Replication and infectivity of a novel genotype 1b hepatitis C virus clone

Hepatitis C virus infection is a major public health problem because of an estimated 170 million carriers worldwide. Genotype 1b is the major subtype of HCV in many countries and is resistant to interferon therapy. Study of the viral life cycle is important for understanding the mechanisms of interferon resistance of genotype 1b HCV strains. For such studies, genotype 1b HCV strains that can replicate and produce infectious virus particles in cultured cells are required. In the present study, we isolated HCV cDNA, which we named the NC1 strain, from a patient with acute severe hepatitis. Subgenomic replicon experiments revealed that several mutations enhanced the colony-formation efficiency of the NC1 replicon. The full-length NC1 genome with these adaptive mutations could replicate in cultured cells and produce infectious virus particles. The density gradient profile and morphology of the secreted virus particles were similar to those reported for the JFH-1 virus. Further introduction of a combination of mutations of the NS3 and NS5a regions into the NC1 mutants further enhanced secreted core protein levels and infectious virus titers in the culture medium of HCV-RNA-transfected cells. However, the virus infection efficiency was not sufficient for autonomous virus propagation in cultured cells. In conclusion, we established a novel cell culture-adapted genotype 1b HCV strain, termed NC1, which can produce infectious virus when the viral RNA is transfected into cells. This system provides an important opportunity for studying the life cycle of the genotype 1b HCV.     

Non-human primate surrogate model of hepatitis C virus infection

More than 170 million people worldwide are chronically infected by HCV, which is the causative agent of chronic hepatitis C, cirrhosis, and finally liver cancer. Although animal models of viral hepatitis are a prerequisite for the evaluation of antiviral and vaccine efficacy, the restricted host range of HCV has hampered the development of a suitable small animal model of HCV infection. Use of the chimpanzee, the only animal known to be susceptible to HCV infection, is limited by ethical and financial restrictions. In this regard GBV-B, being closely related to HCV, appears to be a promising non-human surrogate model for the study of HCV infection. This review describes the characteristic of GBV-B infection of New World monkeys, and discusses current issues concerning the GBV-B model and its future directions.     

Mutation patterns for two flaviviruses: hepatitis C virus and GB virus C/hepatitis G virus

We studied the mutation patterns of hepatitis C virus (HCV) and GB virus C/hepatitis G virus (HGV). Although the mutation patterns of the two viruses were similar to each other, they were quite different from that of HIV. In particular, the similarity of the patterns between HCV or HGV and human nuclear pseudogenes was statistically significant whereas there was no similarity between HIV and human nuclear pseudogenes. This finding suggests that the mutation patterns of HCV and HGV are similar to the patterns of spontaneous substitution mutations of human genes, implying that nucleotide analogues which are effective against HCV and HGV may have a side effect on the normal cells of humans.     

Interferon therapy in chronic hepatitis C virus infection

Abstract: Antiviral treatment of chronic hepatitis C with interferon is reviewed. Alpha-interferon, both recombinant alpha-2a, -2b and human lymphoblastoid interferon given at a dose of ≥3MU t.i.w. for 6–12 months will result in normalisation of ALT levels complete response) in some 50–60% of treated patients with chronic hepatitis C virus (HCV) infection. Approximately half of the complete responders to interferon will relapse within 6 months once treatment is withdrawn (non-sustained response). Longer treatment schedules (6 vs. 12 months) seem to diminish the relapse rate and increase the percentage of sustained response. In patients with sustained response to interferon treatment with continuously normal ALT levels ≥6 months after treatment stop a concomitant eradication of the viraemia is usually seen, whereas a non-sustained or non-response to interferon usually will indicate a continuous viraemia. Factors predictive of a favourable response are low pretreatment HCV RNA levels in serum, genotypes other than type II according to Okamoto, short disease duration, female gender and less pronounced liver damage, whereas high serum HCV RNA levels, having genotype II and cirrhosis, are predictive of a less favourable response. Patients with a sustained response and eradication of the viraemia will also improve their liver inflammation with diminishing scores for portal inflammation, piecemeal necrosis, lobular inflammation and also fibrosis after treatment. For non-responders and non-sustained responders to interferon, ribavirin especially in combination with interferon will offer some hope for the future.     

