Immune responses in BALF. Immunized mice were infected with 0.5×LD50 of Aichi virus 4 weeks after the boosting immunization. (A), Levels of virus-specific IgG antibody titers. IgG levels were measured from BALF pre-challenge and 4 days post-challenge by ELISA using inactivated Aichi virus as coating antigen. (B, C and D), Levels of cytokines. IFN-γ, IL-4 and IL-6 in BALF were determined after virus infection by cytokine ELISA. (E), Body weight changes. (F), Lung viral titers. Mice lungs were collected 4 days post-challenge and virus titers were titrated using plaque assay with MDCK cells. Data represent mean ± SD. *: p<0.05, **: p<0.01, ***: p<0.001.