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Induced pluripotent stem cells (iPSCs) are pluripotent cells derived from adult somatic cells. After the pioneering work by Yamanaka, who first generated iPSCs by retroviral transduction of four reprogramming factors, several alternative methods to obtain iPSCs have been developed in order to increase the yield and safety of the process. However, the question remains open on whether the different reprogramming methods can influence the pluripotency features of the derived lines. In this study, three different strategies, based on retroviral vectors, episomal vectors, and Sendai virus vectors, were applied to derive iPSCs from human fibroblasts. The reprogramming efficiency of the methods based on episomal and Sendai virus vectors was higher than that of the retroviral vector-based approach. All human iPSC clones derived with the different methods showed the typical features of pluripotent stem cells, including the expression of alkaline phosphatase and stemness maker genes, and could give rise to the three germ layer derivatives upon embryoid bodies assay. Microarray analysis confirmed the presence of typical stem cell gene expression profiles in all iPSC clones and did not identify any significant difference among reprogramming methods. In conclusion, the use of different reprogramming methods is equivalent and does not affect gene expression profile of the derived human iPSCs. [ABSTRACT FROM AUTHOR]

Background: Liver cancer stem cells (LCSCs) have been shown to express higher levels of microRNA-21 (miR-21). Here, we examine the possible contributions of miR-21 to the phenotype of LCSCs in culture and in xenograft tumors in nude mice. Methods: The hepatocellular carcinoma cell line MHCC-97H was stably transformed with a retroviral vector to establish cells overexpressing miR-21, while a cell line transformed with empty vector served as a negative control. RT-PCR and Western blotting were used to evaluate the effects of miR-21 overexpression on the expression of various LCSC markers, a Transwell assay was used to assess the effects on cell migration and invasion, and a spheroid formation assay was used to examine the effects on clonogenesis. The effects of miR-21 overexpression were also examined in tumors in nude mice. Results: An MHCC-97H cell line was constructed that stably overexpresses miR-21 at 7.78 ± 1.51-fold higher levels than the negative control cell line. Expression of the LCSC markers CD13, Ep-CAM, CD90, and OCT4 was significantly higher in the miR-21-overexpressing cell line than in the negative control at both mRNA and protein levels. The overexpressing cell line formed larger, tighter, and more numerous spheroids. Overexpression of miR-21 was associated with greater cell migration and invasion. Tumors of overexpressing cells in nude mice had a significantly larger mean volume after 34 days of growth (773.62 ± 163.46 mm³) than tumors of negative control cells (502.79 ± 33.94 mm3, p = 0.048), as well as greater mean weight (0.422 ± 0.019 vs. 0.346 ± 0.006 g, p = 0.003). Conclusions: Overexpression of miR-21 strengthens the phenotype of LCSCs, facilitating invasion, migration, and tumorigenesis in hepatocellular carcinoma. [ABSTRACT FROM AUTHOR]

Adoptive immunotherapy using chimeric antigen receptor-expressing T (CAR-T) cells has attracted attention as an efficacious strategy for cancer treatment. To prove the efficacy and safety of CAR-T cell therapy, the elucidation of immunological mechanisms underlying it in mice is required. Although a retroviral vector (Rv) is mainly used for the introduction of CAR to murine T cells, gene transduction efficiency is generally less than 50%. The low transduction efficiency causes poor precision in the functional analysis of CAR-T cells. We attempted to improve the Rv gene transduction protocol to more efficiently generate functional CAR-T cells by optimizing the period of pre-cultivation and antibody stimulation. In the improved protocol, gene transduction efficiency to murine T cells was more than 90%. In addition, almost all of the prepared murine T cells expressed CAR after puromycin selection. These CAR-T cells had antigen-specific cytotoxic activity and secreted multiple cytokines by antigen stimulation. We believe that our optimized gene transduction protocol for murine T cells contributes to the advancement of T cell biology and development of immunotherapy using genetically engineered T cells. [ABSTRACT FROM AUTHOR]

Sequencing data from large cohorts of T-cell acute lymphoblastic leukemia patients identified a significant association between the presence of JAK3 mutations and ectopic HOXA9 expression. Mouse models using a constitutive or novel inducible retroviral expression vector to express the JAK3(M511I) mutant and HOXA9 led to the development of an aggressive leukemia in vivo, with shorter latency than JAK3(M511I) or HOXA9 alone. This was primarily due to the co-binding of STAT5 and HOXA9 to the same genomic loci leading to increased oncogenic JAK-STAT signaling. [ABSTRACT FROM AUTHOR]

Zinc finger protein 809 (ZFP809) belongs to the Kruppel-associated box-containing zinc finger protein (KRAB-ZFP) family and functions in repressing the expression of Moloney murine leukemia virus (MoMLV). ZFP809 binds to the primer-binding site (PBS)located downstream of the MoMLV-long terminal repeat (LTR) and induces epigenetic modifications at integration sites, such as repressive histone modifications and de novo DNA methylation. KRAB-ZFPs contain consensus TGEKP linkers between C2H2 zinc fingers. The phosphorylation of threonine residues within linkers leads to the inactivation of zinc finger binding to target sequences. ZFP809 also contains consensus linkers between zinc fingers. However, the function of ZFP809 linkers remains unknown. In the present study, we constructed ZFP809 proteins containing mutated linkers and examined their ability to silence transgene expression driven by MLV, binding ability to MLV PBS, and cellular localization. The results of the present study revealed that the linkers affected the ability of ZFP809 to silence transgene expression. Furthermore, this effect could be partly attributed to changes in the localization of ZFP809 proteins containing mutated linkers. Further characterization of ZFP809 linkers is required for understanding the functions and features of KRAB-ZFP-containing linkers. [ABSTRACT FROM AUTHOR]

