scholarly journals Burkholderia cenocepacia Lipopolysaccharide Modification and Flagellin Glycosylation Affect Virulence but Not Innate Immune Recognition in Plants

mBio ◽  
2015 ◽  
Vol 6 (3) ◽  
Author(s):  
Maryam Khodai-Kalaki ◽  
Angel Andrade ◽  
Yasmine Fathy Mohamed ◽  
Miguel A. Valvano
Keyword(s):  
Nitric Oxide ◽  
Arabidopsis Thaliana ◽  
Galleria Mellonella ◽  
Opportunistic Infections ◽  
Innate Immune ◽  
Burkholderia Cenocepacia ◽  
Immune Recognition ◽  
Content Type ◽  
Opportunistic Bacteria ◽  
Flagellin Glycosylation

ABSTRACTBurkholderia cenocepaciacauses opportunistic infections in plants, insects, animals, and humans, suggesting that “virulence” depends on the host and its innate susceptibility to infection. We hypothesized that modifications in key bacterial molecules recognized by the innate immune system modulate host responses toB. cenocepacia. Indeed, modification of lipopolysaccharide (LPS) with 4-amino-4-deoxy-l-arabinose and flagellin glycosylation attenuatesB. cenocepaciainfection inArabidopsis thalianaandGalleria mellonellainsect larvae. However,B. cenocepaciaLPS and flagellin triggered rapid bursts of nitric oxide and reactive oxygen species inA. thalianaleading to activation of thePR-1defense gene. These responses were drastically reduced in plants withfls2(flagellin FLS2 host receptor kinase),Atnoa1(nitric oxide-associated protein 1), anddnd1-1(reduced production of nitric oxide) null mutations. Together, our results indicate that LPS modification and flagellin glycosylation do not affect recognition by plant receptors but are required for bacteria to establish overt infection.IMPORTANCEVirulence and pathogenicity are properties ascribed to microbes, which actually require careful consideration of the host. Using the term “pathogen” to define a microbe without considering its host has recently been debated, since the microbe's capacity to establish a niche in a given host is a critical feature associated with infection. Opportunistic bacteria are a perfect example of microbes whose ability to cause disease is intimately related to the host's ability to recognize and respond to the infection. Here, we use the opportunistic bacteriumBurkholderia cenocepaciaand the host plantArabidopsis thalianato investigate the role of bacterial surface molecules, namely, lipopolysaccharide and flagellin, in contributing to infection and also in eliciting a host response. We reveal that both molecules can be modified by glycosylation, and although the modifications are critical for the bacteria to establish an infection, they do not impact the host's ability to recognize the pathogen.

scholarly journals Distinct Contributions of Interleukin-1α (IL-1α) and IL-1β to Innate Immune Recognition of Pseudomonas aeruginosa in the Lung

2014 ◽  
Vol 82 (10) ◽  
pp. 4204-4211 ◽  
Author(s):  
Khatoun Al Moussawi ◽  
Barbara I. Kazmierczak
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Immune Responses ◽  
Bacterial Pathogen ◽  
Innate Immune ◽  
Immune Recognition ◽  
Content Type ◽  
Caspase 1 ◽  
Rapid Responses ◽  
Subsequent Activation ◽  
Deficient Mice

ABSTRACTThe bacterial pathogenPseudomonas aeruginosacauses acute infections associated with significant morbidity and mortality.P. aeruginosaelicits strong innate immune responses in immunocompetent hosts, and the resulting recruitment of neutrophils to the site of infection is necessary for bacterial clearance.P. aeruginosalipopolysaccharide and flagellin are recognized by extracellular Toll-like receptors, but the most rapid responses to infection occur when cytosolic receptors sense flagellin or type 3 secretion system (T3SS) structural proteins. The subsequent activation of the NLRC4 inflammasome and caspase-1 generates an interleukin-1β (IL-1β) signal that is required for the rapid neutrophilic response. A T3SS effector, exotoxin U (ExoU), can inhibit activation of the NLRC4 inflammasome and caspase-1. Thus, our observation that IL-1 receptor (IL-1R)-mediated signals were still required to initiate a response to ExoU-producing bacteria was unexpected. As both IL-1α and IL-1β signal via the IL-1R, we examined immune responses in mice lacking either of these cytokines. IL-1β-deficient mice responded to ExoU-producingP. aeruginosabacteria similarly to wild-type animals; however, IL-1α-deficient mice had an attenuated immune response. The situation was reversed following infections by ExoU-negative bacteria: here, IL-1α was dispensable for neutrophil recruitment, while IL-1β was required. IL-1α secretion by macrophages infected with ExoU-producingP. aeruginosaisolates was independent of both caspase-1 and caspase-11. This study documents distinct roles for IL-1α and IL-1β in the response toP. aeruginosainfection as a function of the T3SS effectors produced by the infecting strain. The redundancy of these two cytokines nonetheless allows the infected host to mount a response to ExoU-positive and -negative bacterial isolates.