Putative hepatitis C virus cell receptors

Virus entry into a host cell comprises the first step of the viral life cycle. Blockage of this process can stop or prevent the rise of the infection. Development of compounds exhibiting directed blocking activity requires information about host cell and viral molecules, which are involved into reciprocal recognition resulting in the virus entry into the cell. This review is devoted to the problems of the identification of plasma membrane molecules, involved in binding of hepatitis C virus and its subsequent transfer inside the cells. The putative role of these molecules as hepatitis C virus receptors and co-receptors in the beginning and development of the infection is discussed.     

Prevalence of hepatitis C virus infection among recyclable waste collectors in Central-West Brazil

The prevalence of hepatitis C virus (HCV) in a population of recyclable waste collectors (n = 431) was assessed using a cross-sectional survey in all 15 cooperatives in the city of Goiânia, Central-West Brazil. The HCV prevalence was 1.6% (95% confidence interval: 0.6-3.6) and a history of sexually transmitted infections was independently associated with this infection. HCV RNA (corresponding to genotype 1; subtypes 1a and 1b) was detected in five/seven anti-HCV-positive samples. Although the study population reported a high rate (47.3%) of sharps and needle accidents, HCV infection was not more frequent in recyclable waste collectors than in the general Brazilian population.     

Persistent hepatitis C virus infections and hepatopathological manifestations in immune-competent humanized mice

The majority of hepatitis C virus (HCV) infection develops chronic infection, which causes steatosis, cirrhosis and hepatocellular carcinoma. However, understanding HCV chronicity and pathogenesis is hampered by its narrow host range, mostly restricted to human and chimpanzee. Recent endeavour to infect a variety of humanized mice has not been able to achieve persistent HCV infection unless the essential innate immune responsive genes are knocked out. Nevertheless, such immune-compromised humanized mice still lacked HCV infection-induced hepatopathogenesis. Here we report that transgenic mice in ICR background harboring both human CD81 and occludin genes (C/O^Tg) are permissive to HCV infection at a chronicity rate comparable to humans. In this mouse model, HCV accomplishes its replication cycle, leading to sustained viremia and infectivity for more than 12 months post infection with expected fibrotic and cirrhotic progression. Host factors favorable for HCV replication, and inadequate innate immune-response may contribute to the persistence. Lastly, NS3/4 protease inhibitor telaprevir can effectively inhibit de novo RNA synthesis and acute HCV infection of C/O^Tg mice. Thus, chronic HCV infection with complete replication cycle and hepatopathologic manifestations is recapitulated, for the first time, in immune-competent mice. This model will open a new venue to study the mechanisms of chronic hepatitis C and develop better treatments.     

Non-nucleoside inhibitors binding to hepatitis C virus NS5B polymerase reveal a novel mechanism of inhibition

The RNA-dependent RNA polymerase (NS5B) from hepatitis C virus (HCV) is a key enzyme in HCV replication. NS5B is a major target for the development of antiviral compounds directed against HCV. Here we present the structures of three thiophene-based non-nucleoside inhibitors (NNIs) bound non-covalently to NS5B. Each of the inhibitors binds to NS5B non-competitively to a common binding site in the "thumb" domain that is approximately 35 Angstroms from the polymerase active site located in the "palm" domain. The three compounds exhibit IC(50) values in the range of 270 nM to 307 nM and have common binding features that result in relatively large conformational changes of residues that interact directly with the inhibitors as well as for other residues adjacent to the binding site. Detailed comparisons of the unbound NS5B structure with those having the bound inhibitors present show that residues Pro495 to Arg505 (the N terminus of the "T" helix) exhibit some of the largest changes. It has been reported that Pro495, Pro496, Val499 and Arg503 are part of the guanosine triphosphate (GTP) specific allosteric binding site located in close proximity to our binding site. It has also been reported that the introduction of mutations to key residues in this region (i.e. Val499Gly) ablate in vivo sub-genomic HCV RNA replication. The details of NS5B polymerase/inhibitor binding interactions coupled with the observed induced conformational changes provide new insights into the design of novel NNIs of HCV.     

