(IgG1) and TH2 (IgG2a) responses. The immunization scheme is shown in Figure 6B. Seven days after the second boost, sera were collected and IgG1 (A) and IgG2a (B) titers were determined by ELISA. F1mut-V was used as the coating antigen, since it covers all the epitopes present in both F1mut-V and F1mut-V10. Note that the sera of the control T4 phage-immunized mice showed higher background. This was because T4 phage, as demonstrated in previous studies, induces a strong antibody response to its components. Consequently, the sera from T4 phage- immunized mice will have increased amounts of IgGs compared to the pre-immune sera, giving more non-specific background at low dilutions of the sera. Data shown are the antibody titers of 12 mice in each group with S.D. (error bars). *, p<0.05; ***, p<0.001 (ANOVA).