Monitoring Of H9N2 Avian Influenza Antibody In Huangyu Chicken In Jiangmen Area And Evaluation Of Immunization Effect Of Local Isolates Strain

Avian influenza is the infectious disease which seriously affect poultry industry and public health.The pathogeny is avian influenza virus with varies of serotype.In recent year,H5N6,H7N9 and H9N2 subtype AIV prevalent in our country.According to the pathogenicity avian influenza virus can be divided into Highly Pathogenic Avian Influenza Virus(HPAIV)and Lowly Pathogenic Avian Influenza Virus(LPAIV),studies have shown that most of the H9N2 subtype avian influenza viruses belong to LPAIV.In most cases,it will only cause mild respiratory symptoms or egg drop.However,if the poultry was mixed infection with bacteria or secondly infection,it may causes large death,leading large economic losses.The most effective way to prevent H9N2 AIV is injected inactivated vaccine.Because of the genetic mobility characteristics of AIV,phenomenon of virus carried and excreted among the immune poultry occurred frequently.So analyseing genetic mobility of H9N2,select the match strains and prepare the inactivated vaccine is sensitive to prevent this disease.In this study,serum from chickens in Jiangmen,Guangdong Province was collected,and antibody was tested by HA-HI test to carry out H9N2 subtype AIV serological investigation to evaluate the immune effect of H9N2 subtype AIV inactivated vaccine.HAHI test results were found,after the vaccination of the broiler chickens in the region,56% of the population can reach the antibody level of 9log2 or more,and the remaining 44% of the chickens have the antibody level of 7-9log2.Using SPSS18.0 software to make correlation coefficient statistical analysis of antibody uniformity,antibody level and age between broiler groups,found that antibody uniformity was significantly negatively correlated with antibody level,correlation coefficient was-0.562;antibody uniformity It was related to weak age,and the correlation coefficient was-0.257.There was also a strong positive correlation between day age and antibody level,and the correlation coefficient was 0.443.The antibody level of the flocks is significantly higher than the broiler flocks.The antibody level of 64.3% of the laying flocks can reach more than 10log2,and 28.6% is between 9～10log2.At the same time,pharyngeal anal cotton swabs were collected,and the virus was isolated and identified by chicken embryo inoculation method.Two strains of H9N2 subtype avian influenza virus strains of JM1 and JM3 were isolated and identified from the samples taken.The results of sequencing analysis showed that the HA gene sequences of both viruses were 1683 bp,encoding 560 AA.The nucleotides and amino acids with the A/chicken/Yunnan/YNKM/2015(H9N2)isolates have the highest homology,97.5%～98% and 98.0%～98.7%,respectively;and the classic vaccine strain SS strain,F98 The homology of the strain was about 88.6%～89% and 88.4%～89%.The amino acid sequence near the cleavage site of the HA gene is PSRSSR/GL,and there are no consecutive basic amino acid insertions in the vicinity,which has the typical HA gene characteristics of LPAIV.The virus lacks a glycosylation site at positions 218-220,suggesting that it may enhance viral pathogenicity.Phylogenetic tree analysis indicated that all belong to the Y280 small branch of the CK/Beijing-like branch(h9.4.2.5 sub-branch),which is closely related to A/Duck/Hong Kong/Y280/97,and A/Quail/Hong Kong/ G1/9(h9.4.1 branch)is far from the domestic vaccine strain.JM3 strain were successfully developed and prepared to be inactivated vaccine under laboratory conditions.The HA titer of the semi-finished product was more than 1:512,the physical character test,sterility test and safty test of the inactivated vaccine was approved.The prepared H9N2 AIV inactivated vaccine(JM3 strain)laboratory challenge protection effect,the parental strain JM3 strain and The strains of the popular strain SD have a 100% protection rate,indicating that the isolated strain can be suitable as a vaccine candidate strain.