FIG 6.
cAMP and cGMP EIA ELISAs show the same levels of in vitro protection against CT or STa enterotoxicity by serum antibodies of mice immunized with MecVax or toxoid fusion protein 3xSTaN12S-mnLTR192G/L211A. Intracellular cAMP or cGMP levels (nM) were measured in T-84 cells exposed to CT or STa that was pretreated with serum samples from mice i.m. immunized with MecVax (MecVax), toxoid fusion protein 3xSTaN12S-mnLTR192G/L211A (TF), or PBS (Control). Two more treatment groups were included, T-84 cells exposed to culture medium alone (Media) to establish the baseline cAMP and cGMP levels and T-84 cells exposed to CT alone (CT) or STa toxin alone (STa) as the positive control to show elevation of intracellular cAMP or cGMP by CT or STa enterotoxicity. Bars and error bars represent the mean cAMP and cGMP values and standard deviations. *, P < 0.05; ***, P < 0.001.