| Avian influenza is caused by influenza virus type A. The clinical manifestations are respiratory infection, decline in egg production and alvi profluvium. H9 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. There are important significance to explore the genetic mutations of the hemagglutinin gene and the neuraminidase gene and the law of molecular epidemiology of H9 subtype avian influenza for prevention and curing the Avian influenza. In order to explore the genetic mutations of the hemagglutinin gene and the neuraminidase gene and the law of molecular epidemiology of H9 subtype avian influenza in China, Ten Avian influenza virus subtype H9N2 were isolated from some poultry yards in China in the years 2001-2007, and explored their virulence, immune reference and the genetic mutations. The investigation includes two experiments:In the first experiment, through the determination of hemagglutination properties, infected chicken embryo, the average time of death of chicken embryo and the ICPI, the virulence was analyzed and compared. Elected six virus which representing different regions and different periods and depurated these virus by Microdilution, maked manufacture single-factor serum and maked double cross-hemagglutination inhibition test. The results show that the virulences of there virus were weak and there were small disparity in antigenicity. The virulence of ACSD307 was more strong than the others. The HA potency is between 29 and 210, the HI potency for Standard antigen is between 11log2 and 13log2. The EID50 is between 10-5.62/0.2mL and 10-8.69/0.2mL. The EID50 of the ACSD307 is 10-8.69/0.2mL. There are some difference in MDT is between 90.0 hours and 108.1 hours. The correlation of the double cross-hemagglutination inhibition test is between 0.78 and 0.95. One result can be inferred that there will be a stronger strain under the immune pressure in the actual production.In the second experiment, the whole HA and NA cDNA fragments of the ten virus were amplified by reverse transcription polymerase chain reaction, with primers specific to HA gene and NA gene. After cloning and sequencing, gene sequences were analyzed on homology and heredity evolution. The sequence analysis showed the little degree of variation. The schizolysis site of HA Gene fragments are all the RSSR↓GLF. The virulence of ACHB101 has a new glycosylation site in the NO.145 amino acids. The NO.198 receptor binding site have more variation what are T,V,A. The NO.191 receptor binding site transform to agedoite, but the ACHN102 is Ser in this site. They belonged to a branch of the CBJ194-like in the phylogenetic tree. The nucleotide homology of the HA gene to the CBJ194 was from 88.8% to 95.8%. The nucleotide homology of the NA gene to the CBJ194 was from 93.4% to 97.6%, so they might come from the same source. Because of the gene mutation, the new potential glycosylation sit appear in the HA gene of the ACHB101 and a stenoplastic receptor-binding sit have changed in ACHN102. In the deduced amino acids sequence, the 63, 64 and 65 sites lost T, E and I, which induces the 61 site of glycosylation is lost. Otherwise, there was conspicuous mutation in the acetylneuraminic acid adsorption sites. These findings may be fruitful for making further study of genetic mutations of AIV in the field and improving the control strategies.
|
PDF Full Text Request