Hepatitis C virus core protein binds to apolipoprotein AII and its secretion is modulated by fibrates

The Hepatitis E Virus Open Reading Frame 2 Protein: Beyond Viral Capsid

Hepatitis E virus (HEV) is a zoonotic pathogen causing hepatitis in both human and animal hosts, which is responsible for acute hepatitis E outbreaks worldwide. The 7.2 kb genome of the HEV encodes three well-defined open reading frames (ORFs), where the ORF2 translation product acts as the major virion component to form the viral capsid. In recent years, besides forming the capsid, more functions have been revealed for the HEV-ORF2 protein, and it appears that HEV-ORF2 plays multiple functions in both viral replication and pathogenesis. In this review, we systematically summarize the recent research advances regarding the function of the HEV-ORF2 protein such as application in the development of a vaccine, regulation of the innate immune response and cellular signaling, involvement in host tropism and participation in HEV pathogenesis as a novel secretory factor. Progress in understanding more of the function of HEV-ORF2 protein beyond the capsid protein would contribute to improved control and treatment of HEV infection.

Interdependent Impact of Lipoprotein Receptors and Lipid-Lowering Drugs on HCV Infectivity

The HCV replication cycle is tightly associated with host lipid metabolism: Lipoprotein receptors SR-B1 and LDLr promote entry of HCV, replication is associated with the formation of lipid-rich membranous organelles and infectious particle assembly highjacks the very-low-density lipoprotein (VLDL) secretory pathway. Hence, medications that interfere with the lipid metabolism of the cell, such as statins, may affect HCV infection. Here, we study the interplay between lipoprotein receptors, lipid homeostasis, and HCV infection by genetic and pharmacological interventions. We found that individual ablation of the lipoprotein receptors SR-B1 and LDLr did not drastically affect HCV entry, replication, or infection, but double lipoprotein receptor knock-outs significantly reduced HCV infection. Furthermore, we could show that this effect was neither due to altered expression of additional HCV entry factors nor caused by changes in cellular cholesterol content. Strikingly, whereas lipid-lowering drugs such as simvastatin or fenofibrate did not affect HCV entry or infection of immortalized hepatoma cells expressing SR-B1 and/or LDLr or primary human hepatocytes, ablation of these receptors rendered cells more susceptible to these drugs. Finally, we observed no significant differences between statin users and control groups with regards to HCV viral load in a cohort of HCV infected patients before and during HCV antiviral treatment. Interestingly, statin treatment, which blocks the mevalonate pathway leading to decreased cholesterol levels, was associated with mild but appreciable lower levels of liver damage markers before HCV therapy. Overall, our findings confirm the role of lipid homeostasis in HCV infection and highlight the importance of the mevalonate pathway in the HCV replication cycle.

Hepatitis C virus core protein: Not just a nucleocapsid building block, but an immunity and inflammation modulator

Coevolution occurs between viruses and their hosts. The hosts need to evolve means to eliminate pathogenic virus infections, and the viruses, for their own survival and multiplication, have to develop mechanisms to escape clearance by hosts. Hepatitis C virus (HCV) of Flaviviridae is a pathogen which infects human liver and causes hepatitis, a condition of liver inflammation. Unlike most of the other flaviviruses, HCV has an excellent ability to evade host immunity to establish chronic infection. The persistent liver infection leads to chronic hepatitis, liver cirrhosis, hepatocellular carcinoma (HCC), as well as extrahepatic HCV-related diseases. HCV genomic RNA only expresses 10 proteins, many of which bear functions, in addition to those involved in HCV life cycle, for assisting the virus to develop its persistency. HCV core protein is a structural protein which encapsulates HCV genomic RNA and assembles into nucleocapsids. The core protein is also found to exert functions to affect host inflammation and immune responses by altering a variety of host pathways. This paper reviews the studies regarding the HCV core protein-induced alterations of host immunity and inflammatory responses, as well as the involvements of the HCV core protein in pro- and anti-inflammatory cytokine stimulations, host cellular transcription, lipid metabolism, cell apoptosis, cell proliferations, immune cell differentiations, oxidative stress, and hepatocyte steatosis, which leads to liver fibrosis, cirrhosis, and HCC. Implications of roles played by the HCV core protein in therapeutic resistance are also discussed.

Systematic review: chronic viral hepatitis and metabolic derangement

BACKGROUND

The liver has a critical role in the metabolism of glucose and lipids. Chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) infection leads to a spectrum of liver disease including chronic hepatitis, cirrhosis and hepatocellular carcinoma. Metabolic syndrome (MetS) has a rising incidence owing to an epidemic of type 2 diabetes mellitus (T2DM) and obesity. Non-alcoholic fatty liver disease is a liver manifestation of MetS and has become the most common cause of chronic liver disease worldwide.

AIM

To summarise the interplay among hepatitis viruses, MetS and its components.

METHODS

We searched the literature about HBV, HCV infection, MetS, fatty liver and its components from PubMed.

RESULTS

With respect to the viral replication cycle, lipids are important mediators between viral entry and hepatocyte in HCV infection, but not in HBV infection. Thus, HCV infection is inversely associated with hyperlipidaemia and lipid rebound occurs following sustained viral response induced by interferon-based therapy or direct antiviral agents. In addition, HCV infection is positively associated with insulin resistance, hepatic steatosis, MetS and the risk of T2DM and atherosclerosis. In contrast, HBV infection may protect infected subjects from the development of MetS and hepatic steatosis. Accumulating evidence suggests that HBV infection is inversely associated with lipid metabolism, and exhibits no conclusive association with insulin resistance or the risk of T2DM and arteriosclerosis.

CONCLUSIONS

In patients with viral hepatitis and concurrent metabolic diseases, a multidisciplinary approach should be given rather than simply antiviral treatment.

Favouring modulation of circulating lipoproteins and lipid loading capacity by direct antiviral agents grazoprevir/elbasvir or ledipasvir/sofosbuvir treatment against chronic HCV infection

OBJECTIVE

Lipid homoeostasis is disturbed in patients with HCV infection. Direct-acting antiviral agent (DAA) treatment eradicates chronic HCV viraemia, but the dynamics of lipid components remain elusive. This study investigates the clinical manifestation and mechanistic relevance of plasma triglyceride (TG), cholesterol (Chol), lipoproteins and apolipoproteins (apos) after DAA treatment.

DESIGN

Twenty-four patients with chronic genotype 1 (GT1) HCV treated with elbasvir/grazoprevir or ledipasvir/sofosbuvir for 12 weeks, and followed-up thereafter, were recruited. Their TG, Chol, apoAI and apoB levels were quantified in plasma samples and individually fractionated lipoprotein of various classes. Liver fibrosis was evaluated using the FIB-4 Score. The TG and Chol loading capacities were calculated with normalisation to apoB, which represents per very low density lipoprotein (VLDL) and LDL particle unit RESULTS: DAA treatment achieved a sustained virological response rate of 91.7% and reduced the FIB-4 Score. Relative to the baseline, the plasma TG level was reduced but the Chol level increased gradually. Plasma apoB levels and apoB/apoAI ratio were transiently downregulated as early as the first 4 weeks of treatment. The TG and Chol loading capacities in VLDL were elevated by ~20% during the period of DAA treatment and had steadily increased by 100% at follow-up. Furthermore, the TG-to-Chol ratio in VLDL was increased, while the ratio in LDL was reduced, indicating an efficient catabolism.

CONCLUSION

The DAA treatment of patients with chronic hepatitis C might lead to efficient HCV eradication and hepatic improvement concomitantly evolving with favouring lipoprotein/apo metabolisms.

