Whole Genome Sequence Analysis Of H9 Subtype Avian Influenza Viruses In Guangxi And The Selection Of Vaccine Candidate

H9N2 avian influenza virus (AIV) is prevalent in whole world and recognized as one of the main diseases which are greatly threatened to poultry industry. The major subtype of H9 AIV is H9N2 subtype. H9 subtype AIVs may cause respiratory and reproductive system disease in the flock and further result in slow growth and drops in egg production. The ability of infecting human makes H9 subtype AIVs become a threat to human public health.In order to understand the epidemical and ecological situation of H9 subtype AIVs in Guangxi, this study engaged in epidemiological surveillance of H9 subtype AIVs in poultry and wild birds during 2011 to 2014, establishment of duplex RT-PCR which is used to the detecting of H9 and N2 subtype AIVs. We also isolated, identified and purified 17 strains of H9 subtype AIVs and amplified the whole genome to analysis the sequence. The 17 strains of H9 subtype AIVs were identified as lowly pathogenic avian influenza virus according to the biological characteristics and nucleotide and amino acid sequences.16 strains were inclined to combine with both avian and human influenza virus receptor. The HA genes of the 17 strains of H9 subtype AIVs were in the different lineages with vaccine strains. Most of the eight gene segments of each strain were from different origin, that is to say, most of the strains were recombinant viruses. There were four kinds of recombinant models in total in this study.In order to evaluate the immune protective efficacy of commodity vaccine to variant strain and select an ideal candidate of H9 subtype avian influenza inactivated vaccine, we chose 10 strains of H9 subtype AIVs from the 39 isolates kept in our laboratory to perform antigenic analysis with vaccine strain (SS) and chose 4 isolates from the 10 to be developed into inactivated oil-emulsion vaccine. According to the results of cross protection tests, we found that the commodity vaccine (SS) couldn’t provide protection well against the viruses in Guangxi, while A/Chicken/Guangxi/CX/2013 (H9N2) isolate could stimulate the high antibody titers in SPF chickens and protect against the most epidemic strains in Guangxi. In conclusion, the A/Chicken/Guangxi/CX/2013 (H9N2) isolate could be selected as vaccine candidate.