Add-on effects of fluvastatin in simeprevir/pegylated-interferon/ribavirin combination therapy for patients with genotype 1 hepatitis C virus infection: A randomized controlled study

BACKGROUND

The Japan Society of Hepatology guidelines indicate that hepatitis C virus (HCV) protease inhibitor combination therapy with simeprevir (SMV), pegylated-interferon (Peg-IFN), and ribavirin (RBV) is a therapeutic option for patients who fail to respond to a direct direct-acting antiviral-containing regimen. However, treatment outcomes have room for improvement. Fluvastatin (FLV) add-on treatment in Peg-IFN and RBV combination therapy for HCV-infected patients significantly improved the sustained virologic response (SVR), but the add-on effect of FLV on SMV combination therapy is not well understood.

METHODS

This was a prospective, randomized, multicenter study in which a total of 61 HCV genotype 1b-infected patients were recruited and 60 eligible patients were randomly allocated to two groups that received 12 weeks of SMV/Peg-IFN/RBV followed by 12 weeks of Peg-IFN/RBV with or without 24 weeks of FLV. The SVR rate and adverse events were compared between the two groups.

RESULTS

Thirty-one patients were allocated to the FLV add-on group and 29 patients were allocated to the control group. Baseline clinical factors, including median age, baseline platelet count, alanine aminotransferase level, HCV RNA titer, Fibrosis-4 index, and rate of IL28B minor genotype, were all similar between the two groups. The rapid virologic response, end-of-treatment response rates, SVR rates at 24 weeks after treatment, and safety profiles were also similar between the two groups.

CONCLUSIONS

This prospective, randomized, multicenter study indicated that FLV had no add-on effect when given with SMV/Peg-IFN/RBV combination therapy for genotype 1b HCV-infected patients.

Comparing the risk of hepatitis B virus reactivation between direct-acting antiviral therapies and interferon-based therapies for hepatitis C

Hepatitis B virus (HBV) reactivation has been reported during antihepatitis C treatment in patients with hepatitis C virus (HCV) and HBV co-infection. We aimed to evaluate the frequency and risk factors of HBV reactivation during anti-HCV therapy and compared those between interferon (IFN)-free direct-acting antiviral (DAA) therapies and IFN-based therapies. Three hundred and twenty-two patients with HCV infection receiving anti-HCV therapy were retrospectively screened. The baseline HBV infection statuses of all eligible patients and the HBV-DNA level of all patients with current or previous HBV infection were examined at the end of treatment. In patients with baseline anti-HBs positivity, changes in anti-HBs titre were evaluated. Of 287 patients who met the inclusion criteria, 157 had current (n=4) or previous (n=153) HBV infection; 85 were treated with IFN-free DAA therapies and 72 were treated with IFN-based therapies. Six patients experienced HBV reactivation (n=2) or HBV reappearance (n=4) after IFN-free DAA therapies, while no patient developed HBV reactivation after IFN-based therapies. The risk factors of HBV reactivation or reappearance were DAA therapies and a reduction in anti-HBs titre to <12 mIU mL^-1 by the end of treatment. The decline changes of anti-HBs titre were significantly higher in patients treated with DAA therapies. Although HBV reactivation hepatitis was not observed, three of four patients with HBV reactivation or reappearance after achieving HCV eradication had viremia 8 weeks after completion of therapy. A significant proportion of patients develop HBV reactivation or reappearance without hepatitis after IFN-free DAA therapies. Low levels of anti-HBs and their decrease to <12 mIU mL^-1 after treatment are significant risk factors for HBV reactivation or reappearance.

Fibroblast growth factor-2-mediated FGFR/Erk signaling supports maintenance of cancer stem-like cells in esophageal squamous cell carcinoma

