Transcriptional activation of the interleukin-2 promoter by hepatitis C virus core protein

Probing effects of the SARS-CoV-2 E protein on membrane curvature and intracellular calcium

SARS-CoV-2 contains four structural proteins in its genome. These proteins aid in the assembly and budding of new virions at the ER-Golgi intermediate compartment (ERGIC). Current fundamental research efforts largely focus on one of these proteins – the spike (S) protein. Since successful antiviral therapies are likely to target multiple viral components, there is considerable interest in understanding the biophysical role of its other structural proteins, in particular structural membrane proteins. Here, we have focused our efforts on the characterization of the full-length envelope (E) protein from SARS-CoV-2, combining experimental and computational approaches. Recombinant expression of the full-length E protein from SARS-CoV-2 reveals that this membrane protein is capable of independent multimerization, possibly as a tetrameric or smaller species. Fluorescence microscopy shows that the protein localizes intracellularly, and coarse-grained MD simulations indicate it causes bending of the surrounding lipid bilayer, corroborating a potential role for the E protein in viral budding. Although we did not find robust electrophysiological evidence of ion-channel activity, cells transfected with the E protein exhibited reduced intracellular Ca²⁺, which may further promote viral replication. However, our atomistic MD simulations revealed that previous NMR structures are relatively unstable, and result in models incapable of ion conduction. Our study highlights the importance of using high-resolution structural data obtained from a full-length protein to gain detailed molecular insights, and eventually permitting virtual drug screening.

Calcium Ions Signaling: Targets for Attack and Utilization by Viruses

Calcium, as a second intracellular messenger, participate in various physiological and biochemical processes, including cell growth and proliferation, energy metabolism, information transfer, cell death, and immune response. Ca2+ channels or pumps in plasma and organelle membranes and Ca2+-related proteins maintain Ca2+ homeostasis by regulating Ca2+ inflow, outflow and buffering to avoid any adverse effects caused by Ca2+ overload or depletion. Thus, Ca2+ signaling also provides a target for virus invasion, replication, proliferation and release. After hijacking the host cell, viruses exploit Ca2+ signaling to regulate apoptosis and resist host immunity to establish persistent infection. In this review, we discuss cellular Ca2+ signaling and channels, interaction of calcium-associated proteins with viruses, and host cell fate, as well as the role of Ca2+ in cell death and antiviral response during viral infection.

Activation of the Ca2+/NFAT Pathway by Assembly of Hepatitis C Virus Core Protein into Nucleocapsid-like Particles

Hepatitis C virus (HCV) is the primary pathogen responsible for liver cirrhosis and hepatocellular carcinoma. The main virion component, the core (C) protein, has been linked to several aspects of HCV pathology, including oncogenesis, immune evasion and stress responses. We and others have previously shown that C expression in various cell lines activates Ca²⁺ signaling and alters Ca²⁺ homeostasis. In this study, we identified two distinct C protein regions that are required for the activation of Ca²⁺/NFAT signaling. In the basic N-terminal domain, which has been implicated in self-association of C, amino acids 1–68 were critical for NFAT activation. Sedimentation analysis of four mutants in this domain revealed that association of the C protein into nucleocapsid-like particles correlated with NFAT-activated transcription. The internal, lipid droplet-targeting domain was not required for NFAT-activated transcription. Finally, the C-terminal ER-targeting domain was required in extenso for the C protein to function. Our results indicate that targeting of HCV C to the ER is necessary but not sufficient for inducing Ca²⁺/NFAT signaling. Taken together, our data are consistent with a model whereby proteolytic intermediates of C with an intact transmembrane ER-anchor assemble into pore-like structures in the ER membrane.

Hepatitis C Virus Core Protein Down-Regulates Expression of Src-Homology 2 Domain Containing Protein Tyrosine Phosphatase by Modulating Promoter DNA Methylation

Hepatitis C virus (HCV) is the major causative pathogen associated with liver cirrhosis and hepatocellular carcinoma. The main virion component, the core (C) protein, has been implicated in several aspects of HCV pathology including oncogenesis and immune subversion. Here we show that expression of the C protein induced specific tyrosine phosphorylation of the TCR-related signaling proteins ZAP-70, LAT and PLC-γ in the T cells. Stable expression of the C protein specifically reduced Src homology domain 2-containing protein tyrosine phosphatase 1 (SHP-1) mRNA and protein accumulation. Quantitative CpG methylation analysis revealed a distinct CpG methylation pattern at the SHP-1 gene promoter in the C protein expressing cells that included specific hypermethylation of the binding site for Sp1 transcription factor. Collectively, our results suggest that HCV may suppress immune responses and facilitate its own persistence by deregulating phosphotyrosine signaling via repressive epigenetic CpG modification at the SHP-1 promoter in the T cells.

HCV-coinfection is related to an increased HIV-1 reservoir size in cART-treated HIV patients: a cross-sectional study

In HIV-1/HCV-coinfected patients, chronic HCV infection leads to an increased T-lymphocyte immune activation compared to HIV-monoinfected patients, thereby likely contributing to increase HIV-1 reservoir that is the major barrier for its eradication. Our objective was to evaluate the influence of HCV coinfection in HIV-1 viral reservoir size in resting (r) CD4+ T-cells (CD25-CD69-HLADR-). Multicenter cross-sectional study of 97 cART-treated HIV-1 patients, including 36 patients with HIV and HCV-chronic co-infection without anti-HCV treatment, 32 HIV patients with HCV spontaneous clearance and 29 HIV-monoinfected patients. rCD4+ T-cells were isolated and total DNA was extracted. HIV viral reservoir was measured by Alu-LTR qPCR. Differences between groups were calculated with a generalized linear model. Overall, 63.9% were men, median age of 41 years and Caucasian. Median CD4+ and CD8+ T-lymphocytes were 725 and 858 cells/mm3, respectively. CD4+ T nadir cells was 305 cells/mm3. Proviral HIV-1 DNA size was significantly increased in chronic HIV/HCV-coinfected compared to HIV-monoinfected patients (206.21 ± 47.38 vs. 87.34 ± 22.46, respectively; P = 0.009), as well as in spontaneously clarified HCV co-infected patients when compared to HIV-monoinfected individuals (136.20 ± 33.20; P = 0.009). HIV-1/HCV co-infected patients showed a larger HIV-1 reservoir size in comparison to HIV-monoinfected individuals. This increase could lead to a greater complexity in the elimination of HIV-1 reservoir in HIV-1/HCV-coinfected individuals, which should be considered in the current strategies for the elimination of HIV-1 reservoir.

The Immunogenicity in Mice of HCV Core Delivered as DNA Is Modulated by Its Capacity to Induce Oxidative Stress and Oxidative Stress Response

HCV core is an attractive HCV vaccine target, however, clinical or preclinical trials of core-based vaccines showed little success. We aimed to delineate what restricts its immunogenicity and improve immunogenic performance in mice. We designed plasmids encoding full-length HCV 1b core and its variants truncated after amino acids (aa) 60, 98, 152, 173, or up to aa 36 using virus-derived or synthetic polynucleotides (core191/60/98/152/173/36_191v or core152s DNA, respectively). We assessed their level of expression, route of degradation, ability to trigger the production of reactive oxygen species/ROS, and to activate the components of the Nrf2/ARE antioxidant defense pathway heme oxygenase 1/HO-1 and NAD(P)H: quinone oxidoreductase/Nqo-1. All core variants with the intact N-terminus induced production of ROS, and up-regulated expression of HO-1 and Nqo-1. The capacity of core variants to induce ROS and up-regulate HO-1 and Nqo-1 expression predetermined their immunogenicity in DNA-immunized BALB/c and C57BL/6 mice. The most immunogenic was core 152s, expressed at a modest level and inducing moderate oxidative stress and oxidative stress response. Thus, immunogenicity of HCV core is shaped by its ability to induce ROS and oxidative stress response. These considerations are important in understanding the mechanisms of viral suppression of cellular immune response and in HCV vaccine design.

