scholarly journals Enterohemorrhagic Escherichia coli O157:H7 Shiga Toxins Inhibit Gamma Interferon-Mediated Cellular Activation

2012 ◽  
Vol 80 (7) ◽  
pp. 2307-2315 ◽  
Author(s):  
Nathan K. Ho ◽  
Juan C. Ossa ◽  
Uma Silphaduang ◽  
Roger Johnson ◽  
Kathene C. Johnson-Henry ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Epithelial Cells ◽  
Tyrosine Phosphorylation ◽  
Cell Activation ◽  
Gamma Interferon ◽  
Enterohemorrhagic Escherichia Coli ◽  
Host Immune System ◽  
Content Type ◽  
Shiga Toxins ◽  
Ifn Γ

ABSTRACTEnterohemorrhagicEscherichia coli(EHEC) serotype O157:H7 is a food-borne pathogen that causes significant morbidity and mortality in developing and industrialized nations. EHEC infection of host epithelial cells is capable of inhibiting the gamma interferon (IFN-γ) proinflammatory pathway through the inhibition of Stat-1 phosphorylation, which is important for host defense against microbial pathogens. The aim of this study was to determine the bacterial factors involved in the inhibition of Stat-1 tyrosine phosphorylation. Human HEp-2 and Caco-2 epithelial cells were challenged directly with either EHEC or bacterial culture supernatants and stimulated with IFN-γ, and then the protein extracts were analyzed by immunoblotting. The data showed that IFN-γ-mediated Stat-1 tyrosine phosphorylation was inhibited by EHEC secreted proteins. Using two-dimensional difference gel electrophoresis, EHEC Shiga toxins were identified as candidate inhibitory factors. EHEC Shiga toxin mutants were then generated and complemented intrans, and mutant culture supernatant was supplemented with purified Stx to confirm their ability to subvert IFN-γ-mediated cell activation. We conclude that while other factors are likely involved in the suppression of IFN-γ-mediated Stat-1 tyrosine phosphorylation,E. coli-derived Shiga toxins represent a novel mechanism by which EHEC evades the host immune system.

scholarly journals Enterohemorrhagic Escherichia coli O157:H7 Disrupts Stat1-Mediated Gamma Interferon Signal Transduction in Epithelial Cells

2003 ◽  
Vol 71 (3) ◽  
pp. 1396-1404 ◽  
Author(s):  
Peter J. M. Ceponis ◽  
Derek M. McKay ◽  
Joyce C. Y. Ching ◽  
Perpetual Pereira ◽  
Philip M. Sherman
Keyword(s):  
Escherichia Coli ◽  
Signal Transduction ◽  
Epithelial Cells ◽  
Host Cell ◽  
Tyrosine Phosphorylation ◽  
Gamma Interferon ◽  
Enterohemorrhagic Escherichia Coli ◽  
Cell Protein ◽  
E Coli ◽  
Ifn Γ

ABSTRACT Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a clinically important bacterial enteropathogen that manipulates a variety of host cell signal transduction cascades to establish infection. However, the effect of EHEC O157:H7 on Jak/Stat signaling is unknown. To define the effect of EHEC infection on epithelial gamma interferon (IFN-γ)-Stat1 signaling, human T84 and HEp-2 epithelial cells were infected with EHEC O157:H7 and then stimulated with recombinant human IFN-γ. Cells were also infected with different EHEC strains, heat-killed EHEC, enteropathogenic E. coli (EPEC) O127:H6, and the commensal strain E. coli HB101. Nuclear and whole-cell protein extracts were prepared and were assayed by an electrophoretic mobility shift assay (EMSA) and by Western blotting, respectively. Cells were also processed for immunofluorescence to detect the subcellular localization of Stat1. The EMSA revealed inducible, but not constitutive, Stat1 activation upon IFN-γ treatment of both cell lines. The EMSA also showed that 6 h of EHEC O157:H7 infection, but not 30 min of EHEC O157:H7 infection, prevented subsequent Stat1 DNA binding induced by IFN-γ, whereas infection with EPEC did not. Immunoblotting showed that infection with EHEC, but not infection with EPEC, eliminated IFN-γ-induced Stat1 tyrosine phosphorylation in both dose- and time-dependent fashions and disrupted inducible protein expression of the Stat1-dependent gene interferon regulatory factor 1. Immunofluorescence revealed that EHEC infection did not prevent nuclear accumulation of Stat1 after IFN-γ treatment. Also, Stat1 tyrosine phosphorylation was suppressed by different EHEC isolates, including intimin-, type III secretion- and plasmid-deficient strains, but not by HB101 and heat-killed EHEC. These findings indicate the novel disruption of host cell signaling caused by EHEC infection but not by EPEC infection.

