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McCurdy S, Halasohoris SA, Babyak AL, Lembirik S, Hoover R, Hickman M, Scarff J, Klimko CP, Cote CK, Meinig JM. Efficacy of delafloxacin against the biothreat pathogen Bacillus anthracis. J Antimicrob Chemother 2023; 78:810-816. [PMID: 36738250 DOI: 10.1093/jac/dkad015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 12/29/2022] [Indexed: 02/05/2023] Open
Abstract
OBJECTIVES To evaluate the in vitro activity and in vivo efficacy of delafloxacin against Bacillus anthracis, the causative agent of anthrax. METHODS MICs were obtained according to CLSI guidelines for 30 virulent isolates and 14 attenuated antibiotic-resistant strains. For the in vivo efficacy study, mice were administered delafloxacin (30-62.5 mg/kg) subcutaneously, or ciprofloxacin (30 mg/kg) intraperitoneally beginning at either 24 or 48 ± 1 h post-challenge (post-exposure prophylaxis) and continued every 12 h for 14 days with study termination on day 30. The mean inhaled dose in the study was approximately 103 × LD50 equivalents, and the range was 87-120 × LD50. RESULTS Delafloxacin (MIC90 = 0.004 mg/L) was 16-fold more potent than ciprofloxacin (MIC90 = 0.06 mg/L) against a 30-strain set of virulent B. anthracis. Against a panel of attenuated antibiotic-resistant strains, delafloxacin demonstrated potency ≥128-fold over that observed with ciprofloxacin. When evaluated in vivo, mice treated with all delafloxacin doses tested at 24 h post-challenge demonstrated equivalent survival compared with mice treated with the positive control ciprofloxacin. Because of the high challenge dose of spores, mice treated at 48 h showed rapid and high mortality in all groups including the positive control. Surviving animals in all delafloxacin- and ciprofloxacin-treated groups (24 and 48 h) showed complete splenic clearance of infection and <2.2 × 103 cfu/g lung tissue. CONCLUSIONS Given the high bar set by the 100 × LD50 challenge dose in this study, the results from delafloxacin treatment are promising for the treatment of inhaled anthrax.
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Affiliation(s)
- Sandra McCurdy
- Melinta Therapeutics, 44 Whippany Rd, Morristown, NJ, USA
| | - Stephanie A Halasohoris
- Bacteriology Division, US Army Medical Research Institute of Infectious Diseases (USAMRIID), 1425 Porter St., Fort Detrick, MD, USA
| | - Ashley L Babyak
- Bacteriology Division, US Army Medical Research Institute of Infectious Diseases (USAMRIID), 1425 Porter St., Fort Detrick, MD, USA
| | - Sanae Lembirik
- Bacteriology Division, US Army Medical Research Institute of Infectious Diseases (USAMRIID), 1425 Porter St., Fort Detrick, MD, USA
| | - Randall Hoover
- Pharmacology Consultant for Melinta Therapeutics, 15 Plane Tree Ln, Dix Hills, NY 11746, USA
| | - Mark Hickman
- Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense (JPEO-CBRND), CBRN Medical, 110 Thomas Johnson Dr., Suite 300, Frederick, MD, USA
| | - Jennifer Scarff
- Bacteriology Division, US Army Medical Research Institute of Infectious Diseases (USAMRIID), 1425 Porter St., Fort Detrick, MD, USA
| | - Christopher P Klimko
- Bacteriology Division, US Army Medical Research Institute of Infectious Diseases (USAMRIID), 1425 Porter St., Fort Detrick, MD, USA
| | - Christopher K Cote
- Bacteriology Division, US Army Medical Research Institute of Infectious Diseases (USAMRIID), 1425 Porter St., Fort Detrick, MD, USA
| | - J Matthew Meinig
- Bacteriology Division, US Army Medical Research Institute of Infectious Diseases (USAMRIID), 1425 Porter St., Fort Detrick, MD, USA
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Shinde S, Miryala SK, Anbarasu A, Ramaiah S. Systems biology approach to understand the interplay between Bacillus anthracis and human host genes that leads to CVDs. Microb Pathog 2023; 176:106019. [PMID: 36736801 DOI: 10.1016/j.micpath.2023.106019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 01/28/2023] [Accepted: 01/31/2023] [Indexed: 02/04/2023]
Abstract
Humans infected with invasive Bacillus anthracis (B. anthracis) have a very poor prognosis and are at high risk for developing cardiovascular diseases (CVDs) and shock. Several bacterial elements probably have significant pathogenic roles in this pathogenic process of anthrax. In our current work, we have analysed the molecular level interactions between B. anthracis and human genes to understand the interplay during anthrax that leads to the CVDs. Our results have shown dense interactions between the functional partners in both host and the B. anthracis Gene interaction network (GIN). The functional enrichment analysis indicated that the clusters in the host GIN had genes related to hypoxia and autophagy in response to the lethal toxin; and genes related to adherens junction and actin cytoskeleton in response to edema toxin play a significant role in multiple stages of the disease. The B. anthracis genes BA_0530, guaA, polA, rpoB, ribD, secDF, metS, dinG and human genes ACTB, EGFR, EP300, CTNNB1, ESR1 have shown more than 50 direct interactions with the functional partners and hence they can be considered as hub genes in the network and they are observed to have important roles in CVDs. The outcome of our study will help to understand the molecular pathogenesis of CVDs in anthrax. The hub genes reported in the study can be considered potential drug targets and they can be exploited for new drug discovery.