Ultrastructural Localization and Molecular Associations of HCV Capsid Protein in Jurkat T Cells

Hepatitis C virus core protein is a highly basic viral protein that multimerizes with itself to form the viral capsid. When expressed in CD4⁺ T lymphocytes, it can induce modifications in several essential cellular and biological networks. To shed light on the mechanisms underlying the alterations caused by the viral protein, we have analyzed HCV-core subcellular localization and its associations with host proteins in Jurkat T cells. In order to investigate the intracellular localization of Hepatitis C virus core protein, we have used a lentiviral system to transduce Jurkat T cells and subsequently localize the protein using immunoelectron microscopy techniques. We found that in Jurkat T cells, Hepatitis C virus core protein mostly localizes in the nucleus and specifically in the nucleolus. In addition, we performed pull-down assays combined with Mass Spectrometry Analysis, to identify proteins that associate with Hepatitis C virus core in Jurkat T cells. We found proteins such as NOLC1, PP1γ, ILF3, and C1QBP implicated in localization and/or traffic to the nucleolus. HCV-core associated proteins are implicated in RNA processing and RNA virus infection as well as in functions previously shown to be altered in Hepatitis C virus core expressing CD4⁺ T cells, such as cell cycle delay, decreased proliferation, and induction of a regulatory phenotype. Thus, in the current work, we show the ultrastructural localization of Hepatitis C virus core and the first profile of HCV core associated proteins in T cells, and we discuss the functions and interconnections of these proteins in molecular networks where relevant biological modifications have been described upon the expression of Hepatitis C virus core protein. Thereby, the current work constitutes a necessary step toward understanding the mechanisms underlying HCV core mediated alterations that had been described in relevant biological processes in CD4⁺ T cells.

Immune modulation by the hepatitis C virus core protein

Hepatitis C virus (HCV) infection is currently the most important cause of chronic viral hepatitis in the world and one of the most frequent indications for liver transplantation. HCV uses different strategies to evade the innate and adaptive immune response, and this evasion plays a key role in determining viral persistence. Several HCV viral proteins have been described as immune modulators. In this review, we will focus on the effect of HCV nucleocapsid core protein in the function of immune cells and its correlation with the findings observed in HCV chronically infected patients. Effects on immune cell function related to both extracellular and intracellular HCV core localization will be considered. This review provides an updated perspective on the mechanisms involved in HCV evasion related to one single HCV protein, which could become a key tool in the development of new antiviral strategies able to control and/or eradicate HCV infection.

Antiviral Activity of a Novel Compound CW-33 against Japanese Encephalitis Virus through Inhibiting Intracellular Calcium Overload

Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, has five genotypes (I, II, III, IV, and V). JEV genotype I circulates widely in some Asian countries. However, current JEV vaccines based on genotype III strains show low neutralizing capacities against genotype I variants. In addition, JE has no specific treatment, except a few supportive treatments. Compound CW-33, an intermediate synthesized derivative of furoquinolines, was investigated for its antiviral activities against JEV in this study. CW-33 exhibited the less cytotoxicity to Syrian baby hamster kidney (BHK-21) and human medulloblastoma (TE761) cells. CW-33 dose-dependently reduced the cytopathic effect and apoptosis of JEV-infected cells. Supernatant virus yield assay pinpointed CW-33 as having potential anti-JEV activity with IC₅₀ values ranging from 12.7 to 38.5 μM. Time-of-addition assay with CW-33 indicated that simultaneous and post-treatment had no plaque reduction activity, but continuous and simultaneous treatments proved to have highly effective antiviral activity, with IC₅₀ values of 32.7 and 48.5 μM, respectively. CW-33 significantly moderated JEV-triggered Ca²⁺ overload, which correlated with the recovery of mitochondria membrane potential as well as the activation of Akt/mTOR and Jak/STAT1 signals in treated infected cells. Phosphopeptide profiling by LC-MS/MS revealed that CW-33 upregulated proteins from the enzyme modulator category, such as protein phosphatase inhibitor 2 (I-2), Rho GTPase-activating protein 35, ARF GTPase-activating protein GIT2, and putative 3-phosphoinositide-dependent protein kinase 2. These enzyme modulators identified were associated with the activation of Akt/mTOR and Jak/STAT1 signals. Meanwhile, I-2 treatment substantially inhibited the apoptosis of JEV-infected cells. The results demonstrated that CW-33 exhibited a significant potential in the development of anti-JEV agents.

Hepatitis C virus suppresses Hepatocyte Nuclear Factor 4 alpha, a key regulator of hepatocellular carcinoma

Hepatitis C Virus (HCV) infection presents with a disturbed lipid profile and can evolve to hepatic steatosis and hepatocellular carcinoma (HCC). Hepatocyte Nuclear Factor 4 alpha (HNF4α) is the most abundant transcription factor in the liver, a key regulator of hepatic lipid metabolism and a critical determinant of Epithelial to Mesenchymal Transition and hepatic development. We have previously shown that transient inhibition of HNF4α initiates transformation of immortalized hepatocytes through a feedback loop consisting of miR-24, IL6 receptor (IL6R), STAT3, miR-124 and miR-629, suggesting a central role of HNF4α in HCC. However, the role of HNF4α in Hepatitis C Virus (HCV)-related hepatocarcinoma has not been evaluated and remains controversial. In this study, we provide strong evidence suggesting that HCV downregulates HNF4α expression at both transcriptional and translational levels. The observed decrease of HNF4α expression correlated with the downregulation of its downstream targets, HNF1α and MTP. Ectopic overexpression of HCV proteins also exhibited an inhibitory effect on HNF4α levels. The inhibition of HNF4α expression by HCV appeared to be mediated at transcriptional level as HCV proteins suppressed HNF4α gene promoter activity. HCV also up-regulated IL6R, activated STAT3 protein phosphorylation and altered the expression of acute phase genes. Furthermore, as HCV triggered the loss of HNF4α a consequent change of miR-24, miR-629 or miR-124 was observed. Our findings demonstrated that HCV-related HCC could be mediated through HNF4α-microRNA deregulation implying a possible role of HNF4α in HCV hepatocarcinogenesis. HCV inhibition of HNF4α could be sustained to promote HCC.