In esophageal squamous cell carcinoma (ESCC), a subset of cells defined by high expression of CD44 and low expression of CD24 has been reported to possess characteristics of cancer stem-like cells (CSCs). Novel therapies directly targeting CSCs have the potential to improve prognosis of ESCC patients. Although fibroblast growth factor-2 (FGF-2) expression correlates with recurrence and poor survival in ESCC patients, the role of FGF-2 in regulation of ESCC CSCs has yet to be elucidated. We report that FGF-2 is significantly upregulated in CSCs and significantly increases CSC content in ESCC cell lines by inducing epithelial-mesenchymal transition (EMT). Conversely, the FGFR inhibitor, AZD4547, sharply diminishes CSCs via induction of mesenchymal-epithelial transition. Further experiments revealed that MAPK/Erk kinase (Mek)/extracellular signal-regulated kinases (Erk) pathway is crucial for FGF-2-mediated CSC regulation. Pharmacological inhibition of FGF receptor (FGFR)-mediated signaling via AZD4547 did not affect CSCs in Ras mutated cells, implying that Mek/Erk pathway, downstream of FGFR signaling, might be an important regulator of CSCs. Indeed, the Mek inhibitor, trametinib, efficiently suppressed ESCC CSCs even in the context of Ras mutation. Consistent with these findings in vitro, xenotransplantation studies demonstrated that inhibition of FGF-2-mediated FGFR/Erk signaling significantly delayed tumor growth. Taken together, these findings indicate that FGF-2 is an essential factor regulating CSCs via Mek/Erk signaling in ESCC. Additionally, inhibition of FGFR and/or Mek signaling represents a potential novel therapeutic option for targeting CSCs in ESCC.

Safety and efficacy of daclatasvir and asunaprevir in hepatitis C virus-infected patients with renal impairment

AIM

Hepatitis C virus (HCV) infection is a risk factor for end-stage renal disease, renal graft failure, and hemodialysis patient mortality. However, the efficacy of direct-acting antiviral therapy for HCV-infected patients with renal impairment is unclear. Additionally, the promising NS5B inhibitor sofosbuvir has not been recommended for patients with severe renal impairment. In this prospective, multicenter study, we evaluated the efficacy and safety of daclatasvir and asunaprevir combination therapy, with a focus on patients with renal impairment.

METHODS

The study included 322 genotype 1 HCV-infected patients who received daclatasvir and asunaprevir combination therapy. The safety and sustained virological response was examined at 12 weeks after the end of treatment and safety was evaluated according to renal function.

RESULTS

Of 322 patients, 5% (16/322) and 2.5% (8/322) had chronic kidney disease stage G3b (estimated glomerular filtration rate [eGFR], 30-44 mL/min/1.73 m² ) and stage G4/5 (eGFR, 15-29/<15 mL/min/1.73 m² ), respectively. Baseline presence of the NS5A resistance-associated variant, previous simeprevir treatment, and HCV RNA titers, which were predictors of a sustained viral response, were similar between patients with eGFR <45 mL/min/1.73 m² and eGFR >45 mL/min/1.73 m² . Notably, the 12-week sustained viral response rate was comparable in patients with eGFR <45 mL/min/1.73 m² (100%, 24/24) and those with eGFR >45 mL/min/1.73 m² (88.9%, 265/298; P = 0.07). Treatment discontinuation rates and adverse events, including alanine aminotransferase elevation, anemia, and renal disorders, were similar between the two groups.

CONCLUSION

Daclatasvir and asunaprevir combination therapy for patients with renal dysfunction was highly effective and safe.

Investigation of the utility of various diagnostic guidelines for Wilson's disease

Wilson's disease is one of many potential differential diagnoses in patients with unknown liver injury or liver cirrhosis. Many patients are diagnosed in early childhood, but rare cases may not be revealed until adulthood, and of these, most present with liver cirrhosis. While some patients can be diagnosed by the examination of serum ceruloplasmin and urinary copper levels, there are patients in whom ATP7B genetic testing and hepatic copper content measurement are indicated. Diagnostic guidelines for Wilson's disease were proposed by the American Association for the Study of Liver Diseases in 2008, the European Association for the Study of the Liver in 2012, and the Japan Society of Hepatology along with affiliated societies in 2015. Even in patients in whom making a diagnosis was problematic, we were able to establish confirmation of Wilson's disease in patients with unknown adulthood liver dysfunction using these established guidelines. In this paper, we present the cases of patients with Wilson's disease treated by the administration of copper chelating agents in our department using diagnostic criteria and further provide flow charts of each guideline. We also report the utility of this approach.

Combination of neutrophil-to-lymphocyte ratio and early des-γ-carboxyprothrombin change ratio as a useful predictor of treatment response for hepatic arterial infusion chemotherapy against advanced hepatocellular carcinoma

AIM

Hepatic arterial infusion chemotherapy (HAIC) is a potent therapeutic option for advanced hepatocellular carcinoma (HCC). However, there are few known predictive factors of treatment response to HAIC. We clarified the most accurate predictive factors early on in treatment.

