title: Rapid heat-treatment attenuation of infectious bronchitis virus.
abstract: In the present study we describe the rapid development of an attenuated live vaccine for GA08, a new serotype of infectious bronchitis virus, using a heat-treatment method. Incubation of the GA08 strain of IBV at 56 degrees C and passage in embryonated eggs was used as a method to fast track the attenuation process. The virus was incubated in a 56 degrees C water bath and aliquots were removed every 5 min for up to 1 h, and then each aliquot was inoculated into 10-day-old embryonated eggs. Virus with the longest incubation time that produced lesions in the embryos was harvested, again incubated at 56 degrees C as described and passaged in embryonated eggs. Attenuation of the virus, designated GA08/GA08HSp16/08, was verified in 1-day-old specific pathogen free chicks. A 10x dose of the vaccine was found to be safe for 2-week-old broiler chicks of commercial origin. The efficacy of the heat-treated attenuated virus was determined by vaccinating broiler chicks of commercial origin at 1 and 14 days of age intraocularly/intranasally. Vaccinated birds that were challenged with 10(4.5) median embryo infectious doses of pathogenic GA08 virus/bird at 28 days of age were protected from the disease, and challenge virus was only detected in the trachea of one of 21 birds by real-time reverse transcriptase-polymerase chain reaction at 5 days post challenge. The attenuation process took 10 weeks to complete, which is a substantially shorter time than required to attenuate infectious bronchitis virus by serial passage in embryonated eggs without heat treatment (38 weeks or more).
authors.affiliation: Department of Population Health, Poultry Diagnostic and Research Center, 953 College Station Road, University of Georgia, Athens, GA 30602, USA. mjackwoo@uga.edu
authors.forename: Mark W
authors.initials: MW
authors.lastname: Jackwood
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Hilt
authors.forename: Holly S
authors.initials: HS
authors.lastname: Sellers
authors.forename: Susan M
authors.initials: SM
authors.lastname: Williams
authors.forename: Hiram N
authors.initials: HN
authors.lastname: Lasher
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn / Q000276:immunology / Q000821:virology; D001483:Base Sequence; D002642:Chick Embryo / Q000276:immunology; D002645:Chickens / Q000276:immunology / Q000821:virology; D018352:Coronavirus Infections / Q000276:immunology* / Q000662:veterinary; D017931:DNA Primers; D006358:Hot Temperature; D006799:Housing, Animal / Q000592:standards; D001351:Infectious bronchitis virus / Q000145:classification / Q000235:genetics / Q000276:immunology*; D010802:Phylogeny; D011201:Poultry Diseases / Q000276:immunology*; D012367:RNA, Viral / Q000235:genetics / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012449:Safety; D014613:Vaccines, Attenuated / Q000276:immunology; D014765:Viral Vaccines / Q000008:administration & dosage
chemical_list: D017931:DNA Primers; D012367:RNA, Viral; D014613:Vaccines, Attenuated; D014765:Viral Vaccines