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Cuypers L, Snoeck J, Kerremans L, Libin P, Crabbé R, Van Dooren S, Vuagniaux G, Vandamme AM. HCV1b genome evolution under selective pressure of the cyclophilin inhibitor alisporivir during the DEB-025-HCV-203 phase II clinical trial. Infect Genet Evol 2016; 44:169-181. [PMID: 27374748 DOI: 10.1016/j.meegid.2016.06.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 06/24/2016] [Accepted: 06/27/2016] [Indexed: 12/18/2022]
Abstract
Major advances have revolutionized the HCV antiviral treatment field, with interferon-free combinations of direct-acting antivirals (DAAs) resulting into success rates of >90% for all HCV genotypes. Nevertheless, viral eradication at a global level stills remains challenging, stimulating the continued search for new affordable pan-genotypic drugs. To overcome selection of drug resistant variants, targeting host proteins can be an attractive mechanism of action. Alisporivir (Debio 025) is a potent pan-genotypic host-targeting antiviral agent, acting on cyclophilin A, which is necessary for HCV replication. The efficacy and safety of three different oral doses of alisporivir in combination with pegylated interferon-α2a given over a period of four weeks, was investigated in a randomized, double-blind and placebo-controlled phase IIa clinical trial, in 90 treatment-naïve subjects infected with chronic hepatitis C, wherefrom 58 HCV1b samples were selected for genetic sequencing purposes. Sequencing results were used to study the HCV genome for amino acid changes potentially related with selective pressure and resistance to alisporivir. By comparing baseline and on-treatment sequences, a large variation in proportion of amino acid changes was detected in all treatment arms. The NS5A variant D320E, which was previously identified during in vitro resistance selection and resulted in 3.6-fold reduced alisporivir susceptibility, emerged in two subjects in the alisporivir monotherapy arm. However, emergence of D320E appeared to be associated only with concurrent viral load rebound in one subject with 0.8log10IU/ml increase in HCV RNA. In general, for all datasets, low numbers of positions under positive selective pressure were observed, with no significant differences between naïve and treated sequences. Additionally, incomplete sequence information for some of the 22 patients and the low number of individuals per treatment arm, is limiting the power to assess the association of alisporivir or interferon treatment with the observed amino acid changes.
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Affiliation(s)
- Lize Cuypers
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Minderbroedersstraat 10, 3000 Leuven, Belgium.
| | - Joke Snoeck
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Minderbroedersstraat 10, 3000 Leuven, Belgium.
| | - Lien Kerremans
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Minderbroedersstraat 10, 3000 Leuven, Belgium.
| | - Pieter Libin
- Artificial Intelligence Lab, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium; KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Minderbroedersstraat 10, 3000 Leuven, Belgium.
| | - Raf Crabbé
- Debiopharm International S.A., Che. Messidor 5-7, P.O. Box 5911, 1002 Lausanne, Switzerland.
| | - Sonia Van Dooren
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Minderbroedersstraat 10, 3000 Leuven, Belgium.
| | - Grégoire Vuagniaux
- Debiopharm International S.A., Che. Messidor 5-7, P.O. Box 5911, 1002 Lausanne, Switzerland.
| | - Anne-Mieke Vandamme
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Minderbroedersstraat 10, 3000 Leuven, Belgium; Center for Global Health and Tropical Medicine, Unidade de Microbiologia, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Jungquiera 100, 1349-008 Lisbon, Portugal.
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Abstract
For many years, the standard of treatment for hepatitis C virus (HCV) infection was a combination of pegylated interferon alpha (Peg-IFN-α) and ribavirin for 24–48 weeks. This treatment regimen results in a sustained virologic response (SVR) rate in about 50 % of cases. The failure of IFN-α-based therapy to eliminate HCV is a result of multiple factors including a suboptimal treatment regimen, severity of HCV-related diseases, host factors and viral factors. In recent years, advances in HCV cell culture have contributed to a better understanding of the viral life cycle, which has led to the development of a number of direct-acting antiviral agents (DAAs) that target specific key components of viral replication, such as HCV NS3/4A, HCV NS5A, and HCV NS5B proteins. To date, several new drugs have been approved for the treatment of HCV infection. Application of DAAs with IFN-based or IFN-free regimens has increased the SVR rate up to >90 % and has allowed treatment duration to be shortened to 12–24 weeks. The impact of HCV proteins in response to IFN-based and IFN-free therapies has been described in many reports. This review summarizes and updates knowledge on molecular mechanisms of HCV proteins involved in anti-IFN activity as well as examining amino acid variations and mutations in several regions of HCV proteins associated with the response to IFN-based therapy and pattern of resistance associated amino acid variants (RAV) to antiviral agents.
