Table 2.

Structure alteration and toxicity of STa expressed by mutant strains. Supernatant of overnight growth (in 4 AA medium) from an equal amount of cells for each strain was used in STa competitive ELISA and cGMP ELISA. Reactivity of modified STa peptides to anti-STa serum was expressed as protein structure similarity by referring to the recombinant STa. Crude overnight culture growth of each mutant strain, the recombinant strain, and the negative control strain was used in porcine ligated gut loop assay.