scholarly journals Toll-Like Receptor 5-Deficient Mice Have Dysregulated Intestinal Gene Expression and Nonspecific Resistance to Salmonella-Induced Typhoid-Like Disease

2008 ◽  
Vol 76 (3) ◽  
pp. 1276-1281 ◽  
Author(s):  
Matam Vijay-Kumar ◽  
Jesse D. Aitken ◽  
Amrita Kumar ◽  
Andrew S. Neish ◽  
Satoshi Uematsu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Salmonella Enterica ◽  
Host Recognition ◽  
Toll Like Receptor ◽  
Defense Gene Expression ◽  
Nonspecific Resistance ◽  
Serovar Typhimurium ◽  
Toll Like Receptor 5

ABSTRACT The recognition of flagellin by Toll-like receptor 5 (TLR5) is the dominant means by which model intestinal epithelia activate proinflammatory gene expression in response to Salmonella enterica. The role of the flagellin-TLR5 interaction in vivo has been addressed primarily via studies that use flagellar mutants. Such studies suggest that host recognition of flagellin promotes rapid neutrophil recruitment that protects the host from this pathogen. However, these works do not directly address the role of TLR5 and are subject to the caveat that flagellar mutations may broadly affect Salmonella gene expression. Thus, we examined the role of the flagellin-TLR5 interaction via the use of TLR5-deficient (TLR5KO) mice. We utilized both the traditional model of murine Salmonella infection, wherein low-dose oral infection of mice with Salmonella enterica subsp. enterica serovar Typhimurium results in systemic typhoid-like disease, and a more recently characterized model in which mice are pretreated with streptomycin to result in gut-restricted acute enteritis. In the enteritis model, TLR5KO mice had more severe gut pathology, thus “phenocopying” previous results obtained with Salmonella mutants. In contrast, TLR5KO mice were resistant to Salmonella-induced typhoid-like disease. However, such resistance was not specific for flagellated serovar Typhimurium, but rather, TLR5KO mice were also resistant to challenges by flagellin-deficient serovar Typhimurium. Such resistance associated with elevations in the microbiota was ablated by antibiotic pretreatment and correlated with basal elevations in intestinal host defense gene expression. All together, these results indicate that the resistance of TLR5KO mice to Salmonella-induced typhoid-like illness resulted from alterations in their basal phenotype rather than from the lack of TLR5 ligation during the infection per se.

scholarly journals Flagella and Chemotaxis Are Required for Efficient Induction of Salmonella enterica Serovar Typhimurium Colitis in Streptomycin-Pretreated Mice

2004 ◽  
Vol 72 (7) ◽  
pp. 4138-4150 ◽  
Author(s):  
Bärbel Stecher ◽  
Siegfried Hapfelmeier ◽  
Catherine Müller ◽  
Marcus Kremer ◽  
Thomas Stallmach ◽  
...  
Keyword(s):  
Virulence Factors ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Innate Immune ◽  
Gastrointestinal Infections ◽  
Infection Models ◽  
Serovar Typhimurium ◽  
Efficient Induction ◽  
Toll Like Receptor 5

ABSTRACT Salmonella enterica subspecies 1 serovar Typhimurium is a common cause of gastrointestinal infections. The host's innate immune system and a complex set of Salmonella virulence factors are thought to contribute to enteric disease. The serovar Typhimurium virulence factors have been studied extensively by using tissue culture assays, and bovine infection models have been used to verify the role of these factors in enterocolitis. Streptomycin-pretreated mice provide an alternative animal model to study enteric salmonellosis. In this model, the Salmonella pathogenicity island 1 type III secretion system has a key virulence function. Nothing is known about the role of other virulence factors. We investigated the role of flagella in murine serovar Typhimurium colitis. A nonflagellated serovar Typhimurium mutant (fliGHI) efficiently colonized the intestine but caused little colitis during the early phase of infection (10 and 24 h postinfection). In competition assays with differentially labeled strains, the fliGHI mutant had a reduced capacity to get near the intestinal epithelium, as determined by fluorescence microscopy. A flagellated but nonchemotactic cheY mutant had the same virulence defects as the fliGHI mutant for causing colitis. In competitive infections, both mutants colonized the intestine of streptomycin-pretreated mice by day 1 postinfection but were outcompeted by the wild-type strain by day 3 postinfection. Together, these data demonstrate that flagella are required for efficient colonization and induction of colitis in streptomycin-pretreated mice. This effect is mostly attributable to chemotaxis. Recognition of flagellar subunits (i.e., flagellin) by innate immune receptors (i.e., Toll-like receptor 5) may be less important.