Eradication of hepatitis C virus is associated with the attenuation of steatosis as evaluated using a controlled attenuation parameter

Chronic hepatitis C virus (HCV) infection was shown to cause hepatic steatosis or suppression of serum lipid levels. However, little is known about the changes in hepatic steatosis following HCV eradication. We aimed to evaluate this issue using the controlled attenuation parameter (CAP), which was recently shown to provide a standardized non-invasive measure of hepatic steatosis. We enrolled 70 patients with chronic HCV infections and steatosis (CAP of over 248 dB/m) who had achieved a sustained viral response at 12 weeks after discontinuation of antiviral treatment using direct-acting antivirals (DAA). We then evaluated the state of hepatic steatosis before and after HCV eradication. We also investigated the changes in serum parameters such as cholesterol and glucose levels. The median value of CAP level decreased significantly after HCV eradication from 273 dB/m to 265 dB/m (P = 0.034). Also, LDL and HDL cholesterol levels increased significantly after HCV eradication (P = 0.002 and P = 0.027, respectively). In conclusion, a decrease in hepatic steatosis after HCV eradication with DAA was revealed in chronic hepatitis C patients with significant steatosis. Cancellation of the viral effect is a possible underlying cause of hepatic steatosis improvement and increase in HDL and LDL cholesterol levels.

Distribution of hepatitis C virus genotypes, hepatic steatosis and their correlation with clinical and virological factors in Pakistan

Background: Due to the inherently unstable nature of HCV, various genotypes have been identified. Steatosis is a histological feature in the progression of HCV-associated liver disease and has been shown to alter the host lipid metabolism. Objective: Assess the distribution of HCV genotypes in the two provinces of Pakistan, and determine the association of hepatic steatosis with altered clinical and virological factors in chronic HCV patients. Methods: One hundred twenty six chronic HCV patients (steatosis in 49 patients) were enrolled for qualitative analysis by PCR. Out of 126 ELISA and PCR positive samples, 119 (48 with hepatic steatosis) chronic HCV patients (mean age 42.0±13.3 years, mean body mass index (BMI) 24.2±4.1) were proved positive after PCR-based detection. Biochemical and virological factors such as HCV genotype, or glucose, in 119 CHC patients were determined and compared between patients with and without hepatic steatosis. Results: Out of 126 samples, 119 were HCV positive, where 58 (48.7%) were genotype 3a, 24 (20.2%) were 3b, 12 (10.1%) were 1a, eight (6.7%) were 2a, six (5.0%) were 1b, and one (0.8%) was 4. Furthermore, seven (5.9%) had a co-infection and three (2.5%) were untypable. BMI (p=0.004), genotype 3a (p<0.001), and triglycerides (p=0.002) were significantly associated with steatosis. It is noteworthy that cholesterol (p=0.281), glucose (p=0.305), lowdensity lipoprotein (p=0.101), high-density lipoprotein (p=0.129), alanine amino transferase (p=0.099), aspartate transaminase (p=0.177), bilirubin (p= 0.882), and age (p=0.846) showed non-significant association. Conclusion: Genotype 3a is the predominant genotype in Pakistan. Hepatic steatosis is quite frequent feature in HCV patients and strongly correlates with BMI, genotype 3a, and triglyceride contents in patients infected with HCV.

Association between serum aminotransferase enzymes–lipid profile ratio and spontaneous HCV clearance in blood donors

Aim: Study the role of the aminotransferase lipid profile ratio in the spontaneous clearance of HCV. Materials & methods: Blood samples from 68 blood donors were classified into three groups: negative for HCV antibodies (control group I), positive anti-HCV with negative HCV-RNA, (group II) and positive anti-HCV with positive HCV-RNA (group III). Results: A significant linear correlation was observed between the HCV-RNA levels and aminotransferase enzymes–lipid profile ratio as indicated by the values of (AST)/triglycerides (r = 0.577; p = 0.003) and ALT/triglycerides (r = 0.508; p < 0.009). AST/high-density lipoprotein had an area under the receiver operating characteristic curve of 0.72 for discriminating between nonspontaneous HCV-clearance from spontaneous HCV-clearance patients. Conclusion: AST/high-density lipoprotein can be used for the prediction of HCV clearance without treatment.

Ledipasvir/sofosbuvir treatment of hepatitis C virus is associated with reduction in serum apolipoprotein levels

The interaction of lipoproteins with hepatitis C virus (HCV) has pathogenic and therapeutic implications. Our aim was to evaluate changes in the apolipoprotein profile of patients with chronic hepatitis C during and after successful cure with ledipasvir and sofosbuvir (LDV/SOF) with and without ribavirin (RBV). One hundred HCV genotype 1 patients who had achieved SVR-12 after treatment with 12 weeks of LDV/SOF ± RBV were selected from the ION-1 clinical trial. Frozen serum samples from baseline, end of treatment and week 4 of follow-up were used to assay apolipoproteins (apoAI, apoAII, apoB, apoCII, apoCIII, apoE) using the Multiplex platform to assess for changes in the apolipoprotein levels. At the end of treatment compared to baseline, a significant reduction in apoAII levels (-14.97 ± 63.44 μg/mL, P = 0.0067) and apoE levels (-4.38 ± 12.19 μg/mL, P < 0.001) was noted. These declines from baseline in apoAII (-16.59 ±66.15 μg/mL, P = 0.0075) and apoE (-2.66 ± 12.64 μg/mL, P = 0.015) persisted at 4 weeks of post-treatment follow-up. In multivariate analysis, treatment with LDV/SOF + RBV was independently associated with reduction in apoE (beta = 5.31 μg/mL, P = 0.002) (compared to RBV-free LDV/SOF) (P < 0.05). In contrast, apoCII levels overall increased from baseline to end of treatment (+2.74 ±11.76 μg/mL, P = 0.03) and persisted at 4 weeks of follow-up (+4.46 ± 12.81 μg/mL from baseline, P = 0.0005). Subgroup analysis revealed an increase in apoCII during treatment only in patients receiving LDV/SOF without RBV (+5.52 ± 11.92 μg/mL, P = 0.0007) but not in patients receiving LDV/SOF + RBV (P = 0.638). Treatment with LDV/SOF ± RBV is associated with a persistent reduction in the apolipoprotein AII and E after achieving cure. These data suggest that treatment with LDV/SOF ± RBV may be associated with alterations in serum apolipoproteins which could potentially impact viral eradication.

Increased hepatic expression of miRNA-122 in patients infected with HCV genotype 3

Hepatitis C virus (HCV) infection affects approximately 3 % of the world population. HCV targets hepatic tissue, and most infected patients develop a chronic infection. Currently, studies have demonstrated an association between HCV-RNA replication and miR-122, the most abundant microRNA in the liver. Our aim was to evaluate liver and serum expression of miR-122 in patients infected with HCV genotypes 1 and 3, and to identify possible associations between miR-122 expression and lipid profiles, HCV viral load, apolipoproteins and liver enzymes. MicroRNAs were isolated from blood and liver tissue, and miR-122 expression was quantified by real-time PCR. HCV viral load was quantified by real-time PCR and HCV genotype, and serum biomarkers were obtained from medical report. The levels of miR-122 were higher in liver than those in blood from individuals infected with HCV genotypes 1 and 3 (p < 0.0001). The tissue levels of miR-122 were higher in subjects infected with HCV genotype 3 (6.22-fold, p < 0.001). A positive correlation was observed between the blood and hepatic levels of miR-122 in patients infected with HCV genotype 1 (r = 0.302, p = 0.026); in these patients, an inverse correlation was observed between serum apolipoprotein A-II (ApoA-II) levels and the blood (r = -0.330; p = 0.014) and hepatic (r = -0.311; p = 0.020) levels of miR-122. In patients infected with HCV genotype 3, there was a positive correlation between the hepatic miR-122 and the high-density lipoprotein-HDL (r = 0.412, p = 0.036) and insulin (r = 0.478, p = 0.044). Lipid metabolism proteins and miR-122 expression levels have different relations in HCV-3- and HCV-1-infected patients.

