Proteomics identifies complement protein signatures in patients with alcohol-associated hepatitis.

Diagnostic challenges continue to impede development of effective therapies for successful management of alcohol-associated hepatitis (AH), creating an unmet need to identify noninvasive biomarkers for AH. In murine models, complement contributes to ethanol-induced liver injury. Therefore, we hypothesized that complement proteins could be rational diagnostic/prognostic biomarkers in AH. Here, we performed a comparative analysis of data derived from human hepatic and serum proteome to identify and characterize complement protein signatures in severe AH (sAH). The quantity of multiple complement proteins was perturbed in liver and serum proteome of patients with sAH. Multiple complement proteins differentiated patients with sAH from those with alcohol cirrhosis (AC) or alcohol use disorder (AUD) and healthy controls (HCs). Serum collectin 11 and C1q binding protein were strongly associated with sAH and exhibited good discriminatory performance among patients with sAH, AC, or AUD and HCs. Furthermore, complement component receptor 1-like protein was negatively associated with pro-inflammatory cytokines. Additionally, lower serum MBL associated serine protease 1 and coagulation factor II independently predicted 90-day mortality. In summary, meta-analysis of proteomic profiles from liver and circulation revealed complement protein signatures of sAH, highlighting a complex perturbation of complement and identifying potential diagnostic and prognostic biomarkers for patients with sAH.

Tofacitinib is Effective in Treating Refractory Immune Checkpoint Inhibitor Hepatitis.

Immune checkpoint inhibitors (ICI) have improved metastatic melanoma outcomes; however, toxicities, such as hepatitis, can be dose-limiting or even fatal.1 Systemic glucocorticoids and antimetabolite immunosuppressive medications remain the mainstay of treatment for ICI-hepatitis, but options for patients refractory to these therapies are limited.2 Herein we present 3 cases of glucocorticoid-refractory ICI-hepatitis treated with tofacitinib, an inhibitor of Janus kinase (JAK) 1 and 3. These patients represent consecutive patients referred to the Massachusetts General Hospital Severe Immunotherapy Complications service who were determined by our experts to have treatment failure with systemic glucocorticoid and antimetabolite combination therapy between August 2022 and September 2023.3 These were the only 3 patients managed by the Severe Immunotherapy Complications service who were treated with tofacitinib for ICI-hepatitis during that time.

Serum Fibroblast Growth Factor-21 Discriminates Between Decompensated Alcohol-Associated Cirrhosis and Severe Alcohol-Associated Hepatitis.

INTRODUCTION: We hypothesized that fibroblast growth factor-21 (FGF-21) would be highly expressed in patients with alcohol-associated hepatitis (AH) and could be a novel and biologically relevant predictive biomarker to reliably distinguish severe AH and decompensated alcohol-associated cirrhosis (AC). METHODS: We identified a discovery cohort of 88 subjects with alcohol-associated liver disease (ALD) of varying disease severity from our ALD repository. Our validation cohort consisted of 37 patients with a biopsy-proven diagnosis of AH, AC, or absence of ALD with Model for End-Stage Liver Disease scores ≥10. Serum from both groups during index hospitalization was assayed for FGF-21 by ELISA. We performed receiver operating characteristic analysis and prediction modeling in both cohorts to discriminate between AH and AC in high Model for End-Stage Liver Disease (≥20) patients. RESULTS: In both cohorts, FGF-21 concentrations were highest in subjects with moderate to severe AH compared with those having alcohol use disorder or AC (mean: 2,609 pg/mL, P < 0.0001). The discovery cohort area under the curve of FGF-21 between AH and AC was 0.81 (95% confidence interval: 0.65-0.98, P < 0.01). In the validation cohort, FGF-21 levels were higher in severe AH compared with AC (3,052 vs 1,235 pg/mL, P = 0.03), and the area under the curve was 0.76 (95% confidence interval: 0.56-0.96, P < 0.03). A survival analysis showed that patients with FGF-21 serum levels in the second interquartile had the highest survival compared with all other quartiles. DISCUSSION: FGF-21 performs well as a predictive biomarker to distinguish severe AH from AC and may be helpful in the management and clinical investigation of patients with severe alcohol-associated liver diseases.

Trends in gestational age at delivery for intrahepatic cholestasis of pregnancy and adoption of society guidelines.

