Preserved MHC-II antigen processing and presentation function in chronic HCV infection

Strategies Targeting the Innate Immune Response for the Treatment of Hepatitis C Virus-Associated Liver Fibrosis

Direct-acting antivirals eliminate hepatitis C virus (HCV) in more than 95% of treated individuals and may abolish liver injury, arrest fibrogenesis, and reverse fibrosis and cirrhosis. However, liver regeneration is usually a slow process that is less effective in the late stages of fibrosis. What is more, fibrogenesis may prevail in patients with advanced cirrhosis, where it can progress to liver failure and hepatocellular carcinoma. Therefore, the development of antifibrotic drugs that halt and reverse fibrosis progression is urgently needed. Fibrosis occurs due to the repair process of damaged hepatic tissue, which eventually leads to scarring. The innate immune response against HCV is essential in the initiation and progression of liver fibrosis. HCV-infected hepatocytes and liver macrophages secrete proinflammatory cytokines and chemokines that promote the activation and differentiation of hepatic stellate cells (HSCs) to myofibroblasts that produce extracellular matrix (ECM) components. Prolonged ECM production by myofibroblasts due to chronic inflammation is essential to the development of fibrosis. While no antifibrotic therapy is approved to date, several drugs are being tested in phase 2 and phase 3 trials with promising results. This review discusses current state-of-the-art knowledge on treatments targeting the innate immune system to revert chronic hepatitis C-associated liver fibrosis. Agents that cause liver damage may vary (alcohol, virus infection, etc.), but fibrosis progression shows common patterns among them, including chronic inflammation and immune dysregulation, hepatocyte injury, HSC activation, and excessive ECM deposition. Therefore, mechanisms underlying these processes are promising targets for general antifibrotic therapies.

The role of innate immunity in the immunopathology and treatment of HBV infection

In this review we give a brief update on sensors recently determined to be capable of detecting HBV, and examine how the virus represses the induction of pro-inflammatory cytokines like type I interferons. We overview cellular components of innate immunity that are present at high frequencies in the liver, and discuss their roles in HBV control and/or pathogenesis. We argue that many innate effectors have adaptive-like features or can exert specific effects on HBV through immunoregulation of T cells. Finally we consider current and possible future strategies to manipulate innate immunity as novel approaches towards a functional cure for HBV.

Production of CD4⁺ and CD8⁺ T cell hybridomas

T cell hybridomas are very useful tools to investigate antigen presenting cell (APC) function. They were developed based on the fusion technology that led to monoclonal antibody section. Antigen-specific primary T cells are generated and fused to an immortal thymoma line. Unfused thymoma cells are eliminated by engineered metabolic selection. Antigen-specific hybridomas are identified and may be characterized in detail. Primary T cells are preferable for studies of the regulatory mechanisms intrinsic to T cells, but for study of antigen presentation T cell hybridomas have advantages over primary T cell clones, including their relative uniformity, stability over time, and ready availability in large numbers for extensive antigen presentation experiments.

Dendritic cells, regulatory T cells and the pathogenesis of chronic hepatitis C

Hepatitis C virus (HCV) is a small, enveloped RNA virus and a major cause of chronic liver disease. Resolution of primary HCV infections depends upon the vigorous responses of CD4⁺ and CD8⁺ T cells to multiple viral epitopes. Although such broad-based responses are readily detected early during the course of infection regardless of clinical outcome, they are not maintained in individuals who develop chronic disease. Ostensibly, a variety of factors contribute to the diminished T cell responses observed in chronic, HCV-infected patients including impaired dendritic cell function and the induction of CD4⁺FoxP3⁺ regulatory T cells. Overwhelming evidence suggests that the complex interaction of dendritic cells and regulatory T cells plays a critical role in the pathogenesis of chronic hepatitis C.

Dendritic cell-based immunity and vaccination against hepatitis C virus infection

Hepatitis C virus (HCV) has chronically infected an estimated 170 million people worldwide. There are many impediments to the development of an effective vaccine for HCV infection. Dendritic cells (DC) remain the most important antigen-presenting cells for host immune responses, and are capable of either inducing productive immunity or maintaining the state of tolerance to self and non-self antigens. Researchers have recently explored the mechanisms by which DC function is regulated during HCV infection, leading to impaired antiviral T-cell responses and so to persistent viral infection. Recently, DC-based vaccines against HCV have been developed. This review summarizes the current understanding of DC function during HCV infection and explores the prospects of DC-based HCV vaccine. In particular, it describes the biology of DC, the phenotype of DC in HCV-infected patients, the effect of HCV on DC development and function, the studies on new DC-based vaccines against HCV infection, and strategies to improve the efficacy of DC-based vaccines.

Dendritic cells in hepatitis C infection: can they (help) win the battle?

Infection with hepatitis C virus (HCV) is a public health problem; it establishes a chronic course in ~85% of infected patients and increases their risk for developing liver cirrhosis, hepatocellular carcinoma, and significant extrahepatic manifestations. The mechanisms of HCV persistence remain elusive and are largely related to inefficient clearance of the virus by the host immune system. Dendritic cells (DCs) are the most efficient inducers of immune responses; they are capable of triggering productive immunity and maintaining the state of tolerance to self- and non-self antigens. During the past decade, multiple research groups have focused on DCs, in hopes of unraveling an HCV-specific DC signature or DC-dependent mechanisms of antiviral immunity which would lead to a successful HCV elimination strategy. This review incorporates the latest update in the current status of knowledge on the role of DCs in anti-HCV immunity as it relates to several challenging questions: (a) the phenotype and function of diverse DC subsets in HCV-infected patients; (b) the characteristics of non-human HCV infection models from the DCs' point of view; (c) how can in vitro systems, ranging from HCV protein- or peptide-exposed DC to HCV protein-expressing DCs, and in vivo systems, ranging from HCV protein-expressing transgenic mice to HCV-infected non-human primates, be employed to dissect the role of DCs in triggering/maintaining a robust antiviral response; and (d) the prospect of DC-based strategy for managing and finding a cure for HCV infection.