Inhibition of intrahepatic gamma interferon production by hepatitis C virus nonstructural protein 5A in transgenic mice. J Virol. 2009;83:8463-8469. [PMID: 19553305 DOI: 10.1128/jvi.00751-09]

Identification of two novel T cell epitopes on the E2 protein of classical swine fever virus C-strain

C-strain, also known as the HCLV strain, is a well-known live attenuated vaccine against classical swine fever (CSF), a devastating disease caused by classical swine fever virus (CSFV). Vaccination with C-strain induces a rapid onset of protection, which is associated with virus-specific gamma interferon (IFN-γ)-secreting CD8+ T cell responses. The E2 protein of CSFV is a major protective antigen. However, the T cell epitopes on the E2 protein remain largely unknown. In this study, eight overlapping nonapeptides of the E2 protein were predicted and synthesized to screen for potential T cell epitopes on the CSFV C-strain E2 protein. Molecular docking was performed on the candidate epitopes with the swine leukocyte antigen-1*0401. The analysis obtained two highly conserved T cell epitopes, 90STEEMGDDF98 and 331ATDRHSDYF339, which were further identified by enzyme-linked immunospot assay. Interestingly, the mutants deleting or substituting the epitopes are nonviable. Further analysis demonstrated that 90STEEMGDDF98 is crucial for the E2 homodimerization, while CSFV infection is significantly inhibited by the 331ATDRHSDYF339 peptide treatment. The two novel T cell epitopes can be used to design new vaccines that are able to provide rapid-onset protection.

Chronic Hepatitis C: Acute Exacerbation and Alanine Aminotransferase Flare

The hepatitis C virus (HCV) causes acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma, as well as extrahepatic manifestations such as malignant lymphoma. Currently, direct-acting antiviral agents (DAAs) against HCV infection can lead to a sustained virological response (SVR) in almost all HCV-infected patients. In this review article, we discuss acute exacerbation and alanine aminotransferase (ALT) flare in patients with chronic HCV infection. Although acute liver failure caused by HCV infection is rare, careful attention should be paid to the cases with ALT elevation during the natural course of chronic HCV infection. HCV genotype 2 infection, the use of rituximab, and a higher dose of corticosteroid are factors associated with HCV acute exacerbation and ALT flare. Treatment regimens for cancer have been interrupted or changed due to ALT flare due to HCV infection in some patients undergoing chemotherapy for cancer. The pathogenesis of HCV acute exacerbation and ALT flare could involve cellular as well as humoral immune responses. In the DAA era, the earlier introduction of DAAs may prevent chronic HCV-infected patients with acute exacerbation and ALT flare from developing into a more severe form, although DAAs may not be effective for all of them.

Porvac® Subunit Vaccine E2-CD154 Induces Remarkable Rapid Protection against Classical Swine Fever Virus

Live attenuated C-strain classical swine fever vaccines provide early onset protection. These vaccines confer effective protection against the disease at 5–7 days post-vaccination. It was previously reported that intramuscular administration of the Porvac^® vaccine protects against highly virulent classical swine fever virus (CSFV) “Margarita” strain as early as seven days post-vaccination. In order to identify how rapidly protection against CSFV is conferred after a single dose of the Porvac^® subunit vaccine E2-CD154, 15 swine, vaccinated with a single dose of Porvac^®, were challenged intranasally at five, three, and one day post-vaccination with 2 × 10³ LD₅₀ of the highly pathogenic Cuban “Margarita” strain of the classical swine fever virus. Another five animals were the negative control of the experiment. The results provided clinical and virological data confirming protection at five days post-vaccination. Classical swine fever (CSF)-specific IFNγ T cell responses were detected in vaccinated animals but not detected in unvaccinated control animals. These results provided the first data that a subunit protein vaccine demonstrates clinical and viral protection at five days post-vaccination, as modified live vaccines.

A multiepitope peptide vaccine against HCV stimulates neutralizing humoral and persistent cellular responses in mice

BACKGROUND

Although DAAs hold promise to significantly reduce rates of chronic HCV infections, its eradication still requires development of an effective vaccine. Prolonged T cell responses and cross neutralizing antibodies are ideal for vaccination against the infection. We aimed to design and synthesize a 6 multi epitope peptide vaccine candidate and provide evidence for production of extended cellular and neutralizing Abs in mice.

METHODS

Six peptides derived from conserved epitopes in E1, E2 (n = 2),NS4B, NS5A and NS5B were designed, synthesized in a multiple antigenic peptide (MAP) form and administered w/o adjuvant to BALB/c mice as HCVp6-MAP at doses ranging from 800 ng to 16 μg. Humoral responses to structural epitopes were assayed by ELISA at different times after injection. ELISpot assay was used to evaluate IFN ɣ producing CD4+/ CD8+ T- lymphocytes at extended durations i.e. > 20 weeks. Viral neutralization by mice sera was tested for genotypes 2a (JFH1) and a chimeric 2a/4a virus (ED43/JFH1) in HCVcc culture.