Lipid droplets and hepatitis C virus infection

Lipid droplets play an important part in the life cycle of hepatitis C virus and also are markers for steatosis, which is a common condition that arises during infection. These storage organelles are targeted by the viral core protein, which forms the capsid shell. Attachment of core to lipid droplets requires a C-terminal domain within the protein that is highly conserved between different virus isolates. In infected cells, the presence of core on lipid droplets creates loci that contain viral RNA and non-structural proteins involved in genome replication. Such locations may represent sites for initiating assembly and production of nascent virions. In addition to utilising lipid droplets as part the virus life cycle, hepatitis C virus induces their accumulation in infected hepatocytes. The mechanisms involved in this process are not understood but evidence from patient-based studies and model systems suggests the involvement of both viral and host factors.     

我国西部1a型丙肝病毒结构区的cDNA克隆和序列分析

克隆我国西部丙型肝炎病毒全部结构区基因,为探讨HCV的变异和致癌作用,研制丙肝疫苗作准各。从1名西安市丙肝感染血液中,用Trizol试剂裂解HCV病毒颗粒,用糖原与RNA共沉淀提取HCVRNA,用AMV逆转录酶和随机引物逆转录为eDNA,用RT-PCR方法扩增目的片段并转化到pGEM-T质粒,得到pGEM-T-HCVc、pGEM-T-HCVel和pGEM-T-HCVe2克隆。将以上3个克隆用特定的酶降解,用连结酶进行连接,构建了HCV结构区的完整克隆。将克隆好的质粒pGEM-T-HCVjg从两端双向测广手,得到完整的HCV结构基因eDNA核苷酸序列,总长度为2238bp,与已发表的HCV序列长度一致,未发现缺失或移码突变,序列中间亦未发现转录终止子。本序列与HCVla、lb序列核苷酸的同源性分别为91．8％、84．5％;氨基酸的同源性分别为94.2％、86．3％;应为HCVla亚型。以上结果说明我国西部地区存在HCVla亚型,所克隆HCV结构区eDNA克隆可以用于基因工程表达。     

Autoimmune hepatitis and hepatititis C virus infection

Abstract: The identification of the hepatitis C virus (HCV) and the availability of serological tests for the identification of its infection has deeply changed our view of autoimmune hepatitis. In fact, we have learned that autoantibodies such as anti-nuclear, anti-smooth muscle and anti-liver kidney microsomes, cannot be considered specific any longer for the diagnosis, of autoimmune hepatitis, since they are frequently found in association with HCV. The new clinical entity characterized by the association of autoantibodies with signs of HCV infection is presently under evaluation. This, in order to understand what is the prevalent mechanism, viral or autoimmune, operating in these patients and to chose the best treatment regimen.     

Reproducibility and usability of chronic virus infection model using agent-based simulation; comparing with a mathematical model

We created agent-based models that visually simulate conditions of chronic viral infections using two software. The results from two models were consistent, when they have same parameters during the actual simulation. The simulation results comprise a transient phase and an equilibrium phase, and unlike the mathematical model, virus count transit smoothly to the equilibrium phase without overshooting which correlates with actual biology in vivo of certain viruses. We investigated the effects caused by varying all the parameters included in concept; increasing virus lifespan, uninfected cell lifespan, uninfected cell regeneration rate, virus production count from infected cells, and infection rate had positive effects to the virus count during the equilibrium period, whereas increasing the latent period, the lifespan-shortening ratio for infected cells, and the cell cycle speed had negative effects. Virus count at the start did not influence the equilibrium conditions, but it influenced the infection development rate. The space size had no intrinsic effect on the equilibrium period, but virus count maximized when the virus moving speed was twice the space size. These agent-based simulation models reproducibly provide a visual representation of the disease, and enable a simulation that encompasses parameters those are difficult to account for in a mathematical model.     

