scispace - formally typeset
Search or ask a question
Topic

NS5B

About: NS5B is a research topic. Over the lifetime, 1314 publications have been published within this topic receiving 59534 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: It is demonstrated that NS5 B of JFH-1 contributed to this strain’s CsA-resistant phenotype and NS5B and CyPA are significant for determining HCV‘s sensitivity toCsA.
Abstract: Cyclosporine A (CsA) is a well-characterized anti-HCV reagent. Recently it was reported that the genotype 2a JFH-1 strain was more resistant than genotype 1 HCV strains to CsA in a cell culture system. However, the JFH-1 responsible region for the resistance to CsA remains unclear. It was also demonstrated that in genotype 1b HCVs, NS5B interacts with cyclophilin (CyP). To clarify whether or not NS5B of JFH-1 is significant for CsA resistance, we developed a chimeric replicon with NS5B of JFH-1 in the genotype 1b backbone. The chimeric replicon was more resistant to CsA than the parental genotype 1b replicon. Furthermore, reduction of CyPA had a greater effect on HCV RNA replication and sensitivity to CsA than reduction of CyPB. Here, we demonstrated that NS5B of JFH-1 contributed to this strain’s CsA-resistant phenotype. NS5B and CyPA are significant for determining HCV’s sensitivity to CsA.

9 citations

Journal ArticleDOI
TL;DR: It is found that R803 was more effective than alpha interferon (IFN-α) at blocking HCV RNA replication in the replicon model, and could potentially be developed as a treatment for HCV infection.
Abstract: Hepatitis C virus (HCV) infection is one of the major causes of viral hepatitis, with a great propensity to induce chronicity (21). Liver inflammation can persist for decades in chronic HCV infection and eventually leads to cirrhosis, end-stage liver disease, and hepatocellular carcinoma. HCV infection is a significant health care problem: it is estimated that approximately 170 million individuals are chronically infected with HCV worldwide, with ∼30,000 cases of new infection each year in the United States alone (1, 2, 46). No vaccine is currently available to prevent HCV infection. The standard treatment for HCV infection, a combination of pegylated alpha interferon (IFN-α) and ribavirin (RBV), is limited by its suboptimal response rate in a significant patient population, side effects, and affordability (11). Thus, it is critical to discover highly effective, safer therapies to improve the clinical management of HCV infection. HCV is an enveloped RNA virus belonging to the family Flaviviridae (9). HCV clinical isolates display high heterogeneity in their genomic RNA and amino acid sequences, and they are classified into six genotypes and numerous subtypes (49). It is documented that infections by different genotypes may produce different clinical outcomes and may respond differently to IFN-α-based antiviral treatment (for a review, see reference 11). Significantly, patients infected with genotype 1 viruses, which account for approximately 70% of HCV infections in the United States, exhibit poor rates of response to the IFN-α-based treatment. An ideal antiviral should, therefore, be effective against the majority, if not all, of the HCV genotypes. Upon entering the host cell, HCV releases its 9.6-kb genomic RNA into the cytoplasm, where it directs the translation of a single polyprotein of about 3,000 amino acids. The giant polyprotein is cotranslationally processed by host and viral proteases into structural proteins (core, E1, and E2) and nonstructural proteins (P7, NS2, NS3, NS4a, NS4b, NS5a, and NS5b). The mature nonstructural proteins (except P7 and NS2) and host factors assemble into membrane-associated RNA replication complexes, where a vast quantity of progeny viral RNA molecules are amplified from the incoming HCV genomic RNA (14, 18, 35). Although all the steps in the HCV life cycle can be targeted for drug discovery against HCV, the viral nonstructural proteins, specifically NS3 and NS5b, which encode well-defined enzymatic activities crucial for viral replication, are the major targets for antiviral discovery (10, 53). However, the replication of HCV viral RNA by the viral replication complex is quickly becoming another focus for drug discovery with the development of the HCV replicon system. Until the establishment of HCV replicons, the analysis of HCV replication was hampered due to the lack of a robust HCV cell culture system (5, 38). The first-generation HCV replicons are human hepatoma Huh-7 cell lines carrying engineered genotype 1b subgenomic RNA with the following genome organization: HCV 5′ nontranslated region (5′ NTR)-neomycin phosphotransferase (NPT) gene (also referred to as the neomycin resistance [Neor] gene)-encephalomyocarditis virus (EMCV) internal ribosome entry site (IRES)-HCV NS3-4a-4b-5a-5b-HCV 3′ NTR. Subsequent studies have shown that the efficiency of replicon establishment can be enhanced substantially by incorporating cell culture-adaptive mutations, especially those in NS3 and NS5a (5, 26, 37, 38). The HCV replicon system has been an effective tool for studying viral RNA replication and virus-host interactions. It also serves as an important cell-based system with which to evaluate antiviral drugs and to reveal drug resistance mechanisms (for a review, see reference 4). Moreover, the HCV replicon presents a unique drug-screening system, allowing for the screening of compounds inhibiting the viral enzymes as well as other targets of the HCV RNA replication process in a cellular environment. Such screens would perhaps facilitate the discovery of inhibitors that block the functions of NS4b and NS5a or interrupt virus-host interactions, discoveries that cannot be readily achieved with biochemical screens. Several efforts have already been made to screen small-molecule compound libraries against different versions of the HCV replicon system (17, 47, 50, 55). Here we describe the development of an HCV replicon assay for high-throughput screening and the characterization of one of the heterocyclic hits from screens of a 230,000-member chemical library. We show that the lead compound of this hit scaffold is effective at inhibiting HCV replicons of different genotypes and can enhance the inhibitory activity of IFN-α in the replicon model.