scholarly journals Identification of Antibiotics That Diminish Disease in a Murine Model of Enterohemorrhagic Escherichia coli Infection

2020 ◽  
Vol 64 (4) ◽  
Author(s):  
Sabrina Mühlen ◽  
Isabell Ramming ◽  
Marina C. Pils ◽  
Martin Koeppel ◽  
Jana Glaser ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Enterohemorrhagic Escherichia Coli ◽  
Content Type ◽  
Shiga Toxins ◽  
Escherichia Coli Infection ◽  
Uremic Syndrome ◽  
Severity Of The Disease ◽  
Selection Of ◽  
Mild Diarrhea

ABSTRACT Infections with enterohemorrhagic Escherichia coli (EHEC) cause disease ranging from mild diarrhea to hemolytic-uremic syndrome (HUS) and are the most common cause of renal failure in children in high-income countries. The severity of the disease derives from the release of Shiga toxins (Stx). The use of antibiotics to treat EHEC infections is generally avoided, as it can result in increased stx expression. Here, we systematically tested different classes of antibiotics and found that their influence on stx expression and release varies significantly. We assessed a selection of these antibiotics in vivo using the Citrobacter rodentium ϕstx2dact mouse model and show that stx2d-inducing antibiotics resulted in weight loss and kidney damage despite clearance of the infection. However, several non-Stx-inducing antibiotics cleared bacterial infection without causing Stx-mediated pathology. Our results suggest that these antibiotics might be useful in the treatment of EHEC-infected human patients and decrease the risk of HUS development.

scholarly journals Helicobacter pylori Disrupts STAT1-Mediated Gamma Interferon-Induced Signal Transduction in Epithelial Cells

2004 ◽  
Vol 72 (1) ◽  
pp. 537-545 ◽  
Author(s):  
David J. Mitchell ◽  
Hien Q. Huynh ◽  
Peter J. M. Ceponis ◽  
Nicola L. Jones ◽  
Philip M. Sherman
Keyword(s):  
Helicobacter Pylori ◽  
Epithelial Cells ◽  
Tyrosine Phosphorylation ◽  
Nuclear Translocation ◽  
Gamma Interferon ◽  
Cell Protein ◽  
Stat1 Signaling ◽  
Ifn Γ ◽  
H Pylori

ABSTRACT Infection with Helicobacter pylori is chronic despite a vigorous mucosal immune response characterized by gastric T-helper type 1 cell expansion and gamma interferon (IFN-γ) production. IFN-γ signals by activation and nuclear translocation of signal transducer and activator of transcription 1 (STAT1); however, the effect of H. pylori infection on IFN-γ-STAT1 signaling is unknown. We infected human gastric (MKN45 and AGS) and laryngeal (HEp-2) epithelial cell lines with type 1 and type 2 H. pylori strains and then stimulated them with IFN-γ. Western blotting of whole-cell protein extracts revealed that infection with live, but not heat-killed, H. pylori time-dependently decreased IFN-γ-induced STAT1 tyrosine phosphorylation. Electrophoretic mobility shift assay of nuclear protein extracts demonstrated that H. pylori infection reduced IFN-γ-induced STAT1 DNA binding. STAT1 was unable to translocate from the cytoplasm to the nucleus in H. pylori-infected HEp-2 cells examined by immunofluorescence, and reverse transcription-PCR showed that IFN-γ-induced interferon regulatory factor 1 expression was inhibited. These effects were independent of the cagA, cagE, and VacA status of the infecting H. pylori strain. Furthermore, neither H. pylori culture supernatants nor conditioned medium from H. pylori-infected MKN45 cells inhibited IFN-γ-induced STAT1 tyrosine phosphorylation, suggesting that inhibition is independent of a soluble epithelial or bacterial factor but is dependent on bacterial contact with epithelial cells. H. pylori disruption of IFN-γ-STAT1 signaling in epithelial cells may represent a mechanism by which the bacterium modifies mucosal immune responses to promote its survival in the human host.

