Exchange of P/V genes between two non-cytopathic simian virus 5 variants results in a recombinant virus that kills cells through death pathways that are sensitive to caspase inhibitors

Abstract

Short CommunicationExchange of P/V genes between two noncytopathic simian virus 5 variants results in a recombinant virus that kills cells through death pathways that are sensitive to caspase inhibitors The paramyxovirus Simian virus 5 (SV5) is largely non-cytopathic in human epithelial and fibroblast cells. WF-PIV has been described previously as a naturally occurring SV5 variant that encodes P and V proteins differing from the wild-type (WT) SV5 proteins in eight and five amino acid positions, respectively. In this study, it is shown that WF-PIV is like WT SV5 by being largely non-cytopathic in A549 lung epithelial cells. However, substitution of the WF-PIV P/V gene into the background of WT SV5 resulted in a hybrid virus (P/V-WF) that induced apoptotic cell death not seen with either of the parental viruses. The kinetics of HeLa cell killing and induction of apoptosis by the P/V-WF chimera differed from those of the previously described P/V-CPI" chimera by being slower and less extensive. HeLa cell killing by the P/V-WF chimera was effectively reduced by inhibitors of caspase-9, but not of caspase-8. These results demonstrate that an exchange of P/V genes from two non-cytopathic SV5 variants can produce apoptosis-inducing chimeras, and that the role of the SV5 P/V gene products in limiting apoptosis can be dependent on expression in the context of a native viral genome.

Role for the Paramyxovirus Genomic Promoter in Limiting Host Cell Antiviral Responses and Cell Killing

“…Exchanging the P/V gene from WF-PIV or a second variant, CPI-, into an otherwise WT SV5 background results in a chimeric virus that overexpresses viral gene products and activates cytokine secretion and apoptosis (10,46,50). These results illustrate that chimeras can have phenotypes that are very different from those of the two parental viruses (10) and suggest that the trans-acting paramyxovirus gene products function in concert to coordinate viral gene expression and limit host cell responses. Here we show that the sequence of the WF-PIV genomic promoter differs substantially from that of WT SV5 in a key regulatory domain, and we analyze the consequences of variability in these cis-acting sequences for gene expression and antiviral responses.…”

“…Sequence analysis has identified many nucleotide differences between WF-PIV and WT SV5 (50). Exchanging the P/V gene from WF-PIV or a second variant, CPI-, into an otherwise WT SV5 background results in a chimeric virus that overexpresses viral gene products and activates cytokine secretion and apoptosis (10,46,50). These results illustrate that chimeras can have phenotypes that are very different from those of the two parental viruses (10) and suggest that the trans-acting paramyxovirus gene products function in concert to coordinate viral gene expression and limit host cell responses.…”

A Hyperfusogenic F Protein Enhances the Oncolytic Potency of a Paramyxovirus Simian Virus 5 P/V Mutant without Compromising Sensitivity to Type I Interferon

“…First, SV5 P/V gene mutants have been shown to induce apoptosis in a wide range of human tumor cell lines (11,54), but virus spread in primary normal human prostate epithelial cells is highly restricted (53). While we have not determined virus titers in tumors infected with the P/V mutants, we were able to detect viral antigen by immunohistochemistry in LNCaP tumors at the time of harvest (data not shown).…”

“…An SV5 mutant with substitutions in the shared region of the canine parainfluenza virus P/V genes (P/V-CPI Ϫ ) (Fig. 1A) overexpresses viral RNA and protein, is a potent inducer of IFN-␤ and proinflammatory cytokines, cannot block IFN signaling, and induces cell death (11,54). Here, we have tested the oncolytic potential of this P/V-CPI Ϫ mutant in human prostate cancer cells.…”

“…By comparison, SV5 has the unusual property among paramyxoviruses of being largely noncytopathic in most epithelial and fibroblast cell types (39,49) and thus would not be expected to have inherent oncolytic properties. Noncytopathic wild-type (WT) SV5 can be converted into a virus that induces apoptosis by engineered substitutions in the viral P/V gene (11,54). The SV5 P/V gene encodes the phosphoprotein P and the accessory protein V (31), which share an identical 164-residue amino-terminal domain (the shared P/V region) but have unique C-terminal domains.…”