BACKGROUND: Intrahepatic cholestasis of pregnancy is associated with a significant risk of stillbirth, which contributes to variation in clinical management. Recent Society for Maternal-Fetal Medicine guidance recommends delivery at 36 weeks of gestation for patients with serum bile acid levels of >100 µmol/L, consideration for delivery between 36 and 39 weeks of gestation stratified by bile acid level, and against preterm delivery for those with clinical features of cholestasis without bile acid elevation. OBJECTIVE: This study aimed to investigate institutional practices before the publication of the new delivery timing recommendations to establish the maternal and neonatal effects of late preterm, early-term, and term deliveries in the setting of cholestasis. STUDY DESIGN: This study examined maternal and neonatal outcomes of 441 patients affected by cholestasis delivering 484 neonates in a 4-hospital system over a 30-month period. Logistic and linear regression analyses were performed to assess neonatal outcomes concerning peak serum bile acid levels at various gestational ages controlling for maternal comorbidities, multiple pregnancies, and neonatal birthweight. RESULTS: With the clinical flexibility afforded by the new guidelines, pregnancy prolongation to term may have been achieved in 91 patients (21%), and 286 patients (74%) with bile acid elevation could have delivered at a later gestational age. Preterm deliveries of patients with bile acid levels of >10 µmol/L were associated with higher rates of neonatal intensive care unit admission and adverse neonatal outcomes than early-term deliveries. CONCLUSION: Study data suggested an opportunity for education and practice change to reflect current Society for Maternal-Fetal Medicine guidelines in efforts to reduce potential neonatal morbidities associated with late preterm deliveries among pregnancies affected by cholestasis.

The circulating proteomic signature of alcohol-associated liver disease.

Despite being a leading cause of advanced liver disease, alcohol-associated liver disease (ALD) has no effective medical therapies. The circulating proteome, which comprises proteins secreted by different cells and tissues in the context of normal physiological function or in the setting of disease and illness, represents an attractive target for uncovering novel biology related to the pathogenesis of ALD. In this work, we used the aptamer-based SomaScan proteomics platform to quantify the relative concentration of over 1300 proteins in a well-characterized cohort of patients with the spectrum of ALD. We found a distinct circulating proteomic signature that correlated with ALD severity, including over 600 proteins that differed significantly between ALD stages, many of which have not previously been associated with ALD to our knowledge. Notably, certain proteins that were markedly dysregulated in patients with alcohol-associated hepatitis were also altered, to a lesser degree, in patients with subclinical ALD and may represent early biomarkers for disease progression. Taken together, our work highlights the vast and distinct changes in the circulating proteome across the wide spectrum of ALD, identifies potentially novel biomarkers and therapeutic targets, and provides a proteomic resource atlas for ALD researchers and clinicians.

Hepatitis B and Hepatitis C Virus Infection Promote Liver Fibrogenesis through a TGF-ß1-Induced OCT4/Nanog Pathway.

Hepatitis B virus (HBV)/hepatitis C virus (HCV) coinfection accelerates liver fibrosis progression compared with HBV or HCV monoinfection. Octamer binding transcription factor 4 (OCT4) and Nanog are direct targets of the profibrogenic TGF-ß1 signaling cascade. We leveraged a coculture model to monitor the effects of HBV and HCV coinfection on fibrogenesis in both sodium taurocholate cotransporting polypeptide-transfected Huh7.5.1 hepatoma cells and LX2 hepatic stellate cells (HSCs). We used CRISPR-Cas9 to knock out OCT4 and Nanog to evaluate their effects on HBV-, HCV-, or TGF-ß1-induced liver fibrogenesis. HBV/HCV coinfection and HBx, HBV preS2, HCV Core, and HCV NS2/3 overexpression increased TGF-ß1 mRNA levels in sodium taurocholate cotransporting polypeptide-Huh7.5.1 cells compared with controls. HBV/HCV coinfection further enhanced profibrogenic gene expression relative to HBV or HCV monoinfection. Coculture of HBV and HCV monoinfected or HBV/HCV coinfected hepatocytes with LX2 cells significantly increased profibrotic gene expression and LX2 cell invasion and migration. OCT4 and Nanog guide RNA independently suppressed HBV-, HCV-, HBV/HCV-, and TGF-ß1-induced α-SMA, TIMP-1, and Col1A1 expression and reduced Huh7.5.1, LX2, primary hepatocyte, and primary human HSC migratory capacity. OCT4/Nanog protein expression also correlated positively with fibrosis stage in liver biopsies from patients with chronic HBV or HCV infection. In conclusion, HBV and HCV independently and cooperatively promote liver fibrogenesis through a TGF-ß1-induced OCT4/Nanog-dependent pathway.

