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Smith T, Singh P, Chmielewski KO, Bloom K, Cathomen T, Arbuthnot P, Ely A. Improved Specificity and Safety of Anti-Hepatitis B Virus TALENs Using Obligate Heterodimeric FokI Nuclease Domains. Viruses 2021; 13:v13071344. [PMID: 34372550 PMCID: PMC8310341 DOI: 10.3390/v13071344] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 07/02/2021] [Indexed: 01/04/2023] Open
Abstract
Persistent hepatitis B virus (HBV) infection remains a serious medical problem worldwide, with an estimated global burden of 257 million carriers. Prophylactic and therapeutic interventions, in the form of a vaccine, immunomodulators, and nucleotide and nucleoside analogs, are available. Vaccination, however, offers no therapeutic benefit to chronic sufferers and has had a limited impact on infection rates. Although immunomodulators and nucleotide and nucleoside analogs have been licensed for treatment of chronic HBV, cure rates remain low. Transcription activator-like effector nucleases (TALENs) designed to bind and cleave viral DNA offer a novel therapeutic approach. Importantly, TALENs can target covalently closed circular DNA (cccDNA) directly with the potential of permanently disabling this important viral replicative intermediate. Potential off-target cleavage by engineered nucleases leading to toxicity presents a limitation of this technology. To address this, in the context of HBV gene therapy, existing TALENs targeting the viral core and surface open reading frames were modified with second- and third-generation FokI nuclease domains. As obligate heterodimers these TALENs prevent target cleavage as a result of FokI homodimerization. Second-generation obligate heterodimeric TALENs were as effective at silencing viral gene expression as first-generation counterparts and demonstrated an improved specificity in a mouse model of HBV replication.
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Affiliation(s)
- Tiffany Smith
- Wits/SAMRC Antiviral Gene Therapy Research Unit, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa; (T.S.); (P.S.); (K.B.); (P.A.)
| | - Prashika Singh
- Wits/SAMRC Antiviral Gene Therapy Research Unit, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa; (T.S.); (P.S.); (K.B.); (P.A.)
| | - Kay Ole Chmielewski
- Institute for Transfusion Medicine and Gene Therapy, Medical Center-University of Freiburg & Medical Faculty, University of Freiburg, 79106 Freiburg, Germany; (K.O.C.); (T.C.)
| | - Kristie Bloom
- Wits/SAMRC Antiviral Gene Therapy Research Unit, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa; (T.S.); (P.S.); (K.B.); (P.A.)
| | - Toni Cathomen
- Institute for Transfusion Medicine and Gene Therapy, Medical Center-University of Freiburg & Medical Faculty, University of Freiburg, 79106 Freiburg, Germany; (K.O.C.); (T.C.)
| | - Patrick Arbuthnot
- Wits/SAMRC Antiviral Gene Therapy Research Unit, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa; (T.S.); (P.S.); (K.B.); (P.A.)
| | - Abdullah Ely
- Wits/SAMRC Antiviral Gene Therapy Research Unit, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa; (T.S.); (P.S.); (K.B.); (P.A.)
- Correspondence: ; Tel.: +27-(0)11-717-2561
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van den Berg FT, Ely A, Arbuthnot P. Generating DNA Expression Cassettes Encoding Multimeric Artificial MicroRNA Precursors. Methods Mol Biol 2020; 2115:185-197. [PMID: 32006402 DOI: 10.1007/978-1-0716-0290-4_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
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.
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Affiliation(s)
- Fiona T van den Berg
- Wits-SAMRC Antiviral Gene Therapy Research Unit, Department of Molecular Medicine & Haematology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Abdullah Ely
- Wits-SAMRC Antiviral Gene Therapy Research Unit, Department of Molecular Medicine & Haematology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Patrick Arbuthnot
- Wits-SAMRC Antiviral Gene Therapy Research Unit, Department of Molecular Medicine & Haematology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
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3
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Bloom K, Kaldine H, Cathomen T, Mussolino C, Ely A, Arbuthnot P. Inhibition of replication of hepatitis B virus using transcriptional repressors that target the viral DNA. BMC Infect Dis 2019; 19:802. [PMID: 31510934 PMCID: PMC6739920 DOI: 10.1186/s12879-019-4436-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Accepted: 09/03/2019] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Chronic infection with hepatitis B virus (HBV) is a serious global health problem. Persistence of the virus occurs as a result of stability of the replication intermediate comprising covalently closed circular DNA (cccDNA). Development of drugs that are capable of disabling this cccDNA is vital. METHODS To investigate an epigenetic approach to inactivating viral DNA, we engineered transcriptional repressors that comprise an HBV DNA-binding domain of transcription activator like effectors (TALEs) and a fused Krüppel Associated Box (KRAB). These repressor TALEs (rTALEs) targeted the viral surface open reading frame and were placed under transcription control of constitutively active or liver-specific promoters. RESULTS Evaluation in cultured cells and following hydrodynamic injection of mice revealed that the rTALEs significantly inhibited production of markers of HBV replication without evidence of hepatotoxicity. Increased methylation of HBV DNA at CpG island II showed that the rTALEs caused intended epigenetic modification. CONCLUSIONS Epigenetic modification of HBV DNA is a new and effective means of inactivating the virus in vivo. The approach has therapeutic potential and avoids potentially problematic unintended mutagenesis of gene editing.
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Affiliation(s)
- Kristie Bloom
- Wits/SAMRC Antiviral Gene Therapy Research Unit, School of Pathology, Faculty of Health Science, University of the Witwatersrand, Private Bag 3, WITS, Johannesburg, 2050, South Africa
| | - Haajira Kaldine
- Wits/SAMRC Antiviral Gene Therapy Research Unit, School of Pathology, Faculty of Health Science, University of the Witwatersrand, Private Bag 3, WITS, Johannesburg, 2050, South Africa
| | - Toni Cathomen
- Institute for Transfusion Medicine and Gene Therapy, Medical Center - University of Freiburg, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Claudio Mussolino
- Institute for Transfusion Medicine and Gene Therapy, Medical Center - University of Freiburg, Freiburg, Germany
| | - Abdullah Ely
- Wits/SAMRC Antiviral Gene Therapy Research Unit, School of Pathology, Faculty of Health Science, University of the Witwatersrand, Private Bag 3, WITS, Johannesburg, 2050, South Africa
| | - Patrick Arbuthnot
- Wits/SAMRC Antiviral Gene Therapy Research Unit, School of Pathology, Faculty of Health Science, University of the Witwatersrand, Private Bag 3, WITS, Johannesburg, 2050, South Africa.
