Vaccinia virus subverts a mitochondrial antiviral signaling protein-dependent innate immune response in keratinocytes through its double-stranded RNA binding protein, E3.
Skin keratinocytes provide a first line of defense against invading microorganisms in two ways: (i) by acting as a physical barrier to pathogen entry and (ii) by initiating a vigorous innate immune response upon sensing danger signals. How keratinocytes detect virus infections and generate antiviral immune responses is not well understood. Orthopoxviruses are dermatotropic DNA viruses that cause lethal disease in humans. Virulence in animal models depends on the virus-encoded bifunctional Z-DNA/double-stranded RNA (dsRNA)-binding protein E3. Here, we report that infection of mouse primary keratinocytes with a vaccinia DeltaE3L mutant virus triggers the production of beta interferon (IFN-beta), interleukin-6 (IL-6), CCL4, and CCL5. None of these immune mediators is produced by keratinocytes infected with wild-type vaccinia virus. The dsRNA-binding domain of E3 suffices to prevent activation of the innate immune response. DeltaE3L induction of IFN-beta, IL-6, CCL4, and CCL5 secretion requires mitochondrial antiviral signaling protein (MAVS; an adaptor for the cytoplasmic viral RNA sensors RIG-I and MDA5) and the transcription factor IRF3. IRF3 phosphorylation is induced in keratinocytes infected with DeltaE3L, an event that depends on MAVS. The response of keratinocytes to DeltaE3L is unaffected by genetic ablation of Toll-like receptor 3 (TLR3), TRIF, TLR9, and MyD88.
Deng
Liang
L
Department of Medicine, Dermatology Service, Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA. dengl@mskcc.org
Dai
Peihong
P
Parikh
Tanvi
T
Cao
Hua
H
Bhoj
Vijay
V
Sun
Qinmiao
Q
Chen
Zhijian
Z
Merghoub
Taha
T
Houghton
Alan
A
Shuman
Stewart
S
D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D006224:Cricetinae; D016207:Cytokines / Q000378:metabolism; D005260:Female; D017353:Gene Deletion; D006801:Humans; D015603:Keratinocytes / Q000821:virology*; D051379:Mice; D008807:Mice, Inbred BALB C; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000235:genetics / Q000276:immunology* / Q000502:physiology*; D011817:Rabbits; D014616:Vaccinia virus / Q000276:immunology* / Q000502:physiology*; D014764:Viral Proteins / Q000235:genetics / Q000276:immunology* / Q000502:physiology*
D016207:Cytokines; C081374:E3L protein, Vaccinia virus; D016601:RNA-Binding Proteins; D014764:Viral Proteins