Significance of the balance between regulatory T (Treg) and T helper 17 (Th17) cells during hepatitis B virus related liver fibrosis

Effects of antiviral therapy on preventing liver tumorigenesis and hepatocellular carcinoma recurrence

Chronic hepatitis B virus (HBV) infection is the key driving force of liver disease progression, resulting in the development of hepatic dysfunction, cirrhosis and hepatocellular carcinoma (HCC). The primary aim of therapy is to suppress or eliminate HBV replication to reduce the activity of hepatitis, thus reducing the risk of, or slowing the progression of, liver disease. Nucleos(t)ide analogues (Nucs) may result in rapid suppression of HBV replication with normalization of serum transaminases and restore liver function, thus increasing survival in patients with hepatic decompensation. Long-term Nuc therapy may result in histological improvement or reversal of advanced fibrosis and reduction in disease progression, including the development of HCC. The long-term benefits of a finite course of interferon (IFN)-α therapy also include a sustained and cumulative response, as well as hepatitis B surface antigen seroclearance and reduction in the development of cirrhosis and/or HCC. Pegylated IFN and newer Nucs may achieve better long-term outcomes because of improved efficacy and a low risk of drug resistance. However, treatment outcomes are still far from satisfactory. Understanding the effects of anti-HBV treatment against HCC incidence and recurrence after hepatectomy or liver transplantation is required for further improvement of outcome.

Adoptive transfer of regulatory T cells protects against Coxsackievirus B3-induced cardiac fibrosis

Background

Cardiac fibrogenesis in the late stage of viral myocarditis causing contractile dysfunction and ventricular dilatation, is a major pathogenic factor for the progression of myocarditis to serious cardiovascular diseases including dilated cardiomyopathy (DCM) and congestive heart failure (HF). Recent studies indicate that regulatory T cells (Tregs) are involved in the fibrotic process of liver and lung fibosis. However, the role of Tregs in the development of viral myocarditis-caused cardiac fibrosis and their therapeutic potential remains unclear.

Methodology/Principal Findings

Myocardial fibrosis was induced in BALB/c mice by intraperitoneal injection of Coxsackievirus B3 (CVB3) assessed by picrosirius red staining and detection of expression levels of collagen I, matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-3 (MMP-3) and tissue inhibitor of metalloproteinase-1 (TIMP-1). Myocardial Treg frequency was down-regulated during the course of viral myocarditis and a negative correlation with the severity of cardiac fibrosis was found. To explore the role of Tregs in CVB-induced cardiac fibrosis, Treg was in vivo depleted by injecting anti-CD25 mAb which resulted in aggravation of cardiac fibrosis. In consistent with that, after adoptive transfer of isolated Tregs into mice, significant amelioration of CVB3-induced cardiac fibrosis was confirmed. Interleukin-10 (IL-10) neutralizing antibodies were used in vivo and in vitro to explore the molecular mechanism of the therapeutic effect of Treg. It was found that administration of anti-IL-10 mAb after Treg transfer abrogated Treg’s treating effect and the inhibition of Treg on collagen production by cardiac fibroblasts was mediated mainly through IL-10.

Conclusion/Significance

Our data suggested that Tregs have a protective role in the fibrotic process of CVB3-induced cardiac fibrosis via secreting IL-10 and might provide an alternative option for the future treatment of cardiac fibrosis.

The co-inhibitory pathway and cellular immune imbalance in the progress of HBV infection

OBJECTIVE

Chronic hepatitis B (CHB) affects 400 million people and is the most common cause of liver cirrhosis (LC) and hepatocellular carcinoma (HCC) worldwide. Cellular immune regulation plays an important role in determining the infection outcome. Co-signal molecules and Th17/Treg were studied to explore their association with the progression of HBV infection.

METHODS

Ninety-four HBV-infected patients were categorized into three groups: 31 patients with LC caused by CHB, 30 with HCC caused by CHB and 33 with HCC caused by CHB. Co-signal molecules, Th17/Treg, and Stat3 and Stat5 were analyzed by flow cytometry.

RESULTS

CHB patients who progressed to LC or HCC showed a significantly higher level of co-inhibitory molecules such as BTLA and PD-1, while there was no significant difference in co-stimulatory molecules among LC, HCC and CHB. Stat3 and Stat5 were significantly increased in LC and HCC compared to CHB patients.

CONCLUSION

Co-inhibitory molecules play more important roles than co-stimulatory molecules. Increased PD-1 and BTLA/HVEM inhibited immune cells and the immune process. At the same time activated Stat3 and Stat5 stimulate the key factors in differentiation of Th17 and Treg, thus leading to imbalanced expansion of Th17 and Treg; immune tolerance was induced and HBV persistent. This resulted in hepatic inflammation that progressed to cirrhosis and carcinoma.

Induction of regulatory T cells by high-dose gp96 suppresses murine liver immune hyperactivation

Immunization with high-dose heat shock protein gp96, an endoplasmic reticulum counterpart of the Hsp90 family, significantly enhances regulatory T cell (Treg) frequency and suppressive function. Here, we examined the potential role and mechanism of gp96 in regulating immune-mediated hepatic injury in mice. High-dose gp96 immunization elicited rapid and long-lasting protection of mice against concanavalin A (Con A)-and anti-CD137-induced liver injury, as evidenced by decreased alanine aminotransaminase (ALT) levels, hepatic necrosis, serum pro-inflammatory cytokines (IFN-γ, TNF-α, and IL-6), and number of IFN-γ ⁺ CD4⁺ and IFN-γ ⁺ CD8⁺ T cells in the spleen and liver. In contrast, CD4⁺CD25⁺Foxp3⁺ Treg frequency and suppressive function were both increased, and the protective effect of gp96 could be generated by adoptive transfer of Treg cells from gp96-immunized mice. In vitro co-culture experiments demonstrated that gp96 stimulation enhanced Treg proliferation and suppressive function, and up-regulation of Foxp3, IL-10, and TGF-β1 induced by gp96 was dependent on TLR2- and TLR4-mediated NF-κB activation. Our work shows that activation of Tregs by high-dose gp96 immunization protects against Con A- and anti-CD137-induced T cell-hepatitis and provides therapeutic potential for the development of a gp96-based anti-immune hyperactivation vaccine against immune-mediated liver destruction.