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4
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Scott T, Moyo B, Nicholson S, Maepa MB, Watashi K, Ely A, Weinberg MS, Arbuthnot P. ssAAVs containing cassettes encoding SaCas9 and guides targeting hepatitis B virus inactivate replication of the virus in cultured cells. Sci Rep 2017; 7:7401. [PMID: 28785016 PMCID: PMC5547162 DOI: 10.1038/s41598-017-07642-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 06/30/2017] [Indexed: 02/06/2023] Open
Abstract
Management of infection with hepatitis B virus (HBV) remains a global health problem. Persistence of stable covalently closed circular DNA (cccDNA) during HBV replication is responsible for modest curative efficacy of currently licensed drugs. Novel gene editing technologies, such as those based on CRISPR/Cas9, provide the means for permanently disabling cccDNA. However, efficient delivery of antiviral sequences to infected hepatocytes is challenging. A limiting factor is the large size of sequences encoding Cas9 from Streptococcus pyogenes, and resultant incompatibility with the popular single stranded adeno-associated viral vectors (ssAAVs). We thus explored the utility of ssAAVs for delivery of engineered CRISPR/Cas9 of Staphylococcus aureus (Sa), which is encoded by shorter DNA sequences. Short guide RNAs (sgRNAs) were designed with cognates in the S open reading frame of HBV and incorporated into AAVs that also encoded SaCas9. Intended targeted mutation of HBV DNA was observed after transduction of cells with the all-in-one vectors. Efficacy against HBV-infected hNTCP-HepG2 cells indicated that inactivation of cccDNA was successful. Analysis of likely off-target mutagenesis revealed no unintended sequence changes. Use of ssAAVs to deliver all components required to disable cccDNA by SaCas9 is novel and the technology has curative potential for HBV infection.
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Affiliation(s)
- Tristan Scott
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Health Sciences Faculty, University of the Witwatersrand, Johannesburg, South Africa
- HIV Pathogenesis Research Unit, Health Sciences Faculty, University of the Witwatersrand, Johannesburg, South Africa
| | - Buhle Moyo
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Health Sciences Faculty, University of the Witwatersrand, Johannesburg, South Africa
| | - Samantha Nicholson
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Health Sciences Faculty, University of the Witwatersrand, Johannesburg, South Africa
| | - Mohube Betty Maepa
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Health Sciences Faculty, University of the Witwatersrand, Johannesburg, South Africa
| | - Koichi Watashi
- National Institute of Infectious Diseases, Department of Virology II, Tokyo, Japan
| | - Abdullah Ely
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Health Sciences Faculty, University of the Witwatersrand, Johannesburg, South Africa
| | - Marc S Weinberg
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Health Sciences Faculty, University of the Witwatersrand, Johannesburg, South Africa
| | - Patrick Arbuthnot
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Health Sciences Faculty, University of the Witwatersrand, Johannesburg, South Africa.
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5
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van den Berg FT, Rossi JJ, Arbuthnot P, Weinberg MS. Design of Effective Primary MicroRNA Mimics With Different Basal Stem Conformations. MOLECULAR THERAPY-NUCLEIC ACIDS 2016; 5:e278. [PMID: 26756196 PMCID: PMC5012551 DOI: 10.1038/mtna.2015.53] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2015] [Accepted: 11/30/2015] [Indexed: 12/03/2022]
Abstract
Primary microRNA (pri-miRNA) mimics are important mediators of effective gene silencing and are well suited for sustained therapeutic applications. Pri-miRNA mimics are processed in the endogenous miRNA biogenesis pathway, where elements of the secondary RNA structure are crucial for efficient miRNA production. Cleavage of the pri-miRNA to a precursor miRNA (pre-miRNA) by Drosha-DGCR8 typically occurs adjacent to a basal stem of ~11 bp. However, a number of pri-miRNA structures are expected to contain slightly shorter or longer basal stems, which may be further disrupted in predicted folding of the expressed pri-miRNA sequence. We investigated the function and processing of natural and exogenous RNA guides from pri-miRNAs with various basal stems (9–13 bp), where a canonical hairpin was predicted to be well or poorly maintained in predicted structures of the expressed sequence. We have shown that RNA guides can be effectively derived from pri-miRNAs with various basal stem conformations, while predicted guide region stability can explain the function of pri-miRNA mimics, in agreement with previously proposed design principles. This study provides insight for the design of effective mimics based on naturally occurring pri-miRNAs and has identified several novel scaffolds suitable for use in gene silencing applications.
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Affiliation(s)
- Fiona T van den Berg
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - John J Rossi
- Department of Molecular and Cellular Biology, Beckman Research Institute of City of Hope, Duarte, California, USA
| | - Patrick Arbuthnot
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Marc S Weinberg
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa.,HIV Pathogenesis Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa.,Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, USA
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6
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Progress and Prospects of Anti-HBV Gene Therapy Development. Int J Mol Sci 2015; 16:17589-610. [PMID: 26263978 PMCID: PMC4581210 DOI: 10.3390/ijms160817589] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 07/20/2015] [Accepted: 07/22/2015] [Indexed: 12/11/2022] Open
Abstract
Despite the availability of an effective vaccine against hepatitis B virus (HBV), chronic infection with the virus remains a major global health concern. Current drugs against HBV infection are limited by emergence of resistance and rarely achieve complete viral clearance. This has prompted vigorous research on developing better drugs against chronic HBV infection. Advances in understanding the life cycle of HBV and improvements in gene-disabling technologies have been impressive. This has led to development of better HBV infection models and discovery of new drug candidates. Ideally, a regimen against chronic HBV infection should completely eliminate all viral replicative intermediates, especially covalently closed circular DNA (cccDNA). For the past few decades, nucleic acid-based therapy has emerged as an attractive alternative that may result in complete clearance of HBV in infected patients. Several genetic anti-HBV strategies have been developed. The most studied approaches include the use of antisense oligonucleotides, ribozymes, RNA interference effectors and gene editing tools. This review will summarize recent developments and progress made in the use of gene therapy against HBV.
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7
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Abstract
Silencing gene expression by harnessing the RNA interference (RNAi) pathway with short interfering RNAs (siRNAs) has useful analytical and potentially therapeutic application. To augment silencing efficacy of siRNAs, chemical modification has been employed to improve stability, target specificity, and delivery to target tissues. siRNAs incorporating guanidinopropyl (GP) moieties have demonstrated enhanced target gene silencing in cell culture and in vivo models of hepatitis B virus replication. Here we describe the synthesis of GP-modified siRNAs and use of 5' rapid amplification of cDNA ends (5' RACE) to verify an RNAi-mediated mechanism of action of these novel chemically modified siRNAs.
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8
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Gebbing M, Bergmann T, Schulz E, Ehrhardt A. Gene therapeutic approaches to inhibit hepatitis B virus replication. World J Hepatol 2015; 7:150-164. [PMID: 25729471 PMCID: PMC4342598 DOI: 10.4254/wjh.v7.i2.150] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 10/23/2014] [Accepted: 11/19/2014] [Indexed: 02/06/2023] Open
Abstract
Acute and chronic hepatitis B virus (HBV) infections remain to present a major global health problem. The infection can be associated with acute symptomatic or asymptomatic hepatitis which can cause chronic inflammation of the liver and over years this can lead to cirrhosis and the development of hepatocellular carcinomas. Currently available therapeutics for chronically infected individuals aim at reducing viral replication and to slow down or stop the progression of the disease. Therefore, novel treatment options are needed to efficiently combat and eradicate this disease. Here we provide a state of the art overview of gene therapeutic approaches to inhibit HBV replication. We discuss non-viral and viral approaches which were explored to deliver therapeutic nucleic acids aiming at reducing HBV replication. Types of delivered therapeutic nucleic acids which were studied since many years include antisense oligodeoxynucleotides and antisense RNA, ribozymes and DNAzymes, RNA interference, and external guide sequences. More recently designer nucleases gained increased attention and were exploited to destroy the HBV genome. In addition we mention other strategies to reduce HBV replication based on delivery of DNA encoding dominant negative mutants and DNA vaccination. In combination with available cell culture and animal models for HBV infection, in vitro and in vivo studies can be performed to test efficacy of gene therapeutic approaches. Recent progress but also challenges will be specified and future perspectives will be discussed. This is an exciting time to explore such approaches because recent successes of gene therapeutic strategies in the clinic to treat genetic diseases raise hope to find alternative treatment options for patients chronically infected with HBV.
