An Antiviral Branch of the IL-1 Signaling Pathway Restricts Immune-Evasive Virus Replication

Abstract

Virulent pathogens often cause the release of host-derived damage-associated molecular patterns (DAMPs) from infected cells. During encounters with immune-evasive viruses that block inflammatory gene expression, preformed DAMPs provide backup inflammatory signals that ensure protective immunity. Whether DAMPs exhibit additional backup defense activities is unknown. Herein, we report that viral infection of barrier epithelia (keratinocytes) elicits the release of preformed interleukin-1 (IL-1) family cytokines, including the DAMP IL-1α. Mechanistic studies revealed that IL-1 acts on skin fibroblasts to induce an interferon (IFN)-like state that restricts viral replication. We identified a branch in the IL-1 signaling pathway that induces IFN-stimulated gene expression in infected cells and found that IL-1 signaling is necessary to restrict viral replication in human skin explants. These activities are most important to control immune-evasive virus replication in fibroblasts and other barrier cell types. These findings highlight IL-1 as an important backup antiviral system to ensure barrier defense. Keratinocytes are a barrier cell type that contribute to antiviral host defense. Orzalli et al. report that IL-1 cytokines released from infected keratinocytes induce antiviral responses in stromal cells. Mechanistic studies identified a genetic requirement for an IRF1-dependent signaling axis that regulates antiviral gene expression downstream of the IL-1R.