scholarly journals Hexa-Acylated Lipid A Is Required for Host Inflammatory Response to Neisseria gonorrhoeae in Experimental Gonorrhea

2013 ◽  
Vol 82 (1) ◽  
pp. 184-192 ◽  
Author(s):  
Xiyou Zhou ◽  
Xi Gao ◽  
Peter M. Broglie ◽  
Chahnaz Kebaier ◽  
James E. Anderson ◽  
...  
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Lipid A ◽  
Innate Immune ◽  
Immune Recognition ◽  
Toll Like Receptor ◽  
Inflammatory Signaling ◽  
Toll Like Receptor 4 ◽  
Immune Signaling ◽  
Content Type ◽  
Innate Immune Signaling

ABSTRACTNeisseria gonorrhoeaecauses gonorrhea, a sexually transmitted infection characterized by inflammation of the cervix or urethra. However, a significant subset of patients withN. gonorrhoeaeremain asymptomatic, without evidence of localized inflammation. Inflammatory responses toN. gonorrhoeaeare generated by host innate immune recognition ofN. gonorrhoeaeby several innate immune signaling pathways, including lipooligosaccharide (LOS) and other pathogen-derived molecules through activation of innate immune signaling systems, including toll-like receptor 4 (TLR4) and the interleukin-1β (IL-1β) processing complex known as the inflammasome. The lipooligosaccharide ofN. gonorrhoeaehas a hexa-acylated lipid A.N. gonorrhoeaestrains that carry an inactivatedmsbB(also known aslpxL1) gene produce a penta-acylated lipid A and exhibit reduced biofilm formation, survival in epithelial cells, and induction of epithelial cell inflammatory signaling. We now show thatmsbB-deficientN. gonorrhoeaeinduces less inflammatory signaling in human monocytic cell lines and murine macrophages than the parent organism. The penta-acylated LOS exhibits reduced toll-like receptor 4 signaling but does not affectN. gonorrhoeae-mediated activation of the inflammasome. We demonstrate thatN. gonorrhoeaemsbBis dispensable for initiating and maintaining infection in a murine model of gonorrhea. Interestingly, infection withmsbB-deficientN. gonorrhoeaeis associated with less localized inflammation. Combined, these data suggest that TLR4-mediated recognition ofN. gonorrhoeaeLOS plays an important role in the pathogenesis of symptomatic gonorrhea infection and that alterations in lipid A biosynthesis may play a role in determining symptomatic and asymptomatic infections.

scholarly journals Lack of Lipid A Pyrophosphorylation and FunctionallptAReduces Inflammation by Neisseria Commensals

2012 ◽  
Vol 80 (11) ◽  
pp. 4014-4026 ◽  
Author(s):  
Constance M. John ◽  
Mingfeng Liu ◽  
Nancy J. Phillips ◽  
Zhijie Yang ◽  
Courtney R. Funk ◽  
...  
Keyword(s):  
Deletion Mutant ◽  
Lipid A ◽  
Polymyxin B ◽  
Toll Like Receptor ◽  
Inflammatory Signaling ◽  
Toll Like Receptor 4 ◽  
Bioinformatics Analyses ◽  
Monocytic Cells ◽  
Content Type ◽  
High Level

ABSTRACTThe interaction of the immune system withNeisseriacommensals remains poorly understood. We have previously shown that phosphoethanolamine on the lipid A portion of lipooligosaccharide (LOS) plays an important role in Toll-like receptor 4 (TLR4) signaling. For pathogenicNeisseria, phosphoethanolamine is added to lipid A by the phosphoethanolamine transferase specific for lipid A, which is encoded bylptA. Here, we report that Southern hybridizations and bioinformatics analyses of genomic sequences from all eight commensalNeisseriaspecies confirmed thatlptAwas absent in 15 of 17 strains examined but was present inN. lactamica. Mass spectrometry of lipid A and intact LOS revealed the lack of both pyrophosphorylation and phosphoethanolaminylation in lipid A of commensal species lackinglptA. Inflammatory signaling in human THP-1 monocytic cells was much greater with pathogenic than with commensalNeisseriastrains that lackedlptA, and greater sensitivity to polymyxin B was consistent with the absence of phosphoethanolamine. Unlike the other commensals, whole bacteria of twoN. lactamicacommensal strains had low inflammatory potential, whereas their lipid A had high-level pyrophosphorylation and phosphoethanolaminylation and induced high-level inflammatory signaling, supporting previous studies indicating that this species uses mechanisms other than altering lipid A to support commensalism. A meningococcallptAdeletion mutant had reduced inflammatory potential, further illustrating the importance of lipid A pyrophosphorylation and phosphoethanolaminylation in the bioactivity of LOS. Overall, our results indicate that lack of pyrophosphorylation and phosphoethanolaminylation of lipid A contributes to the immune privilege of most commensalNeisseriastrains by reducing the inflammatory potential of LOS.