scholarly journals Phenylacetyl Coenzyme A, Not Phenylacetic Acid, Attenuates CepIR-Regulated Virulence in Burkholderia cenocepacia

2019 ◽  
Vol 85 (24) ◽  
Author(s):  
Tasia Joy Lightly ◽  
Kara L. Frejuk ◽  
Marie-Christine Groleau ◽  
Laurent R. Chiarelli ◽  
Cor Ras ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Phenylacetic Acid ◽  
Coenzyme A ◽  
Opportunistic Pathogen ◽  
Burkholderia Cenocepacia ◽  
Signal Molecules ◽  
Wild Type ◽  
Content Type ◽  
Opportunistic Bacteria ◽  
Virulent Phenotype

ABSTRACT During phenylalanine catabolism, phenylacetic acid (PAA) is converted to phenylacetyl coenzyme A (PAA-CoA) by a ligase, PaaK, and then PAA-CoA is epoxidized by a multicomponent monooxygenase, PaaABCDE, before further degradation through the tricarboxylic acid (TCA) cycle. In the opportunistic pathogen Burkholderia cenocepacia, loss of paaABCDE attenuates virulence factor expression, which is under the control of the LuxIR-like quorum sensing (QS) system, CepIR. To further investigate the link between CepIR-regulated virulence and PAA catabolism, we created knockout mutants of the first step of the pathway (PAA-CoA synthesis by PaaK) and characterized them in comparison to a paaABCDE mutant using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and virulence assays. We found that while loss of PaaABCDE decreased virulence, deletion of the paaK genes resulted in a more virulent phenotype than that of the wild-type strain. Deletion of either paaK or paaABCDE led to higher levels of released PAA but no differences in levels of internal accumulation compared to the wild-type level. While we found no evidence of direct cepIR downregulation by PAA-CoA or PAA, a low-virulence cepR mutant reverted to a virulent phenotype upon removal of the paaK genes. On the other hand, removal of paaABCDE in the cepR mutant did not impact its attenuated phenotype. Together, our results suggest an indirect role for PAA-CoA in suppressing B. cenocepacia CepIR-activated virulence. IMPORTANCE The opportunistic pathogen Burkholderia cenocepacia uses a chemical signal process called quorum sensing (QS) to produce virulence factors. In B. cenocepacia, QS relies on the presence of the transcriptional regulator CepR which, upon binding QS signal molecules, activates virulence. In this work, we found that even in the absence of CepR, B. cenocepacia can elicit a pathogenic response if phenylacetyl-CoA, an intermediate of the phenylacetic acid degradation pathway, is not produced. Instead, accumulation of phenylacetyl-CoA appears to attenuate pathogenicity. Therefore, we have discovered that it is possible to trigger virulence in the absence of CepR, challenging the classical view of activation of virulence by this QS mechanism. Our work provides new insight into the relationship between metabolism and virulence in opportunistic bacteria. We propose that in the event that QS signaling molecules cannot accumulate to trigger a pathogenic response, a metabolic signal can still activate virulence in B. cenocepacia.

scholarly journals Remasking of Candida albicans β-Glucan in Response to Environmental pH Is Regulated by Quorum Sensing

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Fabien Cottier ◽  
Sarah Sherrington ◽  
Sarah Cockerill ◽  
Valentina del Olmo Toledo ◽  
Stephen Kissane ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Quorum Sensing ◽  
Immune Responses ◽  
Female Reproductive Tract ◽  
Innate Immune ◽  
Immune Recognition ◽  
Innate Immune Responses ◽  
Content Type ◽  
Cell Wall Remodeling