CD4+ primary T cells expressing HCV-core protein upregulate Foxp3 and IL-10, suppressing CD4 and CD8 T cells

Adaptive T cell responses are critical for controlling HCV infection. While there is clinical evidence of a relevant role for regulatory T cells in chronic HCV-infected patients, based on their increased number and function; mechanisms underlying such a phenomena are still poorly understood. Accumulating evidence suggests that proteins from Hepatitis C virus can suppress host immune responses. We and others have shown that HCV is present in CD4+ lymphocytes from chronically infected patients and that HCV-core protein induces a state of unresponsiveness in the CD4+ tumor cell line Jurkat. Here we show that CD4+ primary T cells lentivirally transduced with HCV-core, not only acquire an anergic phenotype but also inhibit IL-2 production and proliferation of bystander CD4+ or CD8+ T cells in response to anti-CD3 plus anti-CD28 stimulation. Core-transduced CD4+ T cells show a phenotype characterized by an increased basal secretion of the regulatory cytokine IL-10, a decreased IFN-γ production upon stimulation, as well as expression of regulatory T cell markers, CTLA-4, and Foxp3. A significant induction of CD4+CD25+CD127(low)PD-1(high)TIM-3(high) regulatory T cells with an exhausted phenotype was also observed. Moreover, CCR7 expression decreased in HCV-core expressing CD4+ T cells explaining their sequestration in inflamed tissues such as the infected liver. This work provides a new perspective on de novo generation of regulatory CD4+ T cells in the periphery, induced by the expression of a single viral protein.

Direct effects of hepatitis C virus on the lymphoid cells

It has been reported that the direct binding of hepatitis C virus (HCV) and/or the replication of HCV in the extrahepatic organs and, especially, lymphoid cells, might affect the pathogenesis of extrahepatic diseases with HCV infection. More than one decade ago, several reports described the existence of HCV-RNA in peripheral blood mononuclear cells. Moreover, many reports describing the existence of HCV in B lymphocytes and B cell lymphoma have been published. In addition to B lymphocytes, it was reported that HCV replication could be detected in T lymphocytes and T cell lines. Among the extrahepatic diseases with HCV infection, mixed cryoglobulinemia-related diseases and autoimmune-related diseases are important for understanding the immunopathogensis of HCV persistent infection. Moreover, HCV persistent infection can cause malignant lymphoma. The biological significance of lymphotropic HCV has not yet become clear. However, several candidates have been considered for a long time. One is that lymphotropic HCV is an HCV reservoir that might contribute to the recurrence of HCV infection and difficult-to-treat disease status. The other important issue is the carcinogenesis of the lymphoid cells and disturbances of the immune responses. Therefore, the extrahepatic diseases might be induced by direct interaction between HCV and lymphoid cells. In this article, we summarize various studies showing the direct effect of HCV on lymphoid cells and discuss the biological significance of lymphotropic HCV.

Phenotypic and functional alterations of primary human PBMCs induced by HCV non-enveloped capsid-like particles uptake

Hepatitis C virus non-enveloped particles circulate in the serum of HCV-infected patients and are believed to be involved in viral persistence. It was previously demonstrated that recombinant HCVne particles can efficiently enter T cells. In this study we investigated the effect of this entry on the phenotype and function of PBMCs, focused on the CD4+ and CD8+ T-cells. We have generated recombinant HCVne in the absence of other viral proteins. PBMCs from healthy donors were sampled after incubation either with HCVne or the control at different time points. Levels of expression of CD107a, CD25, CTLA-4, and T regulatory cells were estimated and cytokine expression and secretion were also monitored. Peripheral T cells expressed elevated CD127. The intracellular expression of the inhibitory marker CTLA-4 (CD152) increased significantly on peripheral T cells at late hours post-treatment, compared to the respective non-treated group. Despite the fact that there was an initial immune response due to HCVne uptake, T cells were driven to a partial exhausted phenotype. A significant induction of CD4+CD25+(hi)CD127-regulatory T cells at late hours was observed. Consistently, Foxp3+CD4+ T cells were also increased. In parallel, a significant transcriptional activation and increased secretion of IL-2, IL-10, and IFN-γ, was recorded. Moreover, mRNA transcription of TGF-β was considerably elevated. HCVne particles have the potential to shape the immune response by modifying specific phenotypic and functional markers mainly on CD4+ T cells and driving them to partial exhaustion as well as to Treg expansion.

African swine fever virus controls the host transcription and cellular machinery of protein synthesis

Throughout a viral infection, the infected cell reprograms the gene expression pattern in order to establish a satisfactory antiviral response. African swine fever virus (ASFV), like other complex DNA viruses, sets up a number of strategies to evade the host's defense systems, such as apoptosis, inflammation and immune responses. The capability of the virus to persist in its natural hosts and in domestic pigs, which recover from infection with less virulent isolates, suggests that the virus displays effective mechanisms to escape host defense systems. ASFV has been described to regulate the activation of several transcription factors, thus regulating the activation of specific target genes during ASFV infection. Whereas some reports have concerned about anti-apoptotic ASFV genes and the molecular mechanisms by which ASFV interferes with inducible gene transcription and immune evasion, less is yet known regarding how ASFV regulates the translational machinery in infected cells, although a recent report has shown a mechanism for favored expression of viral genes based on compartmentalization of viral mRNA and ribosomes with cellular translation factors within the virus factory. The viral mechanisms involved both in the regulation of host genes transcription and in the control of cellular protein synthesis are summarized in this review.

Biological significance of HCV in various kinds of lymphoid cells

It has been reported that HCV can infect not only hepatocytes but also various kinds of lymphoid cells. Although many reports have described the biological significance of lymphotropic HCV, the issue remains controversial since the target lymphoid cells might have various kinds of functions in the immune system. One of the important roles of lymphoid cells in HCV replication is being a reservoir of HCV. Several groups described the detection of HCV-RNA in lymphoid cells after HCV eradication in plasma. Another important role of lymphotropic HCV is that it acts as a carcinogenic agent and induces immune dysfunction. In this paper, we summarize the reports regarding the biological significance of lymphotropic HCV in representative lymphoid cells.

Evaluation of hepatitis B viral replication and proteomic analysis of HepG2.2.15 cell line after knockdown of HBx

BACKGROUND

Hepatitis B virus (HBV) is one of the major pathogens of human liver disease. Studies have shown that HBV X protein (HBx) plays an important role in promoting viral gene expression and replication. In this study we performed a global proteomic profiling to identify the downstream functional proteins of HBx, thereby detecting the mechanisms of action of HBx on virion replication.

METHODS

HBx in the HepG2.2.15 cell line was knocked down by the transfection of small interfering RNA (siRNA). The replication level of HBV was evaluated by microparticle enzyme immunoassay analysis of HBsAg and HBeAg in the culture supernatant, and real-time quantitative PCR analysis of HBV DNA. Two-dimensional electrophoresis combined with MALDI-TOF/TOF was performed to analyze the changes in protein expression profile after treatment with HBx siRNA.

RESULTS

Knockdown of HBx disturbed HBV replication in vitro. HBx target siRNA significantly inhibited the expression of HBsAg, HBeAg and the replication of HBV DNA. Twelve significantly changed proteins (7 upregulated and 5 downregulated) were successfully identified by MALDI-TOF/TOF using proteomics differential expression analysis after the knockdown of HBx. Among these identified proteins, HSP70 was validated by Western blotting.

CONCLUSION

The results of the study indicated the positive effect of HBx on HBV replication, and a group of downstream target proteins of HBx may be responsible for this effect.

Modulation of IL-2 expression after uptake of hepatitis C virus non-enveloped capsid-like particles: the role of p38 kinase

Hepatitis C virus (HCV) has been shown to actively replicate in cells of the immune system, altering both their function and cytokine expression. Naked nucleocapsids have been reported in the serum of infected patients. We investigated interference of recombinant non-enveloped capsid-like particles with signaling pathways in T cells. HCV non-enveloped particles (HCVne) internalization was verified in Jurkat and Hut 78 T cells, as well as primary human peripheral blood and intrahepatic mononuclear cells. HCVne uptake leads to activation of the MAPKs-p38 signaling pathway. Using specific phosphoantibodies, signaling pathways inhibitors, and chemical agents, it was demonstrated that p38 activation in T cells correlated with IL-2 transcriptional activation and was accompanied by a parallel increase of IL-2 cytokine secretion. c-fos and egr-1, two transcription factors, essential for IL-2 promoter activity, were also found to be elevated. We propose that HCVne uptake by T lymphocytes results in increased MAPKs-p38 activity and IL-2 expression, thus altering the host immune response.