scholarly journals The enzyme phosphoglucomutase (Pgm) is required by Salmonella enterica serovar Typhimurium for O-antigen production, resistance to antimicrobial peptides and in vivo fitness

Microbiology ◽  
2009 ◽  
Vol 155 (10) ◽  
pp. 3403-3410 ◽  
Author(s):  
G. K. Paterson ◽  
D. B. Cone ◽  
S. E. Peters ◽  
D. J. Maskell
Keyword(s):  
Antimicrobial Peptides ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Live Attenuated Vaccine ◽  
Antigen Production ◽  
O Antigen ◽  
Serovar Typhimurium

The enzyme phosphoglucomutase (Pgm) catalyses the interconversion of glucose 1-phosphate and glucose 6-phosphate and contributes to glycolysis and the generation of sugar nucleotides for biosynthesis. To assess the role of this enzyme in the biology of the pathogen Salmonella enterica serovar Typhimurium we have characterized a pgm deletion mutant in strain SL1344. Compared to SL1344, SL1344 pgm had impaired growth in vitro, was deficient in the ability to utilize galactose as a carbon source and displayed reduced O-antigen polymer length. The mutant was also more susceptible to antimicrobial peptides and showed decreased fitness in the mouse typhoid model. The in vivo phenotype of SL1344 pgm indicated a role for pgm in the early stages of infection, most likely through deficient O-antigen production. Although pgm mutants in other pathogens have potential as live attenuated vaccine strains, SL1344 pgm was not sufficiently attenuated for such use.

HEPATOCYTE TOLL-LIKE RECEPTOR 2 EXPRESSION IN VIVO AND IN VITRO: ROLE OF CYTOKINES IN INDUCTION OF RAT TLR2 GENE EXPRESSION BY LIPOPOLYSACCHARIDE

Shock ◽  
2000 ◽  
Vol 14 (3) ◽  
pp. 361-365 ◽  
Author(s):  
Shubing Liu ◽  
Neil A. Salyapongse ◽  
David A. Geller ◽  
Yoram Vodovotz ◽  
Timothy R. Billiar
Keyword(s):  
Gene Expression ◽  
Toll Like Receptor ◽  
Tlr2 Gene ◽  
Toll Like Receptor 2

scholarly journals Aggregation via the Red, Dry, and Rough Morphotype Is Not a Virulence Adaptation in Salmonella enterica Serovar Typhimurium

2008 ◽  
Vol 76 (3) ◽  
pp. 1048-1058 ◽  
Author(s):  
A. P. White ◽  
D. L. Gibson ◽  
G. A. Grassl ◽  
W. W. Kay ◽  
B. B. Finlay ◽  
...  
Keyword(s):  
In Vivo Imaging ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Primary Role ◽  
Wild Type ◽  
Serovar Typhimurium ◽  
Cell Densities ◽  
Two Populations

