An in vitro model of hepatitis C virion production

Abstract

The hepatitis C virus (HCV) is a major cause of liver disease worldwide. The understanding of the viral life cycle has been hampered by the lack of a satisfactory cell culture system. The development of the HCV replicon system has been a major advance, but the system does not produce virions. In this study, we constructed an infectious HCV genotype 1b cDNA between two ribozymes that are designed to generate the exact 5 and 3 ends of HCV. A second construct with a mutation in the active site of the viral RNA-dependent RNA polymerase (RdRp) was generated as a control. The HCV-ribozyme expression construct was transfected into Huh7 cells. Both HCV structural and nonstructural proteins were detected by immunofluorescence and Western blot. RNase protection assays showed positive-and negative-strand HCV RNA. Sequence analysis of the 5 and 3 ends provided further evidence of viral replication. Sucrose density gradient centrifugation of the culture medium revealed colocalization of HCV RNA and structural proteins in a fraction with the density of 1.16 g͞ml, the putative density of HCV virions. Electron microscopy showed viral particles of Ϸ50 nm in diameter. The level of HCV RNA in the culture medium was as high as 10 million copies per milliliter. The HCV-ribozyme construct with the inactivating mutation in the RdRp did not show evidence of viral replication, assembly, and release. This system supports the production and secretion of high-level HCV virions and extends the repertoire of tools available for the study of HCV biology.assembly ͉ cell culture ͉ infection ͉ ribozyme ͉ viral replication T he hepatitis C virus (HCV) is an important cause of human illness worldwide (1). Although it has proven to be a difficult public health problem, it has been no easier to study in the laboratory. A major impediment has been the lack of robust model systems to study the complete viral life cycle. HCV is a member of the Flaviviridae family of Ϸ9.6 kb, and it has a central ORF flanked by the 5Ј and 3Ј noncoding regions. The ORF is divided into the coding sequences for the structural proteins at the 5Ј end and the nonstructural proteins at the 3Ј end. Study of the biology of hepatitis C at a molecular level focused initially on expression and manipulation of individual viral proteins in tissue culture.The development of the subgenomic and genomic replicons is a major breakthrough to understanding viral replication and viral-cell interactions and provides a means to test therapeutic targets (2, 3). However, as yet, none of these systems produce viral particles, nor do they produce infectious virions. Although some infectious tissue culture systems have been described; in general, these systems have not been robust enough to study the complete viral life cycle (4, 5).Why virion production has been such an elusive goal remains unclear; however, the promise of a system that produces authentic virions is clear. Not only would more of the biology of the virus become accessible for study, but also such a system would provide a means to s...

Extrahepatic replication of HCV: Insights into clinical manifestations and biological consequences

“…35,40,41 Recently, the development of self-replicating HCV RNA replicons has revolutionized the study of HCV; 42 however, these systems are restricted to a single, highly permissive hepatocyte-derived cell line. 43,44 Only within the last year have HCV systems that support infectious HCV production been reported, [45][46][47][48] although they do not support HCV replication in non-hepatocyte-derived cells. Consequently, additional systems to study sustained viral replication in multiple hepatocyte-and non-hepatocyte-derived cells are critically needed to advance the molecular characterization of extrahepatic replication of HCV and its role in the progression of the disease.…”

Establishment of an infectious genotype 1b hepatitis C virus clone in human hepatocyte chimeric mice

“…To date, five full-length genotype 1b clones, HCV-N (Beard et al, 1999), Con-1 (Bukh et al, 2002), HCV-J4 (Okamoto et al, 1992), HCV-CG1b (Thomson et al, 2001) and HCV-BK (Takamizawa et al, 1991), have been demonstrated to be infectious by intrahepatic inoculation of transcribed HCV RNA into the liver of chimpanzees. Among these, only the HCV-CG1b genome is reported to produce HCV particles when transfected into Huh7 cells (Heller et al, 2005).…”

Hepatitis C Virus Infection Downregulates the Ligands of the Activating Receptor NKG2D

“…A very recent report showed that HCV genome transfected cells maybe trigger ATM-dependent DNA damage response (5). This infection model system does not allow the study of viral entry and the earliest events in the HCV life cycle (12). In our study, HL7702 cells were infected with HCV-positive serum mimicking the natural HCV infection process.…”