Oncogenic potential of hepatitis C virus proteins

Chronic hepatitis C virus (HCV) infection is a major risk factor for liver disease progression, and may lead to cirrhosis and hepatocellular carcinoma (HCC). The HCV genome contains a single-stranded positive sense RNA with a cytoplasmic lifecycle. HCV proteins interact with many host-cell factors and are involved in a wide range of activities, including cell cycle regulation, transcriptional regulation, cell proliferation, apoptosis, lipid metabolism, and cell growth promotion. Increasing experimental evidences suggest that HCV contributes to HCC by modulating pathways that may promote malignant transformation of hepatocytes. At least four of the 10 HCV gene products, namely core, NS3, NS5A and NS5B play roles in several potentially oncogenic pathways. Induction of both endoplasmic reticulum (ER) stress and oxidative stress by HCV proteins may also contribute to hepatocyte growth promotion. The current review identifies important functions of the viral proteins connecting HCV infections and potential for development of HCC. However, most of the putative transforming potentials of the HCV proteins have been defined in artificial cellular systems, and need to be established relevant to infection and disease models. The new insight into the mechanisms for HCV mediated disease progression may offer novel therapeutic targets for one of the most devastating human malignancies in the world today.

Specific activation of 2'-5'oligoadenylate synthetase gene promoter by hepatitis C virus-core protein: A potential for developing hepatitis C virus targeting gene therapy

AIM: To examine whether 2'-5'oligoadenylate synthetase (OAS) gene promoter can be specifically activated by hepatitis C virus (HCV)-core protein.

METHODS: Human embryo hepatic cell line L02 was transfected with pcDNA3.1-core plasmid and selected by G418. Expression of HCV-core was detected by reverse transcription polymerase chain reaction and Western blotting. The OAS promoter sequence was amplified from the genomic DNA and inserted into pGL3-basic vector. The resultant pGL3-OAS-Luci plasmid was transiently transfected into L02/core cells and luciferase activity was assayed.

RESULTS: L02/core cell line stably expressing HCV-core protein was established. The pGL3-OAS-Luci construct exhibited significant transcriptional activity in the L02/core cells but not in the L02 cells.

CONCLUSION: HCV-core protein activates the OAS gene promoter specifically and effectively. Utilization of OAS gene promoter would be an ideal strategy for developing HCV-specific gene therapy.

Hepatitis C virus and disrupted interferon signaling promote lymphoproliferation via type II CD95 and interleukins

BACKGROUND & AIMS

The molecular mechanisms of lymphoproliferation associated with the disruption of interferon (IFN) signaling and chronic hepatitis C virus (HCV) infection are poorly understood. Lymphomas are extrahepatic manifestations of HCV infection; we sought to clarify the molecular mechanisms of these processes.

METHODS

We established interferon regulatory factor-1-null (irf-1(-/-)) mice with inducible and persistent expression of HCV structural proteins (irf-1/CN2 mice). All the mice (n = 900) were observed for at least 600 days after Cre/loxP switching. Histologic analyses, as well as analyses of lymphoproliferation, sensitivity to Fas-induced apoptosis, colony formation, and cytokine production, were performed. Proteins associated with these processes were also assessed.

RESULTS

Irf-1/CN2 mice had extremely high incidences of lymphomas and lymphoproliferative disorders and displayed increased mortality. Disruption of irf-1 reduced the sensitivity to Fas-induced apoptosis and decreased the levels of caspases-3/7 and caspase-9 messenger RNA species and enzymatic activities. Furthermore, the irf-1/CN2 mice showed decreased activation of caspases-3/7 and caspase-9 and increased levels of interleukin (IL)-2, IL-10, and Bcl-2, as well as increased Bcl-2 expression, which promoted oncogenic transformation of lymphocytes. IL-2 and IL-10 were induced by the HCV core protein in splenocytes.

CONCLUSIONS

Disruption of IFN signaling resulted in development of lymphoma, indicating that differential signaling occurs in lymphocytes compared with liver. This mouse model, in which HCV expression and disruption of IFN signaling synergize to promote lymphoproliferation, will be an important tool for the development of therapeutic agents that target the lymphoproliferative pathway.

Viral calciomics: interplays between Ca2+ and virus

Ca²⁺ is one of the most universal and versatile signaling molecules and is involved in almost every aspect of cellular processes. Viruses are adept at utilizing the universal Ca²⁺ signal to create a tailored cellular environment that meets their own demands. This review summarizes most of the known mechanisms by which viruses perturb Ca²⁺ homeostasis and utilize Ca²⁺ and cellular Ca²⁺-binding proteins to their benefit in their replication cycles. Ca²⁺ plays important roles in virion structure formation, virus entry, viral gene expression, posttranslational processing of viral proteins and virion maturation and release. As part of the review, we introduce an algorithm to identify linear “EF-hand” Ca²⁺-binding motifs which resulted in the prediction of a total of 93 previously unrecognized Ca²⁺-binding motifs in virus proteins. Many of these proteins are nonstructural proteins, a class of proteins among which Ca²⁺ interactions had not been formerly appreciated. The presence of linear Ca²⁺-binding motifs in viral proteins enlarges the spectrum of Ca²⁺–virus interplay and expands the total scenario of viral calciomics.

Th1 and Th2 cytokines are elevated in HCV-infected SVR(-) patients treated with interferon-alpha

Interferon-alpha-based treatment is a standard therapy to cure hepatitis C virus-infected patients. However, the reasons for the failure of interferon-alpha treatment in some patients have not been fully elucidated. We evaluated the differences in the expression levels of various cytokines among patients with and without sustained viral response (SVR). We found that the chemokines (MIG and IP-10) and inflammation-related cytokines (IL-6) were transiently elevated in patients with SVR(+) before interferon-alpha treatment and in the early phase of treatment (week 2), indicating that these cytokines may be related to viral clearance. Furthermore, higher serum levels of Th1 and Th2 cytokines (IL-2, IL-4, IL-5, IL-10, tumor necrosis factor, and IFN-gamma) were observed in SVR(-) than in SVR(+) patients, indicating that they may be associated with ineffective anti-HCV immune response. Our data revealed that the patterns of cytokines varied greatly between SVR(+) and SVR(-) patients before and after IFN-alpha treatment.

Hepatitis C virus core protein up-regulates anergy-related genes and a new set of genes, which affects T cell homeostasis

Hepatitis C virus (HCV) infection is the main cause for chronic hepatitis, leading to cirrhosis and hepatic carcinoma. Virally induced immune dysfunction has been called as the cause for viral persistence. Previous results demonstrate that CD4 Jurkat cells stably expressing the HCV core protein show an increased activation of NFAT transcription factor and an impaired IL-2 promoter activity, affecting intracellular signaling pathways in a manner that mimics clonal anergy. We had shown previously that NFAT activates a transcriptional program, ensuing in immunological tolerance. In the present work, we have engineered lentiviral vectors expressing the HCV core to analyze the events, which unfold in the initial phase of HCV core-induced anergy. We show that genes initially described to be up-regulated by ionomycin-induced anergy in mice are also up-regulated in humans, not only by ionomycin but also by HCV core expression. We also show that HCV core is sufficient to cause NFAT nuclear translocation and a slow-down in cell-cycle progression, and using whole genome microarrays, we identify novel genes up-regulated in Jurkat cells expressing HCV core. The relevance of our results is highlighted by the presence of HCV in CD4 T cells from HCV chronically infected patients.

