they lack DYSTROPHIN expression. Utilizing an exon skipping-based approach with CRISPR/Cas9, we report on genetic correction of the dystrophin mutation in DMD iMPCs and restoration of protein expression in vitro. Furthermore, engraftment of corrected DMD iMPCs into the muscles of dystrophic mice restored DYSTROPHIN expression and contributed to the muscle stem cell reservoir. Collectively, our findings report on a novel in vitro cellular model for DMD and utilize it in conjunction with gene editing to restore DYSTROPHIN expression in vivo.

The Titer of the Lentiviral Vector Encoding Chimeric TRIM5α-HRH Gene is Reduced Due to Expression of TRIM5α-HRH in Producer Cells and the Negative Effect of Ef1α Promoter

The Titer of the Lentiviral Vector Encoding Chimeric TRIM5α-HRH Gene is Reduced Due to Expression of TRIM5α-HRH in Producer Cells and the Negative Effect of Ef1α Promoter

Synthetic biology approach to developing all-in-one baculovirus vector using mammalian introns and miRNA binding sites

BackgroundInsect baculovirus is a promising vector for gene delivery into mammalian cells. We developed a Cre/loxP-based hybrid baculovirus comprising two viruses: one expressing Cre recombinase and the other harboring the transgene flanked by two loxP sites. Co-transduction of mammalian cells with two viruses confers Cre expression, which excises the loxP-flanking cassette off baculovirus genome and catalyzes DNA minicircle formation, thereby prolonging transgene expression. Two separate baculoviruses avoid undesirable recombination and loss of transgene during virus production process, but reduces gene delivery efficiency and complicates applications. MethodsTo tackle this problem, we exploited synthetic biology strategy to control Cre expression and develop an all-in-one baculovirus harboring both cre and loxP-flanking transgene cassette. We controlled cre transcription with a mammalian EF-1α promoter, and regulated cre translation with an intron inserted within the coding region and bantam miRNA binding site at the 3′UTR. Significant findingsThe all-in-one baculovirus vector selectively conferred Cre/loxP-mediated recombination in mammalian cells, but not in E. coli and Sf-9 cells, hence circumventing transgene excision from the virus genome during gene cloning in E. coli and virus amplification in insect cells. The all-in-on vector enabled formation of DNA minicircle in mammalian cells at efficiencies exceeding 80% and implicated its potential for gene delivery. Our design may be expanded to other gene delivery systems that require two separate vectors and is beneficial to gene therapy applications.

Absence of PEXEL-Dependent Protein Export in Plasmodium Liver Stages Cannot Be Restored by Gain of the HSP101 Protein Translocon ATPase.

Host cell remodeling is critical for successful Plasmodium replication inside erythrocytes and achieved by targeted export of parasite-encoded proteins. In contrast, during liver infection the malarial parasite appears to avoid protein export, perhaps to limit exposure of parasite antigens by infected liver cells. HSP101, the force-generating ATPase of the protein translocon of exported proteins (PTEX) is the only component that is switched off during early liver infection. Here, we generated transgenic Plasmodium berghei parasite lines that restore liver stage expression of HSP101. HSP101 expression in infected hepatocytes was achieved by swapping the endogenous promoter with the ptex150 promoter and by inserting an additional copy under the control of the elongation one alpha (ef1α) promoter. Both promoters drive constitutive and, hence, also pre-erythrocytic expression. Transgenic parasites were able to complete the life cycle, but failed to export PEXEL-proteins in early liver stages. Our results suggest that PTEX-dependent early liver stage export cannot be restored by addition of HSP101, indicative of alternative export complexes or other functions of the PTEX core complex during liver infection.

Development of Minicircle Vectors Encoding COL7A1 Gene with Human Promoters for Non-Viral Gene Therapy for Recessive Dystrophic Epidermolysis Bullosa.

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare autosomal inherited skin disorder caused by mutations in the COL7A1 gene that encodes type VII collagen (C7). The development of an efficient gene replacement strategy for RDEB is mainly hindered by the lack of vectors able to encapsulate and transfect the large cDNA size of this gene. To address this problem, our group has opted to use polymeric-based non-viral delivery systems and minicircle DNA. With this approach, safety is improved by avoiding the usage of viruses, the absence of bacterial backbone, and the replacement of the control viral cytomegalovirus (CMV) promoter of the gene with human promoters. All the promoters showed impressive C7 expression in RDEB skin cells, with eukaryotic translation elongation factor 1 α (EF1α) promoter producing higher C7 expression levels than CMV following minicircle induction, and COL7A1 tissue-specific promoter (C7P) generating C7 levels similar to normal human epidermal keratinocytes. The improved system developed here has a high potential for use as a non-viral topical treatment to restore C7 in RDEB patients efficiently and safely, and to be adapted to other genetic conditions.