A Deep Ravine Rather Than a Shallow Gap: Many More Bridges Needed to Improve Care of Chronic Hepatitis B in the United States.

ABSTRACT: In the United States, improved screening of those who are at highest risk of chronic hepatitis B (CHB) has been a major focus of public health efforts, as has facilitating access to care for those with chronic infection. Despite this, data suggest that less than half of those at risk are tested, and another minority of those who harbor chronic infection receive longitudinal care for the disease. In this study by Tran et al., the authors find that even among those being treated for CHB, a vast minority receive basic testing and screening for staging and complications of CHB.

Fatty Acids Activate the Transcriptional Coactivator YAP1 to Promote Liver Fibrosis via p38 Mitogen-Activated Protein Kinase.

BACKGROUND & AIMS: Patients with simple steatosis (SS) and nonalcoholic steatohepatitis can develop progressive liver fibrosis, which is associated with liver-related mortality. The mechanisms contributing to liver fibrosis development in SS, however, are poorly understood. SS is characterized by hepatocellular free fatty acid (FFA) accumulation without lobular inflammation seen in nonalcoholic steatohepatitis. Because the Hippo signaling transcriptional coactivator YAP1 (YAP) has previously been linked with nonalcoholic fatty liver disease (NAFLD)-related fibrosis, we sought to explore how hepatocyte FFAs activate a YAP-mediated profibrogenic program. METHODS: We analyzed RNA sequencing data from a GEO DataSet (accession: GSE162694) consisting of 143 patients with NAFLD. We also performed immunohistochemical, immunofluorescence, immunoblot, and quantitative reverse-transcription polymerase chain reaction analyses (qRT-PCR) in liver specimens from NAFLD subjects, from a murine dietary NAFLD model, and in FFA-treated hepatic spheroids and hepatocytes. RESULTS: YAP-target gene expression correlated with increasing fibrosis stage in NAFLD patients and was associated with fibrosis in mice fed a NAFLD-inducing diet. Hepatocyte-specific YAP deletion in the murine NAFLD model attenuated diet-induced fibrosis, suggesting a causative role of YAP in NAFLD-related fibrosis. Likewise, in hepatic spheroids composed of Huh7 hepatoma cells and primary human hepatic stellate cells, Huh7 YAP silencing reduced FFA-induced fibrogenic gene expression. Notably, inhibition of p38 mitogen-activated protein kinase could block YAP activation in FFA-treated Huh7 cells. CONCLUSIONS: These studies provide further evidence for the pathological role of YAP in NAFLD-associated fibrosis and that YAP activation in NAFLD may be driven by FFA-induced p38 MAPK activation.

Microrna-130a Downregulates HCV Replication through an atg5-Dependent Autophagy Pathway.

We previously identified that miR-130a downregulates HCV replication through two independent pathways: restoration of host immune responses and regulation of pyruvate metabolism. In this study, we further sought to explore host antiviral target genes regulated by miR-130a. We performed a RT² Profiler™ PCR array to identify the host antiviral genes regulated by miR-130a. The putative binding sites between miR-130a and its downregulated genes were predicted by miRanda. miR-130a and predicted target genes were over-expressed or knocked down by siRNA or CRISPR/Cas9 gRNA. Selected gene mRNAs and their proteins, together with HCV replication in JFH1 HCV-infected Huh7.5.1 cells were monitored by qRT-PCR and Western blot. We identified 32 genes that were significantly differentially expressed more than 1.5-fold following miR-130a overexpression, 28 of which were upregulated and 4 downregulated. We found that ATG5, a target gene for miR-130a, significantly upregulated HCV replication and downregulated interferon stimulated gene expression. miR-130a downregulated ATG5 expression and its conjugation complex with ATG12. ATG5 and ATG5-ATG12 complex affected interferon stimulated gene (ISG) such as MX1 and OAS3 expression and subsequently HCV replication. We concluded that miR-130a regulates host antiviral response and HCV replication through targeting ATG5 via the ATG5-dependent autophagy pathway.

A Long Noncoding RNA Regulates Hepatitis C Virus Infection Through Interferon Alpha-Inducible Protein 6.