Up-regulation of fatty acid synthase promoter by hepatitis C virus core protein: genotype-3a core has a stronger effect than genotype-1b core

BACKGROUND/AIMS

Hepatitis C virus genotype-3a (HCV-3a) is directly linked to steatosis development. We studied the effects of HCV-3a core protein on the promoter activity of fatty acid synthase (FAS), a major enzyme involved in de novo lipid synthesis.

METHODS AND RESULTS

HCV-3a and -1b core genes were cloned and expressed. Using a FAS promoter-luciferase reporter, we demonstrated that both HCV-3a and -1b core proteins up-regulated the FAS promoter. However, HCV-3a core protein expression induced significantly higher FAS promoter activity than HCV-1b core. We further showed that FAS up-regulation by HCV core was dependent on transcription factor sterol response element binding protein-1. Mutational analysis showed that processing of HCV core protein of different genotypes was differentially involved in FAS promoter up-regulation. Although lipid droplet localization of HCV core protein was not important for FAS up-regulation, a specific amino acid residue (Phe(164)) within the FATG lipid droplet localization sequence of HCV-3a core protein played a major role in the stronger FAS activation by HCV-3a core.

CONCLUSIONS

The stronger effect of HCV-3a core protein on FAS activation in comparison to HCV-1b core could contribute to the higher prevalence and severity of steatosis in HCV-3a infections.

Development and characterization of a recombinant cDNA-based hepatitis C virus system

Invention of subgenomic HCV replicon a few years ago and recent success of in vitro production of infectious HCV have improved our knowledge of the HCV life cycle, replication, pathogenesis, and screening of anti-HCV therapeutics. However, the highly genotype-dependent nature of the in vitro HCV production system has limited its potential for HCV research. In this study, we constructed a recombinant DNA-based HCV system that contained EF-1alpha promoter-driven HCV genotype 1b with HCV E1/E2 deleted and replaced by GFP. We co-transfected this recombinant cDNA with HCV E1/E2 or VSV-G expression plasmid into 293T cells, and we showed HCV protein expression and processing and demonstrated production of HCV-like particles in culture supernatant of co-transfected cells. These results support potential use of this system for studies on expression and processing of the HCV polyprotein and assembly and release of HCV-like particles.

Expression of the alternative reading frame protein of Hepatitis C virus induces cytokines involved in hepatic injuries

Hepatitis C virus (HCV) Core has been implicated in immune-mediated mechanisms associated with the development of chronic hepatic diseases. Discovery of different alternative reading frame proteins (ARFPs) expressed from the HCV Core coding sequence challenges properties assigned to Core. This study was designed to evaluate the immunomodulatory functions of Core and ARFPs in monocytes, dendritic cells (DCs), macrophages (Mphi) and hepatocytes, cells that are all capable of supporting HCV replication. THP-1 cells, monocyte-derived Mphi and DCs, and Huh7 cells were infected by using adenoviruses (Ad) encoding Core, CE1E2 and a Core sequence modified so that the Core protein is wild type, but no ARFPs are expressed (CDeltaARFP). THP-1 cells and DCs infected with Ad encoding Core or CE1E2 produced significant levels of interleukin-6 (IL-6), IL-8, MCP-1 and MIP-1beta, whereas production of these chemokines with AdCDeltaARFP was reduced or abolished. Similar effects on IL-8 production were observed in Huh7 cells and on IL-6 and MIP-1beta in Mphi. Wild-type Core sequence, but not CDeltaARFP, could trans-activate the IL-8 promoter and this activation was not associated with activation of p38/p42-44MAPK. This study illustrates, for the first time, the critical importance of ARFP expression in immunomodulatory functions attributed to Core expression and suggests a potential involvement of ARFP in mechanisms associated with HCV pathogenesis.

Alpha-defensin increase in peripheral blood mononuclear cells from patients with hepatitis C virus chronic infection

The alpha-defensin genes promoter regions contain a putative nuclear factors of activated T cells (NFAT)-binding site and it is known that hepatitis C virus (HCV) core protein activates the interleukin (IL)-2 gene transcription through the NFAT pathway. The aims of this study were to investigate if HCV affects the alpha-defensin expression in peripheral human mononuclear cells (PBMCs) and to evaluate the existence of a correlation between alpha-defensins and liver damage in patients with chronic hepatitis C. Ninety patients with chronic hepatitis C, 30 with chronic hepatitis B and 25 healthy controls were enrolled. Alpha-defensins were identified and quantified in PBMCs by mass spectrometry, enzyme-linked immunosorbent assay, antibacterial activity and mRNA levels. PBMCs from three patients and controls were stimulated with HCV core protein, hepatitis B virus core antigen and the alpha-defensin mRNAs level was quantified. We found that HCV core protein activates in vitro the alpha-defensin transcription. Alpha-defensin levels in patients with chronic hepatitis C (mean +/- SD = 1.103 +/- 0.765 ng/10(6) cells), chronic hepatitis B (0.53 +/- 0.15) and healthy controls (0.217 +/- 0.09) resulted significantly different (P < 0.001). In patients with chronic hepatitis C, the alpha-defensin levels and antibacterial activity correlate with the liver fibrosis. Our data suggest that HCV induces alpha-defensin expression. The high linear correlation of alpha-defensin levels with advancing fibrosis makes the measure of these peptides a reliable marker to evaluate fibrosis stage.

Cytobiological consequences of calcium-signaling alterations induced by human viral proteins

Since calcium-signaling regulates specific and fundamental cellular processes, it represents the ideal target of viral proteins, in order for the virus to control cellular functions and favour its persistence, multiplication and spread. A detailed analysis of reports focused on the impact of viral proteins on calcium-signaling has shown that virus-related elevations of cytosolic calcium levels allow increased viral protein expression (HIV-1, HSV-1/2), viral replication (HBx, enterovirus 2B, HTLV-1 p12(I), HHV-8, EBV), viral maturation (rotavirus), viral release (enterovirus 2B) and cell immortalization (EBV). Interestingly, virus-induced decreased cytosolic calcium levels have been found to be associated with inhibition of immune cells functions (HIV-1 Tat, HHV-8 K15, EBV LMP2A). Finally, several viral proteins are able to modulate intracellular calcium-signaling to control cell viability (HIV-1 Tat, HTLV-1 p13(II), HCV core, HBx, enterovirus 2B, HHV-8 K7). These data point out calcium-signaling as a key cellular target for viral infection and should stimulate further studies exploring new calcium-related therapeutic strategies.

Viral and host immune regulatory mechanisms in hepatitis C virus infection

Recent studies suggest that liver inflammation in chronic hepatitis C virus (HCV) infection is controlled by several mechanisms, including host regulatory immune responses and viral polypeptides interacting with cells involved in innate and adaptive immunity. This article provides an overview about current thinking on host-pathogen symbiotic relationship in HCV infection and its significance with respect to pathogenesis. Special emphasis is given to regulatory T-cell subsets which have recently received attention and which are thought to play a major role in persistent viral infections such as HCV.

