Cirrhosis Hampers Early and Rapid Normalization of Natural Killer Cell Phenotype and Function in Hepatitis C Patients Undergoing Interferon-Free Therapy

Hepatitis C Virus and the Host: A Mutual Endurance Leaving Indelible Scars in the Host's Immunity

Hepatitis C virus (HCV) has spread worldwide, and it is responsible for potentially severe chronic liver disease and primary liver cancer. Chronic infection remains for life if not spontaneously eliminated and viral persistence profoundly impairs the efficiency of the host's immunity. Attempts have been made to develop an effective vaccine, but efficacy trials have met with failure. The availability of highly efficacious direct-acting antivirals (DAA) has created hope for the progressive elimination of chronic HCV infections; however, this approach requires a monumental global effort. HCV elicits a prompt innate immune response in the host, characterized by a robust production of interferon-α (IFN-α), although interference in IFN-α signaling by HCV proteins may curb this effect. The late appearance of largely ineffective neutralizing antibodies and the progressive exhaustion of T cells, particularly CD8 T cells, result in the inability to eradicate the virus in most infected patients. Moreover, an HCV cure resulting from DAA treatment does not completely restore the normal immunologic homeostasis. Here, we discuss the main immunological features of immune responses to HCV and the epigenetic scars that chronic viral persistence leaves behind.

Ablation of Tumor Necrosis Factor Alpha Receptor 1 Signaling Blunts Steatohepatitis in Peroxisome Proliferator Activated Receptor α-Deficient Mice

Tumor necrosis factor -alpha (TNFα) is strongly associated with fatty liver disease (i.e, hepatosteatosis). Cytokine production has been thought of as a consequence of hepatic lipid accumulation which becomes a critical factor in the development of chronic liver pathologies as well as insulin resistance. The purpose of this study was to test the hypothesis that TNFα directly regulates lipid metabolism in liver in the mutant peroxisome-proliferator activated receptor-alpha (PPARα^-/-) mouse model with robust hepatic lipid accumulation. At 10 weeks of age, TNFα and TNF receptor 1 expression are increased in livers of PPARα^-/- mice compared to wild type. PPARα^-/- mice were then crossed with mice lacking the receptor for TNFα receptor 1 (TNFR1^-/-). Wild type, PPARα^-/-, TNFR1^-/-, PPARα^-/- x TNFR1^-/- mice were housed on ad-libitum standard chow diet for up to 40 weeks. Increases in hepatic lipid and liver injury and metabolic disruption associated with PPARα ablation were largely blunted when PPARα^-/- mice were crossed with TNFR1^-/- mice. These data support the hypothesis that TNFR1 signaling is critical for accumulation of lipid in liver. Therapies that reduce pro-inflammatory responses, namely TNFα, could have important clinical implications to reduce hepatosteatosis and progression of severe liver disease.

The antifibrotic role of natural killer cells in liver fibrosis

Liver fibrosis is the common pathological change of chronic liver diseases characterized by increased deposition of extracellular matrix and reduced matrix degradation. In response to liver injury caused by a variety of pathogenic agents, such as virus and alcohol, hepatic stellate cells (HSCs) are differentiated into myofibroblast-like cells and produce excessive collagens, thus resulting in fibrogenesis. Natural killer (NK) cells are the essential innate immune cells in the liver and generally control fibrosis by killing activated HSCs. This review briefly describes the fibrogenesis process and the phenotypic features of hepatic NK cells. Besides, it focuses on the antifibrotic mechanisms of NK cells and explores the potential of activating NK cells as a therapeutic strategy for the disease.

Splenic CD4+ and CD8+ T-cells highly expressed PD-1 and Tim-3 in cirrhotic patients with HCV infection and portal hypertension

Introduction: The spleen plays an important role in regulating the immune response to infectious pathogens. T-cells dysfunction and exhaustion have been reported in patients with hepatitis B/C virus (HBV/HCV) infection, which contributes to persistent virus infection. The aims of this study were to investigate spleen-related evidence of immunosuppression and immune tolerance in HCV cirrhotic patients with portal hypertension (PH). Methods: The expression of programmed cell death 1 (PD-1), T-cell immunoglobulin domain and mucin domain-containing molecule-3 (Tim-3) and its ligand PD-L1/2, and Galectin-9 in the spleens and livers of HCV cirrhotic patients (n = 15) was analyzed using real-time PCR and immunohistochemistry. Flow cytometry was used to evaluate the expression of PD-1 and Tim-3 on splenic T-cells and the peripheral blood T-cells before and after splenectomy (n = 8). Results: Spleens from patients with PH showed significantly increased mRNA levels of PD-L2, Tim-3, Galectin-9, CD80, and CD86, and decreased levels of CD28 compared to control spleens (spleens removed due to traumatic injury) (all p < 0.05). Additionally, protein expression of inhibitory signaling molecules was significantly increased in both the spleens and livers of cirrhotic patients compared with controls (all p < 0.05). Peripheral blood and splenic CD4⁺ and CD8⁺ T-cells also expressed higher protein levels of PD-1, Tim-3, and CTLA-4 in cirrhotic patients as compared with healthy controls (all p < 0.05). The proportion of PD-1⁺CD4⁺T lymphocytes (26.2% ± 7.12% vs. 21.0% ± 9.14%, p = 0.0293) and Tim-3⁺CD8⁺ T lymphocytes (9.4% ± 3.04% vs. 6.0% ± 2.24%, p = 0.0175) in peripheral blood decreased followed splenectomy. Conclusion: The CD4⁺ and CD8⁺ T-cells in spleen and peripheral blood highly expressed PD-1 and Tim-3 in HCV-infected and cirrhotic patients with portal hypertension. Highly expressed PD-1 and Tim-3 in peripheral blood T-lymphocytes can be partly reversed following splenectomy.

