Poster Presentation Lorne Infection and Immunity 2019

Interferon epsilon (IFNε) is a unique type I interferon: defining its biochemical similarities and functional differences (#118)

Nicole A De Weerd 1 , Sebastian A Stifter 2 , Antony Y Matthews 1 , Niamh E Mangan 1 , Michelle D Tate 1 , Tatiana P Soares da Costa 3 , Ka Yee Fung 1 , Daniel Hampsey 4 , Jemma Mayall 4 , Phil Hansbro 4 , Albert Garcia-Minabres 5 , Sahar Eid 5 , Johnson Mak 6 , Judith Scoble 7 , George Lovrecz 8 , Paul J Hertzog 1
  1. Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, , Clayton, Victoria, Australia
  2. The Centenary Institute, Camperdown, NSW, Australia
  3. LaTrobe Institute for Molecular Sciences, Bundoora, VIC, Australia
  4. Hunter Medical Research Institute, Newcastle, NSW
  5. Deakin University, Geelong, VIC, Australia
  6. CSIRO Australian Animal Health Laboratory, Geelong, VIC, Australia
  7. CSIRO Manufacturing, Parkville, VIC, Australia
  8. CSIRO Manufacturing, Parkville, VIC, Australia

The type I interferons (IFNs) are a family of cytokines with diverse biological activities including antiviral, antiproliferative, and immunoregulatory functions. Discovery of the hormonally-regulated IFNε, which is constitutively expressed in the female reproductive tract, suggested a role for IFNs in both homeostasis and protection from infection at this unique site; however the intrinsic properties of IFNε were yet to be determined.

We generated a recombinant form of murine (m)IFNε and report here its biochemical properties and functional characteristics. Using Circular Dichroism spectroscopy and Microscale Thermophoresis, we showed that mIFNε exhibited an α-helical fold characteristic of other type I IFNs and had measurable affinity for the extracellular domains (ECD) of murine IFN alpha/beta receptor (IFNAR)1 and IFNAR2-ECD, albeit with a preference for IFNAR1-ECD. Recombinant mIFNε also induced typical type I IFN signaling activities, including STAT1 phosphorylation and activation of canonical type I IFN signaling reporters, demonstrating that it utilizes the canonical JAK/STAT signaling pathway. We also found that, similar to other type I IFNs, mIFNε exhibited antiviral, antiproliferative, and antibacterial activities in cell-based assays, albeit with 100- to 1000-fold reduced potency compared with mIFNα1 and mIFNβ. mIFNε was also demonstrated by flow cytometry to upregulate a lymphocyte activation marker (CD69) on T, B, and NK cells, again at reduced efficacy compared to mIFNα1 and mIFNβ. Surprisingly, although type I IFNs generally do not display cross-species activities, mIFNε is unique in this regard, exhibiting antiviral activity on human cells, suppressing HIV replication and inducing the expression of known HIV-restriction factors in primary human lymphocytes.

Our findings define the intrinsic properties of mIFNε, indicating that it distinctly interacts with IFNAR and elicits pathogen-suppressing activity with a potency enabling host defense, but with limited toxicity, appropriate for a protein expressed constitutively in a sensitive mucosal site such as the reproductive tract.