Single Amino Acid Substitution in the V Protein of Simian Virus 5 Differentiates Its Ability To Block Interferon Signaling in Human and Murine Cells

Abstract

(2,8,16,38), although they achieve this by distinct mechanisms (40). Thus, for example, we have shown that simian virus 5 (SV5) blocks IFN signaling by targeting STAT1, an essential component of IFN-␣/␤ and IFN-␥ signaling cascades, for proteasome-mediated degradation (3). However, the ability of SV5 to block IFN signaling is species dependent. Thus, wild-type (wt) SV5 blocks IFN signaling in human, monkey, and canine cells but fails to block IFN signaling in murine cells. Indeed, the ability to block IFN signaling in a particular species may be one factor that limits the host range of a given virus (2).SV5 is a prototype member of the Rubulavirus genus within the Paramyxoviridae family (19). Like other paramyxoviruses, SV5 has a nonsegmented, negative-sense, single-stranded RNA genome. Its genome is encapsidated within a helical nucleocapsid which is surrounded by a pleomorphic, lipid-containing envelope containing the HN and F virus glycoproteins. (For a review of the Paramyxoviridae, see reference 17.) Over the last few years, techniques have been developed to manipulate the genomes of many Paramyxoviridae, including SV5 (11,12,24,27). Thus, it is now possible to manipulate the genome of SV5 and to correlate genotypes with phenotypes. We report here that a single amino acid substitution in the V protein confers on SV5 the ability to block IFN signaling in murine cells, and we demonstrate protracted virus protein synthesis in murine cells infected with a recombinant virus which blocks IFN signaling in these cells compared to cells infected with wt virus. MATERIALS AND METHODSCells, viruses, and IFN. Murine BF cells (cloned from a primary cell culture of a BALB/c mouse embryo) and human 2fTGH cells (22) were grown as monolayers in 25-or 75-cm 2 tissue culture flasks in Dulbecco modified Eagle medium (DMEM) supplemented with 10% fetal bovine serum (growth medium). Monolayer cultures of A549, BHK-21, MDBK, and CV-1 cells were maintained in DMEM and 10% fetal calf serum as described previously (26). Chick embryo fibroblasts (CEFs) were grown as described previously (18). All cell lines were negative for mycoplasmas as screened by DAPI (4Ј,6Ј-diamidino-2-phenylindole) staining. Human and mouse cells were treated with recombinant human ␣A/D (rHuIFN-␣A/D) IFN (31) at 1,000 IU/ml in medium containing 2% bovine serum (maintenance medium). The wt (strain W3A) (1), rSV5-V/P N 100 D, and SV5 mci-2 strains of SV5 were grown and titrated under appropriate conditions in Vero cells using maintenance medium. High-multiplicity infections

Paramyxovirus evasion of innate immunity: Diverse strategies for common targets

“…Importantly, IFN antagonism has been implicated as a key factor in host and tissue specificity, with PIV5 showing limited host range dependent on the capacity of the V protein to bind to STAT2 from different species [129][130][131][132] , whereas NiV V blocks IFN signalling in cells of many species, consistent with its broad infectious range [82,110,124,126] . Tissue-specific antagonism of IFN has also been reported for NiV, which induces an IFN response in endothelial but not neuronal cells, correlating with differential subcellular localisation of NiV W [133] .…”

Identification of the Nuclear Export Signal and STAT-Binding Domains of the Nipah Virus V Protein Reveals Mechanisms Underlying Interferon Evasion

“…As an IFN response modifier, the V protein is a virulence and pathogenesis-determining factor. In the case of SV5, species-specific restriction of STAT1 degradation has been shown to be a determinant of host species tropism, restricting SV5 replication in IFN-competent murine cells (20,31).…”

“…As an IFN response modifier, the V protein is a virulence and pathogenesis-determining factor. In the case of SV5, species-specific restriction of STAT1 degradation has been shown to be a determinant of host species tropism, restricting SV5 replication in IFN-competent murine cells (20,31).A new genus of recently emerged paramyxoviruses, Henipavirus, was demonstrated to share V-dependent IFN signaling evasion properties with other paramyxoviruses (21,24,25). Encoded by a polycistronic gene, the 405-amino-acid V protein N terminus is shared with the co-amino-terminal P and W proteins (3).…”

The V proteins of paramyxoviruses bind the IFN-inducible RNA helicase, mda-5, and inhibit its activation of the IFN -β promoter

“…Furthermore, ectopic expression of SV5 V inhibits the activation of IRF-3 and NF-B by both dsRNA and infection with SV5V⌬C (10,11). Unlike the targeted degradation of signal transducer and activator of transcription 1 (STAT1), which requires both the N-and C-terminal domains of V (14,15), only the cysteine-rich C-terminal domain of V is required to inhibit dsRNA activation of the IFN-␤ promoter (11).…”