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Zenobia C, Herpoldt KL, Freire M. Is the oral microbiome a source to enhance mucosal immunity against infectious diseases? NPJ Vaccines 2021; 6:80. [PMID: 34078913 PMCID: PMC8172910 DOI: 10.1038/s41541-021-00341-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 04/24/2021] [Indexed: 12/14/2022] Open
Abstract
Mucosal tissues act as a barrier throughout the oral, nasopharyngeal, lung, and intestinal systems, offering first-line protection against potential pathogens. Conventionally, vaccines are applied parenterally to induce serotype-dependent humoral response but fail to drive adequate mucosal immune protection for viral infections such as influenza, HIV, and coronaviruses. Oral mucosa, however, provides a vast immune repertoire against specific microbial pathogens and yet is shaped by an ever-present microbiome community that has co-evolved with the host over thousands of years. Adjuvants targeting mucosal T-cells abundant in oral tissues can promote soluble-IgA (sIgA)-specific protection to confer increased vaccine efficacy. Th17 cells, for example, are at the center of cell-mediated immunity and evidence demonstrates that protection against heterologous pathogen serotypes is achieved with components from the oral microbiome. At the point of entry where pathogens are first encountered, typically the oral or nasal cavity, the mucosal surfaces are layered with bacterial cohabitants that continually shape the host immune profile. Constituents of the oral microbiome including their lipids, outer membrane vesicles, and specific proteins, have been found to modulate the Th17 response in the oral mucosa, playing important roles in vaccine and adjuvant designs. Currently, there are no approved adjuvants for the induction of Th17 protection, and it is critical that this research is included in the preparedness for the current and future pandemics. Here, we discuss the potential of oral commensals, and molecules derived thereof, to induce Th17 activity and provide safer and more predictable options in adjuvant engineering to prevent emerging infectious diseases.
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Affiliation(s)
| | | | - Marcelo Freire
- Departments of Genomic Medicine and Infectious Diseases, J. Craig Venter Institute, La Jolla, CA, USA.
- Division of Infectious Diseases and Global Public Health, Department of Medicine, University of California San Diego, La Jolla, CA, USA.
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Swietnicki W, Caspi R. Prediction of Selected Biosynthetic Pathways for the Lipopolysaccharide Components in Porphyromonas gingivalis. Pathogens 2021; 10:pathogens10030374. [PMID: 33804654 PMCID: PMC8003790 DOI: 10.3390/pathogens10030374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 03/16/2021] [Accepted: 03/17/2021] [Indexed: 11/16/2022] Open
Abstract
Porphyromonas gingivalis is an oral human pathogen. The bacterium destroys dental tissue and is a serious health problem worldwide. Experimental data and bioinformatic analysis revealed that the pathogen produces three types of lipopolysaccharides (LPS): normal (O-type), anionic (A-type), and capsular (K-type). The enzymes involved in the production of all three types of lipopolysaccharide have been largely identified for the first two and partially for the third type. In the current work, we use bioinformatics tools to predict biosynthetic pathways for the production of the normal (O-type) lipopolysaccharide in the W50 strain Porphyromonas gingivalis and compare the pathway with other putative pathways in fully sequenced and completed genomes of other pathogenic strains. Selected enzymes from the pathway have been modeled and putative structures are presented. The pathway for the A-type antigen could not be predicted at this time due to two mutually exclusive structures proposed in the literature. The pathway for K-type antigen biosynthesis could not be predicted either due to the lack of structural data for the antigen. However, pathways for the synthesis of lipid A, its core components, and the O-type antigen ligase reaction have been proposed based on a combination of experimental data and bioinformatic analyses. The predicted pathways are compared with known pathways in other systems and discussed. It is the first report in the literature showing, in detail, predicted pathways for the synthesis of selected LPS components for the model W50 strain of P. gingivalis.
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Affiliation(s)
- Wieslaw Swietnicki
- Department of Immunology of Infectious Diseases, L. Hirszfeld Institute of Immunology and Experimental Therapy of PAS, ul. R. Weigla 12, 53-114 Wroclaw, Poland
- Correspondence:
| | - Ron Caspi
- Artificial Intelligence Center, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493, USA;
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3
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Kawahara K. Variation, Modification and Engineering of Lipid A in Endotoxin of Gram-Negative Bacteria. Int J Mol Sci 2021; 22:2281. [PMID: 33668925 PMCID: PMC7956469 DOI: 10.3390/ijms22052281] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/20/2021] [Accepted: 02/22/2021] [Indexed: 12/12/2022] Open
Abstract
Lipid A of Gram-negative bacteria is known to represent a central role for the immunological activity of endotoxin. Chemical structure and biosynthetic pathways as well as specific receptors on phagocytic cells had been clarified by the beginning of the 21st century. Although the lipid A of enterobacteria including Escherichia coli share a common structure, other Gram-negative bacteria belonging to various classes of the phylum Proteobacteria and other taxonomical groups show wide variety of lipid A structure with relatively decreased endotoxic activity compared to that of E. coli. The structural diversity is produced from the difference of chain length of 3-hydroxy fatty acids and non-hydroxy fatty acids linked to their hydroxyl groups. In some bacteria, glucosamine in the backbone is substituted by another amino sugar, or phosphate groups bound to the backbone are modified. The variation of structure is also introduced by the enzymes that can modify electrostatic charges or acylation profiles of lipid A during or after its synthesis. Furthermore, lipid A structure can be artificially modified or engineered by the disruption and introduction of biosynthetic genes especially those of acyltransferases. These technologies may produce novel vaccine adjuvants or antagonistic drugs derived from endotoxin in the future.
