Recombinant Lentiviral Particles Research Articles

Construction and functional activity of a recombinant vector expressing rat glutamic acid decarboxylase 65

Glutamic acid decarboxylase 2 (GAD65) is a gamma-aminobutyric acid (GABA) synthetase. This study aimed to construct a recombinant lentivirus-rGAD65 (rLV-rGAD65) vector containing the cDNA of rat GAD65 (rGAD65) and assess its functional activity in vitro and in vivo. cDNA of rGAD65 was amplified by RT-PCR and subcloned into the LV vector, forming the rLV-GFP-rGAD65 plasmid. The recombinant lentivirus particles (rLV-rGAD65) were packaged by the LV Helper-Free System and the titer was measured. Primary rat lung fibroblasts were transfected with rLV-rGAD65. The expression of rGAD65 in fibroblasts was detected by immunocytochemistry and western blot and the level of GABA in the medium was assessed by high-performance liquid chromatograph (HPLC). In vivo, rLV-rGAD65 was injected into the subthalamic nucleus (STN) of Sprague-Dawley rats using stereotaxic methods, and rGAD65 protein levels in the STN were assessed by immunohistochemistry and Western blot, while the GABA concentration in the substantia nigra pars reticulata (SNr) was assayed by HPLC. The sequence of rGAD65 cDNA was in accord with that in GenBank. The amino-acid sequence of rGAD65 had no mutations and the titer of rLV-rGAD65 reached 6.8 × 10⁸/mL. The efficiency of infection of fibroblasts was 80%, and the concentration of GABA in the medium was (48.14 +/- 9.35) nmol/L. In vivo, rGAD65 expression was detected in the STN, and the concentration of GABA in the SNr increased from (5.95 +/- 1.09) to (12.44 +/- 3.79) nmol/g tissue. The recombinant LV-GFP-rGAD65 vector was successfully constructed. rLV-rGAD65-infected primary fibroblasts in vitro and the expressed rGAD65 catalyzed the formation of GABA from glutamic acid. In vivo, the concentration of GABA in the SNr was increased after rLV-rGAD65 injection into the STN.

Effect of lentivirus-mediated shRNA targeting VEGFR-3 on proliferation, apoptosis and invasion of gastric cancer cells

It has been reported that vascular endothelial growth factor receptor 3 (VEGFR-3) is highly expressed in most tumor tissues, including gastric cancer. However, the effects of VEGFR-3 knockdown on the proliferation, apoptosis and invasion of gastric cancer cells and downstream signaling molecules have not yet been well established. In the present study, four short hairpin RNA (shRNA) sequences targeting the VEGFR-3 gene (NM_002020) were designed and cloned into a lentiviral vector, pRNAT-U6.2/Lenti, to construct four recombinant lentiviral vectors. The vectors with the two highest interfering efficiencies were selected to be co-transfected with packaging vectors in HEK293T cells to assemble lentivirus particles. Results from Western blot analysis showed that the VEGFR-3 shRNA-4 lentivirus-infected group (sh#4) had the highest efficiency of gene silencing in the MKN45 cell line compared with the parental and control group. The sh#4 group significantly slowed cell proliferation, decreased the mean percentage of S-phase cells and increased the mean percentage of G1 phase cells, promoted cell apoptosis, and also significantly inhibited cell invasion of MKN45 compared with the other two groups. Furthermore, the expression of the anti-apoptotic factor Bcl-2 was significantly decreased in the sh#4 group compared to that of the other two groups. Moreover, results from qRT-PCR revealed that knockdown of VEGFR-3 with the shRNA lentiviral vector resulted in down-regulation of the downstream neural cell adhesion molecule contactin-1 (CNTN-1). In conclusion, the recombinant lentivirus particles were able to remarkably suppress VEGFR-3 expression, regulate the cell cycle, inhibit proliferation and induce apoptosis in the MKN45 cell lines.