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Affiliation(s)
- Shabduli Shinde
- School of Medical Science and Technology, Indian Institute of Technology, Kharagpur, Kharagpur, 721302, West Bengal, India
| | - Sravan Kumar Miryala
- Medical and Biological Computing Laboratory, School of Biosciences and Technology, Vellore Institute of Technology (VIT), Vellore, 632014, Tamil Nadu, India
| | - Anand Anbarasu
- Medical and Biological Computing Laboratory, School of Biosciences and Technology, Vellore Institute of Technology (VIT), Vellore, 632014, Tamil Nadu, India
| | - Sudha Ramaiah
- Medical and Biological Computing Laboratory, School of Biosciences and Technology, Vellore Institute of Technology (VIT), Vellore, 632014, Tamil Nadu, India.
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Rohokale R, Guo Z. Development in the Concept of Bacterial Polysaccharide Repeating Unit-Based Antibacterial Conjugate Vaccines. ACS Infect Dis 2023; 9:178-212. [PMID: 36706246 PMCID: PMC9930202 DOI: 10.1021/acsinfecdis.2c00559] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The surface of cells is coated with a dense layer of glycans, known as the cell glycocalyx. The complex glycans in the glycocalyx are involved in various biological events, such as bacterial pathogenesis, protection of bacteria from environmental stresses, etc. Polysaccharides on the bacterial cell surface are highly conserved and accessible molecules, and thus they are excellent immunological targets. Consequently, bacterial polysaccharides and their repeating units have been extensively studied as antigens for the development of antibacterial vaccines. This Review surveys the recent developments in the synthetic and immunological investigations of bacterial polysaccharide repeating unit-based conjugate vaccines against several human pathogenic bacteria. The major challenges associated with the development of functional carbohydrate-based antibacterial conjugate vaccines are also considered.
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4
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Boyer AE, Gallegos-Candela M, Lins RC, Solano MI, Woolfitt AR, Lee JS, Sanford DC, Knostman KAB, Quinn CP, Hoffmaster AR, Pirkle JL, Barr JR. Comprehensive characterization of toxins during progression of inhalation anthrax in a non-human primate model. PLoS Pathog 2022; 18:e1010735. [PMID: 36534695 PMCID: PMC9810172 DOI: 10.1371/journal.ppat.1010735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 01/03/2023] [Accepted: 11/28/2022] [Indexed: 12/23/2022] Open
Abstract
Inhalation anthrax has three clinical stages: early-prodromal, intermediate-progressive, and late-fulminant. We report the comprehensive characterization of anthrax toxins, including total protective antigen (PA), total lethal factor (LF), total edema factor (EF), and their toxin complexes, lethal toxin and edema toxin in plasma, during the course of inhalation anthrax in 23 cynomolgus macaques. The toxin kinetics were predominantly triphasic with an early rise (phase-1), a plateau/decline (phase-2), and a final rapid rise (phase-3). Eleven animals had shorter survival times, mean±standard deviation of 58.7±7.6 hours (fast progression), 11 animals had longer survival times, 113±34.4 hours (slow progression), and one animal survived. Median (lower-upper quartile) LF levels at the end-of-phase-1 were significantly higher in animals with fast progression [138 (54.9-326) ng/mL], than in those with slow progression [23.8 (15.6-26.3) ng/mL] (p = 0.0002), and the survivor (11.1 ng/mL). The differences were also observed for other toxins and bacteremia. Animals with slow progression had an extended phase-2 plateau, with low variability of LF levels across all time points and animals. Characterization of phase-2 toxin levels defined upper thresholds; critical levels for exiting phase-2 and entering the critical phase-3, 342 ng/mL (PA), 35.8 ng/mL (LF), and 1.10 ng/mL (EF). The thresholds were exceeded earlier in animals with fast progression (38.5±7.4 hours) and later in animals with slow progression (78.7±15.2 hours). Once the threshold was passed, toxin levels rose rapidly in both groups to the terminal stage. The time from threshold to terminal was rapid and similar; 20.8±7.4 hours for fast and 19.9±7.5 hours for slow progression. The three toxemic phases were aligned with the three clinical stages of anthrax for fast and slow progression which showed that anthrax progression is toxin- rather than time-dependent. This first comprehensive evaluation of anthrax toxins provides new insights into disease progression.
