Function of the Respiratory Syncytial Virus Small Hydrophobic Protein

Abstract

Respiratory syncytial virus (RSV), a member of the Paramyxoviridae family, encodes a small hydrophobic (SH) protein of unknown function. Parainfluenza virus 5 (PIV5), a prototypical paramyxovirus, also encodes an SH protein, which inhibits tumor necrosis factor alpha (TNF-␣) signaling. In this study, recombinant PIV5 viruses without their own SH but containing RSV SH (from RSV strain A2 or B1) in its place (PIV5⌬SH-RSV SH) and RSV lacking its own SH (RSV⌬SH) were generated and analyzed. The results indicate that the SH protein of RSV has a function similar to that of PIV5 SH and that it can inhibit TNF-␣ signaling.Human respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in infants and young children (17). RSV, along with the prototype paramyxovirus parainfluenza virus 5 (PIV5; formerly known as simian virus 5), is a member of the Paramyxoviridae family, which includes important human and animal pathogens. Both RSV and PIV5 encode small hydrophobic (SH) proteins, which are type II transmembrane proteins. The SH protein of RSV contains 64 (RSV subgroup A) or 65 (RSV subgroup B) amino acid residues (Fig. 1A) (3)(4)(5)14). Some studies have suggested that the RSV SH protein may have a role in viral fusion (9, 19) or in changing membrane permeability (15). However, RSV lacking the SH gene (RSV⌬SH) is viable, causes syncytium formation, and grows as well as the wild-type virus (1, 10, 11), indicating that the SH protein is not necessary for virus entry into host cells or syncytium formation (19). RSV⌬SH is attenuated in animals, indicating that RSV plays an important role in viral pathogenesis (1). Interestingly, recombinant PIV5 lacking the SH gene (rPIV5⌬SH) has a similar phenotype: it has normal growth in vitro, but it is attenuated in vivo (7). Studies of rPIV5⌬SH have shown that the SH protein is necessary for the inhibition of tumor necrosis factor alpha (TNF-␣)-induced apoptosis in L929 cells (12). Recent work suggests that the SH protein of mumps virus is a functional counterpart of the PIV5 SH protein (22), even though the PIV5 and mumps SH proteins have no sequence homology. We hypothesized that the SH protein of RSV may be functionally similar to other SH proteins from members of the Paramyxoviridae family. To test this hypothesis, recombinant viruses that contained the RSV SH gene of strain A2 or B1 in place of the PIV5 SH gene were produced and confirmed by reverse transcription (RT)-PCR (Fig. 1B). The rPIV5 and rPIV5⌬SH viruses grow to similar titers, although rPIV5⌬SH virus grows slightly faster in the first stages of infection (Fig. 1C) (6, 22). Growth of the rPIV5⌬SH-RSV SH recombinant viruses was comparable to that of rPIV5 and rPIV5⌬SH up to 2 days postinfection (dpi). Occasionally, a delay in the growth of one or both of the recombinant viruses was observed, but by 24 or 36 h the viruses had always reached titers comparable to that of the wild-type virus (Fig. 1C). The plaques formed by the rPIV5, rPIV5⌬SH, and rPIV5⌬SH-RSV SH viruses in BHK cells were of a...

Viroporins: structure, function and potential as antiviral targets

“…SH-deleted RSV shows 10-and 40-fold reductions in replication in small animal and chimpanzee models, respectively (Bukreyev et al, 1997;Whitehead et al, 1999). SH has been proposed to antagonize TNF-a-mediated apoptosis (Fuentes et al, 2007;Lin et al, 2003), but recent reports also point to a role during HMPV entry, where it modulates both virion membrane permeability and the activity of the viral F (fusion) protein (Masante et al, 2014).…”

Aberrant T cell immunity triggered by human Respiratory Syncytial Virus and human Metapneumovirus infection

“…118 This protein also inhibits apoptosis in order to promote viral replication, as recombinant hRSV lacking the SH protein induced a significant cytopathic effect in different cell lines, compare with WT hRSV. 119 In addition, the hRSV SH has been shown to inhibit the NF-kb pathway through a decrease in the TNF-a production in mouse fibroblastic cells. 119 Another studies have demonstrated that glycoproteins affect the innate and adaptive immune response to hRSV.…”

“…119 In addition, the hRSV SH has been shown to inhibit the NF-kb pathway through a decrease in the TNF-a production in mouse fibroblastic cells. 119 Another studies have demonstrated that glycoproteins affect the innate and adaptive immune response to hRSV. In this study, immunization of BALB/c mice with a recombinant strain of hRSV lacking both G and SH (CP52) increased the number of pulmonary natural killer (NK) cells, as well as the levels of IFN-g and TNF-a at day 3 p.i.…”

Surface features of a Mononegavirales matrix protein indicate sites of membrane interaction

“…Morphologically, the extracellular virion consists of a lipid bilayer envelope, within which are embedded 3 glycoproteins, 2 of which (F and G) are important in cell attachment and viral entry into target cells. The third, the SH protein, contributes to pathology in the host (1). Internally, virions contain helical nucleocapsids that consist of N protein tightly bound to the negative-sense nonsegmented genomic RNA.…”