PLoS ONE (Jan 2015)

IFN-λ Inhibits MiR-122 Transcription through a Stat3-HNF4α Inflammatory Feedback Loop in an IFN-α Resistant HCV Cell Culture System.

  • Fatma Aboulnasr,
  • Sidhartha Hazari,
  • Satyam Nayak,
  • Partha K Chandra,
  • Rajesh Panigrahi,
  • Pauline Ferraris,
  • Srinivas Chava,
  • Ramazan Kurt,
  • Kyongsub Song,
  • Asha Dash,
  • Luis A Balart,
  • Robert F Garry,
  • Tong Wu,
  • Srikanta Dash

DOI
https://doi.org/10.1371/journal.pone.0141655
Journal volume & issue
Vol. 10, no. 12
p. e0141655

Abstract

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BACKGROUND:HCV replication in persistently infected cell culture remains resistant to IFN-α/RBV combination treatment, whereas IFN-λ1 induces viral clearance. The antiviral mechanisms by which IFN-λ1 induces sustained HCV clearance have not been determined. AIM:To investigate the mechanisms by which IFN-λ clears HCV replication in an HCV cell culture model. METHODS:IFN-α sensitive (S3-GFP) and resistant (R4-GFP) cells were treated with equivalent concentrations of either IFN-α or IFN-λ. The relative antiviral effects of IFN-α and IFN-λ1 were compared by measuring the HCV replication, quantification of HCV-GFP expression by flow cytometry, and viral RNA levels by real time RT-PCR. Activation of Jak-Stat signaling, interferon stimulated gene (ISG) expression, and miRNA-122 transcription in S3-GFP and R4-GFP cells were examined. RESULTS:We have shown that IFN-λ1 induces HCV clearance in IFN-α resistant and sensitive replicon cell lines in a dose dependent manner through Jak-Stat signaling, and induces STAT 1 and STAT 2 activation, ISRE-luciferase promoter activation and ISG expression. Stat 3 activation is also involved in IFN-λ1 induced antiviral activity in HCV cell culture. IFN-λ1 induced Stat 3 phosphorylation reduces the expression of hepatocyte nuclear factor 4 alpha (HNF4α) through miR-24 in R4-GFP cells. Reduced expression of HNF4α is associated with decreased expression of miR-122 resulting in an anti-HCV effect. Northern blot analysis confirms that IFN-λ1 reduces miR-122 levels in R4-GFP cells. Our results indicate that IFN-λ1 activates the Stat 3-HNF4α feedback inflammatory loop to inhibit miR-122 transcription in HCV cell culture. CONCLUSIONS:In addition to the classical Jak-Stat antiviral signaling pathway, IFN-λ1 inhibits HCV replication through the suppression of miRNA-122 transcription via an inflammatory Stat 3-HNF4α feedback loop. Inflammatory feedback circuits activated by IFNs during chronic inflammation expose non-responders to the risk of hepatocellular carcinoma.