scholarly journals Tools of Aggregatibacter actinomycetemcomitans to Evade the Host Response

2019 ◽  
Vol 8 (7) ◽  
pp. 1079 ◽  
Author(s):  
Jan Oscarsson ◽  
Rolf Claesson ◽  
Mark Lindholm ◽  
Carola Höglund Åberg ◽  
Anders Johansson
Keyword(s):  
Host Response ◽  
Molecular Mechanisms ◽  
Inflammatory Responses ◽  
Treatment Resistance ◽  
Membrane Vesicles ◽  
Aggregatibacter Actinomycetemcomitans ◽  
Outer Membrane Vesicles ◽  
Oral Microbiome ◽  
Connective Tissues ◽  
Ecological Changes

Periodontitis is an infection-induced inflammatory disease that affects the tooth supporting tissues, i.e., bone and connective tissues. The initiation and progression of this disease depend on dysbiotic ecological changes in the oral microbiome, thereby affecting the severity of disease through multiple immune-inflammatory responses. Aggregatibacter actinomycetemcomitans is a facultative anaerobic Gram-negative bacterium associated with such cellular and molecular mechanisms associated with the pathogenesis of periodontitis. In the present review, we outline virulence mechanisms that help the bacterium to escape the host response. These properties include invasiveness, secretion of exotoxins, serum resistance, and release of outer membrane vesicles. Virulence properties of A. actinomycetemcomitans that can contribute to treatment resistance in the infected individuals and upon translocation to the circulation, also induce pathogenic mechanisms associated with several systemic diseases.

scholarly journals Aggregatibacter actinomycetemcomitans Outer Membrane Vesicles Are Internalized in Human Host Cells and Trigger NOD1- and NOD2-Dependent NF-κB Activation

2014 ◽  
Vol 82 (10) ◽  
pp. 4034-4046 ◽  
Author(s):  
Bernard Thay ◽  
Anna Damm ◽  
Thomas A. Kufer ◽  
Sun Nyunt Wai ◽  
Jan Oscarsson
Keyword(s):  
Outer Membrane ◽  
Hela Cells ◽  
Inflammatory Responses ◽  
Membrane Vesicles ◽  
Aggregatibacter Actinomycetemcomitans ◽  
Outer Membrane Vesicles ◽  
Biologically Active ◽  
Host Cells ◽  
Content Type ◽  
Human Embryonic Kidney Cells

ABSTRACTAggregatibacter actinomycetemcomitansis an oral and systemic pathogen associated with aggressive forms of periodontitis and with endocarditis. We recently demonstrated that outer membrane vesicles (OMVs) disseminated byA. actinomycetemcomitanscould deliver multiple proteins, including biologically active cytolethal distending toxin (CDT), into the cytosol of HeLa cells and human gingival fibroblasts (HGF). In the present work, we have used immunoelectron and confocal microscopy analysis and fluorescently labeled vesicles to further investigate mechanisms forA. actinomycetemcomitansOMV-mediated delivery of bacterial antigens to these host cells. Our results supported that OMVs were internalized into the perinuclear region of HeLa cells and HGF. Colocalization analysis revealed that internalized OMVs colocalized with the endoplasmic reticulum and carried antigens, detected using an antibody specific to wholeA. actinomycetemcomitansserotype a cells. Consistent with OMV internalization mediating intracellular antigen exposure, the vesicles acted as strong inducers of cytoplasmic peptidoglycan sensor NOD1- and NOD2-dependent NF-κB activation in human embryonic kidney cells. Moreover, NOD1 was the main sensor of OMV-delivered peptidoglycan in myeloid THP1 cells, contributing to the overall inflammatory responses induced by the vesicles. This work reveals a role ofA. actinomycetemcomitansOMVs as a trigger of innate immunity via carriage of NOD1- and NOD2-active pathogen-associated molecular patterns (PAMPs).

scholarly journals Bacterial Membrane Vesicles in Pneumonia: From Mediators of Virulence to Innovative Vaccine Candidates

2021 ◽  
Vol 22 (8) ◽  
pp. 3858
Author(s):  
Felix Behrens ◽  
Teresa C. Funk-Hilsdorf ◽  
Wolfgang M. Kuebler ◽  
Szandor Simmons
Keyword(s):  
Extracellular Vesicles ◽  
Inflammatory Responses ◽  
Significant Proportion ◽  
Treatment Strategies ◽  
Membrane Vesicles ◽  
Multidrug Resistant ◽  
Biochemical Properties ◽  
Outer Membrane Vesicles ◽  
Vaccine Candidates ◽  
Treatment Regimens

