Importance of the cysteine-rich carboxyl-terminal half of V protein for Sendai virus pathogenesis

Abstract

The Sendai virus V protein is a nonstructural trans-frame protein whose cysteine-rich C-terminal half is fused to the acidic N-terminal half of the P protein via mRNA editing. We recently created a mutant by disrupting the editing motif, which is devoid of mRNA editing and hence unable to produce the V protein, and demonstrated that this V(؊) virus replicated normally or even faster with augmented gene expression and cytopathogenicity in cells in vitro, but was strongly attenuated in pathogenicity for mice (A. Kato, K. Kiyotani, Y. Sakai, T. Yoshida, and Y. Nagai, EMBO J. 16:578-587, 1997). Thus, although categorized as a nonessential protein, the V protein appeared to encode a luxury function required for the viral in vivo pathogenesis. Here, we created another version of a V-deficient mutant, V ⌬C , encoding only the N-terminal half but not the V-specific C-terminal half, by introducing a stop codon in the trans-V frame, and then we compared its in vitro and in vivo phenotypes with those of the V(؊) and wild-type viruses. The V ⌬C virus was found to be similar to the wild-type virus in vitro with no augmented gene expression and cytopathogenicity, but in vivo, it resembled the V(؊) virus, displaying a similarly attenuated phenotype. Thus, the pathogenicity determinant in the V protein was mapped to the C-terminal half. The N-terminal half was likely sufficient to confer normal (wildtype) in vitro phenotypes.

Human parainfluenza virus type 2 V protein inhibits interferon production and signaling and is required for replication in non-human primates

“…Similarly, V protein defective canine distemper virus was restricted 50-to 100-fold in replication in ferrets (von Messling et al, 2006). SeV V mutants that replicated efficiently in vitro were significantly attenuated in mice with a shorter duration of replication and approximately 10-fold lower peak titers than WT SeV (Kato et al, 1997a(Kato et al, , 1997b. The greater restriction of rHPIV2-V ko in vivo than morbillivirus or SeV V mutants perhaps is due to V's role as the sole IFN antagonist in HPIV2, whereas measles and SeV have both V and C proteins contributing to IFN antagonism.…”

Paramyxovirus Accessory Proteins as Interferon Antagonists

“…Recombinant SeV, which does not express the accessory protein, C or V protein, was created without affecting other viral amino acid sequences (58,59,67). Successful isolation of these knockout viruses from a mutat-ed full-length genome cDNA demonstrates that the C and V proteins are dispensable and essentially accessory for virus replication.…”

Sendai virus C proteins are categorically nonessential gene products but silencing their expression severely impairs viral replication and pathogenesis

“…Although categorized as a nonessential gene product completely dispensable for viral replication in cells in culture, the V protein was essential for the maintenance of a high viral load in mice, the natural host, and manifest pathogenicity characterized by severe pneumonia (Kato et al 1997a). Furthermore, this 'luxury' function has been primarily mapped to the unique cysteine-rich carboxyl-terminal half (Kato et al 1997b).…”