title: Selective ablation of virion host shutoff protein RNase activity attenuates herpes simplex virus 2 in mice.
abstract: The virion host shutoff (vhs) protein of herpes simplex virus (HSV) has endoribonuclease activity and rapidly reduces protein synthesis in infected cells through mRNA degradation. Herpes simplex virus 1 (HSV-1) and HSV-2 vhs mutants are highly attenuated in vivo, but replication and virulence are largely restored to HSV-2 vhs mutants in the absence of a type I interferon (IFN) response. The role of vhs in pathogenesis and the hindrance of the type I IFN response have classically been examined with viruses that completely lack vhs or express a truncated vhs protein. To determine whether RNase activity is the principal mechanism of vhs-mediated type I IFN resistance and virulence, we constructed a HSV-2 point mutant that synthesizes full-length vhs protein lacking RNase activity (RNase(-) virus). Wild-type and mutant HSV-2 vhs proteins coimmunoprecipitated with VP16 and VP22. vhs protein bearing the point mutation was packaged into the virion as efficiently as the wild-type vhs protein. Like a mutant encoding truncated vhs, the RNase(-) virus showed IFN-dependent replication that was restricted compared with that of the wild-type virus. The RNase(-) virus was highly attenuated in wild-type mice infected intravaginally, with reduced mucosal replication, disease severity, and spread to the nervous system comparable to those of the vhs truncation mutant. Surprisingly, in alpha/beta interferon (IFN-alpha/beta) receptor knockout mice, the vhs RNase mutant was more attenuated than the vhs truncation mutant in terms of disease severity and virus titer in vaginal swabs and central nervous system samples, suggesting that non-enzymatically active vhs protein interferes with efficient virus replication. Our results indicate that vhs enzymatic activity plays a complex role in vhs-mediated type I IFN resistance during HSV-2 infection.
authors.affiliation: Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, 1100 S. Grand Blvd., St. Louis, Missouri 63104, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Korom
authors.forename: Kristine M
authors.initials: KM
authors.lastname: Wylie
authors.forename: Lynda A
authors.initials: LA
authors.lastname: Morrison
mesh_terms: D000818:Animals; D001921:Brain / Q000821:virology; D005260:Female; D006561:Herpes Simplex / Q000821:virology*; D017405:Herpes Simplex Virus Protein Vmw65 / Q000378:metabolism; D018258:Herpesvirus 2, Human / Q000254:growth & development* / Q000276:immunology; D047468:Immunoprecipitation; D007370:Interferon Type I / Q000276:immunology; D016898:Interferon-alpha / Q000172:deficiency; D016899:Interferon-beta / Q000172:deficiency; D051379:Mice; D018345:Mice, Knockout; D017354:Point Mutation; D011485:Protein Binding; D012260:Ribonucleases / Q000235:genetics* / Q000378:metabolism*; D012720:Severity of Illness Index; D016019:Survival Analysis; D014621:Vagina / Q000821:virology; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism*; D015678:Viral Structural Proteins / Q000378:metabolism; D014771:Virion / Q000737:chemistry; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D019065:Virus Assembly / Q000502:physiology
chemical_list: D017405:Herpes Simplex Virus Protein Vmw65; D007370:Interferon Type I; D016898:Interferon-alpha; D014764:Viral Proteins; D015678:Viral Structural Proteins; D037521:Virulence Factors; C114208:protein VP22, Herpes simplex virus type 2; C070722:virion host shutoff protein, Simplexvirus; D016899:Interferon-beta; D012260:Ribonucleases