Pneumonia due to respiratory infection with most prominently bacteria, but also viruses, fungi, or parasites is the leading cause of death worldwide among all infectious disease in both adults and infants. The introduction of modern antibiotic treatment regimens and vaccine strategies has helped to lower the burden of bacterial pneumonia, yet due to the unavailability or refusal of vaccines and antimicrobials in parts of the global population, the rise of multidrug resistant pathogens, and high fatality rates even in patients treated with appropriate antibiotics pneumonia remains a global threat. As such, a better understanding of pathogen virulence on the one, and the development of innovative vaccine strategies on the other hand are once again in dire need in the perennial fight of men against microbes. Recent data show that the secretome of bacteria consists not only of soluble mediators of virulence but also to a significant proportion of extracellular vesicles—lipid bilayer-delimited particles that form integral mediators of intercellular communication. Extracellular vesicles are released from cells of all kinds of organisms, including both Gram-negative and Gram-positive bacteria in which case they are commonly termed outer membrane vesicles (OMVs) and membrane vesicles (MVs), respectively. (O)MVs can trigger inflammatory responses to specific pathogens including S. pneumonia, P. aeruginosa, and L. pneumophila and as such, mediate bacterial virulence in pneumonia by challenging the host respiratory epithelium and cellular and humoral immunity. In parallel, however, (O)MVs have recently emerged as auspicious vaccine candidates due to their natural antigenicity and favorable biochemical properties. First studies highlight the efficacy of such vaccines in animal models exposed to (O)MVs from B. pertussis, S. pneumoniae, A. baumannii, and K. pneumoniae. An advanced and balanced recognition of both the detrimental effects of (O)MVs and their immunogenic potential could pave the way to novel treatment strategies in pneumonia and effective preventive approaches.

scholarly journals Aggregatibacter actinomycetemcomitans Leukotoxin Is Delivered to Host Cells in an LFA-1-Indepdendent Manner When Associated with Outer Membrane Vesicles

Toxins ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 414 ◽  
Author(s):  
Justin Nice ◽  
Nataliya Balashova ◽  
Scott Kachlany ◽  
Evan Koufos ◽  
Eric Krueger ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Membrane Vesicles ◽  
Aggregatibacter Actinomycetemcomitans ◽  
Aggressive Periodontitis ◽  
Outer Membrane Vesicles ◽  
Host Cells ◽  
Type I ◽  
Outer Membranes ◽  
Independent Mechanism ◽  
Bacterial Outer Membrane

The Gram-negative bacterium, Aggregatibacter actinomycetemcomitans, has been associated with localized aggressive periodontitis (LAP). In particular, highly leukotoxic strains of A. actinomycetemcomitans have been more closely associated with this disease, suggesting that LtxA is a key virulence factor for A. actinomycetemcomitans. LtxA is secreted across both the inner and outer membranes via the Type I secretion system, but has also been found to be enriched within outer membrane vesicles (OMVs), derived from the bacterial outer membrane. We have characterized the association of LtxA with OMVs produced by the highly leukotoxic strain, JP2, and investigated the interaction of these OMVs with host cells to understand how LtxA is delivered to host cells in this OMV-associated form. Our results demonstrated that a significant fraction of the secreted LtxA exists in an OMV-associated form. Furthermore, we have discovered that in this OMV-associated form, the toxin is trafficked to host cells by a cholesterol- and receptor-independent mechanism in contrast to the mechanism by which free LtxA is delivered. Because OMV-associated toxin is trafficked to host cells in an entirely different manner than free toxin, this study highlights the importance of studying both free and OMV-associated forms of LtxA to understand A. actinomycetemcomitans virulence.

scholarly journals Physicochemical Evidence that Francisella FupA and FupB Proteins Are Porins

