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Shen S, Liu W, Zeng G, Liang H, Yu X, Zhang H, Sun J, Guo H. Conditional replication and secretion of hepatitis B virus genome uncover the truncated 3' terminus of encapsidated viral pregenomic RNA. J Virol 2023; 97:e0076023. [PMID: 37754759 PMCID: PMC10617516 DOI: 10.1128/jvi.00760-23] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Accepted: 08/07/2023] [Indexed: 09/28/2023] Open
Abstract
IMPORTANCE The biogenesis and clinical application of serum HBV pgRNA have been a research hotspot in recent years. This study further characterized the heterogeneity of the 3' terminus of capsid RNA by utilizing a variety of experimental systems conditionally supporting HBV genome replication and secretion, and reveal that the 3' truncation of capsid pgRNA is catalyzed by cellular ribonuclease(s) and viral RNaseH at positions after and before 3' DR1, respectively, indicating the 3' DR1 as a boundary between the encapsidated portion of pgRNA for reverse transcription and the 3' unprotected terminus, which is independent of pgRNA length and the 3' terminal sequence. Thus, our study provides new insights into the mechanism of pgRNA encapsidation and reverse transcription, as well as the optimization of serum HBV RNA diagnostics.
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Affiliation(s)
- Sheng Shen
- Department of Infectious Diseases, State Key Laboratory of Organ Failure Research, Key Laboratory of Infectious Diseases Research in South China, Ministry of Education, Guangdong Provincial Key Laboratory of Viral Hepatitis Research, Nanfang Hospital, Southern Medical University, Guangzhou, China
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Cancer Virology Program, UPMC Hillman Cancer Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Wendong Liu
- Department of Infectious Diseases, State Key Laboratory of Organ Failure Research, Key Laboratory of Infectious Diseases Research in South China, Ministry of Education, Guangdong Provincial Key Laboratory of Viral Hepatitis Research, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Ge Zeng
- Department of Infectious Diseases, State Key Laboratory of Organ Failure Research, Key Laboratory of Infectious Diseases Research in South China, Ministry of Education, Guangdong Provincial Key Laboratory of Viral Hepatitis Research, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Hongyan Liang
- Department of Infectious Diseases, State Key Laboratory of Organ Failure Research, Key Laboratory of Infectious Diseases Research in South China, Ministry of Education, Guangdong Provincial Key Laboratory of Viral Hepatitis Research, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Xiaoyang Yu
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Cancer Virology Program, UPMC Hillman Cancer Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Hu Zhang
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Cancer Virology Program, UPMC Hillman Cancer Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Jian Sun
- Department of Infectious Diseases, State Key Laboratory of Organ Failure Research, Key Laboratory of Infectious Diseases Research in South China, Ministry of Education, Guangdong Provincial Key Laboratory of Viral Hepatitis Research, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Haitao Guo
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Cancer Virology Program, UPMC Hillman Cancer Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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Olenginski LT, Attionu SK, Henninger EN, LeBlanc RM, Longhini AP, Dayie TK. Hepatitis B Virus Epsilon (ε) RNA Element: Dynamic Regulator of Viral Replication and Attractive Therapeutic Target. Viruses 2023; 15:1913. [PMID: 37766319 PMCID: PMC10534774 DOI: 10.3390/v15091913] [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] [Received: 07/01/2023] [Revised: 09/01/2023] [Accepted: 09/05/2023] [Indexed: 09/29/2023] Open
Abstract
Hepatitis B virus (HBV) chronically infects millions of people worldwide, which underscores the importance of discovering and designing novel anti-HBV therapeutics to complement current treatment strategies. An underexploited but attractive therapeutic target is ε, a cis-acting regulatory stem-loop RNA situated within the HBV pregenomic RNA (pgRNA). The binding of ε to the viral polymerase protein (P) is pivotal, as it triggers the packaging of pgRNA and P, as well as the reverse transcription of the viral genome. Consequently, small molecules capable of disrupting this interaction hold the potential to inhibit the early stages of HBV replication. The rational design of such ligands necessitates high-resolution structural information for the ε-P complex or its individual components. While these data are currently unavailable for P, our recent structural elucidation of ε through solution nuclear magnetic resonance spectroscopy marks a significant advancement in this area. In this review, we provide a brief overview of HBV replication and some of the therapeutic strategies to combat chronic HBV infection. These descriptions are intended to contextualize our recent experimental efforts to characterize ε and identify ε-targeting ligands, with the ultimate goal of developing novel anti-HBV therapeutics.
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Affiliation(s)
- Lukasz T. Olenginski
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA (R.M.L.)
- Department of Biochemistry, University of Colorado, Boulder, CO 80309, USA
| | - Solomon K. Attionu
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA (R.M.L.)
| | - Erica N. Henninger
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA (R.M.L.)
| | - Regan M. LeBlanc
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA (R.M.L.)
| | - Andrew P. Longhini
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA (R.M.L.)
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Theodore K. Dayie
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA (R.M.L.)
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Kamzeeva PN, Aralov AV, Alferova VA, Korshun VA. Recent Advances in Molecular Mechanisms of Nucleoside Antivirals. Curr Issues Mol Biol 2023; 45:6851-6879. [PMID: 37623252 PMCID: PMC10453654 DOI: 10.3390/cimb45080433] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/12/2023] [Accepted: 08/14/2023] [Indexed: 08/26/2023] Open
Abstract
The search for new drugs has been greatly accelerated by the emergence of new viruses and drug-resistant strains of known pathogens. Nucleoside analogues (NAs) are a prospective class of antivirals due to known safety profiles, which are important for rapid repurposing in the fight against emerging pathogens. Recent improvements in research methods have revealed new unexpected details in the mechanisms of action of NAs that can pave the way for new approaches for the further development of effective drugs. This review accounts advanced techniques in viral polymerase targeting, new viral and host enzyme targeting approaches, and prodrug-based strategies for the development of antiviral NAs.
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Affiliation(s)
| | | | | | - Vladimir A. Korshun
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Miklukho-Maklaya 16/10, 117997 Moscow, Russia; (P.N.K.); (A.V.A.); (V.A.A.)
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4
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Squires KE, Ogilvie L, Jucov A, Anastasiy I, Ghicavii N, Huguet J, Melara R, Constantineau M, De La Rosa A, Mayers DL. A randomized phase 1b trial of the active site polymerase inhibitor nucleotide ATI-2173 in patients with chronic hepatitis B virus infection. J Viral Hepat 2023; 30:19-28. [PMID: 36201354 PMCID: PMC10092119 DOI: 10.1111/jvh.13753] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 09/13/2022] [Accepted: 09/13/2022] [Indexed: 01/15/2023]
Abstract
ATI-2173 is an active site polymerase inhibitor nucleotide in development as part of a potentially curative regimen for chronic hepatitis B virus (HBV) infection. This study evaluated the safety, tolerability, pharmacokinetics (PK) and antiviral activity of ATI-2173. This was a phase 1b, randomized, double-blind, placebo-controlled trial in treatment-naive adults with chronic HBV infection conducted in the Republic of Moldova and Ukraine (ClinicalTrials.gov: NCT04248426). Patients positive for hepatitis B surface antigen were randomized 6:2 to receive once-daily oral doses of ATI-2173 10, 25, or 50 mg (n = 6 per dose) or placebo (n = 7) for 28 days, with off-treatment monitoring for 24 weeks. Endpoints included PK parameters of ATI-2173 and its metabolite clevudine, maximum reduction from baseline in HBV DNA, and safety and tolerability. Treatment-emergent adverse events occurred in eight patients (47%) receiving ATI-2173 and five (71%) receiving placebo; headache was the most common (n = 4). ATI-2173 PK was generally dose proportional. Systemic clevudine exposure with ATI-2173 dosing was substantially reduced compared with historical values observed with clevudine administration. On Day 28, mean changes from baseline in HBV DNA were -2.72 to -2.78 log10 IU/ml with ATI-2173 and +0.17 log10 IU/ml with placebo. Off-treatment sustained viral suppression and decreases in covalently closed circular DNA biomarkers were observed in most patients; one maintained undetectable HBV DNA at 24 weeks off treatment. In this 28-day monotherapy study, ATI-2173 demonstrated safety and antiviral activity, with sustained off-treatment effects and substantially reduced systemic clevudine exposure. These results support evaluation of ATI-2173 with tenofovir disoproxil fumarate in phase 2 studies.