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Affiliation(s)
- Kazuyoshi Kawahara
- Department of Biosciences, College of Science and Engineering, Kanto Gakuin University, Yokohama, Kanagawa 236-8501, Japan
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4
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Bacterial Periplasmic Oxidoreductases Control the Activity of Oxidized Human Antimicrobial β-Defensin 1. Infect Immun 2018; 86:IAI.00875-17. [PMID: 29378796 DOI: 10.1128/iai.00875-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 01/18/2018] [Indexed: 12/21/2022] Open
Abstract
The antimicrobial peptide human β-defensin 1 (hBD1) is continuously produced by epithelial cells in many tissues. Compared to other defensins, hBD1 has only minor antibiotic activity in its native state. After reduction of its disulfide bridges, however, it becomes a potent antimicrobial agent against bacteria, while the oxidized native form (hBD1ox) shows specific activity against Gram-negative bacteria. We show that the killing mechanism of hBD1ox depends on aerobic growth conditions and bacterial enzymes. We analyzed the different activities of hBD1 using mutants of Escherichia coli lacking one or more specific proteins of their outer membrane, cytosol, or redox systems. We discovered that DsbA and DsbB are essential for the antimicrobial activity of hBD1ox but not for that of reduced hBD1 (hBD1red). Furthermore, our results strongly suggest that hBD1ox uses outer membrane protein FepA to penetrate the bacterial periplasm space. In contrast, other bacterial proteins in the outer membrane and cytosol did not modify the antimicrobial activity. Using immunogold labeling, we identified the localization of hBD1ox in the periplasmic space and partly in the outer membrane of E. coli However, in resistant mutants lacking DsbA and DsbB, hBD1ox was detected mainly in the bacterial cytosol. In summary, we discovered that hBD1ox could use FepA to enter the periplasmic space, where its activity depends on presence of DsbA and DsbB. HBD1ox concentrates in the periplasm in Gram-negative bacteria, which finally leads to bleb formation and death of the bacteria. Thus, the bacterial redox system plays an essential role in mechanisms of resistance against host-derived peptides such as hBD1.
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Sochalska M, Potempa J. Manipulation of Neutrophils by Porphyromonas gingivalis in the Development of Periodontitis. Front Cell Infect Microbiol 2017; 7:197. [PMID: 28589098 PMCID: PMC5440471 DOI: 10.3389/fcimb.2017.00197] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 05/04/2017] [Indexed: 12/31/2022] Open
Abstract
The pathogenesis of the chronic periodontal disease is associated with a skewed host inflammatory response to periodontal pathogens, such as Porphyromonas gingivalis, that accounts for the majority of periodontal tissue damage. Neutrophils are the most abundant leukocytes in periodontal pockets and depending on the stage of the disease, also plentiful PMNs are present in the inflamed gingival tissue and the gingival crevice. They are the most efficient phagocytes and eliminate pathogens by a variety of means, which are either oxygen-dependent or -independent. However, these secretory lethal weapons do not strictly discriminate between pathogens and host tissue. Current studies describe conflicting findings about neutrophil involvement in periodontal disease. On one hand literature indicate that hyper-reactive neutrophils are the main immune cell type responsible for this observed tissue damage and disease progression. Deregulation of neutrophil survival and functions, such as chemotaxis, migration, secretion of antimicrobial peptides or enzymes, and production of reactive oxygen species, contribute to observed tissue injury and the clinical signs of periodontal disease. On the other hand neutrophils deficiencies in patients and mice also result in periodontal phenotype. Therefore, P. gingivalis represents a periodontal pathogen that manipulates the immune responses of PMNs, employing several virulence factors, such as gingipains, serine proteases, lipid phosphatases, or fimbriae. This review will sum up studies devoted to understanding different strategies utilized by P. gingivalis to manipulate PMNs survival and functions in order to inhibit killing by a granular content, prolong inflammation, and gain access to nutrient resources.
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Affiliation(s)
- Maja Sochalska
- Department of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian UniversityKrakow, Poland
| | - Jan Potempa
- Department of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian UniversityKrakow, Poland.,Department of Oral Immunology and Infectious Diseases, School of Dentistry, University of LouisvilleLouisville, KY, United States
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6
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Lipid A structural modifications in extreme conditions and identification of unique modifying enzymes to define the Toll-like receptor 4 structure-activity relationship. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1439-1450. [PMID: 28108356 DOI: 10.1016/j.bbalip.2017.01.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 01/10/2017] [Accepted: 01/12/2017] [Indexed: 01/23/2023]
Abstract
Strategies utilizing Toll-like receptor 4 (TLR4) agonists for treatment of cancer, infectious diseases, and other targets report promising results. Potent TLR4 antagonists are also gaining attention as therapeutic leads. Though some principles for TLR4 modulation by lipid A have been described, a thorough understanding of the structure-activity relationship (SAR) is lacking. Only through a complete definition of lipid A-TLR4 SAR is it possible to predict TLR4 signaling effects of discrete lipid A structures, rendering them more pharmacologically relevant. A limited 'toolbox' of lipid A-modifying enzymes has been defined and is largely composed of enzymes from mesophile human and zoonotic pathogens. Expansion of this 'toolbox' will result from extending the search into lipid A biosynthesis and modification by bacteria living at the extremes. Here, we review the fundamentals of lipid A structure, advances in lipid A uses in TLR4 modulation, and the search for novel lipid A-modifying systems in extremophile bacteria. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.
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Microbiome and chronic inflammatory bowel diseases. J Mol Med (Berl) 2016; 95:21-28. [PMID: 27988792 DOI: 10.1007/s00109-016-1495-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 11/15/2016] [Accepted: 11/25/2016] [Indexed: 01/12/2023]
Abstract
It is nowadays generally accepted that the microbiome is a central driver of chronic inflammatory bowel diseases based on observations from human patients as well as inflammatory rodent models. Many studies focussed on different aspects of microbiota and some scientists believe that a primary dis-balance results in a direct microbial induced inflammatory situation. It is also clear that the microbiome is influenced by environmental and genetic factors and is also tightly regulated by host defense molecules such as antimicrobial peptides (defensins et al.). Different lines of investigations showed different complex antimicrobial barrier defects in inflammatory bowel diseases which also influence the composition of the microbiome and generally impact on the microbial-mucosal interface. In this review, we aim to discuss the bigger picture of these different aspects and current views and conclude about therapeutic consequences for future concepts beyond anti-inflammatory treatment.
