A Glässner

Natural killer p46High expression defines a natural killer cell subset that is potentially involved in control of hepatitis C virus replication and modulation of liver fibrosis

Natural killer (NK) cells play a role in the early control and natural course of hepatitis C virus (HCV) infection. NK cell function is regulated by a multitude of receptors, including activating NKp46 receptor. However, reports on NKp46 in hepatitis C are controversial. Therefore, we investigated the hepatic recruitment and function of NKp46(+) NK cells, considering differential surface expression of NKp46 resulting in NKp46High and NKp46Dim subsets. Intra‐ and extrahepatic NK‐cell subsets from HCV‐infected patients were characterized by flow cytometry. Cytotoxic activity and interferon‐gamma (IFN‐γ) secretion were studied using K‐562, P815, and primary hepatic stellate cells as targets. Anti‐HCV activity of NK‐cell subsets was studied using the replicon system. Density of NKp46 surface expression clearly segregated NKp46Dim and NKp46High subsets, which differed significantly with respect to the coexpression of maturation markers and NK‐cell receptors. More important, NKp46High NK cells showed a higher cytolytic activity and stronger IFN‐γ secretion than NKp46Dim NK cells. Accordingly, NKp46High NK cells efficiently blocked HCV replication in vitro. Blocking experiments confirmed an important role for the NKp46 receptor. Furthermore, we found an intrahepatic accumulation of NKp46High NK cells. Of note, high cytolytic activity of NKp46High NK cells was also confirmed in the intrahepatic NK‐cell population, and the frequency of intrahepatic NKp46High NK cells was inversely correlated with HCV‐RNA levels and fibrosis stage. Conclusions: NKp46High expression defines a specific NK‐cell subset that may be involved in both the suppression of HCV replication and HCV‐associated liver damage underpinning the role of NK cells in the immunopathogenesis of HCV. (HEPATOLOGY 2012)

NK cells from HCV-infected patients effectively induce apoptosis of activated primary human hepatic stellate cells in a TRAIL-, FasL- and NKG2D-dependent manner

In mouse models it has been shown that natural killer (NK) cells can attenuate liver fibrosis via killing of activated hepatic stellate cells (HSCs) in a NKG2D- and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-dependent manner. However, only little data exist regarding interactions of human NK cells with HSCs and their potential role in hepatitis C virus (HCV)-associated fibrogenesis. Therefore, purified NK cells from untreated HCV RNA(+) patients (n=33), interferon-α (IFN-α)-treated patients (n=17) and healthy controls (n=18) were coincubated with activated primary HSCs, and were tested for degranulation (CD107a expression) and secretion of IFN-γ and TNF-α, respectively. Induction of HSC apoptosis was analyzed using an active caspase-3 assay. We found that following coincubation with HSCs a significant increase in CD107a expression could be observed in both NK cells from HCV(+) patients and healthy controls, whereas only negligible secretion of IFN-γ and TNF-α could be detected. More importantly, NK cells from untreated HCV RNA(+) patients were significantly more effective in induction of HSC apoptosis (17.8±9.2%) than NK cells from healthy controls (6.2±2.1%; P<0.0001). Additionally, we observed an inverse correlation of liver fibrosis stage and the ability of NK cells to induce HSC apoptosis. Induction of HSC apoptosis was contact dependent and could partly be blocked by antibodies specific for TRAIL, NKG2D and FasL, respectively. It is noteworthy that NK cells from IFN-α-treated HCV(+) patients displayed the highest capability to kill HSCs (27.6±10.5%). Accordingly, pre-stimulation of NK cells with recombinant IFN-α significantly increased the ability of NK cells to induce cell death in primary HSCs and was dependent on upregulated expression of TRAIL. Here we demonstrate that NK cells from HCV-infected patients are highly efficient in inducing apoptosis of activated HSCs. Thus, NK cells may have an important anti-fibrotic role in chronic hepatitis C.