Deficiency of Biglycan Causes Cardiac Fibroblasts to Differentiate into a Myofibroblast Phenotype

Myocardial infarction (MI) is followed by extracellular matrix (ECM) remodeling, which is on the one hand required for the healing response and the formation of stable scar tissue. However, on the other hand, ECM remodeling can lead to fibrosis and decreased ventricular compliance. The small leucine-rich proteoglycan (SLRP), biglycan (bgn), has been shown to be critically involved in these processes. During post-infarct remodeling cardiac fibroblasts differentiate into myofibroblasts which are the main cell type mediating ECM remodeling. The aim of the present study was to characterize the role of bgn in modulating the phenotype of cardiac fibroblasts. Cardiac fibroblasts were isolated from hearts of wild-type (WT) versus bgn(-/0) mice. Phenotypic characterization of the bgn(-/0) fibroblasts revealed increased proliferation. Importantly, this phenotype of bgn(-/0) fibroblasts was abolished to the WT level by reconstitution of biglycan in the ECM. TGF-β receptor II expression and phosphorylation of SMAD2 were increased. Furthermore, indicative of a myofibroblast phenotype bgn(-/0) fibroblasts were characterized by increased α-smooth muscle actin (α-SMA) incorporated into stress fibers, increased formation of focal adhesions, and increased contraction of collagen gels. Administration of neutralizing antibodies to TGF-β reversed the pro-proliferative, myofibroblastic phenotype. In vivo post-MI α-SMA, TGF-β receptor II expression, and SMAD2 phosphorylation were markedly increased in bgn(-/0) mice. Collectively, the data suggest that bgn deficiency promotes myofibroblast differentiation and proliferation in vitro and in vivo likely due to increased responses to TGF-β and SMAD2 signaling.

Combining bio-electrospraying with gene therapy: a novel biotechnique for the delivery of genetic material via living cells

The investigations reported in this article demonstrate the ability of bio-electrosprays and cell electrospinning to deliver a genetic construct in association with living cells. Previous studies on both bio-electrosprays and cell electrospinning demonstrated great promise for tissue engineering and regenerative biology/medicine. The investigations described herein widen the applicability of these biotechniques by combining gene therapy protocols, resulting in a novel drug delivery methodology previously unexplored. In these studies a human cell line was transduced with recombinant self-inactivating lentiviral particles. These particles incorporated a green fluorescent protein fused to an endosomal targeting construct. This construct encodes a peptide, which can subsequently be detected on the surface of cells by specific T-cells. The transduced cell line was subsequently manipulated in association with either bio-electrospraying or cell electrospinning. Hence this demonstrates (i) the ability to safely handle genetically modified living cells and (ii) the ability to directly form pre-determined architectures bearing living therapeutic cells. This merged technology demonstrates a unique approach for directly forming living therapeutic architectures for controlled and targeted release of experimental cells/genes, as well as medical cell/gene therapeutics for a plethora of biological and medical applications. Hence, such developments could be applied to personalised medicine.

Correction of Fanconi Anemia Group C Hematopoietic Stem Cells Following Intrafemoral Gene Transfer

The main cause of morbidity and mortality in Fanconi anemia patients is the development of bone marrow (BM) failure; thus correction of hematopoietic stem cells (HSCs) through gene transfer approaches would benefit FA patients. However, gene therapy trials for FA patients using ex vivo transduction protocols have failed to provide long-term correction. In addition, ex vivo cultures have been found to be hazardous for FA cells. To circumvent negative effects of ex vivo culture in FA stem cells, we tested the corrective ability of direct injection of recombinant lentiviral particles encoding FancC-EGFP into femurs of FancC −/− mice. Using this approach, we show that FancC −/− HSCs were efficiently corrected. Intrafemoral gene transfer of the FancC gene prevented the mitomycin C-induced BM failure. Moreover, we show that intrafemoral gene delivery into aplastic marrow restored the bone marrow cellularity and corrected the remaining HSCs. These results provide evidence that targeting FA-deficient HSCs directly in their environment enables efficient and long-term correction of BM defects in FA.

