The long term goal of these studies is to define the host-virus Interactions that occur during hepatitis C virus (HCV) infection with the hope that this knowledge will lead to the discovery of improved therapeutic approaches to this important human pathogen. HCV is a noncytopathic, positive-strand RNA virus that causes acute and chronic hepatitis and hepatocellular carcinoma. Approximately 2-4 million persons are chronically infected by HCV in the USA and 170 million people are chronically infected worldwide, many of whom will die from liver failure and hepatocelluar carcinoma. Elegant in vitro experiments have revealed that HCV strongly inhibits type 1 IFN production in infected cells by blocking the retinoid inducible gene-I (RIG-I)- mediated pathway. In contrast, HCV strongly Induces type 1 IFN responses in the liver despite this evasion mechanism. This discrepancy suggests that HCV might trigger type 1 IFN production in the liver by cells other than infected hepatocytes. In experiments that form the basis of this application, we showed that human peripheral blood plasmacytoid dendritic cells (pDCs) produce large amounts of IFNa and IFNb when they are cocultured with HCV-infected human hepatoma-derived Huh-7 cells. We also showed that IFN production correlates strongly with the HCV RNA content of the Huh-7 cells, that it requires direct cell-cell contact between the pDCs and the infected cells, that it is not induced by free infectious HCV particles, and that it is mediated by Toll-like receptor 7 (TLR7) in the pDCs. Importantly, active viral RNA replication by the hepatocyte, not virus particle formation, is required to produce the pDC-activatIng signal, implying that a unique cell-cell RNA transfer mechanism could mediate this response. These unexpected observations help resolve the contradiction between the ability of HCV to induce type 1 IFN in the Infected liver and its ability to block type 1 interferon production by cells it infects. The host apparently avoids this viral evasion strategy via pDC sensing of the infected cells. To my knowledge, this is a novel aspect of the host response to viral infection that deserves to be characterized and more fully understood. In this application, therefore, we will define the cellular and molecular characteristics of this exciting new mechanism.
In Specific Aim 1. we will identify the molecular nature of the HCV-related signal that activates the pDC, focusing on the viral RNA as the likeliest candidate.
In Specific Aim 2, we will examine the cellular mechanisms whereby that signal is produced and how it is transferred to the pDC.
In Specific Aim 3, we will explore the extent to which this mechanism is operative in the chronically HCV infected liver.
Over 170 million people throughout the world are chronically Infected by HCV, 2-4 million of whom live in the United States. Twenty percent of these patients will develop cirrhosis of the liver and about 5% will die from liver failure and cancer. The work described in this proposal will improve our understanding of the host-virus interactions that regulate this infection with the hope that we will identify vulnerabilities in the HCV life cycle that can be exploited to develop safe and effective antiviral drugs to alleviate the human suffering and socioeconomic burden of this worldwide threat to public health.
|Wieland, Stefan; Makowska, Zuzanna; Campana, Benedetta et al. (2014) Simultaneous detection of hepatitis C virus and interferon stimulated gene expression in infected human liver. Hepatology 59:2121-30|
|McFarland, Adelle P; Horner, Stacy M; Jarret, Abigail et al. (2014) The favorable IFNL3 genotype escapes mRNA decay mediated by AU-rich elements and hepatitis C virus-induced microRNAs. Nat Immunol 15:72-9|
|Ireton, Reneé C; Gale Jr, Michael (2014) Pushing to a cure by harnessing innate immunity against hepatitis C virus. Antiviral Res 108:156-64|
|Wieland, S F; Takahashi, K; Boyd, B et al. (2014) Human plasmacytoid dendritic cells sense lymphocytic choriomeningitis virus-infected cells in vitro. J Virol 88:752-7|
|Brownell, Jessica; Bruckner, Jacob; Wagoner, Jessica et al. (2014) Direct, interferon-independent activation of the CXCL10 promoter by NF-*B and interferon regulatory factor 3 during hepatitis C virus infection. J Virol 88:1582-90|
|Horner, Stacy M; Gale Jr, Michael (2013) Regulation of hepatic innate immunity by hepatitis C virus. Nat Med 19:879-88|
|Ireton, Renee C; Gale Jr, Michael (2013) Systems biology analyses to define host responses to HCV infection and therapy. Curr Top Microbiol Immunol 363:143-67|
|Negash, Amina A; Ramos, Hilario J; Crochet, Nanette et al. (2013) IL-1? production through the NLRP3 inflammasome by hepatic macrophages links hepatitis C virus infection with liver inflammation and disease. PLoS Pathog 9:e1003330|
|Patel, Maulik R; Loo, Yueh-Ming; Horner, Stacy M et al. (2012) Convergent evolution of escape from hepaciviral antagonism in primates. PLoS Biol 10:e1001282|
|Loo, Yueh-Ming; Gale Jr, Michael (2011) Immune signaling by RIG-I-like receptors. Immunity 34:680-92|
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