Location: Agroecosystems Management ResearchTitle: Salmonella DIVA vaccine reduces disease, colonization and shedding due to virulent S. Typhimurium infection in swine Author
|Bearson, Bradley - Brad|
|Lee, In Soo - Hannam University|
|Kich, Jalusa - Embrapa-Pigs And Poultry|
Submitted to: Journal of Medical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2017
Publication Date: 5/18/2017
Citation: Bearson, B.L., Bearson, S.M., Brunelle, B.W., Bayles, D.O., Lee, I., Kich, J.D. 2017. Salmonella DIVA vaccine reduces disease, colonization and shedding due to virulent S. Typhimurium infection in swine. Journal of Medical Microbiology. 66:651-661. doi: 10.1099/jmm.0.000482.
Interpretive Summary: In swine production worldwide, Salmonella is endemic, often colonizing animals without signs of clinical disease. Asymptomatic Salmonella colonization of pigs is a food safety issue because the human pathogen can be introduced into the food supply through contaminated meat. To limit Salmonella colonization in pigs, control methods should be applied early in the animal production system, including vaccination. In the current study, a vaccine designed and created by our research group limited clinical symptoms (fever) and reduced tissue colonization and fecal shedding of Salmonella in vaccinated pigs. In response to the vaccination, immune genes were differentially-expressed, indicating that immunity was induced in the vaccinated pigs. As part of a comprehensive swine management strategy, vaccination of pigs will protect animal health, reduce shedding into the environment, and enhance food safety by limiting the transmission of this important foodborne pathogen from pen to plate.
Technical Abstract: Non-host adapted Salmonella serovars are opportunistic pathogens that can colonize food-producing animals without causing overt disease, including the frequent foodborne pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium). Interventions against Salmonella need to both enhance food safety and protect animal health. We previously described an attenuated S. Typhimurium vaccine (BBS 866) that provided cross-protection against the swine pathogen S. Choleraesuis while allowing the differentiation of infected from vaccinated animals (DIVA). In this report, we further characterize the vaccine following challenge of pigs with virulent S. Typhimurium. Vaccination significantly reduced fever and interferon-gamma (IFN') levels in swine challenged with virulent S. Typhimurium compared to mock-vaccinated pigs. Salmonella fecal shedding and gastrointestinal tissue colonization were also significantly reduced in vaccinated swine. RNA-Seq analysis comparing BBS 866 to its parental S. Typhimurium strain demonstrated a decrease in expression of genes involved in cellular invasion and bacterial motility; a concurrent phenotypic decline in invasion of porcine-derived IPEC-J2 cells and swimming motility for the vaccine strain is consistent with the RNA-Seq analysis. Numerous membrane proteins were also differentially expressed, an anticipated gene expression pattern due to the targeted deletion of several small RNAs and the rfaH gene in the vaccine strain. The porcine response to vaccination, as measured by RNA-Seq, indicated that genes involved in the immune and inflammatory response were differentially regulated at 2 days post-vaccination compared to pre-vaccination. Collectively, evaluation of the S. Typhimurium DIVA vaccine indicates that vaccination will provide both swine health and food safety benefits.