ABSTRACT
We characterized a novel substitution conferring moderate resistance to telaprevir, a peptidomimetic inhibitor of hepatitis C virus protease. V36C conferred a 4.0-fold increase in the telaprevir 50% inhibitory concentration in an enzyme assay and a 9.5-fold increase in the replicon model. The replication capacity of a replicon harboring V36C was close to that of the wild-type protease. This case emphasizes the complexity of hepatitis C virus resistance to protease inhibitors.
Subject(s)
Antiviral Agents/pharmacology , Hepacivirus/drug effects , Hepacivirus/genetics , Oligopeptides/pharmacology , Serine Proteinase Inhibitors/pharmacology , Amino Acid Substitution , Antiviral Agents/chemistry , Drug Resistance, Viral/genetics , Genetic Variation , Hepacivirus/enzymology , Hepatitis C/drug therapy , Hepatitis C/virology , Humans , In Vitro Techniques , Models, Molecular , Molecular Mimicry , Oligopeptides/chemistry , Serine Proteinase Inhibitors/chemistry , Viral Nonstructural Proteins/antagonists & inhibitors , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/genetics , Virus Replication/drug effectsABSTRACT
BACKGROUND & AIMS: Silymarin is a mixture of flavonolignans extracted from the milk thistle. Silymarin contains several molecules, including silibinin A, silibinin B, isosilibinin A, isosilibinin B, silicristin, and silidianin. Intravenous infusion of silibinin induces dose-dependent reduction of hepatitis C virus (HCV) RNA levels. The aim of this study was to test the principal isomers contained in silymarin preparations for their ability to inhibit HCV enzymatic functions and replication in different models. METHODS: The inhibitory activity of silymarin components was tested in HCV RNA-dependent RNA polymerase and NS3/4A protease enzyme assays. Their ability to inhibit replication of an HCV genotype 1b replicon model and the JFH1 infectious HCV model in cell culture was also studied. RESULTS: Silibinin A, silibinin B, their water-soluble dihydrogen succinate forms and Legalon SIL, a commercially available intravenous preparation of silibinin, inhibited HCV RNA-dependent RNA polymerase function, with inhibitory concentrations 50% of the order of 75-100 microM. Silibinin A and silibinin B also inhibited HCV genotype 1b replicon replication and HCV genotype 2a strain JFH1 replication in cell culture. None of these compounds inhibited HCV protease function. CONCLUSIONS: Silibinin A and silibinin B, as well as Legalon SIL, inhibit HCV replicon and JFH1 replication in cell culture. This effect is at least partly explained by the ability of these compounds to inhibit HCV RNA-dependent RNA polymerase activity. Our results provide a basis for the optimization and subsequent development of members of the Flavonoid family as specific HCV antivirals.
Subject(s)
Antiviral Agents/pharmacology , Hepacivirus/drug effects , Nucleic Acid Synthesis Inhibitors/pharmacology , RNA-Dependent RNA Polymerase/antagonists & inhibitors , Viral Nonstructural Proteins/antagonists & inhibitors , Virus Replication/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , Dose-Response Relationship, Drug , Drug Resistance, Viral , Genotype , Hepacivirus/enzymology , Hepacivirus/genetics , Hepacivirus/growth & development , Humans , Mutation , RNA-Dependent RNA Polymerase/genetics , RNA-Dependent RNA Polymerase/metabolism , Recombinant Proteins/antagonists & inhibitors , Recombinant Proteins/metabolism , Silybin , Silymarin/pharmacology , Viral Nonstructural Proteins/genetics , Viral Nonstructural Proteins/metabolismABSTRACT
Hepatitis C virus subtype 3a (HCV-3a) originates from Asia and has spread widely among injecting drug users as well as other patient groups in industrialized countries. HCV subtype 3a infection remains highly prevalent and frequently transmitted in the population of intravenous drug users. The objective of this study was to understand better the mechanisms of the worldwide HCV-3a epidemics in drug users. Ninety-three sera from HCV-3a-infected IDUs from France, the United States, Brazil, Argentina, and Australia were studied. Phylogenetic analyses of the non-structural 5B region showed no specific clustering according to the continent of the patient's origin. Non-exclusive clusters of viral sequences from South America, Australia, and California were observed, but topologies were not supported by strong bootstrap values. The results suggest that HCV-3a has been transmitted from a common origin through a unique worldwide epidemic that rapidly spread among drug users. Regional transmission occurred in the recent past, leading to an embryonic genetic diversification of HCV-3a among local injecting drug user population.
