title: Attenuation of a vaccine strain of vaccinia virus via inactivation of interferon viroceptor.
abstract: BACKGROUND
  Interferons (IFNs) play an important role in host antiviral responses, but viruses, including vaccinia viruses (VV), employ mechanisms to disrupt IFN activities, and these viral mechanisms are often associated with their virulence. Here, we explore an attenuation strategy with a vaccine strain of VV lacking a virus-encoded IFN-gamma receptor homolog (viroceptor).
  
  
  METHODS
  To facilitate the monitoring of virus properties, first we constructed a Lister vaccine strain derivative VV-RG expressing optical reporters. Further, we constructed a VV-RG derivative, VV-RG8, which lacks the IFN-gammaR viroceptor (B8R gene product). Replication, immunological and pathogenic properties of the constructed strains were compared.
  
  
  RESULTS
  Viruses did not show significant differences in humoral and cellular immune responses of immune-competent mice. Replication of constructed viruses was efficient both in vitro and in vivo, but showed marked difference in kinetics of propagation. In cultured CV-1 epithelial cells, the VV-RG8 strain retained the propagation potential of the parental virus, while, in the C6 glial cells, significant delay was observed in the kinetics of the VV-RG8 replication cycle compared to VV-RG. The pathogenesis of the viruses was tested by survival assay and biodistribution in nude mice. High dose inoculation of nude mice with VV-RG8 caused less pronounced virus dissemination, improved weight gain, and increased survival rate, as compared with the VV-RG strain.
  
  
  CONCLUSIONS
  The replication-competent virus VV-RG8 carrying a mutation at the B8R gene is less pathogenic for mice than the parental vaccine virus. We anticipate that step-wise inactivation of VV vaccine genes involved in evasion of host immune response may provide an alternative approach for generation of hyper-attenuated replication-competent vaccines.
authors.affiliation: Center for Molecular Biology and Gene Therapy, Loma Linda University, 11085 Campus St., Loma Linda, CA 92354, USA.
authors.forename: Béla
authors.initials: B
authors.lastname: Dénes
authors.forename: Daila S
authors.initials: DS
authors.lastname: Gridley
authors.forename: Nadja
authors.initials: N
authors.lastname: Fodor
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Takátsy
authors.forename: Tatyana M
authors.initials: TM
authors.lastname: Timiryasova
authors.forename: István
authors.initials: I
authors.lastname: Fodor
mesh_terms: D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D018014:Gene Transfer Techniques; D017930:Genes, Reporter; D007111:Immunity, Cellular; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D010957:Plasmids / Q000235:genetics; D051381:Rats; D017471:Receptors, Interferon / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000276:immunology; D012449:Safety; D014613:Vaccines, Attenuated / Q000235:genetics / Q000276:immunology; D014614:Vaccines, Synthetic / Q000235:genetics / Q000276:immunology; D014616:Vaccinia virus / Q000235:genetics* / Q000276:immunology* / Q000472:pathogenicity; D014765:Viral Vaccines / Q000235:genetics / Q000276:immunology; D014774:Virulence; D000096743:Interferon gamma Receptor
chemical_list: D017471:Receptors, Interferon; D014613:Vaccines, Attenuated; D014614:Vaccines, Synthetic; D014765:Viral Vaccines; D000096743:Interferon gamma Receptor