METHODS

Study subjects were 70 patients with advanced HCC who had been treated with HAIC. We assessed the relationships between patient characteristics, change ratios of early tumor markers, tumor response, progression-free survival (PFS), and overall survival.

RESULTS

After two courses of HAIC, 1 (1.4%), 16 (22.9%), 30 (42.8%), and 23 (32.9%) of the 70 patients showed complete response, partial response, stable disease, and progressive disease, respectively. Overall survival was related to Child-Turcotte-Pugh score, extrahepatic metastasis, and the des-γ-carboxyprothrombin (DCP) response. Univariate and multivariate analyses identified the neutrophil-to-lymphocyte ratio (NLR) and DCP response as significant determinants of treatment response and PFS. Progression-free survival with a low NLR (<2.87) was significantly longer than with a high NLR (median, 8.4 months vs. 2.8 months, respectively). Progression-free survival was 7.2 months for patients with a responsive DCP (<0.7) and 2.3 months for an unresponsive DCP (≥0.7). Additionally, even with baseline high NLR, patients with responsive DCP achieved better PFS.

CONCLUSION

Baseline NLR and early DCP response were significant predictors of treatment response and PFS after HAIC for patients with advanced HCC. The combination of baseline NLR and early DCP response could be accurate and useful predictive factors of response to HAIC and could help optimize treatments for patients with advanced HCC.

Interferon-free therapy with sofosbuvir plus ribavirin for successful treatment of genotype 2 hepatitis C virus with lichen planus: a case report

Hepatitis C virus (HCV) infection remains the main cause of liver disease and can lead to chronic hepatitis, cirrhosis, and hepatocellular carcinoma. HCV may also develop extrahepatic manifestations in the skin, eyes, joints, kidneys, nervous system, and immune system. In fact, several studies reported that up to 70% of HCV patients experienced extrahepatic manifestations. Lichen planus (LP), which is an immune system disorder that is triggered by viral infections, allergens, and stress, can affect the skin, mouth, nails, and scalp. The association of LP with HCV has been reported, but the effect of HCV treatment on LP remission is controversial. We encountered a 53-year-old man with HCV genotype 2a and LP that were successfully treated with sofosbuvir and ribavirin for 12 weeks. After treatment, he achieved sustained virological response against HCV and remission of erosive LP lesions on the lip. In the era of interferon (IFN)-based treatment for HCV, exacerbation of autoimmune diseases is a common adverse event. Therefore, use of an IFN-free regimen of direct-acting antivirals for HCV might prevent the extrahepatic manifestation of an immune disorder.

Micro/extended-nano sampling interface from a living single cell

Single-cell analysis is of increasing importance in many fields, but is challenging due to the ultra-small volumes (picoliters) of single cells. Indeed, analysis of a specific analyte might require the analysis of a single molecule or several molecules. Analytical processes usually include sampling, chemical processing, and detection. Although several papers have reported chemical processing and detection methods for single cells, a sampling method compatible with maintaining the viability of a single cell during sampling has yet to be developed. Here, we propose a femtoliter sampling method from a living single cell using micro/nanofluidic device technology. The sampling of 39 fL of cytoplasm from a single human aortic endothelial cell was demonstrated and its viability after sampling was confirmed.

Novel Treatment of Hepatitis C Virus Infection for Patients with Renal Impairment

Prevalence of hepatitis C virus (HCV) infection is high in patients with end-stage renal dysfunction, including patients undergoing hemodialysis (HD). The HCV infection itself can cause glomerulonephritis and puts individuals at increased risk of developing end-stage renal disease; fortunately, successful HCV eradication sometimes restore HCV-related renal dysfunction. Moreover, the prognosis of dialysis patients infected with HCV is significantly worse and the renal allograft survival in HCV-infected patients is also worse than in dialysis patients without HCV infection. If life prognosis is favorable, therefore, anti-HCV therapy is strongly recommended for HCV-infected patients with severe renal dysfunction. The standard therapy for HCV-infected patients with severe renal dysfunction has historically been interferon-based therapy. However, this therapy remains ineffective in achieving high, sustained viral response rates and the rate of adverse events and treatment discontinuation due to treatment-induced adverse events continues to be high in patients with severe renal dysfunction. Safe and effective anti-HCV therapies are urgently needed, and crucial, for patients with severe renal dysfunction. Recently, direct-acting antivirals (DAAs) that specifically target viral proteins have been developed, and these targets include the NS3, NS5A, and NS5B of HCV. Clinical trials have revealed high efficacy and safety of the DAA-based therapies, but patients with severe renal dysfunction were not included in the majority of these trials. However, several recent reports have shown high efficacy and safety for some regimens of DAA combination therapy for HCV-infected patients with severe renal dysfunction. In this review, we discuss novel treatments for HCV-infected patients with severe renal dysfunction and the pharmacokinetics of these drugs.