ABSTRACT The Salmonella rdar (red, dry, and rough) morphotype is an aggregative and resistant physiology that has been linked to survival in nutrient-limited environments. Growth of Salmonella enterica serovar Typhimurium was analyzed in a variety of nutrient-limiting conditions to determine whether aggregation would occur at low cell densities and whether the rdar morphotype was involved in this process. The resulting cultures consisted of two populations of cells, aggregated and nonaggregated, with the aggregated cells preferentially displaying rdar morphotype gene expression. The two groups of cells could be separated based on the principle that aggregated cells were producing greater amounts of thin aggregative fimbriae (Tafi or curli). In addition, the aggregated cells retained some physiological characteristics of the rdar morphotype, such as increased resistance to sodium hypochlorite. Competitive infection experiments in mice showed that nonaggregative ΔagfA cells outcompeted rdar-positive wild-type cells in all tissues analyzed, indicating that aggregation via the rdar morphotype was not a virulence adaptation in Salmonella enterica serovar Typhimurium. Furthermore, in vivo imaging experiments showed that Tafi genes were not expressed during infection but were expressed once Salmonella was passed out of the mice into the feces. We hypothesize that the primary role of the rdar morphotype is to enhance Salmonella survival outside the host, thereby aiding in transmission.

scholarly journals Inhibition of Salmonella enterica Serovar Typhimurium Lipopolysaccharide Deacylation by Aminoarabinose Membrane Modification

2005 ◽  
Vol 187 (7) ◽  
pp. 2448-2457 ◽  
Author(s):  
Kiyoshi Kawasaki ◽  
Robert K. Ernst ◽  
Samuel I. Miller
Keyword(s):  
Outer Membrane ◽  
Salmonella Enterica ◽  
Lipid A ◽  
Bacterial Resistance ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Host Recognition ◽  
Membrane Modification ◽  
Serovar Typhimurium ◽  
Nonionic Detergent

ABSTRACT Salmonella enterica serovar Typhimurium remodels the lipid A component of lipopolysaccharide, a major component of the outer membrane, to survive within animals. The activation of the sensor kinase PhoQ in host environments increases the synthesis of enzymes that deacylate, palmitoylate, hydroxylate, and attach aminoarabinose to lipid A, also known as endotoxin. These modifications promote bacterial resistance to antimicrobial peptides and reduce the host recognition of lipid A by Toll-like receptor 4. The Salmonella lipid A 3-O-deacylase, PagL, is an outer membrane protein whose expression is regulated by PhoQ. In S. enterica serovar Typhimurium strains that had the ability to add aminoarabinose to lipid A, 3-O-deacylated lipid A species were not detected, despite the PhoQ induction of PagL protein expression. In contrast, strains defective for the aminoarabinose modification of lipid A demonstrated in vivo PagL activity, indicating that this membrane modification inhibited PagL's enzymatic activity. Since not all lipid A molecules are modified with aminoarabinose upon PhoQ activation, these results cannot be ascribed to the substrate specificity of PagL. PagL-dependent deacylation was detected in sonically disrupted membranes and membranes treated with the nonionic detergent n-octyl-β-d-glucopyranoside, suggesting that perturbation of the intact outer membrane releases PagL from posttranslational inhibition by aminoarabinose-containing membranes. Taken together, these results suggest that PagL enzymatic deacylation is posttranslationally inhibited by membrane environments, which either sequester PagL from its substrate or alter its conformation.

scholarly journals Role of FimW, FimY, and FimZ in Regulating the Expression of Type I Fimbriae in Salmonella enterica Serovar Typhimurium

2009 ◽  
Vol 191 (9) ◽  
pp. 3003-3010 ◽  
Author(s):  
Supreet Saini ◽  
Jeffrey A. Pearl ◽  
Christopher V. Rao
Keyword(s):  
Gene Expression ◽  
Negative Feedback ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Phase Variation ◽  
Type I ◽  
Serovar Typhimurium ◽  
Type I Fimbriae ◽  
Positive And Negative Feedback