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Affiliation(s)
- Kattareeya Kumthip
- Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand.
| | - Niwat Maneekarn
- Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand.
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Chusri P, Kumthip K, Pantip C, Thongsawat S, O'Brien A, Maneekarn N. Influence of amino acid variations in the NS3, NS4A and NS4B of HCV genotypes 1a, 1b, 3a, 3b and 6f on the response to pegylated interferon and ribavirin combination therapy. Virus Res 2014; 196:37-43. [PMID: 25445343 DOI: 10.1016/j.virusres.2014.11.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 10/21/2014] [Accepted: 11/04/2014] [Indexed: 02/05/2023]
Abstract
BACKGROUND It has been suggested that HCV proteins, core, NS3/4A, NS4B, and NS5A, contribute to the resistance of HCV to IFN and ribavirin (RBV) treatments. AIM To assess the effects of HCV amino acid variations in NS3, NS4A and NS4B of HCV subtypes 1a, 1b, 3a, 3b and 6f on the response to pegylated interferon (Peg-IFN) and RBV therapy. METHODS One hundred and thirty four HCV isolates of genotypes 1a, 1b, 3a, 3b and 6f obtained from HCV patients both before and at week 4 of treatments were evaluated. Amino acid sequences of NS3, NS4A and NS4B were analyzed and in compared to reference sequences of corresponding genotypes. RESULTS The data revealed that amino acid variations within the full-length NS3, protease and helicase domains of NS3 of HCV 1a from responders were significantly higher than those from treatment failure groups as compared to reference sequences of each corresponding genotype. Similar results were observed in the full-length and helicase domain but not in the protease domain of HCV 1b. However, the number of amino acid variations in NS3 of HCV 3a, 3b and 6f as well as in NS4A and NS4B showed no difference between the viruses from responders and treatment failure group. Analysis of amino acid variations both before and at week 4 of treatment revealed that the mean number of amino acid variation in the full-length NS3 of HCV 3a and 3b from responders were also significantly higher than those from the treatment failure group. CONCLUSION Our study suggests that the increase of amino acid variations within the NS3 protein of HCV 1a, 1b, 3a and 3b were associated with the response to Peg-IFN and RBV treatment in Thai patients.
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Affiliation(s)
- Pattranuch Chusri
- Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Kattareeya Kumthip
- Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Chansom Pantip
- Research Institute for Health Sciences, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Satawat Thongsawat
- Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Amornrat O'Brien
- Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Niwat Maneekarn
- Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
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Welker MW, Susser S, Welsch C, Perner D, Füller C, Kronenberger B, Herrmann E, Zeuzem S, Sarrazin C. Modulation of replication efficacy of the hepatitis C virus replicon Con1 by site-directed mutagenesis of an NS4B aminoterminal basic leucine zipper. J Viral Hepat 2012; 19:775-83. [PMID: 23043384 DOI: 10.1111/j.1365-2893.2012.01605.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The hepatitis C virus (HCV) nonstructural protein 4B (NS4B) is assumed to function as a membrane anchor and protein hub for the viral replication complex. The aim of the current work was to modulate HCV replication efficacy in the subgenomic Con1 replicon by mutations of specific sites within the aminoterminal-located basic leucine zipper (bZIP), a candidate motif for protein-protein interactions involving NS4B. Mutational sites and amino acid substitutes were determined by in-silico sequence analyses of the NS4B-bZIP motif in 357 isolates of HCV genotype 1b from the euHCVdB and LosAlamos database and consecutive analysis of conserved physico-chemical properties at bZIP specific positions. Mutants with predicted minor, medium or major reduction of replication efficacy were tested in the pFKI389neo/NS3-3'/ET plasmid replicon model. Four sites (L25, T29, V39 and W43) of crucial importance for bZIP-mediated protein interaction with predicted apolarity of respective amino acid positions were selected for mutational studies. Substitutes with physico-chemical properties matching the predicted requirements either well (T29A), moderately (L25W, V39W), or insufficiently (T29E, W43E) were associated with slightly improved, moderate and marked decreased replication efficacy, respectively. Spontaneous (T29G) and adaptive (A28G, E40G) mutations occurred in the T29E mutation isolate only and were associated with marked reduction of replication efficacy. The bZIP motif region of NS4B is crucial for RNA replication in the subgenomic Con1 replicon system. RNA replication efficacy can be modulated by site-directed mutagenesis at specific bZIP functional sites. New adaptive amino acid mutations were identified within the HCV NS4B protein.
