![]() Cover art by Falguni Gokhale Foreo et. al. Differential Activation of the Transcription Factor IRF1 Underlies the Distinct Immune Responses Elicited by Type I and Type III Interferons. Immunity 2019 https://doi.org/10.1016/j.immuni.2019.07.007 |
![]() In this study Adriana shows that type I IFNs, but not type III IFNs (IFNλ), promote inflammation at the site of infection. She finds that differential expression of proinflammatory genes results from selective induction of the transcription factor IRF1 by type I IFNs. Type III IFNs induce a tissue repair program, suggesting a division of labor that spans proinflammatory and tissue repair functions to promote protective immunity. A commentary by Casazza and Lazear discusses the implications of our work. |
Genome-wide association studies identified a strong association between polymorphisms near IFNL3 and clearance of HCV. In the first study, we reported the identification of a functional polymorphism (rs4803217) in the 3' untranslated region (UTR) of IFNL3 mRNA that dictated transcript stability. We found that this polymorphism influenced AU-rich element-mediated decay of IFNL3 mRNA, as well as the binding of HCV-induced microRNAs during infection. We show that HCV induces aberrant expression of two host microRNAs, miR-208b and miR-499a-5p, encoded by myosin genes in infected hepatocytes. These miRNAs, along with AMD, suppress IFNL2 and IFNL3 gene expression, to support viral persistence. Together, these destabilizing mechanisms mediated robust mRNA repression of the unfavorable IFNL3 polymorphism. This study was highlighted by Tian, Asselah, and Frankfurter Aligemeine Zeitung.
In the second study, we show myomiRs also dampen type I IFN signaling in HCV-infected hepatocytes by directly down-regulating expression of the type I IFN receptor chain, IFNAR1. Inhibition of these miRNAs by using miRNA inhibitors during HCV infection increased expression of IFNAR1. Additionally, inhibition rescued the antiviral response to exogenous type I IFN, as measured by a marked increase in IFN stimulated genes and a decrease in HCV load. Treatment of HCV-infected hepatocytes with type I IFN increased expression of myosins over HCV infection alone. Since these miRNAs can suppress IFNl2 and IFNL3, these data collectively define a novel cross-regulation between type I and III IFNs during HCV infection. Thus, we propose myomiR regulation of IFNL3 as a mechanism to explain why interferon lambda genotype associates with response to type I IFN-based therapies in HCV-infected patients. This study was highlighted at Science Signaling by Alexandra Mushegian. |