Objective To construct and identify the recombinant retroviral vector containing five copies of hypoxia responsive elements (5HRE) and neurotrophin-3 (NT-3). Methods Using PCR, enzyme digestion and DNA ligase, 5HRE and human derived NT-3 were cloned into the retroviral vector plasmid (pLNCX) to construct the recombinant retroviral vector plasmid pLNCX-5HRE-SV40-NT3-IRES-EGFP. The retrovirus RV-5HRE-NT3 was packaged in the PT67 cells, and then it was purified and concentrated by high-speed centrifugation. After infected for 48h with the concentrated retrovirus, the number of the EGFP positive cells in the NIH 3T3 cells was counted by fluorescence activated cells and sorted to calculate the retrovirus titer. Results The retroviral vector plasmid, pLNCX-5HRE-SV40-NT3-IRES-EGFP, was successfully constructed, and the retrovirus was packaged and defined as RV-5HRE-NT3. After purification and concentration, the retrovirus titer reached 9.1×106cfu/mL. Conclusion The recombinant retroviral vector which carried out hypoxia-regulated expression of NT-3 was successfully constructed. It may provide basis for studies on hypoxia-regulated expression of the exogenous genes. [ABSTRACT FROM AUTHOR]

Introduction Primary cultures of human corneal epithelial (HCE) cells usually cease to grow after four or five passages. This result in a small cell yield for experiments such as the eye irritancy test represents a serious problem for human and animal corneal epithelial research. In the present study, we established an HCE cell line immortalized by simian virus 40 (SV40), a polyomavirus, and characterized the inherent morphologic and cytologic cell properties. Methods Primary cultured HCE cells were infected with a SV40 large T antigen (SV40 T)-expressing retrovirus, and were selected using G418 solution, an aminoglycoside antibiotic. To ensure that the immortalized cell lines express SV40 T and cytokeratin-3, a corneal epithelial-specific marker, we conducted reverse-transcription (RT)-PCR and Western blot analysis. Results These cell lines continued to grow for more than 50 generations, exhibiting a cobble stone-like appearance similar to normal HCE cells and an increased proliferation rate compared to primary cultured HCE cells. RT-PCR results showed that the immortalized cell lines expressed SV40 T while the primary cultured cells did not. In the Western blot assay, protein levels of phosphorylated (Ser15) p53 protein were significantly decreased in the immortalized cell lines while the expression of total p53 protein was constant. In addition, expression of p21 cip1 , a cell cycle protein, was down-regulated in the immortalized cells. Moreover, a cornea epithelium-specific marker, cytokeratin-3 (CK-3), was expressed at equal levels in the immortalized cells and primary HCE cells. Discussion Taken together, these results indicate that immortalized HCE cell lines were successfully established using the SV40-retroviral vector. These cells may be an excellent model for detecting the adverse effects of standard toxic materials and could replace the traditional eye irritation test as an animal-free alternative method. [ABSTRACT FROM AUTHOR]

Members of the kruppel-associated box-containing zinc finger protein (KRAB-ZFP) family mediate a number of cellular processes through binding to target DNA sequences via zinc fingers. Generally, zinc fingers recognize three-nucleotide sequences; however, this rule is not universally applicable. Zinc finger protein 809 (ZFP809) belongs to the KRAB-ZFP family and functions in repressing the expression of Moloney murine leukemia virus (MoMLV) via sequence-specific binding to the primer-binding site (PBS) located downstream of the MoMLV-long terminal repeat (LTR) and the induction of epigenetic modifications at LTR, such as repressive histone modifications and de novo DNA methylation. Previously, we demonstrated the role of the first to fifth zinc fingers of ZFP809 in binding to MLV PBS, indicating these zinc fingers do not recognize MLV PBS as a three-nucleotide sequence. Therefore, in the present study, we constructed truncated and mutated zinc fingers and examined their ability to bind to MLV PBS. The third to fifth zinc fingers of ZFP809 were found to be essential for binding to MLV PBS. Furthermore, the results of the present study indicate that other zinc fingers, which were not directly involved in binding to MLV PBS, may function in potentiating binding and stable protein expression. Further characterization of the amino acid sequences of zinc fingers will help further elucidate the functions and features of KRAB-ZFP and other zinc finger proteins. [ABSTRACT FROM AUTHOR]