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Affiliation(s)
- M-W Welker
- Klinikum der Johann Wolfgang Goethe-Universität, Medizinische Klinik, Theodor-Stern-Kai, Frankfurt am Main, Germany
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Toyoda H, Kumada T, Kiriyama S, Tanikawa M, Hisanaga Y, Kanamori A, Tada T, Arakawa T, Fujimori M, Niinomi T, Ando N, Yasuda S, Sakai K, Kimura J. High ability to predict the treatment outcome of peginterferon and ribavirin combination therapy based on the reduction in HCV RNA levels at 4 weeks after starting therapy and amino acid substitutions in the hepatitis C virus in patients infected with HCV genotype 1b. J Gastroenterol 2011; 46:501-9. [PMID: 20927636 DOI: 10.1007/s00535-010-0328-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 09/08/2010] [Indexed: 02/04/2023]
Abstract
BACKGROUND The ability to predict the outcome of peginterferon (PEG-IFN) and ribavirin combination therapy based on the reduction in hepatitis C virus (HCV) RNA levels at 4 weeks after starting the therapy and amino acid substitutions in HCV was to be confirmed. METHODS We measured the reduction in HCV RNA levels at 4 weeks after starting the combination therapy, as well as examining amino acid substitutions at residue 70 in the HCV core and within the interferon sensitivity-determining region (ISDR) of HCV non-structural protein 5A (NS5A), for 101 patients infected with HCV genotype 1b. The ability of these factors to predict a sustained virologic response (SVR) was analyzed. RESULTS When a 3 log(10) reduction in HCV RNA levels at 4 weeks after starting therapy was set as the cut-off value, an SVR was achieved in 37 of the 46 patients (80.4%) with a ≥3 log(10) decrease and in 4 of the 55 patients (7.3%) with a <3 log(10) decrease. All 4 patients who achieved an SVR despite a <3 log(10) reduction in HCV RNA levels at 4 weeks had an arginine at residue 70 in the HCV core and a non-wild-type sequence for the ISDR of HCV NS5A. CONCLUSION A ≥3 log(10) reduction in HCV RNA levels at 4 weeks after starting therapy indicates that a patient has a high likelihood of achieving an SVR as a final outcome. Additional information on the amino acid substitutions at residue 70 in the HCV core and within NS5A-ISDR will further increase the ability to predict a clinical response.