Long noncoding RNAs (lncRNAs) play a critical role in the regulation of many important cellular processes. However, the mechanisms by which lncRNAs regulate viral infection and host immune responses are not well understood. We sought to explore lncRNA regulation of hepatitis C virus (HCV) infection and interferon response. We performed RNA sequencing (RNAseq) in Huh7.5.1 cells with or without interferon alpha (IFNα) treatment. Clustered regularly interspaced short palindromic repeats/Cas9 guide RNA (gRNA) was used to knock out selected genes. The promoter clones were constructed, and the activity of related interferon-stimulated genes (ISGs) were detected by the secrete-pair dual luminescence assay. We constructed the full-length and four deletion mutants of an interferon-induced lncRNA RP11-288L9.4 (lncRNA-IFI6) based on predicted secondary structure. Selected gene mRNAs and their proteins, together with HCV infection, in Huh7.5.1 cells and primary human hepatocytes (PHHs) were monitored by quantitative real-time PCR (qRT-PCR) and western blot. We obtained 7,901 lncRNAs from RNAseq. A total of 1,062 host-encoded lncRNAs were significantly differentially regulated by IFNα treatment. We found that lncRNA-IFI6 gRNA significantly inhibited HCV infection compared with negative gRNA control. The expression of the antiviral ISG IFI6 was significantly increased following lncRNA-IFI6 gRNA editing compared with negative gRNA control in Japanese fulminant hepatitis 1 (JFH1)-infected Huh7.5.1 cells and PHHs. We observed that lncRNA-IFI6 regulation of HCV was independent of Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling. lncRNA-IFI6 negatively regulated IFI6 promoter function through histone modification. Overexpression of the truncated spatial domain or full-length lncRNA-IFI6 inhibited IFI6 expression and increased HCV replication. Conclusion: A lncRNA, lncRNA-IFI6, regulates antiviral innate immunity in the JFH1 HCV infection model. lncRNA-IFI6 regulates HCV infection independently of the JAK-STAT pathway. lncRNA-IFI6 exerts its regulatory function via promoter activation and histone modification of IFI6 through its spatial domain.

Macrophage Activation Marker Soluble CD163 Is a Dynamic Marker of Liver Fibrogenesis in Human Immunodeficiency Virus/Hepatitis C Virus Coinfection.

Background: Coinfection with human immunodeficiency virus (HIV) accelerates hepatitis C virus (HCV)-related liver fibrosis. Macrophages are triggered during both viral infections and are critical in liver inflammation/fibrogenesis. Liver fibrosis strongly associates with serum soluble CD163 (sCD163, a macrophage activation marker); comprehensive evaluation in HIV/HCV coinfection is lacking. Methods: We retrospectively analyzed sCD163 (enzyme-linked immunosorbent assay) and hepatic CD163 (immunofluorescent CD163/CD68 costaining) in patients infected with HIV/HCV, HCV, or HIV, pre- and post-antiviral therapy. Results: sCD163 was significantly higher in HIV/HCV compared to either monoinfection, and decreased following successful antiviral therapy, although did not fully normalize. In HIV/HCV, sCD163 was associated with necroinflammation, Ishak fibrosis scores, and noninvasive fibrosis scores. We observed a novel trend whereby sCD163 levels progressively increase with increasing Ishak fibrosis score, peaking at stage 4, above which levels plateaued. Periportal CD163+ macrophage frequency was also higher with increasing fibrosis score. When stratified by fibrosis stage, sCD163 levels were higher in HIV/HCV than HCV but only in individuals with mild to moderate fibrosis. Conclusions: In HIV/HCV, increasing sCD163 levels accompanied periportal CD163+ macrophage enrichment in mild to moderate fibrosis, but not in established cirrhosis, suggesting that sCD163 is a dynamic biomarker of fibrogenesis rather than accumulated fibrosis. Our findings implicate HIV-related macrophage activation in accelerated fibrosis progression in HIV/HCV coinfection.

MicroRNA 130a Regulates both Hepatitis C Virus and Hepatitis B Virus Replication through a Central Metabolic Pathway.

