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Inhibition of DAI-dependent necroptosis by the Z-DNA binding domain of the vaccinia virus innate immune evasion protein, E3.

ABSTRACT: Vaccinia virus (VACV) encodes an innate immune evasion protein, E3, which contains an N-terminal Z-nucleic acid binding (Z?) domain that is critical for pathogenicity in mice. Here we demonstrate that the N terminus of E3 is necessary to inhibit an IFN-primed virus-induced necroptosis. VACV deleted of the Z? domain of E3 (VACV-E3L?83N) induced rapid RIPK3-dependent cell death in IFN-treated L929 cells. Cell death was inhibited by the RIPK3 inhibitor, GSK872, and infection with this mutant virus led to phosphorylation and aggregation of MLKL, the executioner of necroptosis. In 293T cells, induction of necroptosis depended on expression of RIPK3 as well as the host-encoded Z? domain-containing DNA sensor, DAI. VACV-E3L?83N is attenuated in vivo, and pathogenicity was restored in either RIPK3- or DAI-deficient mice. These data demonstrate that the N terminus of the VACV E3 protein prevents DAI-mediated induction of necroptosis.

SUBMITTER: Koehler H

PROVIDER: S-EPMC5664489 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Inhibition of DAI-dependent necroptosis by the Z-DNA binding domain of the vaccinia virus innate immune evasion protein, E3.

Koehler Heather H Cotsmire Samantha S Langland Jeffrey J Kibler Karen V KV Kalman Daniel D Upton Jason W JW Mocarski Edward S ES Jacobs Bertram L BL

Proceedings of the National Academy of Sciences of the United States of America 20171009 43

Vaccinia virus (VACV) encodes an innate immune evasion protein, E3, which contains an N-terminal Z-nucleic acid binding (Zα) domain that is critical for pathogenicity in mice. Here we demonstrate that the N terminus of E3 is necessary to inhibit an IFN-primed virus-induced necroptosis. VACV deleted of the Zα domain of E3 (VACV-E3LΔ83N) induced rapid RIPK3-dependent cell death in IFN-treated L929 cells. Cell death was inhibited by the RIPK3 inhibitor, GSK872, and infection with this mutant virus ...[more]

PMID: 29073079

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Project description:Plasmacytoid dendritic cells (pDCs) play important roles in antiviral innate immunity by producing type I interferon (IFN). In this study, we assess the immune responses of primary human pDCs to two poxviruses, vaccinia and myxoma virus. Vaccinia, an orthopoxvirus, was used for immunization against smallpox, a contagious human disease with high mortality. Myxoma virus, a Leporipoxvirus, causes lethal disease in rabbits, but is non-pathogenic in humans. We report that myxoma virus infection of human pDCs induces IFN-? and TNF production, whereas vaccinia infection does not. Co-infection of pDCs with myxoma virus plus vaccinia blocks myxoma induction effects. We find that heat-inactivated vaccinia (Heat-VAC; by incubating the virus at 55°C for 1?h) gains the ability to induce IFN-? and TNF in primary human pDCs. Induction of IFN-? in pDCs by myxoma virus or Heat-VAC is blocked by chloroquine, which inhibits endosomal acidification required for TLR7/9 signaling, and by inhibitors of cellular kinases PI3K and Akt. Using purified pDCs from genetic knockout mice, we demonstrate that Heat-VAC-induced type I IFN production in pDCs requires the endosomal RNA sensor TLR7 and its adaptor MyD88, transcription factor IRF7 and the type I IFN feedback loop mediated by IFNAR1. These results indicate that (i) vaccinia virus, but not myxoma virus, expresses inhibitor(s) of the poxvirus sensing pathway(s) in pDCs; and (ii) Heat-VAC infection fails to produce inhibitor(s) but rather produces novel activator(s), likely viral RNA transcripts that are sensed by the TLR7/MyD88 pathway. Using vaccinia gene deletion mutants, we show that the Z-DNA/RNA binding domain at the N-terminus of the vaccinia immunomodulatory E3 protein is an antagonist of the innate immune response of human pDCs to poxvirus infection and TLR agonists. The myxoma virus ortholog of vaccinia E3 (M029) lacks the N-terminal Z-DNA/RNA binding domain, which might contribute to the immunostimulating properties of myxoma virus.

Dataset Information

Inhibition of DAI-dependent necroptosis by the Z-DNA binding domain of the vaccinia virus innate immune evasion protein, E3.

Publications

Inhibition of DAI-dependent necroptosis by the Z-DNA binding domain of the vaccinia virus innate immune evasion protein, E3.

Similar Datasets

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