The immune efficacy of the H9N2 avian influenza ressortant virus Re-9 strain inactivated vaccine

To evaluate the immune efficacy of the vaccine strain Re-9 ressortant avian influenza virus(AIV) derived from H9N2 AIV,the 7-week-old SPF chicks was immunized with Re-9 inactivated vaccine and challenged,respectively,at 3 weeks post immunization with 5 isolates of H9N2 AIV isolated from 2010 to 2011 which the homologous of the HA and NA gene were 90.6% to 97.5% and 88.1% to 98.7%,and the antigen correlation value was 66.67% to 100% with Re-9 strain,respectively.The results showed that the average antibody titer of the HI was up to 9.5 log2 at 3 weeks post immunization.In addition,the virus shedding was detected by virus isolations with chicken embryonated eggs from the trachea and cloaca swab samples collected at 3,5 and 7 days post challenging,and virus shedding was all negative in the Re-9 vaccinated vaccine groups,but the positive rates in the control groups were higher than 80% at 3 and 5 days,and lower than 60% at 7 days post challenge,respectively.These results demonstrated that the inactivated vaccine prepared with Re-9 strain is high efficient against H9N2 AIV infection.