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Affiliation(s)
| | | | - Alina Jucov
- ARENSIA Exploratory Medicine, Republican Clinical Hospital, Chisinau, Moldova.,Department of Infectious Diseases, Nicolae Testemitanu State University of Medicine and Pharmacy, Chisinau, Moldova
| | - Igor Anastasiy
- Department of Infectious Diseases, Nicolae Testemitanu State University of Medicine and Pharmacy, Chisinau, Moldova.,ARENSIA Exploratory Medicine, Kiev, Ukraine
| | - Nelli Ghicavii
- ARENSIA Exploratory Medicine, Republican Clinical Hospital, Chisinau, Moldova
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Safety and efficacy of vebicorvir administered with entecavir in treatment-naïve patients with chronic hepatitis B virus infection. J Hepatol 2022; 77:1265-1275. [PMID: 35697332 DOI: 10.1016/j.jhep.2022.05.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 04/20/2022] [Accepted: 05/17/2022] [Indexed: 12/27/2022]
Abstract
BACKGROUND & AIMS Nucleos(t)ide reverse transcriptase inhibitors do not completely suppress HBV DNA in chronic HBV infection (cHBV). Vebicorvir (VBR) is an investigational core inhibitor that interferes with multiple aspects of HBV replication. This phase II trial evaluated the safety and efficacy of VBR in combination with entecavir (ETV) in treatment-naïve patients with cHBV. METHODS HBeAg-positive, treatment-naïve patients without cirrhosis were randomised 1:1 in a double-blind manner to once-daily VBR 300 mg+ETV 0.5 mg or placebo (PBO)+ETV 0.5 mg for 24 weeks. The primary endpoint was change in mean log10 HBV DNA from Baseline to Week 12 and 24. RESULTS All patients in both treatment groups (PBO+ETV: 12/12; VBR+ETV: 13/13) completed the study. At Week 12, VBR+ETV led to a greater mean (SD) reduction from Baseline in log10 IU/ml HBV DNA (-4.45 [1.03]) vs. PBO+ETV (-3.30 [1.18]; p = 0.0077). At Week 24, VBR+ETV led to a greater reduction from Baseline in log10 IU/ml HBV DNA (-5.33 [1.59]) vs. PBO+ETV (-4.20 [0.98]; p = 0.0084). Greater mean reductions in pregenomic RNA were observed at Week 12 and 24 in patients receiving VBR+ETV vs. PBO+ETV (p <0.0001 and p <0.0001). Changes in viral antigens were similar in both groups. No drug interaction between VBR and ETV was observed. Two patients experienced HBV DNA rebound during treatment, with no resistance breakthrough detected. The safety of VBR+ETV was similar to PBO+ETV. All treatment-emergent adverse events and laboratory abnormalities were Grade 1/2. There were no deaths, serious adverse events, or evidence of drug-induced liver injury. CONCLUSIONS In this 24-week study, VBR+ETV provided additive antiviral activity over PBO+ETV in treatment-naïve patients with cHBV, with a favourable safety and tolerability profile. CLINICAL TRIAL NUMBER NCT03577171 LAY SUMMARY: Hepatitis B is a long-lasting viral infection of the liver. Current treatments can suppress hepatitis B virus but do not offer the opportunity of cure, hence, new treatment approaches are required. Herein, we show that the combination of the novel core inhibitor vebicorvir with an existing antiviral (entecavir) in treatment-naïve patients chronically infected with hepatitis B virus demonstrated greater antiviral activity than entecavir alone. Additionally, vebicorvir was safe and well tolerated. Thus, further studies evaluating its potential role in the treatment of chronic hepatitis B are warranted.
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Hsu PK, Su PY, Wu CL. Analysis of antiviral efficacy after switching from brand to generic entecavir in patients with treatment-naïve chronic hepatitis B. BMC Gastroenterol 2022; 22:228. [PMID: 35538425 PMCID: PMC9088125 DOI: 10.1186/s12876-022-02317-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 05/04/2022] [Indexed: 12/04/2022] Open
Abstract
Background/Aims Entecavir (ETV) can suppress chronic hepatitis B (CHB) virus replication as a standard of treatment drugs. For the treatment of CHB, affordable generic drugs may be more widely used in developing and undeveloped countries. However, there is little real-world data regarding the clinical efficacy of switching from entecavir-brand-name drugs (ETV-Brand) to entecavir generic drugs (ETV-Generic) with 0.5 mg once daily. The aim of the study was to evaluate the antiviral activity and safety of ETV-Generic in comparison to ETV-Brand in CHB-patients. Methods In this single-center, retrospective, 175 treatment-naïve—CHB-patients were assigned to receive 0.5 mg of ETV-Brand per day for a least 2 years and then switched to ETV-Generic for 6 months for analysis. The primary efficacy endpoint was a sustained virological response in comparison of the rate of undetectable serum Hepatitis B deoxyribonucleic acid (HBV DNA) as the sustained virologic response at baseline and 6 months after switching. Secondary efficacy endpoints were the comparison of the alanine aminotransferase (ALT) levels between before and after switching and ALT normalization. Renal safety consideration was reported on changing the estimated glomerular filtration rate. Results From baseline to 6 months, the rate of undetectable HBV DNA and ALT levels remained stable as compared ETV-Brand period with ETV-Generic for 6 months. The rate of undetectable HBV DNA were 81.1%in ETV-Brand versus 88.0%in ETV-Generic (p = 0.05 CI 0.1–13.5%). ALT levels were 27.2 IU/L (CI 24.8–29.6 IU/L) in ETV-Brand versus 26.2 IU/L (CI 24.0–28.4 IU/L) in ETV-Generic (p = 0.55). Both endpoints were not significantly different between ETV-Brand and ETV-Generic treatments. Kidney function did not significantly differ from ETV-Brand (80.8, interquartile range [IQR]: 66.6–95.3 mL/min/1.73 m2) to ETV-Generic treatment period (80.3, IQR: 65.6–93.5 mL/min/1.73 m2). Conclusion In treatment-naïve CHB-patients, the efficacy and safety profiles of switching from ETV-Brand to ETV-Generic showed no difference. Concluding the ETV-Generic comes to exciting virologic responses and rare adverse events. Supplementary Information The online version contains supplementary material available at 10.1186/s12876-022-02317-7.
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Affiliation(s)
- Po-Ke Hsu
- Division of Gastroenterology, Department of Internal Medicine, Changhua Christian Hospital, Changhua, Taiwan.,Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan
| | - Pei-Yuan Su
- Division of Gastroenterology, Department of Internal Medicine, Changhua Christian Hospital, Changhua, Taiwan
| | - Chia-Lin Wu
- School of Medicine, Chung Shan Medical University, Taichung, Taiwan. .,Division of Nephrology, Changhua Christian Hospital, Changhua, Taiwan. .,School of Medicine, National Chung Hsing University, Taichung, Taiwan.
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Colombatto P, Coco B, Bonino F, Brunetto MR. Management and Treatment of Patients with Chronic Hepatitis B: Towards Personalized Medicine. Viruses 2022; 14:701. [PMID: 35458431 PMCID: PMC9027850 DOI: 10.3390/v14040701] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 03/22/2022] [Accepted: 03/23/2022] [Indexed: 02/07/2023] Open
Abstract
The currently available antiviral treatments (Peg-Interferon-α and Nucleos(t)ide Analogues, NA) for chronic hepatitis B (CHB) achieve a functional cure (serum HBsAg and HDV-DNA clearance) of HBV infection in a limited number of patients. Nevertheless, the continuous pharmacological suppression of viral replication by NA halts liver disease progression lowering the risk of HCC development and improving the survival. In the near future, to fully exploit the potential of old and new drugs for HBV treatment a personalized approach to the patients will be required according to an accurate definition of their virologic, immunologic and clinical profile.
