NS5B

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

Persistent Replication of Hepatitis C Virus Replicons Expressing the β-Lactamase Reporter in Subpopulations of Highly Permissive Huh7 Cells

Abstract: Progress toward development of better therapies for the treatment of hepatitis C virus (HCV) infection has been hampered by poor understanding of HCV biology and the lack of biological assays suitable for drug screening. Here we describe a powerful HCV replication system that employs HCV replicons expressing the beta-lactamase reporter (bla replicons) and subpopulations of Huh7 cells that are more permissive (or "enhanced") to HCV replication than naive Huh7 cells. Enhanced cells represent a small fraction of permissive cells present among naive Huh7 cells that is enriched during selection with replicons expressing the neomycin phosphotransferase gene (neo replicons). The level of permissiveness of cell lines harboring neo replicons can vary greatly, and the enhanced phenotype is usually revealed upon removal of the neo replicon with inhibitors of HCV replication. Replicon removal is responsible for increased permissiveness, since this effect could be reproduced either with alpha interferon or with an HCV NS5B inhibitor. Moreover, adaptive mutations present in the replicon genome used during selection do not influence the permissiveness of the resulting enhanced-cell population, suggesting that the mechanisms governing the permissiveness of enhanced cells are independent from viral adaptation. Because the beta-lactamase reporter allows simultaneous quantitation of replicon-harboring cells and reporter activity, it was possible to investigate the relationship between genome replication activity and the frequency with which transfected genomes can establish persistent replication. Our study demonstrates that differences in the replication potential of the viral genome are manifested primarily in the frequency with which persistent replication is established but modestly affect the number of replicons observed per replicon-harboring cell. Replicon copy number was found to vary over a narrow range that may be defined by a minimal number required for persistent maintenance and a maximum that is limited by the availability of essential host factors.

Inhibitors of the Hepatitis C Virus RNA-Dependent RNA Polymerase NS5B

Abstract: More than 20 years after the identification of the hepatitis C virus (HCV) as a novel human pathogen, the only approved treatment remains a combination of pegylated interferon-α and ribavirin This rather non-specific therapy is associated with severe side effects and by far not everyone benefits from treatment Recently, progress has been made in the development of specifically targeted antiviral therapy for HCV (STAT-C) A major target for such direct acting antivirals (DAAs) is the HCV RNA-dependent RNA polymerase or non-structural protein 5B (NS5B), which is essential for viral replication This review will examine the current state of development of inhibitors targeting the polymerase and issues such as the emergence of antiviral resistance during treatment, as well as strategies to address this problem

Non-nucleoside inhibitors of the HCV NS5B polymerase: progress in the discovery and development of novel agents for the treatment of HCV infections.

Abstract: The severe health conditions associated with chronic HCV infection remain a global concern. Small-molecule drugs that specifically target essential virally encoded enzymes have not yet progressed to market, and the current standard of care continues to rely on a combination of pegylated IFN with ribavirin. This therapy has serious side effects and a significant proportion of patients infected with HCV genotype 1 (the major genotype in industrialized countries) have an unsatisfactory outcome with this therapy. Major advances have been realized in the development of specific non-nucleoside inhibitors of the viral NS5B RNA-dependent RNA polymerase. This well-characterized replicative enzyme is a highly drugable target that, in addition to its active site, features at least three known allosteric binding pockets that regulate RNA synthesis and are suitable for inhibitor design. Clinical proof-of-concept for allosteric non-nucleoside HCV polymerase inhibitors has been reported and several compounds have progressed into preclinical studies. It is likely that in the future NS5B inhibitors will form an integral part of more effective anti-HCV therapies, combining the use of small-molecule antiviral drugs with or without the assistance of immune modulators such as IFNs in order to minimize the emergence of resistance.