title: The replicase gene of avian coronavirus infectious bronchitis virus is a determinant of pathogenicity.
abstract: We have previously demonstrated that the replacement of the S gene from an avirulent strain (Beaudette) of infectious bronchitis virus (IBV) with an S gene from a virulent strain (M41) resulted in a recombinant virus (BeauR-M41(S)) with the in vitro cell tropism of the virulent virus but that was still avirulent. In order to investigate whether any of the other structural or accessory genes played a role in pathogenicity we have now replaced these from the Beaudette strain with those from M41. The recombinant IBV was in effect a chimaeric virus with the replicase gene derived from Beaudette and the rest of the genome from M41. This demonstrated that it is possible to exchange a large region of the IBV genome, approximately 8.4 kb, using our transient dominant selection method. Recovery of a viable recombinant IBV also demonstrated that it is possible to interchange a complete replicase gene as we had in effect replaced the M41 replicase gene with the Beaudette derived gene. Analysis of the chimaeric virus showed that it was avirulent indicating that none of the structural or accessory genes derived from a virulent isolate of IBV were able to restore virulence and that therefore, the loss of virulence associated with the Beaudette strain resides in the replicase gene.
authors.affiliation: Division of Microbiology, Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire, United Kingdom.
authors.forename: Maria
authors.initials: M
authors.lastname: Armesto
authors.forename: Dave
authors.initials: D
authors.lastname: Cavanagh
authors.forename: Paul
authors.initials: P
authors.lastname: Britton
mesh_terms: D000818:Animals; D002460:Cell Line; D002645:Chickens; D002522:Chlorocebus aethiops; D006224:Cricetinae; D016679:Genome, Viral; D001351:Infectious bronchitis virus / Q000201:enzymology* / Q000235:genetics*; D007668:Kidney / Q000821:virology*; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism; D008957:Models, Genetic; D011201:Poultry Diseases / Q000235:genetics / Q000821:virology; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics*; D014132:Trachea / Q000821:virology; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019065:Virus Assembly / Q000235:genetics
chemical_list: D008562:Membrane Glycoproteins; D014759:Viral Envelope Proteins; D012324:RNA-Dependent RNA Polymerase