Rapid evolution of low-pathogenic H9N2 avian influenza viruses following poultry vaccination programmes.
To investigate whether currently circulating H9N2 avian influenza viruses (AIVs) in domestic poultry have evolved in Korean poultry since 2007, genetic and serological comparisons were conducted of H9N2 isolates from poultry slaughterhouses from January 2008 to December 2009. The isolation rate was relatively low in 2008 but increased gradually from January 2009 onwards. Genetic and phylogenetic analyses revealed that reassortant viruses had emerged, generating at least five novel genotypes, mostly containing segments of a previously prevalent domestic H9N2 virus lineage (Ck/Korea/04116/04-like). It was noteworthy that the N2 genes of some H9N2 isolates (genotypes D, E and F) were derived from those of H3N2-like viruses commonly isolated among domestic ducks in live-poultry markets. Animal challenge studies demonstrated that the pathogenicity of Ck/Korea/SH0906/09 (genotype B) and Ck/Korea/SH0912/09 (genotype F) in domestic avian species was altered due to reassortment. Furthermore, serological analysis revealed that the isolates were antigenically distinct from previous Korean H9N2 viruses including Ck/Korea/01310/01. Such antigenic diversity was illustrated further in experiments using H9N2-immunized chickens, which could not inhibit the replication and transmission of challenge viruses from each genotype. These results suggest that H9N2 viruses from domestic poultry have undergone substantial evolution since 2007 by immune selection as a result of vaccinal and natural immunity, coupled with reassortment. Taken together, this study demonstrates that periodical updating of vaccine strains, based on continuous surveillance data, is an important issue in order to provide sufficient protectivity against AIV infections.
Park
Kuk Jin
KJ
College of Medicine and Medical Research Institute, Chungbuk National University, 12 Gaeshin-Dong Heungduk-Ku, Cheongju 361-763, Republic of Korea.
Kwon
Hyeok-Il
HI
Song
Min-Suk
MS
Pascua
Philippe Noriel Q
PN
Baek
Yun Hee
YH
Lee
Jun Han
JH
Jang
Hae-Lan
HL
Lim
Jai-Yun
JY
Mo
In-Phil
IP
Moon
Ho-Jin
HJ
Kim
Chul-Joong
CJ
Choi
Young Ki
YK
D000003:Abattoirs; D000818:Animals; D016000:Cluster Analysis; D019143:Evolution, Molecular; D005838:Genotype; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics; D053127:Influenza A Virus, H9N2 Subtype / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification* / Q000472:pathogenicity; D007252:Influenza Vaccines / Q000008:administration & dosage*; D005585:Influenza in Birds / Q000473:pathology / Q000517:prevention & control* / Q000821:virology*; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000235:genetics; D010802:Phylogeny; D011200:Poultry; D012367:RNA, Viral / Q000235:genetics; D016865:Reassortant Viruses / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity; D056910:Republic of Korea; D017422:Sequence Analysis, DNA; D014764:Viral Proteins / Q000235:genetics; D014774:Virulence
D007252:Influenza Vaccines; D012367:RNA, Viral; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase