Figure 2.

Mouse serum antibodies against STa toxin in vitro antibody neutralization assay with T-84 cells and EIA cGMP kit. Pooled serum samples (30 μl) from each immunization group or the control group were used to incubate STa (2 ng). The serum/toxin mixture samples were added to T-84 cells. After 1 h incubation, intracellular cGMP levels (pmole ml⁻¹) in T-84 cells were measured.(A) Intracellular cGMP levels in T-84 cells incubated with STa toxin and pooled serum from the SC immunized group using 2 μg dmLT or ISA51 adjuvant, or from the control group. (B)Intracellular cGMP levels in T-84 cells incubated with STa toxin and pooled serum from the IP immunized groups using 2 μg dmLT, 0.2 μg dmLT or FIA as the adjuvant, or from the control group. Baseline cGMP levels (T-84 cells incubated with cell culture medium) and cGMP levels in T-84 cells incubated with 2 ng STa (as positive reference) were included. P values were calculated with Student's t-test. Boxes and bars represented means and standard deviations of cGMP levels, respectively.