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Steimle A, Autenrieth IB, Frick JS. Structure and function: Lipid A modifications in commensals and pathogens. Int J Med Microbiol 2016; 306:290-301. [DOI: 10.1016/j.ijmm.2016.03.001] [Citation(s) in RCA: 189] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 03/01/2016] [Accepted: 03/02/2016] [Indexed: 02/07/2023] Open
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Chen Z, Su L, Xu Q, Katz J, Michalek SM, Fan M, Feng X, Zhang P. IL-1R/TLR2 through MyD88 Divergently Modulates Osteoclastogenesis through Regulation of Nuclear Factor of Activated T Cells c1 (NFATc1) and B Lymphocyte-induced Maturation Protein-1 (Blimp1). J Biol Chem 2015; 290:30163-74. [PMID: 26483549 DOI: 10.1074/jbc.m115.663518] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Indexed: 01/10/2023] Open
Abstract
Toll-like receptors (TLR) and the receptor for interleukin-1 (IL-1R) signaling play an important role in bacteria-mediated bone loss diseases including periodontitis, rheumatoid arthritis, and osteomyelitis. Recent studies have shown that TLR ligands inhibit the receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation from un-committed osteoclast precursors, whereas IL-1 potentiates RANKL-induced osteoclast formation. However, IL-1R and TLR belong to the same IL-1R/TLR superfamily, and activate similar intracellular signaling pathways. Here, we investigate the molecular mechanisms underlying the distinct effects of IL-1 and Porphyromonas gingivalis lipopolysaccharide (LPS-PG) on RANKL-induced osteoclast formation. Our results show that LPS-PG and IL-1 differentially regulate RANKL-induced activation of osteoclast genes encoding Car2, Ctsk, MMP9, and TRAP, as well as expression of NFATc1, a master transcription factor of osteoclastogenesis. Regulation of osteoclast genes and NFATc1 by LPS-PG and IL-1 is dependent on MyD88, an important signaling adaptor for both TLR and IL-1R family members. Furthermore, LPS-PG and IL-1 differentially regulate RANKL-costimulatory receptor OSCAR (osteoclast-associated receptor) expression and Ca(2+) oscillations induced by RANKL. Moreover, LPS-PG completely abrogates RANKL-induced gene expression of B lymphocyte-induced maturation protein-1 (Blimp1), a global transcriptional repressor of anti-osteoclastogenic genes encoding Bcl6, IRF8, and MafB. However, IL-1 enhances RANKL-induced blimp1 gene expression but suppresses the gene expression of bcl6, irf8, and mafb. Our study reveals the involvement of multiple signaling molecules in the differential regulation of RANKL-induced osteoclastogenesis by TLR2 and IL-1 signaling. Understanding the signaling cross-talk among TLR, IL-1R, and RANK is critical for identifying therapeutic strategies to control bacteria-mediated bone loss.
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Affiliation(s)
- Zhihong Chen
- From the Departments of Pediatric Dentistry, the Department of Prosthodontics, School and Hospital of Stomatology, Zhejiang University, Hangzhou, Zhejiang 310006, China, and
| | - Lingkai Su
- From the Departments of Pediatric Dentistry
| | - Qingan Xu
- From the Departments of Pediatric Dentistry, the The State Key Laboratory Breeding Base of Basic Science of Stomatology and Key Laboratory of Oral Biomedicine of Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei 430079, China
| | - Jenny Katz
- From the Departments of Pediatric Dentistry
| | | | - Mingwen Fan
- the The State Key Laboratory Breeding Base of Basic Science of Stomatology and Key Laboratory of Oral Biomedicine of Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, Hubei 430079, China
| | - Xu Feng
- Pathology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Ping Zhang
- From the Departments of Pediatric Dentistry,
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Di Lorenzo F, Kubik Ł, Oblak A, Lorè NI, Cigana C, Lanzetta R, Parrilli M, Hamad MA, De Soyza A, Silipo A, Jerala R, Bragonzi A, Valvano MA, Martín-Santamaría S, Molinaro A. Activation of Human Toll-like Receptor 4 (TLR4)·Myeloid Differentiation Factor 2 (MD-2) by Hypoacylated Lipopolysaccharide from a Clinical Isolate of Burkholderia cenocepacia. J Biol Chem 2015; 290:21305-19. [PMID: 26160169 DOI: 10.1074/jbc.m115.649087] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Indexed: 11/06/2022] Open
Abstract
Lung infection by Burkholderia species, in particular Burkholderia cenocepacia, accelerates tissue damage and increases post-lung transplant mortality in cystic fibrosis patients. Host-microbe interplay largely depends on interactions between pathogen-specific molecules and innate immune receptors such as Toll-like receptor 4 (TLR4), which recognizes the lipid A moiety of the bacterial lipopolysaccharide (LPS). The human TLR4·myeloid differentiation factor 2 (MD-2) LPS receptor complex is strongly activated by hexa-acylated lipid A and poorly activated by underacylated lipid A. Here, we report that B. cenocepacia LPS strongly activates human TLR4·MD-2 despite its lipid A having only five acyl chains. Furthermore, we show that aminoarabinose residues in lipid A contribute to TLR4-lipid A interactions, and experiments in a mouse model of LPS-induced endotoxic shock confirmed the proinflammatory potential of B. cenocepacia penta-acylated lipid A. Molecular modeling combined with mutagenesis of TLR4-MD-2 interactive surfaces suggests that longer acyl chains and the aminoarabinose residues in the B. cenocepacia lipid A allow exposure of the fifth acyl chain on the surface of MD-2 enabling interactions with TLR4 and its dimerization. Our results provide a molecular model for activation of the human TLR4·MD-2 complex by penta-acylated lipid A explaining the ability of hypoacylated B. cenocepacia LPS to promote proinflammatory responses associated with the severe pathogenicity of this opportunistic bacterium.
