Background Payers of health services and policymakers place a major focus on cost containment in health care.

Background S. Typhi, a human-restricted Salmonella enterica serovar, causes a systemic intracellular infection in humans (typhoid fever). In comparison, S. Typhimurium causes gastroenteritis in humans, but causes a systemic typhoidal illness in mice. The PhoP regulon is a well studied two component (PhoP/Q) coordinately regulated network of genes whose expression is required for intracellular survival of S. enterica.Methodology/Principal FindingsUsing high performance liquid chromatography mass spectrometry (HPLC-MS/MS), we examined the protein expression profiles of three sequenced S. enterica strains: S. Typhimurium LT2, S. Typhi CT18, and S. Typhi Ty2 in PhoP-inducing and non-inducing conditions in vitro and compared these results to profiles of phoP−/Q− mutants derived from S. Typhimurium LT2 and S. Typhi Ty2. Our analysis identified 53 proteins in S. Typhimurium LT2 and 56 proteins in S. Typhi that were regulated in a PhoP-dependent manner. As expected, many proteins identified in S. Typhi demonstrated concordant differential expression with a homologous protein in S. Typhimurium. However, three proteins (HlyE, STY1499, and CdtB) had no homolog in S. Typhimurium. HlyE is a pore-forming toxin. STY1499 encodes a stably expressed protein of unknown function transcribed in the same operon as HlyE. CdtB is a cytolethal distending toxin associated with DNA damage, cell cycle arrest, and cellular distension. Gene expression studies confirmed up-regulation of mRNA of HlyE, STY1499, and CdtB in S. Typhi in PhoP-inducing conditions.Conclusions/SignificanceThis study is the first protein expression study of the PhoP virulence associated regulon using strains of Salmonella mutant in PhoP, has identified three Typhi-unique proteins (CdtB, HlyE and STY1499) that are not present in the genome of the wide host-range Typhimurium, and includes the first protein expression profiling of a live attenuated bacterial vaccine studied in humans (Ty800).

Vibrio cholerae causes a dehydrating diarrheal illness that can be rapidly fatal in the absence of specific treatment. The organism is an historic scourge and, like similar infectious diseases, may have influenced the evolution of the human genome. We report here the results of the first candidate gene association study of cholera. In a family-based study of 76 pedigrees from Dhaka, Bangladesh, we evaluated the association between cholera and five candidate genes -- the cystic fibrosis transmembrane receptor; lactoferrin; long palate, lung and nasal epithelium clone 1 (LPLUNC1); estrogen related receptor alpha; and calcium activated chloride channel 1. We found a significant association with a marker in the promoter region of LPLUNC1 (rs11906665), a member of a family of evolutionarily conserved innate immunity proteins. A previous microarray-based study of duodenal biopsies revealed significantly increased expression of LPLUNC1 in cholera patients compared to healthy control subjects. Our results suggest that variation in host innate immune responses may influence the outcome of exposure to V. cholerae in an endemic setting.

An effective vaccine for Vibrio choleraeis not yet available for use in the developing world, where the burden of cholera disease is highest. Characterizing the proteins that are expressed by V. cholerae in the human host environment may provide insight into the pathogenesis of cholera and assist with the development of an improved vaccine. We analyzed the V. cholerae proteins present in the stools of 32 patients with clinical cholera. The V. cholerae outer membrane porin, OmpU, was identified in all of the human stool samples, and many V. cholerae proteins were repeatedly identified in separate patient samples. The majority of V. cholerae proteins identified in human stool are involved in protein synthesis and energy metabolism. A number of proteins involved in the pathogenesis of cholera, including the A and B subunits of cholera toxin and the toxincoregulated pilus, were identified in human stool. In a subset of stool specimens, we also assessed which in vivo expressed V. cholerae proteins were recognized uniquely by convalescent-phase as opposed to acute-phase serum from cholera patients. We identified a number of these in vivo expressed proteins as immunogenic during human infection. To our knowledge, this is the first characterization of the proteome of a pathogenic bacteria recovered from a natural host.Vibrio cholerae is a gram-negative bacillus that exists within an aquatic reservoir and that can cause severe, dehydrating, and occasionally fatal diarrhea in humans (11). Strains of V. cholerae are differentiated serologically by the O side chain of lipopolysaccharide, and the majority of toxigenic strains belong to serogroup O1 or O139. V. cholerae O1 occurs in two biotypes, classical and El Tor, which differ in biochemical characteristics and phage susceptibility. Since 1817, there have been seven cholera pandemics during which disease has spread from the Indian subcontinent across Asia, Europe, Africa, and the Western Hemisphere. The disease is also endemic in floodprone regions of South Asia, such as Bangladesh, where seasonal outbreaks typically occur in the spring and fall. The ongoing seventh pandemic of cholera is due to the O1 El Tor biotype of V. cholerae, and more than 100,000 diarrheal deaths per year are attributed to infection with this organism. Although a number of cholera vaccines have been developed over the past 100 years, an effective vaccine is not yet available for use in the developing world, where the burden of disease is highest (21).Humans are the only known host and reservoir for V. cholerae outside its aquatic environment, and an important limitation to the development and testing of cholera vaccines has been the lack of an optimal animal model of infection. It is consequently of great interest to understand which virulence factors are expressed by the organism directly in the human host environment, since in vivo expressed antigens of V. cholerae may represent targets of protective human immune responses. The capacity to perform such research has been facilitated by the sequen...