Prevalence and characteristics of naturally occurring sofosbuvir resistance-associated variants in patients with hepatitis C virus genotype 1b infection

AIM

Sofosbuvir (SOF), a nucleotide analog pro-drug, targets hepatitis C virus (HCV) NS5B polymerase and shows potential for treating HCV infection, given its high efficacy and good barrier to resistance. However, in addition to the rare resistant-associated variant (RAV) of non-structural protein NS5B S282T, several new potential RAVs of SOF have been reported, especially related to HCV genotype 1b. However, the prevalence and characteristics of these RAVs have not been clarified.

METHODS

We analyzed the prevalence of variants in the NS3/NS5A/NS5B regions in 96 patients treated with simeprevir (SMV) combination therapy, and the prevalence of RAVs in patients showing treatment failure was determined by direct- or deep-sequencing methods. Associations between these potential RAVs and clinical factors were also analyzed.

RESULTS

Prevalence of NS5B RAV C316N was high (46.9%, 45/96), whereas that of NS5B L159F was relatively low (1.04%, 1/96); however, deep sequencing showed that 30.0% of patients with C316N also had NS5B RAV L159F. Additionally, there was no significant relationship between the existence of potential NS5B and NS5A or NS3 RAVs. However, the presence of NS5B C316N was significantly associated with an HCV core amino acid 91 substitution. No significant difference was detected between each RAV and sustained virological response in simeprevir combination therapy.

CONCLUSION

We provide clear evidence of the high prevalence of two potential naturally occurring NS5B RAVs (C316N and L159F) in Japan. It may be important to pay particular attention to these new potential RAVs, especially when using SOF-based therapy in patients with RAVs due to previous direct-acting antiviral therapy failure.

Anti-adipogenic and antiviral effects of l-carnitine on hepatitis C virus infection

Hepatitis C virus (HCV) has been reported to hijack fatty acid metabolism in infected hepatocytes, taking advantage of lipid droplets for virus assembly. In this study, we analyzed the anti-HCV activity of l-carnitine, a substance involved in the transport of fatty acids into mitochondria. JFH-1 or HCV replicon-transfected Huh7.5.1 cells were treated with or without l-carnitine to examine its anti-HCV effects. The effects of l-carnitine on HCV entry, HCV-induced adipogenesis and lipid droplet formation, and HCV-induced oxidative stress were examined. Treatment of JFH-1-infected cells with l-carnitine inhibited HCV propagation in a concentration-dependent manner. In contrast, l-carnitine had no anti-HCV activity in the HCV replicon system, which is lacking viral assembly. In addition, l-carnitine did not affect HCV entry. However, l-carnitine treatment decreased intracellular lipid droplets, which are crucial for HCV assembly in JFH-1-infected cells. The expression level of CPT-1 was decreased in JFH-1-infected cells, and l-carnitine treatment restored this expression. HCV-infected cells exhibited increased production of reactive oxygen species and glutathione oxidation. l-carnitine decreased oxidative stress induced by JFH-1-infection, as shown by glutathione/glutathione disulfide assays and MitoSOX staining. l-carnitine exhibited anti-HCV activity, possibly by inhibiting HCV assembly and through its anti-adipogenic activity in HCV-infected cells. Moreover, l-carnitine has antioxidant properties in HCV-infected hepatocytes. Overall, these results indicated that l-carnitine may be an effective adjunctive agent in antiviral therapies to treat chronic hepatitis C. J. Med. Virol. 89:857-866, 2017. © 2016 Wiley Periodicals, Inc.

