Serum IgG responses to SaoA (A), nasal IgA responses to SaoA (B), serum IgG responses to
Choleraesuis OMPs (C) in ten pigs were measured by ELISA. The data represent reciprocal anti-IgG antibody titers from the piglets orally immunized with attenuated Salmonella carrying either pS-SaoA and pYA3493 at the indicated weeks after immunization. Serum and nasal cavity wash obtained from individual pig were serially diluted to obtain titers, starting from either 1:50 or 1:10. Error bars represent variation between different pigs. Significant differences were indicated. **P < 0.01, for Salmonella Choleraesuis with pS-SaoA compare to Salmonella Choleraesuis with pYA3493 in A and B; #
P < 0.05; ##
P < 0.01, for Salmonella carrying either pS-SaoA or pYA3493 compared each other. No responses were detected to antigen tested in pigs immunized with BSG or in pre-immune sera from vaccinated piglets. ELISA was performed twice with identical results.