Fig. 2

Antibody responses generated by each immunization group. a Schematic diagram of mouse immunizations and sampling. b PSOP25-specific IgG levels for three immunizations in the sera of immunized mice in each group. Sera were harvested and tested post-first immunization on days 14, 28, and 38. c PSOP25-specific IgG titers for three immunizations in the sera of immunized mice in each group. Serum samples were measured at two-fold serial dilution. The lower horizontal line (cut-off value) represents the average value of the negative control antisera + 3 × SEM. d The antibody avidity index of PSOP25-specific IgG was assessed on day 28 (left of dash line) and day 38 (right of dash line) with serum samples from mice in each group. Sera were treated with PBS or 8 M urea. The avidity index was calculated as the ratio of the ELISA OD490 value of 8 M urea-treated wells to control wells incubated in PBS. Error bars were indicated as mean ± SD