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Affiliation(s)
- Piero Colombatto
- Hepatology Unit and Laboratory of Molecular Genetics and Pathology of Hepatitis Viruses, Reference Center of the Tuscany Region for Chronic Liver Disease and Cancer, Department of Medical Specialties, University Hospital of Pisa, Via Paradisa 2, 56124 Pisa, Italy; (P.C.); (B.C.)
| | - Barbara Coco
- Hepatology Unit and Laboratory of Molecular Genetics and Pathology of Hepatitis Viruses, Reference Center of the Tuscany Region for Chronic Liver Disease and Cancer, Department of Medical Specialties, University Hospital of Pisa, Via Paradisa 2, 56124 Pisa, Italy; (P.C.); (B.C.)
| | - Ferruccio Bonino
- Institute of Biostructure and Bioimaging, National Research Council, Via De Amicis 95, 80145 Naples, Italy;
| | - Maurizia R. Brunetto
- Hepatology Unit and Laboratory of Molecular Genetics and Pathology of Hepatitis Viruses, Reference Center of the Tuscany Region for Chronic Liver Disease and Cancer, Department of Medical Specialties, University Hospital of Pisa, Via Paradisa 2, 56124 Pisa, Italy; (P.C.); (B.C.)
- Institute of Biostructure and Bioimaging, National Research Council, Via De Amicis 95, 80145 Naples, Italy;
- Internal Medicine, Department of Clinical and Experimental Medicine, University of Pisa, Via Savi 10, 56127 Pisa, Italy
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Proulx J, Ghaly M, Park IW, Borgmann K. HIV-1-Mediated Acceleration of Oncovirus-Related Non-AIDS-Defining Cancers. Biomedicines 2022; 10:biomedicines10040768. [PMID: 35453518 PMCID: PMC9024568 DOI: 10.3390/biomedicines10040768] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 03/22/2022] [Accepted: 03/22/2022] [Indexed: 11/25/2022] Open
Abstract
With the advent of combination antiretroviral therapy (cART), overall survival has been improved, and the incidence of acquired immunodeficiency syndrome (AIDS)-defining cancers has also been remarkably reduced. However, non-AIDS-defining cancers among human immunodeficiency virus-1 (HIV-1)-associated malignancies have increased significantly so that cancer is the leading cause of death in people living with HIV in certain highly developed countries, such as France. However, it is currently unknown how HIV-1 infection raises oncogenic virus-mediated cancer risks in the HIV-1 and oncogenic virus co-infected patients, and thus elucidation of the molecular mechanisms for how HIV-1 expedites the oncogenic viruses-triggered tumorigenesis in the co-infected hosts is imperative for developing therapeutics to cure or impede the carcinogenesis. Hence, this review is focused on HIV-1 and oncogenic virus co-infection-mediated molecular processes in the acceleration of non-AIDS-defining cancers.
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Gish RG, Asselah T, Squires K, Mayers D. Active site polymerase inhibitor nucleotides (ASPINs): Potential agents for chronic HBV cure regimens. Antivir Chem Chemother 2022; 30:20402066221138705. [PMID: 36423233 PMCID: PMC9703507 DOI: 10.1177/20402066221138705] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 10/06/2022] [Indexed: 10/03/2023] Open
Abstract
Chronic hepatitis B virus (HBV) infection affects 240 to 300 million people worldwide. In the nucleus of infected hepatocytes, the HBV genome is converted to covalently closed circular DNA (cccDNA), which persists and serves as a transcriptional template for viral progeny. Therefore, a long-term cure for chronic HBV infection will require elimination of cccDNA. Although currently available nucleos(t)ide analogues (eg, tenofovir disoproxil fumarate, tenofovir alafenamide, entecavir) effectively control HBV replication, they are seldom curative (functional cure rate ∼10%) and require lifelong treatment for most patients. As such, antiviral agents with novel mechanisms of action are needed. Active site polymerase inhibitor nucleotides (ASPINs) noncompetitively distort the HBV polymerase active site to completely inhibit all polymerase functions, unlike traditional chain-terminating nucleos(t)ide analogues, which only target select polymerase functions and are consumed in the process. Clevudine, a first-generation ASPIN, demonstrated potent and prolonged HBV suppression in phase 2 and 3 clinical studies, but long-term treatment was associated with reversible myopathy in a small number of patients. ATI-2173, a novel next-generation ASPIN, is structurally similar to clevudine but targets the liver and demonstrates potent anti-HBV activity on and off treatment, and may ultimately demonstrate an improved pharmacokinetic and safety profile by significantly reducing systemic clevudine exposure. Thus, ATI-2173 is currently in clinical development as an agent for HBV cure. Here, we review the mechanism of action and preclinical and clinical profiles of clevudine and ATI-2173 to support the role of ASPINs as part of curative regimens for chronic HBV infection.
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Affiliation(s)
- Robert G Gish
- Hepatitis B Foundation, Doylestown, PA, USA
- Robert G. Gish Consultants, LLC, La Jolla, CA, USA
| | - Tarik Asselah
- Université de Paris, Inserm U1149, Centre de Recherche sur l’inflammation, Paris, France
- Department of Hepatology, AP-HP, Hôpital Beaujon, Clichy, France
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10
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Tremblay T, Alcée JB, Giguère D. Protecting-group-free synthesis of clevudine ( l-FMAU), a treatment of the hepatitis B virus. Org Biomol Chem 2022; 20:8859-8863. [DOI: 10.1039/d2ob01814d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A new strategy for the synthesis of unnatural 2′-deoxy-2′-fluoro-l-nucleoside is described.
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Affiliation(s)
- Thomas Tremblay
- Département de Chimie, 1045 av. De la Médecine, Université Laval, Québec City, Qc, Canada G1V 0A6
| | - Jessica B. Alcée
- Département de Chimie, 1045 av. De la Médecine, Université Laval, Québec City, Qc, Canada G1V 0A6
| | - Denis Giguère
- Département de Chimie, 1045 av. De la Médecine, Université Laval, Québec City, Qc, Canada G1V 0A6
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Abstract
Hepatitis B virus (HBV) is a hepatotropic, partially double-stranded DNA virus that replicates by reverse transcription and is a major cause of chronic liver disease and hepatocellular carcinoma. Reverse transcription is catalyzed by the four-domain multifunctional HBV polymerase (P) protein that has protein-priming, RNA- and DNA-dependent DNA synthesis (i.e., reverse transcriptase), and ribonuclease H activities. P also likely promotes the three strand transfers that occur during reverse transcription, and it may participate in immune evasion by HBV. Reverse transcription is primed by a tyrosine residue in the amino-terminal domain of P, and P remains covalently attached to the product DNA throughout reverse transcription. The reverse transcriptase activity of P is the target for the nucleos(t)ide analog drugs that dominate HBV treatment, and P is the target of ongoing efforts to develop new drugs against both the reverse transcriptase and ribonuclease H activities. Despite the unusual reverse transcription pathway catalyzed by P and the importance of P to HBV therapy, understanding the enzymology and structure of HBV P severely lags that of the retroviral reverse transcriptases due to substantial technical challenges to studying the enzyme. Obtaining a better understanding of P will broaden our appreciation of the diversity among reverse transcribing elements in nature, and will help improve treatment for people chronically infected with HBV.
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Affiliation(s)
- Daniel N Clark
- Department of Microbiology, Weber State University, Ogden, UT, United States
| | - Razia Tajwar
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, Saint Louis, MO, United States
| | - Jianming Hu
- Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - John E Tavis
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, Saint Louis, MO, United States.
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Tsai E. Review of Current and Potential Treatments for Chronic Hepatitis B Virus Infection. Gastroenterol Hepatol (N Y) 2021; 17:367-376. [PMID: 34602899 PMCID: PMC8475260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Chronic hepatitis B virus (HBV) infection remains a major global health burden. Millions of people are at risk for complications of chronic HBV infection, despite the widespread availability of an effective prophylactic vaccine. The current available treatments for HBV infection-interferon and nucleos(t)ide analogues-are effective at suppressing viral replication and decreasing the risk of cirrhosis. However, these treatments have a number of limitations, creating the need for alternative therapeutic agents. Recent advances in drug therapy have heralded a new horizon of novel therapeutic approaches for chronic HBV infection, with several promising antiviral and immunomodulatory agents currently in preclinical or clinical testing. This article reviews the current landscape of HBV treatments and highlights the most recent therapeutic strategies designed to directly target HBV or to improve immune response during chronic infection.