Hepatitis B virus induces IL-23 production in antigen presenting cells and causes liver damage via the IL-23/IL-17 axis

IL-23 regulates myriad processes in the innate and adaptive immune systems, and is a critical mediator of the proinflammatory effects exerted by Th17 cells in many diseases. In this study, we investigated whether and how hepatitis B virus (HBV) causes liver damage directly through the IL-23 signaling pathway. In biopsied liver tissues from HBV-infected patients, expression of both IL-23 and IL-23R was remarkably elevated. In vivo observations also indicated that the main sources of IL-23 were myeloid dendritic cells (mDCs) and macrophages. Analysis of in vitro differentiated immature DCs and macrophages isolated from healthy donors revealed that the HBV surface antigen (HBsAg) efficiently induces IL-23 secretion in a mannose receptor (MR)-dependent manner. Culture with an endosomal acidification inhibitor and the dynamin inhibitor showed that, upon binding to the MR, the HBsAg is taken up by mDCs and macrophages through an endocytosis mechanism. In contrast, although the HBV core antigen (HBcAg) can also stimulate IL-23 secretion from mDCs, the process was MR- and endocytosis-independent. In addition, IL-23 was shown to be indispensible for HBsAg-stimulated differentiation of naïve CD4(+) T cells into Th17 cells, which were determined to be the primary source of IL-17 in HBV-infected livers. The cognate receptor, IL-17R, was found to exist on the hepatic stellate cells and mDCs, both of which might represent the potential target cells of IL-17 in hepatitis B disease. These data provide novel insights into a yet unrecognized mechanism of HBV-induced hepatitis, by which increases in IL-23 expression, through an MR/endocytosis-dependent or -independent manner, produce liver damage through the IL-23/IL-17 axis.

Th17 cells and liver diseases

In recent years, it has been demonstrated that T helper cells 17 (Th17) are closely related to the occurrence and development of many kinds of liver diseases such as viral hepatitis, autoimmune liver diseases and fatty liver diseases. Th17 cells are a new CD4⁺ T cell subset, which can interact with Th1, Th2 and Treg cells. There exists complex antagonistic or collaborative relationship among these cells. Understanding the role of Th17 cells in liver diseases will help explore the pathogenesis and treatment of these diseases.

Changes in CD4+ T lymphocyte subsets and clinical outcomes of hepatitis B virus infection

Various clinical manifestations may develop in people infected with hepatitis B virus (HBV), ranging from asymptomatic infection to acute severe hepatitis B. Some infections become self-limiting when the virus is cleared, while approximately 90% of children and 10% of adults become HBV carriers or patients with chronic hepatitis B, who can further develop cirrhosis and hepatocellular carcinoma. CD4⁺ T lymphocytes play a central role in anti-infection immunity and can be divided into different subsets, including Th1, Th2, Treg, Th17, Th22, Th9 and Tfh. These T lymphocyte subsets all come from the same progenitor cells (Th0), although they have particular differentiation pathway and secrete different kinds of cytokines. Furthermore, they are able to interact with each other and change into each other. Particularly, the balances of Th1/Th2 and Th17/Treg play a vital role in determining the clinical outcomes of HBV infection.

The serum IL-6 profile and Treg/Th17 peripheral cell populations in patients with type 1 diabetes

IL-6 is a pleiotropic cytokine involved in the regulation of the immune response, inflammation, and hematopoeisis. Its elevated levels are found in a range of autoimmune and chronic inflammatory diseases. IL-6 is also involved in regulation of the balance between two T cell subsets: Tregs and Th17, which have contradictory functions in the control of inflammation. The present study provides a quantitative analysis regarding the Th17/Treg cell balance in peripheral blood of children with type 1 diabetes and its association with serum IL-6 level.

IL-22 and IL-17 mRNA expression in PBMCs from patients with chronic hepatitis B virus infection

AIM: To detect the expression of IL-22 and IL-17 mRNAs in peripheral blood mononuclear cells (PBMCs) from patients with chronic hepatitis B (CHB) infection and to analyze their significance in the pathogenesis of CHB.

METHODS: Thirty-three patients with moderate CHB, 21 patients with severe CHB, 16 patients with liver failure, and 16 cirrhotic patients were enrolled in the study. Ten healthy volunteers were used as controls. RT-PCR method was used to detect the expression of IL-22 and IL-17 mRNAs in PBMCs from these subjects.

RESULTS: IL-22 expression in PBMCs from patients with moderate CHB, severe CHB, or cirrhosis was comparable, but all was higher than that from controls (P = 0.000). IL-22 expression in PBMCs from patients with liver failure was significantly lower than that from other three groups of patients (P = 0.000). IL-17 expression in PBMCs from four groups of patients was higher than that from controls (P = 0.000). IL-17 expression in PBMCs from patients with liver failure was slightly lower than that from other three groups of patients, although no statistical difference was found.

CONCLUSION: Down-regulation of IL-22 is unfavorable to repair of hepatic cells after liver injury. Up-regulation of IL-22 expression may be important in alleviating liver damage. IL-17 levels in patients infected with HBV are increased significantly. IL-17 may participate in the inflammatory process in chronic HBV infection and play an important role in development of liver fibrosis.