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El-Shamy A, Kim SR, Ide YH, Sasase N, Imoto S, Deng L, Shoji I, Hotta H. Polymorphisms of hepatitis C virus non-structural protein 5A and core protein and clinical outcome of pegylated-interferon/ribavirin combination therapy. Intervirology 2011; 55:1-11. [PMID: 21293098 DOI: 10.1159/000322219] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 10/14/2010] [Indexed: 12/21/2022] Open
Abstract
OBJECTIVE Hepatitis C virus (HCV genome) polymorphisms are thought to influence the outcome of pegylated-interferon/ribavirin (PEG-IFN/RBV) therapy. This study aimed to examine non-structural protein 5A (NS5A) polymorphisms, e.g. IFN/RBV resistance-determining region (IRRDR) and IFN sensitivity-determining region (ISDR), and core protein polymorphism as predictive therapeutic markers. METHODS Pretreatment sequences of NS5A and core regions were analyzed in 68 HCV-1b-infected patients treated with PEG-IFN/RBV. RESULTS Of 24 patients infected withHCV having an IRRDR with 6 or more mutations (IRRDR≥6), 18 (75%) patients achieved sustained virological response (SVR), whereas only 11 (25%) of 44 patients infected with HCV having IRRDR≤5 did. IRRDR≥6 was significantly associated with SVR (p < 0.0001). On the other hand, ISDR≥2 was significantly associated with relapse (either before [breakthrough] or after end-of-treatment response [ETR[-]relapse]) (p < 0.05) and a point mutation of the core protein from Arg to Gln at position 70 (Gln(70)) was significantly associated with null-response (p < 0.05). Multivariate analysis identified IRRDR≥6 as the only viral genetic factor that independently predicted SVR. CONCLUSION NS5A (IRRDR and ISDR) and core protein polymorphisms are associated with the outcome of PEG-IFN/RBV therapy for chronic hepatitis C. In particular, IRRDR≥6 is a useful marker for prediction of SVR.
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Affiliation(s)
- Ahmed El-Shamy
- Division of Microbiology, Center for Infectious Diseases, Kobe University Graduate School of Medicine, Kobe, Japan
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Toyoda H, Kumada T, Tada T, Arakawa T, Hayashi K, Honda T, Katano Y, Goto H. Association between HCV amino acid substitutions and outcome of peginterferon and ribavirin combination therapy in HCV genotype 1b and high viral load. J Gastroenterol Hepatol 2010; 25:1072-8. [PMID: 20594221 DOI: 10.1111/j.1440-1746.2010.06240.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
BACKGROUND AND AIM We prospectively compared the sensitivity to interferon (IFN) and the efficacy of antiviral combination therapy with peginterferon (PEG-IFN) and ribavirin for chronic hepatitis C virus (HCV) genotype 1b infection according to the amino acid sequences of the HCV core, E1, and NS5A regions reported to be associated with the outcome of antiviral therapy. METHODS A total of 107 patients with HCV genotype 1b were investigated. All patients received combination therapy with PEG-IFN alpha-2b and ribavirin. Amino acids 70 and 91 (core), 139 (E1), and 2209-2248 (NS5A) of HCV were analyzed by direct nucleotide sequencing. RESULTS The reduction in HCV RNA concentration at 24 h after a single administration of conventional IFN-alpha and after the start of combination therapy was significantly less marked, and rates of complete early virologic response, end-of-treatment response, and sustained virologic response (SVR) were significantly lower (all P < 0.0001) in patients with glutamine at amino acid 70 (n = 29) than in those with arginine at that position (n = 70). We found no differences associated with the other amino acid positions. Amino acid 70 was an independent factor for the responses to the therapy in multivariate analysis. CONCLUSION The identity of amino acid 70 of the HCV core region affected the sensitivity to IFN; patients with glutamine at amino acid 70 of HCV showed resistance to IFN. Consequently, it strongly affected the outcome of combination therapy with PEG-IFN and ribavirin in Japanese patients with HCV genotype 1b.
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Affiliation(s)
- Hidenori Toyoda
- Department of Gastroenterology, Ogaki Municipal Hospital, Ogaki, Gifu, Japan.