Expression of Moloney murine leukemia virus (MoMLV)-typed retroviral vectors is strictly suppressed in immature cells such as embryonic stem cells. The phenomenon known as gene silencing is primed by the sequence-specific binding of the zinc finger protein 809 (ZFP809) to the primer-binding site of the vectors. However, it has yet to be determined whether the ZFP809-mediated gene silencing is maintained over a long period. In this study, we established an experimental system that can monitor gene silencing during a long-term cell culture using flow cytometry technology combined with fluorescent reporters for the expression of ZFP809 and the transgene expression driven by the promoters of interest. Time-course analysis using our system revealed that ZFP809 maintains gene silencing effect even at a longtime period. Furthermore, our system was useful for the monitoring of ZFP809-mediated gene silencing regardless of the types of vectors and cell lines. Time-course monitoring of gene silencing [ABSTRACT FROM PUBLISHER]

Activation of B-cells is initiated by the ligation of B-cell receptors by its cognate antigen, inducing a series of signal cascades. Understanding the molecular mechanisms of these important events is a crucial goal for immunologists. Chimeric B cell receptors provide a powerful tool for analysis of B-cell signal function. However, this method can only be used in tool cells, but cannot be used for in vivo study. Here, we constructed a retroviral vector to encode both heavy chains and light chains of a membrane immunoglobulin, and expressed them in primary B-cells using retroviral gene transfer. Our results demonstrate that the membrane immunoglobulin expressed by retroviral vectors transfer can initiate B-cell receptor-mediated signaling, resulting in the phosphorylation of Syk and Erk1/2 proteins. The results showed that B-cells expressing membrane immunoglobulin can make proliferative responses to cognate antigen both in vitro and in vivo. Therefore, we provide a methodology for rapidly analyzing the downstream signals of B-cell receptors both in vitro and in vivo, which could expedite the identification of proteins involved in B-cell function. [ABSTRACT FROM AUTHOR]

BCR-JAK2 is an infrequent gene fusion found in chronic/acute, myeloid/lymphoid Philadelphia chromosomenegative leukaemia. In this study, we demonstrated that in vivo expression of BCR-JAK2 in mice induces neoplasia, with fatal consequences. Transplantation of BCR-JAK2 bone marrow progenitors promoted splenomegaly, with megakaryocyte infiltration and elevated leukocytosis of myeloid origin. Analysis of peripheral blood revealed the presence of immature myeloid cells, platelet aggregates and ineffective erythropoiesis. A possible molecular mechanism for these observations involved inhibition of apoptosis by deregulated expression of the anti-apoptotic mediator Bcl-xL and the serine/threonine kinase Pim1. Together, these data provide a suitable in vivo molecular mechanism for leukaemia induction by BCR-JAK2 that validates the use of this model as a relevant preclinical tool for the design of new targeted therapies in Philadelphia chromosome-negative leukaemia involving BCR-JAK2-driven activation of the JAK2 pathway. [ABSTRACT FROM AUTHOR]

Lentiviral and gammaretroviral vectors are state-of-the-art tools for transgene expression within target cells. The integration of these vectors can be deliberately suppressed to derive a transient gene expression system based on extrachromosomal circular episomes with intact coding regions. These episomes can be used to deliver DNA templates and to express RNA or protein. Importantly, transient gene transfer avoids the genotoxic side effects of integrating vectors. Restricting their applicability, episomes are rapidly lost upon dilution in dividing target cells. Addressing this limitation, we could establish comparably stable percentages of transgene-positive cells over prolonged time periods in proliferating cells by repeated transductions. Flow cytometry was applied for kinetic analyses to decipher the impact of individual parameters on the kinetics of fluoroprotein expression after episomal retransduction and to visualize sequential and simultaneous transfer of heterologous fluoroproteins. Expression windows could be exactly timed by the number of transduction steps. The kinetics of signal loss was affected by the cell proliferation rate. The transfer of genes encoding fluoroproteins with different half-lives revealed a major impact of protein stability on temporal signal distribution and accumulation, determining optimal retransduction intervals. In addition, sequential transductions proved broad applicability in different cell types and using different envelope pseudotypes without receptor overload. Stable percentages of cells coexpressing multiple transgenes could be generated upon repeated coadministration of different episomal vectors. Alternatively, defined patterns of transgene expression could be recapitulated by sequential transductions. Altogether, we established a methodology to control and adjust a temporally defined window of transgene expression using retroviral episomal vectors. Combined with the highly efficient cell entry of these vectors while avoiding integration, the developed technology is of great significance for a broad panel of applications, including transcription-factor-based induced cell fate conversion and controlled transfer of genetically encoded RNA- or protein-based drugs. © 2015 International Society for Advancement of Cytometry [ABSTRACT FROM AUTHOR]

Ligation-mediated-PCR was performed followed by the mapping of 177 and 150 integration sites from HepG2 and Hek293 transduced with chimera vector carrying recombinant human Factor IX (rhFIX) cDNA, respectively. The sequences were analyzed for chromosome preference, CpG, transcription start site (TSS), repetitive elements, fragile sites and target genes. In HepG2, rhFIX was had an increased preference for chromosomes 6 and 17; the median distance to the nearest CpG islands was 15,240 base pairs and 37 % of the integrations occurred in RefSeq genes. In Hek293, rhFIX had an increased preference for chromosome 5; the median distance to the nearest CpG islands was 209,100 base pairs and 74 % of the integrations occurred in RefSeq genes. The integrations in both cell lines were distant from the TSS. The integration patterns associated with this vector are different in each cell line. [ABSTRACT FROM AUTHOR]