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Affiliation(s)
- Anne E. Boyer
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
- * E-mail:
| | | | - Renato C. Lins
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
- Battelle Atlanta Analytical Services, Atlanta, Georgia, United States of America
| | - Maria I. Solano
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Adrian R. Woolfitt
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - John S. Lee
- Biomedical Advanced Research and Development Authority, Washington, DC, United States of America
| | - Daniel C. Sanford
- Battelle Biomedical Research Center, West Jefferson, Ohio, United States of America
| | | | - Conrad P. Quinn
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Alex R. Hoffmaster
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - James L. Pirkle
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - John R. Barr
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
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Williams B, López-García M, Gillard JJ, Laws TR, Lythe G, Carruthers J, Finnie T, Molina-París C. A Stochastic Intracellular Model of Anthrax Infection With Spore Germination Heterogeneity. Front Immunol 2021; 12:688257. [PMID: 34497601 PMCID: PMC8420810 DOI: 10.3389/fimmu.2021.688257] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 07/01/2021] [Indexed: 12/02/2022] Open
Abstract
We present a stochastic mathematical model of the intracellular infection dynamics of Bacillus anthracis in macrophages. Following inhalation of B. anthracis spores, these are ingested by alveolar phagocytes. Ingested spores then begin to germinate and divide intracellularly. This can lead to the eventual death of the host cell and the extracellular release of bacterial progeny. Some macrophages successfully eliminate the intracellular bacteria and will recover. Here, a stochastic birth-and-death process with catastrophe is proposed, which includes the mechanism of spore germination and maturation of B. anthracis. The resulting model is used to explore the potential for heterogeneity in the spore germination rate, with the consideration of two extreme cases for the rate distribution: continuous Gaussian and discrete Bernoulli. We make use of approximate Bayesian computation to calibrate our model using experimental measurements from in vitro infection of murine peritoneal macrophages with spores of the Sterne 34F2 strain of B. anthracis. The calibrated stochastic model allows us to compute the probability of rupture, mean time to rupture, and rupture size distribution, of a macrophage that has been infected with one spore. We also obtain the mean spore and bacterial loads over time for a population of cells, each assumed to be initially infected with a single spore. Our results support the existence of significant heterogeneity in the germination rate, with a subset of spores expected to germinate much later than the majority. Furthermore, in agreement with experimental evidence, our results suggest that most of the spores taken up by macrophages are likely to be eliminated by the host cell, but a few germinated spores may survive phagocytosis and lead to the death of the infected cell. Finally, we discuss how this stochastic modelling approach, together with dose-response data, allows us to quantify and predict individual infection risk following exposure.
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Affiliation(s)
- Bevelynn Williams
- Department of Applied Mathematics, School of Mathematics, University of Leeds, Leeds, United Kingdom
| | - Martín López-García
- Department of Applied Mathematics, School of Mathematics, University of Leeds, Leeds, United Kingdom
| | - Joseph J. Gillard
- CBR Division, Defence Science and Technology Laboratory, Salisbury, United Kingdom
| | - Thomas R. Laws
- CBR Division, Defence Science and Technology Laboratory, Salisbury, United Kingdom
| | - Grant Lythe
- Department of Applied Mathematics, School of Mathematics, University of Leeds, Leeds, United Kingdom
| | - Jonathan Carruthers
- Emergency Response Department, Public Health England, Salisbury, United Kingdom
| | - Thomas Finnie
- Emergency Response Department, Public Health England, Salisbury, United Kingdom
| | - Carmen Molina-París
- Department of Applied Mathematics, School of Mathematics, University of Leeds, Leeds, United Kingdom
- T-6, Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, United States
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Abstract
