Specific SEB antibodies. Sera (A) and stools (B) from the different groups of mice were collected and analyzed by ELISA after the first oral administration. Immune response was assayed in mice orally immunized with recombinant Lactococcus lactis pSEC:rSEB or pCYT:rSEB. Significant results are marked with asterisks: *, p < 0.05; ** p < 0.01. Values were recorded as standard deviation of samples from 10 mice per group.