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Affiliation(s)
- Flaviana Di Lorenzo
- From the Departments of Chemical Sciences and Department of Biotechnology, National Institute of Chemistry, Ljubljana 1000, Slovenia
| | - Łukasz Kubik
- Department of Chemistry and Biochemistry, Universidad CEU San Pablo, Boadilla del Monte, Madrid 28668, Spain, Department of Biopharmaceutics and Pharmacodynamics, Medical University of Gdańsk, Gdańsk 80-416, Poland
| | - Alja Oblak
- Department of Biotechnology, National Institute of Chemistry, Ljubljana 1000, Slovenia, Centre of Excellence NMR - Future Innovation for Sustainable Technologies, Ljubljana 1000, Slovenia
| | - Nicola Ivan Lorè
- Infection and Cystic Fibrosis Unit, Istituto di Ricovero e Cura a Carattere Scientifico-San Raffaele Scientific Institute, Milan 20132, Italy
| | - Cristina Cigana
- Infection and Cystic Fibrosis Unit, Istituto di Ricovero e Cura a Carattere Scientifico-San Raffaele Scientific Institute, Milan 20132, Italy
| | | | | | - Mohamad A Hamad
- Department of Microbiology and Immunology, University of Western Ontario, London N6A 5C1, Canada
| | - Anthony De Soyza
- Applied Immunobiology and Transplantation Group, Institute of Cellular Medicine, University of Newcastle, Newcastle NE1 7RU, United Kingdom, and
| | - Alba Silipo
- From the Departments of Chemical Sciences and
| | - Roman Jerala
- Department of Biotechnology, National Institute of Chemistry, Ljubljana 1000, Slovenia, Centre of Excellence NMR - Future Innovation for Sustainable Technologies, Ljubljana 1000, Slovenia
| | - Alessandra Bragonzi
- Infection and Cystic Fibrosis Unit, Istituto di Ricovero e Cura a Carattere Scientifico-San Raffaele Scientific Institute, Milan 20132, Italy
| | - Miguel A Valvano
- Department of Microbiology and Immunology, University of Western Ontario, London N6A 5C1, Canada, Centre for Infection and Immunity, Queen's University Belfast, Belfast BT9 7AE, United Kingdom
| | - Sonsoles Martín-Santamaría
- Department of Chemistry and Biochemistry, Universidad CEU San Pablo, Boadilla del Monte, Madrid 28668, Spain,
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Zariri A, van der Ley P. Biosynthetically engineered lipopolysaccharide as vaccine adjuvant. Expert Rev Vaccines 2015; 14:861-76. [PMID: 25797360 DOI: 10.1586/14760584.2015.1026808] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Lipopolysaccharide (LPS), a dominant component of the Gram-negative bacterial outer membrane, is a strong activator of the innate immune system, and thereby an important determinant in the adaptive immune response following bacterial infection. This adjuvant activity can be harnessed following immunization with bacteria-derived vaccines that naturally contain LPS, and when LPS or molecules derived from it are added to purified vaccine antigens. However, the downside of the strong biological activity of LPS is its ability to contribute to vaccine reactogenicity. Modification of the LPS structure allows triggering of a proper immune response needed in a vaccine against a particular pathogen while at the same time lowering its toxicity. Extensive modifications to the basic structure are possible by using our current knowledge of bacterial genes involved in LPS biosynthesis and modification. This review focuses on biosynthetic engineering of the structure of LPS and implications of these modifications for generation of safe adjuvants.
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Affiliation(s)
- Afshin Zariri
- Institute for Translational Vaccinology (InTraVacc), Antonie van Leeuwenhoeklaan 9, 3721 MA Bilthoven, The Netherlands
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12
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Abstract
BACKGROUND Toll-like receptor (TLR) expression in patients with inflammatory bowel disease is increased when compared with healthy controls. However, the impact of TLR signaling during inflammatory bowel disease is not fully understood. METHODS In this study, we used a murine model of acute phase inflammation in bone marrow chimeric mice to investigate in which cell type TLR2/4 signal induction is important in preventing intestinal inflammation and how intestinal dendritic cells are influenced. Mice were either fed with wild-type bacteria, able to initiate the TLR2/4 signaling cascade, or with mutant strains with impaired signal induction capacity. RESULTS The induction of the TLR2/4 signal cascade in epithelial cells resulted in inflammation in bone marrow chimeric mice, whereas induction in hematopoietic cells had an opposed function. Furthermore, feeding of wild-type bacteria prevented disease; however, differing signal induction of bacteria had no effect on lamina propria dendritic cell activation. In contrast, functional TLR2/4 signals resulted in increased frequencies of CD103-expressing lamina propria and mesenteric lymph node dendritic cells, which were able to ameliorate disease. CONCLUSIONS The TLR-mediated amelioration of disease, the increase in CD103-expressing cells, and the beneficial function of TLR signal induction in hematopoietic cells indicate that the increased expression of TLRs in patients with inflammatory bowel disease might result in counterregulation of the host and serve in preventing disease.
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Gronbach K, Flade I, Holst O, Lindner B, Ruscheweyh HJ, Wittmann A, Menz S, Schwiertz A, Adam P, Stecher B, Josenhans C, Suerbaum S, Gruber AD, Kulik A, Huson D, Autenrieth IB, Frick JS. Endotoxicity of lipopolysaccharide as a determinant of T-cell-mediated colitis induction in mice. Gastroenterology 2014; 146:765-75. [PMID: 24269927 DOI: 10.1053/j.gastro.2013.11.033] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Revised: 11/05/2013] [Accepted: 11/12/2013] [Indexed: 01/21/2023]
Abstract
BACKGROUND & AIMS The intestinal microbiota is an important determinant of the mucosal response. In patients with inflammatory bowel diseases, the mucosal immune system has inappropriate interactions with the intestinal microbiota. We investigated how the composition of the intestinal microbiota affects its endotoxicity and development of colitis in mice. METHODS Germ-free C57BL/6J-Rag(1tm1Mom) (Rag1(-/-)) mice were colonized with 2 different types of complex intestinal microbiota. Colitis was induced in Rag1(-/-) mice by transfer of CD4(+)CD62L(+) T cells from C57BL/6J mice. Colonic tissues were collected and used for histologic analysis and cell isolation. Activation of lamina propria dendritic cells and T cells was analyzed by flow cytometry. RESULTS After transfer of CD4(+)CD62L(+) T cells, mice with intestinal Endo(lo) microbiota (a low proportion of Enterobacteriaceae, high proportion of Bacteroidetes, and low endotoxicity) maintained mucosal immune homeostasis, and mice with highly endotoxic Endo(hi) microbiota (a high proportion of Enterobacteriaceae and low proportion of Bacteroidetes) developed colitis. To determine whether the effects of Endo(hi) microbiota were related to the higher endotoxic activity of lipopolysaccharide (LPS), we compared LPS from Enterobacteriaceae with that of Bacteroidetes. Administration of Escherichia coli JM83 (wild-type LPS) to the mice exacerbated colitis, and Escherichia coli JM83 + htrBPG (mutated LPS, with lower endotoxicity, similar to that of Bacteroidetes) prevented development of colitis after transfer of the T cells to mice. CONCLUSIONS The endotoxicity of LPS produced by the intestinal microbiota is a determinant of whether mice develop colitis after transfer of CD4(+)CD62L(+) T cells. This finding might aid the design of novel biologics or probiotics to treat inflammatory bowel disease.