Hepatitis B: progress in understanding chronicity, the innate immune response, and cccDNA protection

Hepatitis B virus (HBV) infection is a serious health threat around the world. Despite the availability of an effective hepatitis B vaccine, the number of HBV carriers is estimated to be as high as 240 million worldwide. Global mortality due to HBV-related liver diseases such as chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma (HCC) may be as high as 1 million deaths per year. HBV is transmitted via blood and body fluids, and is much more infectious than both human immunodeficiency virus (HIV) and hepatitis C virus. While HBV infection exhibits a variety of clinical presentations, even asymptomatic carriers can develop HCC without liver fibrosis. Current therapeutic options against HBV include pegylated interferon (Peg-IFN) and nucleos(t)ide reverse transcriptase inhibitors (NRTIs), with clinical studies showing a significant association between loss of HBV DNA and a decrease in cancer risk. However, the ultimate goal of HBV therapy is a complete cure of HBV-including the elimination of covalently closed circular DNA (cccDNA)-in order to further decrease the risk of developing HCC. The development of hepatitis B is associated with the host immune response to virus-infected hepatocytes, as HBV is understood to lack direct cytotoxicity. While HBV-specific CD8+ T cells are thus involved in hepatitis development, they also play an important role in eliminating HBV infection. Indeed, the innate immune response during the initial phase of HBV infection is essential to the induction of acquired immunity. However, the innate immune response to HBV infection, including the roles of specific immunocompetent cells and associated molecules, is not well understood. In this review, we focus on the current understanding of the mechanisms underlying hepatitis development by HBV infection. We also address the mechanisms by which HBV protects cccDNA.

Hepatitis B virus X protein impairs α-interferon signaling via up-regulation of suppressor of cytokine signaling 3 and protein phosphatase 2A

Hepatitis B Virus (HBV) causes liver cirrhosis and hepatocellular carcinoma. Standard therapy includes treatment with interferon (IFN); however, its efficacy is limited. HBV has been reported to impair IFN signaling; however, the mechanism is unclear. Here, the relationship between HBV X protein (HBx) and IFN signaling was investigated by establishing HepG2 cells, stably expressing HBx (HepG2/HBx) via retrovirus-mediated gene transfer. Subsequently, IFN negative-regulator expression and its mechanism were studied. HepG2/HBx cells showed reduced expression of IFN-stimulated genes and expressed higher levels of suppressor of cytokine signaling 3 (SOCS3) and protein phosphatase 2A (PP2A) suppressor compared with control cells. Knockdown of SOCS3 and PP2A restored IFN sensitivity. Moreover, HepG2/HBx cells showed higher phosphorylation levels of signal transducers and activators of transcription 3 and endoplasmic reticulum stress, which are inducers of SOCS3 and PP2A, respectively. Additionally, HBx-knockdown restored IFN sensitivity in HepG2.2.15.7 cells. It was also confirmed that SOCS3 and PP2A expression levels were up-regulated in the liver of patients with HBV infection. The results of this study demonstrated that HBx impairs IFN signaling via increased expression of SOCS3 and PP2A, a novel mechanistic insight, providing a potential therapeutic target to enhance the efficiency of IFN therapy. J. Med. Virol. 89:267-275, 2017. © 2016 Wiley Periodicals, Inc.

Intratumoral artery on contrast-enhanced computed tomography imaging: differentiating intrahepatic cholangiocarcinoma from poorly differentiated hepatocellular carcinoma

AIM

Differentiating intrahepatic cholangiocarcinoma (ICC) from poorly differentiated hepatocellular carcinoma (p-HCC) is often difficult, but it is important for providing appropriate treatments. The purpose of this study was to examine the features differentiating ICC from p-HCC on contrast-enhanced dynamic-computed tomography (CT).

METHODS

This study examined 42 patients with pathologically confirmed ICC (n = 19) or p-HCC (n = 23) for which contrast-enhanced dynamic CT data were available. CT images were analyzed for enhancement patterns during the arterial phase, washout pattern, delayed enhancement, satellite nodules, capsular retraction, lesion shape, and presence of an intratumoral hepatic artery, intratumoral hepatic vein, intratumoral portal vein, and bile duct dilation around the tumor, portal vein tumor thrombus, lobar atrophy, or lymphadenopathy.

