Enterotoxigenic Escherichia coli Prevents Host NF-κB Activation by Targeting IκBα Polyubiquitination

ABSTRACTThe NF-κB pathway regulates innate immune responses to infection. NF-κB is activated after pathogen-associated molecular patterns are detected, leading to the induction of proinflammatory host responses. As a countermeasure, bacterial pathogens have evolved mechanisms to subvert NF-κB signaling. EnterotoxigenicEscherichia coli(ETEC) causes diarrheal disease and significant morbidity and mortality for humans in developing nations. The extent to which this important pathogen subverts innate immune responses by directly targeting the NF-κB pathway is an understudied topic. Here we report that ETEC secretes a heat-stable, proteinaceous factor that blocks NF-κB signaling normally induced by tumor necrosis factor (TNF), interleukin-1β, and flagellin. Pretreating intestinal epithelial cells with ETEC supernatant significantly blocked the degradation of the NF-κB inhibitor IκBα without affecting IκBα phosphorylation. Data from immunoprecipitation experiments suggest that the ETEC factor functions by preventing IκBα polyubiquitination. Inhibiting clathrin function blocked the activity of the secreted ETEC factor, suggesting that this yet-uncharacterized activity may utilize clathrin-dependent endocytosis to enter host cells. These data suggest that ETEC evades the host innate immune response by directly modulating NF-κB signaling.

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Characterization of Immunological Cross-Reactivity between Enterotoxigenic Escherichia coli Heat-Stable Toxin and Human Guanylin and Uroguanylin

Infection and Immunity ◽

10.1128/iai.01749-14 ◽

2014 ◽

Vol 82 (7) ◽

pp. 2913-2922 ◽

Cited By ~ 14

Author(s):

Arne M. Taxt ◽

Yuleima Diaz ◽

Amélie Bacle ◽

Cédric Grauffel ◽

Nathalie Reuter ◽

...

Keyword(s):

Escherichia Coli ◽

Diarrheal Disease ◽

Cross Reactivity ◽

Enterotoxigenic Escherichia Coli ◽

Middle Income ◽

Content Type ◽

Cross Reactions ◽

Endogenous Peptides ◽

Heat Stable ◽

Wide Range

ABSTRACTEnterotoxigenicEscherichia coli(ETEC) expressing the heat-stable toxin (ST) (human-type [STh] and porcine-type [STp] variants) is among the five most important enteric pathogens in young children living in low- and middle-income countries. ST mediates diarrheal disease through activation of the guanylate cyclase C (GC-C) receptor and is an attractive vaccine target with the potential to confer protection against a wide range of ETEC strains. However, immunological cross-reactivity to the endogenous GC-C ligands guanylin and uroguanylin is a major concern because of the similarities to ST in amino acid sequence, structure, and function. We have investigated the presence of similar epitopes on STh, STp, guanylin, and uroguanylin by analyzing these peptides in eight distinct competitive enzyme-linked immunosorbent assays (ELISAs). A fraction (27%) of a polyclonal anti-STh antibody and an anti-STh monoclonal antibody (MAb) cross-reacted with uroguanylin, the latter with a 73-fold-lower affinity. In contrast, none of the antibodies raised against STp, one polyclonal antibody and three MAbs, cross-reacted with the endogenous peptides. Antibodies raised against guanylin and uroguanylin showed partial cross-reactivity with the ST peptides. Our results demonstrate, for the first time, that immunological cross-reactions between ST and the endogenous peptides can occur. However, the partial nature and low affinity of the observed cross-reactions suggest that the risk of adverse effects from a future ST vaccine may be low. Furthermore, our results suggest that this risk may be reduced or eliminated by basing an ST immunogen on STp or a selectively mutated variant of STh.

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Mouse intestinal innate immune responses altered by enterotoxigenic Escherichia coli (ETEC) infection

Microbes and Infection ◽

10.1016/j.micinf.2014.09.005 ◽

2014 ◽

Vol 16 (11) ◽

pp. 954-961 ◽

Cited By ~ 26

Author(s):

Wenkai Ren ◽

Jie Yin ◽

Jielin Duan ◽

Gang Liu ◽

Xiaoping Zhu ◽

...

Keyword(s):

Escherichia Coli ◽

Immune Responses ◽

Innate Immune ◽

Enterotoxigenic Escherichia Coli ◽

Innate Immune Responses ◽

Etec Infection

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Zinc Influences Innate Immune Responses in Children with Enterotoxigenic Escherichia coli-Induced Diarrhea

Journal of Nutrition ◽

10.3945/jn.109.111492 ◽

2010 ◽

Vol 140 (5) ◽

pp. 1049-1056 ◽

Cited By ~ 37

Author(s):

Alaullah Sheikh ◽

Sohel Shamsuzzaman ◽

Shaikh Meshbahuddin Ahmad ◽

Dilruba Nasrin ◽

Setarun Nahar ◽

...

