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Krueger E, Brown AC. Aggregatibacter actinomycetemcomitans leukotoxin: From mechanism to targeted anti-toxin therapeutics. Mol Oral Microbiol 2020; 35:85-105. [PMID: 32061022 DOI: 10.1111/omi.12284] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 02/12/2020] [Accepted: 02/13/2020] [Indexed: 12/13/2022]
Abstract
Aggregatibacter actinomycetemcomitans is a Gram-negative bacterium associated with localized aggressive periodontitis, as well as other systemic diseases. This organism produces a number of virulence factors, all of which provide some advantage to the bacterium. Several studies have demonstrated that clinical isolates from diseased patients, particularly those of African descent, frequently belong to specific clones of A. actinomycetemcomitans that produce significantly higher amounts of a protein exotoxin belonging to the repeats-in-toxin (RTX) family, leukotoxin (LtxA), whereas isolates from healthy patients harbor minimally leukotoxic strains. This finding suggests that LtxA might play a key role in A. actinomycetemcomitans pathogenicity. Because of this correlation, much work over the past 30 years has been focused on understanding the mechanisms by which LtxA interacts with and kills host cells. In this article, we review those findings, highlight the remaining open questions, and demonstrate how knowledge of these mechanisms, particularly the toxin's interactions with lymphocyte function-associated antigen-1 (LFA-1) and cholesterol, enables the design of targeted anti-LtxA strategies to prevent/treat disease.
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Affiliation(s)
- Eric Krueger
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, USA
| | - Angela C Brown
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, USA
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2
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Cranberry Proanthocyanidins Neutralize the Effects of Aggregatibacter actinomycetemcomitans Leukotoxin. Toxins (Basel) 2019; 11:toxins11110662. [PMID: 31739483 PMCID: PMC6891731 DOI: 10.3390/toxins11110662] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 11/07/2019] [Accepted: 11/08/2019] [Indexed: 01/14/2023] Open
Abstract
Aggregatibacter actinomycetemcomitans is a Gram-negative bacterium that has been strongly associated with localized aggressive periodontitis. The capacity of A. actinomycetemcomitans to produce a leukotoxin (LtxA) that activates pyroptosis in macrophages and induces the release of endogenous danger signals is thought to play a key role in the disease process. The aim of the present study was to investigate the effects of cranberry proanthocyanidins (PACs) on gene expression and cytotoxic activities of LtxA. We showed that cranberry PACs dose-dependently attenuate the expression of genes making up the leukotoxin operon, including ltxB and ltxC, in the two strains of A. actinomycetemcomitans tested. Cranberry PACs (≥62.5 µg/mL) protected macrophages against the cytotoxic effect of purified LtxA. Moreover, cranberry PACs reduced caspase-1 activation in LtxA-treated macrophages and consequently decreased the release of both IL-1β and IL-18, which are known as damage-associated molecular patterns (DAMPs) and contribute to the progression of periodontitis by increasing cell migration and osteoclastogenesis. In addition, cranberry PACs reduced the expression of genes encoding the P2X7 receptor and NALP3 (NACHT, LRR and PYD domains-containing protein 3), which play key roles in pore formation and cell death. Lastly, cranberry PACs blocked the binding of LtxA to macrophages and consequently reduced the LtxA-mediated cytotoxicity. In summary, the present study showed that cranberry PACs reduced LtxA gene expression in A. actinomycetemcomitans and neutralized the cytolytic and pro-inflammatory responses of human macrophages treated with LtxA. Given these properties, cranberry PACs may represent promising molecules for prevention and treatment of the aggressive form of periodontitis caused by A. actinomycetemcomitans.
