[The 50% effective dose (ED50a) of seasonal spilt influenza vaccine in mice].

OBJECTIVE: To evaluate the seasonal influenza spilt vaccine's immunogenicity and the 50% effective dose (ED50a) of hemagglutin (HA) that can make 50% of the mice hemagglutination inhibition antibody (HI) titers to 40. METHODS: The 2008-2009 seasonal influenza spilt vaccine's two components, with HA from H1N1 and H3N2 influenza virus respectively, were used as a model. Mice were immunized once or twice with different doses, and the HI antibody titers were tested to determine the immunization procedure and to evaluate the immugenicity of seasonal influenza spilt vaccine in mice; Consequently, HI antibody response kinetics of the two components were observed to determine the time point when the HI antibody titer reached the peak point; Finally, mice were immunized with different doses of HA to evaluate the ED50a that can make 50% of mice HI titers reach 40. RESULTS: Immunization procedures study showed that one-dose of seasonal influenza vaccine induced the HI antibody titers ranged from 10 to 120, while two-dose of influenza vaccine improved the HI antibody titer 10-100 times as compared with one dose; antibody kinetics study suggested that the time point of HI antibody produced to peak is 28-35 days post one dose immunization; and the ED50a detection results indicated that one dose of 1.5 microg HA could make 50% of the mice HI antibody titer reach 40. CONCLUSION: Seasonal influenza spilt vaccine is very immunogenic in mouse; the time point of HI antibody produced to peak is 28-35 days post one dose immunization; and the ED50a of HA is 1.5 microg, which can make 50% of the mice HI titer reach 40. The experimental results provided foundation for the establishment of influenza vaccine evaluation system based on seasonal influenza vaccine.