scholarly journals Identification of PGN_1123 as the Gene Encoding Lipid A Deacylase, an Enzyme Required for Toll-Like Receptor 4 Evasion, inPorphyromonas gingivalis

2019 ◽  
Vol 201 (11) ◽  
Author(s):  
Sumita Jain ◽  
Ana M. Chang ◽  
Manjot Singh ◽  
Jeffrey S. McLean ◽  
Stephen R. Coats ◽  
...  
Keyword(s):  
Immune Response ◽  
Porphyromonas Gingivalis ◽  
Innate Immune Response ◽  
Lipid A ◽  
Innate Immune ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Gene Encoding ◽  
Content Type ◽  
Chronic Inflammatory Condition

ABSTRACTRemoval of one acyl chain from bacterial lipid A by deacylase activity is a mechanism used by many pathogenic bacteria to evade the host's Toll-like receptor 4 (TLR4)-mediated innate immune response. InPorphyromonas gingivalis, a periodontal pathogen, lipid A deacylase activity converts a majority of the initially synthesized penta-acylated lipid A, a TLR4 agonist, to tetra-acylated structures, which effectively evade TLR4 sensing by being either inert or antagonistic at TLR4. In this paper, we report successful identification of the gene that encodes theP. gingivalislipid A deacylase enzyme. This gene, PGN_1123 inP. gingivalis33277, is highly conserved withinP. gingivalis, and putative orthologs are phylogenetically restricted to theBacteroidetesphylum. Lipid A of ΔPGN_1123 mutants is penta-acylated and devoid of tetra-acylated structures, and the mutant strain provokes a strong TLR4-mediated proinflammatory response, in contrast to the negligible response elicited by wild-typeP. gingivalis. Heterologous expression of PGN_1123 inBacteroides thetaiotaomicronpromoted lipid A deacylation, confirming that PGN_1123 encodes the lipid A deacylase enzyme.IMPORTANCEPeriodontitis, commonly referred to as gum disease, is a chronic inflammatory condition that affects a large proportion of the population.Porphyromonas gingivalisis a bacterium closely associated with periodontitis, although how and if it is a cause for the disease are not known. It has a formidable capacity to dampen the host's innate immune response, enabling its persistence in diseased sites and triggering microbial dysbiosis in animal models of infection.P. gingivalisis particularly adept at evading the host's TLR4-mediated innate immune response by modifying the structure of lipid A, the TLR4 ligand. In this paper, we report identification of the gene encoding lipid A deacylase, a key enzyme that modifies lipid A to TLR4-evasive structures.

scholarly journals Innate immune signaling by Toll-like receptor-4 (TLR4) shapes the inflammatory microenvironment in colitis-associated tumors

2009 ◽  
Vol 15 (7) ◽  
pp. 997-1006 ◽  
Author(s):  
Masayuki Fukata ◽  
Yasmin Hernandez ◽  
Daisy Conduah ◽  
Jason Cohen ◽  
Anli Chen ◽  
...  
Keyword(s):  
Innate Immune ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Immune Signaling ◽  
Inflammatory Microenvironment ◽  
Innate Immune Signaling ◽  
Associated Tumors

scholarly journals Lipopolysaccharides from Different Burkholderia Species with Different Lipid A Structures Induce Toll-Like Receptor 4 Activation and React with Melioidosis Patient Sera

2019 ◽  
Vol 87 (12) ◽  
Author(s):  
Sineenart Sengyee ◽  
Sung Hwan Yoon ◽  
T. Eoin West ◽  
Robert K. Ernst ◽  
Narisara Chantratita
Keyword(s):  
Lipid A ◽  
Immunoblot Analysis ◽  
Immune Recognition ◽  
Pathogenic Species ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Content Type ◽  
Maldi Tof ◽  
Flight Mass Spectrometry ◽  
Sds Page