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Vega BA, Belinka BA, Kachlany SC. Aggregatibacter actinomycetemcomitans Leukotoxin (LtxA; Leukothera ®): Mechanisms of Action and Therapeutic Applications. Toxins (Basel) 2019; 11:toxins11090489. [PMID: 31454891 PMCID: PMC6784247 DOI: 10.3390/toxins11090489] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 08/21/2019] [Accepted: 08/22/2019] [Indexed: 12/18/2022] Open
Abstract
Aggregatibacter actinomycetemcomitans is an oral pathogen that produces the RTX toxin, leukotoxin (LtxA; Leukothera®). A. actinomycetemcomitans is strongly associated with the development of localized aggressive periodontitis. LtxA acts as a virulence factor for A. actinomycetemcomitans to subvert the host immune response by binding to the β2 integrin lymphocyte function-associated antigen-1 (LFA-1; CD11a/CD18) on white blood cells (WBCs), causing cell death. In this paper, we reviewed the state of knowledge on LtxA interaction with WBCs and the subsequent mechanisms of induced cell death. Finally, we touched on the potential therapeutic applications of LtxA (trade name Leukothera®) toxin therapy for the treatment of hematological malignancies and immune-mediated diseases.
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Affiliation(s)
- Brian A Vega
- Department of Oral Biology, Rutgers School of Dental Medicine, Newark, NJ 07103, USA
- Actinobac Biomed, Inc., Princeton, NJ 08540, USA
| | | | - Scott C Kachlany
- Department of Oral Biology, Rutgers School of Dental Medicine, Newark, NJ 07103, USA.
- Actinobac Biomed, Inc., Princeton, NJ 08540, USA.
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Ha JH, Hauk P, Cho K, Eo Y, Ma X, Stephens K, Cha S, Jeong M, Suh JY, Sintim HO, Bentley WE, Ryu KS. Evidence of link between quorum sensing and sugar metabolism in Escherichia coli revealed via cocrystal structures of LsrK and HPr. SCIENCE ADVANCES 2018; 4:eaar7063. [PMID: 29868643 PMCID: PMC5983913 DOI: 10.1126/sciadv.aar7063] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Accepted: 04/18/2018] [Indexed: 05/30/2023]
Abstract
Quorum sensing (QS), a bacterial process that regulates population-scale behavior, is mediated by small signaling molecules, called autoinducers (AIs), that are secreted and perceived, modulating a "collective" phenotype. Because the autoinducer AI-2 is secreted by a wide variety of bacterial species, its "perception" cues bacterial behavior. This response is mediated by the lsr (LuxS-regulated) operon that includes the AI-2 transporter LsrACDB and the kinase LsrK. We report that HPr, a phosphocarrier protein central to the sugar phosphotransferase system of Escherichia coli, copurifies with LsrK. Cocrystal structures of an LsrK/HPr complex were determined, and the effects of HPr and phosphorylated HPr on LsrK activity were assessed. LsrK activity is inhibited when bound to HPr, revealing new linkages between QS activity and sugar metabolism. These findings help shed new light on the abilities of bacteria to rapidly respond to changing nutrient levels at the population scale. They also suggest new means of manipulating QS activity among bacteria and within various niches.
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Affiliation(s)
- Jung-Hye Ha
- Protein Structure Research Group, Korea Basic Science Institute, 162 Yeongudanji-ro, Ochang-eup, Cheongju-si, Chungcheongbuk-do 28119, South Korea
- Department of Bio-Analytical Science, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, South Korea
- New Drug Development Center, 80 Cheombok-ro, Dong-gu, Daegu-si 41061, South Korea
| | - Pricila Hauk
- Institute for Bioscience and Biotechnology Research, University of Maryland, College Park, MD 20742, USA
- Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742, USA
| | - Kun Cho
- Biomedical Omics Group, Korea Basic Science Institute, Chungcheongbuk-do 28119, South Korea
| | - Yumi Eo
- Protein Structure Research Group, Korea Basic Science Institute, 162 Yeongudanji-ro, Ochang-eup, Cheongju-si, Chungcheongbuk-do 28119, South Korea
| | - Xiaochu Ma
- Department of Chemistry and Institute for Drug Discovery, Purdue University, West Lafayette, IN 47907, USA
| | - Kristina Stephens
- Institute for Bioscience and Biotechnology Research, University of Maryland, College Park, MD 20742, USA
- Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742, USA
| | - Soyoung Cha
- Protein Structure Research Group, Korea Basic Science Institute, 162 Yeongudanji-ro, Ochang-eup, Cheongju-si, Chungcheongbuk-do 28119, South Korea
| | - Migyeong Jeong
- Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, South Korea