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Affiliation(s)
- Kerstin Gronbach
- Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany; German Centre for Infection Research (DZIF), Germany
| | - Isabell Flade
- Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany; German Centre for Infection Research (DZIF), Germany
| | - Otto Holst
- Division of Structural Biochemistry, Research Center Borstel, Airway Research Center North (ARCN) and German Center for Lung Research (DZL), Borstel, Germany
| | - Buko Lindner
- Division of Immunochemistry, Research Center Borstel, Airway Research Center North (ARCN) and German Center for Lung Research (DZL), Borstel, Germany
| | - Hans Joachim Ruscheweyh
- Algorithms in Bioinformatics, ZBIT Center for Bioinformatics, University of Tübingen, Tübingen, Germany
| | - Alexandra Wittmann
- Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany; German Centre for Infection Research (DZIF), Germany
| | - Sarah Menz
- Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany; German Centre for Infection Research (DZIF), Germany
| | | | - Patrick Adam
- Institute of Pathology, University of Tübingen, Tübingen, Germany
| | - Bärbel Stecher
- German Centre for Infection Research (DZIF), Germany; Max von Pettenkofer-Institute of Hygiene and Medical Microbiology, Ludwig-Maximilians-University, Munich, Germany
| | - Christine Josenhans
- German Centre for Infection Research (DZIF), Germany; Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Hannover, Germany
| | - Sebastian Suerbaum
- German Centre for Infection Research (DZIF), Germany; Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Hannover, Germany
| | - Achim D Gruber
- Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Andreas Kulik
- Institute for Microbiology, University of Tübingen, Tübingen, Germany
| | - Daniel Huson
- Algorithms in Bioinformatics, ZBIT Center for Bioinformatics, University of Tübingen, Tübingen, Germany
| | - Ingo B Autenrieth
- Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany; German Centre for Infection Research (DZIF), Germany
| | - Julia-Stefanie Frick
- Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany; German Centre for Infection Research (DZIF), Germany.
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14
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Scior T, Alexander C, Zaehringer U. Reviewing and identifying amino acids of human, murine, canine and equine TLR4 / MD-2 receptor complexes conferring endotoxic innate immunity activation by LPS/lipid A, or antagonistic effects by Eritoran, in contrast to species-dependent modulation by lipid IVa. Comput Struct Biotechnol J 2013; 5:e201302012. [PMID: 24688705 PMCID: PMC3962135 DOI: 10.5936/csbj.201302012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Revised: 02/12/2013] [Accepted: 02/17/2013] [Indexed: 11/28/2022] Open
Abstract
There is literature evidence gathered throughout the last two decades reflecting unexpected species differences concerning the immune response to lipid IVa which provides the opportunity to gain more detailed insight by the molecular modeling approach described in this study. Lipid IVa is a tetra-acylated precursor of lipid A in the biosynthesis of lipopolysaccharide (LPS) in Gram-negative bacteria. Lipid A of the prototypic E. coli-type is a hexa-acylated structure that acts as an agonist in all tested mammalian species by innate immunorecognition via the Toll-like receptor 4 (TLR4)/myeloid differentiation factor 2 (MD-2) receptor complex. In contrast, lipid IVa is proinflammatory in mouse cells (agonism) but it remains inactive to human macrophages and even antagonizes the action of potent agonists like E. coli-type lipid A. This particular ambivalent activity profile of lipid IVa has been confirmed in other mammalian species: in equine cells Lipid IVa also acts in a weak agonistic manner, whereas being inactive and antagonizing the lipid A-induced activation of canine TLR4/MD-2. Intriguingly, the respective TLR4 amino acid sequences of the latter species are more identical to the human (67%, 68%) than to the murine (62%, 58%) ortholog. In order to address the unpaired activity-sequence dualism for human, murine, canine and equine species regarding the activity of lipid IVa as compared to LPS and lipid A and, we review the literature and computationally pinpoint the differential biological effects of lipid IVa versus LPS and lipid A to specific amino acid residues. In contrast to lipid IVa the structurally related synthetic compound Eritoran (E5564) acts consistently in an antagonistic manner in these mammalian species and serves as a reference ligand for molecular modeling in this study. The combined evaluation of data sets provided by prior studies and in silico homology mapping of differential residues of TLR4/MD-2 complexes lends detailed insight into the driving forces of the characteristic binding modes of the lipid A domain in LPS and the precursor structure lipid IVa to the receptor complex in individual mammalian species.