Microarray analyses and molecular profiling of Stat3 signaling pathway induced by hepatitis C virus core protein in human hepatocytes

Hepatitis C virus (HCV) infection is a major contributor to the development of end-stage liver disease, including cirrhosis and hepatocellular carcinoma (HCC). We have previously shown that HCV core protein promotes immortalization of primary human hepatocytes. To identify molecular changes involved in core protein-mediated immortalization, we have investigated differential gene expression by microarray analyses in primary human hepatocytes and HCV core gene introduced hepatocytes after senescence (early passage), immortalization (middle passage), and anchor-independent growth (late passage). Out of 33,000 human genes screened, 1918 transcripts were differentially expressed (>2-fold) in immortalized human hepatocytes (IHH) as compared to negative controls. Our analyses provided a molecular portrait of changes in gene expression associated with three distinct stages of hepatocytes after introduction of HCV core gene. Many of the overall changes were involved with important cellular pathways, including cell growth regulation, immune regulation, oxidative stress, and apoptosis. We focused on the Stat3 signaling pathway by further verifying selected genes at the protein level relevant to hepatocyte growth regulation. Our data suggested that the introduction of HCV core protein results in an increase in expression of IL-6, gp130, leptin receptor, and Stat3. Upregulation of these genes in turn may regulate c-myc and cyclin D1, downstream of the Stat3 signaling pathway. Identification of these modulated genes with potential roles may help in the selection of targets for therapies against HCV-mediated liver disease progression.

Pilot study of interferon-alpha-ribavirin-interleukin-2 for treatment of nonresponder patients with severe liver disease infected by hepatitis C virus genotype 1

The aim of this randomized prospective study was to assess the efficacy and safety of a triple therapy with interferon-alpha (IFN-alpha)-ribavirin-interleukin-2 (IL-2) for the treatment of patients with genotype 1 infection and high viral load nonresponsive to primary IFN-ribavirin therapy. Twenty hepatitis C virus (HCV) genotype 1 patients with high viral load and Metavir fibrosis score >or=2 without HIV co-infection who were previously nonviral responders to standard treatment with IFN plus ribavirin were intensively re-treated with IFN-alpha2a (3 millions (M) IU every 2 days) combined with ribavirin (1000-1200 mg/day) for a 24-week period. Patients were randomized to receive four cycles of subcutaneous injection of IL-2 (3 MIU/day, 5 days a week every 3 weeks) during either the first 12 weeks (group 1, n = 10) or the last 12 weeks (group 2, n = 10) of combination therapy. At the end of triple therapy, six patients (30%) achieved a biochemical response and 4 (20%) a viral response followed by a relapse after triple therapy withdrawal. After 12 weeks of therapy, no difference in viral load was observed between the groups. The decrease in viral load in group 2 was not raised after the addition of IL-2 to IFN plus ribavirin combination therapy. No serious adverse effects were observed. In conclusion, in patients with poor predictive factors of response, the addition of IL-2 to IFN ribavirin combination therapy does not exert a favourable impact on HCV treatment.

Characterization of T-cell responses against immunodominant epitopes from hepatitis C virus E2 and NS4a proteins

Successful clearance of hepatitis C virus (HCV) infection has been associated with strong cellular immune responses against viral antigens. However, although the magnitude of these responses is clearly important for viral eradication, more studies are needed to unravel the fine specificity of the protective anti-HCV immunity in infected patients. This was the aim of the present study. Overlapping peptides spanning the sequence of HCV E2 and NS4a proteins were used to stimulate T cells from patients with chronic hepatitis C divided into three groups: naïve patients, patients who exhibited sustained response to interferon (IFN)-alpha therapy and patients who failed to respond to the treatment. Interleukin-2 production by stimulated cells was measured in each case. Patients with sustained response to therapy had stronger responses to E2 peptides than nonresponders, whereas naïve patients demonstrated intermediate reactivity. In the case of NS4a, responses against peptides where similar in all groups of patients. Analysis of the peptides recognized by T cells showed that responses were broad and heterogeneous, and some immunodominant epitopes, preferentially recognized by patients exhibiting sustained response to treatment, were found. These results confirm the role of cellular immune responses in viral clearance, and stress the importance of immunodominant regions within HCV antigens. These viral sequences may represent valuable immunogens for preparation of therapeutic or prophylactic vaccines.

Hepatitis C virus non-structural 5A protein can enhance full-length core protein-induced nuclear factor-kappaB activation

AIM

To study the effects of hepatitis C virus (HCV) core and non-structural 5A (NS5A) proteins on nuclear factor-kappaB (NF-kappaB) activity for understanding their biological function on chronic hepatitis caused by HCV infection.

METHODS

Luciferase assay was used to measure the activity of NF-kappaB in three different cell lines cotransfected with a series of deletion mutants of core protein alone or together with NS5A protein using pNF-kappaB-Luc as a reporter plasmid. Western blot and indirect immunofluorescence assays were used to confirm the expression of proteins and to detect their subcellular localization, respectively. Furthermore, Western blot was also used to detect the expression levels of NF-kappaB/p65, NF-kappaB/p50, and inhibitor kappaB-a (IkappaB-a).

RESULTS

The wild-type core protein (C191) and its mutant segments (C173 and C158) could activate NF-kappaB in Huh7 cells only and activation caused by (C191) could be enhanced by NS5A protein. Moreover, the full-length core protein and its different deletion mutants alone or together with NS5A protein did not enhance the expression level of NF-kappaB. The NF-kappaB activity was augmented due to the dissociation of NF-kappaB-IkappaB complex and the degradation of IkappaB-a.

CONCLUSION

NF-kappaB is the key transcription factor that can activate many genes that are involved in the cellular immune response and inflammation. Coexpression of the full-length core protein along with NS5A can enhance the NF-kappaB activation, and this activation may play a significant role in chronic liver diseases including hepatocellular carcinoma associated with HCV infection.

Hepatitis C virus core protein induces an anergic state characterized by decreased interleukin-2 production and perturbation of mitogen-activated protein kinase responses

Alterations of cytokine responses are thought to favor the establishment of persistent hepatitis C virus (HCV) infections, enhancing the risk of liver cirrhosis and hepatocellular carcinoma. Here we demonstrate that the expression of the HCV core (C) protein in stably transfected T cells correlates with a selective reduction of interleukin-2 (IL-2) promoter activity and IL-2 production in response to T-cell receptor triggering, whereas the activation of IL-4, IL-10, gamma interferon, and tumor necrosis factor alpha was moderately increased. This altered cytokine expression profile was associated with a perturbation of mitogen-activated protein (MAP) kinase responses. Extracellular regulated kinase and p38 were constitutively phosphorylated in C-expressing cells, while triggering of the costimulatory c-Jun N-terminal kinase (JNK) signaling cascade and activation of the CD28 response element within the IL-2 promoter appeared to be impaired. The perturbations of MAP kinase phosphorylation could be eliminated by cyclosporine A-mediated inhibition of nuclear factor of activated T cells, suggesting that the inactivation of JNK signaling and hyporesponsiveness to IL-2 induction were downstream consequences of C-induced Ca(2+) flux in a manner that mimics the induction of clonal anergy.

