Protective immunity to Salmonella enterica is partially serogroup specific

Pre-harvest reduction of Salmonella carriage by swine would benefit both animal health and food quality. While vaccination is an attractive pre-harvest intervention to reduce Salmonella levels in swine, the large number of potential Salmonella enterica serovars found in swine makes it critical that vaccines provide broad serotype efficacy. In order to directly compare the relative efficacy of Salmonella vaccines against serogroup-matched and serogroup-unmatched Salmonella, we vaccinated pigs with two commercially available Salmonella vaccines (either serogroup B or serogroup C1) and challenged with serovar-matched, serogroup-matched or serogroup-unmatched challenge strains. We found that while serogroup-matched vaccines provided relatively better efficacy than unmatched vaccines, serotype-unmatched vaccines also provided significant reduction of Salmonella carriage and shed. In addition, by measuring serogroup specific cell mediated (IFN-γ ELISPOT) and humoral (anti-LPS ELISA) immunity, we found that this serogroup specific efficacy correlates primarily with humoral immunity, while cell mediated immunity was mostly non-serogroup specific. While the practical relevance to pork quality of this serogroup-specific efficacy remains to be demonstrated, the large predominance of serogroup B Salmonella in swine suggests that a serogroup B Salmonella vaccine for swine would be of value to pre-harvest food safety interventions in swine.