title: Evolutional analysis of human influenza A virus N2 neuraminidase genes based on the transition of the low-pH stability of sialidase activity.
abstract: The 1957 and 1968 human pandemic influenza A virus strains as well as duck viruses possess sialidase activity under low-pH conditions, but human H3N2 strains isolated after 1968 do not possess such activity. We investigated the transition of avian (duck)-like low-pH stability of sialidase activities with the evolution of N2 neuraminidase (NA) genes in human influenza A virus strains. We found that the NA genes of H3N2 viruses isolated from 1971 to 1982 had evolved from the side branches of NA genes of H2N2 epidemic strains isolated in 1968 that were characterized by the low-pH-unstable sialidase activities, though the NA genes of the 1968 pandemic strains preserved the low-pH-stable sialidase. These findings suggest that the prototype of the H3N2 epidemic influenza strains isolated after 1968 probably acquired the NA gene from the H2N2 low-pH-unstable sialidase strain by second genetic reassortment in humans.
authors.affiliation: Department of Biochemistry, University of Shizuoka, School of Pharmaceutical Sciences, CREST, JST, and COE Program in the 21st century, Shizuoka 422-8526, Japan. suzukit@u-shizuoka-ken.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Tadanobu
authors.initials: T
authors.lastname: Takahashi
authors.forename: Takehiko
authors.initials: T
authors.lastname: Saito
authors.forename: Chao-Tan
authors.initials: CT
authors.lastname: Guo
authors.forename: Kazuya I-P Jwa
authors.initials: KI
authors.lastname: Hidari
authors.forename: Daisei
authors.initials: D
authors.lastname: Miyamoto
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Suzuki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002642:Chick Embryo; D004372:Ducks; D019143:Evolution, Molecular; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009980:Influenza A virus / Q000201:enzymology* / Q000235:genetics*; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000235:genetics* / Q000378:metabolism
chemical_list: D009439:Neuraminidase