Role of the exogenous HCV core protein in the interaction of human hepatocyte proliferation and macrophage sub-populations

BACKGROUND

The core protein of hepatitis C virus (HCV) is found in the cytoplasm and nuclei of infected cells, including hepatocytes and other cells in the liver. The core protein could be secreted as well. Resident liver macrophages are dependent on the tissue micro-environment and external stimuli to differentiate M1 and M2 hypotypes with distinct functions, and increased expression of the nuclear transcription factor STAT3 was seen in M2-polarized macrophages. In contrast to proinflammatory M1 macrophages, M2 macrophages serve beneficial roles in chronic inflammation, immunosuppression, and tumorigenesis.

METHODS

Monocyte-derived human macrophage line (mTHP-1) was treated with the exogenous HCV core protein. Next, the mTHP-1 culture supernatant or cell pellets were added to culture media of normal human liver cell line (L02).

RESULTS

Only the culture supernatant stimulated L02 cells proliferation, which was associated with phosphorylated ERK expression. Core protein activated mTHP-1 cells showed enhanced pro- and anti-inflammatory cytokines secretion, which was accompanied by high expression of phosphorylated NF-κB105 and NF-κB65. However, phosphorylated STAT1, and STAT3, which are normally associated with M1 and M2 macrophage polarization, and cell surface expression of CD206, CD14, CD16, and CD86, were unaltered. A transwell co-culture system showed that only in mTHP-1 co-cultured with L02 in the presence of exogenous core protein, were higher levels of phosphorylated STAT3 and CD206 seen.

CONCLUSIONS

We showed L02 cells proliferation was accelerated by the culture supernatant of mTHP-1 cells treated with the exogenous HCV core protein. The exogenous core protein mediated the interaction between macrophages and hepatocytes in co-culture, which enhanced the expression of phosphorylated STAT3 and CD206 in macrophages.

Are human polyomaviruses co-factors for cancers induced by other oncoviruses?

Presently, 12 human polyomaviruses are known: BK polyomavirus (BKPyV), JCPyV, KIPyV, WUPyV, Merkel cell polyomavirus (MCPyV), HPyV6, HPyV7, Trichodysplasia spinulosa-associated polyomavirus, HPyV9, HPyV10, STLPyV and HPyV12. In addition, the non-human primate polyomavirus simian virus 40 (SV40) seems to circulate in the human population. MCPyV was first described in 2008 and is now accepted to be an etiological factor in about 80% of the rare but aggressive skin cancer Merkel cell carcinoma. SV40, BKPyV and JCPyV or part of their genomes can transform cells, including human cells, and induce tumours in animal models. Moreover, DNA and RNA sequences and proteins of these three viruses have been discovered in tumour tissue. Despite these observations, their role in cancer remains controversial. So far, an association between cancer and the other human polyomaviruses is lacking. Because human polyomavirus DNA has been found in a broad spectrum of cell types, simultaneous dwelling with other oncogenic viruses is possible. Co-infecting human polyomaviruses may therefore act as a co-factor in the development of cancer, including those induced by other oncoviruses. Reviewing studies that report co-infection with human polyomaviruses and other tumour viruses in cancer tissue fail to detect a clear link between co-infection and cancer. Directions for future studies to elaborate on a possible auxiliary role of human polyomaviruses in cancer are suggested, and the mechanisms by which human polyomaviruses may synergize with other viruses in oncogenic transformation are discussed.

Plasma triglyceride levels may modulate hepatitis C viral replication

BACKGROUND

Plasma and hepatic lipid abnormalities are frequent in hepatitis C infected individuals.

METHODS

Plasma lipid and medical records profiles were prospectively obtained in 130 consecutive individuals seen by a single hepatologist in a university liver disease clinic. The relationships between viral load, genotype, plasma lipid fractions, HDL, LDL particle number and particle size were examined.

RESULTS

Of 130 individuals studied, 74 had hepatitis C while 15 had NAFLD/NASH and 30 had alcohol related liver disease. The LDL particle number and LDL-C levels did not differ between those with and without hepatitis C although the number of small LDL particles was greater in those with hepatitis C infection. The HDL-C and total cholesterol levels were greater in those without hepatitis C than those with hepatitis C (P = 0.009). In contrast, the serum triglyceride level was greater in the hepatitis C viral group (P = 0.013). Importantly, the hepatitis C viral load regardless of the genotype correlated directly with the triglyceride and VLDL levels with r values of 0.73 and 0.84, respectively.

CONCLUSIONS

There are: (1) important differences in lipid classes, number and the size of lipid particles exist between hepatitis C virus infected and noninfected liver disease groups, (2) the serum total triglyceride and the LDL levels correlate significantly with the hepatitis C viral load and, (3) Serum triglyceride level may play an important role in viral replication. These data further suggest that therapies directed at lowering plasma triglyceride levels may enhance the efficacy of current antiviral treatment regimens.

Bridging the past and the future of virology: surface plasmon resonance as a powerful tool to investigate virus/host interactions

Despite decades of antiviral drug research and development, viruses still remain a top global healthcare problem. Compared to eukaryotic cells, viruses are composed by a limited numbers of proteins that, nevertheless, set up multiple interactions with cellular components, allowing the virus to take control of the infected cell. Each virus/host interaction can be considered as a therapeutical target for new antiviral drugs but, unfortunately, the systematic study of a so huge number of interactions is time-consuming and expensive, calling for models overcoming these drawbacks. Surface plasmon resonance (SPR) is a label-free optical technique to study biomolecular interactions in real time by detecting reflected light from a prism-gold film interface. Launched 20 years ago, SPR has become a nearly irreplaceable technology for the study of biomolecular interactions. Accordingly, SPR is increasingly used in the field of virology, spanning from the study of biological interactions to the identification of putative antiviral drugs. From the literature available, SPR emerges as an ideal link between conventional biological experimentation and system biology studies functional to the identification of highly connected viral or host proteins that act as nodal points in virus life cycle and thus considerable as therapeutical targets for the development of innovative antiviral strategies.

Lipid droplet binding of hepatitis C virus core protein genotype 3

Background. Hepatitis C virus (HCV) genotype 3 is known to cause steatosis (fatty liver) that is more frequent and severe than other genotypes. We previously identified sequence elements within genotype 3 HCV Core domain 3 that were sufficient for lipid accumulation. Aims. We examined various genotype 3 Core domains for lipid droplet localization and compared the lipid droplet binding regions of domain 2 with a genotype 1 isolate. Methods. We generated HCV Core domain constructs fused with green fluorescent protein and performed immunofluorescence to visualize lipid droplets. Results. Constructs containing HCV Core domain 2 are appropriately localized to lipid droplets with varying degrees of efficiency. When compared to genotype 1, there are polymorphisms within domain 2 that do not appear to alter lipid droplet localization. Conclusions. In summary, the differences in a steatosis-associated HCV Core genotype 3 isolate do not appear to involve altered lipid droplet localization.

Hepatitis C viral heterogeneity based on core gene and an attempt to design small interfering RNA against strains resistant to interferon in rawalpindi, pakistan

BACKGROUND

Global prevalence of Hepatitis C Virus (HCV) infection corresponds to about 130 million HCV positive patients worldwide. The only drug that effectively reduces viral load is interferon-α (IFN-α) and currently combination of IFN and ribavirin is the choice for treatment.

OBJECTIVES

The present study is aimed to resolve the genotypes based on core gene that might affect the response to interferon therapy. Furthermore an attempt was made to propose a powerful therapeutic approach by designing the siRNA from sequences of the same patients who remain resistant to IFN in this study.

PATIENTS AND METHODS

To achieve the objectives, a sequence analysis was performed in five HCV ELISA positive subjects who have completed IFN treatment. Neighbor Joining (NJ) method was used to study the evolutionary relationship. Atomic models were predicted using online software PROCHECK and i- TASSER.