AtxA, the master virulence regulator of Bacillus anthracis, regulates the expression of three toxins and genes for capsule formation that are required for the pathogenicity of B. anthracis. Recent transcriptome analyses showed that AtxA affects a large number of genes on the chromosome and plasmids, suggesting a role as a global regulator. However, information on genes directly regulated by AtxA is scarce. In this work, we conducted genome-wide analyses and cataloged the binding sites of AtxA in vivo and transcription start sites on the B. anthracis genome. By integrating these results, we detected eight genes as direct regulons of AtxA. These consisted of five protein-coding genes, including two of the three toxin genes, and three genes encoding the small RNAs XrrA and XrrB and a newly discovered 95-nucleotide small RNA, XrrC. Transcriptomes from single-knockout mutants of these small RNAs revealed changes in the transcription levels of genes related to the aerobic electron transport chain, heme biosynthesis, and amino acid metabolism, suggesting their function for the control of cell physiology. These results reveal the first layer of the gene regulatory network for the pathogenicity of B. anthracis and provide a data set for the further study of the genomics and genetics of B. anthracis. IMPORTANCEBacillus anthracis is the Gram-positive bacterial species that causes anthrax. Anthrax is still prevalent in countries mainly in Asia and Africa, where it causes economic damage and remains a public health issue. The mechanism of pathogenicity is mainly explained by the three toxin proteins expressed from the pXO1 plasmid and by proteins involved in capsule formation expressed from the pXO2 plasmid. AtxA is a protein expressed from the pXO1 plasmid that is known to upregulate genes involved in toxin production and capsule formation and is thus considered the master virulence regulator of B. anthracis. Therefore, understanding the detailed mechanism of gene regulation is important for the control of anthrax. The significance of this work lies in the identification of genes that are directly regulated by AtxA via genome-wide analyses. The results reveal the first layer of the gene regulatory network for the pathogenicity of B. anthracis and provide useful resources for a further understanding of B. anthracis.
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7
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Immunogenicity and Protective Efficacy of a Non-Living Anthrax Vaccine versus a Live Spore Vaccine with Simultaneous Penicillin-G Treatment in Cattle. Vaccines (Basel) 2020; 8:vaccines8040595. [PMID: 33050254 PMCID: PMC7711464 DOI: 10.3390/vaccines8040595] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 09/29/2020] [Accepted: 10/01/2020] [Indexed: 11/17/2022] Open
Abstract
Sterne live spore vaccine (SLSV) is the current veterinary anthrax vaccine of choice. Unlike the non-living anthrax vaccine (NLAV) prototype, SLSV is incompatible with concurrent antibiotics use in an anthrax outbreak scenario. The NLAV candidates used in this study include a crude recombinant protective antigen (CrPA) and a purified recombinant protective antigen (PrPA) complemented by formalin-inactivated spores and Emulsigen-D®/Alhydrogel® adjuvants. Cattle were vaccinated twice (week 0 and 3) with NLAVs plus penicillin-G (Pen-G) treatment and compared to cattle vaccinated twice with SLSV alone and with Pen-G treatment. The immunogenicity was assessed using ELISA against rPA and FIS, toxin neutralisation assay (TNA) and opsonophagocytic assay. The protection was evaluated using an in vivo passive immunisation mouse model. The anti-rPA IgG titres for NLAVs plus Pen-G and SLSV without Pen-G treatment showed a significant increase, whereas the titres for SLSV plus Pen-G were insignificant compared to pre-vaccination values. A similar trend was measured for IgM, IgG1, and IgG2 and TNA titres (NT50) showed similar trends to anti-rPA titres across all vaccine groups. The anti-FIS IgG and IgM titres increased significantly for all vaccination groups at week 3 and 5 when compared to week 0. The spore opsonising capacity increased significantly in the NLAV vaccinated groups including Pen-G treatment and the SLSV without Pen-G but much less in the SLSV group with Pen-G treatment. Passive immunization of A/J mice challenged with a lethal dose of 34F2 spores indicated significant protective capacity of antibodies raised in the SLSV and the PrPA + FIS + adjuvants vaccinated and Pen-G treated groups but not for the NLAV with the CrPA + FIS + adjuvants and the SLSV vaccinated and Pen-G treated group. Our findings indicate that the PrPA + FIS + Emulsigen-D®/Alhydrogel® vaccine candidate may provide the same level of antibody responses and protective capacity as the SLSV. Advantageously, it can be used concurrently with Penicillin-G in an outbreak situation and as prophylactic treatment in feedlots and valuable breeding stocks.