9 citations

Journal ArticleDOI
TL;DR: HCV-1b was predominant in the present Albanian population, as in southeastern Europe, and best matches for these HCV RNAs in GenBank were obtained in different countries worldwide.

9 citations

Journal ArticleDOI
TL;DR: This study shows that among this group of Iranian patients with β‐thalassemia major, 13.4% had activeHCV infection and 6.3% had occult HCV infection as evidenced by HCV RNA detected in PBMC specimens.
Abstract: Beta (β) thalassemia major is a genetic blood disorder with a deficiency in the hemoglobin beta chain, requiring blood transfusion therapy. Multiple blood transfusions increase the risk of transmitting blood-borne infections. The aim of this study is to determine the frequency of hepatitis C virus (HCV) infection in Iranian individuals with β-thalassemia major. A total of 164 patients with β-thalassemia major were recruited for this study. HCV RNA testing was done on plasma and peripheral blood mononuclear cells (PBMCs) from the HCV seropositive samples (with reverse transcriptase-nested polymerase chain reaction [PCR] method using primers from the 5'-untranslated region [UTR]), and all HCV RNA positive samples were genotyped by the restriction fragment length polymorphism assay. For confirmation of the HCV genotyping in PBMCs of occult HCV infection [OCI]-positive patients, the PCR products of two different regions of HCV (5'-UTR and nonstructural protein 5B [NS5B]) were sequenced. Of 164 patients, 29.3% were positive for anti-HCV antibodies, and HCV RNA was detected in the plasma specimens of 13.4% patients and in the PBMC samples of 15.2% participants. The genomic HCV-RNA was detected in PBMC samples in 3 (6.3%) of the total 48 individuals who were HCV seropositive, and plasma HCV-RNA negative (occult HCV infection). The subtypes of HCV in the plasma and PBMC samples of three participants were not identical. This study shows that among this group of Iranian patients with β-thalassemia major, 13.4% had active HCV infection and 6.3% had occult HCV infection as evidenced by HCV RNA detected in PBMC specimens. Therefore, the design of a prospective study that focuses on the diagnosis of OCI can be very valuable and provide more information.

8 citations

Journal ArticleDOI
TL;DR: A crystal structure of the NS5B S15G/C223H/V321I mutant of the JFH-1 isolate exhibited rearrangement to a conformation potentially consistent with short primer-template RNA binding, which could suggest a mechanism of resistance accomplished through a change in theNS5B conformation, which was better tolerated by genotype 2a virus than by viruses of other genotypes.
Abstract: Resistance to the 2′-F-2′-C-methylguanosine monophosphate nucleotide hepatitis C virus (HCV) inhibitors PSI-352938 and PSI-353661 was associated with a combination of amino acid changes (changes of S to G at position 15 [S15G], C223H, and V321I) within the genotype 2a nonstructural protein 5B (NS5B), an RNA-dependent RNA polymerase. To understand the role of these residues in viral replication, we examined the effects of single and multiple point mutations on replication fitness and inhibition by a series of nucleotide analog inhibitors. An acidic residue at position 15 reduced replicon fitness, consistent with its proximity to the RNA template. A change of the residue at position 223 to an acidic or large residue reduced replicon fitness, consistent with its proposed proximity to the incoming nucleoside triphosphate (NTP). A change of the residue at position 321 to a charged residue was not tolerated, consistent with its position within a hydrophobic cavity. This triple resistance mutation was specific to both genotype 2a virus and 2′-F-2′-C-methylguanosine inhibitors. A crystal structure of the NS5B S15G/C223H/V321I mutant of the JFH-1 isolate exhibited rearrangement to a conformation potentially consistent with short primer-template RNA binding, which could suggest a mechanism of resistance accomplished through a change in the NS5B conformation, which was better tolerated by genotype 2a virus than by viruses of other genotypes.

8 citations


Network Information
Related Topics (5)
Hepatitis C virus
32.2K papers, 1.1M citations
88% related
Viral replication
33.4K papers, 1.6M citations
86% related
Hepatitis B virus
39.1K papers, 1.2M citations
85% related
Interferon
28.9K papers, 1.2M citations
83% related
Virus
136.9K papers, 5.2M citations
82% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202310
202258
202128
202033
201943
201842