Anti-IFNL2 monoclonal antibody, clone 359623

IFNL4 is linked to hepatitis C virus treatment response and type III interferons (IFNs). We studied the functional associations among hepatic expressions of IFNs and IFN-stimulated genes (ISGs), and treatment response to peginterferon and ribavirin. Type I IFNs (IFNA1, IFNB1), type II (IFNG), type III (IFNL1, IFNL2/3), IFNL4 and ISG hepatic expressions were measured by qPCR from in 65 chronic hepatitis C (CHC) patients whose IFNL4-associated rs368234815 and IFNL3-associated rs12989760 genotype were determined. There was a robust correlation of hepatic expression within type I and type III IFNs and between type III IFNs and IFNL4 but no correlation between other IFN types. Expression of ISGs correlated with type III IFNs and IFNL4 but not with type I IFNs. Levels of ISGs and IFNL2/3 mRNAs were lower in IFNL3 rs12979860 CC patients compared with non-CC patients, and in treatment responders, compared with nonresponders. IFNL4-Delta G genotype was associated with high ISG levels and nonresponse. Hepatic levels of ISGs in CHC are associated with IFNL2/3 and IFNL4 expression, suggesting that IFNLs, not other types of IFNs, drive ISG expression. Hepatic IFNL2/3 expression is functionally linked to IFNL4 and IFNL3 polymorphisms, potentially explaining the tight association among ISG expression and treatment response.

Type III interferon (IFN), or IFN lambda (IFN-lambda), is an essential component of the innate immune response to mucosal viral infections. In both the intestine and the lung, signaling via the IFN-lambda receptor (IFNLR) controls clinically important viral pathogens, including influenza virus, norovirus, and rotavirus. While it is thought that IFN-lambda cytokines are the exclusive ligands for signaling through IFNLR, it is not known whether genetic ablation of these cytokines phenotypically recapitulates disruption of the receptor. Here, we report the serendipitous establishment of Ifnl2(-/-) Ifnl3(-/-) mice, which lack all known functional murine IFN-lambda cytokines. We demonstrate that, like Ifnlr1(-/-) mice lacking IFNLR signaling, these mice display defective control of murine norovirus, reovirus, and influenza virus and therefore genocopy Ifnlr1(-/-) mice. Thus, for regulation of viral infections at mucosal sites of both the intestine and lung, signaling via IFNLR can be fully explained by the activity of known cytokines IFN-lambda 2 and IFN-lambda 3. Our results confirm the current understanding of ligand-receptor interactions for type III IFN signaling and highlight the importance of this pathway in regulation of mucosal viral pathogens. IMPORTANCE Type III interferons are potent antiviral cytokines important for regulation of viruses that infect at mucosal surfaces. Studies using mice lacking the Ifnlr1 gene encoding the type III interferon receptor have demonstrated that signaling through this receptor is critical for protection against influenza virus, norovirus, and reovirus. Using a genetic approach to disrupt murine type III interferon cytokine genes Ifnl2 and Ifnl3, we found that mice lacking these cytokines fully recapitulate the impaired control of viruses observed in mice lacking Ifnlr1. Our results support the idea of an exclusive role for known type III interferon cytokines in signaling via IFNLR to mediate antiviral effects at mucosal surfaces. These findings emphasize the importance of type III interferons in regulation of a variety of viral pathogens and provide important genetic evidence to support our understanding of the ligand-receptor interactions in this pathway.