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Jacobs R, Singh P, Smith T, Arbuthnot P, Maepa MB. Prospects of viral vector-mediated delivery of sequences encoding anti-HBV designer endonucleases. Gene Ther 2022:10.1038/s41434-022-00342-5. [PMID: 35606493 DOI: 10.1038/s41434-022-00342-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 05/05/2022] [Accepted: 05/06/2022] [Indexed: 11/09/2022]
Abstract
Available treatment for chronic hepatitis B virus (HBV) infection offers modest functional curative efficacy. The viral replicative intermediate comprising covalently closed circular DNA (cccDNA) is responsible for persistent chronic HBV infection. Hence, current efforts have focused on developing therapies that disable cccDNA. Employing gene editing tools has emerged as an attractive strategy, with the end goal of establishing permanently inactivated cccDNA. Although anti-HBV designer nucleases are effective in vivo, none has yet progressed to clinical trial. Lack of safe and efficient delivery systems remains the limiting factor. Several vectors may be used to deliver anti-HBV gene editor-encoding sequences, with viral vectors being at the forefront. Despite the challenges associated with packaging large gene editor-encoding sequences into viral vectors, advancement in the field is overcoming such limitations. Translation of viral vector-mediated gene editing against HBV to clinical application is within reach. This review discusses the prospects of delivering HBV targeted designer nucleases using viral vectors.
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Affiliation(s)
- Ridhwaanah Jacobs
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Prashika Singh
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Tiffany Smith
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Patrick Arbuthnot
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Mohube Betty Maepa
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
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2
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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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3
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Sustained inhibition of hepatitis B virus replication in vivo using RNAi-activating lentiviruses. Gene Ther 2014; 22:163-71. [PMID: 25338920 DOI: 10.1038/gt.2014.94] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 08/26/2014] [Accepted: 09/17/2014] [Indexed: 12/15/2022]
Abstract
Chronic infection with hepatitis B virus (HBV) puts individuals at high risk for complicating cirrhosis and liver cancer, but available treatment to counter the virus rarely eliminates infection. Although harnessing RNA interference (RNAi) to silence HBV genes has shown the potential, achieving efficient and durable silencing of viral genes remains an important goal. Here we report on the propagation of lentiviral vectors (LVs) that successfully deliver HBV-targeting RNAi activators to liver cells. Mono- and tricistronic artificial primary microRNAs (pri-miRs) derived from pri-miR-31, placed under transcriptional control of the liver-specific modified murine transthyretin (mTTR) promoter, caused efficient inhibition of HBV replication markers. The tricistronic cassette was capable of silencing a mutant viral target and the effects were observed without disrupting the function of an endogenous miR (miR-16). The mTTR promoter stably expressed a reporter transgene in mouse livers over a study period of 1 year. Good silencing of HBV genes, without evidence of toxicity, was demonstrated following intravenous injection of LVs into neonatal HBV transgenic mice. Collectively, these data indicate that LVs may achieve sustained inhibition of HBV replication that is appealing for their therapeutic use.
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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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Shi B, Abrams M. Technologies for investigating the physiological barriers to efficient lipid nanoparticle-siRNA delivery. J Histochem Cytochem 2013; 61:407-20. [PMID: 23504369 PMCID: PMC3715328 DOI: 10.1369/0022155413484152] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 02/20/2013] [Indexed: 11/22/2022] Open
Abstract
Small interfering RNA (siRNA) therapeutics have advanced from bench to clinical trials in recent years, along with new tools developed to enable detection of siRNA delivered at the organ, cell, and subcellular levels. Preclinical models of siRNA delivery have benefitted from methodologies such as stem-loop quantitative polymerase chain reaction, histological in situ immunofluorescent staining, endosomal escape assay, and RNA-induced silencing complex loading assay. These technologies have accelerated the detection and optimization of siRNA platforms to overcome the challenges associated with delivering therapeutic oligonucleotides to the cytosol of specific target cells. This review focuses on the methodologies and their application in the biodistribution of siRNA delivered by lipid nanoparticles.
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Affiliation(s)
- Bin Shi
- Department of RNA Therapeutics, Merck Research Laboratories, Merck & Co., Inc., West Point, Pennsylvania, USA.
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Abstract
Human immunodeficiency virus type 1 (HIV-1), hepatitis B virus (HBV), and herpes simplex virus (HSV) have been incurable to date because effective antiviral therapies target only replicating viruses and do not eradicate latently integrated or nonreplicating episomal viral genomes. Endonucleases that can target and cleave critical regions within latent viral genomes are currently in development. These enzymes are being engineered with high specificity such that off-target binding of cellular DNA will be absent or minimal. Imprecise nonhomologous-end-joining (NHEJ) DNA repair following repeated cleavage at the same critical site may permanently disrupt translation of essential viral proteins. We discuss the benefits and drawbacks of three types of DNA cleavage enzymes (zinc finger endonucleases, transcription activator-like [TAL] effector nucleases [TALENs], and homing endonucleases [also called meganucleases]), the development of delivery vectors for these enzymes, and potential obstacles for successful treatment of chronic viral infections. We then review issues regarding persistence of HIV-1, HBV, and HSV that are relevant to eradication with genome-altering approaches.
