IRF3-mediated pathogenicity in a murine model of human hepatitis A.

Lu Sun,Ryosuke Suzuki,Jason K Whitmire,Olga González-López,David R Mcgivern,Lucinda Hensley,Stanley M Lemon,Ganes C Sen,Asuka Hirai-Yuki,John M Cullen,Mami Matsuda,Ichiro Misumi,You Li,Carolyn B Coyne

doi:10.1371/journal.ppat.1009960

Abstract

HAV-infected Ifnar1-/- mice recapitulate many of the cardinal features of hepatitis A in humans, including serum alanine aminotransferase (ALT) elevation, hepatocellular apoptosis, and liver inflammation. Previous studies implicate MAVS-IRF3 signaling in pathogenesis, but leave unresolved the role of IRF3-mediated transcription versus the non-transcriptional, pro-apoptotic activity of ubiquitylated IRF3. Here, we compare the intrahepatic transcriptomes of infected versus naïve Mavs-/- and Ifnar1-/- mice using high-throughput sequencing, and identify IRF3-mediated transcriptional responses associated with hepatocyte apoptosis and liver inflammation. Infection was transcriptionally silent in Mavs-/- mice, in which HAV replicates robustly within the liver without inducing inflammation or hepatocellular apoptosis. By contrast, infection resulted in the upregulation of hundreds of genes in Ifnar1-/- mice that develop acute hepatitis closely modeling human disease. Upregulated genes included pattern recognition receptors, interferons, chemokines, cytokines and other interferon-stimulated genes. Compared with Ifnar1-/- mice, HAV-induced inflammation was markedly attenuated and there were few apoptotic hepatocytes in livers of infected Irf3S1/S1Ifnar1-/- mice in which IRF3 is transcriptionally-inactive due to alanine substitutions at Ser-388 and Ser-390. Although transcriptome profiling revealed remarkably similar sets of genes induced in Irf3S1/S1Ifnar1-/- and Ifnar1-/- mice, a subset of genes was differentially expressed in relation to the severity of the liver injury. Prominent among these were both type 1 and type III interferons and interferon-responsive genes associated previously with apoptosis, including multiple members of the ISG12 and 2’-5’ oligoadenylate synthetase families. Ifnl3 and Ifnl2 transcript abundance correlated strongly with disease severity, but mice with dual type 1 and type III interferon receptor deficiency remained fully susceptible to liver injury. Collectively, our data show that IRF3-mediated transcription is required for HAV-induced liver injury in mice and identify key IRF3-responsive genes associated with pathogenicity, providing a clear distinction from the transcription-independent role of IRF3 in liver injury following binge exposure to alcohol.

Highlights

Viral hepatitis is an important cause of human morbidity and mortality worldwide, the absence of tractable small animal models for hepatotropic human viruses has handicapped efforts to understand anti-viral immunity and inflammatory responses within the liver [1,2]
Hepatitis A is a common and potentially serious disease involving inflammation and liver cell death resulting from infection with the picornavirus, hepatitis A virus (HAV)
We show that the liver injury associated with HAV infection in these mice results from the induction of genes under transcriptional control of interferon regulatory factor 3 (IRF3)

Summary

Introduction

Viral hepatitis is an important cause of human morbidity and mortality worldwide, the absence of tractable small animal models for hepatotropic human viruses has handicapped efforts to understand anti-viral immunity and inflammatory responses within the liver [1,2]. That Ifnar1-/- mice lacking expression of the type I interferon (IFN) receptor are highly permissive for infection with hepatitis A virus (HAV), the causative agent of type A hepatitis in humans [3,4,5]. These mice experience an hepatotropic HAV infection associated with elevated levels of liver-specific enzymes in the serum, fecal shedding of virus through the biliary track, and mixed inflammatory cell infiltrates surrounding apoptotic infected hepatocytes in the liver. Consistent with the notion that hepatitis results from cell-intrinsic responses, prior depletion of CD4+ or CD8+ T cells, NK/ NK-T cells, or phagocytic macrophages has no impact on the development of hepatitis following intravenous challenge of Ifnar1-/- mice with HAV [3]

Methods

Results

Discussion

Conclusion