Safety and immunogenicity of a domestic tetravalent influenza virus subunit vaccine in mice

Objective To evaluate the safety and immunogenicity of a domestic tetravalent influenza virus subunit vaccine in mice. Methods The vaccine was subjected to identification test and acute toxicity assay according to Chinese pharmacopoeia (2015 edition, volume Ⅲ). Then, 40 specific pathogen-free female Kunming mice were divided into 4 groups by randomized block method with 10 mice each. They were intraperitoneally inoculated with 7.5, 15.0, 30.0 μg vaccines and PBS control, respectively, 1.0 ml each. Orbital blood was collected after 21 days of inoculation. Antibodies were measured by hemagglutination inhibition method and seroconversion rate was calculated. The results were compared using t-test. Results The identification test showed that antigenicity of the vaccine strains was identical with that of recommended virus strains. No abnormalities in the appearance, behavior, secretions, excretions were observed in both vaccine groups and control group as indicated by acute toxicity assay. All mice survived. During the 14 d observation period, the body weights of mice in vaccine groups (22.0-33.0 g) and control group (21.8-33.7 g) were not statistically different (t=-1.90 - 1.03, all P>0.05), and both increased compared with those before immunization (21.4-23.6 g and 21.2-23.4 g). There were no obvious pathological changes in the heart, lung, brain, and liver. Serum antibody titers induced by 3 dose vaccines (1∶69 - 1∶998) were significantly higher than those induced by PBS control (1∶6-1∶25) (t=3.68 - 4.88, all P<0.01). The seroconversion rates of 15.0 and 30.0 μg dose groups reached 100%. Conclusion The tetravalent influenza virus subunit vaccine is safe and has good immunogenicity. Key words: Influenza vaccines; Vaccines, subunit; Safety; Immunogenicity