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Xu J, Liu S, Xu Y, Tien P, Gao G. Identification of the nonstructural protein 4B of hepatitis C virus as a factor that inhibits the antiviral activity of interferon-alpha. Virus Res 2009; 141:55-62. [PMID: 19185598 DOI: 10.1016/j.virusres.2009.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2008] [Revised: 12/25/2008] [Accepted: 01/08/2009] [Indexed: 11/30/2022]
Abstract
Interferon-alpha (IFN-alpha) is the most commonly used therapeutics for the treatment of chronic viral infection. However, many viruses are resistant to IFN-alpha treatment to some degrees through encoding inhibitors of the IFN-alpha producing or signaling pathway. Multiple HCV viral proteins have been reported to be involved in IFN-alpha resistance. To develop a method to screen for factors that inhibit the antiviral activity of IFN-alpha, a mini-library of HCV genome was transduced into the Huh7 cells containing the HCV subgenomic replicon (CON1 HCV S2204I) and screened for the factor that rendered the cells more resistant to IFN-alpha treatment. A fragment of nonstructural protein 4B (NS4B), named tNS4B, was isolated. Expression of tNS4B or the full-length NS4B in CON1 HCV S2204I or naïve Huh7 cells inhibited the protection of the cells by IFN-alpha treatment from vesicular stomatitis virus (VSV) infection. In Huh7 cells expressing NS4B or tNS4B, IFN-alpha-induced phosphorylation levels of signal transducer and activator of transcription 1 (STAT1) were reduced. Furthermore, expression of NS4B reduced IFN-alpha-induced expression levels of type I interferon receptor and a reporter driven by the ISRE promoter. In conclusion, we have developed a method to screen for IFN-alpha resistance factors and identified HCV NS4B as such a factor.
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Affiliation(s)
- Jing Xu
- Wuhan University, Wu Han, Hubei Province, China
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Mihm U, Ackermann O, Welsch C, Herrmann E, Hofmann WP, Grigorian N, Welker MW, Lengauer T, Zeuzem S, Sarrazin C. Clinical relevance of the 2'-5'-oligoadenylate synthetase/RNase L system for treatment response in chronic hepatitis C. J Hepatol 2009; 50:49-58. [PMID: 19022516 DOI: 10.1016/j.jhep.2008.08.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 08/26/2008] [Accepted: 08/27/2008] [Indexed: 01/22/2023]
Abstract
BACKGROUND/AIMS Interferon-alpha induces 2'-5'-oligoadenylate synthetase which activates RNase L. Viral RNA is cleaved by RNase L at UU/UA dinucleotides. The clinical relevance of RNase L cleavage for response to an interferon-alpha-based therapy in chronic hepatitis C is unknown. METHODS RNase L cleavage sites within pre-treatment sequences coding for structural and non-structural hepatitis C virus proteins were compared between non-responders and responders to an interferon-alpha-based therapy. Furthermore, RNase L cleavage sites were analyzed in full length and partial genome isolates of hepatitis C virus genotype 1b infected non-responders before and during treatment and in different hepatitis C virus genotypes (1b, 2a/b, 3a/b). RESULTS No differences in RNase L cleavage sites were observed between non-responders and responders within a given hepatitis C genotype. Non-responders with hepatitis C virus genotype 1b infection did not eliminate UA/UU dinucleotides during therapy. Hepatitis C virus genotype 1b isolates showed a lower number of UA/UU dinucleotides than hepatitis C virus genotypes 2/3 (p < 0.001). CONCLUSIONS Response or non-response to an interferon-alpha-based therapy within a given hepatitis C virus genotype is not explained by differences for RNase L cleavage sites. General differences of interferon sensitivity between hepatitis C virus genotypes correlate significantly with frequencies of RNase L cleavage sites.
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Affiliation(s)
- Ulrike Mihm
- Medizinische Klinik I, Klinikum der Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, 60590 Frankfurt/Main, Germany
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Jones DM, Patel AH, Targett-Adams P, McLauchlan J. The hepatitis C virus NS4B protein can trans-complement viral RNA replication and modulates production of infectious virus. J Virol. 2009;83:2163-2177. [PMID: 19073716 DOI: 10.1128/jvi.01885-08] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Studies of the hepatitis C virus (HCV) life cycle have been aided by development of in vitro systems that enable replication of viral RNA and production of infectious virus. However, the functions of the individual proteins, especially those engaged in RNA replication, remain poorly understood. It is considered that NS4B, one of the replicase components, creates sites for genome synthesis, which appear as punctate foci at the endoplasmic reticulum (ER) membrane. In this study, a panel of mutations in NS4B was generated to gain deeper insight into its functions. Our analysis identified five mutants that were incapable of supporting RNA replication, three of which had defects in production of foci at the ER membrane. These mutants also influenced posttranslational modification and intracellular mobility of another replicase protein, NS5A, suggesting that such characteristics are linked to focus formation by NS4B. From previous studies, NS4B could not be trans-complemented in replication assays. Using the mutants that blocked RNA synthesis, defective NS4B expressed from two mutants could be rescued in trans-complementation replication assays by wild-type protein produced by a functional HCV replicon. Moreover, active replication could be reconstituted by combining replicons that were defective in NS4B and NS5A. The ability to restore replication from inactive replicons has implications for our understanding of the mechanisms that direct viral RNA synthesis. Finally, one of the NS4B mutations increased the yield of infectious virus by five- to sixfold. Hence, NS4B not only functions in RNA replication but also contributes to the processes engaged in virus assembly and release.