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Affiliation(s)
- Eugenia Tsai
- Texas Liver Institute and UT Health San Antonio, San Antonio, Texas
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13
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Shen S, Xie Z, Cai D, Yu X, Zhang H, Kim ES, Zhou B, Hou J, Zhang X, Huang Q, Sun J, Guo H. Biogenesis and molecular characteristics of serum hepatitis B virus RNA. PLoS Pathog 2020; 16:e1008945. [PMID: 33079954 PMCID: PMC7575114 DOI: 10.1371/journal.ppat.1008945] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 08/28/2020] [Indexed: 02/06/2023] Open
Abstract
HBV is an enveloped DNA virus that replicates its DNA genome via reverse transcription of a pregenomic (pg) RNA intermediate in hepatocytes. Interestingly, HBV RNA can be detected in virus-like particles in chronic hepatitis B (CHB) patient serum and has been utilized as a biomarker for intrahepatic cccDNA activity in treated patients. However, the biogenesis and molecular characteristics of serum HBV RNA remain to be fully defined. In this study, we found that the encapsidated serum HBV RNA predominately consists of pgRNA, which are detergent- and ribonuclease-resistant. Through blocking HBV DNA replication without affecting pgRNA encapsidation by using the priming-defective HBV mutant Y63D or 3TC treatment, we demonstrated that the cell culture supernatant contains a large amount of pgRNA-containing nonenveloped capsids and a minor population of pgRNA-containing virions. The formation of pgRNA-virion requires both capsid assembly and viral envelope proteins, which can be inhibited by capsid assembly modulators and an envelope-knockout mutant, respectively. Furthermore, the pgRNA-virion utilizes the multivesicular body pathway for egress, in a similar way as DNA-virion morphogenesis. Northern blotting, RT-PCR, and 3' RACE assays revealed that serum/supernatant HBV pgRNA are mainly spliced and devoid of the 3'-terminal sequences. Furthermore, pgRNA-virion collected from cells treated with a reversible HBV priming inhibitor L-FMAU was unable to establish infection in HepG2-NTCP cells. In summary, serum HBV RNA is secreted in noninfectious virion-like particle as spliced and poly(A)-free pgRNA. Our study will shed light on the molecular biology of serum HBV RNA in HBV life cycle, and aid the development of serum HBV RNA as a novel biomarker for CHB diagnosis and treatment prognosis.
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Affiliation(s)
- Sheng Shen
- Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, United States of America
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
| | - Zhanglian Xie
- Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, United States of America
| | - Dawei Cai
- Assembly Biosciences, Inc., South San Francisco, CA, United States of America
| | - Xiaoyang Yu
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, United States of America
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
| | - Hu Zhang
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, United States of America
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
| | - Elena S. Kim
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, United States of America
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
| | - Bin Zhou
- Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, United States of America
| | - Jinlin Hou
- Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Xiaoyong Zhang
- Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Qi Huang
- Assembly Biosciences, Inc., South San Francisco, CA, United States of America
| | - Jian Sun
- Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Haitao Guo
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, United States of America
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
- Cancer Virology Program, UPMC Hillman Cancer Center, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
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14
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Bak E, Miller JT, Noronha A, Tavis J, Gallicchio E, Murelli RP, Le Grice SFJ. 3,7-Dihydroxytropolones Inhibit Initiation of Hepatitis B Virus Minus-Strand DNA Synthesis. Molecules 2020; 25:molecules25194434. [PMID: 32992516 PMCID: PMC7583054 DOI: 10.3390/molecules25194434] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 09/15/2020] [Accepted: 09/19/2020] [Indexed: 02/07/2023] Open
Abstract
Initiation of protein-primed (-) strand DNA synthesis in hepatitis B virus (HBV) requires interaction of the viral reverse transcriptase with epsilon (ε), a cis-acting regulatory signal located at the 5' terminus of pre-genomic RNA (pgRNA), and several host-encoded chaperone proteins. Binding of the viral polymerase (P protein) to ε is necessary for pgRNA encapsidation and synthesis of a short primer covalently attached to its terminal domain. Although we identified small molecules that recognize HBV ε RNA, these failed to inhibit protein-primed DNA synthesis. However, since initiation of HBV (-) strand DNA synthesis occurs within a complex of viral and host components (e.g., Hsp90, DDX3 and APOBEC3G), we considered an alternative therapeutic strategy of allosteric inhibition by disrupting the initiation complex or modifying its topology. To this end, we show here that 3,7-dihydroxytropolones (3,7-dHTs) can inhibit HBV protein-primed DNA synthesis. Since DNA polymerase activity of a ribonuclease (RNase H)-deficient HBV reverse transcriptase that otherwise retains DNA polymerase function is also abrogated, this eliminates direct involvement of RNase (ribonuclease) H activity of HBV reverse transcriptase and supports the notion that the HBV initiation complex might be therapeutically targeted. Modeling studies also provide a rationale for preferential activity of 3,7-dHTs over structurally related α-hydroxytropolones (α-HTs).
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Affiliation(s)
- Ellen Bak
- Basic Research Laboratory National Cancer Institute, Frederick, MD 21702, USA; (E.B.); (J.T.M.); (A.N.)
| | - Jennifer T. Miller
- Basic Research Laboratory National Cancer Institute, Frederick, MD 21702, USA; (E.B.); (J.T.M.); (A.N.)
| | - Andrea Noronha
- Basic Research Laboratory National Cancer Institute, Frederick, MD 21702, USA; (E.B.); (J.T.M.); (A.N.)
| | - John Tavis
- Department of Molecular Microbiology and Immunology, St. Louis University, St. Louis, MO 63104, USA;
| | - Emilio Gallicchio
- Department of Chemistry, Brooklyn College, The City University of New York, Brooklyn, NY 11210, USA; (E.G.); (R.P.M.)
- PhD Program in Chemistry, The Graduate Center of The City University of New York, New York, NY 10016, USA
- PhD Program in Biochemistry, The Graduate Center of The City University of New York, New York, NY 10016, USA
| | - Ryan P. Murelli
- Department of Chemistry, Brooklyn College, The City University of New York, Brooklyn, NY 11210, USA; (E.G.); (R.P.M.)
- PhD Program in Chemistry, The Graduate Center of The City University of New York, New York, NY 10016, USA
- PhD Program in Biochemistry, The Graduate Center of The City University of New York, New York, NY 10016, USA
| | - Stuart F. J. Le Grice
- Basic Research Laboratory National Cancer Institute, Frederick, MD 21702, USA; (E.B.); (J.T.M.); (A.N.)
- Correspondence:
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15
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Al-Horani RA, Kar S. Potential Anti-SARS-CoV-2 Therapeutics That Target the Post-Entry Stages of the Viral Life Cycle: A Comprehensive Review. Viruses 2020; 12:E1092. [PMID: 32993173 PMCID: PMC7600245 DOI: 10.3390/v12101092] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 09/08/2020] [Accepted: 09/23/2020] [Indexed: 02/06/2023] Open
Abstract
The coronavirus disease-2019 (COVID-19) pandemic continues to challenge health care systems around the world. Scientists and pharmaceutical companies have promptly responded by advancing potential therapeutics into clinical trials at an exponential rate. Initial encouraging results have been realized using remdesivir and dexamethasone. Yet, the research continues so as to identify better clinically relevant therapeutics that act either as prophylactics to prevent the infection or as treatments to limit the severity of COVID-19 and substantially decrease the mortality rate. Previously, we reviewed the potential therapeutics in clinical trials that block the early stage of the viral life cycle. In this review, we summarize potential anti-COVID-19 therapeutics that block/inhibit the post-entry stages of the viral life cycle. The review presents not only the chemical structures and mechanisms of the potential therapeutics under clinical investigation, i.e., listed in clinicaltrials.gov, but it also describes the relevant results of clinical trials. Their anti-inflammatory/immune-modulatory effects are also described. The reviewed therapeutics include small molecules, polypeptides, and monoclonal antibodies. At the molecular level, the therapeutics target viral proteins or processes that facilitate the post-entry stages of the viral infection. Frequent targets are the viral RNA-dependent RNA polymerase (RdRp) and the viral proteases such as papain-like protease (PLpro) and main protease (Mpro). Overall, we aim at presenting up-to-date details of anti-COVID-19 therapeutics so as to catalyze their potential effective use in fighting the pandemic.
