Steatosis and intrahepatic lymphocyte recruitment in hepatitis C virus transgenic mice

Abstract

To assess the effects of constitutive hepatitis C virus (HCV) gene expression on liver, transgenic mice carrying the entire HCV open reading frame inserted in the a1 antitrypsin (A1AT) gene were generated. Expression of A1AT/HCV mRNA was found to be mainly limited to perivascular areas of the liver as indicated by in situ hybridization analysis. HCV core protein was detected in Western blots of liver extracts, whereas the expression of E2, NS3 and NS5 proteins was revealed by immunostaining of liver samples using HCV-specific antisera. Histological analysis of HCV transgenic mice showed that these animals develop extensive steatosis, but very little necrosis of liver tissue. Moreover, a consistent T cell infiltrate and a slight hepatocyte proliferation were observed. Phenotypic analysis of cells infiltrating the liver indicated that recruitment and/or expansion of residing CD8 + , NK, NKT and cd T cells occurred in transgenic animals. Among these cells, a large fraction of CD8 + T lymphocytes released mainly IL-10 and, to a lesser extent, IFN-c upon mitogenic stimulation in vitro. Furthermore, both intrahepatic lymphocytes and splenocytes did not produce cytokines in response to HCV antigens. Thus, these data indicate that constitutive expression of HCV proteins may be responsible for intrahepatic lymphocyte recruitment in absence of viral antigen recognition. This response is likely to be driven by virus-induced cellular factors and may play a significant role in the immunopathology of chronic HCV infection and liver disease. INTRODUCTIONHepatitis C virus (HCV) is a member of the Flaviviridae and is the major cause of non-A, non-B hepatitis (Choo et al., 1989;Houghton et al., 1991;Kuo et al., 1989). HCV has a single-stranded RNA genome of positive polarity of about 9?5 kb that contains a long open reading frame (ORF) encoding a polyprotein of approximately 3000 amino acids Kato et al., 1990;Takamizawa et al., 1991). The polyprotein precursor has the following gene order: NH 2 C-E1-E2-p7-NS2-NS3-NS4a-NS4b-NS5a-NS5b COOH (Eckart et al., 1993;Grakoui et al., 1993; Hijikata et al., 1993a, b;Lin et al., 1994;Tomei et al., 1993) C is an RNA-binding protein (Santolini et al., 1994) and is considered to be the viral nucleocapsid; E1 and E2 are thought to be the virion glycoproteins; p7 is a protein involved in the formation of ion channels (Griffin et al., 2004) and is inefficiently cleaved from the E2 polypeptide (Mizushima et al., 1994). Processing of the structural polypeptides is mediated by cellular signal peptidase (Hijikata et al., 1993b;Santolini et al., 1994). The HCVencoded metalloproteinase and serine protease located in the NS2 to NS3 region and N-terminal one-third of NS3 protein, respectively, mediate cleavages in the nonstructural region (Clarke, 1997).More than 170 million people worldwide are infected with HCV, and the complications of liver cirrhosis and hepatocellular carcinoma cause significant morbidity and mortality. The virus is cleared in a minority of patients and 70-80 % develop chronic infec...

Very low density lipoprotein and low density lipoprotein isolated from patients with hepatitis C infection induce altered cellular lipid metabolism

“…Indeed, HCV core protein has been reported to induce intracytoplasmic triglyceride-rich droplet accumulation in transfected cells [Barba et al, 1997]. Consistent with this data, Alonzi et al [2004] and others have reported that expression of viral proteins only causes steatosis in several transgenic animal models [reviewed in Fimia et al, 2003].…”

“…The demonstration of a direct and specific interaction of HCV proteins with lipoproteins would provide a potential molecular mechanism for our observations. To address this point we performed several Western blots on the proteic fraction of both LDL and VLDL of HCV infected patients, using different anti-HCV antibodies [Alonzi et al, 2004], collecting only negative results. Nevertheless, we believe that our data do not definitively rule out the hypothesis that HCV may directly or indirectly interfere with molecular lipoproteins structure.…”

Hepatitis C virus core protein impairs in vitro priming of specific T cell responses by dendritic cells and hepatocytes

“…It is also well established by now that HC can interact with and prime naïve CD8 + T cells in vivo, although function and role of these T cells are yet unclear [11,13,19]. The way in which alteration of hepatocyte phenotype influences specific T cell responses in vivo will be examined using the HCV tg mice which express HCVc exclusively in the liver [14,27].…”

“…C57BL/6J (H-2 b ) (B6) mice, A b /OVA TCR transgenic OT-II B6 mice, K b /OVA TCR transgenic OT-I B6 and B6 HCV transgenic mice [14] were bred and kept under standard pathogen-free conditions in the animal colony of Ulm University (Ulm, Germany). Male and female mice were used at 10-14 weeks of age.…”

A high glucose condition sensitizes human hepatocytes to hydrogen peroxide-induced cell death

“…ROS generation resulting in abnormal mitochondrial function has been observed in NASH, and oxidative stress plays a role not only in hepatic steatosis but also in hepatic fibrosis (7). HCV also causes mitochondrial damage in hepatocytes and increases ROS (8,9), followed by ROS-induced hepatic steatosis (10,11). Hepatic cancer in HCV transgenic mice is moreover associated with the generation of ROS (12).…”