Immunogenicity and Cross Protection in Mice Afforded by Pandemic H1N1 Live Attenuated Influenza Vaccine Containing Wild-Type Nucleoprotein

Figure 4

Antibody immune responses following immunization of mice with H1N1 LAIVs. Groups of 12 mice were inoculated i.n. with two doses of 10⁶ EID₅₀ of each LAIV virus 21 days apart or mock-vaccinated. Mice sera were collected from 6 mice in each group 21 days after the first dose and 21 days after the second dose. HI (a) and IgG ELISA (b) tests were performed using egg-grown whole viruses SA/wt and NY/wt as antigens. Bars represent geometric mean with SD calculated from log₂-transformed HI and ELISA titers. Statistical significance of differences between the vaccine groups was estimated by the Mann–Whitney test. White bars: H1N1 LAIV (6 : 2) rg; grey bars: H1N1 LAIV (5 : 3) rg; black bars: Mock.

(a) Virus-specific HAI antibodies

(b) Serum IgG ELISA antibodies