Retinoids and rexinoids inhibit hepatitis C virus independently of retinoid receptor signaling

Using a high-throughput screening system involving HCV JFH-1-Huh 7.5.1 cells, we determined that the ligands of class II nuclear receptors, retinoids and rexinoids inhibit HCV infection. Retinoids, ligands of retinoic acid receptor (RAR), and rexinoids, ligands of retinoid X receptor (RXR), reduced extracellular HCV RNA of HCV infected cells in a dose-dependent manner. The 50% effective concentrations were below 10 nM, and the 50% cytotoxic concentrations were over 10 μM. Both agonists and antagonists demonstrated inhibition, which indicates that the effect is not dependent on retinoic acid signaling. These chemicals reduced HCV RNA and NS5A protein levels in cells harboring the subgenomic HCV replicon RNA, which suggests that the chemicals affect HCV RNA replication. These compounds were also effective against persistently infected cells, although the reduction in the intracellular HCV RNA was smaller than that of the extracellular HCV RNA, suggesting that viral post-replication step is also inhibited. In combination with interferon (IFN), retinoid exhibited a synergistic effect. Retinoids did not enhance expression of the IFN effector molecule PKR. These series of compounds warrant further investigation as new class of HCV drugs, for the clinical translation of our observation may lead to increased anti-HCV efficacy.     

Assays for RNA synthesis and replication by the hepatitis C virus

At least six major genotypes of Hepatitis C virus (HCV) cause liver diseases worldwide.The efficacy rates with current standard of care are about 50％ against genotype 1,the most prevalent strain in the...     

丙型肝炎病毒核心蛋白在大肠杆菌中的表达

目的：建立稳定表达丙型肝炎病毒(HCV)核心蛋白的原核表达系统,获得高产量的纯化核心蛋白。方法：应用多聚酶链反应(PCR),以HCV—H株全长cDNA序列为模板,扩增获得核心区基因片段,克隆入原核表达载体pBVIL1,构建原核表达载体pBVIL1-C,转化HB101宿主菌,通过温度诱导表达核心蛋白。结果：扩增得到目的基因长度为573bp,构建pBVIL1-C表达载体,在HB101宿主菌中通过温度诱导获得稳定表达,表达蛋白占菌体总蛋白含量的21％,Western—Blot检测证实表达产物可与HCV患者阳性血清发生特异性结合反应。结论：HCV核心蛋白可在大肠杆菌中获得高表达并具有良好的反应原性。     

Human oncogenic viruses: Hepatitis B and hepatitis C viruses and their role in hepatocarcinogenesis

Chronic infections caused by hepatitis B virus (HBV) and/or hepatitis C virus (HCV) are the main risk factors for the development of hepatocellular carcinoma (HCC) in humans. Both viruses cause a wide spectrum of clinical manifestations ranging from healthy carrier state to acute and chronic hepatitis, liver cirrhosis, and HCC. HBV and HCV belong to different viral families (Hepadnoviridae and Flaviviridae, respectively); they are characterized by different genetic structures. Clinical manifestations of these viral infections result from the interaction between these viruses and host hepatocytes (i.e. between viral and cell genomes). Proteins encoded by both viruses play an important role in processes responsible for immortalization and transformation of these cells. Chronic inflammation determined by host immune response to the viral infection, hepatocyte death and their compensatory proliferation, as well as modulation of expression of some regulatory proteins of the cell (growth factors, cytokines, etc.) are the processes that play the major role in liver cancer induced by HBV and HCV.     