The use of vaccination against the influenza virus remains the most effective method of mitigating the significant morbidity and mortality caused by this virus. Antibodies elicited by currently licensed influenza vaccines are predominantly hemagglutination-inhibition (HI)- competent antibodies that target the globular head of hemagglutinin (HA) thus inhibiting influenza virus entry into target cells. These antibodies predominantly confer homosubtypic/ strain specific protection and only rarely confer heterosubtypic protection. However, recent academia or pharma-led R&D toward the production of a "universal vaccine" has centered on the elicitation of antibodies directed against the stalk of the influenza HA that has been shown to confer broad protection across a range of different subtypes (H1- H16). The accurate and sensitive measurement of antibody responses elicited by these "next-generation" influenza vaccines is, however, hampered by the lack of sensitivity of the traditional influenza serological assays HI, single radial hemolysis, and microneutralization. Assays utilizing pseudotypes, chimeric viruses bearing influenza glycoproteins, have been shown to be highly efficient for the measurement of homosubtypic and heterosubtypic broadly neutralizing antibodies, making them ideal serological tools for the study of cross-protective responses against multiple influenza subtypes with pandemic potential. In this review, we will analyze and compare literature involving the production of influenza pseudotypes with particular emphasis on their use in serum antibody neutralization assays. This will enable us to establish the parameters required for optimization and propose a consensus protocol to be employed for the further deployment of these assays in influenza vaccine immunogenicity studies. [ABSTRACT FROM AUTHOR]

Insertional leukemogenesis represents the major risk factor of hematopoietic stem cell (HSC) based gene therapy utilizing integrating viral vectors. To develop a pre-clinical model for the evaluation of vector-related genotoxicity directly in the relevant human target cells, cord blood CD34+ HSCs were transplanted into immunodeficient NOD.SCID.IL2rg−/− (NSG) mice after transduction with an LTR-driven gammaretroviral vector (GV). Furthermore, we specifically investigated the effect of prolonged in vitro culture in the presence of cytokines recently described to promote HSC expansion or maintenance. Clonality of human hematopoiesis in NSG mice was assessed by high throughput insertion site analyses and validated by insertion site-specific PCR depicting a GV typical integration profile with insertion sites resembling to 25% those of clinical studies. No overrepresentation of integrations in the vicinity of cancer-related genes was observed, however, several dominant clones were identified including two clones harboring integrations in the ANGPT1 and near the ANGPT2 genes associated with deregulated ANGPT1- and ANGPT2-mRNA levels. While these data underscore the potential value of the NSG model, our studies also identified short-comings such as overall low numbers of engrafted HSCs, limited in vivo observation time, and the challenges of in-depth insertion site analyses by low contribution of gene modified hematopoiesis.

MazF, an endoribonuclease encoded by Escherichia coli, specifically cleaves the ACA (adenine–cytosine–adenine) sequence of single-stranded RNAs. Conditional expression of MazF under the control of the HIV-1 LTR promoter rendered CD4+ T cells resistant to HIV-1 replication without affecting cell growth. To investigate the safety, persistence and efficacy of MazF-modified CD4+ T cells in a nonhuman primate model in vivo, rhesus macaques were infected with a pathogenic simian/human immunodeficiency virus (SHIV) and transplanted with autologous MazF-modified CD4+ T cells. MazF-modified CD4+ T cells were clearly detected throughout the experimental period of more than 6 months. The CD4+ T cell count values increased in all four rhesus macaques. Moreover, the transplantation of the MazF-modified CD4+ T cells was not immunogenic, and did not elicit cellular or humoral immune responses. These data suggest that the autologous transplantation of MazF-modified CD4+ T cells in the presence of SHIV is effective, safe and not immunogenic, indicating that this is an attractive strategy for HIV-1 gene therapy.

Recently, adipose tissue-derived mesenchymal stem cells (MSCs) were reported to be a valuable cell source for generating induced pluripotent stem (iPS) cells because adipose tissue is readily obtainable and possesses high quantities of MSCs. To date, little research has been conducted to characterize the efficiency of iPS induction in adipose tissue. Human iPS cells were generated from adipose tissue-derived MSCs (AT-MSCs) and stromal cells (AT-SCs) via a retroviral delivery system. The reprogramming efficiency of AT-MSCs and AT-SCs were 0.008 and 0.014%, respectively, in terms of the expression of the TRA-1-60 antibody and 0.023 and 0.041%, respectively, regarding alkaline phosphatase staining. This differential reprogramming capability resulted from different levels of viral infectivity between the two cell types. Viral infectivity using pMXs-IRES-GFP was notably low in AT-MSCs and the quantities of OSKM (OCT4, SOX2, KLF4 and c-MYC) in AT-MSCs were 22.5-31.6% of AT-SCs. In conclusion, the amount of transgenes leads to a higher reprogramming efficiency in AT-SCs compared with AT-MSCs. The present study shows that the induction efficiency of pluripotent cells from somatic or adult stem cells could depend on the viral susceptibility of the target cells. Therefore, non-MSCs could be a more efficient source for reprogramming by retrovirus-mediated iPS induction. [ABSTRACT FROM AUTHOR]

