Figure 3. Antibody response trend and long-term humoral immune response induced by NM2e protein in mice.

(A and B) Mice were immunized intramuscularly with 10 µg of NM2e protein three times at 2-week intervals. Al(OH)₃ and/or CpG 1826 were used as adjuvants. Mice immunized with normal saline (NS) or adjuvant alone was used as negative controls. Serum was obtained from each mouse on days 14, 28, and 38, respectively, and analyzed for the presence of IgG antibodies specific for NP (left) or M2e (right), in an ELISA, as described in the Materials and Methods. Antibody response trends after three immunizations are presented in A, and the comparison of results on day 38 are presented in B. Columns show geometric mean antibody titers, and bars indicate the 95% confidence interval in each group. Plots in B show the NP- and M2e-specific IgG titers of all of the mice in each treatment group on day 38, and bars indicate the geometric mean antibody titers of each treatment group (n = 6 mice per experimental group, except n = 5 mice in the NS group). Lines above two or more groups indicate that they have the same comparative results. *, p≤0.05; **, p≤0.01; ***, p≤0.001 by one-way ANOVA. (C) Mice were immunized intramuscularly with 10 µg of NM2e protein formulated with Al(OH)₃ three times at 2-week intervals or immunized with a single dose of 10 µg of NM2e formulated with Al(OH)₃. Serum was prepared from each mouse at the indicated times, and NP- and M2e-specific IgG antibodies were analyzed by ELISA, as described in the Materials and Methods.