Lentivirus-mediated SMO RNA interference inhibits SMO expression and cell proliferation, and affects the cell cycle in LNCaP and PC3 cancer cell lines

Smoothened (SMO) is an important member of the Hedgehog signaling pathway. We constructed a specific recombinant lentiviral vector for RNA interference, targeting the SMO gene (NM_005631) to observe its effect on SMO expression, cell proliferation and the cell cycle in the human androgen-sensitive prostate cancer cell line, LNCaP, and in the androgen-independent prostate cancer cell line, PC3. Four siRNA sequences were designed and inserted into a lentiviral vector pGCSIL-GFP to construct four recombinant vectors. The vector with the highest interfering efficiency was co-transfected with packaging vectors (pHelper1.0 and pHelper2.0) in 293T cells to assemble lentivirus particles by liposome for infecting LNCaP and PC3 cell lines, respectively. The expression level of SMO mRNA, tumor cell proliferation and cell cycle were measured by quantitative realtime polymerase chain reaction (qRT-PCR), 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay and flow cytometry, respectively. Sequence results showed that recombinant lentiviral vectors were constructed successfully. pGCSIL-GFP-723 had the highest interfering efficiency, named Lv-SIL-SMO723 after co-transfection, with which LNCaP and PC3 cell lines were infected. Compared with the control groups, results showed significantly decreased (P < 0.05) SMO mRNA expressions of LNCaP and PC3, lower mean percentage of S-phase cells and higher mean percentage of G(2)/M phase cells, as well as obviously slow proliferation (P < 0.01) of LNCaP in the infected group. Yet, the proliferation of PC3 was not altered (P > 0.05). In conclusion, the recombinant lentivirus particles were able to suppress SMO expression, regulate the cell cycle in the LNCaP and PC3 cell lines and markedly inhibit proliferation of LNCaP cells but not PC3 cells.

434 REPLICATION COMPETENT LENTIVIRUS (RCL) ANALYSIS IN RECIPIENT ANIMALS OF TRANSGENIC EMBRYOS PRODUCED BY LENTIVIRAL TRANSFER

Lentiviral vectors have become a useful tool for gene therapies and the expression of small hairpin (sh)RNAs to target genes both in vitro and in vivo. This is due primarily to their ability to integrate transgenes into both dividing and nondividing cells, as well as the lack of silencing in the germ cell line. However, the retroviral basis for these recombinant, replication-incompetent viruses has prompted investigation into their safety for use in therapeutics and transgenic animal production. Concerns are that recombination with wild-type viruses or endogenous retroviral elements may allow the integrated provirus genome to become replication competent. In order to investigate this, transgenic embryos produced by lentiviral-mediated gene transfer were transferred into recipient animals. The lentiviral plasmids used in this experiment contained a self-inactivating 3′ untranslated region as well as a green fluorescent protein (GFP) reporter gene (Miyoshi et al. 1998 J.Virol. 72, 8150-8157). Recombinant lentivirus was produced through cotransfection of HEK293T cells with the lentiviral transfer plasmid as well as a packaging plasmid and a plasmid encoding the vesicular stomatitis virus glycoprotein (VSV-G), which was used to pseudotype viral particles. Two methods were used for production of transgenic embryos. The first was lentiviral transduction of bovine fetal fibroblasts followed by somatic cell nuclear transfer. The second was incubation of IVP hatched ovine blastocysts in culture medium containing infectious recombinant lentiviral particles. Recipients were then sacrificed and analyzed for the presence of replication competent lentivirus (RCL). Tissues collected from each recipient included blood, lung, lymph node, kidney, liver, mammary gland, ovary, skeletal muscle, spleen, and uterus. In addition, when available, fetal and placental samples were collected. Analyses for RCL included a serum ELISA test for presence of the p24 HIV antigen as well as real-time quantitative PCR (qRT-PCR) on genomic DNA for the presence of VSV-G. To date, a total of 13 recipients including both sheep and cattle have been analyzed. All animals had p24 titers below the level of detection for the assay (&lt;12.5 pg mL-1). Additionally, the tissues mentioned above have been analyzed by qRT-PCR for 6 of the 13 recipients so far, and all have been negative for VSV-G as determined by comparison with positive and negative control samples. Additional collections and analysis are ongoing. A lack of detection of RCL in these animals will build confidence in the use of lentiviral vectors in transgenic animal production and will lend support for their safety in both animal and human therapies.