Gene transfer technology and its application to human gene therapy greatly expanded in the last decade. One area of investigation that appears particularly promising is the transfer of new genetic material into T cells for the potential treatment of cancer. Herein, we describe several core technologies that now yield high-efficiency gene transfer into primary human T cells. These gene transfer techniques include viral-based gene transfer methods based on modified Retroviridae and non-viral methods such as DNA-based transposons and direct transfer of mRNA by electroporation. Where specific examples are cited, we emphasize the transfer of chimeric antigen receptors (CARs) to T cells, which permits engineered T cells to recognize potential tumor antigens.

Retrovirus population diversity within infected hosts is commonly high due in part to elevated rates of replication, mutation, and recombination. This high genetic diversity often complicates the development of effective diagnostics, vaccines, and antiviral drugs. This review highlights the diverse vectors and approaches that have been used to examine mutation and recombination in retroviruses. Retroviral vectors for these purposes can broadly be divided into two categories: those that utilize reporter genes as mutation or recombination targets and those that utilize viral genes as targets of mutation or recombination. Reporter gene vectors greatly facilitate the detection, quantification, and characterization of mutants and/or recombinants, but may not fully recapitulate the patterns of mutagenesis or recombination observed in native viral gene sequences. In contrast, the detection of mutations or recombination events directly in viral genes is more biologically relevant but also typically more challenging and inefficient. We will highlight the advantages and disadvantages of the various vectors and approaches used as well as propose ways in which they could be improved. [ABSTRACT FROM AUTHOR]

Introduction: Hematopoietic stem cells are always in a quiescence state. Since they need retroviral transduction to infect dividing cells, they are resistant to retrovirus transduction. They need to be pre-stimulated by a cytokine cocktail. For proliferation without maturation, we suggest MIP-1α as a novel factor. Material and methods: Retroviral vector produced by PG13/LN C8 cells titter on Hela cells. Then, the CD34+ cells of cord blood can be pre-stimulated in a serum- free media supplemented with SCF, Flt3,TPO,IL6 in the presence and absence of 50 ng/ml MIP-1α. Transduction efficiency was assessed by a semi-quantitative PCR for the neomycin gene. Results: A PCR analysis of the neomycin gene in CD34+ cells revealed an improved transduction of cord blood cells in the presence of MIP-1α 65%, in comparison to its absence: 40.7%. Conclusion: the addition of MIP-1α to the cytokine cocktail improves the transduction efficiency of cord blood hematopoietic progenitor cells. Further studies are required to clarify its effect on the functional properties of CD34+ cells.

Stem cell gene therapy approaches for Human Immunodeficiency Virus (HIV) infection have been explored in clinical trials and several anti-HIV genes delivered by retroviral vectors were shown to block HIV replication. However, gammaretroviral and lentiviral based retroviral vectors have limitations for delivery of anti-HIV genes into hematopoietic stem cells (HSC). Foamy virus vectors have several advantages including efficient delivery of transgenes into HSC in large animal models, and a potentially safer integration profile. This review focuses on novel anti-HIV transgenes and the potential of foamy virus vectors for HSC gene therapy of HIV.

Retroviral vector gene therapy is a promising approach to treating HIV-1. However, integrated vectors are mutagens with the potential to dysregulate nearby genes and cause severe adverse side effects. Leukemia has already been a documented severe adverse event in gene therapy clinical trials for the treatment of primary immunodeficiencies. These side effects will need to be reduced or avoided if retroviral vectors are to be used clinically for HIV-1 treatment. The addition of chromatin insulators to retroviral vectors is a potential strategy for reducing adverse side effects. Insulators have already been effectively used in retroviral vectors to reduce genotoxicity in pre-clinical studies. Here, we will review how insulators function, genotoxicity in gene therapy clinical trials, the design of insulated retroviral vectors, promising results from insulated retroviral vector studies, and considerations for the development of insulated retroviral treatment vectors for HIV-1 gene therapy.

Highlights: [•] We modified retroviral vector to insert DNA fragment with homologous recombination. [•] We cloned TCR-cDNAs into modified retroviral vector with homologous recombination. [•] Modified retroviral vectors are powerful tools for high-throughput cloning of cDNA. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To construct the retroviral vector pLEGFP-N1-telomerase reverse transcriptase (TERT) and to investigate the expression of TERT in neonatal mouse hypodermal cells. Methods: The polymerase chain reaction (PCR)-amplified TERT gene was inserted into plasmid pLEGFP-N1. The positive clone was identified by restriction enzyme digestion and sequencing, then was transfected into packaging cells to produce retrovirus particles. Neonatal mouse hypodermal cells were infected with the virus to generate a stable cell line. The TERT mRNA expression level, telomerase activity, and enhanced green fluorescent protein (EGFP) expression level were analyzed. Results: Retroviral vector pLEGFP-N1-TERT was constructed successfully, and a stable cell line of neonatal mouse hypodermal cells expressing EGFP was established. Western blot and immunohistochemical assay showed that the expression level of TERT was significantly elevated in the neonatal mouse hypodermal cells. Conclusions: A high titer of retrovirus pLEGFP-N1-TERT mediates high-level expression of the exogenous TERT gene in the neonatal mouse hypodermal cells. This protocol has potential applications for skin tissue engineering and cell transplantation therapy. [Copyright &y& Elsevier]