RESULTS

HCVp6-MAP confers potent viral neutralization and specific cellular responses at > 1600 ng/ animal for at least 20 weeks.

CONCLUSION

We report on a promising anti HCV vaccine for future studies on permissive hosts and in clinical trials.

Hepatitis C virus-associated hepatocellular carcinoma after sustained virologic response

The introduction of a direct-acting antiviral (DAA) for patients with hepatitis C virus (HCV) infection, could lead to higher sustained virologic response (SVR) rates with fewer adverse events, and it could shorten the treatment duration relative to the interferon era. Although most recent clinical studies have demonstrated that the occurrence rates of hepatocellular carcinoma (HCC) are decreased by SVR with both interferon-based and interferon-free-regimens, there are several reports about the unexpected observation of high rates of early tumor occurrence and recurrence in patients with HCV-related HCC undergoing interferon-free therapy despite SVR. Several mechanisms of HCC occurrence and rapid immunological changes, including cytokines and chemokines during and after DAA treatment, have also been reported. We focused on the possibilities that HCC occurs or recurs during and after DAA treatment, based on the reported clinical and basic studies. Further studies and observations will be needed to determine the short-term and long-term effects on hepatocarcinogenesis caused by the eradication of HCV with DAAs. New serum biomarkers and a follow-up system for HCV-patients with SVR should be established.

Identification of potential anti-hepatitis C virus agents targeting non structural protein 5B using computational techniques

Hepatitis C virus (HCV) nonstructural protein 5B (NS5B) is an RNA-dependent RNA polymerase that plays a key role in HCV replication, and, hence, NS5B is an attractive target for hepatitis C drug discovery. Hepatitis C is a chronic liver disease affecting the global population significantly. Many NS5B inhibitors targeting active site were launched in recent years, however, still there exists a pressing need for cost-effective therapies with pan genotypic activity and therapies targeting niche HCV population with comorbities and resistant to earlier therapies. The objective of the current study is to identify potential anti-HCV agents from FDA approved drugs that are already in the market for a different disease-Drug repurposing approach. A combination of computational chemistry and computational biology techniques was used to discover potential therapies for hepatitis C targeting the NS5B Thumb I allosteric site. Computational chemistry analysis emphasized the fact that fluvastatin, a lipid lowering agent, and olopatadine, an antihistamine, exhibited good binding affinity to NS5B. In addition, gene set enrichment analysis brought to light the significant overlap between disease characteristic features and the mechanism of action of fluvastatin and olopatadine. The current study concludes the potentially beneficial use of fluvastatin in niche hepatitis C patient population suffering from nonalcoholic fatty liver diseases.

Zika virus infection dysregulates human neural stem cell growth and inhibits differentiation into neuroprogenitor cells

The current outbreak of Zika virus-associated diseases in South America and its threat to spread to other parts of the world has emerged as a global health emergency. A strong link between Zika virus and microcephaly exists, and the potential mechanisms associated with microcephaly are under intense investigation. In this study, we evaluated the effect of Zika virus infection of Asian and African lineages (PRVABC59 and MR766) in human neural stem cells (hNSCs). These two Zika virus strains displayed distinct infection pattern and growth rates in hNSCs. Zika virus MR766 strain increased serine 139 phosphorylation of histone H2AX (γH2AX), a known early cellular response proteins to DNA damage. On the other hand, PRVABC59 strain upregulated serine 15 phosphorylation of p53, p21 and PUMA expression. MR766-infected cells displayed poly (ADP-ribose) polymerase (PARP) and caspase-3 cleavage. Interestingly, infection of hNSCs by both strains of Zika virus for 24 h, followed by incubation in astrocyte differentiation medium, induced rounding and cell death. However, astrocytes generated from hNSCs by incubation in differentiation medium when infected with Zika virus displayed minimal cytopathic effect at an early time point. Infected hNSCs incubated in astrocyte differentiating medium displayed PARP cleavage within 24–36 h. Together, these results showed that two distinct strains of Zika virus potentiate hNSC growth inhibition by different mechanisms, but both viruses strongly induce death in early differentiating neuroprogenitor cells even at a very low multiplicity of infection. Our observations demonstrate further mechanistic insights for impaired neuronal homeostasis during active Zika virus infection.

