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.

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.

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.Advances in virology have led to the development of novel therapeutics specifically targeting hepatitis C virus (HCV) (4). Telaprevir (VX-950; Vertex Pharmaceuticals Incorporated, Cambridge, MA) is a novel, highly selective, potent peptidomimetic inhibitor of the HCV nonstructural protein 3/4A (NS3/4A) protease (1, 3) which has reached phase III clinical development in combination with pegylated alpha interferon (IFN-␣) and ribavirin. Amino acid substitutions conferring telaprevir resistance have been reported at positions Val 36, Thr 54, Arg 155, and Ala 156 of the NS3 protease (2, 5). In patients treated with telaprevir and pegylated IFN-␣ with and without ribavirin, breakthroughs during treatment and relapses after treatment are characterized by the recurrence of telaprevir-resistant HCV variant replication (1).Here, we characterized a novel, so far unknown, telaprevir resistance substitution at position Val 36 in a 38-year-old treatment-naïve woman with chronic hepatitis C due to HCV genotype 1b infection. The patient was enrolled in PROVE2, a phase II randomized clinical trial assessing the efficacy and safety of telaprevir in combination with pegylated IFN-␣2a with or without ribavirin (1). The patient was treated with telaprevir at 750 mg/8 h, pegylated IFN-␣2a at 180 g/week, and ribavirin at 1.0 g/day. HCV RNA became undetectable (Ͻ10 IU/ml) on therapy, but after 43 days of treatment, the patient withdrew consent and stopped therapy. She continued to be followed up after treatment withdrawal. Figure 1 shows the kinetics of HCV RNA levels in the patient during the 43 days of therapy. HCV RNA was detected 8 weeks after treatment withdrawal, and HCV RNA levels returned to nearly baseline levels. Twenty to 24 full-length NS3 protease clones were sequenced at each HCV RNA-positive time point. The patient was infected with a wild-type, telaprevir sensitive viral population at the baseline (Fig. 1). At the time of posttreatment relapse, the HCV variants all bore a Val-to-Cys substitution at position 36 (V36C). The V36C substitution remained dominant throughout posttreatment followup, up to day 512 after the start of therapy (Fig. 1). This substitution was associated with a Leu-to-Phe substitution at position 14 of the protease (L14F). L14F is present in approximately 6% of all HCV sequences and 8.5% of HCV subtype 1b sequences available in the European HCV database (http: //euhcvdb.ibcp.fr/euHCVdb/). Based on molecular modeling, it is predicted to be located at more than 20 Å of the telaprevir binding site and is therefore unlikely to alter...

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