ABSTRACT Candida albicans is a commensal yeast of the human gut which is tolerated by the immune system but has the potential to become an opportunistic pathogen. One way in which C. albicans achieves this duality is through concealing or exposing cell wall pathogen-associated molecular patterns (PAMPs) in response to host-derived environment cues (pH, hypoxia, and lactate). This cell wall remodeling allows C. albicans to evade or hyperactivate the host’s innate immune responses, leading to disease. Previously, we showed that adaptation of C. albicans to acidic environments, conditions encountered during colonization of the female reproductive tract, induces significant cell wall remodeling resulting in the exposure of two key fungal PAMPs (β-glucan and chitin). Here, we report that this pH-dependent cell wall remodeling is time dependent, with the initial change in pH driving cell wall unmasking, which is then remasked at later time points. Remasking of β-glucan was mediated via the cell density-dependent fungal quorum sensing molecule farnesol, while chitin remasking was mediated via a small, heat-stable, nonproteinaceous secreted molecule(s). Transcript profiling identified a core set of 42 genes significantly regulated by pH over time and identified the transcription factor Efg1 as a regulator of chitin exposure through regulation of CHT2. This dynamic cell wall remodeling influenced innate immune recognition of C. albicans, suggesting that during infection, C. albicans can manipulate the host innate immune responses. IMPORTANCE Candida albicans is part of the microbiota of the skin and gastrointestinal and reproductive tracts of humans and has coevolved with us for millennia. During that period, C. albicans has developed strategies to modulate the host’s innate immune responses, by regulating the exposure of key epitopes on the fungal cell surface. Here, we report that exposing C. albicans to an acidic environment, similar to the one of the stomach or vagina, increases the detection of the yeast by macrophages. However, this effect is transitory, as C. albicans is able to remask these epitopes (glucan and chitin). We found that glucan remasking is controlled by the production of farnesol, a molecule secreted by C. albicans in response to high cell densities. However, chitin-remasking mechanisms remain to be identified. By understanding the relationship between environmental sensing and modulation of the host-pathogen interaction, new opportunities for the development of innovative antifungal strategies are possible.

scholarly journals Immune recognition of Pseudomonas aeruginosa mediated by the IPAF/NLRC4 inflammasome

2007 ◽  
Vol 204 (13) ◽  
pp. 3235-3245 ◽  
Author(s):  
Fayyaz S. Sutterwala ◽  
Lilia A. Mijares ◽  
Li Li ◽  
Yasunori Ogura ◽  
Barbara I. Kazmierczak ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cell Death ◽  
Host Cell ◽  
Proinflammatory Cytokine ◽  
Opportunistic Infections ◽  
Inflammatory Responses ◽  
Innate Immune ◽  
Immune Recognition ◽  
Independent Manner ◽  
Caspase 1

Pseudomonas aeruginosa is a Gram-negative bacterium that causes opportunistic infections in immunocompromised individuals. P. aeruginosa employs a type III secretion system to inject effector molecules into the cytoplasm of the host cell. This interaction with the host cell leads to inflammatory responses that eventually result in cell death. We show that infection of macrophages with P. aeruginosa results in activation of caspase-1 in an IPAF-dependent, but flagellin-independent, manner. Macrophages deficient in IPAF or caspase-1 were markedly resistant to P. aeruginosa–induced cell death and release of the proinflammatory cytokine interleukin (IL)-1β. A subset of P. aeruginosa isolates express the effector molecule exoenzyme U (ExoU), which we demonstrate is capable of inhibiting caspase-1–driven proinflammatory cytokine production. This study shows a key role for IPAF and capase-1 in innate immune responses to the pathogen P. aeruginosa, and also demonstrates that virulent ExoU-expressing strains of P. aeruginosa can circumvent this innate immune response.

scholarly journals Burkholderia cepacia Complex Phage-Antibiotic Synergy (PAS): Antibiotics Stimulate Lytic Phage Activity