| | - Jeong-Yong Suh
- Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, South Korea
| | - Herman O. Sintim
- Department of Chemistry and Institute for Drug Discovery, Purdue University, West Lafayette, IN 47907, USA
| | - William E. Bentley
- Institute for Bioscience and Biotechnology Research, University of Maryland, College Park, MD 20742, USA
- Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742, USA
| | - Kyoung-Seok Ryu
- Protein Structure Research Group, Korea Basic Science Institute, 162 Yeongudanji-ro, Ochang-eup, Cheongju-si, Chungcheongbuk-do 28119, South Korea
- Department of Bio-Analytical Science, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, South Korea
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Ding Q, Tan KS. Himar1 Transposon for Efficient Random Mutagenesis in Aggregatibacter actinomycetemcomitans. Front Microbiol 2017; 8:1842. [PMID: 29018421 PMCID: PMC5622930 DOI: 10.3389/fmicb.2017.01842] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 09/08/2017] [Indexed: 12/14/2022] Open
Abstract
Aggregatibacter actinomycetemcomitans is the primary etiological agent of aggressive periodontal disease. Identification of novel virulence factors at the genome-wide level is hindered by lack of efficient genetic tools to perform mutagenesis in this organism. The Himar1 mariner transposon is known to yield a random distribution of insertions in an organism’s genome with requirement for only a TA dinucleotide target and is independent of host-specific factors. However, the utility of this system in A. actinomycetemcomitans is unknown. In this study, we found that Himar1 transposon mutagenesis occurs at a high frequency (×10-4), and can be universally applied to wild-type A. actinomycetemcomitans strains of serotypes a, b, and c. The Himar1 transposon inserts were stably inherited in A. actinomycetemcomitans transconjugants in the absence of antibiotics. A library of 16,000 mutant colonies of A. actinomycetemcomitans was screened for reduced biofilm formation. Mutants with transposon inserts in genes encoding pilus, putative ion transporters, multidrug resistant proteins, transcription regulators and enzymes involved in the synthesis of extracellular polymeric substance, bacterial metabolism and stress response were discovered in this screen. Our results demonstrated the utility of the Himar1 mutagenesis system as a novel genetic tool for functional genomic analysis in A. actinomycetemcomitans.
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Affiliation(s)
- Qinfeng Ding
- Faculty of Dentistry, National University of Singapore, Singapore, Singapore
| | - Kai Soo Tan
- Faculty of Dentistry, National University of Singapore, Singapore, Singapore
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Derkaoui M, Antunes A, Poncet S, Nait Abdallah J, Joyet P, Mazé A, Henry C, Taha MK, Deutscher J, Deghmane AE. The phosphocarrier protein HPr of Neisseria meningitidis interacts with the transcription regulator CrgA and its deletion affects capsule production, cell adhesion, and virulence. Mol Microbiol 2016; 100:788-807. [PMID: 26858137 DOI: 10.1111/mmi.13349] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/04/2016] [Indexed: 01/08/2023]
Abstract
The bacterial phosphotransferase system (PTS) transports and phosphorylates sugars, but also carries out numerous regulatory functions. The β-proteobacterium Neisseria meningitidis possesses an incomplete PTS unable to transport carbon sources because it lacks a membrane component. Nevertheless, the residual phosphorylation cascade is functional and the meningococcal PTS was therefore expected to carry out regulatory roles. Interestingly, a ΔptsH mutant (lacks the PTS protein HPr) exhibited reduced virulence in mice and after intraperitoneal challenge it was rapidly cleared from the bloodstream of BALB/c mice. The rapid clearance correlates with lower capsular polysaccharide production by the ΔptsH mutant, which is probably also responsible for its increased adhesion to Hec-1-B epithelial cells. In addition, compared to the wild-type strain more apoptotic cells were detected when Hec-1-B cells were infected with the ΔptsH strain. Coimmunoprecipitation revealed an interaction of HPr and P-Ser-HPr with the LysR type transcription regulator CrgA, which among others controls its own expression. Moreover, ptsH deletion caused increased expression of a ΦcrgA-lacZ fusion. Finally, the presence of HPr or phospho-HPr's during electrophoretic mobility shift assays enhanced the affinity of CrgA for its target sites preceding crgA and pilE, but HPr did not promote CrgA binding to the sia and pilC1 promoter regions.
