Table 1.

Description of S. Typhi strains used in the manuscript.

Serovar Typhi strain	Parent strain	Relevant phenotype	Metabolic pathway affected	Phenotype in vitro	Field/Clinical trial performance
Ty2	Wild-type	–	–	Rapid multiplication	No or short lived protection
Ty21a	Ty2	Chemical mutagenesis	Several critical metabolic pathways, such as galactose metabolism, synthesis of isoleucine, valine, and Vi-capsular PS (see text for details)	Limited multiplication	Up to 7 years of protection
CVD 908	Ty2	ΔaroC ΔaroD	Biosynthesis of aromatic aa	Limited multiplication	Immunogenic but with clinically silent, self-limited vaccine bacteremia
CVD 909	Ty2 CVD 908-htrA	ΔaroC ΔaroD ΔhtrA Ptac-tviA	Biosynthesis of aromatic aa and heat-shock protein. Constitutively express Vi	Limited multiplication	Immunogenic
CVD 910	Ty2 CVD 908-htrA	ΔguaBA ΔhtrA	Biosynthesis of heat-shock protein Biosynthesis of guanine nucleotides	Limited multiplication	No clinical trials
CVD 915	Ty2	ΔguaBA	Biosynthesis of guanine nucleotides	Limited multiplication	No clinical trials