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Background The inhibitor telaprevir (VX-950) of the hepatitis C virus (HCV) protease NS3-4A has been tested in a recent phase 1b clinical trial in patients infected with HCV genotype 1. This trial revealed residue mutations that confer varying degrees of drug resistance. In particular, two protease positions with the mutations V36A/G/L/M and T54A/S were associated with low to medium levels of drug resistance during viral breakthrough, together with only an intermediate reduction of viral replication fitness. These mutations are located in the protein interior and far away from the ligand binding pocket. Results Based on the available experimental structures of NS3-4A, we analyze the binding mode of different ligands. We also investigate the binding mode of VX-950 by protein-ligand docking. A network of non-covalent interactions between amino acids of the protease structure and the interacting ligands is analyzed to discover possible mechanisms of drug resistance. We describe the potential impact of V36 and T54 mutants on the side chain and backbone conformations and on the non-covalent residue interactions. We propose possible explanations for their effects on the antiviral efficacy of drugs and viral fitness. Molecular dynamics simulations of T54A/S mutants and rotamer analysis of V36A/G/L/M side chains support our interpretations. Experimental data using an HCV V36G replicon assay corroborate our findings. Conclusion T54 mutants are expected to interfere with the catalytic triad and with the ligand binding site of the protease. Thus, the T54 mutants are assumed to affect the viral replication efficacy to a larger degree than V36 mutants. Mutations at V36 and/or T54 result in impaired interaction of the protease residues with the VX-950 cyclopropyl group, which explains the development of viral breakthrough variants.
The macrophage-inducible C-type lectin (mincle) is part of the innate immune system and acts as a pattern recognition receptor for pathogen-associated molecular patterns (PAMPS) and damage-associated molecular patterns (DAMPs). Ligand binding induces mincle activation which consequently interacts with the signaling adapter Fc receptor, SYK, and NF-kappa-B. There is also evidence that mincle expressed on macrophages promotes intestinal barrier integrity. However, little is known about the role of mincle in hepatic fibrosis, especially in more advanced disease stages. Mincle expression was measured in human liver samples from cirrhotic patients and donors collected at liver transplantation and in patients undergoing bariatric surgery. Human results were confirmed in rodent models of cirrhosis and acute-on-chronic liver failure (ACLF). In these models, the role of mincle was investigated in liver samples as well as in peripheral blood monocytes (PBMC), tissues from the kidney, spleen, small intestine, and heart. Additionally, mincle activation was stimulated in experimental non-alcoholic steatohepatitis (NASH) by treatment with mincle agonist trehalose-6,6-dibehenate (TDB). In human NASH, mincle is upregulated with increased collagen production. In ApoE deficient mice fed high-fat western diet (NASH model), mincle activation significantly increases hepatic collagen production. In human cirrhosis, mincle expression is also significantly upregulated. Furthermore, mincle expression is associated with the stage of chronic liver disease. This could be confirmed in rat models of cirrhosis and ACLF. ACLF was induced by LPS injection in cirrhotic rats. While mincle expression and downstream signaling via FC receptor gamma, SYK, and NF-kappa-B are upregulated in the liver, they are downregulated in PBMCs of these rats. Although mincle expressed on macrophages might be beneficial for intestinal barrier integrity, it seems to contribute to inflammation and fibrosis once the intestinal barrier becomes leaky in advanced stages of chronic liver disease.
Background: Advanced liver diseases are associated with profound alterations of the coagulation system increasing the risk not only of bleeding, but also of thromboembolic complications. A recent milestone study has shown that prophylactic anticoagulation in liver cirrhosis patients results in a reduced frequency of hepatic decompensation. Yet, INR measurement, one of the most widely applied tests to assess liver function, only inaccurately predicts the risk of hepatic decompensation related to alterations of the coagulation system. To assess the relationship between selected coagulation factors / natural anticoagulants with INR, MELD score, and hepatic decompensation, we performed the present pilot study. A total number of 92 patients with various stages of liver cirrhosis were included and prospectively followed for at least 6 months. We found that important natural anticoagulants, namely antithrombin and protein C, as well as factor XI (which may also serve as an anticoagulant) decreased earlier and by a larger magnitude than one would expect from classical coagulation test results. The correlation between these factors and INR was only moderate. Importantly, reduced plasma activities of natural anticoagulants but not INR or MELD score were independent predictors of hepatic encephalopathy (P = 0.013 and 0.003 for antithrombin and protein C, respectively).