Increased Fas ligand expression of CD4+ T cells by HCV core induces T cell-dependent hepatic inflammation

Hepatitis C virus (HCV) infection is associated with a high rate of viral persistence and the development of chronic liver disease. The expression of HCV core protein in T cells has previously been reported to alter T cell activation and has been linked to the development of liver inflammation. However, the molecular and cellular basis for the role of HCV core-expressing T cells in liver inflammation is not understood. Here, using double-transgenic mice of CD2/HCV-core transgenic mice and ovalbumin (OVA)-specific T cell receptor transgenic mice, we demonstrated that in vivo antigenic stimulation (OVA peptide administration) triggers a marked influx of core-expressing, antigen-specific, transgenic CD4+ T cells into the liver of these mice. Phenotypic analysis of the liver-infiltrating T cells revealed high expression levels of CD44 and Fas ligand (FasL). Adoptive transfer of liver-infiltrating, core-expressing CD4+ T cells into severe combined immunodeficiency mice directly demonstrated the capacity of these activated T cells to induce liver inflammation. It is important that anti-FasL antibody treatment of the mice at the time of cell transfer abrogated the liver inflammation induced by core-expressing CD4+ T cells. These findings suggest that activated T lymphocytes expressing elevated levels of FasL may be involved in the bystander killing of hepatocyte, as well as the induction of chronic liver inflammation, by promoting recruitment of proinflammatory cells to the liver.

Hepatitis C virus core protein acts as a trans-modulating factor on internal translation initiation of the viral RNA

Translation initiation of hepatitis C virus (HCV) RNA occurs through an internal ribosome entry site (IRES) located at its 5' end. As a positive-stranded virus, HCV uses the genomic RNA template for translation and replication, but the transition between these two processes remains poorly understood. HCV core protein (HCV-C) has been proposed as a good candidate to modulate such a regulation. However, current data are still the subject of controversy in attributing any potential role in HCV translation to the HCV core protein. Here we demonstrate that HCV-C displays binding activities toward both HCV IRES and the 40 S ribosomal subunit by using centrifugation on sucrose gradients. To gain further insight into these interactions, we investigated the effect of exogenous addition of purified HCV-C on HCV IRES activity by using an in vitro reporter assay. We found that HCV IRES-mediated translation was specifically modulated by HCV-C provided in trans, in a dose-dependent manner, with up to a 5-fold stimulation of the IRES efficiency upon addition of low amounts of HCV-C, followed by a decrease at high doses. Interestingly, mutations within some domains of the IRES as well as the presence of an upstream reporter gene both lead to changes in the expected effects, consistent with the high dependence of HCV IRES function on its overall structure. Collectively, these results indicate that the HCV core protein is involved in a tight modulation of HCV translation initiation, depending on its concentration, and they suggest an important biological role of this protein in viral gene expression.

Hepatitis C virus core protein regulates p300/CBP co-activation function. Possible role in the regulation of NF-AT1 transcriptional activity

Hepatitis C virus (HCV) core is a viral structural protein; it also participates in some cellular processes, including transcriptional regulation. However, the mechanisms of core-mediated transcriptional regulation remain poorly understood. Oncogenic virus proteins often target p300/CBP, a known co-activator of a wide variety of transcription factors, to regulate the expression of cellular and viral genes. Here we demonstrate, for the first time, that HCV core protein interacts with p300/CBP and enhances both its acetyl-transferase and transcriptional activities. In addition, we demonstrate that nuclear core protein activates the NH2-terminal transcription activation domain (TAD) of NF-AT1 in a p300/CBP-dependent manner. We propose a model in which core protein regulates the co-activation function of p300/CBP and activates NF-AT1, and probably other p300/CBP-regulated transcription factors, by a novel mechanism involving the regulation of the acetylation state of histones and/or components of the transcriptional machinery.

The viral protein A238L inhibits cyclooxygenase-2 expression through a nuclear factor of activated T cell-dependent transactivation pathway

Cyclooxygenase-2 is transiently induced upon cell activation or viral infections, resulting in inflammation and modulation of the immune response. Here we report that A238L, an African swine fever virus protein, efficiently inhibits cyclooxygenase-2 gene expression in Jurkat T cells and in virus-infected Vero cells. Transfection of Jurkat cells stably expressing A238L with cyclooxygenase-2 promoter-luciferase constructs containing 5'-terminal deletions or mutations in distal or proximal nuclear factor of activated T cell (NFAT) response elements revealed that these sequences are involved in the inhibition induced by A238L. Overexpression of a constitutively active version of the calcium-dependent phosphatase calcineurin or NFAT reversed the inhibition mediated by A238L on cyclooxygenase-2 promoter activation, whereas overexpression of p65 NFkappaB had no effect. A238L does not modify the nuclear localization of NFAT after phorbol 12-myristate 13-acetate/calcium ionophore stimulation. Moreover, we show that the mechanism by which the viral protein down-regulates cyclooxygenase-2 activity does not involve inhibition of the binding between NFAT and its specific DNA sequences into the cyclooxygenase-2 promoter. Strikingly, A238L dramatically inhibited the transactivation mediated by a GAL4-NFAT fusion protein containing the N-terminal transactivation domain of NFAT1. Taken together, these data indicate that A238L down-regulates cyclooxygenase-2 transcription through the NFAT response elements, being NFAT-dependent transactivation implicated in this down-regulation.

Functional properties of a 16 kDa protein translated from an alternative open reading frame of the core-encoding genomic region of hepatitis C virus

Hepatitis C virus (HCV) often causes persistent infection in humans. This could be due in part to the effect of viral proteins on cellular gene expression. Earlier observations suggest that the HCV core protein expressed from genotype 1a modulates important cellular genes at the transcriptional level, affects programmed cell death (apoptosis) and promotes cell growth. Recently, different groups of investigators have reported the translation of an approximately 16 kDa protein (named F/ARFP/core+1 ORF) from an alternate open reading frame of the HCV core-encoding genomic region. The functional significance of this F protein is presently unknown. Thus, whether the F and core proteins have both shared and distinct functions was investigated here. The experimental observations suggested that the F protein does not significantly modulate c-myc, hTERT and p53 promoter activities, unlike the HCV core protein. Interestingly, the F protein repressed p21 expression. Further studies indicated that the F protein does not inhibit tumour necrosis factor alpha-mediated apoptosis of HepG2 cells or promote rat embryo fibroblast growth. Taken together, these results suggest that the F protein does not share major properties identified previously for the HCV core protein, other than regulating p21 expression.

Immunization with hepatitis C virus core gene triggers potent T-cell response, but affects CD4+ T-cells

Numerous attempts to induce immunity against HCV core (HCV-C) by DNA immunization met serious difficulties in optimizing T-helper cell and antibody responses. Immunomodulatory properties of HCV-C could be blamed that seem to be dependent on the genotype of HCV source. Here, we characterized HCV-C gene from HCV 1b isolate 274933RU. Eukaryotic expression of HCV-C was effectively driven by CMVIE, while human elongation factor 1 alpha promoter directed low levels of HCV-C expression. C57BL/6 mice were immunized with CMVIE-driven HCV-C gene, and assessed for specific antibody production, T-cell proliferation and cytokine secretion. The number and proportion of CD19+, CD3+, CD3+/CD4+, and CD3+/CD8+ splenocytes in HCV-C gene recipients was evaluated by flow cytometry. A significant mounting drop in CD3+/CD4+ T-cell counts occurred in HCV-C gene-recipients as compared to the controls. Despite that, 75% of mice exhibited core-specific cellular reactivity revealed as high proliferative responses to HCV-C and HCV-C peptides. Stimulated T-cells secreted predominantly IFN-gamma and IL-2. A shift of epitope specificity was observed with the early response being broad, and the late limited to the HCV-C C-terminus. Thus, we demonstrate both T-cell immunogenicity and T-cell modulation by core of HCV 1b. Immune modulation by HCV core may affect host ability to mount long-lasting cellular and antibody response and should be dealt with in designing core-based HCV vaccines.