RESULTS

Two new genotypes were reported for the first time namely 4a from suburban region of Rawalpindi and 6e from all over the Pakistan. According to Ramachandran plot, satisfactory atomic model was considered useful for further studies, i.e. to calculate HCV genotypes conservation at structural level, to find out critical binding sites for drug designing, or to silence those binding sites by using appropriate siRNA. Single siRNA can be used to inhibit HCV RNA synthesis against genotype 3 and 4, as the predicted siRNA were originated from the same domain in studied HCV core region in both genotypes.

CONCLUSIONS

We can conclude that any change or mutation in core region might be the cause of HCV strains to resist against IFN therapy. Therefore, further understanding of the complex mechanism involved in disrupting viral response to therapy would facilitate the development of more effective therapeutic regimens. Additionally, a single designed siRNA can be used as an alternative for current therapy against more than one resistant HCV genotypes.

Autophagy protects cells from HCV-induced defects in lipid metabolism

BACKGROUND & AIMS

Autophagy is a lysosome-mediated catabolic process that mediates degradation and recycling of all major components of eukaryotic cells. Different stresses, including viral and bacterial infection, induce autophagy, which can promote cell survival by removing the stress inducer or by attenuating its dangerous effects. High levels of autophagy occur during infection of cells with hepatitis C virus (HCV), but the clinical relevance of this process is not clear.

METHODS

Levels of autophagy were analyzed in liver biopsy samples from 22 patients with HCV infection using microtubule-associated protein-1 light chain 3 immunoblotting; associations with histological and metabolic parameters were evaluated by Pearson correlation analysis. We investigated the role of HCV-induced autophagy in lipid degradation in cells infected with the virus or replicons, and analyzed autophagosome contents by confocal microscopy and by measuring lipid levels after inhibition of autophagy by Beclin 1 knockdown or lysosome inhibitors.

RESULTS

In liver biopsy samples from patients with HCV, there was an inverse correlation between microvesicular steatosis and level of autophagy (r = -0.617; P = .002). HCV selectively induced autophagy of lipids in virus-infected and replicon cells. In each system, autophagosomes frequently colocalized with lipid deposits, mainly formed by unesterified cholesterol. Inhibition of the autophagic process in these cells significantly increased the induction of cholesterol accumulation by HCV.

CONCLUSIONS

Autophagy counteracts the alterations in lipid metabolism induced by HCV. Disruption of the autophagic process might contribute to development of steatosis in patients with HCV.

HCV and the hepatic lipid pathway as a potential treatment target

Atherosclerosis has been described as a liver disease of the heart [1]. The liver is the central regulatory organ of lipid pathways but since dyslipidaemias are major contributors to cardiovascular disease and type 2 diabetes rather than liver disease, research in this area has not been a major focus for hepatologists. Virus-host interaction is a continuous co-evolutionary process [2] involving the host immune system and viral escape mechanisms [3]. One of the strategies HCV has adopted to escape immune clearance and establish persistent infection is to make use of hepatic lipid pathways. This review aims to: • update the hepatologist on lipid metabolism • review the evidence that HCV exploits hepatic lipid pathways to its advantage • discuss approaches to targeting host lipid pathways as adjunctive therapy.

Lipoprotein component associated with hepatitis C virus is essential for virus infectivity

Many chronic hepatitis patients with hepatitis C virus (HCV) are observed to have a degree of steatosis which is a factor in the progression of liver diseases. Transgenic mice expressing HCV core protein develop liver steatosis before the onset of hepatocellular carcinoma, suggesting active involvement of HCV in the de-regulation of lipid metabolism in host cells. However, the role of lipid metabolism in HCV life cycle has not been fully understood until the establishment of in vitro HCV infection and replication system. In this review we focus on HCV production with regard to modification of lipid metabolism observed in an in vitro HCV infection and replication system. The importance of lipid droplet to HCV production has been recognized, possibly at the stage of virus assembly, although the precise mechanism of lipid droplet for virus production remains elusive. Association of lipoprotein with HCV in circulating blood in chronic hepatitis C patients is observed. In fact, HCV released from culture medium is also associated with lipoprotein. The fact that treatment of HCV fraction with lipoprotein lipase (LPL) abolished infectivity indicates the essential role of lipoprotein's association with virus particle in the virus life cycle. In particular, apolipoprotein E (ApoE), a component of lipoprotein associated with HCV plays a pivotal role in HCV infectivity by functioning as a virus ligand to lipoprotein receptor that also functions as HCV receptor. These results strongly suggest the direct involvement of lipid metabolism in the regulation of the HCV life cycle.

Extracellular hepatitis C virus core protein activates STAT3 in human monocytes/macrophages/dendritic cells via an IL-6 autocrine pathway

Hepatitis C virus (HCV) infection is highly efficient in the establishment of persistent infection, which leads to the development of chronic liver disease and hepatocellular carcinoma. Impaired T cell responses with reduced IFN-γ production have been reported to be associated with persistent HCV infection. Extracellular HCV core is a viral factor known to cause HCV-induced T cell impairment via its suppressive effect on the activation and induction of pro-inflammatory responses by antigen-presenting cells (APCs). The activation of STAT proteins has been reported to regulate the inflammatory responses and differentiation of APCs. To further characterize the molecular basis for the regulation of APC function by extracellular HCV core, we examined the ability of extracellular HCV core to activate STAT family members (STAT1, -2, -3, -5, and -6). In this study, we report the activation of STAT3 on human monocytes, macrophages, and dendritic cells following treatment with extracellular HCV core as well as treatment with a gC1qR agonistic monoclonal antibody. Importantly, HCV core-induced STAT3 activation is dependent on the activation of the PI3K/Akt pathway. In addition, the production of multifunctional cytokine IL-6 is essential for HCV core-induced STAT3 activation. These results suggest that HCV core-induced STAT3 activation plays a critical role in the alteration of inflammatory responses by APCs, leading to impaired anti-viral T cell responses during HCV infection.

Role of insulin resistance and hepatic steatosis in the progression of fibrosis and response to treatment in hepatitis C

Hepatitis C is a common cause of chronic viral infection of the liver. It is associated with insulin resistance and the development of type 2 diabetes mellitus. It is also associated with the development of hepatic steatosis. The presence of hepatic steatosis is associated with an increased risk of having hepatic fibrosis. This is also associated with the severity of insulin resistance. These findings are specifically germane for those with genotype1 infection. Genotype 3 infection independently causes steatosis and successful treatment of the virus is followed by resolution of steatosis. In genotype 1 infection, the presence of hepatic steatosis is also a risk factor for failure to respond to pegylated interferon and ribavirin therapy. Unfortunately efforts to treat insulin resistance prior to antiviral therapy have not been very successful. Newer efforts focused on the role of specific micro RNAs in mediating the metabolic effects of hepatitis C virus infection may provide to ameliorate the metabolic risks of HCV infection.

Inhibition of core gene of HCV 3a genotype using synthetic and vector derived siRNAs

Background

Hepatitis C virus (HCV) is a major causative agent of liver associated diseases throughout the world, with genotype 3a responsible for most of the cases in Pakistan. Due to the limited efficiency of current therapy, RNA interference (RNAi) a novel regulatory and powerful silencing approach for molecular therapeutics through a sequence-specific RNA degradation process represents an alternative option.

Results

The current study was purposed to assess and explore the possibility of RNAi to silence the HCV-3a Core gene expression, which play complex role in regulation of cell growth and host genes expression essential for infectivity and disease progression. To identify the potent siRNA target sites, 5 small interfering RNAs (siRNAs) against Core gene were designed and in vitro transcribed after consensus sequence analysis of different HCV-3a isolates. Antiviral effects of siRNAs showed upto 80% inhibition of Core gene expression by different siRNAs into Huh-7 cells as compared with Mock transfected and control siRNAs treated cells. For long lasting effect of siRNAs, vector based short hairpin siRNAs (shRNAs) were designed and tested against HCV-3a Core which resulted in a similar pattern of inhibition on RNA and protein expression of HCV Core as synthetic siRNAs. Furthermore, the efficacy of cell culture tested siRNA and shRNA, were evaluated for inhibition of HCV replication in HCV infected serum inoculated Huh-7 cells and a significant decrease in HCV viral copy number was observed.

