DETERMINATION OF THE MINIMUM DOSE AND ANTIBODY DYNAMICS OF AN INACTIVATED H9N2 AVIAN INFLUENZA VACCINE

The H9N2 subtype avian influenza vaccines have been used widely in China.Under intense immune pressure,variation of H9N2 subtype avian influenza viruses(AIV) has accelerated.At present,commercial H9N2 subtype avian influenza vaccines do not provide chickens complete protection against AIV infection.Therefore,we chose A/Chicken/Shanghai/441/2009(H9N2)(SH441) from a few of recent virus isolates to develop an inactivated vaccine.In the present study,we determined the minimum dose of this inactivated vaccine and antibody dynamics in immunized chickens.Three-week-old SPF chickens were injected intramuscularly with 0.01,0.02,0.04,0.05 or 0.08 mL of H9N2 AIV inactivated vaccine.After 21 days post-immunization,chickens were challenged with SH441 virus.The results demonstrated that the minimum dose of this vaccine was 0.02 mL per chicken.When immunized with 0.05 mL dose,chickens developed high level of HI antibodies.HI antibody titers peaked(12Log2) at 5 weeks post-immunization and then remained above 7 Log2 by 29 weeks post-immunization.All of these data provided a very good basis for further development of an inactivated H9N2 subtype AIV vaccine.