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Affiliation(s)
- Thomas Scior
- Departamento de Farmacia, Benemerita Universidad Autonoma de Puebla, C.P. 72570 Puebla, Pue., Mexico
| | - Christian Alexander
- Division of Immunochemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Borstel, Germany
| | - Ulrich Zaehringer
- Division of Immunochemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Borstel, Germany
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The expression and regulation of matrix metalloproteinase-3 is critically modulated by Porphyromonas gingivalis lipopolysaccharide with heterogeneous lipid A structures in human gingival fibroblasts. BMC Microbiol 2013; 13:73. [PMID: 23548063 PMCID: PMC3623786 DOI: 10.1186/1471-2180-13-73] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 03/15/2013] [Indexed: 12/31/2022] Open
Abstract
Background Porphyromonas gingivalis lipopolysaccharide (LPS) is a crucial virulence factor strongly associated with chronic periodontitis which is the primary cause of tooth loss in adults. It exhibits remarkable heterogeneity containing tetra-(LPS1435/1449) and penta-(LPS1690) acylated lipid A structures. Human gingival fibroblasts (HGFs) as the main resident cells of human gingiva play a key role in regulating matrix metalloproteinases (MMPs) and contribute to periodontal homeostasis. This study investigated the expression and regulation of MMPs1-3 and tissue inhibitors of MMP-1 (TIMP-1) in HGFs in response to P. gingivalis LPS1435/1449 and LPS1690 and hexa-acylated E. coli LPS as a reference. The expression of MMPs 1–3 and TIMP-1 was evaluated by real-time PCR and ELISA. Results The MMP-3 mRNA and protein were highly upregulated in P. gingivalis LPS1690- and E. coli LPS-treated cells, whereas no induction was observed in P. gingivalis LPS1435/1449-treated cells. On the contrary, the expression of MMP-1 and −2 was not significantly affected by P. gingivalis LPS lipid A heterogeneity. The TIMP-1 mRNA was upregulated in P. gingivalis LPS1435/1449- and E. coli LPS-treated cells. Next, signal transduction pathways involved in P. gingivalis LPS-induced expression of MMP-3 were examined by blocking assays. Blockage of p38 MAPK and ERK significantly inhibited P. gingivalis LPS1690-induced MMP-3 expression in HGFs. Conclusion The present findings suggest that the heterogeneous lipid A structures of P. gingivalis LPS differentially modulate the expression of MMP-3 in HGFs, which may play a role in periodontal pathogenesis.
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Herath TDK, Darveau RP, Seneviratne CJ, Wang CY, Wang Y, Jin L. Tetra- and penta-acylated lipid A structures of Porphyromonas gingivalis LPS differentially activate TLR4-mediated NF-κB signal transduction cascade and immuno-inflammatory response in human gingival fibroblasts. PLoS One 2013; 8:e58496. [PMID: 23554896 PMCID: PMC3595299 DOI: 10.1371/journal.pone.0058496] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 02/05/2013] [Indexed: 12/21/2022] Open
Abstract
Background Porphyromonas gingivalis is a major pathogen of periodontal disease that affects a majority of adults worldwide. Increasing evidence shows that periodontal disease is linked to various systemic diseases like diabetes and cardiovascular disease, by contributing to increased systemic levels of inflammation. Lipopolysaccharides (LPS), as a key virulent attribute of P. gingivalis, possesses significant amount of lipid A heterogeneity containing tetra- (LPS1435/1449) and penta-acylated (LPS1690) structures. Hitherto, the exact molecular mechanism of P. gingivalis LPS involved in periodontal pathogenesis remains unclear, due to limited understanding of the specific receptors and signaling pathways involved in LPS-host cell interactions. Methodology/Principal Findings This study systematically investigated the effects of P. gingivalis LPS1435/1449 and LPS1690 on the expression of TLR2 and TLR4 signal transduction and the activation of pro-inflammatory cytokines IL-6 and IL-8 in human gingival fibroblasts (HGFs). We found that LPS1435/1449 and LPS1690 differentially modulated TLR2 and TLR4 expression. NF-κB pathway was significantly activated by LPS1690 but not by LPS1435/1449. In addition, LPS1690 induced significant expression of NF-κB and p38 MPAK pathways-related genes, such as NFKBIA, NFKB1, IKBKB, MAP2K4 and MAPK8. Notably, the pro-inflammatory genes including GM-CSF, CXCL10, G-CSF, IL-6, IL-8 and CCL2 were significantly upregulated by LPS1690 while down-regulated by LPS1435/1449. Blocking assays confirmed that TLR4-mediated NF-κB signaling was vital in LPS1690-induced expression of IL-6 and IL-8 in HGFs. Conclusions/Significance The present study suggests that the tetra- and penta-acylated lipid A structures of P. gingivalis LPS differentially activate TLR4-mediated NF-κB signaling pathway, and significantly modulate the expression of IL-6 and IL-8 in HGFs. The ability to alter the lipid A structure of LPS could be one of the strategies carried-out by P. gingivalis to evade innate host defense in gingival tissues, thereby contributing to periodontal pathogenesis.
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Affiliation(s)
- Thanuja D. K. Herath
- Faculty of Dentistry, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Richard P. Darveau
- School of Dentistry, University of Washington, Seattle, Washington, United States of America
| | - Chaminda J. Seneviratne
- Faculty of Dentistry, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Cun-Yu Wang
- School of Dentistry, University of California Los Angeles, Los Angeles, California, United States of America
| | - Yu Wang
- Department of Pharmacology & Pharmacy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Lijian Jin
- Faculty of Dentistry, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- * E-mail:
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Mariano FS, Campanelli AP, Nociti FH, Mattos-Graner RO, Gonçalves RB. Antimicrobial peptides and nitric oxide production by neutrophils from periodontitis subjects. Braz J Med Biol Res 2012; 45:1017-24. [PMID: 22850872 PMCID: PMC3854147 DOI: 10.1590/s0100-879x2012007500123] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 07/23/2012] [Indexed: 01/16/2023] Open
Abstract
Neutrophils play an important role in periodontitis by producing nitric oxide (NO) and antimicrobial peptides, molecules with microbicidal activity via oxygen-dependent and -independent mechanisms, respectively. It is unknown whether variation in the production of antimicrobial peptides such as LL-37, human neutrophil peptides (HNP) 1-3, and NO by neutrophils influences the pathogenesis of periodontal diseases. We compared the production of these peptides and NO by lipopolysaccharide (LPS)-stimulated neutrophils isolated from healthy subjects and from patients with periodontitis. Peripheral blood neutrophils were cultured with or without Aggregatibacter actinomycetemcomitans-LPS (Aa-LPS), Porphyromonas gingivalis-LPS (Pg-LPS) and Escherichia coli-LPS (Ec-LPS). qRT-PCR was used to determine quantities of HNP 1-3 and LL-37 mRNA in neutrophils. Amounts of HNP 1-3 and LL-37 proteins in the cell culture supernatants were also determined by ELISA. In addition, NO levels in neutrophil culture supernatants were quantitated by the Griess reaction. Neutrophils from periodontitis patients cultured with Aa-LPS, Pg-LPS and Ec-LPS expressed higher HNP 1-3 mRNA than neutrophils from healthy subjects. LL-37 mRNA expression was higher in neutrophils from patients stimulated with Aa-LPS. Neutrophils from periodontitis patients produced significantly higher LL-37 protein levels than neutrophils from healthy subjects when stimulated with Pg-LPS and Ec-LPS, but no difference was observed in HNP 1-3 production. Neutrophils from periodontitis patients cultured or not with Pg-LPS and Ec-LPS produced significantly lower NO levels than neutrophils from healthy subjects. The significant differences in the production of LL-37 and NO between neutrophils from healthy and periodontitis subjects indicate that production of these molecules might influence individual susceptibility to important periodontal pathogens.
