Figure 3: Levels of antibodies of mice immunized with gene gun in each group by ELISA. Figures (a), (b), and (c) display detection of specific IgG, IgG1, and IgG2a antibodies, respectively. Figure (d) displays the ratio of IgG1-to-IgG2a in pVAX1/SjTGR group. A, B, and C indicated before vaccination, 10 d after prime vaccination, and 10 d after boost vaccination. D indicates that 42 d after challenged with cercariae. The results are presented as mean SD for each group (pVAX1/SjTGR, pVAX1, PBS). The asterisk (*) indicates significantly increased antibody levels of serum collected from pVAX1/SjTGR compared with both pVAX1 and PBS control.