ABSTRACT Lipopolysaccharides (LPSs) of Gram-negative bacteria comprise lipid A, core, and O-polysaccharide (OPS) components. Studies have demonstrated that LPSs isolated from the pathogenic species Burkholderia pseudomallei and Burkholderia mallei and from less-pathogenic species, such as Burkholderia thailandensis, are potent immune stimulators. The LPS structure of B. pseudomallei, the causative agent of melioidosis, is highly conserved in isolates from Thailand; however, the LPSs isolated from other, related species have not been characterized to enable understanding of their immune recognition and antigenicities. Here, we describe the structural and immunological characteristics of the LPSs isolated from eight Burkholderia species and compare those for B. pseudomallei to those for the other seven species. Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS), gas chromatography (GC), SDS-PAGE, Toll-like receptor 4 (TLR4) stimulation, and immunoblot analysis were performed on these Burkholderia species. MALDI-TOF profiles demonstrated that Burkholderia lipid A contains predominantly penta-acylated species modified with 4-amino-4-deoxy-arabinose residues at both terminal phosphate groups. The lipid A could be differentiated based on mass differences at m/z 1,511, 1,642, 1,773, and 1,926 and on fatty acid composition. LPSs of all species induced TLR4-dependent NF-κB responses; however, while SDS-PAGE analysis showed similar LPS ladder patterns for B. pseudomallei, B. thailandensis, and B. mallei, these patterns differed from those of other Burkholderia species. Interestingly, immunoblot analysis demonstrated that melioidosis patient sera cross-reacted with OPSs of other Burkholderia species. These findings can be used to better understand the characteristics of LPS in Burkholderia species, and they have implications for serological diagnostics based on the detection of antibodies to OPS.

scholarly journals Hepacivirus NS3/4A Proteases Interfere with MAVS Signaling in both Their Cognate Animal Hosts and Humans: Implications for Zoonotic Transmission

2016 ◽  
Vol 90 (23) ◽  
pp. 10670-10681 ◽  
Author(s):  
Anggakusuma ◽  
Richard J. P. Brown ◽  
Dominic H. Banda ◽  
Daniel Todt ◽  
Gabrielle Vieyres ◽  
...  
Keyword(s):  
Mammalian Species ◽  
Companion Animals ◽  
Adaptor Protein ◽  
Innate Immune ◽  
Zoonotic Transmission ◽  
Common Mechanism ◽  
Zoonotic Potential ◽  
Immune Signaling ◽  
Content Type ◽  
Innate Immune Signaling

ABSTRACTMultiple novel members of the genusHepacivirushave recently been discovered in diverse mammalian species. However, to date, their replication mechanisms and zoonotic potential have not been explored in detail. The NS3/4A serine protease of hepatitis C virus (HCV) is critical for cleavage of the viral polyprotein. It also cleaves the cellular innate immune adaptor MAVS, thus decreasing interferon (IFN) production and contributing to HCV persistence in the human host. To investigate the conservation of fundamental aspects of the hepaciviral life cycle, we explored if MAVS cleavage and suppression of innate immune signaling represent a common mechanism employed across different clades of the genusHepacivirusto enhance viral replication. To estimate the zoonotic potential of these nonhuman hepaciviruses, we assessed if their NS3/4A proteases were capable of cleaving human MAVS. NS3/4A proteases of viruses infecting colobus monkeys, rodents, horses, and cows cleaved the MAVS proteins of their cognate hosts and interfered with the ability of MAVS to induce the IFN-β promoter. All NS3/4A proteases from nonhuman viruses readily cleaved human MAVS. Thus, NS3/4A-dependent cleavage of MAVS is a conserved replication strategy across multiple clades within the genusHepacivirus. Human MAVS is susceptible to cleavage by these nonhuman viral proteases, indicating that it does not pose a barrier for zoonotic transmission of these viruses to humans.IMPORTANCEVirus infection is recognized by cellular sensor proteins triggering innate immune signaling and antiviral defenses. While viruses have evolved strategies to thwart these antiviral programs in their cognate host species, these evasion mechanisms are often ineffective in a novel host, thus limiting viral transmission across species. HCV, the best-characterized member of the genusHepaciviruswithin the familyFlaviviridae, uses its NS3/4A protease to disrupt innate immune signaling by cleaving the cellular adaptor protein MAVS. Recently, a large number of HCV-related viruses have been discovered in various animal species, including wild, livestock, and companion animals. We show that the NS3/4A proteases of these hepaciviruses from different animals and representing various clades of the genus cleave their cognate host MAVS proteins in addition to human MAVS. Therefore, cleavage of MAVS is a common strategy of hepaciviruses, and human MAVS is likely unable to limit replication of these nonhuman viruses upon zoonotic exposure.