Conclusions

Our results support the possibility of using consensus siRNA and shRNA-based molecular therapy as a promising strategy in effective inhibition of HCV-3a genotype.

Role of Hepatitis C virus core protein in viral-induced mitochondrial dysfunction

Hepatitis C virus (HCV) infection results in several changes in mitochondrial function including increased reactive oxygen species (ROS) production and greater sensitivity to oxidant, Ca(2+) and cytokine-induced cell death. Prior studies in protein over-expression systems have shown that this effect can be induced by the core protein, but other viral proteins and replication events may contribute as well. To evaluate the specific role of core protein in the context of viral replication and infection, we compared mitochondrial sensitivity in Huh7-derived HCV replicon bearing cells with or without core protein expression with that of cells infected with the JFH1 virus strain. JFH1 infection increased hydrogen peroxide production and sensitized cells to oxidant-induced loss of mitochondrial membrane potential and cell death. An identical phenomenon occurred in genome-length replicons-bearing cells but not in cells bearing the subgenomic replicons lacking core protein. Both cell death and mitochondrial depolarization were Ca(2+) dependent and could be prevented by Ca(2+) chelation. The difference in the mitochondrial response of the two replicon systems could be demonstrated even in isolated mitochondria derived from the two cell lines with the 'genome-length' mitochondria displaying greater sensitivity to Ca(2+) -induced cytochrome c release. In vitro incubation of 'subgenomic' mitochondria with core protein increased oxidant sensitivity to a level similar to that of mitochondria derived from cells bearing genome-length replicons. These results indicate that increased mitochondrial ROS production and a reduced threshold for Ca(2+) and ROS-induced permeability transition is a characteristic of HCV infection. This phenomenon is a direct consequence of core protein interactions with mitochondria and is present whenever core is expressed, either in infection, full-length replicon-bearing cells, or in over-expression systems.

Structure and dynamics changes induced by 2,2,2-trifluoro-ethanol (TFE) on the N-terminal half of hepatitis C virus core protein

The Core protein of hepatitis C virus is involved in several interactions other than the encapsidation of viral RNA. We recently proposed that this is related to the fact that the N-terminal half of this protein (C82) is an intrinsically unstructured protein (IUP) domain. IUP domains can adopt a secondary structure when they are interacting with another molecule, such as a nucleic acid or a protein. It is also possible to mimic these conditions by modifying the environment of the protein. We investigated the propensity of this protein to fold as a function of salt concentration, detergent, pH, and 2,2,2-trifluoro-ethanol (TFE); only the addition of TFE resulted in a structural change. The effect of TFE addition was studied by circular dichroism, structural, and dynamic data obtained by NMR. The data indicate that C82 can adopt an alpha-helical structure; this conformation is likely relevant to one of the functional roles of the HCV Core protein.

A disulfide-bonded dimer of the core protein of hepatitis C virus is important for virus-like particle production

Hepatitis C virus (HCV) core protein forms the nucleocapsid of the HCV particle. Although many functions of core protein have been reported, how the HCV particle is assembled is not well understood. Here we show that the nucleocapsid-like particle of HCV is composed of a disulfide-bonded core protein complex (dbc-complex). We also found that the disulfide-bonded dimer of the core protein (dbd-core) is formed at the endoplasmic reticulum (ER), where the core protein is initially produced and processed. Mutational analysis revealed that the cysteine residue at amino acid position 128 (Cys128) of the core protein, a highly conserved residue among almost all reported isolates, is responsible for dbd-core formation and virus-like particle production but has no effect on the replication of the HCV RNA genome or the several known functions of the core protein, including RNA binding ability and localization to the lipid droplet. The Cys128 mutant core protein showed a dominant negative effect in terms of HCV-like particle production. These results suggest that this disulfide bond is critical for the HCV virion. We also obtained the results that the dbc-complex in the nucleocapsid-like structure was sensitive to proteinase K but not trypsin digestion, suggesting that the capsid is built up of a tightly packed structure of the core protein, with its amino (N)-terminal arginine-rich region being concealed inside.

Hepatitis C: the complications of immune dysfunction

Hepatitis C virus (HCV) infection has been linked to numerous diseases of immune dysfunction, including, but not limited to, essential mixed cryoglobulinemia and non-Hodgkin's lymphoma. Clinical studies support these associations and treatment of the underlying HCV infection has been variably successful. Recent studies, focusing on the role of HCV gene products, have discovered evidence of dysregulated responses in multiple aspects of host immunity that may be contributing to the genesis of these diseases. Novel treatments that target these areas of dysregulation offer hope for improved therapy for the diseases associated with immunodysregulation by HCV.

Functional characterization of core genes from patients with acute hepatitis C virus infection

BACKGROUND

The hepatitis C virus (HCV) core protein is implicated in diverse aspects of HCV-induced pathogenesis. There is a paucity of information on core in acute hepatitis C infection.

METHODS

We analyzed core gene sequences and protein functions from 13 patients acutely infected with HCV genotype 1.

RESULTS

Although core isolates differed slightly between patients, core quasispecies were relatively homogeneous within each patient. In 2 of 4 patients studied temporally, core quasispecies did not change over time. Comparison with more than 2700 published core isolates indicated that amino acid changes from a prototype reference strain found in acute core isolates were present in chronically infected persons at low frequency (6.4%; range, 0%-32%). Core isolates associated with lipid droplets to similar degrees in Huh7 cells. Core diffusion in cells was not affected by nonconservative changes F130L and G161S in the lipid targeting domain of core. Core isolates inhibited interferon-stimulated response element- and nuclear factor kappaB-dependent transcription and tumor necrosis factor alpha-induced nuclear translocation of nuclear factor kappaB and were also secreted from Huh7 cells.

CONCLUSIONS

The data suggest that upon transmission, core quasispecies undergo genetic homogenization associated with amino acid changes that are rarely found in chronic infection and that, despite genetic variation, acute core isolates retain similar functions in vitro.

Role of the receptor for the globular domain of C1q protein in the pathogenesis of hepatitis C virus-related cryoglobulin vascular damage

Mixed cryoglobulinemia (MC) is a lymphoproliferative disorder observed in approximately 10 to 15% of hepatitis C virus (HCV)-infected patients. Circulating, nonenveloped HCV core protein, which has been detected in cryoprecipitable immune complexes, interacts with immunocytes through the receptor for the globular domain of C1q protein (gC1q-R). In this study, we have evaluated circulating gC1q-R levels in chronically HCV-infected patients, with and without MC. These levels were significantly higher in MC patients than in those without MC and in healthy controls and paralleled specific mRNA expression in PBL. Soluble gC1q-R circulates as a complexed form containing both C1q and HCV core proteins. Higher serum gC1q-R levels negatively correlated with circulating concentrations of the C4d fragment. The presence of sequestered C4d in the vascular bed of skin biopsies from MC patients was indicative of in situ complement activation. In vitro studies showed that release of soluble gC1q-R is regulated by HCV core-mediated inhibition of cell proliferation. Our results indicate that up-regulation of gC1q-R expression is a distinctive feature of MC, and that dysregulated shedding of C1q-R molecules contributes to vascular cryoglobulin-induced damage via the classic complement-mediated pathway.

Hepatitis C virus-induced hepatocarcinogenesis

Although there is strong evidence that hepatitis C virus (HCV) is one of the leading causes of hepatocellular carcinoma (HCC), there is still much to understand regarding the mechanism of HCV-induced transformation. While liver fibrosis resulting from long-lasting chronic inflammation and liver regeneration resulting from immune-mediated cell death are likely factors that contribute to the development of HCC, the direct role of HCV proteins remains to be determined. In vitro studies have shown that HCV expression may interfere with cellular functions that are important for cell differentiation and cell growth. However, most studies were performed in artificial models which can only give clues for potential mechanisms that need to be confirmed in more relevant models. Furthermore, the difficulty to identify HCV proteins and infected liver cells in patients, contributes to the complexity of our current understanding. For these reasons, there is currently very little experimental evidence for a direct oncogenic role of HCV. Further studies are warranted to clarify these issues.