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Affiliation(s)
- Rami A. Al-Horani
- Division of Basic Pharmaceutical Sciences, College of Pharmacy, Xavier University of Louisiana, New Orleans, LA 70125, USA;
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16
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Alghamdi AS, Alothmani HS, Mogharbel M, Albiladi H, Babatin M. Clinical Characteristics of Hepatitis B Virus Patients After Switching to Tenofovir Alafenamide Fumarate: A Retrospective Observational Study. Cureus 2020; 12:e10380. [PMID: 33062501 PMCID: PMC7550005 DOI: 10.7759/cureus.10380] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Background Hepatitis B Virus (HBV) continues to be a significant global health problem despite vaccination programs and effective antiviral drugs. Aim Assess tenofovir alafenamide fumarate (TAF) as a new treatment modality in light of the clinical characteristics of HBV patients. Settings and design A real-world observational study Methods and material We collected data of 71 HBV patients and recorded the hepatitis B virus deoxyribonucleic acid (HBV-DNA) plasma levels and biochemistry test results for the alanine aminotransferase (ALT), aspartate aminotransferase (AST), and serum creatinine levels at three time points, including baseline, time of switching to TAF, and six months after switching. Results From the time of switching to TAF till six months later, HBV-DNA plasma levels significantly decreased from 838.61 IU/mL to 16.7 IU/mL (p-value of <0.05). ALT and AST levels dropped from 29.05 U/L to 27 U/L and from 21.34 U/L to 20.7 U/L (p-values 0.328 and 0.410, respectively). Although TAF did not show a statistically significant reduction in the serum levels of AST, ALT, and creatinine, it showed a detectable maintenance level. Conclusions In the evaluated cohort, all clinical characteristics of HBV were maintained six months after switching patients to TAF.
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17
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ATI-2173, a Novel Liver-Targeted Non-Chain-Terminating Nucleotide for Hepatitis B Virus Cure Regimens. Antimicrob Agents Chemother 2020; 64:AAC.00836-20. [PMID: 32540975 PMCID: PMC7449170 DOI: 10.1128/aac.00836-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 06/06/2020] [Indexed: 01/05/2023] Open
Abstract
ATI-2173 is a novel liver-targeted molecule designed to deliver the 5′-monophosphate of clevudine for the treatment of chronic hepatitis B infection. Unlike other nucleos(t)ides, the active clevudine-5′-triphosphate is a noncompetitive, non-chain-terminating inhibitor of hepatitis B virus (HBV) polymerase that delivers prolonged reduction of viremia in both a woodchuck HBV model and in humans for up to 6 months after cessation of treatment. However, long-term clevudine treatment was found to exhibit reversible skeletal myopathy in a small subset of patients and was subsequently discontinued from development. ATI-2173 is a novel liver-targeted molecule designed to deliver the 5′-monophosphate of clevudine for the treatment of chronic hepatitis B infection. Unlike other nucleos(t)ides, the active clevudine-5′-triphosphate is a noncompetitive, non-chain-terminating inhibitor of hepatitis B virus (HBV) polymerase that delivers prolonged reduction of viremia in both a woodchuck HBV model and in humans for up to 6 months after cessation of treatment. However, long-term clevudine treatment was found to exhibit reversible skeletal myopathy in a small subset of patients and was subsequently discontinued from development. ATI-2173 was designed by modifying clevudine with a 5′-phosphoramidate to deliver the 5′-monophosphate to the liver. Bypassing the first phosphorylation step of clevudine, the 5′-monophosphate is converted to the active 5′-triphosphate in the liver. ATI-2173 is a selective inhibitor of HBV with an anti-HBV 50% effective concentration (EC50) of 1.31 nM in primary human hepatocytes, with minimal to no toxicity in hepatocytes, skeletal muscle, liver, kidney, bone marrow, and cardiomyocytes. ATI-2173 activity was decreased by viral polymerase mutations associated with entecavir, lamivudine, and adefovir resistance, but not capsid inhibitor resistance mutations. A single oral dose of ATI-2173 demonstrated 82% hepatic extraction, no food effect, and greatly reduced peripheral exposure of clevudine compared with equimolar oral dosing of clevudine. Despite reduced plasma clevudine exposure, liver concentrations of the 5′-triphosphate were equivalent following ATI-2173 versus clevudine administration. By selectively delivering the 5′-monophosphate to the liver, while retaining the unique anti-HBV activity of the 5′-triphosphate, ATI-2173 may provide an improved pharmacokinetic profile for clinical use, reducing systemic exposure of clevudine and potentially eliminating skeletal myopathy.
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18
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Pierra Rouviere C, Dousson CB, Tavis JE. HBV replication inhibitors. Antiviral Res 2020; 179:104815. [PMID: 32380149 PMCID: PMC7293572 DOI: 10.1016/j.antiviral.2020.104815] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 04/22/2020] [Accepted: 04/28/2020] [Indexed: 12/21/2022]
Abstract
Chronic Hepatitis B Virus infections afflict >250 million people and kill nearly 1 million annually. Current non-curative therapies are dominated by nucleos(t)ide analogs (NAs) that profoundly but incompletely suppress DNA synthesis by the viral reverse transcriptase. Residual HBV replication during NA therapy contributes to maintenance of the critical nuclear reservoir of the HBV genome, the covalently-closed circular DNA, and to ongoing infection of naive cells. Identification of next-generation NAs with improved efficacy and safety profiles, often through novel prodrug approaches, is the primary thrust of ongoing efforts to improve HBV replication inhibitors. Inhibitors of the HBV ribonuclease H, the other viral enzymatic activity essential for viral genomic replication, are in preclinical development. The complexity of HBV's reverse transcription pathway offers many other potential targets. HBV's protein-priming of reverse transcription has been briefly explored as a potential target, as have the host chaperones necessary for function of the HBV reverse transcriptase. Improved inhibitors of HBV reverse transcription would reduce HBV's replication-dependent persistence mechanisms and are therefore expected to become a backbone of future curative combination anti-HBV therapies.
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Affiliation(s)
| | - Cyril B Dousson
- Ai-biopharma, Medicinal Chemistry Department, Montpellier, France.
| | - John E Tavis
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, Saint Louis, MO, USA.
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19
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Xia Y, Liang TJ. Development of Direct-acting Antiviral and Host-targeting Agents for Treatment of Hepatitis B Virus Infection. Gastroenterology 2019; 156:311-324. [PMID: 30243618 PMCID: PMC6340783 DOI: 10.1053/j.gastro.2018.07.057] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 07/13/2018] [Accepted: 07/23/2018] [Indexed: 02/06/2023]
Abstract
Hepatitis B virus (HBV) infection affects approximately 300 million people worldwide. Although antiviral therapies have improved the long-term outcomes, patients often require life-long treatment and there is no cure for HBV infection. New technologies can help us learn more about the pathogenesis of HBV infection and develop therapeutic agents to reduce its burden. We review recent advances in development of direct-acting antiviral and host-targeting agents, some of which have entered clinical trials. We also discuss strategies for unbiased high-throughput screens to identify compounds that inhibit HBV and for repurposing existing drugs.
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Affiliation(s)
- Yuchen Xia
- Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, 20892
| | - T Jake Liang
- Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, 20892.
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20
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Zhang P, Zhai S, Chang J, Guo JT. In Vitro Anti-hepatitis B Virus Activity of 2',3'-Dideoxyguanosine. Virol Sin 2018; 33:538-544. [PMID: 30421112 PMCID: PMC6335223 DOI: 10.1007/s12250-018-0065-7] [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] [Received: 08/05/2018] [Accepted: 10/11/2018] [Indexed: 11/30/2022] Open
Abstract
2',3'-dideoxyguanosine (DoG) has been demonstrated to inhibit duck hepatitis B virus (DHBV) replication in vivo in a duck model of HBV infection. In the current study, the in vitro antiviral effects of DoG on human and animal hepadnaviruses were investigated. Our results showed that DoG effectively inhibited HBV, DHBV, and woodchuck hepatitis virus (WHV) replication in hepatocyte-derived cells in a dose-dependent manner, with 50% effective concentrations (EC50) of 0.3 ± 0.05, 6.82 ± 0.25, and 23.0 ± 1.5 μmol/L, respectively. Similar to other hepadnaviral DNA polymerase inhibitors, DoG did not alter the levels of intracellular viral RNA but induced the accumulation of a less-than-full-length viral RNA species, which was recently demonstrated to be generated by RNase H cleavage of pgRNA. Furthermore, using a transient transfection assay, DoG showed similar antiviral activity against HBV wild-type, 3TC-resistant rtA181V, and adefovir-resistant rtN236T mutants. Our results suggest that DoG has potential as a nucleoside analogue drug with anti-HBV activity.
