Non-typhoidal Salmonella (NTS) is a significant source of foodborne illnesses globally, and the most prevalent serogroups linked with human disease are B, C1, C2-C3, and D. While this study and others have reported live vaccine candidates that protect against S. Typhimurium (serogroup B) and S. Enteritidis (serogroup D), considerably less work has been focused toward vaccines that target either serogroup C1 or C2-C3 Salmonella. In this paper, researchers report a live-attenuated vaccine based on Salmonella Newport (serogroup C2-C3). Previously employed in live vaccines to attenuate S. Typhimurium and/or S. Enteritidis, deletion of the genes clpX or rfaL failed to reduce S. Newport. In an intraperitoneal infection paradigm in BALB/c mice, however, loss of either guaBA or htrA increased the 50% fatal dosage of S. Newport. When given intraperitoneally or orally, our live-attenuated vaccine candidate CVD 1966 produced significant antibody responses against COPS, flagellin, and outer membrane proteins. Following fatal challenge with the parental virulent strain of S. Newport, we observed vaccination efficacies of 53% for intraperitoneal immunization and 47% for oral immunization.
Following intraperitoneal vaccination, the vaccine considerably decreased the bacterial load of challenge organisms in the liver and spleen. Interestingly, removing rfaL from the LPS chain did not result in a greater immune response to surface antigens and did not provide protection against fatal homologous challenges. Finally, researchers have created and are testing a live-attenuated Salmonella serogroup C2-C3 vaccine.
Reference: https://www.tandfonline.com/doi/full/10.1080/21645515.2018.1491499
