• Authors: Schwab LSU. et al.
  • Year: 2022
  • Journal: Viruses 14 1547
  • Applications: in vivo / 5'-PPP-dsRNA / in vivo-jetPEI


12.5 μg of 3pRNA or ctrl RNA was formulated in in vivo jetPEI transfection reagent (Polyplus-transfection, France) at a N/P ratio of 8 and intravenously injected. The N/P ratio is a measure of the ionic balance within the RNA complexes and is defined as the number of nitrogen residues of in vivo-jetPEI per nucleic acid phosphate. At the indicates timepoints, mice were infected with the indicated dose of IAV in 50 μL of PBS via the intranasal route.


RIG-I is an innate sensor of RNA virus infection and its activation induces interferon-stimulated genes (ISGs). In vitro studies using human cells have demonstrated the ability of synthetic RIG-I agonists (3pRNA) to inhibit IAV replication. However, in mouse models of IAV the effectiveness of 3pRNA reported to date differs markedly between studies. Myxoma resistance (Mx)1 is an ISG protein which mediates potent anti-IAV activity, however most inbred mouse strains do not express a functional Mx1. Herein, we utilised C57BL/6 mice that do (B6.A2G-Mx1) and do not (B6-WT) express functional Mx1 to assess the ability of prophylactic 3pRNA treatment to induce ISGs and to protect against subsequent IAV infection. In vitro, 3pRNA treatment of primary lung cells from B6-WT and B6.A2G-Mx1 mice resulted in ISG induction however inhibition of IAV infection was more potent in cells from B6.A2G-Mx1 mice. In vivo, a single intravenous injection of 3pRNA resulted in ISG induction in lungs of both B6-WT and B6.A2G-Mx1 mice, however potent and long-lasting protection against subsequent IAV challenge was only observed in B6.A2G-Mx1 mice. Thus, despite broad ISG induction, expression of a functional Mx1 is critical for potent and long-lasting RIG-I agonist-mediated protection in the mouse model of IAV infection.

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