Mucopolysaccharidosis VII (MPS VII) is due to deficient activity of the lysosomal enzyme β-glucuronidase (GUSB) and results in the accumulation of glycosaminoglycans (GAGs). This study determined the long-term effect of neonatal intravenous injection of a gamma retroviral vector (RV) on cardiac valve disease in MPS VII dogs. Transduced hepatocytes secreted GUSB into the blood for up to 11years at levels similar to or greater than those achieved with enzyme replacement therapy (ERT). Valve regurgitation and thickening were scored from 0 (normal) to +4 (severely abnormal). At 1year, untreated MPS VII dogs had mitral regurgitation, mitral valve thickening, aortic regurgitation, and aortic valve thickening scores of 2.3±0.7, 2.3±0.6, 1.8±0.5, and 1.6±0.7, respectively, which were higher than the values of 0.6±0.1, 0.1±0.4, 0.3±0.8, and 0.1±0.4, respectively, in treated MPS VII dogs. Treated MPS VII dogs maintained low aortic regurgitation and aortic valve thickening scores in their lifetime. Although mitral regurgitation and mitral valve thickening scores increased to 2.0 at ≥8years of age in the treated MPS VII dogs, older normal dogs from the colony had similar scores, making it difficult to assess mitral valve disease. Older treated dogs had calcification within the mitral and the aortic valve annulus, while GUSB staining demonstrated enzyme activity within the mitral valve. We conclude that neonatal RV-mediated gene therapy reduced cardiac valve disease in MPS VII dogs for up to 11years, and propose that neonatal initiation of ERT should have a similar effect. [ABSTRACT FROM AUTHOR]

Evaluation of: Aiuti A, Biasco L, Scaramuzza S et al. Lentiviral hematopoietic stem cell gene therapy in patients with Wiskott-Aldrich syndrome. Science 341(6148), 1233151 (2013). Wiskott-Aldrich syndrome (WAS), an X-linked primary immunodeficiency disease (PID) with unique and characteristic features, had been considered to be a good candidate for gene therapy. In 2010, hematopoietic stem cell (HSC) gene therapy, using a retroviral vector, was performed for WAS patients; however, concerns remain regarding the long-term safety of this therapy as several patients with PID developed myeloproliferative diseases due to insertional mutagenesis related to HSC gene therapy using retroviral vectors. Aiuti et al. first reported HSC gene therapy for WAS using a lentiviral vector and compared the safety and efficacy of the two therapies in the context of the same disease background. They undertook a detailed study of the vector integration sites and concluded that lentiviral HSC gene therapy was safer than retroviral gene therapy. [ABSTRACT FROM AUTHOR]

Abstract: Since the introduction of Doxil® on the market nearly 20years ago, a number of nanomedicines have become part of treatment regimens in the clinic. With the exception of antibody–drug conjugates, these nanomedicines are all devoid of targeting ligands and rely solely on their physicochemical properties and the (patho)physiological processes in the body for their biodistribution and targeting capability. At the same time, many preclinical studies have reported on nanomedicines exposing targeting ligands, or ligand-targeted nanomedicines, yet none of these have been approved at this moment. In the present review, we provide a concise overview of 13 ligand-targeted particulate nanomedicines (ligand-targeted PNMs) that have progressed into clinical trials. The progress of each ligand-targeted PNM is discussed based on available (pre)clinical data. Main conclusions of these analyses are that (a) ligand-targeted PNMs have proven to be safe and efficacious in preclinical models; (b) the vast majority of ligand-targeted PNMs is generated for the treatment of cancer; (c) contribution of targeting ligands to the PNM efficacy is not unambiguously proven; and (d) targeting ligands do not cause localization of the PNM within the target tissue, but rather provide benefits in terms of target cell internalization and target tissue retention once the PNM has arrived at the target site. Increased understanding of the in vivo fate and interactions of the ligand-targeted PNMs with proteins and cells in the human body is mandatory to rationally advance the clinical translation of ligand-targeted PNMs. Future perspectives for ligand-targeted PNM approaches include the delivery of drugs that are unable or inefficient in passing cellular membranes, treatment of drug resistant tumors, targeting of the tumor blood supply, the generation of targeted vaccines and nanomedicines that are able to cross the blood–brain barrier. [Copyright &y& Elsevier]