TAMI-35. DETECTING SINGLE-CELL INTERACTIONS IN ORGANOTYPIC CULTURES OF GLIOBLASTOMA USING BARCODED RABIES VIRUS

Abstract Cell-cell interactions are thought to drive tumor-promoting signals in the microenvironment of glioblastoma, but standard approaches for single cell analysis do not directly identify cell interactions and the mechanisms that mediate them. We recently developed a novel method to analyze cell-cell interactions—rabies barcode interaction detection followed by sequencing (RABID-seq), which combines barcoded viral tracing and single-cell RNA sequencing (scRNAseq). RABID-seq was first implemented in transgenic mice to investigate the interactions of astrocytes with other cells in the CNS enabling the study of astrocyte connectome perturbations and candidate therapeutic targets in multiple sclerosis and its pre-clinical model, experimental autoimmune encephalomyelitis (EAE). Here, we report the first use of RABID-seq in human tissues in organotypic cultures established from three IDH-wildtype glioblastoma (GBM) patients. In organotypic GBM cultures, initial infection by pseudotyped barcoded rabies virus deficient for viral glycoprotein was achieved after previous culture transduction with a lentivirus containing the avian TVA receptor and rabies glycoprotein under the human EF1a promoter. We employed this system to initially infect approximately 1,000 malignant or non malignant cells in the tumor microenvironment. After five days, infected cells were isolated from cultures and processed for single cell analysis using SMART seq. We were able to capture at least 6,000 interacting cells per tumor specimen, from which barcodes were recovered and cDNA was sent for sequencing. Here we present connectomic data from our initial cohort of three glioblastoma patients as an introduction to RABID-seq, with a focus on astrocyte-tumor interactions. Candidate mechanisms of cellular interactions will undergo functional validation in murine models of glioblastoma.

Functional Consequence and Therapeutic Targeting of Cryptic ALK Fusions (ALK fus) in Monosomy7 AML

Monosomy 7 (Mono7) AML is one of the most established adverse prognostic markers in AML with over four decades of data on response and outcome in varied clinical trials. However, despite intensive and myeloablative therapies, outcome for this subtype of AML remains dismal with no meaningful advances in therapy in decades. As part of our recently completed discovery efforts in childhood AML (TARGET Pediatric AML; TpAML), we interrogated the transcriptome of 1068 children and young adults treated on COG AAML1031, including 28 cases of Mono7. We discovered novel cryptic fusions involving the Anaplastic Tyrosine Kinase (ALK) gene that were exclusively seen in 4 of 28 Mono7 patients (14.3%) and not detected in the remaining 1064 patients (p<0.001). These ALK fusions (ALK fus) included SPTBN1-ALK (n=3) or RANBP2-ALK (n=1) (figure 1A) and all 4 cases included the entire kinase domain of the ALK gene. Expression of ALK transcript was evaluated in Mono7 patients with and without ALK fus to determine whether these fusions lead to induction/upregulation of ALK. As demonstrated in figure 1B, the only patients with any ALK expression were those with ALK fus positive Mono7.Expression of the resultant onco-proteins of the ALK fus was confirmed by transfection of parental HEK293T cells with the oncofusion and western blot analysis of the protein lysates. As shown in the western blot in figure 1C, immunoblotting of the lysates from ALK fus cells with ALK antibody confirmed expression of the appropriate ALK+ fusion oncoprotein. Under experimental conditions, fusion involving SPTBN1-ALK appeared to generate higher levels of the fusion onco-protein compared to that of RANBP2-ALK fusion. Confirmation of the fusion onco-protein expression further validates the possibility of the functional significance and potential targetability of these fusions.The ALK gene codes for a receptor tyrosine kinase belonging to a family of protein kinases linked to unregulated cell growth which play a key role in CNS development. Alterations of the ALK gene are commonly seen in Non-Small Cell Lung Cancer (NSCLC), Anaplastic Large-Cell Lymphomas, and Neuroblastomas. We further inquired about the functionality of the ALK fus and whether they may confer cytokine-independent proliferation. The ALK fus were cloned from patient samples into pCSII, a direct GFP-tagged lentiviral backbone under the Ef1α promoter; followed by Sanger sequencing to verify the insert. IL-3 dependent Ba/F3 cells were transduced with the GFP tagged lentiviral vectors containing the SPTBN1-ALK or RANBP2-ALK fusion transcripts.Transduced cells were sorted to GFP homogeneity and growth parameters evaluated post-IL-3 withdrawal. In contrast to the parental line, which rapidly died in the absence of cytokines, cells expressing either SPTBN1-ALK or RANBP2-ALK sustained growth and rapidly proliferated in cytokine-free media, suggesting a conferred transformation event by the fusions, figure 1D. SPTBN1-ALK fusion appears to show more transforming potential with more rapid cytokine-free proliferation compared to that of RANBP2-ALK fusion. The observed differential growth pattern with the two ALK fus correlates with the differential expression of the two oncoproteins as presented above.We then sought to evaluate the efficacy of Crizotinib as a potential therapy for aberrant ALK fus positive Mono7 AML. Crizotinib has been FDA-approved and demonstrated efficacy in treating ALK positive NSCLC. ALK fus -positive cells were treated with varying doses of Crizotinib in cytokine-free media and cell viability and cell death were determined with the Promega Cell Titer Glow assay after 48 hours in culture. Fusion positive cells show sensitivity to Crizotinib with IC50s of 144nM and 95nM for the SPTBN1-ALK or RANBP2-ALK fusions, respectively.Here we demonstrate experimental data that when newly discovered cryptic ALK fus in Mono7 AML are functional (translation to fusion onco-protein, conferring cytokine independence) and show susceptibility to the ALK inhibitor crizotinib. This data may support effective therapeutic targeting of a subset of this highly refractory AML. [Display omitted] DisclosuresHylkema: Quest Diagnostics Inc: Current equity holder in publicly-traded company; Moderna: Current equity holder in publicly-traded company. OffLabel Disclosure:Crizotinib is a first-generation ALK inhibitor that is FDA-approved for the treatment of Non-Small Cell Lung Cancer, Anaplastic Lymphoma, and Neuroblastoma.