Hepatitis C virus (HCV) infection has been shown to regulate microRNA 130a (miR-130a) in patient biopsy specimens and in cultured cells. We sought to identify miR-130a target genes and to explore the mechanisms by which miR-130a regulates HCV and hepatitis B virus (HBV) replication. We used bioinformatics software, including miRanda, TargetScan, PITA, and RNAhybrid, to predict potential miR-130a target genes. miR-130a and its target genes were overexpressed or were knocked down by use of small interfering RNA (siRNA) or clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 guide RNA (gRNA). Selected gene mRNAs and their proteins, together with HCV replication in OR6 cells, HCV JFH1-infected Huh7.5.1 cells, and HCV JFH1-infected primary human hepatocytes (PHHs) and HBV replication in HepAD38 cells, HBV-infected NTCP-Huh7.5.1 cells, and HBV-infected PHHs, were measured by quantitative reverse transcription-PCR (qRT-PCR) and Western blotting, respectively. We selected 116 predicted target genes whose expression was related to viral pathogenesis or immunity for qPCR validation. Of these, the gene encoding pyruvate kinase in liver and red blood cell (PKLR) was confirmed to be regulated by miR-130a overexpression. miR-130a overexpression (via a mimic) knocked down PKLR mRNA and protein levels. A miR-130a inhibitor and gRNA increased PKLR expression, HCV replication, and HBV replication, while miR-130a gRNA and PKLR overexpression increased HCV and HBV replication. Supplemental pyruvate increased HCV and HBV replication and rescued the inhibition of HCV and HBV replication by the miR-130a mimic and PKLR knockdown. We concluded that miR-130a regulates HCV and HBV replication through its targeting of PKLR and subsequent pyruvate production. Our data provide novel insights into key metabolic enzymatic pathway steps regulated by miR-130a, including the steps involving PKLR and pyruvate, which are subverted by HCV and HBV replication.IMPORTANCE We identified that miR-130a regulates the target gene PKLR and its subsequent effect on pyruvate production. Pyruvate is a key intermediate in several metabolic pathways, and we identified that pyruvate plays a key role in regulation of HCV and HBV replication. This previously unrecognized, miRNA-regulated antiviral mechanism has implications for the development of host-directed strategies to interrupt the viral life cycle and prevent establishment of persistent infection for HCV, HBV, and potentially other viral infections.

Vascular Injury Characterizes Doxycycline-induced Upper Gastrointestinal Tract Mucosal Injury.

Doxycycline is an oral tetracycline antibiotic that has been associated with upper gastrointestinal (GI) mucosal injury. Recently, characteristic vascular degeneration has been reported in the stomach and duodenum in patients with doxycycline-induced injury. Fourteen patients who underwent upper GI endoscopy for nonspecific symptoms and were found to have doxycycline-induced gastric and esophageal injury are described. Most patients showed characteristic vascular injury. A control group of gastric erosions and esophageal ulcers showed no cases with the characteristic vascular changes. Clinical, endoscopic, and pathologic features of doxycycline-induced upper GI tract injury are reviewed, with an emphasis on vascular injury.

Apolipoprotein B100 is required for hepatitis C infectivity and Mipomersen inhibits hepatitis C.

AIM: To characterize the role of apolipoprotein B100 (apoB100) in hepatitis C viral (HCV) infection. METHODS: In this study, we utilize a gene editing tool, transcription activator-like effector nucleases (TALENs), to generate human hepatoma cells with a stable genetic deletion of APOB to assess of apoB in HCV. Using infectious cell culture-competent HCV, viral pseudoparticles, replicon models, and lipidomic analysis we determined the contribution of apoB to each step of the viral lifecycle. We further studied the effect of mipomersen, an FDA-approved antisense inhibitor of apoB100, on HCV using in vitro cell-culture competent HCV and determined its impact on viral infectivity with the TCID50 method. RESULTS: We found that apoB100 is indispensable for HCV infection. Using the JFH-1 fully infectious cell-culture competent virus in Huh 7 hepatoma cells with TALEN-mediated gene deletion of apoB (APOB KO), we found a significant reduction in HCV RNA and protein levels following infection. Pseudoparticle and replicon models demonstrated that apoB did not play a role in HCV entry or replication. However, the virus produced by APOB KO cells had significantly diminished infectivity as measured by the TCID-50 method compared to wild-type virus. Lipidomic analysis demonstrated that these virions have a fundamentally altered lipidome, with complete depletion of cholesterol esters. We further demonstrate that inhibition of apoB using mipomersen, an FDA-approved anti-sense oligonucleotide, results in a potent anti-HCV effect and significantly reduces the infectivity of the virus. CONCLUSION: ApoB is required for the generation of fully infectious HCV virions, and inhibition of apoB with mipomersen blocks HCV. Targeting lipid metabolic pathways to impair viral infectivity represents a novel host targeted strategy to inhibit HCV.

