These vaccines either required repeated administration or induced insufficient immune responses for long-lasting protection against lethal challenges with virulence Salmonella strains [7]. Many Salmonella vaccine strains carry deletion mutations affecting metabolic functions or virulence factors [8]. Several mutant strains of Salmonella have been investigated in the pursuit to develop optimal immune responses [9–11]. Our approach in constructing a live-attenuated Salmonella vaccine strain is to create a mutant defective in tRNA modification [12]. This strategy enables

our vaccine strain to express multiple virulence factors at a significantly reduced level in order to obtain a safe and immunogenic vaccine candidate. Glucose-inhibited division (GidA) protein (also known as MnmG) was first described in Escherichia coli, where deletion of gidA resulted in a filamentous morphology when #selleck compound randurls[1|1|,|CHEM1|]# grown in a rich medium supplemented with glucose [13]. Further studies showed GidA is a flavin dinucleotide (FAD) binding enzyme

involved in the fruiting body development of Myxococcus xanthus[14]. Furthermore, GidA has been shown to be a tRNA modification methylase in E. coli that forms a heterodimeric complex with MnmE (also known as TrmE) to catalyze the addition of a carboxymethylaminomethyl (cmnm) group at the 5 position of the wobble uridine (U34) HMPL-504 nmr of tRNAs [15–19]. Most importantly, deletion of gidA has been shown to attenuate the pathogenesis of some bacteria including Pseudomonas syringae, Aeromonas hydrophila, Streptococcus pyogenes, and Pseudomonas aeruginosa[20–23]. Our previous studies suggest a role for GidA in the regulation of Salmonella virulence and cell division [12, 24].

In our initial study, the gidA mutant was attenuated in vitro and showed a significant decrease in ability to invade T84 intestinal epithelial cells as well Ribociclib molecular weight as a significant decrease in ability to replicate and produce cytotoxic affects on macrophages. Furthermore, global transcriptional and proteomic profiling indicated a significant down-regulation in numerous genes and proteins involved in Salmonella pathogenesis [12]. Most importantly, the gidA mutant was attenuated in mice as shown by a significant increase in 50% lethal dose (LD50), reduced systemic bacterial survival, defective in the induction of inflammatory cytokines and chemokines, and reduced severity of histopathological lesions in the liver and spleen. Additionally, mice immunized with the gidA mutant were protected from a lethal dose challenge of wild-type (WT) STM [12]. In this study, we examined the relative contribution of the humoral and cellular immune responses in the overall protective mechanism afforded by immunization with the gidA mutant STM strain to further evaluate it as a candidate for use in a live-attenuated vaccine.