Susceptibility of human liver cell cultures to hepatitis C virus infection

The missing pieces of the HCV entry puzzle

The past decade has witnessed steady and rapid progress in HCV research, which has led to the recent breakthrough in therapies against this significant human pathogen. Yet a deeper understanding of the life cycle of the virus is required to develop more affordable treatments and to advance vaccine design. HCV entry presents both a challenge for scientific research and an opportunity for alternative intervention approaches, owning to its highly complex nature and the myriad of players involved. More than half a dozen cellular proteins are implicated in HCV entry; and a more definitive picture regarding the structures of the glycoproteins is emerging. A role of apolipoproteins in HCV entry has also been established. Still, major questions remain, and the answers to these, which we summarize in this review, will hopefully close the gaps in our understanding and complete the puzzle that is HCV entry.

Persistent hepatitis C virus infection in microscale primary human hepatocyte cultures

Hepatitis C virus (HCV) remains a major public health problem, affecting approximately 130 million people worldwide. HCV infection can lead to cirrhosis, hepatocellular carcinoma, and end-stage liver disease, as well as extrahepatic complications such as cryoglobulinemia and lymphoma. Preventative and therapeutic options are severely limited; there is no HCV vaccine available, and nonspecific, IFN-based treatments are frequently ineffective. Development of targeted antivirals has been hampered by the lack of robust HCV cell culture systems that reliably predict human responses. Here, we show the entire HCV life cycle recapitulated in micropatterned cocultures (MPCCs) of primary human hepatocytes and supportive stroma in a multiwell format. MPCCs form polarized cell layers expressing all known HCV entry factors and sustain viral replication for several weeks. When coupled with highly sensitive fluorescence- and luminescence-based reporter systems, MPCCs have potential as a high-throughput platform for simultaneous assessment of in vitro efficacy and toxicity profiles of anti-HCV therapeutics.

Primary cultures of human hepatocytes isolated from hepatitis C virus-infected cirrhotic livers as a model to study hepatitis C infection

BACKGROUND/AIM

Since the discovery of hepatitis C virus (HCV), researchers have encountered difficulties with in vitro models. The aim of this study was to determine whether HCV-infected human primary hepatocytes, isolated from cirrhotic livers at liver transplantation, can be used as a model to study HCV infection.

METHODS

Hepatocytes were isolated with collagenase and cultured over a 20-day period on different matrices. Viral kinetics was monitored with/without treatment by real-time polymerase chain reaction.

RESULTS

Cell yield and viability were higher with uninfected/non-cirrhotic livers (77.2+/-1.8%) in comparison with HCV-infected cirrhotic livers (68.8+/-12%). HCV-infected hepatocytes behaved similar to non-infected cells and expressed albumin and cytochrome P4502E1. HCV-positive strand was identified in supernatants and cell lysates. HCV-negative strand was only found inside cells and correlated with viral RNA recovery in the medium. Improvement in the degree of hepatocyte differentiation was associated with better HCV recovery. Antiviral treatment with interferon-alpha, EX4 and cyclosporine A induced significant reductions in HCV RNA.

CONCLUSION

Primary cultures of HCV-infected human hepatocytes from end-stage cirrhotic livers is feasible, represents an excellent model to study specific virus-host interactions and can be used to assess viral replication.

[Production of infectious hepatitis C virus in cell culture]

Hepatitis C virus (HCV) is a major public health problem, infecting an estimated 170 million people worldwide. Current therapy for HCV-related chronic hepatitis is based on the use of interferon. However, virus clearance rates are insufficient. Investigations to develop the anti-viral therapy or to understand the life cycle of this virus have been hampered by the lack of viral culture systems. We isolated the JFH-1 strain from a patient with fulminant hepatitis, and the JFH-1 subgenomic replicon could replicate efficiently in culture cell without adaptive mutation. Recently, we developed the HCV infection system in culture cells with this JFH-1 strain. The full-length JFH-1 RNA was transfected into Huh7 cells. Subsequently, viral RNA efficiently replicated in transfected cells and viral particles were secreted. Furthermore, secreted virus displayed infectivity for naive Huh7 cells. This system provides a powerful tool for studying the viral life cycle and constructing anti-viral strategies.