Nonstructural 5A Protein of Hepatitis C Virus Interferes with Toll-Like Receptor Signaling and Suppresses the Interferon Response in Mouse Liver

The hepatitis C virus nonstructural protein NS5A is involved in resistance to the host immune response, as well as the viral lifecycle such as replication and maturation. Here, we established transgenic mice expressing NS5A protein in the liver and examined innate immune responses against lipopolysaccharide (LPS) in vivo. Intrahepatic gene expression levels of cytokines such as interleukin-6, tumor necrosis factor-α, and interferon-γ were significantly suppressed after LPS injection in the transgenic mouse liver. Induction of the C-C motif chemokine ligand 2, 4, and 5 was also suppressed. Phosphorylation of the signal transducer and activator of transcription 3, which is activated by cytokines, was also reduced, and expression levels of interferon-stimulated genes, 2’-5’ oligoadenylate synthase, interferon-inducible double-stranded RNA-activated protein kinase, and myxovirus resistance 1 were similarly suppressed. Since LPS binds to toll-like receptor 4 and stimulates the downstream pathway leading to induction of these genes, we examined the extracellular signal-regulated kinase and IκB-α. The phosphorylation levels of these molecules were reduced in transgenic mouse liver, indicating that the pathway upstream of the molecules was disrupted by NS5A. Further analyses revealed that the interaction between interleukin-1 receptor-associated kinase-1 and tumor necrosis factor receptor associated factor-6 was dispersed in transgenic mice, suggesting that NS5A may interfere with this interaction via myeloid differentiation primary response gene 88, which was shown to interact with NS5A. Since the gut microbiota, a source of LPS, is known to be associated with pathological conditions in liver diseases, our results suggest the involvement of NS5A in the pathogenesis of HCV infected-liver via the suppression of innate immunity.

Interferon Response in Hepatitis C Virus (HCV) Infection: Lessons from Cell Culture Systems of HCV Infection

Hepatitis C virus (HCV) is a positive-stranded RNA virus that infects approximately 130–170 million people worldwide. In 2005, the first HCV infection system in cell culture was established using clone JFH-1, which was isolated from a Japanese patient with fulminant HCV infection. JFH-1 replicates efficiently in hepatoma cells and infectious virion particles are released into the culture supernatant. The development of cell culture-derived HCV (HCVcc) systems has allowed us to understand how hosts respond to HCV infection and how HCV evades host responses. Although the mechanisms underlying the different outcomes of HCV infection are not fully understood, innate immune responses seem to have a critical impact on the outcome of HCV infection, as demonstrated by the prognostic value of IFN-λ gene polymorphisms among patients with chronic HCV infection. Herein, we review recent research on interferon response in HCV infection, particularly studies using HCVcc infection systems.

Hepatitis C Virus Nonstructural Protein 5A Inhibits MG132-Induced Apoptosis of Hepatocytes in Line with NF-κB-Nuclear Translocation

Background

Hepatitis C virus (HCV) infection is one of the major causes of cirrhosis and hepatocellular carcinoma. HCV nonstructural protein 5A (NS5A) is an attractive antiviral target and plays an important role in HCV replication as well as hepatocarcinogenesis. The aim of this study was to assess the effect of HCV NS5A protein in the abrogation of apoptotic cell death induced by the proteasome inhibitor MG132.

Methods

Apoptotic responses to MG132 and the expression of molecules involved in NF-κB signaling pathways in human hepatocytes were investigated with or without the expression of HCV NS5A.

Results

HCV NS5A protected HepG2 cells against MG132-induced apoptosis, in line with NF-κB-nuclear translocation. A similar NF-κB-nuclear translocation was observed in Huh7 cells infected with HCV JFH1. In agreement with this, after treatment with MG132, HCV NS5A could elevate the transcription of several NF-κB target genes such as BCL2 and BCLXL to inhibit MG132-induced apoptosis in hepatocytes. HCV HCV NS5A also enhanced phosphorylation of IκBα. Consistent with a conferred prosurvival advantage, HCV NS5A reduced MG132-induced poly(adenosine diphosphate-ribose) polymerase cleavage.

Conclusions

HCV NS5A expression enhances phosphorylation of IκBα, liberates NF-κB for nuclear translocation and downregulates MG132-induced apoptotic pathways in human hepatocytes. It is possible that the disruption of proteasome-associated apoptosis plays a role in the pathogenesis of HCV infection.

TLR4-dependent tumor-initiating stem cell-like cells (TICs) in alcohol-associated hepatocellular carcinogenesis

Alcohol abuse predisposes individuals to the development of hepatocellular carcinoma (HCC) and synergistically heightens the HCC risk in patients infected with hepatitis C virus (HCV). The mechanisms of this synergism have been elusive until our recent demonstration of the obligatory role of ectopically expressed TLR4 in liver tumorigenesis in alcohol-fed HCV Ns5a or Core transgenic mice. CD133+/CD49f+ tumor-initiating stem cell-like cells (TICs) isolated from these models are tumorigenic in a manner dependent on TLR4 and NANOG. TICs' tumor-initiating activity and chemoresistance are causally associated with inhibition of TGF-β tumor suppressor pathway due to NANOG-mediated expression of IGF2BP3 and YAP1. TLR4/NANOG activation causes p53 degradation via phosphorylation of the protective protein NUMB and its dissociation from p53 by the oncoprotein TBC1D15. Nutrient deprivation reduces overexpressed TBC1D15 in TICs via autophagy-mediated degradation, suggesting a possible role of this oncoprotein in linking metabolic reprogramming and self-renewal.