The hepatitis C virus core protein contains a BH3 domain that regulates apoptosis through specific interaction with human Mcl-1

The hepatitis C virus (HCV) core protein is known to modulate apoptosis and contribute to viral replication and pathogenesis. In this study, we have identified a Bcl-2 homology 3 (BH3) domain in the core protein that is essential for its proapoptotic property. Coimmunoprecipitation experiments showed that the core protein interacts specifically with the human myeloid cell factor 1 (Mcl-1), a prosurvival member of the Bcl-2 family, but not with other prosurvival members (Bcl-X(L) and Bcl-w). Moreover, the overexpression of Mcl-1 protects against core-induced apoptosis. By using peptide mimetics, core was found to release cytochrome c from isolated mitochondria when complemented with Bad. Thus, core is a bona fide BH3-only protein having properties similar to those of Noxa, a BH3-only member of the Bcl-2 family that binds preferentially to Mcl-1. There are three critical hydrophobic residues in the BH3 domain of the core protein, and they are essential for the proapoptotic property of the core protein. Furthermore, the genotype 1b core protein is more effective than the genotype 2a core protein in inducing apoptosis due to a single-amino-acid difference at one of these hydrophobic residues (residue 119). Replacing this residue in the J6/JFH-1 infectious clone (genotype 2a) with the corresponding amino acid in the genotype 1b core protein produced a mutant virus, J6/JFH-1(V119L), which induced significantly higher levels of apoptosis in the infected cells than the parental J6/JFH-1 virus. Furthermore, the core protein of J6/JFH-1(V119L), but not that of J6/JFH-1, interacted with Mcl-1 in virus-infected cells. Taken together, the core protein is a novel BH3-only viral homologue that contributes to the induction of apoptosis during HCV infection.

Access of viral proteins to mitochondria via mitochondria-associated membranes

By exploiting host cell machineries, viruses provide powerful tools for gaining insight into cellular pathways. Proteins from two unrelated viruses, human CMV (HCMV) and HCV, are documented to traffic sequentially from the ER into mitochondria, probably through the mitochondria-associated membrane (MAM) compartment. The MAM are sites of ER-mitochondrial contact enabling the direct transfer of membrane bound lipids and the generation of high calcium (Ca2+) microdomains for mitochondria signalling and responses to cellular stress. Both HCV core protein and HCMV UL37 proteins are associated with Ca2+ regulation and apoptotic signals. Trafficking of viral proteins to the MAM may allow viruses to manipulate a variety of fundamental cellular processes, which converge at the MAM, including Ca2+ signalling, lipid synthesis and transfer, bioenergetics, metabolic flow, and apoptosis. Because of their distinct topologies and targeted MAM sub-domains, mitochondrial trafficking (albeit it through the MAM) of the HCMV and HCV proteins predictably involves alternative pathways and, hence, distinct targeting signals. Indeed, we found that multiple cellular and viral proteins, which target the MAM, showed no apparent consensus primary targeting sequences. Nonetheless, these viral proteins provide us with valuable tools to access the poorly characterised MAM compartment, to define its cellular constituents and describe how virus infection alters these to its own end. Furthermore, because proper trafficking of viral proteins is necessary for their function, discovering the requirements for MAM to mitochondrial trafficking of essential viral proteins may provide novel targets for the rational design of anti-viral drugs.

Treatment of hepatitis C virus with peg-interferon and ribavirin combination therapy significantly affects lipid metabolism

AIM

We investigated lipid metabolism in patients with chronic hepatitis C virus (HCV), serotype 1, undergoing combination therapy with PEG-IFN alpha-2b (PEG-IFN) and ribavirin (RBV).

METHODS

A total of 185 patients with chronic HCV (HCV serotype 1; HCV RNA levels >/= 100 KIU/mL) who received a combination of PEG-IFN and RBV were enrolled.

RESULTS

Sustained virological response (SVR) was obtained in 82 cases (44.3%). The median age, red blood cell and platelet counts differed significantly between the SVR and non-SVR groups before treatment. However there was no significant difference between total cholesterol (TC), LDL-cholesterol (LDL-C) and triglyceride (TG) levels before treatment. TC and LDL-C levels decreased during the treatment in both groups. In the SVR group, TC and LDL-C levels increased quickly after the end of the treatment and were higher than those before treatment. On the other hand, TC and LDL-C levels returned to pretreatment levels in the non-SVR group and were significantly lower than in the SVR group. TG levels were elevated in both groups after the beginning of treatment. After the end of treatment, this elevation persisted in the SVR group, while TG levels returned to pre-treatment levels in the non-SVR group. There was a significant difference in TG levels at 24 weeks after the end of the treatment between the 2 groups. In the non-SVR group some patients achieved normalization of ALT (alanine aminotransferase) but persistence of normal ALT levels did not contribute to the increase of TC and TG.

CONCLUSION

TC, LDL-C and TG levels increase only in patients with HCV, serotype 1, undergoing combination therapy when a SVR is achieved.

Silibinin is a potent antiviral agent in patients with chronic hepatitis C not responding to pegylated interferon/ribavirin therapy

BACKGROUND & AIMS

Oral Silibinin (SIL) is widely used for treatment of hepatitis C, but its efficacy is unclear. Substantially higher doses can be administered intravenously (IV).

METHODS

Pedigreed nonresponders to full-dose pegylated (Peg)-interferon/ribavirin (PegIFN/RBV) were studied. First, 16 patients received 10 mg/kg/day SIL IV (Legalon Sil; Madaus, Köln, Germany) for 7 days. In a subsequent dose-finding study, 20 patients received 5, 10, 15, or 20 mg/kg/day SIL for 14 days. In both protocols, PegIFN alpha-2a/RBV were started on day 8. Viral load was determined daily.

RESULTS

Unexpectedly, in the first study, HCV-RNA declined on IV SIL by 1.32 +/- 0.55 log (mean +/- SD), P < .001 but increased again in spite of PegIFN/RBV after the infusion period. The viral load decrease was dose dependent (log drop after 7 days SIL: 0.55 +/- 0.5 [5 mg/kg, n = 3], 1.41 +/- 0.59 [10 mg/kg, n = 19], 2.11 +/- 1.34 [15 mg/kg, n = 5], and 3.02 +/- 1.01 [20 mg/kg, n = 9]; P < .001), decreased further after 7 days combined SIL/PegIFN/RBV (1.63 +/- 0.78 [5 mg/kg, n = 3], 4.16 +/- 1.28 [10 mg/kg, n = 3], 3.69 +/- 1.29 [15 mg/kg, n = 5], and 4.85 +/- 0.89 [20 mg/kg, n = 9]; P < .001), and became undetectable in 7 patients on 15 or 20 mg/kg SIL, at week 12. Beside mild gastrointestinal symptoms, IV SIL monotherapy was well tolerated.

CONCLUSIONS

IV SIL is well tolerated and shows a substantial antiviral effect against HCV in nonresponders.

Expression of apolipoprotein C-IV is regulated by Ku antigen/peroxisome proliferator-activated receptor gamma complex and correlates with liver steatosis

BACKGROUND/AIMS

We previously reported that hepatitis C virus (HCV) core protein up regulated transcription of apolipoprotein C-IV (ApoC-IV, 10.7-fold increase), a member of the apolipoprotein family implicated in liver steatosis. Here, we identified host transcription factors regulating the ApoC-IV gene expression.

METHODS

Transcriptional regulators were identified by DNA affinity purification and steatosis was detected by oil red O staining and triglyceride assay.