Keyword(s):

Escherichia Coli ◽

Immune Responses ◽

Innate Immune ◽

Enterotoxigenic Escherichia Coli ◽

Innate Immune Responses

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Heat-Labile- and Heat-Stable-Toxoid Fusions (LTR192G-STaP13F) of Human Enterotoxigenic Escherichia coli Elicit Neutralizing Antitoxin Antibodies

Infection and Immunity ◽

10.1128/iai.00165-11 ◽

2011 ◽

Vol 79 (10) ◽

pp. 4002-4009 ◽

Cited By ~ 41

Author(s):

Mei Liu ◽

Xiaosai Ruan ◽

Chengxian Zhang ◽

Steve R. Lawson ◽

David E. Knudsen ◽

...

Keyword(s):

Escherichia Coli ◽

Diarrheal Disease ◽

Full Length ◽

Enterotoxigenic Escherichia Coli ◽

Secretory Iga ◽

Content Type ◽

Human Type ◽

Heat Stable ◽

Heat Labile ◽

Iga Antibodies

ABSTRACTEnterotoxigenicEscherichia coli(ETEC) strains are a major cause of diarrheal disease in humans and animals. Adhesins and enterotoxins, including heat-labile (LT) and heat-stable (STa) toxins, are the key virulence factors. Antigenic adhesin and LT antigens have been used in developing vaccines against ETEC diarrhea. However, STa has not been included because of its poor immunogenicity and potent toxicity. Our recent study showed that porcine-type STa toxoids became immunogenic and elicited neutralizing anti-STa antibodies after being genetically fused to a full-length porcine-type LT toxoid, LTR192G(W. Zhang et al., Infect. Immun. 78:316-325, 2010). In this study, we mutated human-type LT and STa genes, which are highly homologous to porcine-type toxin genes, for a full-length LT toxoid (LTR192G) and a full-length STa toxoid (STaP13F) and genetically fused them to produce LT192-STa13toxoid fusions. Mice immunized with LT192-STa13fusion antigens developed anti-LT and anti-STa IgG (in serum and feces) and IgA antibodies (in feces). Moreover, secretory IgA antibodies from immunized mice were shown to neutralize STa and cholera toxins in T-84 cells. In addition, we fused the STa13toxoid at the N terminus and C terminus, between the A1 and A2 peptides, and between the A and B subunits of LT192to obtain different fusions in order to explore strategies for enhancing STa immunogenicity. This study demonstrated that human-type LT192-STa13fusions induce neutralizing antitoxin antibodies and provided important information for developing toxoid vaccines against human ETEC diarrhea.

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Comparison of Holstein and Jersey Innate Immune Responses to Escherichia coli Intramammary Infection

Journal of Dairy Science ◽

10.3168/jds.2008-1013 ◽

2008 ◽

Vol 91 (6) ◽

pp. 2225-2235 ◽

Cited By ~ 35

Author(s):

D.D. Bannerman ◽

A.C.W. Kauf ◽

M.J. Paape ◽

H.R. Springer ◽

J.P. Goff

Keyword(s):

Escherichia Coli ◽

Immune Responses ◽

Innate Immune ◽

Innate Immune Responses ◽

Intramammary Infection

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Immunologic Pathways in Protective versus Maladaptive Host Responses to Attenuated and Pathogenic Strains ofMycoplasma gallisepticum

Infection and Immunity ◽

10.1128/iai.00613-18 ◽

2018 ◽

Vol 87 (3) ◽

Cited By ~ 2

Author(s):

Jessica Beaudet ◽

Edan R. Tulman ◽

Katherine Pflaum ◽

Jessica A. Canter ◽

Lawrence K. Silbart ◽

...

Keyword(s):

Innate Immune ◽

Host Responses ◽

Immune Gene ◽

Avian Host ◽

Innate Immune Responses ◽

Content Type ◽

Mucosal Tissues ◽

Rapid Clearance ◽

Pathogen Clearance ◽

Host Genes

ABSTRACTMycoplasmas are small bacterial commensals or pathogens that commonly colonize host mucosal tissues and avoid rapid clearance, in part by stimulating inflammatory, immunopathogenic responses. We previously characterized a wide array of transcriptomic perturbations in avian host tracheal mucosae infected with virulent, immunopathologicMycoplasma gallisepticum; however, mechanisms delineating these from protective responses, such as those induced upon vaccination, have not been thoroughly explored. In this study, host transcriptomic responses to two experimentalM. gallisepticumvaccines were assessed during the first 2 days of infection. Relative to virulent infection, host metabolic and immune gene responses to both vaccines were greatly decreased, including early innate immune responses critical to disease development and subsequent adaptive immunity. These data specify host genes and potential mechanisms contributing to maladaptive versus beneficial host responses—information critical for design of vaccines efficacious in both limiting inflammation and enabling pathogen clearance.