Abstract: Introduction: Preclinical studies have demonstrated that tumor-reactive T cells expressing the interleukin (IL)-15 transgene had enhanced activity. Gene therapy strategies using IL-15 should include a safety mechanism in anticipation of possible adverse effects because IL-15 overexpression has been implicated in autoimmune disorders and may be involved in the pathogenesis of some leukemias. We developed a retroviral vector carrying both IL-15 and the herpes simplex virus-thymidine kinase (HSV-TK) suicide gene and characterized its application in the transduction of human T lymphocytes. Methods: A retroviral vector carrying IL-15 and HSV-TK genes was optimized for the transduction of human T lymphocytes. IL-15 production was measured by enzyme-linked immunosorbent assay. Thymidine incorporation and cell viability assays were used to assess the efficacy of the HSV-TK suicide gene. Genetically modified tumor-infiltrating lymphocytes (TILs) were assayed for survival after withdrawal from exogenous IL-2. The activity and specificity of retrovirally transduced TILs were assessed using tumor coculture assays. Results: Human T cells transduced with the IL-15 HSV-TK vector exhibited thymidine uptake in the absence of exogenous cytokine support and survived in culture for up to 80 d without IL-2. IL-15 HSV-TK–transduced T cells were efficiently killed by ganciclovir at concentrations as low as 0.1 μM. TILs transduced with the IL-15 HSV-TK vector retained specific recognition of HLA-A2+, MART1+ melanomas, even after withdrawal of IL-2. Conclusions: Human T lymphocytes genetically modified with the IL-15 HSV-TK retroviral vector retained the ability to recognize tumor antigen while gaining the ability to secrete IL-15 and prolong their own survival. IL-15 HSV-TK–transduced T cells expressed HSV-TK and could be efficiently eliminated by ganciclovir. [Copyright &y& Elsevier]

Highlights: [•] We have generated KuO transgenic mouse line by random segregation of provirus method. [•] KuO transgenic mouse line cells carry only one proviral integration site. [•] KuO transgenic mouse line cells stably express KuO in erythrocytes and platelets. [ABSTRACT FROM AUTHOR]

Abstract: Mucopolysaccharidosis (MPS) VII is a lysosomal storage disease due to deficient activity of β-glucuronidase (GUSB), and results in glycosaminoglycan accumulation. Skeletal manifestations include bone dysplasia, degenerative joint disease, and growth retardation. One gene therapy approach for MPS VII involves neonatal intravenous injection of a gamma retroviral vector expressing GUSB, which results in stable expression in liver and secretion of enzyme into blood at levels predicted to be similar or higher to enzyme replacement therapy. The goal of this study was to evaluate the long-term effect of neonatal gene therapy on skeletal manifestations in MPS VII dogs. Treated MPS VII dogs could walk throughout their lives, while untreated MPS VII dogs could not stand beyond 6months and were dead by 2years. Luxation of the coxofemoral joint and the patella, dysplasia of the acetabulum and supracondylar ridge, deep erosions of the distal femur, and synovial hyperplasia were reduced, and the quality of articular bone was improved in treated dogs at 6 to 11years of age compared with untreated MPS VII dogs at 2years or less. However, treated dogs continued to have osteophyte formation, cartilage abnormalities, and an abnormal gait. Enzyme activity was found near synovial blood vessels, and there was 2% as much GUSB activity in synovial fluid as in serum. We conclude that neonatal gene therapy reduces skeletal abnormalities in MPS VII dogs, but clinically-relevant abnormalities remain. Enzyme replacement therapy will probably have similar limitations long-term. [Copyright &y& Elsevier]

Abstract: Adenoviral, retroviral/lentiviral, adeno-associated viral, and herpesviral vectors are the major viral vectors used in gene therapy. Compared with non-viral methods, viruses are highly-evolved, natural delivery agents for genetic materials. Despite their remarkable transduction efficiency, both clinical trials and laboratory experiments have suggested that viral vectors have inherent shortcomings for gene therapy, including limited loading capacity, immunogenicity, genotoxicity, and failure to support long-term adequate transgenic expression. One of the key issues in viral gene therapy is the state of the delivered genetic material in transduced cells. To address genotoxicity and improve the therapeutic transgene expression profile, construction of hybrid vectors have recently been developed. By adding new abilities or replacing certain undesirable elements, novel hybrid viral vectors are expected to outperform their conventional counterparts with improved safety and enhanced therapeutic efficacy. This review provides a comprehensive summary of current achievements in hybrid viral vector development and their impact on the field of gene therapy. [Copyright &y& Elsevier]

The development of transgenic chicken technology has lagged far behind that of mammalian species. Two reasons for this are that only a one-cell-stage oocyte can be obtained from a sacrificed hen and that the yolk prevents high-magnification microscopic observation of oocytes. Recently, several new methods have been developed that will enable the successful establishment of transgenic chickens. Retroviral vectors are used in many cases because of their ability to incorporate transgenes into host cell chromosomes in a highly efficient manner. These viral vectors are injected directly into the embryos, usually at the blastodermal stage. In some cases, primordial germ cells ( PGCs) are infected in vitro and then implanted into recipient embryos. Methods that do not rely on retroviral vectors are also available for creating transgenic chickens. Long-term culture of PGCs permits the selection of stably transfected cells and implantation of the manipulated PGCs. In addition, embryonic stem ( ES) cell systems are available; however, the induction of functional gametes from ES cells has not, to our knowledge, been successful. It is clear that recent developments suggest that chickens may be used as a valuable experimental genetic system. [ABSTRACT FROM AUTHOR]