GATA Transcription Factors Regulate the Expression of the Human Eosinophil-derived Neurotoxin (RNase 2) Gene

The transcription factors GATA-1 and GATA-2 have been implicated in promoting differentiation of eosinophilic leukocytes. In this study, we examined the roles of GATA-1 and GATA-2 in activating transcription of the secretory ribonuclease, the eosinophil-derived neurotoxin (EDN/RNase 2). Augmented expression of both GATA-1 and GATA-2 was detected in eosinophil promyelocyte HL-60 clone 15 cells in response to biochemical differentiation with butyric acid. Deletion or mutation of one or both of the two consensus GATA-binding sites in the extended 1000-bp 5' promoter of the EDN gene resulted in profound reduction in reporter gene activity. Antibody-augmented electrophoretic mobility shift and chromatin immunoprecipitation analyses indicate that GATA-1 and GATA-2 proteins bind to both functional GATA consensus sequences in the EDN promoter. Interestingly, RNA silencing of GATA-1 alone had no impact on EDN expression; silencing of GATA-2 resulted in diminished expression of EDN, and also diminished expression of GATA-1 in both butyric acid-induced HL-60 clone 15 cells and in differentiating human eosinophils derived from CD34(+) hematopoietic progenitors. Likewise, overexpression of GATA-2 in uninduced HL-60 clone 15 cells resulted in augmented transcription of both EDN and GATA-1. Taken together, our data suggest that GATA-2 functions directly via interactions with the EDN promoter and also indirectly, via its ability to regulate the expression of GATA-1 in differentiating eosinophils and eosinophil cell lines.

5 INHIBITION OF FOOT AND MOUTH DISEASE VIRUS IN VITRO USING RNA INTERFERENCE

The use of short-hairpin RNA (shRNA) targeting viral genomes has shown great promise in human medicine and in vitro research in animal agriculture. However, this research has not been extrapolated into livestock applications. Foot and mouth disease virus (FMDV) is a world-wide disease resulting in decreased production and export limitations in countries with endemic FMDV, as well as severe economical impacts if an outbreak occurs in an FMDV-free country. The long-term goal for this project is to produce transgenic cattle that express shRNA targeting the FMDV genome resulting in resistance to infection. As a starting point, five siRNA and one non-targeting control siRNA (Null) were developed targeting different highly conserved regions of a FMDV type-A based replicon. The siRNA were transfected into BHK cells 48 h before viral RNA challenge. Eighteen hours post challenge the cells were lysed and analyzed. Three siRNA targeting the non-structural polymerase protein exhibited severe knockdown of 87, 90, and 92% when compared with the Null siRNA transfected control. The siRNA targeting the VPG3 cap protein reduced activity by 59%, and the siRNA targeting the internal ribosomal entry site had a minimal effect of 15% reduction. Based upon these results, we produced recombinant lentiviral particles designed to deliver the shRNA sequence targeting the FMDV genome and the fluorescent marker, dsRed, into a bovine fetal fibroblast cell line. This transgenic cell line expressing the most effective shRNA (based on initial siRNA screening) was used for somatic cell nuclear transfer to create bovine embryos. One hundred and sixty oocytes were enucleated, of which 149 had successful fusion resulting in 35 blastocysts after in vitro culture. Two embryos per recipient were transferred into five recipients. At Day 40 of pregnancy three of the five recipients had a fetus, but no heart beat could be detected. We are currently in the process of creating another cell line and repeating this experiment. If successful, transgenic calves will be visually and genetically analyzed for expression of dsRed and shRNA targeting FMDV. Transgenic and control animals/tissues will then be analyzed for resistance to infection with FMDV.