ABSTRACT Type I fimbriae in Salmonella enterica serovar Typhimurium are surface appendages that facilitate binding to eukaryotic cells. Expression of the fim gene cluster is known to be regulated by three proteins—FimW, FimY, and FimZ—and a tRNA encoded by fimU. In this work, we investigated how these proteins and tRNA coordinately regulate fim gene expression. Our results indicate that FimY and FimZ independently activate the P fimA promoter which controls the expression of the fim structural genes. FimY and FimZ were also found to strongly activate each other's expression and weakly activate their own expression. FimW was found to negatively regulate fim gene expression by repressing transcription from the P fimY promoter, independent of FimY or FimZ. Moreover, FimW and FimY interact within a negative feedback loop, as FimY was found to activate the P fimW promoter. In the case of fimU, the expression of this gene was not found to be regulated by FimW, FimY, or FimZ. We also explored the effect of fim gene expression on Salmonella pathogenicity island 1 (SPI1). Our results indicate that FimZ alone is able to enhance the expression of hilE, a known repressor of SPI1 gene expression. Based on our results, we were able to propose an integrated model for the fim gene circuit. As this model involves a combination of positive and negative feedback, we hypothesized that the response of this circuit may be bistable and thus a possible mechanism for phase variation. However, we found that the response was continuous and not bistable.

scholarly journals Increased Susceptibility of C1q-Deficient Mice to Salmonella enterica Serovar Typhimurium Infection

2002 ◽  
Vol 70 (2) ◽  
pp. 551-557 ◽  
Author(s):  
Joanna Warren ◽  
Pietro Mastroeni ◽  
Gordon Dougan ◽  
Mahdad Noursadeghi ◽  
Jonathan Cohen ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Fluorescent Protein ◽  
Alternative Pathway ◽  
No Production ◽  
Classical Pathway ◽  
Serovar Typhimurium ◽  
Deficient Mice

ABSTRACT The role of the complement system in host defense against Salmonella infection is poorly defined. Bacterial cell wall O-antigen polysaccharide can activate the alternative pathway in vitro. No studies, however, have elucidated the role of the classical pathway in immunity to Salmonella spp. in vivo. C1q-deficient mice (C1qa −/−) on a 129/Sv genetic background and strain-matched controls were infected intraperitoneally and intravenously with Salmonella enterica serovar Typhimurium and monitored over a 14-day period. After inoculation by either route, the C1qa −/− mice were found to be significantly more susceptible to Salmonella infection. Hepatic and splenic bacterial counts, performed at various time points, showed increased numbers of colonies in complement-deficient mice compared to controls. Analysis of blood clearance showed no difference between the two experimental groups during the first 15 min. However, after 20 min and until 6 h postinfection, numbers of circulating bacteria were significantly higher in complement-deficient mice. In vitro experiments using either resident or thioglycolate-elicited peritoneal macrophages showed a significant increase in the number of bacteria inside C1q-deficient macrophages compared to controls irrespective of the serum used for opsonizing the bacteria. These findings could not be explained either by an increased bacterial uptake, analyzed in vitro and in vivo using green fluorescent protein-tagged salmonellae, or by a defect in the respiratory burst or in NO production. The data presented here suggest the possibility of novel pathways by which C1q may modulate the pathogenesis of infectious diseases caused by intracellular pathogens.

scholarly journals Toll-Like Receptor 5-Dependent Regulation of Inflammation in Systemic Salmonella enterica Serovar Typhimurium Infection

2009 ◽  
Vol 77 (9) ◽  
pp. 4121-4129 ◽  
Author(s):  
Bénédicte Fournier ◽  
Ifor R. Williams ◽  
Andrew T. Gewirtz ◽  
Andrew S. Neish
Keyword(s):  
Salmonella Enterica ◽  
Cell Types ◽  
Surface Expression ◽  
Leukocyte Recruitment ◽  
Mucosal Inflammation ◽  
Toll Like Receptor ◽  
Necrosis Factor Alpha ◽  
Serovar Typhimurium ◽  
Disease Parameter ◽  
Toll Like Receptor 5

