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Among human RNA viruses, hepatitis C virus (HCV) is unusual in that it causes persistent infection in the majority of infected people. To establish persistence, HCV evades host innate and adaptive immune responses by multiple mechanisms. Recent studies identified virus genome-derived small RNAs (vsRNAs) in HCV-infected cells; however, their biological significance during human HCV infection is unknown. One such vsRNA arising from the hepatitis C virus (HCV) E2 coding region impairs T cell receptor (TCR) signaling by reducing expression of a Src-kinase regulatory phosphatase (PTPRE) in vitro. Since TCR signaling is a critical first step in T cell activation, differentiation, and effector function, its inhibition may contribute towards HCV persistence in vivo. The effect of HCV infection on PTPRE expression in vivo has not been examined. Here, we found that PTPRE levels were significantly reduced in liver tissue and peripheral blood mononuclear cells (PBMCs) obtained from HCV-infected humans compared to uninfected controls. Loss of PTPRE expression impaired antigen-specific TCR signaling, and curative HCV therapy restored PTPRE expression in PBMCs; restoring antigen-specific TCR signaling defects. The extent of PTPRE expression correlated with the amount of sequence complementarity between the HCV E2 vsRNA and the PTPRE 3’ UTR target sites. Transfection of a hepatocyte cell line with full-length HCV RNA or with synthetic HCV vsRNA duplexes inhibited PTPRE expression, recapitulating the in vivo observation. Together, these data demonstrate that HCV infection reduces PTPRE expression in the liver and PBMCs of infected humans, and suggest that the HCV E2 vsRNA is a novel viral factor that may contribute towards viral persistence. [ABSTRACT FROM AUTHOR]

Introduction: Telomerase repairs the telomeric ends of chromosomes and is active in nearly all malignant cells. Hepatitis C virus (HCV) is known to be oncogenic and potential interactions with the telomerase system require further study. We determined the effects of HCV infection on human telomerase reverse transcriptase (TERT) expression and enzyme activity in primary human hepatocytes and continuous cell lines. Results: Primary human hepatocytes and Huh-7.5 hepatoma cells showed early de novo TERT protein expression 2–4 days after infection and these events coincided with increased TERT promoter activation, TERT mRNA, and telomerase activity. Immunoprecipitation studies demonstrated that NS3-4A protease-helicase, in contrast to core or NS5A, specifically bound to the C-terminal region of TERT through interactions between helicase domain 2 and protease sequences. Increased telomerase activity was noted when NS3-4A was transfected into cells, when added to reconstituted mixtures of TERT and telomerase RNA, and when incubated with high molecular weight telomerase ‘holoenzyme’ complexes. The NS3-4A catalytic effect on telomerase was inhibited with primuline or danoprevir, agents that are known to inhibit NS3 helicase and protease activities respectively. In HCV infected cells, NS3-4A could be specifically recovered with telomerase holoenzyme complexes in contrast to NS5A or core protein. HCV infection also activated the effector caspase 7 which is known to target TERT. Activation coincided with the appearance of lower molecular weight carboxy-terminal fragment(s) of TERT, chiefly sized at 45 kD, which could be inhibited with pancaspase or caspase 7 inhibitors. Conclusions: HCV infection induces TERT expression and stimulates telomerase activity in addition to triggering Caspase activity that leads to increased TERT degradation. These activities suggest multiple points whereby the virus can influence neoplasia. The NS3-4A protease-helicase can directly bind to TERT, increase telomerase activity, and thus potentially influence telomere repair and host cell neoplastic behavior. [ABSTRACT FROM AUTHOR]

Chronic Hepatitis C virus (HCV) infection is the leading cause of advanced liver disease worldwide. The virus successfully evades host immune detection and for many years has hampered efforts to find a safe, uncomplicated, and reliable oral antiviral therapy. Initially, interferon and ribavirin therapy was the treatment standard of care, but it offered limited performance across the wide spectrum of HCV disease and was fraught with excessive and often limiting side effects. Sofosbuvir (SOF) is a potent first-in-class nucleoside inhibitor that has recently been approved for treatment of HCV. The drug has low toxicity, a high resistance barrier, and minimal drug interactions with other HCV direct-acting antiviral agents such as protease inhibitors or anti-NS5A agents. SOF is safe and can be used across different viral genotypes, disease stages, and special patient groups, such as those coinfected with human immunodeficiency virus. When used in combination with ribavirin or another direct-acting antiviral agent, SOF has revolutionized the HCV treatment spectrum and set the stage for nearly universal HCV antiviral therapy. More so than any other anti-HCV drug developed to date, SOF offers the widest applicability for all infected patients, and new regimens will be tailored to maximize performance. [ABSTRACT FROM AUTHOR]

Background. Tetrapyrrole substrates and products of heme oxygenase are potent inhibitors of hepatitis C virus (HCV) replication. It is not clear whether this occurs through primary induction of type I interferon (IFN), inhibition of viral NS3/4A protease, or a combination of these mechanisms. We studied the antiviral actions of tetrapyrroles and their potential influence on type I IFN induction.Methods. The effects of tetrapyrrole on NS3/4A protease activity and type I IFN induction were assessed in HCV-permissive cells, replicons, or human embryonic kidney (HEK) 293 cells transfected with NS3/4A protease. Activation of innate immune signaling was determined after transfection of double-strand surrogate nucleic acid antigens or infection with defined sequence HCV cell culture (HCVcc) RNA.Results. Tetrapyrroles failed to directly induce IFN expression at concentrations that inhibited HCV replication and NS3/4A protease activity. However, they potently restored IFN induction after attenuation with NS3/4A protease, a process accompanied by preservation of the adapter protein, mitochondrial antiviral signaling protein, nuclear localization of IFN regulatory factor 3, and augmentation of IFN-stimulated gene products.Conclusions. Tetrapyrroles do not directly induce IFN, but they dramatically restore type I IFN signaling pathway after attenuation with NS3/4A protease. They show immunomodulatory as well as antiprotease activity and may be useful for treatment of HCV infection. [ABSTRACT FROM AUTHOR]

Antioxidant enzymes, including heme oxygenase (HO)-1, are an important line of defense against oxidant-mediated liver injury. Because hepatitis C virus (HCV) infection appears to increase the production of oxidants, we evaluated levels of antioxidant enzymes and HO-1 in liver-biopsy samples from HCV-infected patients by immunoblot and semiquantitative reverse-transcriptase polymerase chain reaction. In HCV-infected liver samples, levels of immunoreactive HO-1 and HO-1 mRNA were >4-fold lower than levels in control samples, but levels of superoxide dismutase and catalase were unaffected. Immunohistochemical results confirmed the decreased expression of HO-1 in hepatocytes from liver samples from HCV-infected patients but not in those from patients with other chronic liver diseases. The expression of HO-1 was also reduced in cell lines that stably express HCV core protein, which suggests that core gene products are capable of regulating the expression of HO-1. [ABSTRACT FROM AUTHOR]

Examines the presence of hepatitic C virus viremia in persons without detectable HCV antibodies. Characterization of serosilent HCV infection; Characteristics of persons acquiring HIV through transfusion of blood products; Percentage of HIV-positive intravenous drug users affected with HCV infection.