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Affiliation(s)
- Pinghu Zhang
- Institute of Translational Medicine and Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Yangzhou University, Yangzhou, 225001 China
- Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, PA 18902 USA
- Qinghai Himalayan Experimental Animal Center, Xining, 810006 China
| | - Shuo Zhai
- Institute of Translational Medicine and Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Yangzhou University, Yangzhou, 225001 China
| | - Jinhong Chang
- Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, PA 18902 USA
| | - Ju-Tao Guo
- Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, PA 18902 USA
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21
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Recent progress in potential anti-hepatitis B virus agents: Structural and pharmacological perspectives. Eur J Med Chem 2018; 147:205-217. [DOI: 10.1016/j.ejmech.2018.02.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 01/29/2018] [Accepted: 02/01/2018] [Indexed: 12/13/2022]
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22
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Durantel D. New treatments to reach functional cure: Virological approaches. Best Pract Res Clin Gastroenterol 2017; 31:329-336. [PMID: 28774415 DOI: 10.1016/j.bpg.2017.05.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 05/13/2017] [Indexed: 02/07/2023]
Abstract
Current therapies of chronic hepatitis B (CHB) remain limited to pegylated-interferon-alpha (pegIFN-α) or any of the five approved nucleos(t)ide analogues (NA). If viral suppression can be achieved in the majority of patients with the high-barrier-to-resistance new-generation of NA, i.e. entecavir and tenofovir, HBsAg loss is achieved by PEG-IFN-α and/or NA in only 10% of patients, after a 5-year follow-up. Attempts to improve the response by administering two different NA or a combination of NA and PEG-IFN-α have not provided a dramatic increase in the rate of "functional cure". Because of this and the need of long-term NA administration, there is a renewed interest regarding the understanding of various steps of the HBV replication cycle, as well as specific virus-host cell interactions, in order to define new targets and develop novel drugs. This includes the direct inhibition of several HBV life cycle steps by either entry inhibitors, drugs targeting cccDNA, siRNA targeting viral transcripts, capsid assembly modulators, and approaches targeting the secretion of viral envelope proteins. The addition of one or several new drugs to current therapies should offer the prospect of a markedly improved response to treatments and an increased rate of functional cure. This should lead to a reduced risk of antiviral drug resistance, and to a decreased incidence of cirrhosis and hepatocellular carcinoma (HCC). In this chapter, we review investigational and early clinical efforts regarding the identification and characterization of antiviral targets that are being evaluated for the development of innovative DAA concepts for chronic HBV infections.
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Affiliation(s)
- David Durantel
- INSERM, U1052, Lyon, 69003, France; Cancer Research Center of Lyon (CRCL), Lyon, 69008, France; University of Lyon, UCBL1, UMR_S1052, UCBL, 69008, Lyon, France.
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23
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Clark DN, Jones SA, Hu J. In Vitro Assays for RNA Binding and Protein Priming of Hepatitis B Virus Polymerase. Methods Mol Biol 2017; 1540:157-177. [PMID: 27975315 DOI: 10.1007/978-1-4939-6700-1_13] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The hepatitis B virus (HBV) polymerase synthesizes the viral DNA genome from the pre-genomic RNA (pgRNA) template through reverse transcription. Initiation of viral DNA synthesis is accomplished via a novel protein priming mechanism, so named because the polymerase itself acts as a primer, whereby the initiating nucleotide becomes covalently linked to a tyrosine residue on the viral polymerase. Protein priming, in turn, depends on specific recognition of the packaging signal on pgRNA called epsilon. These early events in viral DNA synthesis can now be dissected in vitro as described here.The polymerase is expressed in mammalian cells and purified by immunoprecipitation. The purified protein is associated with host cell factors, is enzymatically active, and its priming activity is epsilon dependent. A minimal epsilon RNA construct from pgRNA is co-expressed with the polymerase in cells. This RNA binds to and co-immunoprecipitates with the polymerase. Modifications can be made to either the epsilon RNA or the polymerase protein by manipulating the expression plasmids. Also, the priming reaction itself can be modified to assay for the initiation or subsequent DNA synthesis during protein priming, the susceptibility of the polymerase to chemical inhibitors, and the precise identification of the DNA products upon their release from the polymerase. The identity of associated host factors can also be evaluated. This protocol closely mirrors our current understanding of the RNA binding and protein priming steps of the HBV replication cycle, and it is amenable to modification. It should therefore facilitate both basic research and drug discovery.
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Affiliation(s)
- Daniel N Clark
- Department of Microbiology and Immunology-H107, The Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA, 17033, USA.
| | - Scott A Jones
- Department of Microbiology and Immunology-H107, The Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA, 17033, USA
- Nevada Division of Public and Behavioral Health, Primary Care Office, 4150 Technology Way, Suite 104, Carson City, NV, 89706, USA
| | - Jianming Hu
- Department of Microbiology and Immunology-H107, The Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA, 17033, USA
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24
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Menéndez-Arias L, Sebastián-Martín A, Álvarez M. Viral reverse transcriptases. Virus Res 2016; 234:153-176. [PMID: 28043823 DOI: 10.1016/j.virusres.2016.12.019] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 12/19/2016] [Accepted: 12/24/2016] [Indexed: 12/11/2022]
Abstract
Reverse transcriptases (RTs) play a major role in the replication of Retroviridae, Metaviridae, Pseudoviridae, Hepadnaviridae and Caulimoviridae. RTs are enzymes that are able to synthesize DNA using RNA or DNA as templates (DNA polymerase activity), and degrade RNA when forming RNA/DNA hybrids (ribonuclease H activity). In retroviruses and LTR retrotransposons (Metaviridae and Pseudoviridae), the coordinated action of both enzymatic activities converts single-stranded RNA into a double-stranded DNA that is flanked by identical sequences known as long terminal repeats (LTRs). RTs of retroviruses and LTR retrotransposons are active as monomers (e.g. murine leukemia virus RT), homodimers (e.g. Ty3 RT) or heterodimers (e.g. human immunodeficiency virus type 1 (HIV-1) RT). RTs lack proofreading activity and display high intrinsic error rates. Besides, high recombination rates observed in retroviruses are promoted by poor processivity that causes template switching, a hallmark of reverse transcription. HIV-1 RT inhibitors acting on its polymerase activity constitute the backbone of current antiretroviral therapies, although novel drugs, including ribonuclease H inhibitors, are still necessary to fight HIV infections. In Hepadnaviridae and Caulimoviridae, reverse transcription leads to the formation of nicked circular DNAs that will be converted into episomal DNA in the host cell nucleus. Structural and biochemical information on their polymerases is limited, although several drugs inhibiting HIV-1 RT are known to be effective against the human hepatitis B virus polymerase. In this review, we summarize current knowledge on reverse transcription in the five virus families and discuss available biochemical and structural information on RTs, including their biosynthesis, enzymatic activities, and potential inhibition.
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Affiliation(s)
- Luis Menéndez-Arias
- Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, c/Nicolás Cabrera, 1, Campus de Cantoblanco, 28049 Madrid, Spain.
| | - Alba Sebastián-Martín
- Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, c/Nicolás Cabrera, 1, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Mar Álvarez
- Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, c/Nicolás Cabrera, 1, Campus de Cantoblanco, 28049 Madrid, Spain
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25
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Zhang P, Liu F, Guo F, Zhao Q, Chang J, Guo JT. Characterization of novel hepadnaviral RNA species accumulated in hepatoma cells treated with viral DNA polymerase inhibitors. Antiviral Res 2016; 131:40-8. [PMID: 27083116 DOI: 10.1016/j.antiviral.2016.04.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 04/07/2016] [Accepted: 04/10/2016] [Indexed: 12/21/2022]
Abstract
Inhibitors of hepadnaviral DNA polymerases are predicted to inhibit both minus and plus strand of viral DNA synthesis and arrest viral DNA replication at the stage of pregenomic (pg) RNA-containing nucleocapsids. However, analyses of the RNA species of human and duck hepatitis B viruses (HBV and DHBV, respectively) in hepatoma cells treated with viral DNA polymerase inhibitors revealed the genesis of novel RNA species migrating slightly faster than the full-length pgRNA. The DNA polymerase inhibitor-induced accumulation of these RNA species were abolished in the presence of alpha-interferon or HBV nucleocapsid assembly inhibitors. Moreover, they were protected from microccocal nuclease digestion and devoid of a poly-A tail. These characteristics suggest that the novel RNA species are most likely generated from RNase H cleavage of encapsidated pgRNA, after primer translocation and synthesis of the 5' terminal portion of minus strand DNA. In support of this hypothesis, DNA polymerase inhibitor treatment of chicken hepatoma cells transfected with a DHBV genome encoding an RNase H inactive DNA polymerase (E696H) failed to produce such RNA species. Our results thus suggest that the currently available DNA polymerase inhibitors do not efficiently arrest minus strand DNA synthesis at the early stage in hepatocytes. Hence, development of novel antiviral agents that more potently suppress viral DNA synthesis or viral nucleocapsid assembly inhibitors that are mechanistically complementary to the currently available DNA polymerase inhibitors are warranted.