Construction and identification of recombinant lentivirus-mediated gene transfer system for rat transducer of regulated CREB activity 1

Objective To construct a recombinant lentivirus vector which carries SD rat transducer of regulated CREB activity-1(TORC1) gene and examine its ability to express the TORC1 gene in vitro. Methods The coding sequence of SD rat TORC1 gene was amplified using PCR and cloned into pGC-FU vector. 293T cells were transfected using Lipofectamine 2000 and packaged for the recombinant lentivirus particles. When the cloned sequence was identified to be right, the recombinant lentivirus particles were amplified in a large quantity. The titer of virus was determined by real-time PCR and the level of TORC1 expression was examined by Western blot. Results The recombinant lentivirus vector carrying TORC1 was constructed successfully and could express TORC1 at a high level in 293T cells in vitro, and the titer determined by real-time PCR was 2 × 10 8 TU/ml. Conclusion The recombinant lentivirus vector could express TORC1 gene at a high level, and was very helpful in the study of exploring the effect of TORC1 on spinal cord injury.

Restricted transgene persistence after lentiviral vector‐mediated fetal gene transfer in the pregnant rabbit model

Prenatal gene transfer may enable early causal intervention for the treatment or prevention of many devastating diseases. Nevertheless, permanent correction of most inherited disorders requires a sustained level of expression from the therapeutic transgene, which could theoretically be achieved with integrating vectors. Rabbit fetuses received 8.5 x 10(6) HIV-based recombinant lentivirus particles containing the enhanced green fluorescent protein (EGFP) transgene by intrahepatic, intra-amniotic or intraperitoneal injection at 22 days of gestation. Provirus presence and transgene expression in rabbit tissues were evaluated at both 1.5 and 16 weeks post-in utero intervention by polymerase chain reaction (PCR) and reverse transcriptase-PCR, respectively. Moreover, we assessed persistence of EGFP by immunohistochemistry. Enzyme-linked immunosorbent assays confirmed the development of antibodies specific against both the viral vector and the reporter protein. Regardless of the route of administration employed, lentiviral vector-based in utero gene transfer was safe and reached 85% of the intervened fetuses at birth. However, the integrated provirus frequency was significantly reduced to 50% of that in young rabbits at 16 weeks post-treatment. In these animals, EGFP expression was evident in many tissues, including cytokeratin 5-rich basal cells from stratified and pseudostratified epithelia, suggesting that the lentiviral vector might have reached progenitor cells. Conversely, we identified the presence of immune-inflammatory infiltrates in several EGFP-expressing tissues. Moreover, almost 70% of the lentiviral vector-treated rabbits elicited a humoral immune response against the viral envelope and/or the EGFP. At two-thirds gestational age, the adaptive immune system of the rabbit appears a relevant factor limiting transgene persistence and expression following lentiviral vector-mediated in utero gene transfer.

A High Affinity Hepatocyte Growth Factor-binding Site in the Immunoglobulin-like Region of Met

Hepatocyte growth factor (HGF) and its high affinity receptor, the tyrosine kinase Met, play a key role in embryo development and tumor invasion. Both HGF and Met are established targets for cancer therapy. However, the mechanism of their interaction is complex and remains elusive. HGF is secreted as a monomeric precursor (pro-HGF) that binds to but does not activate Met. Mature HGF is a α/β heterodimer containing a high affinity Met-binding site in the α-chain (HGF-α) and a low affinity Met-binding site in the β-chain (HGF-β). The extracellular portion of Met contains a semaphorin (Sema) domain, a cysteine-rich hinge (plexin-semaphorin-integrin), and four immunoglobulin-like domains (immunoglobulin-like regions in plexins and transcription factors (IPT) 1-4). HGF-β binds to Sema through a low affinity contact. The domain of Met responsible for high affinity binding to HGF-α has not been identified yet. Here we show that this long sought after binding site lies in the immunoglobulin-like region of Met and more precisely in IPT 3 and 4. We also show that IPT 3 and 4 are sufficient to transmit the signal for kinase activation to the cytoplasm, although the lack of Sema makes the receptor equally sensitive to mature HGF and pro-HGF. Finally, we provide evidence that soluble Met-derived proteins containing either the low affinity or high affinity HGF-binding site antagonize HGF-induced invasive growth both in vitro and in xenografts. These data suggest that the immunoglobulin-like region of Met cooperates with the Sema domain in binding to HGF and in controlling Met kinase activity. Although the IPT-HGF-α interaction provides binding strength, the Sema-HGF-β contact confers selective sensitivity to the active form of the ligand.