Viral inhibitors of the virus-induced IFN-α/β response loop: Viral gene products interfere with the type I IFN system at all levels. The following viral IFN antagonists are shown in clockwise order: NS1 of FLUAV (Garcia-Sastre, 2001, Garcia-Sastre et al., 1998, Talon et al., 2000a, Wang et al., 2000), NS1 of FLUBV (Dauber et al., 2004), E3L VV (Smith et al., 2001, Xiang et al., 2002), V of paramyxoviruses (Andrejeva et al., 2004), NS3/4A of HCV (Breiman et al., 2005, Foy et al., 2005), VP35 of EBOV (Basler et al., 2003), P of RV (Brzozka et al., 2005), P of BDV (Unterstab et al., 2005), V, W of Nipah virus (Park et al., 2003, Shaw et al., 2004), NS1/NS2 of RSV (Bossert et al., 2003, Spann et al., 2004, Valarcher et al., 2003), leader protein of TMEV (Delhaye et al., 2004, van Pesch et al., 2001), ML of THOV (Hagmaier, 2003 #89;Jennings, 2004 #233;Pichlmair, 2004 #247), NPro of CSFV (La Rocca et al., 2005, Ruggli et al., 2003, Ruggli et al., 2005), vIRF and ORF45 of HHV-8 (Burysek et al., 1999a, Burysek et al., 1999b, Li et al., 1998, Lubyova et al., 2004, Lubyova and Pitha, 2000, Zhu et al., 2002, Zimring et al., 1998), E6 of HPV16 (Ronco et al., 1998), BZLF-1 of EBV (Hahn et al., 2005), M of VSV (Ahmed et al., 2003, Yuan et al., 1998), 3CPro of PV (Clark et al., 1993, Yalamanchili et al., 1996), NSs of BUNV (Thomas et al., 2004, Weber et al., 2002), NSs of RVFV, (Billecocq et al., 2004, Bouloy et al., 2001, Le May et al., 2004), B18 and B8 of VV (Alcami et al., 2000, Symons et al., 1995), JEV, WNV (Guo et al., 2005, Lin et al., 2004), E6 of HPV18 (Li et al., 1999), core protein of HCV (Bode et al., 2003, Keskinen et al., 2002, Melen et al., 2004, Miller et al., 2004), HSV-1 (Yokota et al., 2004), NSs of RVFV (M. Bouloy, pers. communication), V, C, N of paramyxoviruses (Andrejeva et al., 2002, Didcock et al., 1999, Garcin et al., 2002, Garcin et al., 2004, Gotoh et al., 2003, Kato et al., 2001, Kubota et al., 2002, Palosaari et al., 2003, Parisien et al., 2001, Rodriguez et al., 2002, Rodriguez et al., 2003, Shaffer et al., 2003, Shaw et al., 2004, Takeuchi et al., 2001), NS4B of DHFV, WNV, and YFV (Jones et al., 2005, Munoz-Jordan et al., 2003, Munoz-Jordan et al., 2005), E1A AdV (Leonard and Sen, 1996, Look et al., 1998), NS5A and E2 of HCV (Gale et al., 1998, Taylor et al., 1999), EBER of EBV (Elia et al., 1996), VA of AdV (Kitajewski et al., 1986, Mathews and Shenk, 1991), K3L of VV (Davies et al., 1992). Not shown: Tat and TAR of HIV interfere with PKR activation (Gunnery et al., 1990, Roy et al., 1990). γ34.5 protein of HSV-1 reverts the translational block mediated by PKR (He et al., 1997). NS1 of influenza B virus targets the IFN-induced ubiquitin-like modifier ISG15, the significance of which remains to be established (Krug et al., 2003). The M27 gene product of mouse cytomegalovirus binds and down-regulates STAT-2 (Zimmermann et al., 2005). Unknown gene products of hepatitis A virus and SARS-coronavirus inhibit IRF-3 activation (Fensterl et al., 2005, Spiegel et al., 2005).