Regulated expression of the interferon-β gene in mice

Externally-Controlled Systems for Immunotherapy: From Bench to Bedside

Immunotherapy is a very promising therapeutic approach against cancer that is particularly effective when combined with gene therapy. Immuno-gene therapy approaches have led to the approval of four advanced therapy medicinal products (ATMPs) for the treatment of p53-deficient tumors (Gendicine and Imlygic), refractory acute lymphoblastic leukemia (Kymriah) and large B-cell lymphomas (Yescarta). In spite of these remarkable successes, immunotherapy is still associated with severe side effects for CD19+ malignancies and is inefficient for solid tumors. Controlling transgene expression through an externally administered inductor is envisioned as a potent strategy to improve safety and efficacy of immunotherapy. The aim is to develop smart immunogene therapy-based-ATMPs, which can be controlled by the addition of innocuous drugs or agents, allowing the clinicians to manage the intensity and durability of the therapy. In the present manuscript, we will review the different inducible, versatile and externally controlled gene delivery systems that have been developed and their applications to the field of immunotherapy. We will highlight the advantages and disadvantages of each system and their potential applications in clinics.

Generating DNA Expression Cassettes Encoding Multimeric Artificial MicroRNA Precursors

RNA interference (RNAi) is a promising tool for the treatment of chronic viral infection, such as that caused by the hepatitis B virus (HBV). RNAi activators, including expressed primary microRNA (pri-miRNA) mimics, can effectively silence viral gene expression and thereby inhibit viral replication. Here we describe a protocol for the design, generation and functional assessment of cassettes encoding effective single and multimeric pri-miRNA mimics. Artificial miRNAs targeting viral genes can be identified in silico and used to design corresponding pri-miRNA mimics. A two-step generation and TA cloning protocol can be used to produce single mimics, while the strategic use of restriction sites enables concatenation of mimics in a sub-cloning protocol. Basic gene silencing function of pri-miRNA mimics in cell culture can then be assessed using a dual luciferase assay and appropriate minimal targets. The methods described here for the generation of effective pri-miRNA mimics targeting HBV can be applied in the silencing of other viral or endogenous genes.

In-Depth Characterization of a Mifepristone-Regulated Expression System for AAV5-Mediated Gene Therapy in the Liver

Gene therapy is being developed for the treatment of inherited diseases, whereby a therapeutic gene is continuously expressed in patients after delivery via viral vectors such as adeno-associated virus (AAV). Depending on the transgene, there could be a limited therapeutic window, and regulating timing and levels of transgene expression is advantageous. To control transgene transcription, the regulatory system GeneSwitch (GS) was evaluated in detail both in vitro and in vivo. The classical two-plasmid mifepristone (MFP)-inducible GS system was put into one plasmid or a single AAV5 vector. Our data demonstrate the inducibility of multiple transgenes and the importance of promoter and regulatory elements within the GS system. Mice injected with AAV5 containing the GS system transiently expressed mRNA and protein after MFP induction. The inducer MFP could be measured in plasma and liver tissue, and assessment of MFP and its metabolites showed rapid clearance from murine plasma. In a head-to-head comparison, our single vector outclassed the classical two-vector GS system. Finally, we show repeated inducibility of the transgene that also translated into a dynamic phenotypic change in mice. Taken together, this in-depth analysis of the GS system shows its applicability for regulated gene therapy.

Amelioration of Experimental Autoimmune Encephalomyelitis in Mice by Interferon-Beta Gene Therapy, Using a Long-Term Expression Plasmid Vector

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. Repeated injections of the interferon-β (IFN-β) protein are required for relapse prevention therapy in patients with MS. IFN-β gene transfer can be an alternative treatment that continuously supplies IFN-β protein to the patient without requiring repeated injections. In a previous study, we constructed a novel long-term IFN-β-expressing plasmid vector (pMx-IFN-β). In the present study, we examined whether gene transfer of pMx-IFN-β could be effective for the treatment of MS in experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. Seven days after injection of the EAE-inducing peptide, the EAE mice received hydrodynamic injections pMx-IFN-β. The severity of EAE symptoms in the pMx-IFN-β-treated mice was significantly lower for 1 month than that observed in the untreated mice. An evaluation of blood-brain barrier (BBB) function, using Evans Blue, showed that injection of pMx-IFN-β suppressed the BBB disruptions normally observed in EAE mice, while BBB disruptions remained evident in the untreated EAE mice. Histological analysis showed fewer invasive inflammatory cells in the spinal cords of the pMx-IFN-β-treated mice than in the spinal cords of the other mice. Serum interferon gamma protein (IFN-γ) concentrations in the pMx-IFN-β-treated mice were significantly lower than that in the untreated mice, indicating that IFN-β gene transfer suppressed the production of IFN-γ from pathogenic T cells. These results indicate that IFN-β transgene expression by single administration of the pMx-IFN-β can be an effective long-term treatment for MS.