2020 ◽  
Vol 21 (15) ◽  
pp. 5496
Author(s):  
Claire Siebert ◽  
Corinne Mercier ◽  
Donald K. Martin ◽  
Patricia Renesto ◽  
Beatrice Schaack
Keyword(s):  
Outer Membrane ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Iron Transport ◽  
Molecular Mechanisms ◽  
Protein A ◽  
Membrane Vesicles ◽  
Disodium Salt ◽  
Outer Membrane Vesicles ◽  
Novel Therapeutic Strategies

Responsible for tularemia, Francisella tularensis bacteria are highly infectious Gram-negative, category A bioterrorism agents. The molecular mechanisms for their virulence and resistance to antibiotics remain largely unknown. FupA (Fer Utilization Protein), a protein mediating high-affinity transport of ferrous iron across the outer membrane, is associated with both. Recent studies demonstrated that fupA deletion contributed to lower F. tularensis susceptibility towards fluoroquinolones, by increasing the production of outer membrane vesicles. Although the paralogous FupB protein lacks such activity, iron transport capacity and a role in membrane stability were reported for the FupA/B chimera, a protein found in some F. tularensis strains, including the live vaccine strain (LVS). To investigate the mode of action of these proteins, we purified recombinant FupA, FupB and FupA/B proteins expressed in Escherichia coli and incorporated them into mixed lipid bilayers. We examined the porin-forming activity of the FupA/B proteoliposomes using a fluorescent 8-aminonaphthalene-1,3,6-trisulfonic acid, disodium salt (ANTS) probe. Using electrophysiology on tethered bilayer lipid membranes, we confirmed that the FupA/B fusion protein exhibits pore-forming activity with large ionic conductance, a property shared with both FupA and FupB. This demonstration opens up new avenues for identifying functional genes, and novel therapeutic strategies against F. tularensis infections.

scholarly journals Proteomics of Aggregatibacter actinomycetemcomitans Outer Membrane Vesicles

PLoS ONE ◽  
2015 ◽  
Vol 10 (9) ◽  
pp. e0138591 ◽  
Author(s):  
Thomas Kieselbach ◽  
Vincent Zijnge ◽  
Elisabeth Granström ◽  
Jan Oscarsson
Keyword(s):  
Outer Membrane ◽  
Membrane Vesicles ◽  
Aggregatibacter Actinomycetemcomitans ◽  
Outer Membrane Vesicles

Heterologous Expression of 3-O-Deacylase in Acinetobacter baumannii Modulates the Endotoxicity of Lipopolysaccharide

2015 ◽  
Vol 25 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Farzad Badmasti ◽  
Fereshteh Shahcheraghi ◽  
Seyed Davar Siadat ◽  
Saeid Bouzari ◽  
Soheila Ajdary ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Lipid A ◽  
Recombinant Dna ◽  
Inflammatory Responses ◽  
Acyl Chain ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Negative Ion ◽  
Recombinant Dna Technology ◽  
Whole Cells

The lipopolysaccharide (LPS) of <i>Acinetobacter baumannii</i> is a potent stimulator of proinflammatory cytokines, such as interleukin-6 (IL-6). The 3-O-deacylase (PagL)-modifying enzyme that removes the 3-O-linked acyl chain from the disaccharide backbone of lipid A provides the opportunity to develop a new therapeutic compound that could reduce detrimental inflammatory responses. The plasmid pMMB66EH-PagL obtained by recombinant DNA technology was electroporated into <i>A. baumannii</i> ATCC 19606. Compared with wild-type LPS, outer membrane vesicles and inactivated whole cells of engineered bacteria had a statistically significant decreased ability to produce IL-6. Structural analysis of lipid A by negative-ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry revealed that the profile of lipid A fractions under PagL expression was changed. Taken together, our data showed that recombinant penta-acylated lipid A had less immunoreactivity and that the tetra-acylated version of lipid A with TLR4 antagonist activity decreased the induction of IL-6 production in the murine macrophage cell line J774 A.1.

scholarly journals LPS Remodeling Triggers Formation of Outer Membrane Vesicles inSalmonella

mBio ◽  
2016 ◽  
Vol 7 (4) ◽  
Author(s):  
Wael Elhenawy ◽  
Michael Bording-Jorgensen ◽  
Ezequiel Valguarnera ◽  
M. Florencia Haurat ◽  
Eytan Wine ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Molecular Mechanisms ◽  
Lipid A ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Mass Spectrometry Analysis ◽  
Membrane Remodeling ◽  
Macrophage Infection ◽  
Spectrometry Analysis