scholarly journals Differential Virulence of Clinical and Bovine-Biased Enterohemorrhagic Escherichia coli O157:H7 Genotypes in Piglet and Dutch Belted Rabbit Models

2011 ◽  
Vol 80 (1) ◽  
pp. 369-380 ◽  
Author(s):  
Smriti Shringi ◽  
Alexis García ◽  
Kevin K. Lahmers ◽  
Kathleen A. Potter ◽  
Sureshkumar Muthupalani ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Severe Disease ◽  
Meat Products ◽  
Developed Countries ◽  
Reservoir Host ◽  
Enterohemorrhagic Escherichia Coli ◽  
Content Type ◽  
Shiga Toxins ◽  
Virulence Potential ◽  
The Developed Countries

ABSTRACTEnterohemorrhagicEscherichia coliO157:H7 (EHEC O157) is an important cause of food and waterborne illness in the developed countries. Cattle are a reservoir host of EHEC O157 and a major source of human exposure through contaminated meat products. Shiga toxins (Stxs) are an important pathogenicity trait of EHEC O157. The insertion sites of the Stx-encoding bacteriophages differentiate EHEC O157 isolates into genogroups commonly isolated from cattle but rarely from sick humans (bovine-biased genotypes [BBG]) and those commonly isolated from both cattle and human patients (clinical genotypes [CG]). Since BBG and CG share the cardinal virulence factors of EHEC O157 and are carried by cattle at similar prevalences, the infrequent occurrence of BBG among human disease isolates suggests that they may be less virulent than CG. We compared the virulence potentials of human and bovine isolates of CG and BBG in newborn conventional pig and weaned Dutch Belted rabbit models. CG-challenged piglets experienced severe disease accompanied by early and high mortality compared to BBG-challenged piglets. Similarly, CG-challenged rabbits were likely to develop lesions in kidney and intestine compared with the BBG-challenged rabbits. The CG strains used in this study carriedstx2and produced significantly higher amounts of Stx, whereas the BBG strains carried thestx2cgene variant only. These results suggest that BBG are less virulent than CG and that this difference in virulence potential is associated with the Stx2 subtype(s) carried and/or the amount of Stx produced.

scholarly journals Inhibition of Indoleamine 2,3-Dioxygenase Activity by Levo-1-Methyl Tryptophan Blocks Gamma Interferon-Induced Chlamydia trachomatis Persistence in Human Epithelial Cells

2011 ◽  
Vol 79 (11) ◽  
pp. 4425-4437 ◽  
Author(s):  
Joyce A. Ibana ◽  
Robert J. Belland ◽  
Arnold H. Zea ◽  
Danny J. Schust ◽  
Takeshi Nagamatsu ◽  
...  
Keyword(s):  
Chlamydia Trachomatis ◽  
Epithelial Cells ◽  
Gamma Interferon ◽  
Developmental Cycle ◽  
Tryptophan Depletion ◽  
Content Type ◽  
Indoleamine 2,3 Dioxygenase ◽  
Human Epithelial Cells ◽  
Ifn Γ

ABSTRACTGamma interferon (IFN-γ) induces expression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO1) in human epithelial cells, the permissive cells for the obligate intracellular bacteriumChlamydia trachomatis. IDO1 depletes tryptophan by catabolizing it to kynurenine with consequences forC. trachomatis, which is a tryptophan auxotroph.In vitrostudies reveal that tryptophan depletion can result in the formation of persistent (viable but noncultivable) chlamydial forms. Here, we tested the effects of the IDO1 inhibitor, levo-1-methyl-tryptophan (L-1MT), on IFN-γ-inducedC. trachomatispersistence. We found that addition of 0.2 mM L-1MT to IFN-γ-exposed infected HeLa cell cultures restricted IDO1 activity at the mid-stage (20 h postinfection [hpi]) of the chlamydial developmental cycle. This delayed tryptophan depletion until the late stage (38 hpi) of the cycle. Parallel morphological and gene expression studies indicated a consequence of the delay was a block in the induction ofC. trachomatispersistence by IFN-γ. Furthermore, L-1MT addition allowedC. trachomatisto undergo secondary differentiation, albeit with limited productive multiplication of the bacterium. IFN-γ-induced persistent infections in epithelial cells have been previously reported to be more resistant to doxycycline than normal productive infectionsin vitro. Pertinent to this observation, we found that L-1MT significantly improved the efficacy of doxycycline in clearing persistentC. trachomatisforms. It has been postulated that persistent forms ofC. trachomatismay contribute to chronic chlamydial disease. Our findings suggest that IDO1 inhibitors such as L-1MT might provide a novel means to investigate, and potentially target, persistent chlamydial forms, particularly in conjunction with conventional therapeutics.

