Stack, J. et al. Vaccinia virus protein A46R targets multiple Toll-like-interleukin-1 receptor adaptors and contributes to virulence. J. Exp. Med. 201, 1007-1018

Department of Biochemistry, Trinity College, Dublin 2, Ireland.
Journal of Experimental Medicine (Impact Factor: 12.52). 04/2005; 201(6):1007-18. DOI: 10.1084/jem.20041442
Source: PubMed


Viral immune evasion strategies target key aspects of the host antiviral response. Recently, it has been recognized that Toll-like receptors (TLRs) have a role in innate defense against viruses. Here, we define the function of the vaccinia virus (VV) protein A46R and show it inhibits intracellular signalling by a range of TLRs. TLR signalling is triggered by homotypic interactions between the Toll-like-interleukin-1 resistance (TIR) domains of the receptors and adaptor molecules. A46R contains a TIR domain and is the only viral TIR domain-containing protein identified to date. We demonstrate that A46R targets the host TIR adaptors myeloid differentiation factor 88 (MyD88), MyD88 adaptor-like, TIR domain-containing adaptor inducing IFN-beta (TRIF), and the TRIF-related adaptor molecule and thereby interferes with downstream activation of mitogen-activated protein kinases and nuclear factor kappaB. TRIF mediates activation of interferon (IFN) regulatory factor 3 (IRF3) and induction of IFN-beta by TLR3 and TLR4 and suppresses VV replication in macrophages. Here, A46R disrupted TRIF-induced IRF3 activation and induction of the TRIF-dependent gene regulated on activation, normal T cell expressed and secreted. Furthermore, we show that A46R is functionally distinct from another described VV TLR inhibitor, A52R. Importantly, VV lacking the A46R gene was attenuated in a murine intranasal model, demonstrating the importance of A46R for VV virulence.

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    • "Reserve (VACV) and VACV-A5L-EGFP (Carter et al., 2003) were used in this work. The anti-A46 antibody was a kind gift from Andrew Bowie (Stack et al., 2005), the anti-D8 antibody a kind gift from Geoffrey Smith (Parkinson and Smith, 1994). Other antibodies used were anti-RAB1A (ab97956, Abcam), anti-GM130 (610822, BD Pharmingen ), and anti-B5 (NR-556, BeiResources). "
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    • "Activation of the NFκB pathway through the IL-1R is prevented by A52R, A46R, and K7L (Bowie et al., 2000; Schroder et al., 2008). A46R binds the TIR-domain containing adapter proteins MyD88, TRIF, TIRAP, and TRAM, and prevents them from associating with the IL-1R (Bowie et al., 2000; Stack et al., 2005). A52R and K7 bind TRAF6 and IRAK2 to disrupt signaling complexes containing these proteins (Bowie et al., 2000; Graham et al., 2008; Harte et al., 2003; Schroder et al., 2008). "
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    • "Detection of TRAF2, p84, A46, and D8 was carried out using direct infrared fluorescence (Li-Cor). Blots were treated with Odyssey blocking buffer (Li-Cor) before incubation with A46 (53), D8 (54), TRAF2 (Santa Cruz), p84 (GeneTex), or β-actin (AbCam) antibodies. Goat anti-rabbit IgG (H+L) DyLight 800 conjugate (Cell Signaling) and goat anti-mouse IgG (H+L) DyLight 680 conjugate (Cell Signaling) were used as secondary antibodies. "
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