ABSTRACTOuter membrane vesicles (OMV) are proposed to mediate multiple functions during pathogenesis and symbiosis. However, the mechanisms responsible for OMV formation remain poorly understood. It has been shown in eukaryotic membranes that lipids with an inverted-cone shape favor the formation of positive membrane curvatures. Based on these studies, we formulated the hypothesis that lipid A deacylation might impose shape modifications that result in the curvature of the outer membrane (OM) and subsequent OMV formation. We tested the effect of lipid A remodeling on OMV biogenesis employingSalmonella entericaserovar Typhimurium as a model organism. Expression of the lipid A deacylase PagL resulted in increased vesiculation, without inducing an envelope stress response. Mass spectrometry analysis revealed profound differences in the patterns of lipid A in OM and OMV, with accumulation of deacylated lipid A forms exclusively in OMV. OMV biogenesis by intracellular bacteria upon macrophage infection was drastically reduced in apagLmutant strain. We propose a novel mechanism for OMV biogenesis requiring lipid A deacylation in the context of a multifactorial process that involves the orchestrated remodeling of the outer membrane.IMPORTANCEThe role of lipid remodeling in vesiculation is well documented in eukaryotes. Similarly, bacteria produce membrane-derived vesicles; however, the molecular mechanisms underlying their production are yet to be determined. In this work, we investigated the role of outer membrane remodeling in OMV biogenesis inS. Typhimurium. We showed that the expression of the lipid A deacylase PagL results in overvesiculation with deacylated lipid A accumulation exclusively in OMV. AnS. Typhimurium ΔpagLstrain showed a significant reduction in intracellular OMV secretion relative to the wild-type strain. Our results suggest a novel mechanism for OMV biogenesis that involves outer membrane remodeling through lipid A modification. Understanding how OMV are produced by bacteria is important to advance our understanding of the host-pathogen interactions.

scholarly journals Perinuclear Localization of Internalized Outer Membrane Vesicles Carrying Active Cytolethal Distending Toxin from Aggregatibacter actinomycetemcomitans

2011 ◽  
Vol 80 (1) ◽  
pp. 31-42 ◽  
Author(s):  
Pramod Kumar Rompikuntal ◽  
Bernard Thay ◽  
Muhammad Khanzeb Khan ◽  
Jonna Alanko ◽  
Anna-Maija Penttinen ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Membrane Vesicles ◽  
Cell Types ◽  
Aggregatibacter Actinomycetemcomitans ◽  
Outer Membrane Vesicles ◽  
Biologically Active ◽  
Cytolethal Distending Toxin ◽  
Content Type ◽  
Serotype A ◽  
Tight Association

ABSTRACTAggregatibacter actinomycetemcomitansis implicated in aggressive forms of periodontitis. Similarly to several other Gram-negative species, this organism produces and excretes a cytolethal distending toxin (CDT), a genotoxin associated with cell distention, G2cell cycle arrest, and/or apoptosis in many mammalian cell types. In this study, we have identifiedA. actinomycetemcomitansouter membrane vesicles (OMVs) as a vehicle for simultaneous delivery of multiple proteins, including CDT, into human cells. The OMV proteins were internalized in both HeLa cells and human gingival fibroblasts (HGF) via a mechanism of OMV fusion with lipid rafts in the plasma membrane. The active toxin unit, CdtB, was localized inside the nucleus of the intoxicated cells, whereas OmpA and proteins detected using an antibody specific to wholeA. actinomycetemcomitansserotype a cells had a perinuclear distribution. In accordance with a tight association of CdtB with OMVs, vesicles isolated fromA. actinomycetemcomitansstrain D7SS (serotype a), in contrast to OMVs from a D7SScdtABCmutant, induced a cytolethal distending effect on HeLa and HGF cells, indicating that OMV-associated CDT was biologically active. Association of CDT with OMVs was also observed inA. actinomycetemcomitansisolates belonging to serotypes b and c, indicating that OMV-mediated release of CDT may be conserved inA. actinomycetemcomitans. Although the role ofA. actinomycetemcomitansOMVs in periodontal disease has not yet been elucidated, our present data suggest that OMVs could deliver biologically active CDT and additional virulence factors into susceptible cells of the periodontium.

Sign in / Sign up

Export Citation Format

Share Document