scholarly journals Interaction of Enteropathogenic or Enterohemorrhagic Escherichia coli with HeLa Cells Results in Translocation of Cortactin to the Bacterial Adherence Site

2000 ◽  
Vol 68 (1) ◽  
pp. 382-386 ◽  
Author(s):  
Vlademir V. Cantarelli ◽  
Akira Takahashi ◽  
Yukihiro Akeda ◽  
Kenichi Nagayama ◽  
Takeshi Honda
Keyword(s):  
Escherichia Coli ◽  
Epithelial Cells ◽  
Hela Cell ◽  
Tyrosine Phosphorylation ◽  
Hela Cells ◽  
Shigella Flexneri ◽  
Enterohemorrhagic Escherichia Coli ◽  
Bacterial Adherence ◽  
Cell Infection ◽  
E Coli

ABSTRACT Infection of cultured HeLa epithelial cells with enteropathogenicEscherichia coli (EPEC) or enterohemorrhagic E. coli (EHEC) O157:H7 results in accumulation of cortactin under the adherent bacteria. Tyrosine phosphorylation of cortactin is not induced following HeLa cell infection with EHEC or EPEC, contrary to what has been reported to occur with Shigella flexneri.

scholarly journals Retrograde Trafficking Inhibitor of Shiga Toxins Reduces Morbidity and Mortality of Mice Infected with Enterohemorrhagic Escherichia coli

2015 ◽  
Vol 59 (8) ◽  
pp. 5010-5013 ◽  
Author(s):  
T. Secher ◽  
A. Shima ◽  
K. Hinsinger ◽  
J. C. Cintrat ◽  
L. Johannes ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Survival Rates ◽  
Body Weight Loss ◽  
Enterohemorrhagic Escherichia Coli ◽  
Content Type ◽  
Shiga Toxins ◽  
Retrograde Trafficking ◽  
Reduced Body ◽  
Novel Approach ◽  
Trafficking Inhibitor

ABSTRACTThe most deadly outbreak ofEscherichia coliO104:H4 occurred in Europe in 2011. Here, we evaluated the effects of the retrograde trafficking inhibitor Retro-2cyclin a murine model ofE. coliO104:H4 infection. Systemic treatment with Retro-2cyclsignificantly reduced body weight loss and improved clinical scores and survival rates for O104:H4-infected mice. The present data established that Retro-2cyclcontributes to the protection of mice against O104:H4 infection and may represent a novel approach to limit Shiga toxin-producingEscherichia coli(STEC)-induced toxicity.

scholarly journals Characterization of theIn VitroChlamydia pecorumResponse to Gamma Interferon

2018 ◽  
Vol 86 (4) ◽  
Author(s):  
M. Mominul Islam ◽  
Martina Jelocnik ◽  
Wilhelmina M. Huston ◽  
Peter Timms ◽  
Adam Polkinghorne
Keyword(s):  
Immune Response ◽  
Epithelial Cells ◽  
Host Cell ◽  
Anthranilic Acid ◽  
Gamma Interferon ◽  
Tryptophan Depletion ◽  
Content Type ◽  
Natural Hosts ◽  
Ifn Γ