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Shi B, Keough E, Matter A, Leander K, Young S, Carlini E, Sachs AB, Tao W, Abrams M, Howell B, Sepp-Lorenzino L. Biodistribution of small interfering RNA at the organ and cellular levels after lipid nanoparticle-mediated delivery. J Histochem Cytochem 2011; 59:727-40. [PMID: 21804077 PMCID: PMC3261601 DOI: 10.1369/0022155411410885] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chemically stabilized small interfering RNA (siRNA) can be delivered systemically by intravenous injection of lipid nanoparticles (LNPs) in rodents and primates. The biodistribution and kinetics of LNP-siRNA delivery in mice at organ and cellular resolution have been studied using immunofluorescence (IF) staining and quantitative polymerase chain reaction (qPCR). At 0.5 and 2 hr post tail vein injection of Cy5-labeled siRNA encapsulated in LNP, the organ rank-order of siRNA levels is liver > spleen > kidney, with only negligible accumulation in duodenum, lung, heart, and brain. Similar conclusions were drawn by using qPCR to measure tissue siRNA levels as a secondary end point. siRNA levels in these tissues decreased by more than 10-fold after 24 hr. Within the liver, LNPs delivered siRNA to hepatocytes, Kupffer cells, and sinusoids in a time-dependent manner, as revealed by IF staining and signal quantitation methods established using OPERA/Columbus software. siRNA first accumulated in liver sinusoids and trafficked to hepatocytes by 2 hr post dose, corresponding to the onset of target mRNA silencing. Fluorescence in situ hybridization methods were used to detect both strands of siRNA in fixed tissues. Collectively, the authors have implemented a platform to evaluate biodistribution of siRNA across cell types and across tissues in vivo, with the objective of elucidating the pharmacokinetic and pharmacodynamic relationship to guide optimization of delivery vehicles.
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Affiliation(s)
- Bin Shi
- Department of RNA Therapeutics, Merck Research Laboratories, Merck & Co, West Point, Pennsylvania 19486, USA.
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Weinberg MS, Arbuthnot P. Progress in the use of RNA interference as a therapy for chronic hepatitis B virus infection. Genome Med 2010; 2:28. [PMID: 20429960 PMCID: PMC2873806 DOI: 10.1186/gm149] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Chronic infection with hepatitis B virus (HBV) occurs in approximately 6% of the world's population and carriers of the virus are at risk for hepatocellular carcinoma and cirrhosis. Current treatment regimens, which include interferon-α and nucleoside/nucleotide analogs, are only partially effective and new treatment methods remain an important objective. Harnessing the RNA interference (RNAi) pathway to achieve post-transcriptional silencing of rogue genetic elements is an exciting avenue for development of novel therapeutic strategies. The specific and potent suppression of HBV gene expression and replication is an attractive option as a novel and effective approach for the treatment of chronic HBV infection. However, despite significant and rapid progress, existing RNAi technologies require further refinement before clinical applications can be realized. Here, we review current efforts aimed at improving the efficiency of anti-HBV RNAi-based delivery systems, at limiting the toxicities associated with RNAi modalities and at preventing reactivation of viral replication. We discuss the progress towards clinical implementation of anti-HBV RNAi therapies.
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Affiliation(s)
- Marc S Weinberg
- Antiviral Gene Therapy Research Unit, Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School, WITS 2050, South Africa.
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Ely A, Naidoo T, Arbuthnot P. Efficient silencing of gene expression with modular trimeric Pol II expression cassettes comprising microRNA shuttles. Nucleic Acids Res 2009; 37:e91. [PMID: 19474340 PMCID: PMC2715259 DOI: 10.1093/nar/gkp446] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Expressed polycistronic microRNA (miR) cassettes have useful properties that can be utilized for RNA interference (RNAi)-based gene silencing. To advance their application we generated modular trimeric anti-hepatitis B virus (HBV) Pol II cassettes encoding primary (pri)-miR-31-derived shuttles that target three different viral genome sites. A panel of six expression cassettes, comprising each of the possible ordering combinations of the pri-miR-31 shuttles, was initially tested. Effective silencing of individual target sequences was achieved in transfected cells and transcribed pri-miR trimers generated intended guide strands. There was, however, variation in processing and silencing by each of the shuttles. In some cases the monomers’ position within the trimers influenced processing and this correlated with target silencing. Compromised efficacy could be compensated by substituting the pri-miR-31 backbone with a pri-miR-30a scaffold. Inhibition of HBV replication was achieved in vivo, and in cell culture without disruption of endogenous miR function or induction of the interferon response. A mutant HBV target sequence, with changes in one of the guide cognates, was also silenced by the trimeric cassettes. The modular nature of the cassettes together with compatibility with expression from Pol II promoters should be advantageous for gene silencing applications requiring simultaneous targeting of different sites.
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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, Private Bag 3 WITS 2050, South Africa
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