Induction of interleukin 2 expression in the liver for the treatment of H22 hepatoma in mice

BACKGROUND AND AIMS

We designed this study to evaluate the ability of a plasmid carrying an RU486 regulatory system to induce expression of interleukin-2 (IL-2) gene and to examine the antitumour efficacy of the induced IL-2 gene.

METHODS

The plasmid pRS-mIL-2,which contains an RU486 inducible system and IL-2 gene was injected into mice. Sera and tissues from liver, spleen, lungs and kidneys were taken to test the properties of the plasmid. To examine the antitumour efficacy of pRS-mIL-2, tumours were established in the liver by direct inoculation of H22 hepatoma cells.

RESULTS

The IL-2 levels in serum correlated with the dose of plasmid and RU486. High and sustained IL-2 levels could be achieved by administration of RU486 every day. The mRNA of transgene IL-2 was found only in the liver. Treatment of mice with pRS-mIL-2 plus RU486 resulted in the significant reduction in tumour volume compared with control groups.

CONCLUSIONS

Tight temporal and spatial control of transgene IL-2 expression can be achieved by a plasmid containing an RU486 inducible system driven by liver specific promoter. pRS-mIL-2 exhibited strong antitumour efficacy following consecutive induction with RU486.

Inhibition of fatty-acid amide hydrolase and CB1 receptor antagonism differentially affect behavioural responses in normal and PCP-treated rats

The 'cannabinoid hypothesis' of schizophrenia tulates that over-activity of the endocannabinoid system might contribute to the aetiology of schizophrenia. In keeping with this hypothesis, increased expression of CB1 receptors, elevation of the endocannabinoid anandamide (AEA) and cannabinoid-induced cognitive changes have been reported in animal models of schizophrenia and psychotic patients. In this study we measured brain endocannabinoid levels and [35S]GTPgammaS binding stimulated by the CB receptor agonist CP55,940 in rats undergoing withdrawal from subchronic administration of phencyclidine (PCP), a well-established pharmacological model of schizophrenia. We also investigated whether systemic application of the fatty-acid amide hydrolase (FAAH) inhibitor URB597 or CB1 receptor blockade by AM251 affected the following PCP-induced behavioural deficits reminiscent of schizophrenia-like symptoms: (1) working-memory impairment (cognitive deficit), (2) social withdrawal (negative symptom), and (3) hyperactivity in response to d-amphetamine challenge (positive symptoms). PCP-treated rats showed increased endocannabinoid levels in the nucleus accumbens and ventral tegmental area, whereas CB1 receptor expression and CP55,940-stimulated [35S]GTPgammaS binding were unaltered. URB597 reversed the PCP-induced social withdrawal but caused social withdrawal and working-memory deficits in saline-treated rats that were comparable to those observed after PCP treatment. Administration of AM251 ameliorated the working-memory deficit in PCP-treated rats, but impaired working memory in saline-injected controls. Taken together, these results suggest that FAAH inhibition may improve negative symptoms in PCP-treated rats but produce deleterious effects in untreated animals, possibly by disturbing endocannabinoid tone. A similar pattern (beneficial for schizophrenia-related cognitive deficits, but detrimental under normal conditions) accompanies CB1 receptor blockade.

Development and validation of an improved inducer-regulator protein complex in the pBRES-regulated expression system

Widespread adaptation of small molecule-regulated expression systems requires the development of selective inducer molecules that do not have any significant side effects on the endogenous receptors from which the regulated expression system is derived. Here we report the identification and in vitro validation of a novel inducer-receptor pair for the single-plasmid regulated expression system termed pBRES, which contains the ligand-binding domain from the human progesterone receptor (hPR). A small molecule inducer, BLX-913, has been identified as having a 30-fold lower IC(50) for the human progesterone receptor than mifepristone (MFP), the previously best characterized inducer for pBRES. Using modeling-guided protein engineering, compensatory mutations were installed at positions W755 and V729 (hPR numbering) in the ligand-binding pocket of the pBRES regulator protein (pBRES RP) to accommodate the new inducer and allow induction of transgene expression to levels previously seen with MFP. The improved inducer-pBRES RP complex was validated in vitro by monitoring the induction of luciferase, murine secreted alkaline phosphatase, and human interferon beta transgenes in mouse skeletal muscle cells. The engineered pBRES demonstrated low levels of transgene expression in the absence, and high expression levels in the presence, of the new BLX-913 inducer. Findings presented here allow induction of the pBRES-regulated gene expression system by a compound with markedly lower anti-hPR activity than MFP, the previously best characterized inducer.