H9n2 Guangxi Isolates The Ha Gene Sequence Analysis And Vietnamese And Chinese Students H9 Subtype Antibody Level Detection

Avian influenza viruses (AIV) are segmented, negative-sense, single-strand RNA viruses of the family Orthomyxoviridae. Currently,16 hemagglutinin (HA) subtypes and 9 neuraminidase subtypes of AIV have been isolated from avian species.According to the pathogenicity; the AIV can be divided into 2 groups, highly pathogenic avian influenza virus (HPAI) and low pathogenic avian influenza virus (LPAI). H9N2 avian influenza virus (AIV) is prevalent in whole world and recognized as one of the main poultry disease.H9N2 subtype of avian influenza is low-pathogenicity avian influenza. It can cause decline in egg production, growth retardation and a small quantity death.The mutation frequency of the avian influenza virus is frequently and the speed of propagation is quick, so it is very difficult to prevent the dissemination of the Avian influenza virus. In Mainland China, H9N2 avian influenza virus was firstly isolated from chickens in Guangdong province in 1994, and then H9N2 AIV circulated widely in the domestic poultry and had caused great economic losses in China. Moreover, H9N2 subtype avian influenza virus can infect humans, has important public health significance.This study mainly include:Molecular evolution analysing of HA genes of subtype H9N2 avian influenza viruses isolated in 2009 from Guangxi and serological survey of antibody to H9 subtypes of avian influenza A virus in medical college students in Guangxi and Hue. 1.Molecular evolution analysing of HA genes of subtype H9N2 avian influenza viruses isolated in 2009 from GuangxioObjective To determine the HA gene sequence of one H9N2 Avian influenza virus (AIV) strain and carry out comparative analysis so as to understand the difference and variation pattern of this strain from the angle of molecular biology and to know the distribution and epidemic law of H9N2 AFV. Method Two pairs of primers were designed referring to HA gene sequences of H9N2 AIV. The HA genes of Qa/GX/3131/2009(H9N2) was amplified, purified and sequenced. Then the HA gene sequence of this strain was compared with that of 13 H9N2 AIV stains in GenBank. Result The ORF of HA genes of this strain was 1683 bp in size, encoding 560 amino acids. The deduced amino acid sequences at the hemagglutinin cleavage site were R-S-S-R, typical of lowly pathogenic avian influenza. There was 7 potential glycosylation sites in the isolates. The nucleotide homology and amino acid homology between the isolate and reference strains were higher and the isolate was Eurasian species, and had a close relationships with A/Duck/Hong Kong/Y280/97strain Conclusion By analysis at molecular level, it could be concluded that Qa/GX/3131/2009 was low pathogenic H9N2 isolates of avian origin.2.Serological survey of antibody to H9 subtypes of avian influenza A virus in Vietnam and China。Objective To investigate whether 2010’s freshman students of Guangxi medical university and Hue medical university have been infected with H9 subtypes of avian influenza virus through detecting antibodies to H9 subtypes of avian influenza A virus. Methods A total of 500 serum samples were collected from the 2010’s freshman students of Guangxi Medical University and Hue Medical University and antibody to H9 subtypes of avian influenza virus were detected by HI. Results The positive rate of antibodies to H9 in Guangxi and Hue reached 19.20% and 12.40%, respectively. And infection rate of H9 subtype was not significantly difference in Guangxi and Hue. Conclusion The 2010’s freshman students of Guangxi Medical University and Hue Medical University have been infected with H9 subtype of avian influenza A virus. These findings suggest that the importance of systematic surveillance of H9 subtype in human.