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Affiliation(s)
- Meriem Derkaoui
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France.,Institut Pasteur, Unité des Infections Bactériennes Invasives, 75000, Paris Cedex, France
| | - Ana Antunes
- Institut Pasteur, Unité des Infections Bactériennes Invasives, 75000, Paris Cedex, France
| | - Sandrine Poncet
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France
| | - Jamila Nait Abdallah
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France.,Institut Pasteur, Unité des Infections Bactériennes Invasives, 75000, Paris Cedex, France
| | - Philippe Joyet
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France
| | - Alain Mazé
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France
| | - Céline Henry
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France
| | - Muhamed-Kheir Taha
- Institut Pasteur, Unité des Infections Bactériennes Invasives, 75000, Paris Cedex, France
| | - Josef Deutscher
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France.,Centre National de la Recherche Scientifique, UMR8261, Expression Génétique Microbienne, Institut de Biologie Physico-Chimique, 75005, Paris, France
| | - Ala-Eddine Deghmane
- Institut Pasteur, Unité des Infections Bactériennes Invasives, 75000, Paris Cedex, France
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Transcriptome Profiling of Wild-Type and pga-Knockout Mutant Strains Reveal the Role of Exopolysaccharide in Aggregatibacter actinomycetemcomitans. PLoS One 2015. [PMID: 26221956 PMCID: PMC4519337 DOI: 10.1371/journal.pone.0134285] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Exopolysaccharides have a diverse set of functions in most bacteria including a mechanistic role in protecting bacteria against environmental stresses. Among the many functions attributed to the exopolysaccharides, biofilm formation, antibiotic resistance, immune evasion and colonization have been studied most extensively. The exopolysaccharide produced by many Gram positive as well as Gram negative bacteria including the oral pathogen Aggregatibacter actinomycetemcomitans is the homopolymer of β(1,6)-linked N-acetylglucosamine. Recently, we reported that the PGA-deficient mutant of A. actinomycetemcomitans failed to colonize or induce bone resorption in a rat model of periodontal disease, and the colonization genes, apiA and aae, were significantly down regulated in the mutant strain. To understand the role of exopolysaccharide and the pga locus in the global expression of A. actinomycetemcomitans, we have used comparative transcriptome profiling to identify differentially expressed genes in the wild-type strain in relation to the PGA-deficient strain. Transcriptome analysis revealed that about 50% of the genes are differently expressed (P < 0.05 and fold change >1.5). Our study demonstrated that the absence of the pga locus affects the genes involved in peptidoglycan recycling, glycogen storage, and virulence. Further, using confocal microscopy and plating assays, we show that the viability of pga mutant strain is significantly reduced during biofilm growth. Thus, this study highlights the importance of pga genes and the exopolysaccharide in the virulence of A. actinomycetemcomitans.
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Abstract
Oral colonising bacteria are highly adapted to the various environmental niches harboured within the mouth, whether that means while contributing to one of the major oral diseases of caries, pulp infections, or gingival/periodontal disease or as part of a commensal lifestyle. Key to these infections is the ability to adhere to surfaces via a range of specialised adhesins targeted at both salivary and epithelial proteins, their glycans and to form biofilm. They must also resist the various physical stressors they are subjected to, including pH and oxidative stress. Possibly most strikingly, they have developed the ability to harvest both nutrient sources provided by the diet and those derived from the host, such as protein and surface glycans. We have attempted to review recent developments that have revealed much about the molecular mechanisms at work in shaping the physiology of oral bacteria and how we might use this information to design and implement new treatment strategies.