RESULTS

Univariate analysis revealed the presence of rim enhancement (p = 0.037), lobulated shape (p = 0.004), intratumoral artery (p < 0.001), and bile duct dilation (p = 0.006) as parameters significantly favoring ICC, while a washout pattern significantly favored p-HCC (p < 0.001). Multivariate analysis revealed intratumoral artery as a significant, independent variable predictive of ICC (p = 0.037), and 15 ICCs (78.9%) showed this feature. Washout pattern was a significant, independent variable favoring p-HCC (p = 0.049), with 15 p-HCCs (65.2%) showing this feature.

CONCLUSION

The presence of an intratumoral artery in the arterial phase on contrast-enhanced dynamic CT was a predictable finding for ICC, and the presence of a washout pattern was a predictable finding for p-HCC, differentiating between ICC and p-HCC.

A pivotal role of Krüppel-like factor 5 in regulation of cancer stem-like cells in hepatocellular carcinoma

In hepatocellular carcinoma (HCC), there exists a highly tumorigenic subset of cells defined by high expression of CD44 and CD133 that has been reported to contain cancer stem-like cells (CSCs). Krüppel-like factor 5 (KLF5) regulates many factors involved in cell cycle, migration, inflammation, angiogenesis and stemness and has cancer-promoting effects in some cancers. While some reports have indicated that KLF5 may have important roles in regulation of CSCs, what role, if any, KLF5 plays in regulation of CSCs in HCC remains to be elucidated. Flow cytometric analysis of CD44 and CD133 in HCC cell lines revealed subpopulations of CD44(High)/CD133(High) and CD44(Low)/CD133(Low) cells. We subsequently sorted these subpopulations and identified KLF5 as a gene that is significantly upregulated in CD44(High)/CD44(High) cells via RNA sequencing using next generation sequencing technology. Moreover, KLF5 overexpression enriched the CD44(High)/CD133(High) subpopulation and, consistent with the up-regulation of CD44(High)/CD133(High) cells, KLF5 overexpressing cells were more resistant to anti-cancer drugs and displayed enhanced colony-formation capacity. By contrast, knock-down of KLF5 by siRNA diminished the CD44(High)/CD133(High) subpopulation. When KLF5 was acetylated by TGF-β1, the KLF5-mediated CD44(High)/CD133(High) subpopulation enrichment was abrogated. Oppositely, ectopic expression of an acetylation-deficient KLF5 mutant further increased CD44(High)/CD133(High) subpopulations as compared to cell expressing wild-type KLF5. These findings provide novel mechanistic insight into a pivotal role for KLF5 in the regulation of CSCs in HCC.

Hepatitis C virus variants resistant to macrocyclic NS3-4A inhibitors subvert IFN-β induction by efficient MAVS cleavage

BACKGROUND & AIMS

The hepatitis C virus (HCV) NS3-4A protease is essential for the HCV life cycle and a prime target of antiviral treatment strategies. Protease inhibitors, however, are limited by emergence of resistance-associated amino acid variants (RAVs). The capacity to cleave and inactivate mitochondrial antiviral-signaling protein (MAVS) in the RIG-I-signaling pathway is a cardinal feature of NS3-4A, by which HCV blocks induction of interferon-(IFN)-β, thereby promoting viral persistence. Here, we aimed to investigate the impact of NS3-4A RAVs on MAVS cleavage.

METHODS

The impact of NS3-4A RAVs on MAVS cleavage was assessed using immunoblot analyses, luciferase reporter assays and molecular dynamics simulations to study the underlying molecular principles. IFN-β was quantified in serum from patients with different NS3-4A RAVs.

RESULTS

We show that macrocyclic NS3-4A RAVS with substitutions at residue D168 of the protease result in an increased capacity of NS3-4A to cleave MAVS and suppress IFN-β induction compared with a comprehensive panel of RAVs and wild type HCV. Mechanistically, we show the reconstitution of a tight network of electrostatic interactions between protease and the peptide substrate that allows much stronger binding of MAVS to D168 RAVs than to the wild-type protease. Accordingly, we could show IFN-β serum levels to be lower in patients with treatment failure due to the selection of D168 variants compared to R155 RAVs.

CONCLUSIONS

Our data constitutes a proof of concept that the selection of RAVs against specific classes of direct antivirals can lead to the predominance of viral variants with possibly adverse pathogenic characteristics.