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8
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Rougeaux C, Becher F, Goossens PL, Tournier JN. Very Early Blood Diffusion of the Active Lethal and Edema Factors of Bacillus anthracis After Intranasal Infection. J Infect Dis 2020; 221:660-667. [PMID: 31574153 PMCID: PMC6996859 DOI: 10.1093/infdis/jiz497] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 09/30/2019] [Indexed: 11/22/2022] Open
Abstract
Background Lethal and edema toxins are critical virulence factors of Bacillus anthracis. Few data are available on their presence in the early stage of intranasal infection. Methods To investigate the diffusion of edema factor (EF) and lethal factor (LF), we use sensitive quantitative methods to measure their enzymatic activities in mice intranasally challenged with a wild-type B anthracis strain or with an isogenic mutant deficient for the protective antigen. Results One hour after mouse challenge, although only 7% of mice presented bacteremia, LF and EF were detected in the blood of 100% and 42% of mice, respectively. Protective antigen facilitated the diffusion of LF and EF into the blood compartment. Toxins played a significant role in the systemic dissemination of B anthracis in the blood, spleen, and liver. A mouse model of intoxination further confirmed that LT and ET could diffuse rapidly in the circulation, independently of bacteria. Conclusions In this inhalational model, toxins have disseminated rapidly in the blood, playing a significant and novel role in the early systemic diffusion of bacteria, demonstrating that they may represent a very early target for the diagnosis and the treatment of anthrax.
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Affiliation(s)
- Clémence Rougeaux
- Unité Biothérapies Anti-Infectieuses et Immunité, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France.,Pathogénie des Toxi-Infections Bactériennes, Institut Pasteur, Paris, France
| | - François Becher
- Service de Pharmacologie et d'Immunoanalyse, Laboratoire d'Etude du Métabolisme des Médicaments, Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut National de la Recherche Agronomique, Université Paris Saclay, Gif-sur-Yvette, France
| | - Pierre L Goossens
- Pathogénie des Toxi-Infections Bactériennes, Institut Pasteur, Paris, France
| | - Jean-Nicolas Tournier
- Unité Biothérapies Anti-Infectieuses et Immunité, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France.,Pathogénie des Toxi-Infections Bactériennes, Institut Pasteur, Paris, France.,Ecole du Val-de-Grâce, Paris, France.,Centre National de Référence-Laboratoire Expert Charbon, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France
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Patel VI, Booth JL, Dozmorov M, Brown BR, Metcalf JP. Anthrax Edema and Lethal Toxins Differentially Target Human Lung and Blood Phagocytes. Toxins (Basel) 2020; 12:toxins12070464. [PMID: 32698436 PMCID: PMC7405021 DOI: 10.3390/toxins12070464] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 07/14/2020] [Accepted: 07/15/2020] [Indexed: 12/26/2022] Open
Abstract
Bacillus anthracis, the causative agent of inhalation anthrax, is a serious concern as a bioterrorism weapon. The vegetative form produces two exotoxins: Lethal toxin (LT) and edema toxin (ET). We recently characterized and compared six human airway and alveolar-resident phagocyte (AARP) subsets at the transcriptional and functional levels. In this study, we examined the effects of LT and ET on these subsets and human leukocytes. AARPs and leukocytes do not express high levels of the toxin receptors, tumor endothelium marker-8 (TEM8) and capillary morphogenesis protein-2 (CMG2). Less than 20% expressed surface TEM8, while less than 15% expressed CMG2. All cell types bound or internalized protective antigen, the common component of the two toxins, in a dose-dependent manner. Most protective antigen was likely internalized via macropinocytosis. Cells were not sensitive to LT-induced apoptosis or necrosis at concentrations up to 1000 ng/mL. However, toxin exposure inhibited B. anthracis spore internalization. This inhibition was driven primarily by ET in AARPs and LT in leukocytes. These results support a model of inhalation anthrax in which spores germinate and produce toxins. ET inhibits pathogen phagocytosis by AARPs, allowing alveolar escape. In late-stage disease, LT inhibits phagocytosis by leukocytes, allowing bacterial replication in the bloodstream.
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Affiliation(s)
- Vineet I. Patel
- Department of Medicine, Pulmonary, Critical Care & Sleep Medicine, the University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (V.I.P.); (J.L.B.); (B.R.B.)
| | - J. Leland Booth
- Department of Medicine, Pulmonary, Critical Care & Sleep Medicine, the University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (V.I.P.); (J.L.B.); (B.R.B.)
| | - Mikhail Dozmorov
- Department of Biostatistics, Virginia Commonwealth University, Richmond, VA 23298, USA;
| | - Brent R. Brown
- Department of Medicine, Pulmonary, Critical Care & Sleep Medicine, the University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (V.I.P.); (J.L.B.); (B.R.B.)
| | - Jordan P. Metcalf
- Department of Medicine, Pulmonary, Critical Care & Sleep Medicine, the University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (V.I.P.); (J.L.B.); (B.R.B.)