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9
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Hean J, Crowther C, Ely A, Ul Islam R, Barichievy S, Bloom K, Weinberg MS, van Otterlo WA, de Koning CB, Salazar F, Marion P, Roesch EB, Lemaitre M, Herdewijn P, Arbuthnot P. Inhibition of hepatitis B virus replication in vivo using lipoplexes containing altritol-modified antiviral siRNAs. ARTIFICIAL DNA, PNA & XNA 2014; 1:17-26. [PMID: 21687523 DOI: 10.4161/adna.1.1.11981] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Revised: 04/06/2010] [Accepted: 04/07/2010] [Indexed: 01/15/2023]
Abstract
Chronic infection with the hepatitis B virus (HBV) occurs in approximately 6% of the world's population and carriers of the virus are at risk for complicating hepatocellular carcinoma. Current treatment options have limited efficacy and chronic HBV infection is likely to remain a significant global medical problem for many years to come. Silencing HBV gene expression by harnessing RNA interference (RNAi) presents an attractive option for development of novel and effective anti HBV agents. However, despite significant and rapid progress, further refinement of existing technologies is necessary before clinical application of RNAi-based HBV therapies is realized. Limiting off target effects, improvement of delivery efficiency, dose regulation and preventing reactivation of viral replication are some of the hurdles that need to be overcome. To address this, we assessed the usefulness of the recently described class of altritol-containing synthetic siRNAs (ANA siRNAs), which were administered as lipoplexes and tested in vivo in a stringent HBV transgenic mouse model. Our observations show that ANA siRNAs are capable of silencing of HBV replication in vivo. Importantly, non specific immunostimulation was observed with unmodified siRNAs and this undesirable effect was significantly attenuated by ANA modification. Inhibition of HBV replication of approximately 50% was achieved without evidence for induction of toxicity. These results augur well for future application of ANA siRNA therapeutic lipoplexes.
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Affiliation(s)
- Justin Hean
- Antiviral Gene Therapy Research Unit; School of Pathology; University of the Witwatersrand Medical School; South Africa
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10
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Inhibition of hepatitis B virus replication by helper dependent adenoviral vectors expressing artificial anti-HBV pri-miRs from a liver-specific promoter. BIOMED RESEARCH INTERNATIONAL 2014; 2014:718743. [PMID: 25003129 PMCID: PMC4066856 DOI: 10.1155/2014/718743] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Revised: 04/25/2014] [Accepted: 05/08/2014] [Indexed: 12/17/2022]
Abstract
Research on applying RNA interference (RNAi) to counter HBV replication has led to identification of potential therapeutic sequences. However, before clinical application liver-specific expression and efficient delivery of these sequences remain an important objective. We recently reported short-term inhibition of HBV replication in vivo by using helper dependent adenoviral vectors (HD Ads) expressing anti-HBV sequences from a constitutively active cytomegalovirus (CMV) promoter. To develop the use of liver-specific transcription regulatory elements we investigated the utility of the murine transthyretin (MTTR) promoter for expression of anti-HBV primary microRNAs (pri-miRs). HD Ads containing MTTR promoter effected superior expression of anti-HBV pri-miRs in mice compared to HD Ads containing the CMV promoter. MTTR-containing HD Ads resulted in HBV replication knockdown of up to 94% in mice. HD Ads expressing trimeric anti-HBV pri-miRs silenced HBV replication for 5 weeks. We previously showed that the product of the codelivered lacZ gene induces an immune response, and the duration of HBV silencing in vivo is likely to be attenuated by this effect. Nevertheless, expression of anti-HBV pri-miRs from MTTR promoter is well suited to countering HBV replication and development of HD Ads through attenuation of their immunostimulatory effects should advance their clinical utility.
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Inhibition of hepatitis B virus replication in cultured cells and in vivo using 2'-O-guanidinopropyl modified siRNAs. Bioorg Med Chem 2013; 21:6145-55. [PMID: 23743442 DOI: 10.1016/j.bmc.2013.04.073] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 04/10/2013] [Accepted: 04/19/2013] [Indexed: 12/11/2022]
Abstract
Silencing hepatitis B virus (HBV) gene expression with exogenous activators of the RNA interference (RNAi) pathway has shown promise as a new mode of treating infection with the virus. However, optimizing efficacy, specificity, pharmacokinetics and stability of RNAi activators remains a priority before clinical application of this promising therapeutic approach is realised. Chemical modification of synthetic short interfering RNAs (siRNAs) provides the means to address these goals. This study aimed to assess the benefits of incorporating nucleotides with 2'-O-guanidinopropyl (GP) modifications into siRNAs that target HBV. Single GP residues were incorporated at nucleotide positions from 2 to 21 of the antisense strand of a previously characterised effective antiHBV siRNA. When tested in cultured cells, siRNAs with GP moieties at selected positions improved silencing efficacy. Stability of chemically modified siRNAs in 80% serum was moderately improved and better silencing effects were observed without evidence for toxicity or induction of an interferon response. Moreover, partially complementary target sequences were less susceptible to silencing by siRNAs with GP residues located in the seed region. Hydrodynamic co-injection of siRNAs with a replication-competent HBV plasmid resulted in highly effective knock down of markers of viral replication in mice. Evidence for improved efficacy, reduced off target effects and good silencing in vivo indicate that GP-modifications of siRNAs may be used to enhance their therapeutic utility.
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12
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Green VA, Arbuthnot P, Weinberg MS. Impact of sustained RNAi-mediated suppression of cellular cofactor Tat-SF1 on HIV-1 replication in CD4+ T cells. Virol J 2012; 9:272. [PMID: 23153325 PMCID: PMC3511259 DOI: 10.1186/1743-422x-9-272] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 10/18/2012] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Conventional anti-HIV drug regimens targeting viral enzymes are plagued by the emergence of drug resistance. There is interest in targeting HIV-dependency factors (HDFs), host proteins that the virus requires for replication, as drugs targeting their function may prove protective. Reporter cell lines provide a rapid and convenient method of identifying putative HDFs, but this approach may lead to misleading results and a failure to detect subtle detrimental effects on cells that result from HDF suppression. Thus, alternative methods for HDF validation are required. Cellular Tat-SF1 has long been ascribed a cofactor role in Tat-dependent transactivation of viral transcription elongation. Here we employ sustained RNAi-mediated suppression of Tat-SF1 to validate its requirement for HIV-1 replication in a CD4+ T cell-derived line and its potential as a therapeutic target. RESULTS shRNA-mediated suppression of Tat-SF1 reduced HIV-1 replication and infectious particle production from TZM-bl reporter cells. This effect was not a result of increased apoptosis, loss of cell viability or an immune response. To validate its requirement for HIV-1 replication in a more relevant cell line, CD4+ SupT1 cell populations were generated that stably expressed shRNAs. HIV-1 replication was significantly reduced for two weeks (~65%) in cells with depleted Tat-SF1, although the inhibition of viral replication was moderate when compared to SupT1 cells expressing a shRNA targeting the integration cofactor LEDGF/p75. Tat-SF1 suppression was attenuated over time, resulting from decreased shRNA guide strand expression, suggesting that there is a selective pressure to restore Tat-SF1 levels. CONCLUSIONS This study validates Tat-SF1 as an HDF in CD4+ T cell-derived SupT1 cells. However, our findings also suggest that Tat-SF1 is not a critical cofactor required for virus replication and its suppression may affect cell growth. Therefore, this study demonstrates the importance of examining HIV-1 replication kinetics and cytotoxicity in cells with sustained HDF suppression to validate their therapeutic potential as targets.