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Cheng YA, Jee J, Hsu G, Huang Y, Chen C, Lin CP. A markerless protocol for genetic analysis of Aggregatibacter actinomycetemcomitans. J Formos Med Assoc 2014; 113:114-23. [PMID: 24530245 DOI: 10.1016/j.jfma.2012.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 05/09/2012] [Accepted: 05/15/2012] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND/PURPOSE The genomes of different Aggregatibacter actinomycetemcomitans (A actinomycetemcomitans) strains contain many strain-specific genes and genomic islands (defined as DNA found in some but not all strains) of unknown functions. Genetic analysis for the functions of these islands will be constrained by the limited availability of genetic markers and vectors for A actinomycetemcomitans. In this study, we tested a novel genetic approach of gene deletion and restoration in a naturally competent A actinomycetemcomitans strain D7S-1. METHODS Specific genes' deletion mutants and mutants restored with the deleted genes were constructed by a markerless loxP/Cre system. In mutants with sequential deletion of multiple genes loxP with different spacer regions were used to avoid unwanted recombinations between loxP sites. RESULTS Eight single-gene deletion mutants, four multiple-gene deletion mutants, and two mutants with restored genes were constructed. No unintended non-specific deletion mutants were generated by this protocol. The protocol did not negatively affect the growth and biofilm formation of A actinomycetemcomitans. CONCLUSION The protocol described in this study is efficient and specific for genetic manipulation of A actinomycetemcomitans, and will be amenable for functional analysis of multiple genes in A actinomycetemcomitans.
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Affiliation(s)
- Ya-An Cheng
- School of Dentistry and Graduate Institute of Clinical Dentistry, National Taiwan University, Taipei, Taiwan
| | - Jason Jee
- Division of Periodontology, Diagnostic Sciences and Dental Hygiene, Herman Ostrow School of Dentistry of the University of Southern California, Los Angeles, CA, USA
| | - Genie Hsu
- Division of Periodontology, Diagnostic Sciences and Dental Hygiene, Herman Ostrow School of Dentistry of the University of Southern California, Los Angeles, CA, USA
| | - Yanyan Huang
- Division of Periodontology, Diagnostic Sciences and Dental Hygiene, Herman Ostrow School of Dentistry of the University of Southern California, Los Angeles, CA, USA
| | - Casey Chen
- Division of Periodontology, Diagnostic Sciences and Dental Hygiene, Herman Ostrow School of Dentistry of the University of Southern California, Los Angeles, CA, USA
| | - Chun-Pin Lin
- School of Dentistry and Graduate Institute of Clinical Dentistry, National Taiwan University, Taipei, Taiwan.
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Nissen L, Sgorbati B, Biavati B, Belibasakis GN. Lactobacillus salivarius and L. gasseri down-regulate Aggregatibacter actinomycetemcomitans exotoxins expression. ANN MICROBIOL 2013; 64:611-617. [PMID: 24860281 PMCID: PMC4028514 DOI: 10.1007/s13213-013-0694-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 07/11/2013] [Indexed: 12/17/2022] Open
Abstract
Beneficial microbes, such as lactobacilli establish a symbiosis with the host and confer health-associated effects, by limiting the growth of indigenous pathogens and challenging microbes introduced by altered foods. Nevertheless, there is scarce information on the effects of beneficial microbes on the virulence properties of bacterial species associated with oral diseases, such as periodontitis. Aggregatibacter actinomycetemcomitans is a Gram-negative species highly implicated in the etiology of localized aggressive periodontitis. The objective of this study was to investigate the effect of lactobacilli on the expression of the two major virulence factors of A. actinomycetemcomitans. Lactobacillus salivarius and L. gasseri were selected as beneficial species. The gene expressions of leukotoxin (LtxA) and cytolethal distending toxin (CdtB) by A. actinomycetemcomitans were analyzed in response to challenge by lactobacilli cell-free supernatants. Neither lactobacilli affected the growth, but strongly attenuated the expressions of both CdtB and LtxA in the two A. actinomycetemcomitans strains tested. This reduction of the expression of these two exotoxins was time-dependent. These fundamental findings may indicate that lactobacilli can reduce the virulence of putative opportunistic oral pathogens, and may provide insights to future therapeutic approaches for the respective diseases.