ABSTRACTChlamydia pecorumis an important intracellular bacterium that causes a range of diseases in animals, including a native Australian marsupial, the koala. In humans and animals, a gamma interferon (IFN-γ)-mediated immune response is important for the control of intracellular bacteria. The present study tested the hypotheses thatC. pecorumcan escape IFN-γ-mediated depletion of host cell tryptophan pools. In doing so, we demonstrated that, unlikeChlamydia trachomatis,C. pecorumis completely resistant to IFN-γ in human epithelial cells. While the growth ofC. pecorumwas inhibited in tryptophan-deficient medium, it could be restored by the addition of kynurenine, anthranilic acid, and indole, metabolites that could be exploited by the gene products of theC. pecorumtryptophan biosynthesis operon. We also found that expression oftrpgenes was detectable only whenC. pecorumwas grown in tryptophan-free medium, with gene repression occurring in response to the addition of kynurenine, anthranilic acid, and indole. When grown in bovine kidney epithelial cells, bovine IFN-γ also failed to restrict the growth ofC. pecorum, whileC. trachomatiswas inhibited, suggesting thatC. pecorumcould use the same mechanisms to evade the immune responsein vivoin its natural host. Highlighting the different mechanisms triggered by IFN-γ, however, both species failed to grow in murine McCoy cells treated with murine IFN-γ. This work confirms previous hypotheses about the potential survival ofC. pecorumafter IFN-γ-mediated host cell tryptophan depletion and raises questions about the immune pathways used by the natural hosts ofC. pecorumto control the widespread pathogen.

scholarly journals CCL19 enhances CD8+ T-cell responses and accelerates HBV clearance

2021 ◽  
Author(s):  
Yan Yan ◽  
Wei Zhao ◽  
Wei Liu ◽  
Yan Li ◽  
Xu Wang ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Crucial Role ◽  
Cell Activation ◽  
Hbv Infection ◽  
Host Immune System ◽  
Tnf Α ◽  
Ifn Γ ◽  
High Level

Abstract Background Chemokine (C–C motif) ligand 19 (CCL19) is a leukocyte chemoattractant that plays a crucial role in cell trafficking and leukocyte activation. Dysfunctional CD8+ T cells play a crucial role in persistent HBV infection. However, whether HBV can be cleared by CCL19-activated immunity remains unclear. Methods We assessed the effects of CCL19 on the activation of PBMCs in patients with HBV infection. We also examined how CCL19 influences HBV clearance and modulates HBV-responsive T cells in a mouse model of chronic hepatitis B (CHB). In addition, C–C chemokine-receptor type 7 (CCR7) knockdown mice were used to elucidate the underlying mechanism of CCL19/CCR7 axis-induced immune activation. Results From in vitro experiments, we found that CCL19 enhanced the frequencies of Ag-responsive IFN-γ+ CD8+ T cells from patients by approximately twofold, while CCR7 knockdown (LV-shCCR7) and LY294002 partially suppressed IFN-γ secretion. In mice, CCL19 overexpression led to rapid clearance of intrahepatic HBV likely through increased intrahepatic CD8+ T-cell proportion, decreased frequency of PD-1+ CD8+ T cells in blood and compromised suppression of hepatic APCs, with lymphocytes producing a significantly high level of Ag-responsive TNF-α and IFN-γ from CD8+ T cells. In both CCL19 over expressing and CCR7 knockdown (AAV-shCCR7) CHB mice, the frequency of CD8+ T-cell activation-induced cell death (AICD) increased, and a high level of Ag-responsive TNF-α and low levels of CD8+ regulatory T (Treg) cells were observed. Conclusions Findings in this study provide insights into how CCL19/CCR7 axis modulates the host immune system, which may promote the development of immunotherapeutic strategies for HBV treatment by overcoming T-cell tolerance.

scholarly journals Presence of Enterohemorrhagic Escherichia coli ST678/O104:H4 in France Prior to 2011

2011 ◽  
Vol 77 (24) ◽  
pp. 8784-8786 ◽  
Author(s):  
Stefan Monecke ◽  
Patricia Mariani-Kurkdjian ◽  
Edouard Bingen ◽  
François-Xavier Weill ◽  
Charlotte Balière ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Enterohemorrhagic Escherichia Coli ◽  
Content Type

ABSTRACTTwo isolates of enterohemorrhagicEscherichia coli(EHEC) O104:H4 were isolated in France in 2004 and 2009. Both were characterized and compared to the strain which caused the German outbreak in 2011 and to other O104:H4 strains. This suggests that different O104:H4 EHEC strains were present several years prior to the 2011 outbreak.

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