Emerging roles of interferon-stimulated genes in the innate immune response to hepatitis C virus infection

Infection with hepatitis C virus (HCV), a major viral cause of chronic liver disease, frequently progresses to steatosis and cirrhosis, which can lead to hepatocellular carcinoma. HCV infection strongly induces host responses, such as the activation of the unfolded protein response, autophagy and the innate immune response. Upon HCV infection, the host induces the interferon (IFN)-mediated frontline defense to limit virus replication. Conversely, HCV employs diverse strategies to escape host innate immune surveillance. Type I IFN elicits its antiviral actions by inducing a wide array of IFN-stimulated genes (ISGs). Nevertheless, the mechanisms by which these ISGs participate in IFN-mediated anti-HCV actions remain largely unknown. In this review, we first outline the signaling pathways known to be involved in the production of type I IFN and ISGs and the tactics that HCV uses to subvert innate immunity. Then, we summarize the effector mechanisms of scaffold ISGs known to modulate IFN function in HCV replication. We also highlight the potential functions of emerging ISGs, which were identified from genome-wide siRNA screens, in HCV replication. Finally, we discuss the functions of several cellular determinants critical for regulating host immunity in HCV replication. This review will provide a basis for understanding the complexity and functionality of the pleiotropic IFN system in HCV infection. Elucidation of the specificity and the mode of action of these emerging ISGs will also help to identify novel cellular targets against which effective HCV therapeutics can be developed.

Emerging roles of interferon-stimulated genes in the innate immune response to hepatitis C virus infection

Infection with hepatitis C virus (HCV), a major viral cause of chronic liver disease, frequently progresses to steatosis and cirrhosis, which can lead to hepatocellular carcinoma. HCV infection strongly induces host responses, such as the activation of the unfolded protein response, autophagy and the innate immune response. Upon HCV infection, the host induces the interferon (IFN)-mediated frontline defense to limit virus replication. Conversely, HCV employs diverse strategies to escape host innate immune surveillance. Type I IFN elicits its antiviral actions by inducing a wide array of IFN-stimulated genes (ISGs). Nevertheless, the mechanisms by which these ISGs participate in IFN-mediated anti-HCV actions remain largely unknown. In this review, we first outline the signaling pathways known to be involved in the production of type I IFN and ISGs and the tactics that HCV uses to subvert innate immunity. Then, we summarize the effector mechanisms of scaffold ISGs known to modulate IFN function in HCV replication. We also highlight the potential functions of emerging ISGs, which were identified from genome-wide siRNA screens, in HCV replication. Finally, we discuss the functions of several cellular determinants critical for regulating host immunity in HCV replication. This review will provide a basis for understanding the complexity and functionality of the pleiotropic IFN system in HCV infection. Elucidation of the specificity and the mode of action of these emerging ISGs will also help to identify novel cellular targets against which effective HCV therapeutics can be developed.

Regulation of microRNA by hepatitis B virus infection and their possible association with control of innate immunity

Hepatitis B virus (HBV) chronically infects more than 350 million people worldwide. HBV causes acute and chronic hepatitis, and is one of the major causes of cirrhosis and hepatocellular carcinoma. There exist complex interactions between HBV and the immune system including adaptive and innate immunity. Toll-like receptors (TLRs) and TLR-signaling pathways are important parts of the innate immune response in HBV infections. It is well known that TLR-ligands could suppress HBV replication and that TLRs play important roles in anti-viral defense. Previous immunological studies demonstrated that HBV e antigen (HBeAg) is more efficient at eliciting T-cell tolerance, including production of specific cytokines IL-2 and interferon gamma, than HBV core antigen. HBeAg downregulates cytokine production in hepatocytes by the inhibition of MAPK or NF-κB activation through the interaction with receptor-interacting serine/threonine protein kinase. MicroRNAs (miRNAs) are also able to regulate various biological processes such as the innate immune response. When the expressions of approximately 1000 miRNAs were compared between human hepatoma cells HepG2 and HepG2.2.15, which could produce HBV virion that infects chimpanzees, using real-time RT-PCR, we observed several different expression levels in miRNAs related to TLRs. Although we and others have shown that HBV modulates the host immune response, several of the miRNAs seem to be involved in the TLR signaling pathways. The possibility that alteration of these miRNAs during HBV infection might play a critical role in innate immunity against HBV infection should be considered. This article is intended to comprehensively review the association between HBV and innate immunity, and to discuss the role of miRNAs in the innate immune response to HBV infection.