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Affiliation(s)
- Lorenzo Nissen
- />Microbiology Area, Department. Agricultural Sciences, Alma Mater Studiorum, Università di Bologna, V.le Fanin 44, 40127 Bologna, Italy
| | - Barbara Sgorbati
- />Microbiology Area, Department. Agricultural Sciences, Alma Mater Studiorum, Università di Bologna, V.le Fanin 44, 40127 Bologna, Italy
| | - Bruno Biavati
- />Microbiology Area, Department. Agricultural Sciences, Alma Mater Studiorum, Università di Bologna, V.le Fanin 44, 40127 Bologna, Italy
| | - Georgios N. Belibasakis
- />Oral Microbiology and Immunology, Institute of Oral Biology, Center of Dental Medicine, University of Zürich, Plattenstrasse 11, 8032 Zürich, Switzerland
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Expression and secretion of the RTX-toxin GtxA among members of the genus Gallibacterium. Vet Microbiol 2011; 153:116-23. [DOI: 10.1016/j.vetmic.2011.05.019] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 05/02/2011] [Accepted: 05/10/2011] [Indexed: 11/16/2022]
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12
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Feuerbacher LA, Burgum A, Kolodrubetz D. The cyclic-AMP receptor protein (CRP) regulon in Aggregatibacter actinomycetemcomitans includes leukotoxin. Microb Pathog 2011; 51:133-41. [PMID: 21575705 PMCID: PMC3120918 DOI: 10.1016/j.micpath.2011.04.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 04/27/2011] [Accepted: 04/29/2011] [Indexed: 11/29/2022]
Abstract
The cyclic-AMP receptor protein (CRP) acts as a global regulatory protein among bacteria. Here, the CRP regulon has been defined in Aggregatibacter actinomycetemcomitans using microarray analysis of A. actinomycetemcomitans strain JP2 wild type cells compared to an isogenic crp deletion mutant. Genes whose expression levels changed at least 2-fold with p≤0.05 were considered significant. Of the 300 genes identified as being CRP-regulated, 139 were CRP-activated, including leukotoxin, with the remaining being CRP-repressed. The 300 genes represent 14.2% of ORFs probed which is significantly higher than what has been reported for CRP regulons in other bacteria. If the CRP-regulated genes are put into 17 functional classes, all 17 categories had at least 1 CRP-regulated gene. Several functional categories, mainly transport and binding proteins and energy metabolism proteins, were disproportionately represented in the CRP-regulated subset of genes relative to their overall representation in the genome. This is similar to the patterns seen in other bacteria. Finally, quantitative RT-PCR was used to show that the leukotoxin RNA levels were repressed 16-fold in the CRP mutant indicating that CRP activates leukotoxin transcription. However, this regulation appears to be acting through another regulatory protein since the leukotoxin promoter, unlike ∼129 other promoters of CRP-regulated genes, does not have a match to the consensus CRP-binding site. Several candidate genes for this intermediary transcription factor have been identified in the CRP regulon.
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Affiliation(s)
- Leigh A. Feuerbacher
- Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229-3900 USA
| | - Alex Burgum
- Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229-3900 USA
| | - David Kolodrubetz
- Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229-3900 USA
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13
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Isolation of a novel Aggregatibacter actinomycetemcomitans serotype b bacteriophage capable of lysing bacteria within a biofilm. Appl Environ Microbiol 2011; 77:3157-9. [PMID: 21378052 DOI: 10.1128/aem.02115-10] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
A bacteriophage specific for Aggregatibacter actinomycetemcomitans serotype b, able to kill the bacterium within a biofilm, was isolated. Random mutagenesis of this phage rendered a bacteriophage able to kill 99% of the bacteria within a biofilm. This is the first report of a biocontrol experiment against A. actinomycetemcomitans.
