Heterologous protection in pigs induced by a plasmid-cured andcrpgene-deletedSalmonella choleraesuislive vaccine

In this study, we exploited acrp(cAMP receptor protein) gene-deleted, virulence plasmid-curedSalmonella choleraesuismutant with decreased carbon source utilization, designatedS.C.-Δcrp/vpl-, as a live vaccine strain. Normal weight gain with no clinical signs was observed in pigs immunized with high doses ofS.C.-Δcrp/vpl-live vaccine. Vaccination in pregnant sows induced high maternal antibodies, which could prevent piglets fromSalmonellainfection. Moreover, serial transmission of the vaccine strain in piglets produced no evidence of reversion to virulence. Furthermore, the peripheral blood mononuclear cells from immunized piglets also developedSalmonellaspecific T-cell proliferative responsein vitro. Our results indicate that immunogenic antigens inS.C.-Δcrp/vpl-can induce adequate immunity to protect pigs against challenge with a heterologous virulent strain. Thus, this mutant holds promise for the development of a new liveS. choleraesuisvaccine.