Enterovirus 71 Proteins 2A and 3D Antagonize the Antiviral Activity of Gamma Interferon via Signaling Attenuation.
Enterovirus 71 (EV71) infection causes severe mortality involving multiple possible mechanisms, including cytokine storm, brain stem encephalitis, and fulminant pulmonary edema. Gamma interferon (IFN-γ) may confer anti-EV71 activity; however, the claim that disease severity is highly correlated to an increase in IFN-γ is controversial and would indicate an immune escape initiated by EV71. This study, investigating the role of IFN-γ in EV71 infection using a murine model, showed that IFN-γ was elevated. Moreover, IFN-γ receptor-deficient mice showed higher mortality rates and more severe disease progression with slower viral clearance than wild-type mice. In vitro results showed that IFN-γ pretreatment reduced EV71 yield, whereas EV71 infection caused IFN-γ resistance with attenuated IFN-γ signaling in IFN regulatory factor 1 (IRF1) gene transactivation. To study the immunoediting ability of EV71 proteins in IFN-γ signaling, 11 viral proteins were stably expressed in cells without cytotoxicity; however, viral proteins 2A and 3D blocked IFN-γ-induced IRF1 transactivation following a loss of signal transducer and activator of transcription 1 (STAT1) nuclear translocation. Viral 3D attenuated IFN-γ signaling accompanied by a STAT1 decrease without interfering with IFN-γ receptor expression. Restoration of STAT1 or blocking 3D activity was able to rescue IFN-γ signaling. Interestingly, viral 2A attenuated IFN-γ signaling using another mechanism by reducing the serine phosphorylation of STAT1 following the inactivation of extracellular signal-regulated kinase without affecting STAT1 expression. These results demonstrate the anti-EV71 ability of IFN-γ and the immunoediting ability by EV71 2A and 3D, which attenuate IFN-γ signaling through different mechanisms.


OBJECTIVE
Immunosurveillance by gamma interferon (IFN-γ) may confer anti-enterovirus 71 (anti-EV71) activity; however, the claim that disease severity is highly correlated to an increase in IFN-γ is controversial and would indicate an immune escape initiated by EV71. IFN-γ receptor-deficient mice showed higher mortality and more severe disease progression, indicating the anti-EV71 property of IFN-γ. However, EV71 infection caused cellular insusceptibility in response to IFN-γ stimulation. We used an in vitro system with viral protein expression to explore the novel IFN-γ inhibitory properties of the EV71 2A and 3D proteins through the different mechanisms. According to this study, targeting either 2A or 3D pharmacologically and/or genetically may sustain a cellular susceptibility in response to IFN-γ, particularly for IFN-γ-mediated anti-EV71 activity.
Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Li-Chiu
LC
Wang
Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Su-O
SO
Chen
Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Shih-Ping
SP
Chang
Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Yi-Ping
YP
Lee
Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Chun-Keung
CK
Yu
Center for Translational Medicine, Taipei Medical University, Taipei, Taiwan.
Chia-Ling
CL
Chen
Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Po-Chun
PC
Tseng
Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Chia-Yuan
CY
Hsieh
Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan shunhua@mail.ncku.edu.tw cflin2014@tmu.edu.tw.
Shun-Hua
http://orcid.org/0000-0002-4585-9279
SH
Chen
Graduate Institute of Medical Sciences, Department of Microbiology and Immunology, College of Medicine, Taipei Medical University, Taipei, Taiwan shunhua@mail.ncku.edu.tw cflin2014@tmu.edu.tw.
Chiou-Feng
CF
Lin
D000818:Animals; D002460:Cell Line; D004195:Disease Models, Animal; D029821:Enterovirus A, Human / Q000276:immunology*; D004769:Enterovirus Infections / Q000276:immunology*; D054884:Host-Pathogen Interactions; D006801:Humans; D007371:Interferon-gamma / Q000037:antagonists & inhibitors*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015398:Signal Transduction; D014764:Viral Proteins / Q000378:metabolism*
D014764:Viral Proteins; D007371:Interferon-gamma