Development of a liver-specific Tet-on inducible system for AAV vectors and its application in the treatment of liver cancer.
ABSTRACT: Recombinant adeno-associated virus (rAAV) are effective gene delivery vehicles that can mediate long-lasting transgene expression. However, tight regulation and tissue-specific transgene expression is required for certain therapeutic applications. For regulatable expression from the liver we designed a hepatospecific bidirectional and autoregulatory tetracycline (Tet)-On system (Tet(bidir)Alb) flanked by AAV inverted terminal repeats (ITRs). We characterized the inducible hepatospecific system in comparison with an inducible ubiquitous expression system (Tet(bidir)CMV) using luciferase (luc). Although the ubiquitous system led to luc expression throughout the mouse, luc expression derived from the hepatospecific system was restricted to the liver. Interestingly, the induction rate of the Tet(bidir)Alb was significantly higher than that of Tet(bidir)CMV, whereas leakage of Tet(bidir)Alb was significantly lower. To evaluate the therapeutic potential of this vector, an AAV-Tet(bidir)-Alb-expressing interleukin-12 (IL-12) was tested in a murine model for hepatic colorectal metastasis. The vector induced dose-dependent levels of IL-12 and interferon-? (IFN-?), showing no significant toxicity. AAV-Tet(bidir)-Alb-IL-12 was highly efficient in preventing establishment of metastasis in the liver and induced an efficient T-cell memory response to tumor cells. Thus, we have demonstrated persistent, and inducible in vivo expression of a gene from a liver-specific Tet-On inducible construct delivered via an AAV vector and proved to be an efficient tool for treating liver cancer.
Project description:BACKGROUND:Diabetes mellitus is caused by a partial or complete lack of insulin production in the body. We have previously shown that a single injection of an adeno-associated virus serotype 8 (AAV8) vector carrying a modified and codon optimized human insulin gene induced hepatic production of insulin and corrected streptozotocin (STZ)-induced diabetes in mice for more than 1 year. Insulin production was constitutive, analogous to long-acting insulin therapy. METHODS:We have developed a single AAV8 vector with a Tet-Off regulatable system as a safety mechanism to turn off insulin secretion should hypoglycaemia develop in vector-treated diabetic mice. We first transfected HepG2 cells or freshly isolated rat hepatocytes in vitro with the Tet-Off system (pAAV-Tetoffbidir -Alb-luc) regulating a luciferase reporter gene. We subsequently incorporated a furin-cleavable codon-optimised human proinsulin cDNA into pAAV-Tetoffbidir backbone to form the doxycycline inducible pAAV-Tetoffbidir -Alb-hINSco. RESULTS:Using STZ-induced diabetic mice, we were able to switch off insulin secretion repeatedly with doxycycline administration, and showed full restoration of insulin secretion on withdrawing doxycycline. CONCLUSIONS:The present study provides proof of concept that, under circumstances when inappropriate basal insulin secretion is a safety concern, insulin secretion from AAV8 gene therapy can be turned off reversibly with doxycycline.
Project description:To investigate the relationship between over-expression of urokinase plasminogen activator (uPA) and hepatitis B virus (HBV) related liver diseases in a transgenic mouse model.Albumin-tetracycline reverse transcriptional activator and tetO-uPA transgenic mice were generated respectively through pronuclear injection and crossed to produce the double transgenic in-alb-uPA mice, for which doxycycline (Dox)-inducible and liver-specific over-expression of uPA can be achieved. Hydrodynamic transfection of plasmid adeno-associated virus (AAV)-1.3 HBV was performed through the tail veins of the Dox-induced in-alb-uPA mice. Expression of uPA and HBV antigens were analyzed through double-staining immunohistochemical assay. Cytokine production was detected by enzyme linked immunosorbent assay and ?-fetoprotein (AFP) mRNA level was evaluated through real-time quantitative polymerase chain reaction.Plasmid AAV-1.3 HBV hydrodynamic transfection in Dox-induced transgenic mice not only resulted in severe liver injury with hepatocarcinoma-like histological changes and hepatic AFP production, but also showed an increased serum level of HBV antigens and cytokines like interleukin-6 and tumor necrosis factor-?, compared with the control group.Over-expression of uPA plays a synergistic role in the development of liver injury, inflammation and regeneration during acute HBV infection.