Hepatitis C virus NS5A inhibitors and drug resistance mutations

Some direct-acting antiviral agents for hepatitis C virus (HCV), such as telaprevir and boceprevir have been available since 2011. It was reported that HCV NS5A is associated with interferon signaling related to HCV replication and hepatocarcinogenesis. HCV NS5A inhibitors efficiently inhibited HCV replication in vitro. Human studies showed that dual, triple and quad regimens with HCV NS5A inhibitors, such as daclatasvir and ledipasvir, in combination with other direct-acting antiviral agents against other regions of HCV with or without peginterferon/ribavirin, could efficiently inhibit HCV replication according to HCV genotypes. These combinations might be a powerful tool for “difficult-to-treat” HCV-infected patients. “First generation” HCV NS5A inhibitors such as daclatasvir, ledipasvir and ABT-267, which are now in phase III clinical trials, could result in resistance mutations. “Second generation” NS5A inhibitors such as GS-5816, ACH-3102, and MK-8742, have displayed improvements in the genetic barrier while maintaining potency. HCV NS5A inhibitors are safe at low concentrations, which make them attractive for use despite low genetic barriers, although, in fact, HCV NS5A inhibitors should be used with HCV NS3/4A inhibitors, HCV NS5B inhibitors or peginterferon plus ribavirin. This review article describes HCV NS5A inhibitor resistance mutations and recommends that HCV NS5A inhibitors be used in combination regimens potent enough to prevent the emergence of resistant variants.

Bitter melon reduces head and neck squamous cell carcinoma growth by targeting c-Met signaling

Head and neck squamous cell carcinoma (HNSCC) remains difficult to treat, and despite of advances in treatment, the overall survival rate has only modestly improved over the past several years. Thus, there is an urgent need for additional therapeutic modalities. We hypothesized that treatment of HNSCC cells with a dietary product such as bitter melon extract (BME) modulates multiple signaling pathways and regresses HNSCC tumor growth in a preclinical model. We observed a reduced cell proliferation in HNSCC cell lines. The mechanistic studies reveal that treatment of BME in HNSCC cells inhibited c-Met signaling pathway. We also observed that BME treatment in HNSCC reduced phosphoStat3, c-myc and Mcl-1 expression, downstream signaling molecules of c-Met. Furthermore, BME treatment in HNSCC cells modulated the expression of key cell cycle progression molecules leading to halted cell growth. Finally, BME feeding in mice bearing HNSCC xenograft tumor resulted in an inhibition of tumor growth and c-Met expression. Together, our results suggested that BME treatment in HNSCC cells modulates multiple signaling pathways and may have therapeutic potential for treating HNSCC.

Update on the Development of Anti-Viral Agents Against Hepatitis C

Hepatitis C virus (HCV) infects nearly 170 million people worldwide and causes chronic hepatitis, cirrhosis, and hepatocellular carcinoma. The search for a drug regimen that maximizes efficacy and minimizes side effects is quickly evolving. This review will discuss a wide range of drug targets currently in all phases of development for the treatment of HCV. Direct data from agents in phase III/IV clinical trials will be presented, along with reported side-effect profiles. The mechanism of action of all treatments and resistance issues are highlighted. Special attention is given to available trial data supporting interferon-free treatment regimens. HCV has become an increasingly important public health concern, and it is important for physicians to stay up to date on the rapidly growing novel therapeutic options.

Animal models for hepatitis C

Hepatitis C remains a global epidemic. Approximately 3 % of the world's population suffers from chronic hepatitis C, which is caused by hepatitis C virus (HCV)-a positive sense, single-stranded RNA virus of the Flaviviridae family. HCV has a high propensity for establishing a chronic infection. If untreated chronic HCV carriers can develop severe liver disease including fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Antiviral treatment is only partially effective, costly, and poorly tolerated. A prophylactic or therapeutic vaccine for HCV does not exist. Mechanistic studies of virus-host interactions, HCV immunity, and pathogenesis as well as the development of more effective therapies have been hampered by the lack of a suitable small animal model. Besides humans, chimpanzees are the only species that is naturally susceptible to HCV infection. While experimentation in these large primates has yielded valuable insights, ethical considerations, limited availability, genetic heterogeneity, and cost limit their utility. In search for more tractable small animal models, numerous experimental approaches have been taken to recapitulate parts of the viral life cycle and/or aspects of viral pathogenesis that will be discussed in this review. Exciting new models and improvements in established models hold promise to further elucidate our understanding of chronic HCV infection.

Hepatitis C virus and hepatocellular carcinoma

Hepatitis C virus (HCV), a hepatotropic virus, is a single stranded-positive RNA virus of ~9,600 nt. length belonging to the Flaviviridae family. HCV infection causes acute hepatitis, chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC). It has been reported that HCV-coding proteins interact with host-cell factors that are involved in cell cycle regulation, transcriptional regulation, cell proliferation and apoptosis. Severe inflammation and advanced liver fibrosis in the liver background are also associated with the incidence of HCV-related HCC. In this review, we discuss the mechanism of hepatocarcinogenesis in HCV-related liver diseases.

