Figure 2. Recall systemic immune responses.

The recall humoral immune responses in serum and lung suspensions were determined in MN and IM immunized mice 12 weeks post immunization and 4 days post-challenge. Naïve infected (Inf) and naïve uninfected (N) mice were used as control groups. Serum HAI titers (a), total serum IgG titers (b), and isotype IgG1 and IgG2a profile (c, d). INF: infected mice, N: naïve mice. ELISA antibody data represent the mean ± SEM and the HAI data represent the geometric mean ± 95% CI. *: p<0.05. Statistics for the MN and IM group were performed with two-tailed unpaired Student's t-test.