Figure 3: Humoral immune responses in vaccinated mice. Mice were immunized IM or orally with C501 (pYA97R1N), live M. hyopneumoniae 168 vaccine, or PBS. Booster immunization was performed 2 weeks later. Serum samples were collected on day 14 (for primary response), and days 28 and 42 (for secondary response) o determine (a) the P97R1-specific IgA (b) the P97R1-specific IgG (c) the P97R1N-specific IgA 1 (d) IgG antibody titers. All data represent the 2 mean ± SD. Data with different letters (a–d) indicate significant differences between groups (p<0.05). “×” represents no detectable antibody levels of titers 10. *p < 0.05. **p < 0.01.