Conclusion: In patients with liver cirrhosis plasma activities of several natural anticoagulants are earlier and stronger affected than routine coagulation tests. Reduced activities of natural anticoagulants may be predictive for the development of hepatic encephalopathy.
Hepatitis C virus (HCV) infection is associated with alterations in host lipid and insulin signaling cascades, which are partially explained by a dependence of the HCV life cycle on key molecules in these metabolic pathways. Yet, little is known on the role in the HCV life cycle of glycogen synthase kinase 3 (GSK3), one of the most important kinases in cellular metabolism. Therefore, the impact of GSK3 on the HCV life cycle was assessed in human hepatoma cell lines harboring subgenomic genotype 1b and 2a replicons or producing cell culture-derived HCV genotype 2a by exposure to synthetic GSK3 inhibitors, GSK3 gene silencing, overexpression of GSK3 constructs and immunofluorescence analyses. In addition, the role of GSK3 in hepatitis E virus (HEV) replication was investigated to assess virus specificity of the observed findings. We found that both inhibition of GSK3 function by synthetic inhibitors as well as silencing of GSK3β gene expression resulted in a decrease of HCV replication and infectious particle production, whereas silencing of the GSK3α isoform had no relevant effect on the HCV life cycle. Conversely, overexpression of GSK3β resulted in enhanced HCV replication. In contrast, GSK3β had no effect on replication of subgenomic HEV replicon. The pro-viral effect of GSK3β on HCV replication was mediated by supporting expression of microRNA-122 (miR-122), a micro-RNA which is mandatory for wild-type HCV replication, as GSK3 inhibitors suppressed miR-122 levels and as inhibitors of GSK3 had no antiviral effect on a miR-122-independent HCV mutant. In conclusion, we have identified GSK3β is a novel host factor supporting HCV replication by maintaining high levels of hepatic miR-122 expression.
Ongoing liver inflammation in patients with chronic hepatitis C and sustained virological response
(2017)
Background: Novel direct-acting antiviral DAA combination therapies tremendously improved sustained virologic response (SVR) rates in patients with chronic HCV infection. SVR is typically accompanied by normalization of liver enzymes, however, hepatic inflammation, i.e. persistently elevated aminotransferase levels may persist despite HCV eradication. Aim: To investigate prevalence and risk factors for ongoing hepatic inflammation after SVR in two large patient cohorts.
Methods: This post-hoc analysis was based on prospectively collected demographic and clinical data from 834 patients with SVR after HCV treatment with either PegIFN- or DAA-based treatment regimens from the PRAMA trial (n = 341) or patients treated at our outpatient clinic (n = 493).
Results: We observed an unexpected high prevalence of post-SVR inflammation, including patients who received novel IFN-free DAA-based therapies. Up to 10% of patients had ongoing elevation of aminotransferase levels and another 25% showed aminotransferase activity above the so-called healthy range. Several baseline factors were independently associated with post-SVR aminotransferase elevation. Among those, particularly male gender, advanced liver disease and markers for liver steatosis were strongly predictive for persistent ALT elevation. The use of IFN-based antiviral treatment was independently correlated with post-SVR inflammation, further supporting the overall benefit of IFN-free combination regimens.
Conclusion: This is the first comprehensive study on a large patient cohort investigating the prevalence and risk factors for ongoing liver inflammation after eradication of HCV. Our data show a high proportion of patients with ongoing hepatic inflammation despite HCV eradication with potential implications for the management of approximately one third of all patients upon SVR.