- Department of Microbiology and Immunology, the University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Veterans Affairs Medical Center, Oklahoma City, OK 73104, USA
- Correspondence:
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Jauro S, C. Ndumnego O, Ellis C, Buys A, Beyer W, van Heerden H. Immunogenicity of Non-Living Anthrax Vaccine Candidates in Cattle and Protective Efficacy of Immune Sera in A/J Mouse Model Compared to the Sterne Live Spore Vaccine. Pathogens 2020; 9:pathogens9070557. [PMID: 32664259 PMCID: PMC7400155 DOI: 10.3390/pathogens9070557] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 06/29/2020] [Accepted: 06/29/2020] [Indexed: 11/16/2022] Open
Abstract
The Sterne live spore vaccine (SLSV, Bacillus anthracis strain 34F2) is the veterinary vaccine of choice against anthrax though contra-indicated for use with antimicrobials. However, the use of non-living anthrax vaccine (NLAV) candidates can overcome the SLSV limitation. In this study, cattle were vaccinated with either of the NLAV (purified recombinant PA (PrPA) or crude rPA (CrPA) and formaldehyde-inactivated spores (FIS of B. anthracis strain 34F2) and emulsigen-D®/alhydrogel® adjuvants) or SLSV. The immunogenicity of the NLAV and SLSV was assessed and the protective efficacies evaluated using a passive immunization mouse model. Polyclonal IgG (including the IgG1 subset) and IgM responses increased significantly across all vaccination groups after the first vaccination. Individual IgG subsets titres peaked significantly with all vaccines used after the second vaccination at week 5 and remained significant at week 12 when compared to week 0. The toxin neutralization (TNA) titres of the NLAV vaccinated cattle groups showed similar trends to those observed with the ELISA titres, except that the former were lower, but still significant, when compared to week 0. The opsonophagocytic assay indicated good antibody opsonizing responses with 75% (PrPA+FIS), 66% (CrPA+FIS) and 80% (SLSV) phagocytosis following spores opsonization. In the passive protection test, A/J mice transfused with purified IgG from cattle vaccinated with PrPA+FIS+Emulsigen-D®/Alhydrogel® and SLSV had 73% and 75% protection from challenge with B. anthracis strain 34F2 spores, respectively, whereas IgG from cattle vaccinated with CrPA+FIS+Emulsigen-D®/Alhydrogel® offered insignificant protection of 20%. There was no difference in protective immune response in cattle vaccinated twice with either the PrPA+FIS or SLSV. Moreover, PrPA+FIS did not show any residual side effects in vaccinated cattle. These results suggest that the immunogenicity and protective efficacy induced by the NLAV (PrPA+FIS) in the cattle and passive mouse protection test, respectively, are comparable to that induced by the standard SLSV.
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Affiliation(s)
- Solomon Jauro
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, Pretoria 0110, South Africa;
- Department of Veterinary Microbiology, Faculty of Veterinary Medicine, University of Maiduguri, Maiduguri 600230, Nigeria
- Correspondence:
| | | | - Charlotte Ellis
- Design Biologix, Building 43b CSIR, Meiring Naude Road, Brummeria 0184, South Africa; (C.E.); (A.B.)
| | - Angela Buys
- Design Biologix, Building 43b CSIR, Meiring Naude Road, Brummeria 0184, South Africa; (C.E.); (A.B.)
| | - Wolfgang Beyer
- Department of Livestock Infectiology and Environmental Hygiene, Institute of Animal Science, University of Hohenheim, Stuttgart 70599, Germany;
| | - Henriette van Heerden
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, Pretoria 0110, South Africa;
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11
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Physiological Responses to a Single Low-Dose of Bacillus anthracis Spores in the Rabbit Model of Inhalational Anthrax. Pathogens 2020; 9:pathogens9060461. [PMID: 32545184 PMCID: PMC7350313 DOI: 10.3390/pathogens9060461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Revised: 06/04/2020] [Accepted: 06/06/2020] [Indexed: 11/25/2022] Open
Abstract
Credible dose–response relationships are needed to more accurately assess the risk posed by exposure to low-level Bacillus anthracis contamination during or following a release. To begin to fill this knowledge gap, New Zealand White rabbits were implanted with D70-PCT telemetry transmitters and subsequently aerosol challenged with average inhaled doses of 2.86 × 102 to 2.75 × 105 colony forming units (CFU) of B. anthracis spores. Rabbits exposed to a single inhaled dose at or above 2.54 × 104 CFU succumbed with dose-dependent time to death. Death was associated with increases above baseline in heart rate, respiration rate, and body temperature and all rabbits that died exhibited bacteremia at some point prior to death. Rabbits that inhaled doses of 2.06 × 103 CFU or lower survived to the end of the study and showed no or minimal adverse changes in the measured physiological responses in response to the challenge. Moreover, no bacteremia nor toxemia were observed in rabbits that survived to the end of the study. Overall, the data indicate that challenge doses of B. anthracis below the level sufficient to establish systemic infection do not produce observable physiological responses; however, doses that triggered a response resulted in death.
