Establishment of an indicator cell system for hepatitis C virus

Although a cell culture system for HCV JFH-1 strain has been developed, no robust cell culture system for serum-derived HCV is available. In this study, we have established systems capable of monitoring infection with JFH-1 virus based on specific reporter gene expression through proteolysis of chimeric transcription factors by HCV NS3/4A protease. We utilized a transcriptional factor Gal4-TBP that synergistically enhances transcription of the GAL4UAS and HIV-1 LTR tandem promoter with the Tat protein. We constructed chimeric Tat and Gal4-TBP transcription factors containing the HCV NS3/4A cleavage sequence of a mitochondria-resident IPS-1, but not those of the HCV polyprotein, and manipulated them to localize in the ER. Upon infection with JFH-1 virus, the transcription factors were efficiently cleaved by HCV protease, migrated into the nucleus and activated the reporter gene under the tandem promoter. Upon infection with JFH-1 virus, the Huh7OK1/TG-Luc cell line carrying the transcription factors and a luciferase gene under the promoter expressed luciferase in a dose-dependent manner in close correlation with HCV RNA replication. Huh7OK1/TG-LNGFR cells carrying the transcription factors and a cDNA of human low affinity nerve growth factor receptor under the promoter were selectively concentrated by immunomagnetic cell sorting upon infection with JFH-1 virus. These results indicate that the chimeric constructs bearing the ER-resident IPS-1 sequence are specifically recognized and efficiently cleaved by HCV protease and are harnessed for detection of HCV replication and for recovery of HCV-infected cells. This strategy may be applicable for the establishment of cell culture systems for the isolation of serum-derived HCV.