Impaired CD4 + T cell stimulation of NK cell anti-fibrotic activity may contribute to accelerated liver fibrosis progression in HIV/HCV patients

BACKGROUND & AIMS HIV/HCV co-infection is characterized by a faster progression to liver fibrosis compared to HCV mono-infection. Epidemiologic studies found an association between low CD4(+) T cell counts and advanced stages of liver fibrosis. However, the mechanisms underlying this association remain unclear. CD4(+) T cells critically modulate NK cell activity. Of note, NK cells have been shown to display anti-fibrotic activity via killing of activated hepatic stellate cells (HSC). Thus, we speculated that CD4(+) T cells might modulate fibrosis progression by interacting with NK cells. METHODS NK cells from HCV(+) (n=35), HIV(+)/HCV(+) (n=28), HIV(+) (n=8) patients, and healthy controls (n=30) were used in this study. NK cells were cultured in the presence or absence of supernatants from CD3/CD28-stimulated CD4(+) cells. Then, NK cells were co-incubated with activated HSC and studied for degranulation, IFN-γ secretion, and induction of HSC apoptosis. RESULTS Following incubation with CD4(+) T cell supernatants, NK cells displayed a significantly increased activity against primary HSC as compared to unstimulated NK cells. This effect was, at least in part, mediated via an IL-2 dependent upregulation of NKG2D expression. HCV/HIV co-infection was associated with an impaired IL-2 secretion of CD4(+) T cells resulting in an ineffective stimulation of anti-fibrotic NK cell function. CONCLUSIONS Here, we show that CD4(+) T cells are able to stimulate anti-fibrotic NK cell activity via IL-2 mediated upregulation of NKG2D. HIV-induced loss of CD4(+) T cells together with an impaired activity of CD4(+) T cells may contribute to accelerate progression of liver fibrosis observed in co-infection.

An effective interferon-gamma-mediated inhibition of hepatitis C virus replication by natural killer cells is associated with spontaneous clearance of acute hepatitis C in human immunodeficiency virus-positive patients

Hepatitis C virus (HCV) coinfection is an increasing health problem in human immunodeficiency virus‐positive (HIV+) individuals. However, a considerable proportion of HIV+ patients manage to overcome acute hepatitis C (AHC) spontaneously. In the present study, we analyzed the role of natural killer (NK) cells in modulating the course of AHC in HIV+ patients. Twenty‐seven HIV+ patients with AHC (self‐limited course: n = 10; chronic course: n = 17), 12 HIV+ patients with chronic hepatitis C (CHC), 8 HIV monoinfected individuals, and 12 healthy controls were studied. NK cells were phenotypically analyzed by flow cytometry. Interferon‐gamma (IFN‐γ) secretion, degranulation (CD107a), and anti‐HCV (= inhibition of HCV replication) activity of NK subpopulations were analyzed using the HuH7A2HCVreplicon cell system. NK cell frequency did not differ significantly between HIV+ patients with chronic and self‐limited course of AHC. However, we found NK cells from patients with self‐limiting infection to be significantly more effective in inhibiting HCV replication in vitro than NK cells from patients developing CHC. Of note, antiviral NK cell activity showed no significant correlation with NK cell degranulation, but was positively correlated with IFN‐γ secretion, and blocking experiments confirmed an important role for IFN‐γ in NK cell‐mediated inhibition of HCV replication. Accordingly, NK cells from patients that spontaneously cleared the virus displayed a stronger IFN‐γ secretion than those developing chronic infection. Finally, we observed high expression of NKG2D and NKp46, respectively, to be associated with self‐limiting course of aHCV. Accordingly, we found that blocking of these NK cell receptors significantly impaired antiviral NK cell activity. Conclusion: Our data suggest a strong IFN‐γ‐mediated antiviral NK cell response to be associated with a self‐limited course of AHC in HIV+ patients. (Hepatology 2014;59:814–827)

Hepatitis C virus core protein induces fibrogenic actions of hepatic stellate cells via toll-like receptor 2