Multi-step regulation of interferon induction by hepatitis C virus

Acute hepatitis C virus (HCV) infection evokes several distinct innate immune responses in host, but the virus usually propagates by circumventing these responses. Although a replication intermediate double-stranded RNA is produced in infected cells, type I interferon (IFN) induction and immediate cell death are largely blocked in infected cells. In vitro studies suggested that type I and III IFNs are mainly produced in HCV-infected hepatocytes if the MAVS pathway is functional, and dysfunction of this pathway may lead to cellular permissiveness to HCV replication and production. Cellular immunity, including natural killer cell activation and antigen-specific CD8 T-cell proliferation, occurs following innate immune activation in response to HCV, but is often ineffective for eradication of HCV. Constitutive dsRNA stimulation differs in output from type I IFN therapy, which has been an authentic therapy for patients with HCV. Host innate immune responses to HCV RNA/proteins may be associated with progressive hepatic fibrosis and carcinogenesis once persistent HCV infection is established in opposition to the IFN system. Hence, innate RNA sensing exerts pivotal functions against HCV genome replication and host pathogenesis through modulation of the IFN system. Molecules participating in the RIG-I and Toll-like receptor 3 pathways are the main targets for HCV, disabling the anti-viral functions of these IFN-inducing molecules. We discuss the mechanisms that abolish type I and type III IFN production in HCV-infected cells, which may contribute to understanding the mechanism of virus persistence and resistance to the IFN therapy.

Hepatitis C virus-mediated inhibition of cathepsin S increases invariant-chain expression on hepatocyte surface

Hepatocytes are the main source of hepatitis C virus (HCV) replication and contain the maximum viral load in an infected person. Chronic HCV infection is characterized by weak cellular immune responses to viral proteins. Cathepsin S is a lysosomal cysteine protease and controls HLA-DR-antigen complex presentation through the degradation of the invariant chain. In this study, we examined the effect of HCV proteins on cathepsin S expression and found it to be markedly decreased in dendritic cells (DCs) exposed to HCV or in hepatocytes expressing HCV proteins. The downregulation of cathepsin S was mediated by HCV core and NS5A proteins involving inhibition of the transcription factors interferon regulatory factor 1 (IRF-1) and upstream stimulatory factor 1 (USF-1) in gamma interferon (IFN-γ)-treated hepatocytes. Inhibition of cathepsin S by HCV proteins increased cell surface expression of the invariant chain. In addition, hepatocytes stably transfected with HCV core or NS5A inhibited HLA-DR expression. Together, these results suggested that HCV has an inhibitory role on cathepsin S-mediated major histocompatibility complex (MHC) class II maturation, which may contribute to weak immunogenicity of viral antigens in chronically infected humans.

CCL5: a double-edged sword in host defense against the hepatitis C virus

C-C motif ligand 5 (CCL5) facilitates induction of chemotaxis in immune cells and activation of hepatic stellate cells (HSC) at sites of liver inflammation during chronic hepatitis C virus (HCV) infection. Importantly, CCL5 participates in the establishment of T-helper 1 responses crucial in controlling liver disease and HCV infection outcome and demonstrates distinct gene expression patterns between the blood and the liver, stressing the importance of immunoregulatory networks differentially functioning between these compartments. This review illustrates the significance of CCL5-dependent pathways in HCV-related immunopathogenesis by elaborating on biological mechanisms interconnecting peripheral and tissue immunology, liver pathology, HSC activation, and interferon-α immunotherapy.

Characterisation of vaccine-induced, broadly cross-reactive IFN-γ secreting T cell responses that correlate with rapid protection against classical swine fever virus

Live attenuated C-strain classical swine fever viruses (CSFV) provide a rapid onset of protection, but the lack of a serological test that can differentiate vaccinated from infected animals limits their application in CSF outbreaks. Since immunity may precede antibody responses, we examined the kinetics and specificity of peripheral blood T cell responses from pigs vaccinated with a C-strain vaccine and challenged after five days with a genotypically divergent CSFV isolate. Vaccinated animals displayed virus-specific IFN-γ responses from day 3 post-challenge, whereas, unvaccinated challenge control animals failed to mount a detectable response. Both CD4(+) and cytotoxic CD8(+) T cells were identified as the cellular source of IFN-γ. IFN-γ responses showed extensive cross-reactivity when T cells were stimulated with CSFV isolates spanning the major genotypes. To determine the specificity of these responses, T cells were stimulated with recombinant CSFV proteins and a proteome-wide peptide library from a related virus, BVDV. Major cross-reactive peptides were mapped on the E2 and NS3 proteins. Finally, IFN-γ was shown to exert potent antiviral effects on CSFV in vitro. These data support the involvement of broadly cross-reactive T cell IFN-γ responses in the rapid protection conferred by the C-strain vaccine and this information should aid the development of the next generation of CSFV vaccines.