ABSTRACT Salmonella enterica, a gram-negative pathogen, causes a spectrum of human infections including enterocolitis and typhoid fever. We previously showed that Salmonella flagellin played a role in suppressing intestinal mucosal inflammation in a murine model of acute enterocolitis. In this study, we examined the role of flagellin in the typhoid-like systemic murine Salmonella infection by measuring bacterial proliferation, inflammation, leukocyte recruitment, and cellular apoptosis in Peyer's patches (PPs), mesenteric lymph node (MLN), and spleen. We found that relative to an isogenic wild-type (WT) strain, aflagellate Salmonella exhibited increased proliferation at 4 days postinfection in PPs and MLN but not spleen. The aflagellate mutant also elicited increased local and systemic secretion of inflammatory cytokines such as interleukin-1β, gamma interferon, and tumor necrosis factor alpha and enhanced surface expression of ICAM-1 on macrophages and dendritic cells (DCs). Furthermore, the recruitment of macrophages and DCs in PPs and MLN, but not spleen, was enhanced upon infection with aflagellate Salmonella. The relative differences between WT and aflagellate Salmonella were highly attenuated in Toll-like receptor 5-deficient (TLR5−/−) mice, indicating involvement of TLR5-dependent signaling. Interestingly, infection with the aflagellate mutant also resulted in decreased levels of T-cell apoptosis in PPs relative to infection with WT Salmonella. We postulate that the initial lack of detection of the aflagellate mutant in the mucosa permits increased proliferation within the host and enhances inflammatory signaling in nonepithelial cell types, which subsequently promotes leukocyte recruitment. In contrast, lack of difference in any disease parameter measured in the spleen likely reflects that Salmonella expression of flagellin is downregulated in this organ. Thus, the characteristic inflammatory pathology of Salmonella infection occurs only in PPs and to a lesser extent in MLN during the initial phases of infection and these early responses are dependent on TLR5.

scholarly journals Role of Mouse Peptidoglycan Recognition Protein PGLYRP2 in the Innate Immune Response to Salmonella enterica Serovar Typhimurium InfectionIn Vivo

2012 ◽  
Vol 80 (8) ◽  
pp. 2645-2654 ◽  
Author(s):  
Jooeun Lee ◽  
Kaoru Geddes ◽  
Catherine Streutker ◽  
Dana J. Philpott ◽  
Stephen E. Girardin
Keyword(s):  
Salmonella Enterica ◽  
Fluorescent Protein ◽  
Intraepithelial Lymphocytes ◽  
Innate Immune ◽  
Th17 Response ◽  
Content Type ◽  
Serovar Typhimurium

ABSTRACTPeptidoglycan recognition proteins (PGRPs) are a family of innate pattern recognition molecules that bind bacterial peptidoglycan. While the role of PGRPs inDrosophilainnate immunity has been extensively studied, how the four mammalian PGRP proteins (PGLYRP1 to PGLYRP4) contribute to host defense against bacterial pathogensin vivoremains poorly understood. PGLYRP1, PGLYRP3, and PGLYRP4 are directly bactericidalin vitro, whereas PGLYRP2 is anN-acetylmuramyl-l-alanine amidase that cleaves peptidoglycan between the sugar backbone and the peptide stem. Because PGLYRP2 cleaves muramyl peptides detected by host peptidoglycan sensors Nod1 and Nod2, we speculated that PGLYRP2 may act as a modifier of Nod1/Nod2-dependent innate immune responses. We investigated the role of PGLYRP2 inSalmonella entericaserovar Typhimurium-induced colitis, which is regulated by Nod1/Nod2 through the induction of an early Th17 response. PGLYRP2 did not contribute to expression of Th17-associated cytokines, interleukin-22 (IL-22)-dependent antimicrobial proteins, or inflammatory cytokines. However, we found thatPglyrp2-deficient mice displayed significantly enhanced inflammation in the cecum at 72 h postinfection, reflected by increased polymorphonuclear leukocyte (PMN) infiltration and goblet cell depletion.Pglyrp2expression was also induced in the cecum ofSalmonella-infected mice, and expression of green fluorescent protein under control of thePglyrp2promoter was increased in discrete populations of intraepithelial lymphocytes. Lastly,Nod2−/−Pglyrp2−/−mice displayed increased susceptibility to infection at 24 h postinfection compared toPglyrp2−/−mice, which correlated with increased PMN infiltration and submucosal edema. Thus, PGLYRP2 plays a protective rolein vivoin the control ofS. Typhimurium infection through a Nod1/Nod2-independent mechanism.

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