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Affiliation(s)
- Pinghu Zhang
- Jiangsu Key Laboratory of New Drug Screening & Jiangsu Center for Pharmacodynamics Research and Evaluation & State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009, China; Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, PA, USA
| | - Fei Liu
- Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, PA, USA
| | - Fang Guo
- Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, PA, USA
| | - Qiong Zhao
- Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, PA, USA
| | - Jinhong Chang
- Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, PA, USA
| | - Ju-Tao Guo
- Baruch S. Blumberg Institute, Hepatitis B Foundation, Doylestown, PA, USA.
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Zhou Y, Wang J, Gu Z, Wang S, Zhu W, Aceña JL, Soloshonok VA, Izawa K, Liu H. Next Generation of Fluorine-Containing Pharmaceuticals, Compounds Currently in Phase II-III Clinical Trials of Major Pharmaceutical Companies: New Structural Trends and Therapeutic Areas. Chem Rev 2016; 116:422-518. [PMID: 26756377 DOI: 10.1021/acs.chemrev.5b00392] [Citation(s) in RCA: 1797] [Impact Index Per Article: 224.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Yu Zhou
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zu Chong Zhi Road, Shanghai 201203, China
| | - Jiang Wang
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zu Chong Zhi Road, Shanghai 201203, China
| | - Zhanni Gu
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zu Chong Zhi Road, Shanghai 201203, China
| | - Shuni Wang
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zu Chong Zhi Road, Shanghai 201203, China
| | - Wei Zhu
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zu Chong Zhi Road, Shanghai 201203, China
| | - José Luis Aceña
- Department of Organic Chemistry I, Faculty of Chemistry, University of the Basque Country UPV/EHU , Paseo Manuel Lardizábal 3, 20018 San Sebastián, Spain.,Department of Organic Chemistry, Autónoma University of Madrid , Cantoblanco, 28049 Madrid, Spain
| | - Vadim A Soloshonok
- Department of Organic Chemistry I, Faculty of Chemistry, University of the Basque Country UPV/EHU , Paseo Manuel Lardizábal 3, 20018 San Sebastián, Spain.,IKERBASQUE, Basque Foundation for Science, María Díaz de Haro 3, 48013 Bilbao, Spain
| | - Kunisuke Izawa
- Hamari Chemicals Ltd., 1-4-29 Kunijima, Higashi-Yodogawa-ku, Osaka, Japan 533-0024
| | - Hong Liu
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zu Chong Zhi Road, Shanghai 201203, China
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27
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Cheng Z, Zhi X, Sun G, Guo W, Huang Y, Sun W, Tian X, Zhao F, Hu K. Sodium selenite suppresses hepatitis B virus transcription and replication in human hepatoma cell lines. J Med Virol 2015; 88:653-63. [PMID: 26331371 PMCID: PMC7167125 DOI: 10.1002/jmv.24366] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2015] [Indexed: 12/30/2022]
Abstract
Hepatitis B virus (HBV) infection is one of the most serious and prevalent health problems worldwide. Current anti‐HBV medications have a number of drawbacks, such as adverse effects and drug resistance; thus, novel potential anti‐HBV reagents are needed. Selenium (Se) has been shown to be involved in both human immunodeficiency virus and hepatitis C virus infections, but its role in HBV infection remains unclear. To address this, sodium selenite (Na2SeO3) was applied to three HBV cell models: HepG2.2.15 cells, and HuH‐7 cells transfected with either 1.1 or 1.3× HBV plasmids. Cytotoxicity of Na2SeO3 was examined by Cell Counting Kit‐8. Levels of viral antigen expression, transcripts, and encapsidated viral DNA were measured by enzyme‐linked immunosorbent assay, northern blot, and Southern blot, respectively. There was no obvious cytotoxicity in either HepG2.2.15 or HuH‐7 cells with <2.5 µM Na2SeO3. Below this concentration, Na2SeO3 suppressed HBsAg and HBeAg production, HBV transcript level, and amount of genomic DNA in all three tested models, and suppression level was enhanced in line with increases in Na2SeO3 concentration or treatment time. Moreover, the inhibitory effect of Na2SeO3 on HBV replication can be further enhanced by combined treatment with lamivudine, entecavir, or adefovir. Thus, the present study clearly proves that Na2SeO3 suppresses HBV protein expression, transcription, and genome replication in hepatoma cell models in a dose‐ and time‐dependent manner. J. Med. Virol. 88:653–663, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Zhikui Cheng
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Xiaoguang Zhi
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Ge Sun
- Sino-Germany Biomedical Center, Hubei University of Technology, Wuhan, 430068, China
| | - Wei Guo
- Department of Infectious Disease and Institute of Infectious Disease, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, Tongji, China
| | - Yayun Huang
- Sino-Germany Biomedical Center, Hubei University of Technology, Wuhan, 430068, China
| | - Weihua Sun
- Sino-Germany Biomedical Center, Hubei University of Technology, Wuhan, 430068, China
| | - Xiaohui Tian
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Fei Zhao
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Kanghong Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China.,Sino-Germany Biomedical Center, Hubei University of Technology, Wuhan, 430068, China
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Clark DN, Hu J. Hepatitis B virus reverse transcriptase - Target of current antiviral therapy and future drug development. Antiviral Res 2015; 123:132-7. [PMID: 26408354 DOI: 10.1016/j.antiviral.2015.09.011] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 09/09/2015] [Accepted: 09/21/2015] [Indexed: 02/07/2023]
Abstract
Hepatitis B virus (HBV) infections rely on the proper functioning of the viral polymerase enzyme, a specialized reverse transcriptase (RT) with multiple activities. All currently approved antiviral drugs for the treatment of chronic HBV infection, except for interferon, target the RT and belong to the same chemical class - they are all nucleoside analogs. Viral DNA synthesis is carried out by the RT enzyme in several different steps, each with distinct RT conformational requirements. In principle, each stage may be targeted by distinct antiviral drugs. In particular, the HBV RT has the unique ability to initiate viral DNA synthesis using itself as a protein primer in a novel protein priming reaction. In order to help identify RT inhibitors and study their mechanisms of action, a number of experimental systems have been developed, each varying in its ability to dissect the protein priming stage and subsequent stages of viral DNA synthesis at the molecular level. Two of the most effective drugs to date, entecavir and tenofovir, can inhibit both the protein priming and the subsequent DNA elongation stages of HBV DNA synthesis. Interestingly, clevudine, a thymidine analog, can inhibit both protein priming and DNA elongation in a non-competitive manner and without being incorporated into the viral DNA. Thus, a nucleoside RT inhibitor (NRTI) can functionally mimic a non-NRTI (NNRTI) in its inhibition of the HBV RT. Therefore, novel NRTIs as well as NNRTIs may be developed to inhibit the DNA synthesis activity of the HBV RT. Furthermore, additional activities of the RT that are also essential to HBV replication, including specific recognition of the viral RNA and its packaging into viral nucleocapsids, may be exploited for antiviral development. To achieve a more potent inhibition of viral replication and ultimately cure chronic HBV infection, the next generation of anti-HBV therapies will likely need to include NRTIs, NNRTIs, and other agents that target the viral RT as well as other viral and host factors in various combinations. This article forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for hepatitis B."
