Fig. 3.

Determination of intestinal mucosal antibody responses in different immunization groups. Groups of five chickens were inoculated orally and nasally with SL/pV-S1, SL/pV-S1 and SL/pV-N, SL/pV, H120 (IB attenuated live vaccine), or PBS. Intestinal samples were prepared at 3 weeks postboosting vaccination. Intestinal extracts (diluted 1:2) were used as primary antibodies, and HRP-conjugated rabbit anti-chicken IgA (Sigma) antibodies were used as secondary antibodies. Anti-IBV IgA antibody titers in intestinal washes were determined by ELISA. Data represent the sample mean (n = 5) ± standard deviation. **, significant difference at P < 0.01.