ABSTRACT
Objective@#To evaluate the immunogenicity of split influenza H1N1 vaccine formulated with an oil-in-water nano-emulsion adjuvant in aged mice and young mice.@*Methods@#A nano-emulsion adjuvant formulated split influenza H1N1 vaccine was used to immunize aged and young mice through intramuscular injection. Each mouse was immunized with 0.012 μg of hemagglutinin (HA) twice with an interval of 28 d. Hemagglutination inhibition (HI) titers in serum were measured 27 d after first immunization. Serum HI, IgG1 and IgG2a titers were detected 14 d after the last immunization. No adjuvant-formulated vaccine and normal saline (NS) were used to set up control groups. Virus challenge test was carried out using 10 times the median lethal dose (LD50) of A/Puerto Rico/8/34 (H1N1) strain two weeks after the last immunization and the protective effects were assessed through measuring the dynamic changes in body weight and survival rate.@*Results@#Higher levels of serum HI, IgG1 and IgG2a antibodies and higher HI antibody conversion rates were induced in the adjuvant groups, especially in the aged mice group, than in the control groups. Nano-emulsion adjuvant improved the immunogenicity of HA and mouse immunity to A/Puerto Rico/8/34 (H1N1).@*Conclusions@#Nano-emulsion adjuvant could enhance the immunogenicity of influenza antigens, especially in aged mice.