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Majumder S, Das S, Kingston J, Shivakiran MS, Batra HV, Somani VK, Bhatnagar R. Functional characterization and evaluation of protective efficacy of EA752-862 monoclonal antibody against B. anthracis vegetative cell and spores. Med Microbiol Immunol 2019; 209:125-137. [PMID: 31811379 DOI: 10.1007/s00430-019-00650-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Accepted: 11/22/2019] [Indexed: 08/30/2023]
Abstract
The most promising means of controlling anthrax, a lethal zoonotic disease during the early infection stages, entail restricting the resilient infectious form, i.e., the spores from proliferating to replicating bacilli in the host. The extractible antigen (EA1), a major S-layer protein present on the vegetative cells and spores of Bacillus anthracis, is highly immunogenic and protects mice against lethal challenge upon immunization. In the present study, mice were immunized with r-EA1C, the C terminal crystallization domain of EA1, to generate a neutralizing monoclonal antibody EA752-862, that was evaluated for its anti-spore and anti-bacterial properties. The monoclonal antibody EA752-862 had a minimum inhibitory concentration of 0.08 mg/ml, was bactericidal at a concentration of 0.1 mg/ml and resulted in 100% survival of mice against challenge with B. anthracis vegetative cells. Bacterial cell lysis as observed by scanning electron microscopy and nucleic acid leakage assay could be attributed as a possible mechanism for the bactericidal property. The association of mAb EA752-862 with spores inhibits their subsequent germination to vegetative cells in vitro, enhances phagocytosis of the spores and killing of the vegetative cells within the macrophage, and subsequently resulted in 90% survival of mice upon B. anthracis Ames spore challenge. Therefore, owing to its anti-spore and bactericidal properties, the present study demonstrates mAb EA752-862 as an efficient neutralizing antibody that hinders the establishment of early infection before massive multiplication and toxin release takes place.
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Affiliation(s)
- Saugata Majumder
- Microbiology Division, Defence Food Research Laboratory, Mysore, 570011, India
| | - Shreya Das
- Microbiology Division, Defence Food Research Laboratory, Mysore, 570011, India
| | - Joseph Kingston
- Microbiology Division, Defence Food Research Laboratory, Mysore, 570011, India.
| | - M S Shivakiran
- Microbiology Division, Defence Food Research Laboratory, Mysore, 570011, India
| | - H V Batra
- Microbiology Division, Defence Food Research Laboratory, Mysore, 570011, India
| | - Vikas Kumar Somani
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Rakesh Bhatnagar
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India
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Ndumnego OC, Koehler SM, Crafford JE, Beyer W, van Heerden H. Immunogenicity of anthrax recombinant peptides and killed spores in goats and protective efficacy of immune sera in A/J mouse model. Sci Rep 2018; 8:16937. [PMID: 30446695 PMCID: PMC6240085 DOI: 10.1038/s41598-018-35382-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 11/02/2018] [Indexed: 11/09/2022] Open
Abstract
Anthrax is primarily recognized as an affliction of herbivores with incubation period ranging from three to five days post-infection. Currently, the Sterne live-spore vaccine is the only vaccine approved for control of the disease in susceptible animals. While largely effective, the Sterne vaccine has several problems including adverse reactions in sensitive species, ineffectiveness in active outbreaks and incompatibility with antibiotics. These can be surmounted with the advent of recombinant peptides (non-living) next generation vaccines. The candidate vaccine antigens comprised of recombinant protective antigen (PA), spore-specific antigen (bacillus collagen-like protein of anthracis, BclA) and formaldehyde inactivated spores (FIS). Presently, little information exists on the protectivity of these novel vaccine candidates in susceptible ruminants. Thus, this study sought to assess the immunogenicity of these vaccine candidates in goats and evaluate their protectivity using an in vivo mouse model. Goats receiving a combination of PA, BclA and FIS yielded the highest antibody and toxin neutralizing titres compared to recombinant peptides alone. This was also reflected in the passive immunization experiment whereby mice receiving immune sera from goats vaccinated with the antigen combination had higher survival post-challenge. In conclusion, the current data indicate promising potential for further development of non-living anthrax vaccines in ruminants.