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Abstract
Hepatitis C virus (HCV) nonstructural protein 4B (NS4B), a poorly characterized integral membrane protein, is thought to function as a scaffold for replication complex assembly; however, functional interactions with the other HCV nonstructural proteins within this complex have not been defined. We report that a Con1 chimeric subgenomic replicon containing the NS4B gene from the closely related H77 isolate is defective for RNA replication in a transient assay, suggesting that H77 NS4B is unable to productively interact with the Con1 replication machinery. The H77 NS4B sequences that proved detrimental for Con1 RNA replication resided in the predicted N- and C-terminal cytoplasmic domains as well as the central transmembrane region. Selection for Con1 derivatives that could utilize the entire H77 NS4B or hybrid Con1-H77 NS4B proteins yielded mutants containing single amino acid substitutions in NS3 and NS4A. The second-site mutations in NS3 partially restored the replication of Con1 chimeras containing the N-terminal or transmembrane domains of H77 NS4B. In contrast, the deleterious H77-specific sequences in the C terminus of NS4B, which mapped to a cluster of four amino acids, were completely suppressed by second-site substitutions in NS3. Collectively, these results provide the first evidence for a genetic interaction between NS4B and NS3 important for productive HCV RNA replication.
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El-Shamy A, Nagano-Fujii M, Sasase N, Imoto S, Kim SR, Hotta H. Sequence variation in hepatitis C virus nonstructural protein 5A predicts clinical outcome of pegylated interferon/ribavirin combination therapy. Hepatology 2008; 48:38-47. [PMID: 18537193 DOI: 10.1002/hep.22339] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
UNLABELLED A substantial proportion of hepatitis C virus (HCV)-1b-infected patients still do not respond to interferon-based therapy. This study aims to explore a predictive marker for the ultimate virological response of HCV-1b-infected patients treated with pegylated interferon/ribavirin (PEG-IFN/RBV) combination therapy. Nonstructural protein 5A (NS5A) sequences of HCV in the pretreated sera of 45 patients infected with HCV-1b were analyzed. The mean number of mutations in the variable region 3 (V3) plus its upstream flanking region of NS5A (amino acid 2334-2379), referred to as IFN/RBV resistance-determining region (IRRDR), was significantly higher for HCV isolates obtained from patients who later achieved sustained virological response (SVR) by PEG-IFN/RBV than for those in patients undergoing non-SVR. The receiver operating characteristic curve analysis estimated six mutations in IRRDR as the optimal threshold for SVR prediction. Indeed, 16 (76%) of 21 SVR, but only 2 (8%) of 24 non-SVR, had HCV with six or more mutations in IRRDR (IRRDR > or = 6) (P < 0.0001). All of 18 patients infected with HCV of IRRDR of 6 or greater examined showed a significant (> or =1 log) reduction or disappearance of serum HCV core antigen titers within 24 hours after initial dose of PEG-IFN/RBV, whereas 10 (37%) of 27 patients with HCV of IRRDR of 5 or less did (P < 0.0001). The positive predictive value of IRRDR of 6 or greater for SVR was 89% (16/18; P = 0.0007), with its negative predictive value for non-SVR being 81% (22/27; P = 0.0008). CONCLUSION A high degree (> or =6) of sequence variation in IRRDR would be a useful marker for predicting SVR, whereas a less diverse (< or =5) IRRDR sequence predicts non-SVR.
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Affiliation(s)
- Ahmed El-Shamy
- Division of Microbiology, Kobe University Graduate School of Medicine, Kobe, Japan
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