Background Engineered mesenchymal stromal cells (MSC) have been used in many preclinical studies of gene directed enzyme/prodrug therapy. We aimed to compare the efficacy of two most frequently used systems, as well as evaluate the extent of a bystander effect mediated by therapeutic MSC towards cell lines derived from different tumours. Methods Two approaches were compared: (i) herpes simplex virus thymidine kinase (TK)/ganciclovir (GCV) and (ii) yeast cytosine deaminase fused with uracil phosphoribosyltransferase (CD::UPRT)/5-fluorocytosine (5-FC). The cytotoxic effect mediated by therapeutic MSC was evaluated in direct co-culture by a fluorimetric assay. The expression profile of tumour cells was analyzed by a quantitative polymerase chain reaction, and the ability of gap-junctional intercellular communication (GJIC) was evaluated by a dye transfer assay. Results Both systems were effective only on glioblastoma cells (8-MG-BA). The CD::UPRT-MSC/5-FC system showed efficiency on melanoma A375 cells. We decreased the sensitivity of 8-MG-BA cells and A375 cells to the CD::UPRT-MSC/5-FC system by pharmacological inhibition of thymidylate synthase, and we achieved a similar result in A375 cells by inhibition of thymidine phosphorylase. Although we demonstrated functional GJIC in A375 cells, TK-MSC were ineffective in mediating the bystander effect similarly to HeLa cells, which were also relatively resistant to CD::UPRT-MSC/5-FC treatment. TK-MSC/GCV treatment had a strong cytotoxic effect on MDA-MB-231 cells (breast carcinoma), whereas CD::UPRT-MSC/5-FC treatment failed as a result of overexpression of the gene for ABCC11. Transfection of the MDA-MB-231 cell line with small interference RNA specific to ABCC11 led to a significantly increased sensitivity to the CD::UPRT-MSC/5-FC approach. Conclusions GJIC, expression of enzymes involved in drug metabolism and ABC transporters correlate with the response of tumour cells to treatment by MSC-expressing prodrug-converting genes. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Murine leukemia virus (MLV)-based retroviral vectors is widely used for gene transfer and basic research, and production of high-titer retroviral vectors is very important. Here we report that expression of the Y-box binding protein 1 (YB-1) enhanced the production of infectious MLV vectors. YB-1 specifically increased the stability of viral genomic RNA in virus-producing cells, and thus increasing viral RNA levels in both producer cells and virion particles. The viral element responsive to YB-1 was mapped to the repeat sequence (R region) in MLV genomic RNA. These results identified YB-1 as a MLV mRNA stabilizer, which can be used for improving production of MLV vectors. [ABSTRACT FROM AUTHOR]

Abstract: Gene trapping is a method of inserting DNA into the genome at random, generating insertional mutations throughout the genome. The efficiency of retroviral gene trapping is not sufficient in part because of a strong preference for retroviral integration near transcription start sites. In contrast, lentiviral vectors strongly favor integration in the entire region of highly active genes, suggesting that lentiviral vectors would improve the efficiency of gene trapping. In this study, we constructed both lentiviral and retroviral gene-trap vectors and analyzed integration sites in mouse embryonic stem (ES) cells. The frequency of false-positive gene-trap events was about 12-fold higher for the retroviral vector compared to the lentiviral vector. Within intragenic regions, most of the retroviral vector integration sites were found in the 5′ untranslated region, while the lentiviral vector integrated uniformly throughout transcriptional units. The trapping efficiency of unique genes was significantly higher for the lentiviral vector (∼83%) than for the retroviral vector (∼51%). Our data demonstrate that the lentiviral vector can trap the active genes more efficiently than the retroviral vector and will facilitate efficient generation of gene-trap libraries not only in ES cells but also in a wide variety of cell lines and primary cells. [Copyright &y& Elsevier]

Abstract: Despite recent advances in targeted therapy, renal cell carcinoma (RCC) remains one of the most lethal urologic malignancies. Approximately 30% of patients with localised RCC will develop metastases after curative surgery. Presurgical therapy has been explored for treatment of localised RCC. Endostatin (ES) is a fragment of collagen XVIII that possesses antiangiogenic activity. In this study, we examined the potential use of an antiangiogenic agent as a neoadjuvant therapy in an orthotopic metastatic mouse model of RCC. BALB/c mice bearing Renca cells were treated before nephrectomy with NIH/3T3-LendSN cells. At the end of the experiment, ES serum levels were measured. Primary and metastatic tumour area and microvascular area were determined. In the survival studies, mice were monitored daily until they died. ES serum levels in treated mice were higher in the control group (P <0.05). The median primary tumour area and the mean microvascular area were significantly lower in the ES-treated group compared to control group (P <0.05). The proliferation of Renca cells in the ES-treated group was significantly reduced compared with the control group (P <0.01). ES therapy led to a significant reduction in the number of pulmonary metastatic nodules compared with the control group (P <0.01). Kaplan–Meier survival curves showed that the probability of survival was significantly higher in mice receiving ES therapy (P =0.0243, Log-Rank test). Our results indicated that neoadjuvant ES gene therapy has the potential to decrease tumour burden, extend survival, and may have clinical benefit in the management of RCC. [Copyright &y& Elsevier]