Genetic characterization and protective immunity of cold-adapted attenuated avian H9N2 influenza vaccine.
H9N2 influenza viruses are endemic in many Asian countries including China and Korea, and cause a considerable economic loss to chicken industry by reduction in egg production and about 30% mortality. Here we developed live cold-adapted attenuated H9N2 influenza vaccine by adaptation of viruses in hen's eggs at 25 degrees C. Genetic analysis shows that the cold-adapted H9N2 (A/Chicken/Korea/S1/03) viruses contain a total of 44 amino acid substitutions, of which 7 amino acids are identical to the loci identified in the cold-adapted H2N2 (A/Ann Arbor/6/60) vaccine strain compared to genes in wild-type H9N2 (A/Chicken/Korea/S1/03) influenza viruses. When cold-adapted H9N2 (A/Chicken/Korea/S1/03) influenza viruses were inoculated in layers viruses were detectable in the tracheas, not in the lungs, no reduction of egg production and mortality was observed in contrast to the infection of wild-type H9N2 influenza viruses, and CD8+ T lymphocytes expressing IFN-gamma were induced. When layers vaccinated with cold-adapted attenuated H9N2 (A/Chicken/Korea/S1/03) influenza viruses were challenged with wild-type H9N2 (A/Chicken/Korea/521/04) influenza viruses, they were protected from the loss of egg production and mortality. Our results suggest that cold-adapted attenuated H9N2 vaccine can be used for controlling the infection of H9N2 influenza viruses in chickens.
Laboratory of Influenza Research, College of Veterinary Medicine, Chungnam National University, 220 Gung Dong, Yuseong-Gu, Daejeon 305-764, Republic of Korea.
Joo Sub
JS
Lee
Hyun Soo
HS
Kim
Sang Heui
SH
Seo
D000222:Adaptation, Physiological; D019943:Amino Acid Substitution; D000818:Animals; D002645:Chickens / Q000276:immunology* / Q000821:virology; D003080:Cold Temperature; D004531:Eggs / Q000821:virology; D005260:Female; D006385:Hemagglutination Inhibition Tests; D053127:Influenza A Virus, H9N2 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000235:genetics* / Q000276:immunology*; D005585:Influenza in Birds / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D009154:Mutation; D014613:Vaccines, Attenuated / Q000235:genetics / Q000276:immunology
D007252:Influenza Vaccines; D014613:Vaccines, Attenuated