Background: Vitamin D is required to maintain the integrity of the intestinal barrier and inhibits inflammatory signaling pathways.
Objective: Vitamin D deficiency might be involved in cirrhosis-associated systemic inflammation and risk of hepatic decompensation in patients with liver cirrhosis.
Methods: Outpatients of the Hepatology Unit of the University Hospital Frankfurt with advanced liver fibrosis and cirrhosis were prospectively enrolled. 25-hydroxyvitamin D (25(OH)D3) serum concentrations were quantified and associated with markers of systemic inflammation / intestinal bacterial translocation and hepatic decompensation.
Results: A total of 338 patients with advanced liver fibrosis or cirrhosis were included. Of those, 51 patients (15%) were hospitalized due to hepatic decompensation during follow-up. Overall, 72 patients (21%) had severe vitamin D deficiency. However, patients receiving vitamin D supplements had significantly higher 25(OH)D3 serum levels compared to patients without supplements (37 ng/mL vs. 16 ng/ml, P<0.0001). Uni- and multivariate analyses revealed an independent association of severe vitamin D deficiency with the risk of hepatic decompensation during follow-up (multivariate P = 0.012; OR = 3.25, 95% CI = 1.30–8.2), together with MELD score, low hemoglobin concentration, low coffee consumption, and presence of diabetes. Of note, serum levels of C-reactive protein, IL-6 and soluble CD14 were significantly higher in patients with versus without severe vitamin D deficiency, and serum levels of soluble CD14 levels declined in patients with de novo supplementation of vitamin D (median 2.15 vs. 1.87 ng/mL, P = 0.002).
Conclusions: In this prospective cohort study, baseline vitamin D levels were inversely associated with liver-cirrhosis related systemic inflammation and the risk of hepatic decompensation.
Interleukin-7 (IL-7) is an important cytokine with pivotal pro-survival functions in the adaptive immune system. However, the role of IL-7 in innate immunity is not fully understood. In the present study, the impact of hepatic IL-7 on innate immune cells was assessed by functional experiments as well as in patients with different stages of liver cirrhosis or acute-on-chronic liver failure (ACLF). Human hepatocytes and liver sinusoidal endothelial cells secreted IL-7 in response to stimulation with interferons (IFNs) of type I and II, yet not type III. De novo translation of interferon-response factor-1 (IRF-1) restricted IL-7 production to stimulation with type I and II IFNs. LPS-primed human macrophages were identified as innate immune target cells responding to IL-7 signaling by inactivation of Glycogen synthase kinase-3 (GSK3). IL-7-mediated GSK3 inactivation augmented LPS-induced secretion of pro-inflammatory cytokines and blunted LPS tolerance of macrophages. The IFN-IRF-1-IL-7 axis was present in liver cirrhosis patients. However, liver cirrhosis patients with or without ACLF had significantly lower concentrations of IL-7 in serum compared to healthy controls, which might contribute to LPS-tolerance in these patients. In conclusion, we propose the presence of an inflammatory cascade where IFNs of type I/II induce hepatocellular IL-7 in an IRF-1-restriced way. Beyond its role in adaptive immune responses, IL-7 appears to augment the response of macrophages to LPS and to ameliorate LPS tolerance, which may improve innate immune responses against invading pathogens.
