Study On Neuraminidase Gene's Molecular Evolution Of Human Influenza Virus (H3N2) Isolated In China

In order to understand human influenza virus (H3N2) the NA gene mutationCharacteristic and the rule, the evolution tendency and discover the neuraminidase inhibitorresistant viruses in mainland China, the NA gene of 585 strains of human influenza virus(H3N2) isolates from 1968～2005 in Chinese National Influenza Center conserved weresequenced, analyzed with bioinformatics tools, There are several conclusions as followingfrom our experiment results:(1)NA gene evolution way showed a main evolution branch with multiple short side,the sequence disparity and the age is proportional, the NA evolution does not have theobvious region characteristic, the new mutation virus appearance has not periodicity.(2)There is an obvious lag between vaccine strains recommended by WHOand Chinese circulating strains in phylogenetic tree of the NA nucleotide and aminoacid in the past years.(3)The NA amino acid and the nucleotide evolution rate assumes the folding shape ineach year, the evolution rate in epidemic years is located the peak spot. Overall, the aminoacid evolution speed is higher than the nucleotide, the antigen sites's evolution is fastest, nextis stalk and the transmembrane domain, but in the epidemic years, which position appearancemutation is not rule.(4)Most amino acid are conservation and only 48% are mutation, the amino acid lossand insertion in the NA entire gene sequence had not discovered, various antigen site has itscharacteristic respectively in 7 antigen sites, its 197～199 aa mutation rate is highestspecifically the 197 aa, therefore it is a most important antigen site, however 153 aamutation rate is lowest. The neuraminidase active-site residues maintenance high conservative,also had not discovered the neuraminidase inhibitor resistant viruses in 1968～2005 inmainland of China. The bisulfide bond and the glycosylation site in NA protein areconservative, one of the epidemic reason possibly is the glycosylation site suddenly appearand vanish. From the analysis also discovered 143 and 267 mutation rate must be higher thanantigen sites's residues, their concrete biology significance also needs further to study.(5)This is the first study on NA gene's molecular evolution of human influenzavirus(H3N2) isolated in China ,our result will provide the basic theory basis for our countryinfluenza prevention and the control work as well as provide the instruction function to theNA inhibitor medicine use.