Immunity to Salmonella

Salmonella enterica infections cause a spectrum of syndromes ranging between a self-limiting gastroenteritis to devastating, often fatal, systemic infections that have helped shape human history. Included in these are typhoid, and invasive nontyphoidal salmonellosis (iNTS), which both occur predominantly in developing/tropical countries. While typhoid can impact most age groups, iNTS is largely restricted to infants and those of any age with concurrent HIV/AIDS. Since the severity of disease caused by Salmonella is largely dependent upon the level of systemic spread, it provides a model to understand how pathogens cause harm. In this article, the immunological parameters associated with these infections will be discussed, with the distinct relationships between the pathogen, the microflora, the innate immune system, and the adaptive immune system considered. Finally, the role of vaccination in controlling Salmonella infections is outlined. Since there are three distinct vaccine types against typhoid, Salmonella infections provide a model to elucidate how vaccines protect against intracellular infections. Collectively, the insights we gain from studying infections caused by this genus, and our responses to them, provide a window into understanding how the different elements of the immune system collaborate to control infection.