Fig. 1

a Mouse immunization and analysis scheme. b rPSOP25 was purified from E. coli and analyzed on a 10% SDS-PAGE gel. c Antibody titers in immunized mice during immunization, experimental mice were immunized with rPSOP25 formulated in Freund’s adjuvant; control mice were immunized with only Freund’s adjuvant and 0.1 M PBS. The data represent two separate experiments. Error bar shows mean ± standard deviation (SD). SD indicates the assay variance. **P < 0.01 (Student’s t-test). d Anti-rPSOP25 total IgG titer at 10 days after the final immunization analyzed by ELISA. Mean of control antisera + 3 × SD is shown by the broken lines. IgG titers correspond to the last dilution of the anti-rPSOP25 sera where in OD490 values were above the cut-off values. Cut-off value was defined as that of the pooled sera from control mice. The experiment was performed three times. Error bar shows mean ± SD. *P < 0.05, **P < 0.01 (Student’s t-test). Abbreviations: M, molecular weight marker; rPSOP25, purified rPSOP25 under reducing conditions