2014 ◽  
Vol 81 (3) ◽  
pp. 1132-1138 ◽  
Author(s):  
Fatima Kamal ◽  
Jonathan J. Dennis
Keyword(s):  
Burkholderia Cepacia ◽  
Galleria Mellonella ◽  
Burkholderia Cenocepacia ◽  
Burkholderia Cepacia Complex ◽  
Lytic Phage ◽  
Bacterial Killing ◽  
Content Type ◽  
Drug Classes ◽  
Phage Production ◽  
A Chain

ABSTRACTTheBurkholderia cepaciacomplex (Bcc) is a group of at least 18 species of Gram-negative opportunistic pathogens that can cause chronic lung infection in cystic fibrosis (CF) patients. Bcc organisms possess high levels of innate antimicrobial resistance, and alternative therapeutic strategies are urgently needed. One proposed alternative treatment is phage therapy, the therapeutic application of bacterial viruses (or bacteriophages). Recently, some phages have been observed to form larger plaques in the presence of sublethal concentrations of certain antibiotics; this effect has been termed phage-antibiotic synergy (PAS). Those reports suggest that some antibiotics stimulate increased production of phages under certain conditions. The aim of this study is to examine PAS in phages that infectBurkholderia cenocepaciastrains C6433 and K56-2. Bcc phages KS12 and KS14 were tested for PAS, using 6 antibiotics representing 4 different drug classes. Of the antibiotics tested, the most pronounced effects were observed for meropenem, ciprofloxacin, and tetracycline. When grown with subinhibitory concentrations of these three antibiotics, cells developed a chain-like arrangement, an elongated morphology, and a clustered arrangement, respectively. When treated with progressively higher antibiotic concentrations, both the sizes of plaques and phage titers increased, up to a maximum.B. cenocepaciaK56-2-infectedGalleria mellonellalarvae treated with phage KS12 and low-dose meropenem demonstrated increased survival over controls treated with KS12 or antibiotic alone. These results suggest that antibiotics can be combined with phages to stimulate increased phage production and/or activity and thus improve the efficacy of bacterial killing.

scholarly journals Correction: Type I IFNs facilitate innate immune control of the opportunistic bacteria Burkholderia cenocepacia in the macrophage cytosol

2021 ◽  
Vol 17 (8) ◽  
pp. e1009821
Author(s):  
Michael G. Dorrington ◽  
Clinton J. Bradfield ◽  
Justin B. Lack ◽  
Bin Lin ◽  
Sinu P. John ◽  
...  
Keyword(s):  
Innate Immune ◽  
Burkholderia Cenocepacia ◽  
Type I ◽  
Immune Control ◽  
Type I Ifns ◽  
Opportunistic Bacteria

scholarly journals Bordetella pertussis Naturally Occurring Isolates with Altered Lipooligosaccharide Structure Fail To Fully Mature Human Dendritic Cells

2014 ◽  
Vol 83 (1) ◽  
pp. 227-238 ◽  
Author(s):  
Jolanda Brummelman ◽  
Rosanne E. Veerman ◽  
Hendrik Jan Hamstra ◽  
Anna J. M. Deuss ◽  
Tim J. Schuijt ◽  
...  
Keyword(s):  
Immune Response ◽  
Dendritic Cells ◽  
Bordetella Pertussis ◽  
Lipid A ◽  
Whooping Cough ◽  
Human Monocyte ◽  
Innate Immune ◽  
Clinical Isolates ◽  
Immune Recognition ◽  
Content Type

Bordetella pertussisis a Gram-negative bacterium and the causative agent of whooping cough. Despite high vaccination coverage, outbreaks are being increasingly reported worldwide. Possible explanations include adaptation of this pathogen, which may interfere with recognition by the innate immune system. Here, we describe innate immune recognition and responses to differentB. pertussisclinical isolates. By using HEK-Blue cells transfected with different pattern recognition receptors, we found that 3 out of 19 clinical isolates failed to activate Toll-like receptor 4 (TLR4). These findings were confirmed by using the monocytic MM6 cell line. Although incubation with high concentrations of these 3 strains resulted in significant activation of the MM6 cells, it was found to occur mainly through interaction with TLR2 and not through TLR4. When using live bacteria, these 3 strains also failed to activate TLR4 on HEK-Blue cells, and activation of MM6 cells or human monocyte-derived dendritic cells was significantly lower than activation induced by the other 16 strains. Mass spectrum analysis of the lipid A moieties from these 3 strains indicated an altered structure of this molecule. Gene sequence analysis revealed mutations in genes involved in lipid A synthesis. Findings from this study indicate thatB. pertussisisolates that do not activate TLR4 occur naturally and that this phenotype may give this bacterium an advantage in tempering the innate immune response and establishing infection. Knowledge on the strategies used by this pathogen in evading the host immune response is essential for the improvement of current vaccines or for the development of new ones.