RESULTS

We defined a 163-bp ApoC-IV promoter as a core protein responsive element, and identified Ku antigen complex (Ku70 and Ku80) as well as nuclear receptors PPARgamma/RXRalpha as key regulators of ApoC-IV gene expression. Both Ku70 overexpression and PPARgamma agonist significantly increased ApoC-IV promoter activity; conversely, Ku70 silencing or mutation of PPARgamma binding site diminished the ApoC-IV promoter activity. Interestingly, transient transfection of ApoC-IV cDNA into a human hepatoma cell line was able to trigger moderate lipid accumulation. In agreement with this in vitro study, ApoC-IV transcript level was increased in HCV infected livers which correlated with triglyceride accumulation.

CONCLUSIONS

ApoC-IV overexpression may perturb lipid metabolism leading to lipid accumulation. HCV core protein may modulate ApoC-IV expression through Ku antigen and PPARgamma/RXRalpha complex.

Hepatitis C infection and nonalcoholic fatty liver disease

In hepatitis C virus (HCV) infection, significant hepatic steatosis or superimposed nonalcoholic steatohepatitis is associated with disease severity and poor response to antiviral therapy. Nonalcoholic fatty liver disease (NAFLD) and HCV are common causes of chronic liver disease in Western countries and are strongly linked to concurrent obesity, insulin resistance, and the metabolic syndrome. With the escalating prevalence of obesity in North America, insulin resistance and the metabolic syndrome are major public health problems that have a significant impact on morbidity and mortality associated with NAFLD and HCV. This article focuses on the current understanding of the interplay between host and viral factors that are involved in the interaction between NAFLD and HCV.

Apolipoprotein B-dependent hepatitis C virus secretion is inhibited by the grapefruit flavonoid naringenin

Hepatitis C virus (HCV) infects over 3% of the world population and is the leading cause of chronic liver disease worldwide. HCV has long been known to associate with circulating lipoproteins, and its interactions with the cholesterol and lipid pathways have been recently described. In this work, we demonstrate that HCV is actively secreted by infected cells through a Golgi-dependent mechanism while bound to very low density lipoprotein (vLDL). Silencing apolipoprotein B (ApoB) messenger RNA in infected cells causes a 70% reduction in the secretion of both ApoB-100 and HCV. More importantly, we demonstrate that the grapefruit flavonoid naringenin, previously shown to inhibit vLDL secretion both in vivo and in vitro, inhibits the microsomal triglyceride transfer protein activity as well as the transcription of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase and acyl-coenzyme A:cholesterol acyltransferase 2 in infected cells. Stimulation with naringenin reduces HCV secretion in infected cells by 80%. Moreover, we find that naringenin is effective at concentrations that are an order of magnitude below the toxic threshold in primary human hepatocytes and in mice.

CONCLUSION

These results suggest a novel therapeutic approach for the treatment of HCV infection.

Role of complement in immune regulation and its exploitation by virus

Complement is activated during the early phase of viral infection and promotes destruction of virus particles as well as the initiation of inflammatory responses. Recently, complement and complement receptors have been reported to play an important role in the regulation of innate as well as adaptive immune responses during infection. The regulation of host immune responses by complement involves modulation of dendritic cell activity in addition to direct effects on T-cell function. Intriguingly, many viruses encode homologs of complement regulatory molecules or proteins that interact with complement receptors on antigen-presenting cells and lymphocytes. The evolution of viral mechanisms to alter complement function may augment pathogen persistence and limit immune-mediated tissue destruction. These observations suggest that complement may play an important role in both innate and adaptive immune responses to infection as well as virus-mediated modulation of host immunity.

Altered expression patterns of lipid metabolism genes in an animal model of HCV core-related, nonobese, modest hepatic steatosis

BACKGROUND

Because the gene expression patterns of nonobese hepatic steatosis in affected patients remain unclear, we sought to explore these patterns using an animal model of nonobese hepatic steatosis.

METHODS

We developed mice that conditionally express the hepatitis C virus (HCV) core protein regulated by the tetracycline transactivator (tTA). Microarray analyses and reverse-transcription polymerase chain reaction were performed using liver samples of both the double transgenic mice (DTM), which express both the HCV core and tTA, and single transgenic mice (STM), which express tTA alone, at 2 months of age. Functional categories of genes with altered expression were classified using gene ontology programs. Serum glucose, lipid levels, and systemic blood pressure were also measured.

RESULTS

Approximately 20-30% of hepatocytes from the DTM were steatotic. No significant differences were observed in the serum glucose, lipid content, or blood pressure levels between the DTM and STM. Gene expression analyses revealed Sterol-regulatory element-binding protein (SREBP) pathway activation and dysregulation of the following genes involved in lipid metabolism: 3-hydroxy-3-methylglutaryl-coenzyme A synthase 1, Apolipoprotein AII, Apolipoprotein CI, acyl-CoA thioesterase I, and fatty acid binding protein 1; in mitochondrial function: solute carrier family 25 member 25 and cytochrome c oxidase subunit II; in immune reaction: complement component 3, lymphocyte antigen 6 complex, locus A, lymphocyte antigen 6 complex, locus C, lymphocyte antigen 6 complex, locus D, and lymphocyte antigen 6 complex, locus E.

CONCLUSION

Some genes of lipid metabolism, mitochondrial function, and immune reaction and the SREBP pathway are involved in HCV core-related, nonobese, modest hepatic steatosis.

Modulation of signaling pathways by RNA virus capsid proteins

Capsid proteins are structural components of virus particles. They are nucleic acid-binding proteins whose main recognized function is to package viral genomes into protective structures called nucleocapsids. Research over the last 10 years indicates that in addition to their role as genome guardians, viral capsid proteins modulate host cell signaling networks. Disruption or alteration of intracellular signaling pathways by viral capsids may benefit replication of the virus by affecting innate immunity and in some cases, may underlie disease progression. In this review, we describe how the capsid proteins from medically relevant RNA viruses interact with host cell signaling pathways.

Role of hepatitis C virus proteins (C, NS3, NS5A) in hepatic oncogenesis

In recent years, the effects of hepatitis C virus (HCV) proteins on hepatocarcinogenesis have undergone intense investigations. The potentially oncogenic proteins include at least three HCV proteins: core (C) protein, NS3, and NS5A. Several authors indicated relationships between subcellular localization, concentration, a specific molecular form of the proteins (full length, truncated, phosphorylated), the presence of specific domains (the nuclear localization signal homologous to e.g. Bcl-2) and their effects on the mechanisms linked to oncogenesis. The involvement of all the proteins has been described as being in control of the cell cycle, through interactions with key proteins of the process (p53, p21, cyclins, proliferating cell nuclear antigen), transcription factors, proto-oncogenes, growth factors/cytokines and their receptors, and proteins linked to the apoptotic process. Untilnow, the involvement of the core protein of HCV in liver carcinogenesis is the most recognized. One of the most common proteins affected by HCV proteins is the p53 tumor-suppressor protein. The p21/WAF1 gene is a major target of p53, and the effect of HCV proteins on the gene is frequently considered in parallel. The results of studies on the effects of HCV proteins on the apoptotic process are controversial. This work summarizes the information collected thus far in the field of HCV molecular virology and principal intracellular signaling pathways in which HCV oncogenic proteins are involved.