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Affiliation(s)
- F S Mariano
- Departamento de Diagnóstico Oral, Área Microbiologia e Imunologia, Faculdade de Odontologia de Piracicaba, Universidade de Campinas, Piracicaba, SP, Brasil.
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Herath TDK, Wang Y, Seneviratne CJ, Lu Q, Darveau RP, Wang CY, Jin L. Porphyromonas gingivalis lipopolysaccharide lipid A heterogeneity differentially modulates the expression of IL-6 and IL-8 in human gingival fibroblasts. J Clin Periodontol 2011; 38:694-701. [DOI: 10.1111/j.1600-051x.2011.01741.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Chen YY, Peng B, Yang Q, Glew MD, Veith PD, Cross KJ, Goldie KN, Chen D, O'Brien-Simpson N, Dashper SG, Reynolds EC. The outer membrane protein LptO is essential for the O-deacylation of LPS and the co-ordinated secretion and attachment of A-LPS and CTD proteins in Porphyromonas gingivalis. Mol Microbiol 2011; 79:1380-401. [DOI: 10.1111/j.1365-2958.2010.07530.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Chang J, Jain S, Carl DJ, Paolella L, Darveau RP, Gravett MG, Adams Waldorf KM. Differential host response to LPS variants in amniochorion and the TLR4/MD-2 system in Macaca nemestrina. Placenta 2010; 31:811-7. [PMID: 20619890 DOI: 10.1016/j.placenta.2010.06.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 06/11/2010] [Accepted: 06/16/2010] [Indexed: 12/23/2022]
Abstract
OBJECTIVES Microbial-specific factors are likely critical in determining whether bacteria trigger preterm labor. Structural variations in lipopolysaccharide (LPS), a component of gram-negative bacteria, can determine whether LPS has an inflammatory (agonist) or anti-inflammatory (antagonist) effect through Toll-like receptor 4 (TLR4). Our objective was to determine whether amniochorion could discriminate between LPS variants in a nonhuman primate model. We also cloned Macaca nemestrina TLR4 and MD-2 and compared this complex functionally to the human homologue to establish whether nonhuman primates could be used to study TLR4 signaling in preterm birth. STUDY DESIGN Amniochorion explants from M. nemestrina were stimulated with a panel of LPS variants for 24 h. Supernatants were analyzed for IL-1beta, TNF-alpha, IL-6, IL-8 and prostaglandins E2 and F2alpha. Tissue expression of TLR1, 2, 4, 6, MyD88 and NF-kappaB was studied by RT-PCR. M. nemestrina TLR4 and MD-2 genes were cloned and compared with their human counterparts in a recombinant TLR4 signaling system to determine LPS sensitivity. RESULTS LPS variants differentially stimulated cytokines and prostaglandins, which was not related to transcriptional changes of TLR4 or other TLRs. Nearly all elements of LPS binding and TLR4 leucine-rich repeats were conserved between humans and M. nemestrina. TLR4/MD-2 signaling complexes from both species were equally sensitive to LPS variants. CONCLUSIONS LPS variants elicit a hierarchical inflammatory response within amniochorion that may contribute to preterm birth. LPS sensitivity is similar between M. nemestrina and humans, validating M. nemestrina as an appropriate model to study TLR4 signaling in preterm birth.
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Affiliation(s)
- J Chang
- Department of Obstetrics & Gynecology, Magee Women's Hospital, Pittsburgh, PA, USA
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Buduneli N, Larsson L, Biyikoglu B, Renaud DE, Bagaitkar J, Scott DA. Fatty acid profiles in smokers with chronic periodontitis. J Dent Res 2010; 90:47-52. [PMID: 21041552 DOI: 10.1177/0022034510380695] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We hypothesized that tobacco smoke induces alterations to the 3-OH fatty acids present in lipid A in a manner consistent with a microflora of reduced inflammatory potential. Whole saliva samples and full-mouth clinical periodontal recordings were obtained from persons with (22 smokers; 15 non-smokers) and without (14 smokers; 15 non-smokers) chronic periodontitis. Clear differences in the contributions of multiple saturated 3-OH fatty acid species were noted in the group with disease compared with healthy individuals. Increases in the long-chain fatty acids associated with anaerobic bacterial periodontopathogens, particularly 3-OH-C(i17.0) (146.7%, relative to controls), were apparent. Significant reductions in the 3-OH fatty acids associated with the consensus (high potency) enteric LPS structure (3-OH-C(12.0) and 3-OH-C(14.0); 33.3% and 15.8% reduction, respectively) were noted in smokers compared with non-smokers with chronic periodontitis. Thus, smoking is associated with specific structural alterations to the lipid-A-derived 3-OH fatty acid profile in saliva that are consistent with an oral microflora of reduced inflammatory potential. These findings provide much-needed mechanistic insight into the established clinical conundrum of increased infection with periodontal pathogens but reduced clinical inflammation in smokers.