Background: While systemic inflammation is recognized as playing a central role in the pathogenesis of organ failures in patients with liver cirrhosis, less is known about its relevance in the development of classical hepatic decompensation. Aim: To characterize the relationship between systemic inflammation, hemodynamics, and anemia with decompensation of liver cirrhosis. Methods: This is a post-hoc analysis of a cohort study of outpatients with advanced liver fibrosis or cirrhosis. Results: Analysis included 338 patients of whom 51 patients (15%) were hospitalized due to decompensation of liver cirrhosis during a median follow-up time of six months. In univariate analysis, active alcoholism (p = 0.002), model of end-stage liver disease (MELD) score (p = 0.00002), serum IL-6 concentration (p = 0.006), heart rate (p = 0.03), low arterial blood pressure (p < 0.05), maximal portal venous flow (p = 0.008), and low hemoglobin concentration (p < 0.00001) were associated with hospitalization during follow-up. Multivariate analysis revealed an independent association of low hemoglobin (OR = 0.62, 95% CI = 0.51–0.78, p = 0.001) and serum IL-6 concentration (OR = 1.02, 95% CI = 1.01–1.04, p = 0.03)—but not of hemodynamic parameters—with hepatic decompensation. An inverse correlation between hemoglobin concentration and portal venous flow (R = −0.362, p < 0.0001) was detected for the non-hospitalized patients. Accuracy of baseline hemoglobin levels for predicting hospitalization (AUC = 0.84, p < 0.000001) was high. Conclusion: Anemia and systemic inflammation, rather than arterial circulatory dysfunction, are strong and independent predictors of hepatic decompensation in outpatients with liver cirrhosis.
Extracellular vesicles (EVs) are increasingly recognized as important mediators of intercellular communication. In this study, we aimed to further characterize the role of macrophage-derived EVs in immune responses against hepatitis C virus (HCV) and the potential of polyunsaturated fatty acids (PUFAs) to modulate this modality of innate immunity. To this end, EVs were isolated from interferon-stimulated macrophage cultures or from serum of patients with acute or chronic hepatitis C. EVs were characterized by electron microscopy, flow cytometry, RNA-sequencing, and Western blot analysis. The effect of EVs on replication of HCV was assessed in coculture models. Functional analyses were performed to assess the impact of PUFAs on EV-mediated antiviral immunity. We found that macrophages secreted various cytokines shortly after stimulation with type I and II IFN, which orchestrated a fast but short-lasting antiviral state. This rapid innate immune answer was followed by the production of macrophage-derived EVs, which induced a late, but long-lasting inhibitory effect on HCV replication. Of note, exposure of macrophages to PUFAs, which are important regulators of immune responses, dampened EV-mediated antiviral immune responses. Finally, EVs from patients with hepatitis C exhibited long-lasting antiviral activities during IFN therapy as well. The antiviral effect of EVs from Caucasian and Japanese patients differed, which may be explained by different nutritional uptake of PUFAs. In conclusion, our data indicate that macrophage-derived EVs mediate long-lasting inhibitory effects on HCV replication, which may bridge the time until efficient adaptive immune responses are established, and which can be blunted by PUFAs.
Background: Liver cirrhosis is associated with profound immunodysfunction, i.e. a parallel presence of chronic systemic inflammation and immunosuppression, which can result in acute-on-chronic liver failure (ACLF). Omega-3 fatty acids are precursors of pro-resolving mediators and support the resolution of inflammation.
Objective: The aim of this study was to determine plasma levels of omega-3 fatty acids in patients with liver cirrhosis and ACLF.
Methods: Patients with liver cirrhosis with and without ACLF were enrolled in a prospective cohort study and analyzed post-hoc for the present sub-study. Clinical data and biomaterials were collected at baseline and at day 7, 28 and after 3 months of follow-up. Plasma concentrations of arachidonic acid (ARA) and docosahexaenoic acid (DHA), which represent key omega-6 and -3 fatty acids, respectively, were quantified and associated with markers of systemic inflammation and severity of liver cirrhosis.
Results: A total of 117 patients were included in the present analyses. Of those, 26 (22.2%), 51 (43.6%) and 40 (34.2%) patients had compensated or decompensated liver cirrhosis, and ACLF. Plasma levels of ARA and DHA were similar in patients with compensated cirrhosis, decompensated cirrhosis, and ACLF. Furthermore, no significant association between plasma ARA or DHA and C-reactive protein or peripheral blood leukocytes were observed (P>0.05).
Conclusion: In our study plasma levels of key omega-3 and omega-6 fatty acid are neither associated with the severity of liver cirrhosis nor with liver-cirrhosis-associated systemic inflammation.
