Recombinant Salmonella vaccination technology and its application to human bacterial pathogens

Salmonella enterica is a Gram-negative intracellular bacterial pathogen which causes salmonellosis in humans and animals. During the past several decades, extensive studies have shown that the attenuated Salmonella vaccine vector is an optimal vehicle for delivering passenger antigens to mucosal sites to induce humoral, cellular, and mucosal immunity. This immunity leads to protection against challenges with the wild-type pathogens from which the passenger antigens were derived. A myriad of studies have demonstrated that using attenuated Salmonella vaccines for recombinant multivalent vaccine construction has multiple advantages. In this review, we summarize these advantages and further evaluate the Salmonella-based vaccines against five bacterial diseases. Four of these are Gram-negative pathogens- Escherichia coli, Helicobacter pylori, Shigella dysenteriae, and Yersinia pestis-and one is a mycobacterial pathogen, Mycobacterium tuberculosis. Apart from H. pylori, the Salmonella-based vaccines against the other four pathogens exhibit excellent performance in safety, immunogenicity, and protection. These properties qualify them to be as a new generation of vaccines for preventing infections from bacterial pathogens.