Project description:Hepatospecific deletion of PTEN results in constitutive activation of Akt and increased lipogenesis. In mice, the addition of a high fat diet (HFD) downregulates lipogenesis. The aim of this study was to determine the effects of a HFD on hepatocellular damage induced by deletion of PTEN.12 Week old male flox/flox hepatospecific PTEN mice (PTENf/f) or Alb-Cre controls were fed a HFD composed of 45% fat-derived calories (from corn oil) or a normal chow. Animals were then analyzed for hepatocellular damage, oxidative stress and expression of enzymes involved in fatty acid metabolism.In the Alb-Cre animals, the addition of a HFD resulted in a significant increase in liver triglycerides and altered REDOX capacity as evidenced by increased GPX activity, decreased GST activity and decreased hepatic concentrations of GSSG. In addition, SCD2, ACLY and FASN were all downregulated by the addition of HFD. Furthermore, expression of PPAR? and PPAR?-dependent proteins Cyp4a and ACSL1 were upregulated. In the PTENf/f mice, HFD resulted in significant increased in ALT, serum triglycerides and decreased REDOX capacity. Although expression of fatty acid synthetic enzymes was elevated in the chow fed PTENf/f group, the addition of HFD resulted in SCD2, ACLY and FASN downregulation. Compared to the Alb-Cre HFD group, expression of PGC1?, PPAR? and its downstream targets ACSL and Cyp4a were upregulated in PTENf/f mice.These data suggest that during conditions of constitutive Akt activation and increased steatosis, the addition of a HFD enhances hepatocellular damage due to increased CD36 expression and altered REDOX status. In addition, this work indicates HFD-induced hepatocellular damage occurs in part, independently of Akt signaling.
Project description:Hemophilia A is a monogenic disease with a blood clotting factor VIII (FVIII) deficiency caused by mutation in the factor VIII (F8) gene. Current and emerging treatments such as FVIII protein injection and gene therapies via AAV-delivered F8 transgene in an episome are costly and nonpermanent. Here, we describe a CRISPR/Cas9-based in vivo genome editing method, combined with non-homologous end joining, enabling permanent chromosomal integration of a modified human B domain deleted-F8 (BDD-F8) at the albumin (Alb) locus in liver cells. To test the approach in mice, C57BL/6 mice received tail vein injections of two vectors, AAV8-SaCas9-gRNA, targeting Alb intron 13, and AAV8-BDD-F8. This resulted in BDD-F8 insertion at the Alb locus and FVIII protein expression in the liver of vector-, but not vehicle-, treated mice. Using this approach in hemophilic mice, BDD-F8 was expressed in liver cells as functional human FVIII, leading to increased plasma levels of FVIII and restoration of blood clotting properties in a dose-dependent manor for at least 7 months, with no detectable liver toxicity or meaningful off-target effects. Based on these findings, our BDD-F8 genome editing approach may offer an efficacious, long-term and safe treatment for patients with hemophilia A.
Project description:Previous studies showed that low-density lipoprotein receptor (LDLR) mRNA 3' untranslated region (UTR) contains regulatory elements responsible for rapid mRNA turnover in hepatic cells and mediates the mRNA stabilization induced by berberine (BBR). Here, we elucidate the underlying mechanism of BBR's action by characterizing mRNA-binding proteins that modulate LDLR mRNA decay via 3'UTR in liver tissue in vivo.We generated a transgenic mouse model (Alb-Luc-UTR) that expresses Luc-LDLR3'UTR reporter gene driven by the albumin promoter to study 3'UTR function in mediating LDLR mRNA decay in liver tissue. We show that treating Alb-Luc-UTR mice with BBR led to significant increases in hepatic bioluminescence signals, Luc-UTR mRNA, and LDLR mRNA levels as compared with control mice. These effects were accompanied by specific reductions of mRNA decay-promoting factor heterogeneous nuclear ribonucleoprotein D (hnRNP D) in liver of BBR-treated mice. Knockdown and overexpression studies further demonstrated that hnRNP D p37 isoform plays a major role in promoting hepatic LDLR mRNA degradation. In addition, we examined LDLR mRNA half-life, Luc-UTR reporter activity, and hnRNP D expression levels in cell lines derived from extrahepatic tissues. We demonstrated that strengths of 3'UTR in promoting mRNA degradation correlate with hnRNP D cellular abundances in nonhepatic cell lines, thereby suggesting its involvement in LDLR mRNA degradation beyond liver tissue.hnRNP D is critically involved in LDLR mRNA degradation in liver tissue in vivo. The inverse relationship of hnRNP D abundance with LDLR mRNA levels after BBR treatment suggests the potential of hnRNP D of being a novel therapeutic target for LDL cholesterol lowering.
