title: Antigenic and S-1 genomic characterization of the Delaware variant serotype of infectious bronchitis virus.
abstract: A previously unrecognized infectious bronchitis virus (IBV) serotype, referred to hereafter as the Delaware variant (DE var), was isolated from commercial broiler chickens during a severe, widespread respiratory disease epornitic in the Delmarva peninsula region of the United States in January-March 1992. The DE var serotype was found to be antigenically unrelated by virus-neutralization (VN) test to nine reference IBV serotypes from North America. Additional VN tests indicated that the DE var isolates (DE/072/92, DE/121/ 92, DE/152/92, and DE/174/92) from broilers were fully or partially neutralized by monospecific antisera prepared against themselves and against two IBV field isolates (DE/492/90 and DE/903/90) recovered from a Delmarva commercial layer flock experiencing egg production losses in 1990. Antigenic relatedness values determined by VN indicated layer isolate DE/492/90 was more closely related to the broiler DE var isolates than was layer isolate DE/903/90. Cross-challenge tests performed in specific-pathogen-free chickens also demonstrated the antigenic similarity of the broiler (DE/072/92 and DE/174/92) and the layer isolates (DE/492/90 and DE/903/90), with heterologous strain protection values ranging from 55% to 100%. Protection values of DE var isolates vs. Massachusetts 41 and Arkansas DPI were considerably lower (0-60%). The S-1 gene of the US/DE/072/92 isolate of the DE var serotype was amplified by reverse transcription polymerase chain reaction, cloned, and sequenced. The DE var S-1 gene sequence was compared with the S-1 gene sequences of IBV serotypes from North America, Europe, and Australia. A dendrogram based on this analysis supported the conclusion that the DE var serotype is highly novel among IBV. A high degree of similarity (> 88%) was observed between the S-1 genes of the DE var broiler isolates (DE/072/92 and DE/174/92) and layer isolates (DE/492/90 and DE/903/90). These data, taken with the VN and cross-challenge results, establish a genetic as well as an antigenic link between the isolates from layers and broilers and indicate the DE var serotype was responsible for both infectious bronchitis outbreaks.
authors.affiliation: Delaware Agricultural Experiment Station, Department of Animal and Food Sciences, College of Agricultural Sciences, University of Delaware, Newark 19717-1303, USA.
authors.forename: J
authors.initials: J
authors.lastname: Gelb
authors.forename: C L
authors.initials: CL
authors.lastname: Keeler
authors.forename: W A
authors.initials: WA
authors.lastname: Nix
authors.forename: J K
authors.initials: JK
authors.lastname: Rosenberger
authors.forename: S S
authors.initials: SS
authors.lastname: Cloud
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000032:analysis*; D001315:Australia; D018175:Birnaviridae Infections / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary*; D002642:Chick Embryo; D002645:Chickens; D003429:Cross Reactions; D003691:Delaware / Q000453:epidemiology; D005060:Europe; D014644:Genetic Variation; D016679:Genome, Viral; D007243:Infectious bursal disease virus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D009500:Neutralization Tests; D009656:North America; D010802:Phylogeny; D011201:Poultry Diseases; D012703:Serotyping; D014765:Viral Vaccines / Q000008:administration & dosage
chemical_list: D000956:Antigens, Viral; D014765:Viral Vaccines