Hepatic stellate cells (HSCs) represent the main fibrogenic cell type accumulating extracellular matrix in the liver. Recent data suggest that hepatitis C virus (HCV) core protein may directly activate HSCs. Therefore, we examined the influence of recombinant HCV core protein on human HSCs. Primary human HSCs and the human HSC line LX-2 were stimulated with recombinant HCV proteins core and envelope 2 protein. Expression of procollagen type I α-1, α-smooth muscle actin, cysteine- and glycine-rich protein 2, glial fibrillary acidic protein, tissue growth factor β1, matrix metalloproteinases 2 (MMP2) and 13, tissue inhibitor of metalloproteinases 1 and 2 was investigated by real-time PCR. Intracellular signaling pathways of ERK1/2, p38 and, jun-amino-terminal kinase (JNK) were analyzed by western blot analysis. Recombinant HCV core protein induced upregulation of procollagen type I α-1, α-smooth muscle actin, MMP 2 and 13, tissue inhibitor of metalloproteinases 1 and 2, tissue growth factor β1, cysteine- and glycine-rich protein 2, and glial fibrillary acidic protein mRNA expression, whereas HCV envelope 2 protein did not exert any significant effect. Blocking of toll-like receptor 2 (TLR2) with a neutralizing antibody prevented mRNA upregulation by HCV core protein confirming that the TLR2 pathway was involved. Furthermore, western blot analysis revealed HCV-induced phosphorylation of the TLR2-dependent signaling molecules ERK1/2, p38 and JNK mitogen-activated kinases. Our in vitro results demonstrate a direct effect of HCV core protein on activation of HSCs toward a profibrogenic state, which is mediated via the TLR2 pathway. Manipulating the TLR2 pathway may thus provide a new approach for antifibrotic therapies in HCV infection.

The CXCR3(+)CD56Bright Phenotype Characterizes a Distinct NK Cell Subset with Anti-Fibrotic Potential That Shows Dys-Regulated Activity in Hepatitis C

Background In mouse models, natural killer (NK) cells have been shown to exert anti-fibrotic activity via killing of activated hepatic stellate cells (HSC). Chemokines and chemokine receptors critically modulate hepatic recruitment of NK cells. In hepatitis C, the chemokine receptor CXCR3 and its ligands have been shown to be associated with stage of fibrosis suggesting a role of these chemokines in HCV associated liver damage by yet incompletely understood mechanisms. Here, we analyzed phenotype and function of CXCR3 expressing NK cells in chronic hepatitis C. Methods Circulating NK cells from HCV-infected patients (n = 57) and healthy controls (n = 27) were analyzed with respect to CXCR3 and co-expression of different maturation markers. Degranulation and interferon-γ secretion of CXCR3(+) and CXCR3(−) NK cell subsets were studied after co-incubation with primary human hepatic stellate cells (HSC). In addition, intra-hepatic frequency of CXCR3(+) NK cells was correlated with stage of liver fibrosis (n = 15). Results We show that distinct NK cell subsets can be distinguished based on CXCR3 surface expression. In healthy controls CXCR3(+)CD56Bright NK cells displayed strongest activity against HSC. Chronic hepatitis C was associated with a significantly increased frequency of CXCR3(+)CD56Bright NK cells which showed impaired degranulation and impaired IFN-γ secretion in response to HSC. Of note, we observed intra-hepatic accumulation of this NK cell subset in advanced stages of liver fibrosis. Conclusion We show that distinct NK cell subsets can be distinguished based on CXCR3 surface expression. Intra-hepatic accumulation of the functionally impaired CXCR3(+)CD56Bright NK cell subset might be involved in HCV-induced liver fibrosis.

DO LAMBDA-IFNS IL28A AND IL28B ACT ON HUMAN NATURAL KILLER CELLS?

In a recent paper, Dring et al. (1) showed that natural killer (NK) cell-associated killer cell Ig-like receptors (KIR) gene KIR2DS3 and IL28B (IFNλ3) T allele are associated with chronic hepatitis C, confirming earlier reports (2, 3). Interestingly, they showed that the presence of both genetic markers synergistically increased the risk of chronic infection over either factor alone (1).

TRAIL receptor I (DR4) polymorphisms C626G and A683C are associated with an increased risk for hepatocellular carcinoma (HCC) in HCV-infected patients

BackgroundTumour surveillance via induction of TRAIL-mediated apoptosis is a key mechanism, how the immune system prevents malignancy. To determine if gene variants in the TRAIL receptor I (DR4) gene affect the risk of hepatitis C virus (HCV)-induced liver cancer (HCC), we analysed DR4 mutations C626G (rs20575) and A683C (rs20576) in HCV-infected patients with and without HCC.MethodsFrequencies of DR4 gene polymorphisms were determined by LightSNiP assays in 159 and 234 HCV-infected patients with HCC and without HCC, respectively. 359 healthy controls served as reference population.ResultsDistribution of C626G and A683C genotypes were not significantly different between healthy controls and HCV-positive patients without HCC. DR4 variants 626C and 683A occurred at increased frequencies in patients with HCC. The risk of HCC was linked to carriage of the 626C allele and the homozygous 683AA genotype, and the simultaneous presence of the two risk variants was confirmed as independent HCC risk factor by Cox regression analysis (Odds ratio 1.975, 95% CI 1.205-3.236; p = 0.007). Furthermore HCV viral loads were significantly increased in patients who simultaneously carried both genetic risk factors (2.69 ± 0.36 × 106 IU/ml vs. 1.81 ± 0.23 × 106 IU/ml, p = 0.049).ConclusionsThe increased prevalence of patients with a 626C allele and the homozygous 683AA genotype in HCV-infected patients with HCC suggests that these genetic variants are a risk factor for HCC in chronic hepatitis C.