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Affiliation(s)
- Victoria A Green
- Antiviral Gene Therapy Research Unit, Health Sciences Faculty, University of the Witwatersrand, Johannesburg, South Africa
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13
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Singh N, Ranjan A, Sur S, Chandra R, Tandon V. Inhibition of HIV-1 Integrase gene expression by 10-23 DNAzyme. J Biosci 2012; 37:493-502. [PMID: 22750986 DOI: 10.1007/s12038-012-9216-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
HIV Integrase (IN) is an enzyme that is responsible for the integration of the proviral genome into the human genome, and this integration step is the first step of the virus hijacking the human cell machinery for its propagation and replication. 10-23 DNAzyme has the potential to suppress gene expressions through sequence-specific mRNA cleavage. We have designed three novel DNAzymes, DIN54, DIN116, and DIN152, against HIV-1 Integrase gene using Mfold software and evaluated them for target site cleavage activity on the in vitro transcribed mRNA. All DNAzymes were tested for its inhibition of expression of HIV Integrase protein in the transiently transfected cell lines. DIN116 and DIN152 inhibited IN-EGFP expression by 80 percent and 70 percent respectively.
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MESH Headings
- Base Pairing
- Base Sequence
- DNA, Catalytic/chemistry
- DNA, Catalytic/genetics
- DNA, Catalytic/metabolism
- DNA, Single-Stranded/chemistry
- DNA, Single-Stranded/genetics
- DNA, Single-Stranded/metabolism
- Gene Expression
- Green Fluorescent Proteins/biosynthesis
- Green Fluorescent Proteins/genetics
- HIV Integrase/biosynthesis
- HIV Integrase/genetics
- HeLa Cells
- Humans
- Models, Molecular
- Nucleic Acid Conformation
- RNA Cleavage
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/genetics
- Software
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Affiliation(s)
- Nirpendra Singh
- Dr BR Ambedkar Center for Biomedical Research, University of Delhi, New Delhi 110 007, India
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14
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Scott T, Paweska JT, Arbuthnot P, Weinberg MS. Pathogenic effects of Rift Valley fever virus NSs gene are alleviated in cultured cells by expressed antiviral short hairpin RNAs. Antivir Ther 2012; 17:643-56. [DOI: 10.3851/imp2073] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2011] [Indexed: 10/28/2022]
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15
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Saayman S, Arbuthnot P, Weinberg MS. Deriving four functional anti-HIV siRNAs from a single Pol III-generated transcript comprising two adjacent long hairpin RNA precursors. Nucleic Acids Res 2010; 38:6652-63. [PMID: 20525791 PMCID: PMC2965221 DOI: 10.1093/nar/gkq460] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2010] [Revised: 05/07/2010] [Accepted: 05/11/2010] [Indexed: 11/19/2022] Open
Abstract
Several different approaches exist to generate expressed RNA interference (RNAi) precursors for multiple target inhibition, a strategy referred to as combinatorial (co)RNAi. One such approach makes use of RNA Pol III-expressed long hairpin RNAs (lhRNAs), which are processed by Dicer to generate multiple unique short interfering siRNA effectors. However, because of inefficient intracellular Dicer processing, lhRNA duplexes have been limited to generating two independent effective siRNA species. In this study, we describe a novel strategy whereby four separate anti-HIV siRNAs were generated from a single RNA Pol III-expressed transcript. Two optimized lhRNAs, each comprising two active anti-HIV siRNAs, were placed in tandem to form a double long hairpin (dlhRNA) expression cassette, which encodes four unique and effective siRNA sequences. Processing of the 3' position lhRNA was more variable but effective multiple processing was possible by manipulating the order of the siRNA-encoding sequences. Importantly, unlike shRNAs, Pol III-expressed dlhRNAs did not compete with endogenous and exogenous microRNAs to disrupt the RNAi pathway. The versatility of expressed lhRNAs is greatly expanded and we provide a mechanism for generating transcripts with modular lhRNAs motifs that contribute to improved coRNAi.
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Affiliation(s)
| | | | - Marc S. Weinberg
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of Witwatersrand, Johannesburg, South Africa
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16
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Dyer V, Ely A, Bloom K, Weinberg M, Arbuthnot P. tRNALys3 promoter cassettes that efficiently express RNAi-activating antihepatitis B virus short hairpin RNAs. Biochem Biophys Res Commun 2010; 398:640-6. [DOI: 10.1016/j.bbrc.2010.06.122] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2010] [Accepted: 06/29/2010] [Indexed: 12/22/2022]
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17
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Saayman SM, Arbuthnot P, Weinberg MS. Effective Pol III-expressed long hairpin RNAs targeted to multiple unique sites of HIV-1. Methods Mol Biol 2010; 629:159-74. [PMID: 20387149 DOI: 10.1007/978-1-60761-657-3_11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The RNA interference (RNAi) pathway has in recent years been exploited for the development of novel antiviral therapies. The emergence of viral escape mutants, however, is a major impediment to the use of RNAi effectors to treat highly mutable viruses such as HIV-1. A combinatorial approach is therefore required for long-term inhibition of gene expression. RNA Pol III-driven long hairpin RNA (lhRNA) duplexes can be cleaved several times by Dicer, yielding multiple functional siRNAs from a single construct. Here we describe a method for the generation of ectopically expressed U6-lhRNAs encoding three separate siRNA sequences targeting unique sites in HIV-1. This methodological overview explains some crucial aspects of lhRNA design and cloning as well as facile experiments to determine their efficacy in cell culture.
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Affiliation(s)
- Sheena M Saayman
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Wits, Johannesburg, South Africa
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18
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Chattopadhyay S, Ely A, Bloom K, Weinberg MS, Arbuthnot P. Inhibition of hepatitis B virus replication with linear DNA sequences expressing antiviral micro-RNA shuttles. Biochem Biophys Res Commun 2009; 389:484-9. [PMID: 19733548 DOI: 10.1016/j.bbrc.2009.09.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Accepted: 09/01/2009] [Indexed: 12/29/2022]
Abstract
RNA interference (RNAi) may be harnessed to inhibit viral gene expression and this approach is being developed to counter chronic infection with hepatitis B virus (HBV). Compared to synthetic RNAi activators, DNA expression cassettes that generate silencing sequences have advantages of sustained efficacy and ease of propagation in plasmid DNA (pDNA). However, the large size of pDNAs and inclusion of sequences conferring antibiotic resistance and immunostimulation limit delivery efficiency and safety. To develop use of alternative DNA templates that may be applied for therapeutic gene silencing, we assessed the usefulness of PCR-generated linear expression cassettes that produce anti-HBV micro-RNA (miR) shuttles. We found that silencing of HBV markers of replication was efficient (>75%) in cell culture and in vivo. miR shuttles were processed to form anti-HBV guide strands and there was no evidence of induction of the interferon response. Modification of terminal sequences to include flanking human adenoviral type-5 inverted terminal repeats was easily achieved and did not compromise silencing efficacy. These linear DNA sequences should have utility in the development of gene silencing applications where modifications of terminal elements with elimination of potentially harmful and non-essential sequences are required.