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Screening of HCTP4 interacting proteins in leukocytes by yeast-two hybrid technique

AIM: To investigate the biological function of HCTP4, yeast-two hybrid was performed to screen proteins interacting with HCTP4 in leukocytes.

METHODS: The HCTP4 gene was amplified by polymerase chain reaction (PCR) and HCTP4 bait plasmid was constructed by using yeast-two hybrid system 3, then the constructed vector was transformed into yeast AH109. The transformed yeast mated with yeast Y187 containing leukocytes cDNA library plasmid in 2×YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x--gal for selecting two times and screening. After extracting and sequencing of plasmid from blue colonies, we underwent analysis by bioinformatics.

RESULTS: Forty-four colonies were sequenced, among which twenty-five colonies were immunoglobulin lambda light chain, six human DNA sequences from clone RP11-189K21, four human DNA sequences from clone RP11-507C10, two homo sapiens 12p BAC RPCI11-75L1, one homo sapiens BAC clone RP11-21M10, one homo sapiens ubiquitin ligase mind bomb (MIB), one homo sapiens genomic DNA, chromosome 11 clone: RP11-867O8, one human DNA sequence from clone RP3-509I19, one homo sapiens small nuclear ribonucleoprotein polypeptide G, one homo sapiens UMP-CMP kinase (UMP-CMPK), and a new gene.

CONCLUSION: Genes of HCTP4 interacting proteins in leukocytes are successfully cloned and the results bring some new clues for studying the biological functions of HCTP4 and associated proteins.

[Active arthritis due to cryoglobulinemia based on HCV infection in a patient with RA improvement of arthritis with IFN-alpha]

A 49-year-old Japanese woman was diagnosed with rheumatoid arthritis (RA) based on ACR criteria in May 1999. She developed liver injury after initiation of disease-modifying antirheumatic drugs (DMARDs) and was found to have contracted HCV infection. RA disease activity worsened following restriction of medication due to liver dysfunction. However, 3 mg/day of prednisolone (PSL) resulted in a temporary but marked improvement of RA in December 2001; but arthritis recurred along with Raynaud's phenomenon and palpable purpura. Differential diagnosis between arthritis caused by cryoglobulinemia and exacerbation of RA was important for the selection of appropriate treatment. She manifested non-erosive arthritis on medium and large joints with proteinuria, hematuria and hypocomplementemia. In addition, type III cryoglobulin was detected and chronic active hepatitis was observed on liver biopsy in March 2002. We considered that the main cause for the arthritis was HCV-related mixed cryoglobulinemia. Administration of IFN-alpha resulted in the disappearance of HCV-RNA and cryoglobulin followed by amelioration of arthritis without exacerbation of RA.

Induction of FAS ligand expression in a human hepatoblastoma cell line by HCV core protein

Tumour cells and virus infected cells expressing Fas ligand (FasL) can evade immune surveillance by inducing apoptosis in T cells expressing Fas. In order to characterise a possible role of hepatitis C virus (HCV) core protein in similar mechanisms during HCV infection, we investigated Fas ligand expression and activity in a human hepatoblastoma cell line (HepG2) constitutively expressing this protein. Strong FasL induction was detected by immunoblotting and flow cytometry analysis in the core expressing cell lines Hep39. In contrast, vector transfected cells or cell lines expressing HCV E1-E2 proteins did not show FasL expression. Co-cultivation experiments of Hep39 cells with a Fas-sensitive T cell line indicated that FasL induced by the core protein had apoptotic activity toward target cells. Effect of the core protein on induction of FasL promoter was further examined by co-transfection of HepG2 cells with core-bearing plasmid and a vector in which luciferase gene expression is driven by human FasL promoter. Results of the luciferase assay indicated a positive regulation of FasL promoter by the core protein. In conclusion, HCV core protein plays a role in the induction of functional FasL in hepatoblastoma cell line and apoptosis in a target T cell line expressing Fas. Similar mechanisms may contribute, in vivo, to establishment of chronic infection and development of hepatocellular carcinoma (HCC).

Modulation of retinoid signaling by a cytoplasmic viral protein via sequestration of Sp110b, a potent transcriptional corepressor of retinoic acid receptor, from the nucleus

Hepatitis C virus (HCV) core protein (core) plays a significant role in the development of chronic liver diseases caused by HCV infection. We have discovered that the core sensitized all-trans-retinoic acid (ATRA)-induced cell death in MCF-7 cells. Activation of retinoic acid receptor alpha (RARalpha)-mediated transcription by the core was also seen in all the cell lines tested. By use of a yeast two-hybrid system, we identified Sp110b as a candidate for a core-interacting cellular factor. Although the function of Sp110b has remained unknown, we observed that Sp110b interacts with RARalpha and suppresses RARalpha-mediated transcription. These data suggest that Sp110b is a transcriptional cofactor negatively regulating RARalpha-mediated transcription. RNA interference-mediated reduction of endogenous Sp110b levels depressed the ability of the core to activate RARalpha-mediated transcription, suggesting an essential role for Sp110b in this pathway. The normal nuclear subcellular localization of Sp110b was altered by molecular interaction with the core to the cytoplasmic surface of the endoplasmic reticulum. This evidence suggests a model in which the core sequesters Sp110b from the nucleus and inactivates its corepressor function to activate RARalpha-mediated transcription. These findings likely describe a novel system in which a cytoplasmic viral protein regulates host cell transcription.

Suppression of HCV-specific T cells without differential hierarchy demonstrated ex vivo in persistent HCV infection

Hepatitis C virus (HCV) has a high propensity for persistence. To better define the immunologic determinants of HCV clearance and persistence, we examined the circulating HCV-specific T-cell frequency, repertoire, and cytokine phenotype ex vivo in 24 HCV seropositive subjects (12 chronic, 12 recovered), using 361 overlapping peptides in 36 antigenic pools that span the entire HCV core, NS3-NS5. Consistent with T-cell-mediated control of HCV, the overall HCV-specific type-1 T-cell response was significantly greater in average frequency (0.24% vs. 0.04% circulating lymphocytes, P =.001) and scope (14/36 vs. 4/36 pools, P =.002) among the recovered than the chronic subjects, and the T-cell response correlated inversely with HCV titer among the chronic subjects (R = -0.51, P =.049). Although highly antigenic regions were identified throughout the HCV genome, there was no apparent difference in the overall HCV-specific T-cell repertoire or type-1/type-2 cytokine profile relative to outcome. Notably, HCV persistence was associated with a reversible CD4-mediated suppression of HCV-specific CD8 T cells and with higher frequency of CD4(+)CD25(+) regulatory T cells (7.3% chronic vs. 2.5% recovered, P =.002) that could directly suppress HCV-specific type-1 CD8 T cells ex vivo. In conclusion, we found that HCV persistence is associated with a global quantitative and functional suppression of HCV-specific T cells but not differential antigenic hierarchy or cytokine phenotype relative to HCV clearance. The high frequency of CD4(+)CD25(+) regulatory T cells and their suppression of HCV-specific CD8 T cells ex vivo suggests a novel role for regulatory T cells in HCV persistence.