Search

The interferon-stimulated gene 15 ( ISG15) plays an important role in the pathogenesis of hepatitis C virus ( HCV) infection. ISG15-regulated proteins have previously been identified that putatively affect this proviral interaction. The present observational study aimed to elucidate the relation between ISG15 and these host factors during HCV infection. Transcriptomic and proteomic analyses were performed using liver samples of HCV-infected ( n = 54) and uninfected ( n = 10) or HBV-infected controls ( n = 23). Primary human hepatocytes ( PHH) were treated with Toll-like receptor ligands, interferons and kinase inhibitors. Expression of ISG15 and proteasome subunit alpha type-6 ( PSMA6) was suppressed in subgenomic HCV replicon cell lines using specific si RNAs. Comparison of hepatic expression patterns revealed significantly increased signals for ISG15, IFIT1, HNRNPK and PSMA6 on the protein level as well as ISG15, IFIT1 and PSMA6 on the mRNA level in HCV-infected patients. In contrast to interferon-stimulated genes, PSMA6 expression occurred independent of HCV load and genotype. In PHH, the expression of ISG15 and PSMA6 was distinctly induced by poly(I:C), depending on IRF3 activation or PI3K/ AKT signalling, respectively. Suppression of PSMA6 in HCV replicon cells led to significant induction of ISG15 expression, thus combined knock-down of both genes abrogated the antiviral effect induced by the separate suppression of ISG15. These data indicate that hepatic expression of PSMA6, which is upregulated during viral hepatitis, likely depends on TLR3 activation. PSMA6 affects the expression of immunoregulatory ISG15, a proviral factor in the pathogenesis of HCV infection. Therefore, the proteasome might be involved in the enigmatic interaction between ISG15 and HCV. [ABSTRACT FROM AUTHOR]

It has been recently shown that Toll-like receptor ( TLR) signalling in murine nonparenchymal liver cells ( NPCs) is suppressed in the presence of Hepatitis B virus surface antigen ( HBs Ag). It is not clear, however, whether this is also relevant for the adaptive immune responses and how this effect is mediated. Peripheral blood mononuclear cells ( PBMCs) from Hepatitis B virus ( HBV) patients and controls were stimulated by TLR ligands in the absence or presence of autologous serum. Interestingly, TLR-mediated cytokine expression ( Interleukin-6 and -10) as well as TLR3-induced interferon ( IFN) expression in PBMCs of HBV patients was significantly higher than in the healthy volunteers, showing a negative correlation with the levels of HBs Ag. In addition, TLR3-mediated IFN-γ production was inhibited in the presence of HBV-containing serum. To mechanistically analyse this observation, murine Kupffer cells ( KCs) and sinusoidal endothelial cells ( LSECs) were stimulated with TLR3 ligands in the presence or absence of HBs Ag. Mixed lymphocyte reactions were performed to study T-cell activation induced by TLR-stimulated NPCs. Gene expression of cytokines and TLR3 was analysed by quantitative rt- PCR, and activation of transcription factors was assessed by Western blot or reporter gene assays. TLR-induced expression of interferon γ, interferon sensitive genes and proinflammatory cytokines in murine KCs and LSECs was efficiently suppressed in the presence of HBs Ag, whereas the expression of anti-inflammatory cytokines was enhanced. Activation of NFκ B, IRF-3 and MAPKs in these liver cells was potently suppressed by HBs Ag. T-cell activation mediated through TLR3-stimulated KCs or LSECs was suppressed by HBs Ag which could be reverted by anti- IL-10 antibodies. These findings may, at least in part, explain how HBV evades innate and adaptive immune responses to maintain a persistent infection. [ABSTRACT FROM AUTHOR]

Chronic hepatitis C infection is associated with increased expression of interferon-sensitive genes ( ISGs) in the liver, which is, paradoxically, correlated with the nonresponse to interferon ( IFN)-based therapies. In the present study PHHs were isolated from HCV-infected or uninfected patients and stimulated with the TLR1-9 ligands for 6-24 h. Expression of cytokines and ISGs was determined by ELISA and qRT- PCR. A comparative analysis was performed for TLR3 signalling, which was also correlated with single nucleotide polymorphisms ( SNPs) related to HCV pathogenesis. TLR-activated PHHs produced pro-inflammatory and anti-inflammatory cytokines, whereas IFNs were exclusively induced by TLR3 stimulation. Here, IL-29 and IL-28 A were significantly highly expressed than IFN-α and IFN-β. TLR3-induced IFN response was enhanced in hepatocytes isolated from patients with HCV infection. This hyper-responsiveness could be mimicked in naïve PHHs consistently stimulated with low dose of poly I: C, but not Guardiquimod. The higher responsiveness in PHH isolated from HCV-infected patients could be partially explained by higher frequencies of unfavourable SNP alleles of different SNPs associated with HCV progression and treatment outcome. These data suggest that durable activation of TLR3 but not TLR7, by low doses of viral replicative intermediates, increases the sensitivity to viral invasion. These findings shed new light on the relevance of TLR3 in the pathogenesis of HCV and may provide a possible explanation for the increased ISG expression during chronic HCV infection, the so-called IFN paradox. [ABSTRACT FROM AUTHOR]

