The Mechanism Of Innate Immune Cells In HBV Tolerance And HCC

The liver works as a metabolic organ and plays important roles in glucose, protein and lipid metabolism. While the liver is a unique immune organ, because of predominant innate immune cells, and actively involved in autoimmune diseases, microbial infection and tumor immune-surveillance. The liver is also recognized as immune-tolerant organ, since liver has enriched regulatory cells and the unique structural characteristics and therefore foster liver allo-grafts, blood and intestinal derived antigens and also chronic hepatotropic microbe infection.Hepatotropic virus infections, such as hepatitis B virus (HBV) infection usually results in Chronic Hepatitis B (CHB) infection, accompanying with persistent expression of HBV antigens and impaired virus-specific cellular and humoral immune response though they are crucial to eliminate virus. Innate immune response, shortage of viral specific property, is also important for viral control and can promote the adaptive immune response. For example, NK cells and type I helper T cell derived IL-2, Dendritic cells and kupffer cells presented antigens are critical for adaptive immune response. However, they maybe harbor regulatory function. In this study we focus on an innate like T cells-γδT cells-and the roles in the process of HBV induced liver tolerance, which act more like bystander.Moreover, CHB has been considered closely related to HCC (Hepatocellular Carcinoma, HCC). Because about300thousand people die from liver tumors in China each year and HBV carriers take up the majority. HBV infection induced liver tumor has been explained with the viral genome insertion induced and HBx protein induced liver cells malignancy. Meanwhile persistent liver inflammation is always observed in the chronic HBV carrier, suggesting chronic inflammation can promote the development of HCC. Thus, targeting liver inflammation maybe provides a theoretical basis for clinical treatment. Our study here support persistent liver inflammation promote liver tumor development, and NK cells play an important function in this process.I, γδT cells modulate HBV-induced toleranceWe constructed HBV-carrier mice by using pAAV/HBV1.2plasmid and recombinant AAV/HBV1.3virus, wild type C57BL/6mice carry persistent expression of viral antigens in the liver hepatocytes and secret outside the cell in the serum with high levels of expression of HBsAg, while almost no liver inflammation, accompanying insufficient antigen-specific humoral immune response and T cell immune response; which can mimic immune tolerance phase during the chronic HBV infection.Next, we detected the number of yδT cells-Vy4subset in particular, is significant upregulation in the HBV-carrier mice. While we injected TCR-/-mice with pAAV/HBV1.2, were observed HBV-tolerance could be not established with quickly disappeared HBV antigen expression in the serum and liver. Similar results obtained after y8T cells depletion by anti-yδTCR antibody. Further we adoptively transferred yδT cells to TCRδ-/-mice, serum high concentration of HBV antigen maintained. Thus, y8T cell is crucial for HBV-induced tolerance.Later, we did not detect elevated HBV-specific humoral immune response between HBV-carrier wild type and TCRδ-/-mice; in addition, hepatic regulatory T cells and Kupffer cells were also not alter between them. Interestingly, HBV-specific CD8+T cell number and activity were notable increased as there were exhausted in the wild type HBV-carrier mice, HBV tolerance was reserved if depletion of CD8+T cells in TCRδ-/-HBV-carrier mice.Furthermore, we found that y8T cells play a bystander effect to CD8+T cells exhaustion. Persistent HBV antigen expression induced y8T cells to produce IL-17, which recruited myeloid suppressor cells (MDSC) into the liver. And MDSC directly inhibited CD8+T cells activation in a dependent manner of iNOS and arginase-1. We also observed a significant decrease MDSC in HBV-carrier IL-17-/-mice, while CD8+T cell function recovered. Treatment HBV-carrier mice with arginase-1in vivo could restore CD8+T cell function and promote elimination of HBV.In summary; γδT cells as an innate-like T cells, play important role in the formation of HBV-induced tolerance by inducing hepatic accumulation of MDSC mediated viral specific CD8+T cell exhaustion. Targeting this process can significantly improve HBV-specific T cells response and promote HBV clearance.II, NK cells resist to CC14-induced hepatocellular carcinoma.We use HBV-transgenic mice in this study as these mice can spontaneous develop liver tumors with sustained liver inflammation at about17month-old, which greatly mimic HBV-induced hepatocellular carcinoma in clinical patients. To strengthen the hypothesis that chronic inflammation may promote tumor development, we continuously injected CC14to the HBV-transgenic mice, and observed liver tumor after six months treatment, suggesting that chronic inflammation is indeed fostering liver tumorigenesis.Furthermore, we found aggravating epithelial-mesenchymal transition between (EMT) occurred in HBV transgenic mice during chronic liver inflammation. EMT is considered as an important mechanism for tumor growth and migration. We noted that NK cells were suppressed during chronic inflammation induced liver tumor with downregulated activation molecules and upregulated inhibitory molecules. We later observed that enhanced vimentin expression-EMT marker-in the liver after NK cells depletion. And a significant increase in liver tumors developed during chronic inflammation in the HBV-transgenic mice after clearing NK cells, thus NK cells are critical for liver tumor immunosurveillance.Moreover, our model of chronic inflammation induced liver tumor may also be useful for studying the prevention and therapy of liver cancer. Non-steroidal anti-inflammatory drug (NSAIDs) and immune-suppressive agents were used to investigate the effect in prevention persistent inflammation induced liver tumor. We found here that immune-suppressive agents-rapamycin and cyclosporine treatment promoted liver tumor development. We also examined two pieces of NSAIDs-diclofenac and aspirin; diclofenac could quickly downregulated CC14-induced liver damage but had aggravated side effect during long-time oral administration. However, oral aspirin seems benefit for control tumor development and body weight. Besides, PolyI:C-a short RNA double strand mimics used for hepatic NK cell expansion and activation-treatment may significantly resist liver cancer development.In summary, we have built a practical model of chronic inflammation-induced liver tumors, and observed NK cells were important to resist liver tumor by inhibition of EMT. The usage of NSAIDs aspirin but not immunosuppressive agents can suppress tumor development in the HBV-transgenic mice.