Antibody responses to the SG mutant JOL916 and the LTB adjuvant strain JOL1229. Antibody responses to SG specific antigen in chickens, orally prime-boost immunized with the vaccine candidate strain (JOL916) and/or the LTB adjuvant strain (JOL1229). Group A chickens were primed and boosted with a mixture consisting of four parts JOL916 (0.8 × 108 CFU) and one part JOL1229 (0.2 × 108 CFU), group B chickens were primed with a mixture consisting of four parts JOL916 (0.8 × 108 CFU) and one part JOL1229 (0.2 × 108 CFU), and were boosted with JOL916, and group C chickens were inoculated with PBS as the control group. (A) Plasma IgG concentration (μg/ml); (B) Secretory IgA concentration (μg/ml) in intestinal lavage. Lower case letters indicate a significant difference (p < 0.05) between each immunized and control group (a: Group A, b: Group B).