ISG56 and IFITM1 proteins inhibit hepatitis C virus replication

Hepatitis C virus (HCV) often leads to persistent infection. Interferon (IFN) and IFN-stimulated genes (ISGs) are amplified during HCV infection but fail to eliminate virus from the liver in a large number of infected patients. We have observed previously that HCV infection induces IFN-β production in immortalized human hepatocytes (IHH) as early as 24 h after infection, although virus replication is not inhibited. To gain insights on possible countermeasures of virus for the suppression of host antiviral response, the cellular transcriptional profiles of ISGs were examined after various treatments of IHH. The majority of ISGs were upregulated in IFN-treated IHH from the level for mock-treated cells. However, the comparison of ISG expression in IFN-treated IHH and IFN-pretreated, HCV genotype 2a-infected IHH indicated that virus infection suppresses the upregulation of a subset of effector molecules, including ISG56 and IFITM1. Similar results were observed for HCV-infected Huh7 cells. Subsequent study suggested that the exogenous expression of ISG56 or IFITM1 inhibits HCV replication in IHH or Huh7 cells, and the knockdown of these genes enhanced HCV replication. Further characterization revealed that the overexpression of these ISGs does not block HCV pseudotype entry into Huh7 cells. Taken together, our results demonstrated that ISG56 and IFITM1 serve as important molecules to restrict HCV infection, and they may have implications in the development of therapeutic modalities.

Hepatitis C Virus nonstructural 5A protein inhibits lipopolysaccharide-mediated apoptosis of hepatocytes by decreasing expression of Toll-like receptor 4

BACKGROUND

Hepatitis C virus (HCV) nonstructural protein 5A (NS5A) has been shown to modulate multiple cellular processes, including apoptosis. The aim of this study was to assess the effects of HCV NS5A on apoptosis induced by Toll-like receptor (TLR) 4 ligand, lipopolysaccharide (LPS).

METHODS

Apoptotic responses to TLR4 ligands and the expression of molecules involved in TLR signaling pathways in human hepatocytes were examined with or without expression of HCV NS5A.

RESULTS

HCV NS5A protected HepG2 hepatocytes against LPS-induced apoptosis, an effect linked to reduced TLR4 expression. A similar downregulation of TLR4 expression was observed in Huh-7-expressing genotype 1b and 2a. In agreement with these findings, NS5A inhibited the expression of numerous genes encoding for molecules involved in TLR4 signaling, such as CD14, MD-2, myeloid differentiation primary response gene 88, interferon regulatory factor 3, and nuclear factor-κB2. Consistent with a conferred prosurvival advantage, NS5A diminished the poly(adenosine diphosphate-ribose) polymerase cleavage and the activation of caspases 3, 7, 8, and 9 and increased the expression of anti-apoptotic molecules Bcl-2 and c-FLIP.

CONCLUSIONS

HCV NS5A downregulates TLR4 signaling and LPS-induced apoptotic pathways in human hepatocytes, suggesting that disruption of TLR4-mediated apoptosis may play a role in the pathogenesis of HCV infection.

Dendritic cells in hepatitis C infection: can they (help) win the battle?

Infection with hepatitis C virus (HCV) is a public health problem; it establishes a chronic course in ~85% of infected patients and increases their risk for developing liver cirrhosis, hepatocellular carcinoma, and significant extrahepatic manifestations. The mechanisms of HCV persistence remain elusive and are largely related to inefficient clearance of the virus by the host immune system. Dendritic cells (DCs) are the most efficient inducers of immune responses; they are capable of triggering productive immunity and maintaining the state of tolerance to self- and non-self antigens. During the past decade, multiple research groups have focused on DCs, in hopes of unraveling an HCV-specific DC signature or DC-dependent mechanisms of antiviral immunity which would lead to a successful HCV elimination strategy. This review incorporates the latest update in the current status of knowledge on the role of DCs in anti-HCV immunity as it relates to several challenging questions: (a) the phenotype and function of diverse DC subsets in HCV-infected patients; (b) the characteristics of non-human HCV infection models from the DCs' point of view; (c) how can in vitro systems, ranging from HCV protein- or peptide-exposed DC to HCV protein-expressing DCs, and in vivo systems, ranging from HCV protein-expressing transgenic mice to HCV-infected non-human primates, be employed to dissect the role of DCs in triggering/maintaining a robust antiviral response; and (d) the prospect of DC-based strategy for managing and finding a cure for HCV infection.

Lymphotropic HCV strain can infect human primary naïve CD4+ cells and affect their proliferation and IFN-γ secretion activity

BACKGROUND

Lymphotropic hepatitis C virus (HCV) infection of B and T cells might play an important role in the pathogenesis of hepatitis C. Recently, we showed that a lymphotropic HCV (SB strain) could infect established T-cell lines and B-cell lines. However, whether HCV replication interferes with cell proliferation and function in primary T lymphocytes is still unclear.

AIM

The aim of this study was to analyze whether HCV replication in primary T lymphocytes affected their development, proliferation, and Th1 commitment.