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Affiliation(s)
- Saket Chattopadhyay
- Antiviral Gene Therapy Research Unit, University of the Witwatersrand, Johannesburg, South Africa
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19
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Carmona S, Jorgensen MR, Kolli S, Crowther C, Salazar FH, Marion PL, Fujino M, Natori Y, Thanou M, Arbuthnot P, Miller AD. Controlling HBV Replication in Vivo by Intravenous Administration of Triggered PEGylated siRNA-Nanoparticles. Mol Pharm 2009; 6:706-17. [DOI: 10.1021/mp800157x] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Sergio Carmona
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
| | - Michael R. Jorgensen
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
| | - Soumia Kolli
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
| | - Carol Crowther
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
| | - Felix H. Salazar
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
| | - Patricia L. Marion
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
| | - Masato Fujino
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
| | - Yukikazu Natori
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
| | - Maya Thanou
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
| | - Patrick Arbuthnot
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
| | - Andrew D. Miller
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Private Bag 3, WITS 2050, South Africa, Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Armstrong Road, Imperial College London, London SW7 2AZ, U.K., Stanford University, Stanford, California, Hepadnavirus Testing, Inc., Mountain View, California, RNAi Co., Cosmos Hongo Bldg. 10F, 4-1-4, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and
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20
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Saayman S, Barichievy S, Capovilla A, Morris KV, Arbuthnot P, Weinberg MS. The efficacy of generating three independent anti-HIV-1 siRNAs from a single U6 RNA Pol III-expressed long hairpin RNA. PLoS One 2008; 3:e2602. [PMID: 18596982 PMCID: PMC2434202 DOI: 10.1371/journal.pone.0002602] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2007] [Accepted: 06/06/2008] [Indexed: 11/24/2022] Open
Abstract
RNA Interference (RNAi) effectors have been used to inhibit rogue RNAs in mammalian cells. However, rapidly evolving sequences such as the human immunodeficiency virus type 1 (HIV-1) require multiple targeting approaches to prevent the emergence of escape variants. Expressed long hairpin RNAs (lhRNAs) have recently been used as a strategy to produce multiple short interfering RNAs (siRNAs) targeted to highly variant sequences. We aimed to characterize the ability of expressed lhRNAs to generate independent siRNAs that silence three non-contiguous HIV-1 sites by designing lhRNAs comprising different combinations of siRNA-encoding sequences. All lhRNAs were capable of silencing individual target sequences. However, silencing efficiency together with concentrations of individual lhRNA-derived siRNAs diminished from the stem base (first position) towards the loop side of the hairpin. Silencing efficacy against HIV-1 was primarily mediated by siRNA sequences located at the base of the stem. Improvements could be made to first and second position siRNAs by adjusting spacing arrangements at their junction, but silencing of third position siRNAs remained largely ineffective. Although lhRNAs offer advantages for combinatorial RNAi, we show that good silencing efficacy across the span of the lhRNA duplex is difficult to achieve with sequences that encode more than two adjacent independent siRNAs.
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Affiliation(s)
- Sheena Saayman
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of Witwatersrand, Johannesburg, South Africa
| | - Samantha Barichievy
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of Witwatersrand, Johannesburg, South Africa
| | - Alexio Capovilla
- HIV Pathogenesis Lab, Department of Molecular Medicine and Haematology, University of Witwatersrand, Johannesburg, South Africa
| | - Kevin V. Morris
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, United States of America
| | - Patrick Arbuthnot
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of Witwatersrand, Johannesburg, South Africa
| | - Marc S. Weinberg
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of Witwatersrand, Johannesburg, South Africa
- * E-mail:
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21
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Ely A, Naidoo T, Mufamadi S, Crowther C, Arbuthnot P. Expressed anti-HBV primary microRNA shuttles inhibit viral replication efficiently in vitro and in vivo. Mol Ther 2008; 16:1105-12. [PMID: 18431360 DOI: 10.1038/mt.2008.82] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The use of RNA interference (RNAi) to inhibit gene expression is potentially applicable in the treatment of viral infections such as hepatitis B virus (HBV) persistence. Although efficient HBV gene silencing by short hairpin RNA (shRNA) expressed from RNA polymerase (Pol) III promoters has been reported, constitutive high-level transcription may cause harmful side effects. Here, we report an approach that allows the use of a Pol II promoter to improve transcription regulation of expressed RNAi effecters. Pol II [cytomegalovirus (CMV)] or Pol III (U6) promoter cassettes that transcribe anti-HBV primary microRNA (pri-miR)-122 and pri-miR-31 shuttles were generated. In cultured cells both types of pri-miR-like sequences effected knockdown of markers of viral replication (>80%) and were processed to form intended 21-nucleotide guides. The concentration of CMV-expressed miRs was approximately 85-fold lower than the U6 shRNA-derived guide RNA. When cells were co-transfected with pri-miR expression cassettes, attenuation of independent RNAi-mediated gene silencing was not observed, which is in contrast to the action of U6 shRNA expression cassettes. The efficacy of the anti-HBV pri-miR shuttles in vivo was verified using the murine hydrodynamic injection model. Employing Pol II-expressed pri-miR mimics may be useful in the treatment of HBV infection, and potentially also for generic application in RNAi-based therapy.
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Affiliation(s)
- Abdullah Ely
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Johannesburg, South Africa
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22
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Barichievy S, Saayman S, von Eije KJ, Morris KV, Arbuthnot P, Weinberg MS. The inhibitory efficacy of RNA POL III-expressed long hairpin RNAs targeted to untranslated regions of the HIV-1 5' long terminal repeat. Oligonucleotides 2008; 17:419-31. [PMID: 17896874 DOI: 10.1089/oli.2007.0095] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1) is a lentivirus that causes persistent infection resulting in the demise of immune regulatory cells, and ensuing diseases associated with acquired immune deficiency syndrome (AIDS). Although current therapeutic modalities have had a significant impact on mortality rates, novel therapies are constantly needed to prevent the emergence of resistant viral variants that escape the effects of antivirals. RNA Interference (RNAi) is a promising therapeutic modality for the inhibition of HIV-1 RNAs. Traditionally, RNAi effector sequences include expressed short hairpin RNAs (shRNAs) or short interfering RNAs (siRNAs). Recently, expressed long hairpin RNAs (lhRNAs) have been used with the aim of generating multiple independent siRNAs, which simultaneously target different susceptible sites on HIV-1. Here, modified lhRNAs expressed from U6 RNA Pol III promoters were targeted to sites within the first transcribed sequences of the HIV-1 5' long terminal repeat (LTR) region. Both Tat-dependent and independent suppressive efficacy was demonstrated against subtype B and C reporter sequences; however, lhRNAs complementary to the TAR stem-loop were refractory to silencing. None of the lhRNAs induced an unwanted interferon response as measured by interferon beta levels. Silencing by the lhRNAs was not equal across the extent of its cognate sequence, with the greatest efficacy observed for sequences located at the base of the stem. Nevertheless, direct antireplicative activity was seen when targeting lhRNAs to a subtype B HIV clone pNL4-3 Luc and a subtype C wild-type HIV-1 strain, FV5. These data highlight distinct target loci within the 5' LTR of HIV-1 that are susceptible to lhRNA targeting, and may prove to have an important advantage over other RNAi target sites within HIV-1. Although lhRNAs themselves require further manipulation to improve their overall efficacy in generating multiple functioning siRNAs, they may prove useful in any combinatorial-based approach to treating HIV-1 infection.