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Affiliation(s)
- Daniel N Clark
- Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, United States.
| | - Jianming Hu
- Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, United States
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29
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Hu J, Seeger C. Hepadnavirus Genome Replication and Persistence. Cold Spring Harb Perspect Med 2015; 5:a021386. [PMID: 26134841 DOI: 10.1101/cshperspect.a021386] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Hallmarks of the hepadnavirus replication cycle are the formation of covalently closed circular DNA (cccDNA) and the reverse transcription of a pregenomic RNA (pgRNA) in core particles leading to synthesis of the relaxed circular DNA (rcDNA) genome. cccDNA, the template for viral RNA transcription, is the basis for the persistence of these viruses in infected hepatocytes. In this review, we summarize the current state of knowledge on the mechanisms of hepadnavirus reverse transcription and the biochemical and structural properties of the viral reverse transcriptase (RT). We highlight important gaps in knowledge regarding cccDNA biosynthesis and stability. In addition, we discuss the impact of current antiviral therapies on viral persistence, particularly on cccDNA.
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Affiliation(s)
- Jianming Hu
- Department of Microbiology and Immunology, Penn State University College of Medicine, Hershey, Pennsylvania 17033
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30
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Abstract
Infection with HBV is common worldwide, with over 350 million chronic carriers. Chronic HBV infection is associated with cirrhosis and hepatocellular carcinoma. All currently available oral antivirals are directed against the HBV polymerase enzyme, a reverse transcriptase. HBV polymerase contains several important domains and motifs which define its functions and reveal ways to further target it. This enzyme executes many functions required for the HBV replication cycle, including viral RNA binding, RNA packaging, protein priming, template switching, DNA synthesis and RNA degradation. In addition, HBV polymerase must interact with host proteins for its functions. Future therapeutics may inhibit not only the DNA synthesis steps which are carried out by the reverse transcriptase domain (as all current antivirals do) but other domains, functions and interactions which are essential to the HBV replication cycle.
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Affiliation(s)
- Daniel N Clark
- The Pennsylvania State University College of Medicine, Milton S Hershey Medical Center, PA 17033, USA
| | - Jianming Hu
- The Pennsylvania State University College of Medicine, Milton S Hershey Medical Center, PA 17033, USA
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31
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Geipel A, Seiz PL, Niekamp H, Neumann-Fraune M, Zhang K, Kaiser R, Protzer U, Gerlich WH, Glebe D. Entecavir allows an unexpectedly high residual replication of HBV mutants resistant to lamivudine. Antivir Ther 2015; 20:779-87. [PMID: 25560463 DOI: 10.3851/imp2928] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2014] [Indexed: 01/25/2023]
Abstract
BACKGROUND Entecavir is an efficient inhibitor of HBV reverse transcriptase (RT) and widely used for therapy of chronic hepatitis B. Entecavir treatment of HBV patients with lamivudine-resistant viral strains, however, often fails, but the mechanism of cross-resistance development is not fully understood. METHODS Using non-linear regression models, dose-response curves of cloned HBV strains from patients pre-treated with RT inhibitors were established in human hepatoma cell lines after transfection with HBV genomes containing HBV polymerase genes from patient isolates. 50% and 90% inhibitory concentrations (IC50 and IC90) and corresponding antiviral resistance factors (RF50 and RF90) were calculated. RESULTS The entecavir dose-response curve of lamivudine-resistant HBV RT mutants rtM204 for the replication of HBV decreased less than expected with increasing drug dose. Remarkably, due to the flat dose-response curves, RF90 values against entecavir of samples with rtM204 substitutions were up to 30× higher than their RF50 values. CONCLUSIONS The unexpectedly high IC90 indicates a strong residual replication capacity of lamivudine-resistant HBV rtM204 variants under entecavir therapy, although IC50 values are initially within the therapeutic range of entecavir. This characteristic favours rapid selection of additional mutants with overt resistance against entecavir. Thus, the current phenotypic resistance assays should include determination of IC90.
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Affiliation(s)
- Andreas Geipel
- Institute of Medical Virology, Justus Liebig University Giessen, National Reference Center for Hepatitis B and D Viruses, Biomedical Research Center Seltersberg, Giessen, Germany
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Nucleoside/nucleotide analog inhibitors of hepatitis B virus polymerase: mechanism of action and resistance. Curr Opin Virol 2014; 8:1-9. [PMID: 24814823 DOI: 10.1016/j.coviro.2014.04.005] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 04/14/2014] [Accepted: 04/16/2014] [Indexed: 02/07/2023]
Abstract
Hepatitis B virus (HBV) polymerase and human immunodeficiency virus (HIV) reverse transcriptase are structurally related. However, the HBV enzyme has a protein priming activity absent in the HIV enzyme. Approved nucleoside/nucleotide inhibitors of the HBV polymerase include lamivudine, adefovir, telbivudine, entecavir and tenofovir. Although most of them target DNA elongation, guanosine and adenosine analogs (e.g. entecavir and tenofovir, respectively) also impair protein priming. Major mutational patterns conferring nucleoside/nucleotide analog resistance include the combinations rtL180M/rtM204(I/V) (for lamivudine, entecavir, telbivudine and clevudine) and rtA181V/rtN236T (for adefovir and tenofovir). However, development of drug resistance is very slow for entecavir and tenofovir. Novel nucleoside/nucleotide analogs in advanced clinical trials include phosphonates similar to adefovir or tenofovir, and new tenofovir derivatives with improved pharmacological properties.
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33
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Comparative analysis of hepatitis B virus polymerase sequences required for viral RNA binding, RNA packaging, and protein priming. J Virol 2013; 88:1564-72. [PMID: 24227865 DOI: 10.1128/jvi.02852-13] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Hepatitis B virus replicates a DNA genome through reverse transcription of a pregenomic RNA (pgRNA) by using a multifunctional polymerase (HP). A critical function of HP is its specific association with a viral RNA signal, termed ε (Hε), located on pgRNA, which is required for specific packaging of pgRNA into viral nucleocapsids and initiation of viral reverse transcription. HP initiates reverse transcription by using itself as a protein primer (protein priming) and Hε as the obligatory template. HP is made up of four domains, including the terminal protein (TP), the spacer, the reverse transcriptase (RT), and the RNase H domains. A recently developed, Hε-dependent, in vitro protein priming assay was used in this study to demonstrate that almost the entire TP and RT domains and most of the RNase H domain were required for protein priming. Specific residues within TP, RT, and the spacer were identified as being critical for HP-Hε binding and/or protein priming. Comparison of HP sequence requirements for Hε binding, pgRNA packaging, and protein priming allowed the classification of the HP mutants into five groups, each with distinct effects on these complex and related processes. Detailed characterization of HP requirements for these related and essential functions of HP will further elucidate the mechanisms of its multiple functions and aid in the targeting of these functions for antiviral therapy.
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Jones SA, Hu J. Hepatitis B virus reverse transcriptase: diverse functions as classical and emerging targets for antiviral intervention. Emerg Microbes Infect 2013; 2:e56. [PMID: 26038488 PMCID: PMC3820986 DOI: 10.1038/emi.2013.56] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 07/21/2013] [Indexed: 12/12/2022]
Abstract
Hepatitis B virus (HBV) infection remains a global health problem with over 350 million chronically infected, causing an increased risk of cirrhosis and hepatocellular carcinoma. Current antiviral chemotherapy for HBV infection include five nucleos(t)ide analog reverse transcriptase inhibitors (NRTIs) that all target one enzymatic activity, DNA strand elongation, of the HBV polymerase (HP), a specialized reverse transcriptase (RT). NRTIs are not curative and long-term treatment is associated with toxicity and the emergence of drug resistant viral mutations, which can also result in vaccine escape. Recent studies on the multiple functions of HP have provided important mechanistic insights into its diverse roles during different stages of viral replication, including interactions with viral pregenomic RNA, RNA packaging into nucleocapsids, protein priming, minus- and plus-strand viral DNA synthesis, RNase H-mediated degradation of viral RNA, as well as critical host interactions that regulate the multiple HP functions. These diverse functions provide ample opportunities to develop novel HP-targeted antiviral treatments that should contribute to curing chronic HBV infection.
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Affiliation(s)
- Scott A Jones
- Department of Microbiology and Immunology, The Penn State University College of Medicine, Hershey , PA 17033, USA
| | - Jianming Hu
- Department of Microbiology and Immunology, The Penn State University College of Medicine, Hershey , PA 17033, USA
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