METHODS

SB strain cell culture supernatant (2 × 10(4) copies/ml HCV) was used to infect several kinds of primary lymphocyte subsets. Mock, UV-irradiated SB-HCV, JFH-1 strain, and JFH-1 NS5B mutant, which could not replicate in T cells, were included as negative controls. Carboxyfluorescein succinimidyl ester (CFSE) and CD45RA double staining was used to evaluate the proliferative activity of CD4(+)CD45RA(+)CD45RO(-) naïve CD4(+) cells. Interferon (IFN)-γ and interleukin (IL)-10 secretion assays magnetic cell sorting (MACS) were carried out.

RESULTS

Negative strand HCV RNA was detected in CD4(+), CD14(+), and CD19(+) cells. Among CD4(+) cells, CD4(+)CD45RA(+)RO(-) cells (naïve CD4(+) cells) were most susceptible to replication of the SB strain. The levels of CFSE and CD45RA expression gradually declined during cell division in uninfected cells, while HCV-infected naïve CD4(+) cells expressed higher levels of CFSE and CD45RA than Mock or UV-SB infected naïve CD4(+) cells. Moreover, the production of IFN-γ was significantly suppressed in SB-infected naïve CD4(+) cells.

CONCLUSIONS

Lymphotropic HCV replication suppressed proliferation and development, including that towards Th1 commitment, in human primary naïve CD4(+) cells.

Hepatitis B virus e antigen downregulates cytokine production in human hepatoma cell lines

Disease activities of hepatitis B are affected by the status of hepatitis B e antigen (HBeAg). The function of the hepatitis B virus (HBV) precore or HBeAg is unknown. We assumed that HBeAg blocks aberrant immune responses, although HBeAg is not required for viral assembly, infection, or replication. We examined the interaction of HBeAg and the immune system, including cytokine production. The inflammatory cytokine TNF, IL-6, IL-8, IL-12A, IFN-α1, and IFN-ß mRNA were downregulated in HBeAg-positive HepG2, which stably expresses HBeAg, compared to HBeAg-negative HepG2 cells. The results of real-time RT-PCR-based cytokine-related gene arrays showed the downregulation of cytokine and IFN production. We also observed inhibition of the activation of NF-κB- and IFN-ß-promoter in HBeAg-positive HepG2, as well as inhibition of IFN and IL-6 production in HBeAg-positive HepG2 cell culture fluids. HBeAg might modify disease progression by inhibiting inflammatory cytokine and IFN gene expression, while simultaneously suppressing NF-κB-signaling- and IFNß-promoter activation.

T helper type 1/T helper type 17-related cytokines in chronic hepatitis C patients before and after interferon and ribavirin therapy

OBJECTIVE

This study examined the T helper (Th) 1/Th17-related cytokines, interferon (IFN)-γ and interleukin (IL)-17 in the serum of biopsy-proven chronic hepatitis C patients before and after IFN and ribavirin therapy to address whether or not viral clearance is related to Th1/Th17 cytokines.

SUBJECTS AND METHODS

The serum levels of IFN-γ and IL-17 were assayed by ELISA on 26 patients with chronic hepatitic C virus (HCV) infection before the start and 3 months after treatment with pegylated IFN-α plus ribavirin and compared with sera from 15 normal control subjects.

RESULTS

IFN-γ and IL-17 levels are higher in the serum of patients with chronic hepatitis than in normal controls and these elevated levels were not directly correlated (r = -0.01, p = 0.96 for IFN-γ and r = -0.08, p = 0.66 for IL-17) to the viremic state of the HCV infection. In contrast to IL-17, IFN-γ showed significant reduction after 12 weeks of treatment with pegylated IFN plus ribavirin. However, IFN-γ and IL-17 serum levels were not significantly (p = 0.19 and = 0.70, respectively) different among responders and nonresponders for pegylated IFN plus ribavirin therapy.

CONCLUSION

Our findings suggest that the combined treatment with pegylated IFN-α and ribavirin downmodulates the secretion of key cytokine IFN-γ as early as 12 weeks after treatment in infected patients. These findings could encourage new exciting possibilities for immune-based interventions with the aim of restoring functional antiviral T cell responses combined with improved viral clearance.

Induction and evasion of innate antiviral responses by hepatitis C virus

Persistent hepatitis C virus infection is associated with progressive hepatic fibrosis and liver cancer. Acute infection evokes several distinct innate immune responses, but these are partially or completely countered by the virus. Hepatitis C virus proteins serve dual functions in replication and immune evasion, acting to disrupt cellular signaling pathways leading to interferon synthesis, subvert Jak-STAT signaling to limit expression of interferon-stimulated genes, and block antiviral activities of interferon-stimulated genes. The net effect is a multilayered evasion of innate immunity, which negatively influences the subsequent development of antigen-specific adaptive immunity, thereby contributing to virus persistence and resistance to therapy.