Research On Improving The Immune Response Of Avian H9N2 DNA Vaccine

H9N2 subtype influenza A virus(IAV)has more than 20 genotypes that are able to cross species barriers and expand from birds to mammals and humans.29 strains of H9N2 avian influenza virus were isolated from different chicken farms of China in 2017.According to the evolution analysis of HA genes,four H9N2 strains were selected for further research,namely Ck/Shanghai//97/17(abbreviation:H97),Ck/Jiangsu/514/17(abbreviation:H514),Ck/Jiangxi/1271/17(abbreviation:H1271)and Ck/Anhui/1523/17(abbreviation:H1523).Next,the optimized HA genes and NA gene were used for H9N2 DNA vaccine plasmid construction.The main contents of this study including followings:1.Immunization test results of SPF chickens immunized with single gene,two gene and three gene H9N2 DNA vaccines showed that the immunization effect of three gene fragments was better than the single or two gene fragments.2.The p?H97N9SH4 and p?H1271N9SH4 were immunized into SPF chickens at a dose of 10-100 ?g.After the second immunization,the serum antibodies in all immunized chickens turned positive.Among them,the HI titer could reach 25 and above after 3 weeks at a dose of 50-100 ?g.3.Animal experiments in the immune challenge group have shown that after being immunized with H9N2 DNA plasmids,it can provide certain protection.The current results show that when the HI titer in the serum reaches 25 and above after immunization,the anti-virus ability can be significantly improved.4.In the three-gene system,the expression of the H4-HA gene initiated by SV40 promoter has little effect on the immune response by H9N2 DNA vaccine immunization.While replace the H4-HA with a 20 repeats rich B-type CpG sequence,the immune effect is becoming better than contain H4-HA H9N2 DNA vaccine plasmid.