Vitamin D receptor and Jak-STAT signaling crosstalk results in calcitriol-mediated increase of hepatocellular response to IFN-α

Recent clinical research suggests a role for vitamin D in the response to IFN-α-based therapy of chronic hepatitis C. Therefore, we aimed to explore the underlying mechanisms in vitro. Huh-7.5 cells harboring subgenomic hepatitis C virus (HCV) replicons or infected with cell culture-derived HCV were exposed to bioactive 1,25-dihydroxyvitamin D3 (calcitriol) with or without IFN-α. In these experiments, calcitriol alone had no effect on the HCV life cycle. However, calcitriol enhanced the inhibitory effect of IFN-α on HCV replication. This effect was based on a calcitriol-mediated increase of IFN-α-induced gene expression. Further mechanistic studies revealed a constitutive inhibitory interaction between the inactive vitamin D receptor (VDR) and Stat1, which was released upon stimulation with calcitriol and IFN-α. As a consequence, IFN-α-induced binding of phosphorylated Stat1 to its DNA target sequences was enhanced by calcitriol. Importantly, and in line with these observations, silencing of the VDR resulted in an enhanced hepatocellular response to IFN-α. Our findings identify the VDR as a novel suppressor of IFN-α-induced signaling through the Jak-STAT pathway.

Quantitative proteomics identifies the membrane-associated peroxidase GPx8 as a cellular substrate of the hepatitis C virus NS3-4A protease

The hepatitis C virus (HCV) NS3-4A protease is not only an essential component of the viral replication complex and a prime target for antiviral intervention but also a key player in the persistence and pathogenesis of HCV. It cleaves and thereby inactivates two crucial adaptor proteins in viral RNA sensing and innate immunity, mitochondrial antiviral signaling protein (MAVS) and TRIF, a phosphatase involved in growth factor signaling, T-cell protein tyrosine phosphatase (TC-PTP), and the E3 ubiquitin ligase component UV-damaged DNA-binding protein 1 (DDB1). Here we explored quantitative proteomics to identify novel cellular substrates of the NS3-4A protease. Cell lines inducibly expressing the NS3-4A protease were analyzed by stable isotopic labeling using amino acids in cell culture (SILAC) coupled with protein separation and mass spectrometry. This approach identified the membrane-associated peroxidase GPx8 as a bona fide cellular substrate of the HCV NS3-4A protease. Cleavage by NS3-4A occurs at Cys 11, removing the cytosolic tip of GPx8, and was observed in different experimental systems as well as in liver biopsies from patients with chronic HCV. Overexpression and RNA silencing studies revealed that GPx8 is involved in viral particle production but not in HCV entry or RNA replication.

CONCLUSION

We provide proof-of-concept for the use of quantitative proteomics to identify cellular substrates of a viral protease and describe GPx8 as a novel proviral host factor targeted by the HCV NS3-4A protease.

Neutralizing antibodies induced by cell culture-derived hepatitis C virus protect against infection in mice

BACKGROUND & AIMS

Hepatitis C virus (HCV) infection is a major cause of liver cancer, so strategies to prevent infection are needed. A system for cell culture of infectious HCV particles (HCVcc) has recently been established; the inactivated HCVcc particles might be used as antigens in vaccine development. We aimed to confirm the potential of HCVcc as an HCV particle vaccine.

METHODS

HCVcc derived from the J6/JFH-1 chimeric genome was purified from cultured cells by ultrafiltration and ultracentrifugation purification steps. Purified HCV particles were inactivated and injected into female BALB/c mice with adjuvant. Sera from immunized mice were collected and their ability to neutralize HCV was examined in naive Huh7.5.1 cells and urokinase-type plasminogen activator-severe combined immunodeficiency mice (uPA(+/+)-SCID mice) given transplants of human hepatocytes (humanized livers).

RESULTS

Antibodies against HCV envelope proteins were detected in the sera of immunized mice; these sera inhibited infection of cultured cells with HCV genotypes 1a, 1b, and 2a. Immunoglobulin G purified from the sera of HCV-particle-immunized mice (iHCV-IgG) inhibited HCV infection of cultured cells. Injection of IgG from the immunized mice into uPA(+/+)-SCID mice with humanized livers prevented infection with the minimum infectious dose of HCV.

CONCLUSIONS

Inactivated HCV particles derived from cultured cells protect chimeric liver uPA(+/+)-SCID mice against HCV infection, and might be used in the development of a prophylactic vaccine.