A vaccinia replication system for producing recombinant hepatitis C virus

AIM: To develop a cell culture system capable of producing high titer hepatitis C virus (HCV) stocks with recombinant vaccinia viruses as helpers.

METHODS: Two plasmids were used for the generation of recombinant HCV: one containing the full-length HCV cDNA cloned between T7 promoter and T7 terminator of pOCUS-T7 vector, and the other containing the HCV polyprotein open reading frame (ORF) directly linked to a vaccinia late promoter in PSC59. These two plasmids were co-transfected into BHK₂₁ cells, which were then infected with vTF7-3 recombinant vaccinia helper viruses.

RESULTS: After 5 d of incubation, approximately 3.6 × 10⁷ copies of HCV RNA were present per milliliter of cell culture supernatant, as detected by fluorescence quantitative RT-PCR (FQ-PCR). The yield of recombinant HCV using this cell system increased 100- to 1000-fold compared to in vitro-transcribed HCV genomic RNA or selective subgenomic HCV RNA molecule method.

CONCLUSION: This cell culture system is capable of producing high titer recombinant HCV.

Intracellular cleavage of hepatitis C virus RNA and inhibition of viral protein translation by hammerhead ribozymes

To determine the effects of hammerhead ribozymes against hepatitis C virus (HCV) RNA on viral protein translation, a luciferase reporter gene vector, pCMV/T7-NCRCdelta-luc, was constructed containing the 5'-noncoding region (5'-NCR) and part of the core region of HCV. Four ribozymes, Rz1-Rz4, were designed to cleave at nucleotide positions 136-160, 313-337, 496-520, and 373-388, respectively. Each ribozyme cleaved the target RNA at expected positions under cell-free conditions. Rz2 and Rz4 significantly suppressed translation of NCRCdelta-luc RNA by 71 and 49%, respectively. Translation of control luciferase mRNA lacking viral elements was not affected by the ribozymes. Furthermore, when NCRCdelta-luc RNA and ribozymes were cotransfected into cells, Rz2 and Rz4 significantly suppressed expression by 73 and 56%, respectively. In contrast, cleavage-deficient ribozymes with a point mutation in the hammerhead domain had no significant effect. To determine the effects of endogenously produced ribozymes, eukaryotic expression vectors for Rz2 and Rz4 were constructed. Cotransfection of the vectors with CMV/T7-NCRCdelta-luc showed suppression of luciferase activities to 50 and 61%, respectively. Moreover, transfection of pCMV/T7-NCRCdelta-luc into stable Rz2 and Rz4 producer cells also showed substantial inhibition of luciferase activity. Ribozymes directed against the HCV genome can substantially and specifically inhibit viral gene expression under intracellular conditions.

Virology of hepatitis C virus

Hepatitis C virus (HCV) has been identified as the main causative agent of posttransfusion non-A, non-B hepatitis. Through recently developed diagnostic assays, routine serologic screening of blood donors has prevented most cases of posttransfusion hepatitis. The purpose of this paper is to comprehensively review current information regarding the virology of HCV. Recent findings on the genome organization, its relationship to other viruses, the replication of HCV ribonucleic acid, HCV translation, and HCV polyprotein expression and processing are discussed. Also reviewed are virus assembly and release, the variability of HCV and its classification into genotypes, the geographic distribution of HCV genotypes, and the biologic differences between HCV genotypes. The assays used in HCV genotyping are discussed in terms of reliability and consistency of results, and the molecular epidemiology of HCV infection is reviewed. These approaches to HCV epidemiology will prove valuable in documenting the spread of HCV in different risk groups, evaluating alternative (nonparenteral) routes of transmission, and in understanding more about the origins and evolution of HCV.