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Affiliation(s)
- N Buduneli
- Department of Periodontology, School of Dentistry, Ege University, İzmir, Turkey
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The lipid A phosphate position determines differential host Toll-like receptor 4 responses to phylogenetically related symbiotic and pathogenic bacteria. Infect Immun 2010; 79:203-10. [PMID: 20974832 DOI: 10.1128/iai.00937-10] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The human symbiont Bacteroides thetaiotaomicron promotes intestinal function and health, whereas the phylogenetically related pathogen Porphyromonas gingivalis is associated with the chronic oral inflammatory disease periodontitis. Although both B. thetaiotaomicron and P. gingivalis synthesize lipopolysaccharides (LPS) consisting of penta-acylated, monophosphorylated lipid A in addition to immunologically silent, nonphosphorylated lipid A, they elicit strikingly distinct Toll-like receptor 4 (TLR4) responses. We show that the phosphate position of penta-acylated, monophosphorylated lipid A is a key feature for determining the differential TLR4 responses elicited by these evolutionarily related bacteria. B. thetaiotaomicron produces TLR4-stimulatory lipid A bearing a 1-phosphate, in contrast to P. gingivalis, which produces TLR4-evasive lipid A bearing a 4'-phosphate. Confirming these observations, recombinant Escherichia coli LPS containing penta-acylated, 1-phosphorylated lipid A is more TLR4 stimulatory than LPS containing 4'-phosphorylated lipid A. The specific capacity of a Gram-negative bacterium to alert or evade the host innate immune defense system through TLR4-dependent signaling is currently recognized as a critical aspect defining the relationship between the host and the bacterium. We propose that the distinct lipid A phosphate positions observed for the B. thetaiotaomicron and P. gingivalis LPS contributes to the manifestation of these bacteria as commensal or pathogen within the human host.
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The structurally similar, penta-acylated lipopolysaccharides of Porphyromonas gingivalis and Bacteroides elicit strikingly different innate immune responses. Microb Pathog 2009; 47:68-77. [PMID: 19460428 DOI: 10.1016/j.micpath.2009.04.015] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 02/12/2009] [Accepted: 04/27/2009] [Indexed: 11/21/2022]
Abstract
Lipid A structural modifications can substantially impact the host's inflammatory response to bacterial LPS. Bacteroides fragilis, an opportunistic pathogen associated with life-threatening sepsis and intra-abdominal abscess formation, and Bacteroides thetaiotaomicron, a symbiont pivotal for proper host intestinal tissue development, both produce an immunostimulatory LPS comprised of penta-acylated lipid A. Under defined conditions, Porphyromonas gingivalis, an oral pathogen associated with periodontitis, also produces an LPS bearing a penta-acylated lipid A. However, this LPS preparation is 100-1000 times less potent than Bacteroides LPS in stimulating endothelial cells. We analyzed Bacteroides and P. gingivalis lipid A structures using MALDI-TOF MS and gas chromatography to determine the structural basis for this phenomenon. Even though both Bacteroides and P. gingivalis lipid A molecules are penta-acylated and mono-phosphorylated, subtle differences in mass and fatty acid content could account for the observed difference in LPS potency. This fatty acid heterogeneity is also responsible for the peak "clusters" observed in the mass spectra and obfuscates the correlation between LPS structure and immunostimulatory ability. Further, we show the difference in potency between Bacteroides and P. gingivalis LPS is TLR4-dependent. Altogether, the data suggest subtle changes in lipid A structure may profoundly impact the host's innate immune response.
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Acyl chain specificity of the acyltransferases LpxA and LpxD and substrate availability contribute to lipid A fatty acid heterogeneity in Porphyromonas gingivalis. J Bacteriol 2008; 190:4549-58. [PMID: 18456814 DOI: 10.1128/jb.00234-08] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Porphyromonas gingivalis lipid A is heterogeneous with regard to the number, type, and placement of fatty acids. Analysis of lipid A by matrix-assisted laser desorption ionization-time of flight mass spectrometry reveals clusters of peaks differing by 14 mass units indicative of an altered distribution of the fatty acids generating different lipid A structures. To examine whether the transfer of hydroxy fatty acids with different chain lengths could account for the clustering of lipid A structures, P. gingivalis lpxA (lpxA(Pg)) and lpxD(Pg) were cloned and expressed in Escherichia coli strains in which the homologous gene was mutated. Lipid A from strains expressing either of the P. gingivalis transferases was found to contain 16-carbon hydroxy fatty acids in addition to the normal E. coli 14-carbon hydroxy fatty acids, demonstrating that these acyltransferases display a relaxed acyl chain length specificity. Both LpxA and LpxD, from either E. coli or P. gingivalis, were also able to incorporate odd-chain fatty acids into lipid A when grown in the presence of 1% propionic acid. This indicates that E. coli lipid A acyltransferases do not have an absolute specificity for 14-carbon hydroxy fatty acids but can transfer fatty acids differing by one carbon unit if the fatty acid substrates are available. We conclude that the relaxed specificity of the P. gingivalis lipid A acyltransferases and the substrate availability account for the lipid A structural clusters that differ by 14 mass units observed in P. gingivalis lipopolysaccharide preparations.
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Albiger B, Dahlberg S, Henriques-Normark B, Normark S. Role of the innate immune system in host defence against bacterial infections: focus on the Toll-like receptors. J Intern Med 2007; 261:511-28. [PMID: 17547708 DOI: 10.1111/j.1365-2796.2007.01821.x] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The innate immunity plays a critical role in host protection against pathogens and it relies amongst others on pattern recognition receptors such as the Toll-like receptors (TLRs) and the nucleotide-binding oligomerization domains proteins (NOD-like receptors, NLRs) to alert the immune system of the presence of invading bacteria. Since their recent discovery less than a decade ago, both TLRs and NLRs have been shown to be crucial in host protection against microbial infections but also in homeostasis of the colonizing microflora. They recognize specific microbial ligands and with the use of distinct adaptor molecules, they activate different signalling pathways that in turns trigger subsequent inflammatory and immune responses that allows a immediate response towards bacterial infections and the initiation of the long-lasting adaptive immunity. In this review, we will focus on the role of the TLRs against bacterial infections in humans in contrast to mice that have been used extensively in experimental models of infections and discuss their role in controlling normal flora or nonpathogenic bacteria. We also highlight how bacteria can evade recognition by TLRs.
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Affiliation(s)
- B Albiger
- Medical Microbiology, Department of Laboratory Medicine, Lund University, Malmö, Sweden
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