Figure 2
Humoral immune responses. A IgY titers of sera from different groups on days 14, 21, 28, and 38. The serum samples were diluted 1:10 before the ELISA assay. B The p values for pairwise comparisons of IgY titers between different groups are shown. C Tracheal lavage IgA titers of different groups on days 14, 21, 28, and 38. The lavage samples were diluted 1:10 before the ELISA assay. D The p values for pairwise comparisons between different groups for IgA antibodies. Chickens were immunized with BGs through inhalation (Inhal. BGs + Expo.), BGs by injection (Inj. BGs + Expo.), and injection of killed vaccine (killed + Expo.) on days 7, 14, 21, and were challenged on day 28 with the wild type E. coli O78:K80. Chickens in the only exposure (only Expo.) group without immunization were challenged. Chickens in the negative control (Neg. Ctrl.) group neither received any immunization nor challenged. Data represent the OD450 nm of at least three to five chicken samples in triplicate. Data in both B and D were normalized with the corresponding data in the Neg. Ctrl group. The bold font in B and D represents the statistically significant p values (p < 0.05).