Project description:The obligate intracellular bacterium Chlamydia psittaci is a known avian pathogen causing psittacosis in birds and is capable of zoonotic transmission. In human pulmonary infections, C. psittaci can cause pneumonia associated with significant mortality if inadequately diagnosed and treated. Although intracellular C. psittaci manipulates host cell organelles for its replication and survival, it has been difficult to demonstrate host-pathogen interactions in C. psittaci infection due to the lack of easy-to-handle genetic manipulation tools. Here, we show the genetic transformation of C. psittaci using a plasmid shuttle vector that contains a controllable gene induction system. The 7,553-bp plasmid p01DC12 was prepared from the nonavian C. psittaci strain 01DC12. We constructed the shuttle vector pCps-Tet-mCherry using the full sequence of p01DC12 and the 4,449-bp fragment of Chlamydia trachomatis shuttle vector pBOMB4-Tet-mCherry. pCps-Tet-mCherry includes genes encoding the green fluorescent protein (GFP), mCherry, and ampicillin resistance (AmpR). Target genes can be inserted at a multiple cloning site (MCS). Importantly, these genes can be regulated by a tetracycline-inducible (tet) promoter. Using the pCps-Tet-mCherry plasmid shuttle vector, we show the expression of GFP, as well as the induction of mCherry expression, in C. psittaci strain 02DC15, which belongs to the avian C. psittaci 6BC clade. Furthermore, we demonstrated that pCps-Tet-mCherry was stably retained in C. psittaci transformants. Thus, our C. psittaci plasmid shuttle vector system represents a novel targeted approach that enables the elucidation of host-pathogen interactions.IMPORTANCE Psittacosis, caused by avian C. psittaci, has a major economic impact in the poultry industry worldwide and represents a significant risk for zoonotic transmission to humans. In the past decade, the tools of genetic manipulation have been improved for chlamydial molecular studies. While several genetic tools have been mainly developed in Chlamydia trachomatis, a stable gene-inducible shuttle vector system has not to date been available for C. psittaci In this study, we adapted a C. trachomatis plasmid shuttle vector system to C. psittaci We constructed a C. psittaci plasmid backbone shuttle vector called pCps-Tet-mCherry. The construct expresses GFP in C. psittaci Importantly, exogeneous genes can be inserted at an MCS and are regulated by a tet promoter. The application of the pCps-Tet-mCherry shuttle vector system enables a promising new approach to investigate unknown gene functions of this pathogen.
Project description:To establish an inducible liver injury mouse model and transplant human hepatocytes to obtain liver-humanized mice.We crossed three mouse strains, including albumin (Alb)-cre transgenic mice, inducible diphtheria toxin receptor (DTR) transgenic mice and severe combined immune deficient (SCID)-beige mice, to create Alb-cre/DTR/SCID-beige (ADSB) mice, which coincidentally harbor Alb-cre and DTR transgenes and are immunodeficient. As the Cre expression is driven by the liver-specific promoter Alb (encoding ALB), the DTR stop signal flanked by two loxP sites can be deleted in the ADSB mice, resulting in DTR expression in the liver. ADSB mice aged 8-10 wk were injected intraperitoneally (i.p.) with diphtheria toxin (DT) and liver damage was assessed by serum alanine aminotransferase (ALT) level. Two days later, mouse livers were sampled for histological analysis, and human hepatocytes were transplanted into the livers on the same day. A human ALB enzyme-linked immunosorbent assay was performed 7, 14, 21 and 28 d after transplantation. Human CD68 immunohistochemistry was performed 30 and 90 d after transplantation.We crossed Alb-cre with DTR and SCID-beige mice to obtain ADSB mice. These mice were found to have liver damage 4 d after i.p. injection of 2.5 ng/g bodyweight DT. Bodyweight began to decrease on day 2, increased on day 7, and was lowest on day 4 (range, 10.5%-13.4%). Serum ALT activity began to increase on day 2 and reached a peak value of 289.7 ± 16.2 IU/mL on day 4, then returned to background values on day 7. After transplantation of human liver cells, peripheral blood human ALB level was 1580 ± 454.8 ng/mL (range, 750.2-3064.9 ng/mL) after 28 d and Kupffer cells were present in the liver at 30 d in ADSB mice.Human hepatocytes were successfully repopulated in the livers of ADSB mice. The inducible mouse model of humanized liver in ADSB mice may have functional applications, such as hepatocyte transplantation, hepatic regeneration and drug metabolism.