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.

Interactions between Viperin, IRAK1 andTRAF6 couple innate immune signaling to antiviral ribonucleotide synthesis

2018 ◽  
Author(s):  
Arti B. Dumbrepatil ◽  
Soumi Ghosh ◽  
Ayesha M. Patel ◽  
Kelcie A. Zegalia ◽  
Paige A. Malec ◽  
...  
Keyword(s):  
Structural Changes ◽  
Interleukin 1 ◽  
Innate Immune ◽  
Tnf Receptor ◽  
Toll Like Receptor ◽  
Immune Signaling ◽  
Innate Immune Signaling ◽  
Synergistic Activation ◽  
Catalytically Active ◽  
Cellular Antiviral Response

SummaryViperin is a radical S-adenosylmethionine (SAM) enzyme that plays a multifaceted role in the cellular antiviral response. Viperin was recently shown to catalyze the SAM-dependent formation of 3′-deoxy-3′,4′-didehydro-CTP (ddhCTP), which inhibits some viral RNA polymerases. Viperin is also implicated in regulating K63-linked poly-ubiquitination of interleukin-1 receptor-associated kinase-1 (IRAK1) by the E3 ubiquitin ligase TNF Receptor-Associated Factor 6 (TRAF6) as part of the Toll-like receptor-7 and 9 (TLR7/9) innate immune signaling pathways. We show that IRAK1 and TRAF6 activate viperin to efficiently catalyze the radical-mediated dehydration of CTP to ddhCTP. Furthermore, poly-ubiquitination of IRAK1 requires the association of viperin with IRAK1 and TRAF6. Poly-ubiquitination appears dependent on structural changes induced by SAM binding to viperin but does not require catalytically active viperin. The synergistic activation of viperin and IRAK1 provides a mechanism that couples innate immune signaling with the production of the antiviral nucleotide ddhCTP.

scholarly journals Critical Role for MyD88-Mediated Neutrophil Recruitment during Clostridium difficile Colitis

2012 ◽  
Vol 80 (9) ◽  
pp. 2989-2996 ◽  
Author(s):  
Irene Jarchum ◽  
Mingyu Liu ◽  
Chao Shi ◽  
Michele Equinda ◽  
Eric G. Pamer
Keyword(s):  
Clostridium Difficile ◽  
Inflammatory Responses ◽  
Adaptor Protein ◽  
Neutrophil Recruitment ◽  
Innate Immune ◽  
Antibiotic Administration ◽  
Immune Signaling ◽  
Content Type ◽  
Innate Immune Signaling ◽  
Deficient Mice

ABSTRACTClostridium difficilecan infect the large intestine and cause colitis when the normal intestinal microbiota is altered by antibiotic administration. Little is known about the innate immune signaling pathways that marshal inflammatory responses toC. difficileinfection and whether protective and pathogenic inflammatory responses can be dissociated. Toll-like receptors predominantly signal via the MyD88 adaptor protein and are important mediators of innate immune signaling in the intestinal mucosa. Here, we demonstrate that MyD88-mediated signals trigger neutrophil and CCR2-dependent Ly6Chimonocyte recruitment to the colonic lamina propria (cLP) during infection, which prevent dissemination of bystander bacteria to deeper tissues. Mortality is markedly increased in MyD88-deficient mice followingC. difficileinfection, as are parameters of mucosal tissue damage and inflammation. Antibody-mediated depletion of neutrophils markedly increases mortality, while attenuated recruitment of Ly6Chimonocytes in CCR2-deficient mice does not alter the course ofC. difficileinfection. Expression of CXCL1, a neutrophil-recruiting chemokine, is impaired in the cLP of MyD88−/−mice. Our studies suggest that MyD88-mediated signals promote neutrophil recruitment by inducing expression of CXCL1, thereby providing critical early defense againstC. difficile-mediated colitis.

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