Exposure to human immunodeficiency virus/hepatitis C virus in hepatic and stellate cell lines reveals cooperative profibrotic transcriptional activation between viruses and cell types.

Human immunodeficiency virus (HIV)/hepatitis C virus (HCV) coinfection accelerates progressive liver fibrosis; however, the mechanisms remain poorly understood. HCV and HIV independently induce profibrogenic markers transforming growth factor beta-1 (TGFß1) (mediated by reactive oxygen species [ROS]) and nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) in hepatocytes and hepatic stellate cells in monoculture; however, they do not account for cellular crosstalk that naturally occurs. We created an in vitro coculture model and investigated the contributions of HIV and HCV to hepatic fibrogenesis. Green fluorescent protein reporter cell lines driven by functional ROS (antioxidant response elements), NFκB, and mothers against decapentaplegic homolog 3 (SMAD3) promoters were created in Huh7.5.1 and LX2 cells, using a transwell to generate cocultures. Reporter cell lines were exposed to HIV, HCV, or HIV/HCV. Activation of the 3 pathways was measured and compared according to infection status. Extracellular matrix products (collagen type 1 alpha 1 (CoL1A1) and tissue inhibitor of metalloproteinase 1 (TIMP1)) were also measured. Both HCV and HIV independently activated TGFß1 signaling through ROS (antioxidant response elements), NFκB, and SMAD3 in both cell lines in coculture. Activation of these profibrotic pathways was additive following HIV/HCV coexposure. This was confirmed when examining CoL1A1 and TIMP1, where messenger RNA and protein levels were significantly higher in LX2 cells in coculture following HIV/HCV coexposure compared with either virus alone. In addition, expression of these profibrotic genes was significantly higher in the coculture model compared to either cell type in monoculture, suggesting an interaction and feedback mechanism between Huh7.5.1 and LX2 cells. CONCLUSION: HIV accentuates an HCV-driven profibrogenic program in hepatocyte and hepatic stellate cell lines through ROS, NFκB, and TGFß1 up-regulation; coculture of hepatocyte and hepatic stellate cell lines significantly increased expression of CoL1A1 and TIMP1; and our novel coculture reporter cell model represents an efficient and more authentic system for studying transcriptional fibrosis responses and may provide important insights into hepatic fibrosis. (Hepatology 2016;64:1951-1968).

IQGAP2 is a novel interferon-alpha antiviral effector gene acting non-conventionally through the NF-κB pathway.

BACKGROUND & AIMS: Type I interferons (IFN) provide the first line of defense against invading pathogens but its mechanism of action is still not well understood. Using unbiased genome-wide siRNA screens, we recently identified IQ-motif containing GTPase activating protein 2 (IQGAP2), a tumor suppressor predominantly expressed in the liver, as a novel gene putatively required for IFN antiviral response against hepatitis C virus (HCV) infection. Here we sought to characterize IQGAP2 role in IFN response. METHODS: We used transient small interfering RNA knockdown strategy in hepatic cell lines highly permissive to JFH1 strain of HCV infection. RESULTS: We found that IQGAP2 acts downstream of IFN binding to its receptor, and independently of the JAK-STAT pathway, by physically interacting with RelA (also known as p65), a subunit of the NF-κB transcription factor. Interestingly, our data reveal a mechanism distinct from the well-characterized role of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in IFN production. Indeed, IFN alone was sufficient to stimulate NF-κB-dependent transcription in the absence of viral infection. Finally, both IQGAP2 and RelA were required for the induction by IFN of a subset of IFN-stimulated genes (ISG) with known antiviral properties. CONCLUSIONS: Our data identify a novel function for IQGAP2 in IFN antiviral response in hepatoma cells. We demonstrate the involvement of IQGAP2 in regulating ISG induction by IFN in an NF-κB-dependent manner. The IQGAP2 pathway may provide new targets for antiviral strategies in the liver, and may have a wider therapeutic implication in other disease pathogeneses driven by NF-κB activation. LAY SUMMARY: In this study, we identify a novel mechanism of action of interferon involving the IQGAP2 protein and the NF-κB pathway that is ultimately protective against hepatitis C virus infection. This newly identified pathway functions independently of the well-known STAT pathway and may therefore provide new targets for antiviral strategies in the liver.