Peptide stimulation experiments were conducted using splenic lymphocytes derived from NP DNA vaccine-immunized chickens to verify some of the predicted potential T cell epitopes. To assess the immune effects of the vaccine, serum NP antibody was detected using the ELISA method. Compared to the control group, a significant increase (P,0.01) in blood NP antibody was observed in the immunized group two weeks after the first vaccination. After the boost, the blood NP antibody level of the immunized group increased further and it remained at a high level throughout the duration of the experiment (Fig. 9 ). This indicated that the immune systems of the chickens were activated by the vaccine immunization and that the splenic lymphocytes of chickens were sensitized.