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Affiliation(s)
- Samantha Barichievy
- Antiviral Gene Therapy Unit, Department of Molecular Medicine and Haematology, University of Witwatersrand, Johannesburg, South Africa
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23
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Pardo M, Bartolomé J, Carreño V. Current therapy of chronic hepatitis B. Arch Med Res 2007; 38:661-77. [PMID: 17613358 DOI: 10.1016/j.arcmed.2006.12.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Accepted: 12/04/2006] [Indexed: 12/24/2022]
Affiliation(s)
- Margarita Pardo
- Fundación para el Estudio de las Hepatitis Virales, Madrid, Spain
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24
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Weinberg MS, Ely A, Passman M, Mufamadi SM, Arbuthnot P. Effective anti-hepatitis B virus hammerhead ribozymes derived from multimeric precursors. Oligonucleotides 2007; 17:104-12. [PMID: 17461767 DOI: 10.1089/oli.2006.0049] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Endonucleolytic hammerhead ribozymes have advantages of inhibiting gene expression by acting specifically, independently of cellular pathways, and within all cell compartments. However, there are concerns about inefficient silencing because of reduced intracellular cleavage of target RNA by ribozymes. To enable production of defined single-unit ribozymes and thereby increase effectiveness, we developed self-cleaving multimeric cassettes that generate several trans-acting ribozyme units from a single transcript. cis and trans ribozyme cleavage, as assessed in vitro against three different sites within the X sequence of hepatitis B virus (HBV), occurred efficiently and precisely according to predictions deduced from the ribozyme designs. Significant knockdown of markers of viral replication in transfected cultured liver-derived cells was achieved by multiribozyme Pol II expression cassettes. To assess silencing efficacy of RNA prepared in vitro, transcription and cis cleavage reactions were carried out to prepare defined single-unit ribozymes. Transfection of ribozyme RNA was capable of inhibiting HBV surface antigen secretion from liver-derived cells without associated elevation of interferon-alpha or interferon-beta secretion into the culture upernatants. The approach described here is potentially useful for several applications, such as generation of RNA interference (RNAi) effectors, which require rapid and inexpensive generation of defined RNA sequences.
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Affiliation(s)
- Marc S Weinberg
- Hepatitis B Virus Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, WITS 2050, South Africa
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25
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Weinberg MS, Ely A, Barichievy S, Crowther C, Mufamadi S, Carmona S, Arbuthnot P. Specific inhibition of HBV replication in vitro and in vivo with expressed long hairpin RNA. Mol Ther 2007; 15:534-41. [PMID: 17213835 DOI: 10.1038/sj.mt.6300077] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Activating RNA interference to achieve specific gene silencing has shown promise for the development of RNA-based treatment of chronic hepatitis B virus (HBV) infection. To further this approach, we assessed the efficacy of expressed long hairpin RNAs (lhRNAs) that target the conserved HBx open reading frame of HBV. As substrates for Dicer, lhRNAs have the potential to generate multiple short interfering RNAs (siRNAs) to enable simultaneous targeting of different sites. Two U6 Pol III vectors were constructed that encode anti-HBV lhRNAs with a 62 base pair stem sequence containing multiple G:U pairings. Assessment in transfected cultured cells and also in vivo using the murine hydrodynamic injection model showed that one of the lhRNA vectors (lhRNA 1) diminished markers of virus replication by 70-90% without evidence of interferon response induction. Greatest silencing efficacy was observed for targets that are complementary to sequences located at the base of the hairpin stem and this correlated with a higher concentration of siRNAs derived from this region of the lhRNA. Although lhRNA 1 has the advantage of targeting a greater viral sequence, incomplete cellular processing may result in unequal silencing across the span of the viral target RNA.
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Affiliation(s)
- Marc S Weinberg
- Hepatitis B Virus Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Wits, South Africa
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26
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Hou W, Ni Q, Wo J, Li M, Liu K, Chen L, Hu Z, Liu R, Hu M. Inhibition of hepatitis B virus X gene expression by 10-23 DNAzymes. Antiviral Res 2006; 72:190-6. [PMID: 16930733 DOI: 10.1016/j.antiviral.2006.07.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2005] [Revised: 06/03/2006] [Accepted: 07/04/2006] [Indexed: 01/08/2023]
Abstract
The X protein (HBx) of human hepatitis B virus (HBV) is a transcriptional activator protein. The HBx protein plays an important role in viral replication in HBV infected cells and the liver diseases including hepatitis, cirrhosis and hepatocellular carcinoma (HCC). Therefore, the repression of HBx gene expression by 10-23 DNAzymes might be a good way to inhibit HBV replication and counteract HBV-related liver diseases. We designed three 10-23 DNAzymes with different substrate-recognition domains. When each of the 10-23 DNAzymes were cotransfected into human AD293 cells with HBx-EGFP expression plasmid, they could all reduce the level of HBx mRNA as well as the HBx-EGFP protein. These results suggest that the 10-23 DNAzymes might be used for gene therapy of liver diseases caused by HBV.
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Affiliation(s)
- Wei Hou
- Key Laboratory of Infectious Diseases, Ministry of Public Health of China, Institute of Infectious Diseases, First Affiliated Hospital, College of Medical Sciences, Zhejiang University, Qingchun Road 79, Hangzhou, Zhejiang 310003, China
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27
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Cave E, Weinberg MS, Cilliers T, Carmona S, Morris L, Arbuthnot P. Silencing of HIV-1 subtype C primary isolates by expressed small hairpin RNAs targeted to gag. AIDS Res Hum Retroviruses 2006; 22:401-10. [PMID: 16706616 DOI: 10.1089/aid.2006.22.401] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Discovery of sequence-specific silencing by activating the RNA interference (RNAi) pathway has led to exciting new strategies for treating infection with human immunodeficiency virus type 1 (HIV-1). Of the HIV-1 subtypes, C is especially common in areas of the world that are worst affected. Although prone to mutation, genome plasticity of this subtype is limited in functionally important regions. We identified conserved sequences within the HIV-1 subtype C gag open reading frame and assessed whether they are suitable targets for inhibition of viral replication by RNA Pol III-driven small hairpin RNAs (shRNAs). Initially, the efficacy of each of a panel of 10 shRNAs against HIV-1 was determined using a reporter assay. shRNAs A and B, which targeted the 5 end of gag, were most effective and were used to assess inhibition of replication in cultured cells of two R5 isolates (Du151 and Du422) and one X4 virus (SW7). These shRNAs diminished intracellular HIV-1 gag RNA and HIV-1 protein concentrations as well as p24 secretion by up to 80% without inducing an interferon response. However, shRNA-mediated knockdown efficacy against each of these viral isolates varied slightly. These data show successful activation of RNAi to inhibit the replication of biologically distinct HIV-1 subtype C isolates. The effector shRNAs described here are potential candidates for gene therapy applications against the most common global subtype of HIV-1.