Apolipoprotein-AII concentrations are associated with liver steatosis in patients with chronic hepatitis C

It has been shown that the hepatitis C virus (HCV) core protein reduces the activity of the microsomal triglyceride transfer protein (MTP) and could lead to steatosis in HCV-infected patients. Experimentally, apolipoprotein-AII (apoAII), which restores triglyceride secretion altered by the HCV core protein, could be protective against HCV steatosis. On the other hand, increasing plasma concentrations of mouse apoAII in transgenic mice produced several aspects of insulin-resistance syndrome, which also is implicated in the pathogenesis of HCV steatosis. This study was designed to investigate the role of apoAII in HCV-related steatosis in humans. Sixty-five hospitalized patients with chronic HCV were included in this study to assess the effects of apoAII, body mass index (BMI), age, insulin sensibility (HOMA), and leptin level on steatosis. Steatosis was observed in 55.3% of patients. Apo-AII was significantly associated with HOMA and with leptin concentrations. In univariate analyses, age, BMI, increased leptin level, increased HOMA, and increased apoAII concentration were associated with steatosis. In multivariate analysis, steatosis was associated with apoAII concentration, age, gender, and BMI. Contrary to previous hypotheses, apoAII is not a protective factor against HCV steatosis but is significantly associated with the development of liver steatosis. The fact that the plasma levels of apoAII correlate with HOMA and leptin levels in HCV-infected patients suggests that apoAII may contribute to hepatic steatosis progression in relationship to visceral obesity, insulin resistance, and metabolism of triglyceride-rich lipoproteins.

Antiproliferative effect of hepatitis C virus on mitogen-stimulated peripheral blood mononuclear cells: potential role in viral persistence in Egyptian patients

OBJECTIVES

We aimed to study the effect of hepatitis C virus (HCV) and sera of chronic HCV patients on phytohemagglutinin (PHA)-stimulated normal donor PBMCs and to study the effect of chronic HCV infection on some cytokine profile.

SUBJECTS AND METHODS

(3)H-Thymidine uptake was utilized to study effect of pelleted virus and patients sera on PBMCs proliferation in vitro. The study included 337 Egyptian chronic liver patients from Ain Shams University Hospitals and 90 healthy control subjects. The patients' group included chronic hepatitis C (250 subjects), and other chronic liver diseases (87 subjects). All subjects' sera were subjected to RT-PCR for HCV RNA detection, IL-4, IL-1beta, and TNF-alpha measurement by EIA, and biochemical measurement of ALT and albumin.

RESULTS

Treatment of PHA-stimulated normal donor PBMCs with pelleted virus led to decrease (dose response) in their rate of proliferation. This was partially reversed after addition of HCV RNA positive patients' sera. HCV RNA positive patients were significantly higher in IL-4 and ALT, and lower in IL-1beta and albumin than HCV RNA negative patients.

CONCLUSION

HCV infection suppresses early immune response. This leads to increased IL-4 Th2 cytokine.

Mapping of the interacting domains of hepatitis C virus core protein and the double-stranded RNA-activated protein kinase PKR

Hepatitis C virus (HCV) core protein has been shown to exhibit several biological properties which suggest an important role in liver pathogenesis and carcinogenesis. During a previous study, we showed that core mutants, isolated from tumour, could directly interact with PKR and maintain it in an activated form. In the present report, we have further investigated this interaction and mapped the core and PKR domains involved. Using glutathion S-transferase fusion protein harbouring the different domains of core or PKR, we determined that the N-terminal 1-58 amino acid (aa) of core protein and the N-terminal 1-180 aa of PKR are responsible for this direct interaction. Using this system we also confirmed that the core-PKR interaction induced PKR autophosphorylation. Furthermore, we found that core protein co-localized and co-immunoprecipitated with PKR in cells expressing a full-length HCV replicon, thus confirming that this interaction occurs when all HCV proteins are expressed. Considering that the activation of PKR has been observed in some cancer cell lines and tissues, it suggests that, depending on the cellular context, PKR may stimulate or inhibit cell proliferation. The precise mapping of core-PKR interaction provides new data to study the molecular mechanism underlying HCV pathogenesis.

Significance of hepatitis C virus core protein in the diagnosis of hepatitis C virus infection in different liver diseases

The present article describes the presence of hepatitis C virus (HCV) core protein in relation to HCV antibody in different types of liver diseases caused by hepatitis viral infections. One hundred thirty patients with various types of liver diseases, including those with acute viral hepatitis (n = 50), chronic viral hepatitis (n = 30), cirrhosis of the liver (n = 30), and fulminant hepatic failure (n = 20), were analyzed for HCV core protein, HCV-ribonucleic acid (RNA) and anti-HCV antibodies using enzyme immunoassays and reverse transcriptase-polymerase chain reaction. All patients were also simultaneously analyzed for other hepatitis markers to diagnose hepatitis A to E in all cases. Patients with HCV infection were additionally tested for HCV core protein and HCV-RNA. The results of analysis demonstrated the presence of hepatitis B, C, and E in different proportions of patients with these liver diseases. Hepatitis A and D infections were absent in all cases. Analysis of sera from acute viral hepatitis demonstrated the presence of HCV core protein, HCV-RNA, anti-HCV antibodies, and both core protein and anti-HCV together in 18%, 16%, 6%, and 2% of cases, respectively. In fulminant hepatic failure patients, these markers were recorded in 20%, 10%, 10%, and 5% of cases, respectively. In the chronic viral hepatitis group, the pattern was reversed, and their presence was recorded in 13.3%, 13.3%, 46.6%, and 10% of cases, respectively. Similarly, in cirrhosis patients, these markers were noted in 23.3%, 23.3%, 23.3%, and 13.3% of cases, respectively. None of the control sera were positive for any hepatitis marker. The significance of HCV core protein in relation to HCV-RNA and anti-HCV for the diagnosis of HCV infection in different liver diseases has been discussed.

Repression of interferon regulatory factor 1 by hepatitis C virus core protein results in inhibition of antiviral and immunomodulatory genes

Hepatitis C virus (HCV) proteins are known to interfere at several levels with both innate and adaptive responses of the host. A key target in these effects is the interferon (IFN) signaling pathway. While the effects of nonstructural proteins are well established, the role of structural proteins remains controversial. We investigated the effect of HCV structural proteins on the expression of interferon regulatory factor 1 (IRF-1), a secondary transcription factor of the IFN system responsible for inducing several key antiviral and immunomodulatory genes. We found substantial inhibition of IRF-1 expression in cells expressing the entire HCV replicon. Suppression of IRF-1 synthesis was mainly mediated by the core structural protein and occurred at the transcriptional level. The core protein in turn exerted a transcriptional repression of several interferon-stimulated genes, targets of IRF-1, including interleukin-15 (IL-15), IL-12, and low-molecular-mass polypeptide 2. These data recapitulate in a unifying mechanism, i.e., repression of IRF-1 expression, many previously described pathogenetic effects of HCV core protein and suggest that HCV core-induced IRF-1 repression may play a pivotal role in establishing persistent infection by dampening an effective immune response.

Enhancement of de novo fatty acid biosynthesis in hepatic cell line Huh7 expressing hepatitis C virus core protein

Hepatitis C virus (HCV) core protein plays important roles in the pathogeneses of liver steatosis as well as hepatocellular carcinomas due to HCV infection. In this study, we examined de novo fatty acid biosynthesis in hepatic cell line Huh7 cells expressing HCV core protein. The rate of metabolic labeling of cellular fatty acids with [(3)H]acetate in core-expressing (Uc39-6) cells was ca. 1.5-fold higher than that in non-expressing (Uc321) cells. The enzyme activities responsible for fatty acid biosynthesis were assayed in vitro. Cytosolic acetyl-CoA carboxylase activity in Uc39-6 cells was ca. 1.6-fold higher than that in Uc321 cells. On the other hand, cytosolic fatty acid synthase activity in Uc39-6 cells was only slightly higher than that in Uc321 cells. Immunoblot analysis of acetyl-CoA carboxylase 1 (ACC1), which is a rate-limiting enzyme for fatty acid biosynthesis, revealed a higher expression level of the protein in Uc39-6 cells than in Uc321 cells. The ACC1 mRNA content in Uc39-6 cells was 1.4-fold higher than that in Uc321 cells. These results strongly suggest that enhancement of fatty acid biosynthesis in core-expressing cells is caused by increased expression of fatty acid biosynthetic enzymes, especially ACC1. Up-regulation of de novo fatty acid biosynthesis by HCV core protein may affect cellular lipid metabolism, resulting in neutral lipid accumulation in HCV-infected cells.