The hepatitis C virus ( HCV) establishes persistent infections despite strong activation of the innate immune system through TLR3 and other sensors. Therefore, we analysed regulatory mechanisms of TLR3-induced immune responses in nonparenchymal liver cells ( NPCs). Effects of Interleukin-10 ( IL-10), transforming growth factor beta ( TGF-β) and immunoregulatory mi R-155 on poly I: C-activated murine ( C57 BL/6) Kupffer cells ( KC) and sinusoidal endothelial cells ( LSEC) were assessed in vitro. NPCs were assayed for inflammatory and antiviral cytokines and T-cell ( Balb/c)-activating factors. Gene expression of mi R-155, IL-10, TGF-β and interferon sensitive genes ( ISGs) in biopsies of patients with HCV was determined by qrt- PCR. TLR3-induced antiviral activity in murine NPCs was potently suppressed by IL-10 and TGF-β which correlated with decreased TLR3 expression and inhibition of NF-κ B and IRF-3 activation. T-cell activation, induced by TLR3-activated NPCs, was also suppressed by IL-10 and TGF-β, which was associated with a down-regulation of CD80 and CD86. Pretreatment with IL-10 or TGF-β suppressed TLR3-induced mi R-155 expression, which itself positively regulated poly I: C-mediated immune responses, thus counteracting IL-10 or TGF-β-induced immunosuppression. In addition, hepatic expression of mi R-155 was elevated in chronically infected patients with HCV, was associated with an IL-28 B SNP (rs12979860) and was inversely correlated with HCV serum load and ISG expression levels. As mi R-155 is a key regulator of anti-inflammatory mechanisms that control innate and adaptive hepatic immune responses during HCV infection, mi R-155 based therapies may represent a novel mechanism to control HCV in the future. [ABSTRACT FROM AUTHOR]

Background and Aims: Hepatitis B virus (HBV) infection is a major cause of hepatocellular carcinoma (HCC) development and progression. The aim of this study was to mechanistically investigate the involvement of Hippo signalling in HBV surface antigen (HBsAg)-dependent neoplastic transformation., Methods: Liver tissue and hepatocytes from HBsAg-transgenic mice were examined for the Hippo cascade and proliferative events. Functional experiments in mouse hepatoma cells included knockdown, overexpression, luciferase reporter assays and chromatin immunoprecipitation. Results were validated in HBV-related HCC biopsies., Results: Hepatic expression signatures in HBsAg-transgenic mice correlated with YAP responses, cell cycle control, DNA damage and spindle events. Polyploidy and aneuploidy occurred in HBsAg-transgenic hepatocytes. Suppression and inactivation of MST1/2 led to the loss of YAP phosphorylation and the induction of BMI1 expression in vivo and in vitro. Increased BMI1 directly mediated cell proliferation associated with decreased level of p16 INK4a , p19 ARF , p53 and Caspase 3 as well as increased Cyclin D1 and γ-H2AX expression. Chromatin immunoprecipitation and the analysis of mutated binding sites in dual-luciferase reporter assays confirmed that the YAP/TEAD4 transcription factor complex bound and activated the Bmi1 promoter. In chronic hepatitis B patients, paired liver biopsies of non-tumour and tumour tissue indicated a correlation between YAP expression and the abundance of BMI1. In a proof-of-concept, treatment of HBsAg-transgenic mice with YAP inhibitor verteporfin directly suppressed the BMI1-related cell cycle., Conclusion: HBV-associated proliferative HCC might be related to the HBsAg-YAP-BMI1 axis and offer a potential target for the development of new therapeutic approaches., (© 2023 The Authors. Liver International published by John Wiley & Sons Ltd.)

Background & Aims: During chronic hepatitis B virus (HBV) infection, suppressed functionality of natural killer (NK) cells might contribute to HBV persistence but the underlying mechanisms remain elusive. A peculiar feature of HBV is the secretion of large amount of hepatitis B surface antigen (HBsAg). However, the effect of HBsAg quantities on NK cells is unclear. The aim was to determine the effects of HBsAg quantities on NK cell functionality in patients with chronic hepatitis B (CHB)., Methods: Eighty CHB patients were included and categorized into four groups based on their HBsAg levels. As a control, 30 healthy donors were enrolled. NK cell frequency, phenotype and function were assessed using flow cytometry and correlated with HBsAg levels and liver enzymes., Results: Compared to the healthy controls, a reshaping of NK cell pool towards more CD56 bright NK cells was observed during CHB infection. Importantly, NK cells in patients with low HBsAg levels (<100 IU/mL) displayed an activated phenotype with increased expression of activation makers CD38, granzyme B and proliferation marker Ki-67 while presenting with defective functional responses (MIP-1β, CD107a) at the same time. Furthermore, NK cell activation was negatively correlated with patient HBsAg levels while NK function correlated with patient age., Conclusions: The differential regulation of NK cell phenotype and function suggests that activation of NK cells in patients with low serum HBsAg levels may contribute to HBV clearance., (© 2021 The Authors. Liver International published by John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The priming of T cells in the liver is widely accepted. Nonetheless, it is controversial whether immune activation in autoimmune hepatitis (AIH) occurs in the liver or in the spleen. To address this issue, we splenectomized mice and induced experimental murine AIH (emAIH) with an adenovirus (Ad)-expressing formiminotransferase cyclodeaminase (FTCD). Post-splenectomy, the experimental mice developed emAIH to a higher extent than the control mice. In addition, splenectomized mice harboured more intrahepatic B cells and a disproportionately small number of regulatory T cells (Tregs) within a reduced T cell population at the site of inflammation. These results imply that the spleen is not the site of AIH induction. In contrast, the spleen seems to have a protective function since the pathological score was more severe in splenectomized animals. These findings have important implications for the aetiology of AIH., (© 2019 The Authors. Liver International published by John Wiley & Sons Ltd.)