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Cooperative Immune Suppression by Escherichia coli and Shigella Effector Proteins

Infection and Immunity ◽

10.1128/iai.00560-17 ◽

2018 ◽

Vol 86 (4) ◽

Cited By ~ 6

Author(s):

Maarten F. de Jong ◽

Neal M. Alto

Keyword(s):

Escherichia Coli ◽

Defense Mechanisms ◽

Immune Defense ◽

Effector Proteins ◽

Innate Immune ◽

Host Cells ◽

Secretion Systems ◽

Content Type ◽

E Coli ◽

Type Iii Secretion Systems

ABSTRACT The enteric attaching and effacing (A/E) pathogens enterohemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC) and the invasive pathogens enteroinvasive E. coli (EIEC) and Shigella encode type III secretion systems (T3SS) used to inject effector proteins into human host cells during infection. Among these are a group of effectors required for NF-κB-mediated host immune evasion. Recent studies have identified several effector proteins from A/E pathogens and EIEC/ Shigella that are involved in suppression of NF-κB and have uncovered their cellular and molecular functions. A novel mechanism among these effectors from both groups of pathogens is to coordinate effector function during infection. This cooperativity among effector proteins explains how bacterial pathogens are able to effectively suppress innate immune defense mechanisms in response to diverse classes of immune receptor signaling complexes (RSCs) stimulated during infection.

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Mycobacterium tuberculosisinhibits human innate immune responses via the production of TLR2 antagonist glycolipids

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1707840114 ◽

2017 ◽

Vol 114 (42) ◽

pp. 11205-11210 ◽

Cited By ~ 33

Author(s):

Landry Blanc ◽

Martine Gilleron ◽

Jacques Prandi ◽

Ok-ryul Song ◽

Mi-Seon Jang ◽

...

Keyword(s):

Immune Responses ◽

Molecular Mechanisms ◽

Cytokine Production ◽

Cell Envelope ◽

Costimulatory Molecule ◽

Immune Defense ◽

Innate Immune ◽

Host Cells ◽

Innate Immune Responses ◽

Reporter System

Mycobacterium tuberculosisis a major human pathogen that is able to survive inside host cells and resist immune clearance. Most particularly, it inhibits several arms of the innate immune response, including phagosome maturation or cytokine production. To better understand the molecular mechanisms by whichM. tuberculosiscircumvents host immune defenses, we used a transposon mutant library generated in a virulent clinical isolate ofM. tuberculosisof the W/Beijing family to infect human macrophages, utilizing a cell line derivative of THP-1 cells expressing a reporter system for activation of the transcription factor NF-κB, a key regulator of innate immunity. We identified severalM. tuberculosismutants inducing a NF-κB activation stronger than that of the wild-type strain. One of these mutants was found to be deficient for the synthesis of cell envelope glycolipids, namely sulfoglycolipids, suggesting that the latter can interfere with innate immune responses. Using natural and synthetic molecular variants, we determined that sulfoglycolipids inhibit NF-κB activation and subsequent cytokine production or costimulatory molecule expression by acting as competitive antagonists of Toll-like receptor 2, thereby inhibiting the recognition ofM. tuberculosisby this receptor. Our study reveals that producing glycolipid antagonists of pattern recognition receptors is a strategy used byM. tuberculosisto undermine innate immune defense. Sulfoglycolipids are major and specific lipids ofM. tuberculosis, considered for decades as virulence factors of the bacilli. Our study uncovers a mechanism by which they may contribute toM. tuberculosisvirulence.

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Cooperative Role of Antibodies against Heat-Labile Toxin and the EtpA Adhesin in Preventing Toxin Delivery and Intestinal Colonization by Enterotoxigenic Escherichia coli

Clinical and Vaccine Immunology ◽

10.1128/cvi.00351-12 ◽

2012 ◽

Vol 19 (10) ◽

pp. 1603-1608 ◽

Cited By ~ 20

Author(s):

Koushik Roy ◽

David J. Hamilton ◽

James M. Fleckenstein

Keyword(s):

Escherichia Coli ◽

Diarrheal Disease ◽

Vaccine Development ◽

Enterotoxigenic Escherichia Coli ◽

Intestinal Colonization ◽

Content Type ◽

Heat Labile

ABSTRACTEnterotoxigenicEscherichia coli(ETEC) is an important cause of diarrheal disease in developing countries, where it is responsible for hundreds of thousands of deaths each year. Vaccine development for ETEC has been hindered by the heterogeneity of known molecular targets and the lack of broad-based sustained protection afforded by existing vaccine strategies. In an effort to explore the potential role of novel antigens in ETEC vaccines, we examined the ability of antibodies directed against the ETEC heat-labile toxin (LT) and the recently described EtpA adhesin to prevent intestinal colonizationin vivoand toxin delivery to epithelial cellsin vitro. We demonstrate that EtpA is required for the optimal delivery of LT and that antibodies against this adhesin play at least an additive role in preventing delivery of LT to target intestinal cells when combined with antibodies against either the A or B subunits of the toxin. Moreover, vaccination with a combination of LT and EtpA significantly impaired intestinal colonization. Together, these results suggest that the incorporation of recently identified molecules such as EtpA could be used to enhance current approaches to ETEC vaccine development.

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