Regulatory CD4+ T cells modulate the interaction between NK cells and hepatic stellate cells by acting on either cell type.

BACKGROUND & AIMS NK cells regulate liver fibrosis by killing activated hepatic stellate cells (HSCs) and are controlled themselves by immune cells and/or soluble factors. Here, we analysed if CD4(+) regulatory T cells (Tregs) modify the interaction between NK cells and HSCs. METHODS The modification of NK cell activity against HSCs was studied in CD56(high)CD16(-) NK cells, using a flow cytometric CD107a degranulation assay and co-cultures with Tregs from healthy donors and patients with hepatitis C, respectively. We studied the underlying mechanisms in detail, applying Treg supernatants, Treg pretreated HSCs, and recombinant IL-8, TGF-ß1, and IL-10 as well as blocking experiments with neutralizing antibodies and analysed Treg-associated changes in the expression of NK cell receptor ligands on HSCs. RESULTS Tregs suppressed NK cell activation during HSC co-culture in a cell-contact-dependent manner involving the cytotoxic T-lymphocyte antigen 4 (CTLA-4). NK cell degranulation was further reduced, when HSCs had been pretreated with Tregs (p=0.043), Treg supernatants (p=0.001) or recombinant IL-8 (R=0.630, p=0.001) and TGF-ß1 (R=0.608, p=0.002), respectively. This additional inhibitory effect corresponded to the IL-8/TGF-ß1-mediated downregulation of MIC-A/B and HLA class-I on HSCs. Tregs from hepatitis C likewise inhibited NK cell activity, which was reversed significantly in specific blocking experiments. CONCLUSIONS Our data indicate that Tregs interfere with NK cell regulation of fibrogenesis via both direct cell-contact-dependent inhibition of NK cells and release of soluble factors, downregulating activating NK cell receptor ligands on HSCs. Our data may be particularly relevant for the intrahepatic accumulation of Tregs in chronic hepatitis C because downregulated NK cell activity against HSCs may blunt their control of fibrogenesis.

The ratio of calprotectin to total protein as a diagnostic and prognostic marker for spontaneous bacterial peritonitis in patients with liver cirrhosis and ascites.

Abstract Background: Diagnosis of spontaneous bacterial peritonitis (SBP) is based on a differential ascites leukocyte count which does not provide prognostic information. We performed a pilot study to assess calprotectin in ascites as an alternative diagnostic and prognostic marker. Methods: We collected ascites from patients with liver cirrhosis from March 2012 to July 2013. Routine clinical and laboratory data of the patients were recorded. Ascites calprotectin levels were determined by ELISA. Results: Overall, we collected 120 ascites samples from 100 patients with liver cirrhosis and from eight patients with malignant peritoneal effusion as disease control. Samples without infection had significantly lower calprotectin levels (median 34 ng/mL, range 5–795) than SBP samples (median 928 ng/mL, range 21–110,480; p<0.001) and malignant effusions (median 401, range 47–2596 ng/mL; p<0.001). In non-infected ascites, calprotectin levels were higher in Child-Pugh stage B versus C (median 57 ng/mL vs. 17 ng/mL; p<0.001) and in alcoholic versus viral cirrhosis (median 37 ng/mL vs. 10 ng/mL; p=0.015). The ratio of ascites calprotectin to total protein was a better marker for SBP than calprotectin alone (AUROC=0.93; p<0.001; sensitivity 93%, specificity 79%; positive predictive value 60%; negative predictive value 97%). In addition, high levels of the ratio to total protein were associated with poor 30-day survival (p=0.042). Conclusions: The ratio of ascites calprotectin to total protein may be a promising new diagnostic and prognostic marker in patients with liver cirrhosis and SBP and should be evaluated further.