Conversion of RpoS ⁻ Attenuated Salmonella enterica Serovar Typhi Vaccine Strains to RpoS ⁺ Improves Their Resistance to Host Defense Barriers

Recombinant attenuated Salmonella vaccines (RASVs) represent a unique prevention strategy to combating infectious disease because they utilize the ability of Salmonella to invade and colonize deep effector lymphoid tissues and deliver hetero- and homologous derived antigens at the lowest immunizing dose. Our recent clinical trial in human volunteers indicated that an RpoS + derivative of Ty2 was better at inducing immune responses than its RpoS − counterpart. In this study, we demonstrate that a functional RpoS allele is beneficial for developing effective live attenuated vaccines against S . Typhi or in using S . Typhi as a recombinant attenuated vaccine vector to deliver other protective antigens.