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CDLD Research Project 2

Dissection of Type-III Interferon Signaling in iPSC-Derived Hepatocytes

 

Eric Meissner M.D. Ph.D.: Department of Medicine

While hepatitis C virus (HCV) infection is now readily curable with antivirals, other viral infections affecting the liver, such as hepatitis B (HBV) and human immunodeficiency virus (HIV), are not and available treatments are suppressive and lifelong. Type-III interferons (IFNs), also called lambda IFNs (IFNLs), are key modulators of innate immunity at mucosal and epithelial surfaces. Single-nucleotide polymorphisms (SNPs) at IFNL loci are strongly associated with the odds of spontaneous HCV clearance during acute infection and the likelihood of cure upon treatment of chronic infection. Insight gained from studies of HCV has prompted clinical trials of IFNL for treatment of HCV, HBV, and hepatitis D (HDV) virus infections, in which they have shown promise. Although IFNL signaling pathways share multiple signaling proteins with type-I IFNs (continual signaling through which may facilitate hepatic inflammation and viral persistence) our mechanistic understanding of how these pathways intersect and communicate in the clinical context is incomplete. Given the interest in therapeutic modulation of IFN signaling for the treatment of chronic viral infections of the liver, it is essential to further our understanding of the protective, pathologic, and relational roles of IFNs.

The objective of this study is to expand our mechanistic insight into type-I and type-III IFN interaction and cross-regulation using HCV as a model, paving the way for future development of therapies targeting broad categories of chronic viral infections (e.g. HCV, HBV, and HIV) through the modulation of IFNL signaling. Using both clinical samples and in vitro models, we have extensively evaluated the role of IFNLs in HCV infection. We showed that hepatic IFNL expression correlates with inflammation during acute and chronic HCV infection. Moreover, expression of IFNL and its receptor, IFNLR1, were downregulated during antiviral suppression of HCV in a manner that parallels the changes in innate and adaptive immunity that are correlated with treatment outcome. Interestingly, in this same study, expression of the type-I IFN gene, IFNA2, was increased in patients who achieved cure. Based on these strong preliminary data, we believe that type-III IFNL signaling dampens the host type-I IFN response through the induction of negative regulators of IFN signaling. While receptor-ligand interactions are known to control type-I signaling efficiency, the impact of IFNLR1 isoform expression on IFNL signaling and the hepatic IFN response has not been explored. Furthermore, a dinucleotide polymorphism at the rs368234815 locus imparts the differential capacity to produce the IFNL4 ligand, the presence of which correlates with worse HCV clinical outcomes. Therefore, we hypothesize that 1) the relative expression of canonical and non-canonical isoforms of IFNLR1 and 2) the expression of IFNL4, tightly regulate IFN signaling in a manner that impacts the cellular response to hepatotropic viral infections.
Meissner Lab Webpage

Our ability to address these hypotheses has thus far been limited by the correlative nature of data generated from clinical samples. Furthermore, hepatoma cell lines and primary human hepatocytes (PHH) have intrinsic limitations that limit their suitability for studies designed to dissect the host response to infection. To overcome these limitations, we will use inducible pluripotent stem cell (iPSC) derived hepatocytes, or iHeps, as a model system. iHeps can be genetically manipulated, cultured long-term, support HCV and HBV infection, and have intact IFN-signaling pathways. Thus, they are extremely well-suited for our proposed study of the host response to hepatotropic viral infections.