Mizoribine inhibits hepatitis C virus RNA replication: effect of combination with interferon-alpha

Interferon (IFN)-alpha monotherapy, as well as the more effective combination therapy of IFN-alpha and ribavirin, are currently used for patients with chronic hepatitis C caused by hepatitis C virus (HCV) infection, although the mechanisms of the antiviral effects of these reagents on HCV remain ambiguous, and side effects such as anemia due to the administration of ribavirin present a problem for patients who are advanced in years. Using a recently developed reporter assay system in which genome-length dicistronic HCV RNA encoding Renilla luciferase gene was found to replicate efficiently, we found that mizoribine, an imidazole nucleoside, inhibited HCV RNA replication. The anti-HCV activity of mizoribine (IC50: approximately 100 microM) was similar to that of ribavirin. Using this genome-length HCV RNA replication monitor system, we were the first to demonstrate that the combination of IFN-alpha and ribavirin exhibited more effective anti-HCV activity than the use of IFN-alpha alone. Moreover, we found that the anti-HCV activity of mizoribine in co-treatment with IFN-alpha was at least equivalent to that of ribavirin. This effect was apparent in the presence of at least 5 microM mizoribine. Since mizoribine is currently used in several clinical applications and has not been associated with severe side effects, mizoribine is considered to be of potential use as a new anti-HCV reagent in combination with IFN-alpha.     

Influence of the hepatitis C virus 3′-untranslated region on IRES-dependent and cap-dependent translation initiation

Translation of hepatitis C virus (HCV) genomic RNA is directed by an internal ribosome entry site (IRES) in the 5′-untranslated region (5′-UTR), and the HCV 3′-UTR enhances IRES activity. Since the HCV 3′-UTR has a unique structure among 3′-UTRs, we checked possible communication between the 5′- and the 3′-UTR of HCV during translation using chimeric reporter RNAs. We show that translation directed by the HCV IRES and by the HCV-like IRES of porcine teschovirus (PTV) which belongs to a quite distinct family of viruses (picornaviruses) or by the EMCV IRES is also enhanced by the HCV 3′-UTR or by a poly(A)-tail in different cell types.     

Increased frequency of micronuclei in the lymphocytes of patients chronically infected with hepatitis B or hepatitis C virus

In this study, we analysed the frequency of micronuclei (MN), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) and evaluated mutagen-induced sensitivity in the lymphocytes of patients chronically infected with hepatitis B virus (HBV) or hepatitis C virus (HCV). In total, 49 patients with chronic viral hepatitis (28 HBV-infected and 21 HCV-infected patients) and 33 healthy, non-infected blood donor controls were investigated. The frequencies (‰) of MN, NPBs and NBUDs in the controls were 4.41 ± 2.15, 1.15 ± 0.97 and 2.98 ± 1.31, respectively. The frequencies of MN and NPBs were significantly increased (p < 0.0001) in the patient group (7.01 ± 3.23 and 2.76 ± 2.08, respectively) compared with the control group. When considered separately, the HBV-infected patients (7.18 ± 3.57) and HCV-infected patients (3.27 ± 2.40) each had greater numbers of MN than did the controls (p < 0.0001). The HCV-infected patients displayed high numbers of NPBs (2.09 ± 1.33) and NBUDs (4.38 ± 3.28), but only the HBV-infected patients exhibited a significant difference (NPBs = 3.27 ± 2.40, p < 0.0001 and NBUDs = 4.71 ± 2.79, p = 0.03) in comparison with the controls. Similar results were obtained for males, but not for females, when all patients or the HBV-infected group was compared with the controls. The lymphocytes of the infected patients did not exhibit sensitivity to mutagen in comparison with the lymphocytes of the controls (p = 0.06). These results showed that the lymphocytes of patients who were chronically infected with HBV or HCV presented greater chromosomal instability.