Gender as a factor affecting NK cell activity in patients successfully treated for chronic hepatitis C with direct-acting antivirals

Chronic hepatitis C (CHC) affects the activity of natural killer (NK) cells, but successful interferon- free treatment partially restores it. The goal of this study was to assess whether gender influences NK functionality. We examined 21 post-menopausal women and 24 men with CHC who were treated with direct-acting antivirals (DAA) and 33 healthy volunteers. Using flow cytometry, we analysed KIR2DS4, NKG2D, NKp30, KIR2DL2/DL3, NKG2A and TRAIL on the surface of NK cells. Intracellular granzyme B was also assessed and serum CXCL10 was quantified via ELISA. Overall, patients with CHC had higher expression of KIR2DS4, NKG2A, and NKp30 relative to the control group. Further, CHC patients had a lower percentage of NK cells among lymphocytes relative to the control group. After treatment, KIR2DS4, KIR2DL2/DL, NKG2A, TRAIL and NKp30 on NK cells were decreased whilst the percentage of NK cells and the expression of granzyme B and NKG2D increased. Prior to treatment, serum CXCL10 was elevated, but it was inhibited post-treatment. We observed gender-specific differences in the expression of KIR2DL2/DL3 (higher in women) and NKp30 (elevated in men) compared to CHC/control groups. After treatment, KIR2DL2/DL3, NKp30 and CXCL10 dropped only in the female group while granzyme B increased in the male group. In conclusion, the response of NK cells among men and women of post-menopausal ages with CHC differs. Our research may lead to more studies on the different nature of female and male immune systems in the context of HCV infection and treatment.

Viral Hepatitis and Hepatocellular Carcinoma: State of the Art

Viral hepatitis is one of the main causes leading to hepatocellular carcinoma (HCC). The continued rise in incidence of HCC suggests additional factors following infection may be involved. This review examines recent studies investigating the molecular mechanisms of chronic hepatitis and its association with hepatocarcinogenesis. Hepatitis B virus patients with genotype C display an aggressive disease course leading to HCC more than other genotypes. Furthermore, hepatitis B excretory antigen (HBeAg) seems to be a more sensitive predictive tumor marker exhibiting a six-fold higher relative risk in patients with positive HBsAg and HBeAg than those with HBsAg only. Single or combined mutations of viral genome can predict HCC development in up to 80% of patients. Several mutations in HBx-gene are related with higher HCC incidence. Overexpression of the core protein in HCV leads to hepatocellular lipid accumulation associated with oncogenesis. Reduced number and decreased functionality of natural killer cells in chronic HCV individuals dysregulate their surveillance function in tumor and viral cells resulting in HCC. Furthermore, high T-cell immunoglobulin and mucin 3 levels supress CD8+ T-cells, which lead to immunological dysregulation. Hepatitis D promotes HCC development indirectly via modifications to innate immunity, epigenetic alterations and production of reactive oxygen species with the LHDAg being the most highly associated with HCC development. Summarizing the results, HBV and HCV infection represent the most associated forms of viral hepatitis causing HCC. Further studies are warranted to further improve the prediction of high-risk patients and development of targeted therapeutics preventing the transition from hepatic inflammation–fibrosis to cancer.

Chronic genotype 1 hepatitis C along with cirrhosis drives a persistent imprint in virus-specific CD8+ T cells after direct-acting antiviral therapies

Chronic hepatitis C virus (HCV) infection impairs HCV CD8⁺ T-cell responses, while it could influence immune responses towards unrelated viruses/vaccines (e.g. cytomegalovirus, CMV, and influenza, Flu). The aim of our study was to delineate whether restoration of these virus-specific CD8⁺ T cells occurs after direct-acting antiviral (DAA) therapies and particularly in patients with cirrhosis. We performed longitudinal analysis (baseline, week 4, follow-up [FU] 12 and FU48) of virus-specific CD8⁺ T cells by multicolour flow cytometry in HCV-cirrhotic patients undergoing DAA therapy (n = 26) after in vitro expansion with immunodominant HCV, CMV and Flu epitopes restricted by HLA-A*02. HCV noncirrhotic patients (n = 9) and healthy individuals (n = 10) served as controls. We found that the proliferative capacity of HCV-specific CD8⁺ T cells increased from baseline up to FU48 in a significant proportion of cirrhotic and noncirrhotic patients. Nevertheless, these cells remained poor cytokine producers in both patient groups, regardless of the down-regulation of inhibitory co-regulatory receptors in HCV-cirrhotic patients at FU48. Likewise, high expression levels of these exhaustion markers were detected in CMV-/Flu-specific CD8⁺ T cells in HCV-cirrhotic patients at all time points, albeit without affecting their proliferative capacity or cytokine production. We conclude that DAA therapies induce restoration of the proliferative capacity of HCV-specific CD8⁺ T cells. However, these cells remain phenotypically and functionally impaired. Contrarily, the 'exhausted' phenotype in CMV-/Flu-specific CD8⁺ T cells in HCV-cirrhotic patients did not associate with their functions. Larger studier with longer follow-up may elucidate whether this complex interplay influences the outcome of cirrhotic patients.