title: Multiple amino acid substitutions are involved in the adaptation of H9N2 avian influenza virus to mice.
abstract: To explore adaptation of avian influenza virus to mice we previously performed serial lung-to-lung passages of the influenza A/Chicken/Jiangsu/7/2002 (H9N2) strain, resulting in the isolation of a variant influenza strain lethal for mice. We now report that virulence correlates with improved growth characteristics on mammalian cells and extended tissue tropism in vivo. Sequencing of the complete genomes of the wild-type and mouse-adapted viruses revealed 25 amino acid substitutions. Some were found to reiterate known substitutions in human and swine H9N2 influenza isolates. Functions affected include nuclear localization signals and sites of protein and RNA interaction, while others are known determinants of pathogenicity and host specificity such as the viral polymerase PB2 E627K substitution. These observations suggest that enhanced growth characteristics and modified cell tropism may contribute to increased virulence in mice. We conclude that multiple amino acid substitutions are likely to be involved in the adaptation of H9N2 avian influenza virus to mice.
authors.affiliation: Institute of Animal Husbandry and Veterinary Science, Hubei Academy of Agricultural Sciences, Wuhan 430064, Hubei, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Wu
authors.forename: Hongbo
authors.initials: H
authors.lastname: Zhang
authors.forename: Keli
authors.initials: K
authors.lastname: Yang
authors.forename: Wangwang
authors.initials: W
authors.lastname: Liang
authors.forename: Zhongliang
authors.initials: Z
authors.lastname: Xiong
authors.forename: Zewen
authors.initials: Z
authors.lastname: Liu
authors.forename: Xuehai
authors.initials: X
authors.lastname: Yang
authors.forename: Huabin
authors.initials: H
authors.lastname: Shao
authors.forename: Xinmin
authors.initials: X
authors.lastname: Zheng
authors.forename: Mingxin
authors.initials: M
authors.lastname: Chen
authors.forename: Diping
authors.initials: D
authors.lastname: Xu