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Affiliation(s)
- Eleanor Cave
- HBV Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand, Wits 2050, Johannesburg, South Africa
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28
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Carmona S, Ely A, Crowther C, Moolla N, Salazar FH, Marion PL, Ferry N, Weinberg MS, Arbuthnot P. Effective inhibition of HBV replication in vivo by anti-HBx short hairpin RNAs. Mol Ther 2005; 13:411-21. [PMID: 16337206 DOI: 10.1016/j.ymthe.2005.10.013] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Revised: 10/08/2005] [Accepted: 10/27/2005] [Indexed: 01/29/2023] Open
Abstract
Exploiting the RNA interference pathway has shown promise for developing novel and effective treatment of hepatitis B virus (HBV) infection. To advance this approach, we analyzed the antiviral efficacy of a panel of 10 Pol III U6 promoter-encoded short hairpin RNAs (shRNAs) that target conserved sequences of the oncogenic HBx open reading frame. To facilitate intracellular processing, the shRNAs included mismatches in the 25-bp stem region and a terminal loop of miRNA-23. Two shRNAs (shRNA 5 and shRNA 6) showed knockdown of HBV markers by 80-100% in transfected hepatocytes and also in a murine hydrodynamic injection model of HBV replication. Intracellular processing of hairpin RNA with the intended strand bias correlated with antiviral efficacy. Moreover, markers of HBV replication were inhibited without inducing genes associated with the nonspecific interferon response. To assess the antiviral efficacy of the shRNAs in a context that is similar to natural HBV infection, shRNA-encoding cassettes were tested against the virus in a HBV transgenic murine model. When delivered using recombinant adenovirus vectors, U6 shRNA 5 and U6 shRNA 6 mediated significant HBV knockdown. Collectively, these observations indicate that U6 shRNA 5 and U6 shRNA 6 are promising candidates for therapy of chronic HBV infection.
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Affiliation(s)
- Sergio Carmona
- Hepatitis B Virus Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, Wits, South Africa
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29
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Nash KL, Alexander GJM, Lever AML. Inhibition of hepatitis B virus by lentiviral vector delivered antisense RNA and hammerhead ribozymes. J Viral Hepat 2005; 12:346-56. [PMID: 15985004 DOI: 10.1111/j.1365-2893.2005.00612.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Chronic hepatitis B virus (HBV) infection is an important cause of cirrhosis and hepatocellular carcinoma. Current treatments are limited and may be ineffective. Nucleic acid-mediated targeting of viral mRNA is an attractive and specific approach for viral infection and lentiviral vectors provide a means to express antisense sequences or ribozymes stably in target cells permitting continuous production within that cell and its progeny. To demonstrate long-term gene expression by lentiviral vectors in hepatocytes and to introduce lentiviral vectors expressing anti-HBV genes to assess their effect against HBV, lentiviral vectors expressing a reporter gene were assessed for longevity of gene expression in hepatocytes in vitro. Hammerhead ribozymes and antisense sequences targeting the HBV encapsidation signal (epsilon), X or surface antigen on mRNAs were cloned into lentiviral vectors and used to transduce HBV expressing hepatocytes where the effect on HBV mRNA level was assessed using ribonuclease protection. Gene expression in hepatocytes from integrated vectors continued for over 4 months without selection. Antisense RNA targeting HBs mRNA reduced this transcript, whilst antisense RNA to HBX mRNA was ineffective. Sense RNAs corresponding to epsilon and HBX mRNA also reduced HBV mRNA levels. Ribozymes targeting HBs and HBX mRNA effectively reduced HBV mRNA levels compared with inactive constructs indicating their effect to be enzymatic rather than antisense. Lentiviral vectors can produce long-term gene expression in hepatocytes and thus permit prolonged expression of antiviral genes targeting the HBV encapsidation signal, surface and X mRNAs as treatments for chronic HBV infection.
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Affiliation(s)
- K L Nash
- Department of Medicine, University of Cambridge, Addenbrooke's, Hospital, Hills Road, Cambridge, UK
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Abstract
With the advent of functional genomics and the shift of interest towards sequence-based therapeutics, the past decades have witnessed intense research efforts on nucleic acid-mediated gene regulation technologies. Today, RNA interference is emerging as a groundbreaking discovery, holding promise for development of genetic modulators of unprecedented potency. Twenty-five years after the discovery of antisense RNA and ribozymes, gene control therapeutics are still facing developmental difficulties, with only one US FDA-approved antisense drug currently available in the clinic. Limited predictability of target site selection models is recognized as one major stumbling block that is shared by all of the so-called complementary technologies, slowing the progress towards a commercial product. Currently employed in vitro systems for target site selection include RNAse H-based mapping, antisense oligonucleotide microarrays, and functional screening approaches using libraries of catalysts with randomized target-binding arms to identify optimal ribozyme/DNAzyme cleavage sites. Individually, each strategy has its drawbacks from a drug development perspective. Utilization of message-modulating sequences as therapeutic agents requires that their action on a given target transcript meets criteria of potency and selectivity in the natural physiological environment. In addition to sequence-dependent characteristics, other factors will influence annealing reactions and duplex stability, as well as nucleic acid-mediated catalysis. Parallel consideration of physiological selection systems thus appears essential for screening for nucleic acid compounds proposed for therapeutic applications. Cellular message-targeting studies face issues relating to efficient nucleic acid delivery and appropriate analysis of response. For reliability and simplicity, prokaryotic systems can provide a rapid and cost-effective means of studying message targeting under pseudo-cellular conditions, but such approaches also have limitations. To streamline nucleic acid drug discovery, we propose a multi-model strategy integrating high-throughput-adapted bacterial screening, followed by reporter-based and/or natural cellular models and potentially also in vitro assays for characterization of the most promising candidate sequences, before final in vivo testing.
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Affiliation(s)
- Isabelle Gautherot
- Virology Platform, Industrialization and Process Development, AVENTIS PASTEUR, Marcy l'Etoile, France.
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N/A. N/A. Shijie Huaren Xiaohua Zazhi 2003; 11:238-241. [DOI: 10.11569/wcjd.v11.i2.238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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Pan WH, Xin P, Bui V, Clawson GA. Rapid identification of efficient target cleavage sites using a hammerhead ribozyme library in an iterative manner. Mol Ther 2003; 7:129-39. [PMID: 12573626 DOI: 10.1016/s0000-000x(00)00000-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
A major limitation to the effectiveness of ribozymes is definition of accessible sites in targeted RNAs. Although library selection procedures have been developed, they are generally difficult to perform and have not been widely employed. Here we describe a selection technology that utilizes a randomized, active hammerhead ribozyme (Rz) library in an iterative manner. After two rounds of binding under inactive conditions, the selected, active Rz library is incubated with target RNA, and the sites of cleavage are identified on sequencing gels. We performed this library-selection protocol using human papillomavirus type 16 E6/E7 mRNA as target and constructed Rz targeted to the identified sites. Rz targeted to sites identified with this procedure were generally highly active in vitro and, more importantly, they were highly active in cell culture, whereas their catalytically inactive counterparts were not. This protocol can be used to identify a set of potential target sites within a relatively short time.
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MESH Headings
- Base Sequence
- DNA Primers
- Hydrolysis
- Kinetics
- Molecular Sequence Data
- Nucleic Acid Conformation
- Oncogene Proteins, Viral/genetics
- Papillomavirus E7 Proteins
- RNA, Catalytic/chemistry
- RNA, Catalytic/genetics
- RNA, Catalytic/metabolism
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Viral/chemistry
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
- Wei-Hua Pan
- Department of Pathology, Gittlen Cancer Research Institute, Hershey Medical Center, Pennsylvania State University, Hershey, Pennsylvania 17033, USA
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Bergeron LJ, Perreault JP. Development and comparison of procedures for the selection of delta ribozyme cleavage sites within the hepatitis B virus. Nucleic Acids Res 2002; 30:4682-91. [PMID: 12409459 PMCID: PMC135815 DOI: 10.1093/nar/gkf598] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2002] [Revised: 09/09/2002] [Accepted: 09/09/2002] [Indexed: 01/01/2023] Open
Abstract
Delta ribozyme possesses several unique features related to the fact that it is the only catalytic RNA known to be naturally active in human cells. This makes it attractive as a therapeutic tool for the inactivation of clinically relevant RNAs. However, several hurdles must be overcome prior to the development of useful gene-inactivation systems based on delta ribozyme. We have developed three procedures for the selection of potential delta ribozyme target sites within the hepatitis B virus (HBV) pregenome: (i) the use of bioinformatic tools coupled to biochemical assays; (ii) RNase H hydrolysis with a pool of oligonucleotides; and (iii) cleavage assays with a pool of ribozymes. The results obtained with delta ribozyme show that these procedures are governed by several rules, some of which are different from those both for other catalytic RNAs and antisense oligonucleotides. Together, these procedures identified 12 sites in the HBV pregenome that can be cleaved by delta ribozymes, although with different efficiencies. Clearly, both target site accessibility and the ability to form an active ribozyme-substrate complex constitute interdependent factors that can best be addressed using a combinatorial library of either oligonucleotides or ribozymes.
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Affiliation(s)
- Lucien Junior Bergeron
- RNA Group/Groupe ARN, Département de Biochimie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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Maniotis D, Wood MJA, Phylactou LA. Hammerhead ribozymes reduce central nervous system (CNS)-derived neuronal nitric oxide synthase messenger RNA in a human cell line. Neurosci Lett 2002; 329:81-5. [PMID: 12161268 DOI: 10.1016/s0304-3940(02)00582-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Catalytic RNA molecules (ribozymes) have been widely used specifically to suppress gene expression. Neuronal nitric oxide synthase (nNOS) is an important molecule involved in normal central nervous system function (e.g. vasodilation, neurotransmission.) and disease (e.g. oxidative stress). This report is an investigation of the hammerhead ribozyme function and potential in the central nervous system using nNOS as a model. Two antisense hammerhead ribozymes, nNOS-RZ1 and nNOS-RZ2, were designed and constructed against nNOS messenger RNA (mRNA). In vitro (cell-free) experiments demonstrated the ability of both ribozymes to cleave nNOS RNA targets. Ribozyme-mediated reduction of the endogenous nNOS mRNA in human TGW-I-nu neuroblastoma cells was demonstrated by plasmid- and adenovirus-mediated transfections. These results may form the basis for studying neuronal gene expression and for designing RNA-directed therapeutic strategies for neurological diseases that involve oxidative stress.
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Affiliation(s)
- D Maniotis
- Department of Human Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK.
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Tan TMC, Zhou L, Houssais S, Seet BL, Jaenicke S, Peter F, Lim SG. Intracellular inhibition of hepatitis B virus S gene expression by chimeric DNA-RNA phosphorothioate minimized ribozyme. ANTISENSE & NUCLEIC ACID DRUG DEVELOPMENT 2002; 12:257-64. [PMID: 12238814 DOI: 10.1089/108729002320351575] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Chronic hepatitis B virus (HBV) infection is a major problem in Asia. Current therapies for chronic hepatitis B have limited efficacy. The successful use of ribozymes for intracellular inhibition of HBV gene expression was recently reported. As an alternative to ribozymes, the use of DNA-containing, phosphorothioate-modified, minimized hammerhead ribozymes (minizymes) to inhibit hepatitis B surface antigen (HBsAg) expression and viral replication was investigated. Such molecules can be synthesized and supplied exogenously. Two conserved sites within the HBsAg open reading frame (ORF) were targeted. PLC/PRF5 cells or 2.2.15 cells were treated with minizymes or antisense oligomers to assess the effects on cell viability, HBsAg expression, and viral DNA production. Treatment with the minizyme, MZPS1, resulted in >80% inhibition of HBsAg expression in PLC/PRF5 cells. MZPS1 had more inhibitory effect than the antisense oligonucletoide target at the same region, whereas the control minizyme had little effect. Another gene-specific minizyme, MZPS2, did not show any effect. Treated cells remained fully viable. Treatment of 2.2.15 cells with MZPS1 also led to decreased HBsAg expression. In addition, a 2.3-fold decrease in viral production was observed. Our data showed that minizymes can inhibit HBV gene expression and may potentially be useful for clinical therapy against chronic HBV infection.
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Feng Y, Kong YY, Wang Y, Qi GR. Intracellular inhibition of the replication of hepatitis B virus by hammerhead ribozymes. J Gastroenterol Hepatol 2001; 16:1125-30. [PMID: 11686839 DOI: 10.1046/j.1440-1746.2001.02548.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND Chronic hepatitis B virus (HBV) infection is frequently associated with cirrhosis and hepatocellular carcinoma, and so has become a major worldwide health problem. Hammerhead ribozymes have recently gained some attention as potential tools to inhibit viral infection, for which there are no general effective therapies available. METHODS A hammerhead ribozyme, RzC, was designed to target the sequence encoding the tail region of the HBV core protein. The activities of the ribozyme were analyzed in vitro and in human hepatoma (HepG2) cells. RESULTS In vitro, RzC cleaves HBV-RNA at its target site up to 30%, while the disabled ribozyme, dRzC, which has a one-base mutation in the catalytic site, did not cleave the target RNA at all. When the ribozymes were cotransfected into HepG2 cells with the HBV genome-containing plasmid, p3.6II, the inhibition of HBV replication by RzC was greater than that by dRzC, indicating that the active catalytic domain of the hammerhead ribozyme could increase the extent of antisense-mediated inhibition. In addition, there was a gradient of effectiveness in which the greater the amount of released ribozyme, the greater the reduction in HBV progeny DNA. CONCLUSIONS These results suggest the possibility of hammerhead ribozyme-mediated gene therapy for the treatment of HBV infections.
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Affiliation(s)
- Y Feng
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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