Browsing by Subject "Hepatitis C virus"

Estimated 180 million people worldwide are infected by hepatitis C virus. It causes liver diseases which are often asymptomatic. Chronic infections can lead to liver cirrhosis, transplantation and hepatocellular carcinoma. Drug development was slow until 1999 when the first cell culture model with autonomously replicating subgenomic HCV replicon was developed. It expresses the viral proteins that are necessary in HCV replication. The current interest in exploring new medicines is concentrated to the essential viral proteins, such as the NS3/4A protease, NS3 helicase, NS5A and NS5B RNA polymerase. HCV belongs to the Hepacivirus genus. Due to its high variability there are at least seven genotypes and several subtypes. Genotype 1 is the most common and the most difficult to treat. The current standard of care continues 24-48 weeks and consists mainly of pegylated interferon alpha and nucleoside analogue ribavirin, both non-specific HCV medicines with severe adverse effects. In 2011 two new direct-acting antivirals, protease inhibitors telaprevir and boceprevir, were approved for the treatment of HCV. A vaccine against HCV has not yet been developed. The aim of this study was to optimize and validate a robust cell-based assay for screening of replication inhibitors against HCV. Genetically modified Huh-7 cells harbor a subgenomic HCV replicon expressing only the viral proteins needed in viral replication. In addition, the replicon encodes a firefly luciferase as a reporter gene. The amount of expressed luciferase is directly correlated with the amount of HCV replication making the replicon system suitable for HTS. The optimized and validated method was used for screening HCV replication inhibitors from a library containing 113 marine-derived substances. Marine environment has been in recent years a very interesting source for finding new drug candidates. This study was part of international MAREX project which aims to discover new active molecules from marine resources. A total of 37 samples (32.7%) exhibited antiviral activity over 50%. A cytotoxicity evaluation in ATP assay was performed with these samples. 10 samples (27.0%) exhibited cytotoxicity below 20%, of which six were synthetic samples and four were extracts. Compounds with high antiviral activity, low cytotoxicity and clear dose-response in further studies should be tested with a cell line expressing the full-length HCV genome. The structural proteins can exhibit some characteristics which inactivate the compound identified as active in the replicon system.