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14
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Henderson B, Ward JM, Ready D. Aggregatibacter (Actinobacillus) actinomycetemcomitans: a triple A* periodontopathogen? Periodontol 2000 2010; 54:78-105. [DOI: 10.1111/j.1600-0757.2009.00331.x] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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15
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Kachlany SC. Aggregatibacter actinomycetemcomitans leukotoxin: from threat to therapy. J Dent Res 2010; 89:561-70. [PMID: 20200418 DOI: 10.1177/0022034510363682] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Aggregatibacter actinomycetemcomitans is a Gram-negative bacterium that colonizes the human oral cavity and is the causative agent for localized aggressive periodontitis (LAP), an aggressive form of periodontal disease that occurs in adolescents. A. actinomycetemcomitans secretes a protein toxin, leukotoxin (LtxA), which helps the bacterium evade the host immune response during infection. LtxA is a membrane-active toxin that specifically targets white blood cells (WBCs). In this review, we discuss recent developments in this field, including the identification and characterization of genes and proteins involved in secretion, regulation of LtxA, biosynthesis, newly described activities of LtxA, and how LtxA may be used as a therapy for the treatment of diseases.
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Affiliation(s)
- S C Kachlany
- Department of Oral Biology, New Jersey Dental School, University of Medicine and Dentistry of New Jersey, 185 S. Orange Avenue, Medical Science Building C-636, Newark, NJ 07103, USA.
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Anti-leukemia activity of a bacterial toxin with natural specificity for LFA-1 on white blood cells. Leuk Res 2009; 34:777-85. [PMID: 19747730 DOI: 10.1016/j.leukres.2009.08.022] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 08/17/2009] [Accepted: 08/17/2009] [Indexed: 12/28/2022]
Abstract
The oral bacterium, Aggregatibacter actinomycetemcomitans, produces a leukotoxin (LtxA) that is specific for white blood cells (WBCs) from humans and Old World primates by interacting with lymphocyte function antigen-1 (LFA-1) on susceptible cells. To determine if LtxA could be used as a therapeutic agent for the treatment of WBC diseases, we tested the in vitro and in vivo anti-leukemia activity of the toxin. LtxA kills human malignant WBC lines and primary leukemia cells from acute myeloid leukemia patients, but healthy peripheral blood mononuclear cells (PBMCs) are relatively resistant to LtxA-mediated cytotoxicity. Levels of LFA-1 on cell lines correlated with killing by LtxA and the toxin preferentially killed cells expressing the activated form of LFA-1. In a SCID mouse model for human leukemia, LtxA had potent therapeutic value resulting in long-term survival in LtxA-treated mice. Intravenous infusion of LtxA into a rhesus macaque resulted in a drop in WBC counts at early times post-infusion; however, red blood cells, platelets, hemoglobin and blood chemistry values remained unaffected. Thus, LtxA may be an effective and safe novel therapeutic agent for the treatment of hematologic malignancies.
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Aggregatibacter actinomycetemcomitans LtxC is required for leukotoxin activity and initial interaction between toxin and host cells. Gene 2009; 443:42-7. [PMID: 19450669 DOI: 10.1016/j.gene.2009.05.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Revised: 05/06/2009] [Accepted: 05/08/2009] [Indexed: 11/21/2022]
Abstract
Aggregatibacter actinomycetemcomitans is a human pathogen that produces the RTX toxin (repeats in toxin), leukotoxin (LtxA). Based on other RTX toxin systems, the product of ltxC, the first gene of the ltx operon, is predicted to be involved in fatty acid modification of LtxA. To determine the function of ltxC in A. actinomycetemcomitans, we generated an ltxC mutation in the highly leukotoxic strain JP2N using random mutagenesis. The toxin from the ltxC mutant (LtxA(ltxC)) was expressed and secreted into the cell culture supernatant but could not lyse human leukocytes or erythrocytes. Mass spectrometric analysis of LtxA(ltxC) and LtxA from strain JP2N (LtxA(wt)) revealed two peptides that differed and this data suggests that two internal lysine residues of LtxA from the wild-type strain are modified. In blocking experiments, pre-treatment of cells with LtxA(ltxC) was unable to prevent LtxA(wt) from killing cells. Furthermore, in contrast to LtxA(wt), LtxA(ltxC) did not cause an increase in intracellular calcium levels in human leukocytes. Taken together, our data show that ltxC is required for full activity and modification of LtxA in A. actinomycetemcomitans and that modification is important for initial binding of toxin to host cells, as defined by an increase in intracellular calcium levels.
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