scholarly journals Identification of Burkholderia cenocepacia Strain H111 Virulence Factors Using Nonmammalian Infection Hosts

2012 ◽  
Vol 81 (1) ◽  
pp. 143-153 ◽  
Author(s):  
Stephan Schwager ◽  
Kirsty Agnoli ◽  
Manuela Köthe ◽  
Friederike Feldmann ◽  
Michael Givskov ◽  
...  
Keyword(s):  
Virulence Factors ◽  
Galleria Mellonella ◽  
Burkholderia Cenocepacia ◽  
Infection Model ◽  
Extracellular Proteases ◽  
Content Type ◽  
C Elegans ◽  
Content Model ◽  
Genes Encoding ◽  
Insertion Mutants

Burkholderia cenocepaciaH111, a strain isolated from a cystic fibrosis patient, has been shown to effectively kill the nematodeCaenorhabditis elegans. We used theC. elegansmodel of infection to screen a mini-Tn5mutant library ofB. cenocepaciaH111 for attenuated virulence. Of the approximately 5,500B. cenocepaciaH111 random mini-Tn5insertion mutants that were screened, 22 showed attenuated virulence inC. elegans. Except for the quorum-sensing regulatorcepR, none of the mutated genes coded for the biosynthesis of classical virulence factors such as extracellular proteases or siderophores. Instead, the mutants contained insertions in metabolic and regulatory genes. Mutants attenuated in virulence in theC. elegansinfection model were also tested in theDrosophila melanogasterpricking model, and those also attenuated in this model were further tested inGalleria mellonella. Six of the 22 mutants were attenuated inD. melanogaster, and five of these were less pathogenic in theG. mellonellamodel. We show that genes encoding enzymes of the purine, pyrimidine, and shikimate biosynthesis pathways are critical for virulence in multiple host models of infection.

scholarly journals Immune Recognition of the Epidemic Cystic Fibrosis Pathogen Burkholderia dolosa

2017 ◽  
Vol 85 (6) ◽  
Author(s):  
Damien Roux ◽  
Molly Weatherholt ◽  
Bradley Clark ◽  
Mihaela Gadjeva ◽  
Diane Renaud ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Immune Response ◽  
Cytokine Production ◽  
Cultured Cells ◽  
Host Immune Response ◽  
Host Cells ◽  
Burkholderia Cenocepacia ◽  
Immune Recognition ◽  
Content Type

ABSTRACT Burkholderia dolosa caused an outbreak in the cystic fibrosis (CF) clinic at Boston Children's Hospital from 1998 to 2005 and led to the infection of over 40 patients, many of whom died due to complications from infection by this organism. To assess whether B. dolosa significantly contributes to disease or is recognized by the host immune response, mice were infected with a sequenced outbreak B. dolosa strain, AU0158, and responses were compared to those to the well-studied CF pathogen Pseudomonas aeruginosa. In parallel, mice were also infected with a polar flagellin mutant of B. dolosa to examine the role of flagella in B. dolosa lung colonization. The results showed a higher persistence in the host by B. dolosa strains, and yet, neutrophil recruitment and cytokine production were lower than those with P. aeruginosa. The ability of host immune cells to recognize B. dolosa was then assessed, B. dolosa induced a robust cytokine response in cultured cells, and this effect was dependent on the flagella only when bacteria were dead. Together, these results suggest that B. dolosa can be recognized by host cells in vitro but may avoid or suppress the host immune response in vivo through unknown mechanisms. B. dolosa was then compared to other Burkholderia species and found to induce similar levels of cytokine production despite being internalized by macrophages more than Burkholderia cenocepacia strains. These data suggest that B. dolosa AU0158 may act differently with host cells and is recognized differently by immune systems than are other Burkholderia strains or species.

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