Project description:Visualization of neurons is indispensable for the investigation of neuronal circuits in the central nervous system. Virus vectors have been widely used for labeling particular subsets of neurons, and the adeno-associated virus (AAV) vector has gained popularity as a tool for gene transfer. Here, we developed a single AAV vector Tet-Off platform, AAV-SynTetOff, to improve the gene-transduction efficiency, specifically in neurons. The platform is composed of regulator and response elements in a single AAV genome. After infection of Neuro-2a cells with the AAV-SynTetOff vector, the transduction efficiency of green fluorescent protein (GFP) was increased by approximately 2- and 15-fold relative to the conventional AAV vector with the human cytomegalovirus (CMV) or human synapsin I (SYN) promoter, respectively. We then injected the AAV vectors into the mouse neostriatum. GFP expression in the neostriatal neurons infected with the AAV-SynTetOff vector was approximately 40-times higher than that with the CMV or SYN promoter. By adding a membrane-targeting signal to GFP, the axon fibers of neostriatal neurons were clearly visualized. In contrast, by attaching somatodendritic membrane-targeting signals to GFP, axon fiber labeling was mostly suppressed. Furthermore, we prepared the AAV-SynTetOff vector, which simultaneously expressed somatodendritic membrane-targeted GFP and membrane-targeted red fluorescent protein (RFP). After injection of the vector into the neostriatum, the cell bodies and dendrites of neostriatal neurons were labeled with both GFP and RFP, whereas the axons in the projection sites were labeled only with RFP. Finally, we applied this vector to vasoactive intestinal polypeptide-positive (VIP+) neocortical neurons, one of the subclasses of inhibitory neurons in the neocortex, in layer 2/3 of the mouse primary somatosensory cortex. The results revealed the differential distribution of the somatodendritic and axonal structures at the population level. The AAV-SynTetOff vector developed in the present study exhibits strong fluorescence labeling and has promising applications in neuronal imaging.
Project description:Studying hepatitis delta virus (HDV) and developing new treatments is hampered by the absence limited availability of small animal models. Here a description of a robust mouse model of HDV infection that mimics several important characteristics of the human disease is presented. HDV- and HBV-replication competent genomes were delivered to the mouse liver using adeno-associated viruses (AAV) (AAV-HDV and AAV-HBV). Viral load, antigen expression and genomes were quantified at different time points after AAV injection. Furthermore, liver pathology, genome editing, and the activation of the innate immune response were evaluated. AAV-HDV infection initiated HDV replication in mouse hepatocytes. Genome-editing was confirmed by the presence of small and large-HDV-antigens and sequencing. Viral replication was detected for 45 days, even after the AAV-HDV vector had almost disappeared. In the presence of HBV, HDV infectious particles were detected in serum. Furthermore, as observed in patients, co-infection was associated with the reduction of HBV antigen expression and the onset of liver damage that included the up/down-regulation of genes involved in the development of liver pathologies. HDV replication induced a sustained type-I IFN response, which was significantly reduced in immunodeficient mice and almost absent in MAVS-deficient mice. The animal model described here reproduces important characteristics of human HDV infection and provides a valuable tool for characterizing the viral infection and for developing new treatments. Furthermore, MAVS was identified as a main player in HDV detection and adaptive immunity was found to be involved in the amplification of the innate immune response. Overall design: C57BL/6 mice received an injection of AAV-HDV, or AAV-HBV , or AAV-HBV+AAV-HDV o AAV-luc 21 days animals were sacrificed, liver isolated and RNA purified. Gene expression analysis if the first three groups was compared with the AAV-luc-terated group.
Project description:Stringently controlled conditional expressing systems are crucial for the functional characterization of genes. Currently, screening of multiple clones to identify the tightly controlled ones is necessary but time-consuming. Here, we describe a system fusing Tet (tetracycline)-inducible elements, BAC (bacterial artificial chromosome) and Gateway technology together to allow tight control of gene expression in BAC-transfected eukaryotic bulk cell cultures. Recombinase cloning into the shuttle vector and the BAC facilitates vector construction. An EGFP (enhanced green fluorescent protein) allows FACS (fluorescence activated cell sorting) and the BAC technology ensures tight control of gene expression that is independent of the integrating site. In the current first application, our gene of interest encodes a beta-catenin-ERalpha fusion protein. Tested by luciferase assay and western blotting, in HTB56 lung cancer cells the final BAC E11-IGR-beta-catenin-ERalpha vector demonstrated sensitive inducibility by Tet or Dox (doxycycline) in a dose-dependent manner with low background, and the EGFP was an effective selection marker by FACS in bulk culture HTB56 and myeloblastic 32D cells. This is a highly efficient tool for the rapid generation of stringently controlled Tet-inducible systems in cell lines.