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Affiliation(s)
- Okechukwu C Ndumnego
- Department of Veterinary Tropical Diseases, University of Pretoria, Onderstepoort, South Africa. .,Africa Health Research Institute, Durban, South Africa.
| | - Susanne M Koehler
- Institute of Animal Science, Department of Livestock Infectiology and Environmental Hygiene, University of Hohenheim, Stuttgart, Germany.,Robert Koch Institute, Berlin, Germany
| | - Jannie E Crafford
- Department of Veterinary Tropical Diseases, University of Pretoria, Onderstepoort, South Africa
| | - Wolfgang Beyer
- Institute of Animal Science, Department of Livestock Infectiology and Environmental Hygiene, University of Hohenheim, Stuttgart, Germany
| | - Henriette van Heerden
- Department of Veterinary Tropical Diseases, University of Pretoria, Onderstepoort, South Africa.
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Petrobactin Protects against Oxidative Stress and Enhances Sporulation Efficiency in Bacillus anthracis Sterne. mBio 2018; 9:mBio.02079-18. [PMID: 30401780 PMCID: PMC6222121 DOI: 10.1128/mbio.02079-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Bacillus anthracis causes the disease anthrax, which is transmitted via its dormant, spore phase. However, conversion from bacillus to spore is a complex, energetically costly process that requires many nutrients, including iron. B. anthracis requires the siderophore petrobactin to scavenge iron from host environments. We show that, in the Sterne strain, petrobactin is required for efficient sporulation, even when ample iron is available. The petrobactin biosynthesis operon is expressed during sporulation, and petrobactin is biosynthesized during growth in high-iron sporulation medium, but instead of being exported, the petrobactin remains intracellular to protect against oxidative stress and improve sporulation. It is also required for full growth and sporulation in blood (bovine), an essential step for anthrax transmission between mammalian hosts. Bacillus anthracis is a Gram-positive bacillus that under conditions of environmental stress, such as low nutrients, can convert from a vegetative bacillus to a highly durable spore that enables long-term survival. The sporulation process is regulated by a sequential cascade of dedicated transcription factors but requires key nutrients to complete, one of which is iron. Iron acquisition by the iron-scavenging siderophore petrobactin is required for vegetative growth of B. anthracis under iron-depleted conditions and in the host. However, the extent to which petrobactin is involved in spore formation is unknown. This work shows that efficient in vitro sporulation of B. anthracis requires petrobactin, that the petrobactin biosynthesis operon (asbA to -F) is induced prior to sporulation, and that the siderophore itself associates with spores. Petrobactin is also required for oxidative stress protection during late-stage growth and for wild-type levels of sporulation in sporulation medium. Sporulation in bovine blood was found to be petrobactin dependent. Collectively, the in vitro contributions of petrobactin to sporulation as well as growth imply that petrobactin may be required for B. anthracis transmission via the spore during natural infections, in addition to its key known functions during active anthrax infections.
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Majumder S, Das S, Somani V, Makam SS, Joseph KJ, Bhatnagar R. A bivalent protein r-PB, comprising PA and BclA immunodominant regions for comprehensive protection against Bacillus anthracis. Sci Rep 2018; 8:7242. [PMID: 29740033 PMCID: PMC5940697 DOI: 10.1038/s41598-018-25502-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 04/23/2018] [Indexed: 01/09/2023] Open
Abstract
Anthrax infection is primarily initiated by B. anthracis endospores that on entry into the host germinate to vegetative cells and cause severe bacteremia and toxaemia employing an array of host colonisation factors and the lethal tripartite toxin. The protective efficacy of conventional protective antigen (PA) based anthrax vaccines is improved by co-administration with inactivated spores or its components. In the present study, using structural vaccinology rationale we synthesized a bivalent protein r-PB encompassing toxin (PAIV) and spore components (BclACTD) and characterized its protective efficacy against B. anthracis infection. Active immunization of mice with r-PB generated high titer circulating antibodies which facilitated the phagocytic uptake of spores, inhibited their germination to vegetative cells and completely neutralized anthrax toxins in vivo resulting in 100 % survival against anthrax toxin challenge. Proliferation of CD4+ T cell subsets with up-regulation of Th1 (IFN-γ, IL-2, and IL-12), Th2 (IL-5, IL-10) cytokines and balanced expression of IgG1:IgG2a antibody isotypes indicated the stimulation of both Th1 and Th2 subsets. The immunized mice exhibited 100 % survival upon challenge with B. anthracis spores or toxin indicating the ability of r-PB to provide comprehensive protection against anthrax. Our results thus demonstrate r-PB an efficient vaccine candidate against anthrax infection.
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Affiliation(s)
- Saugata Majumder
- Microbiology Division, Defence Food Research Laboratory, Defence Research Development Organisation, Mysore, 570011, India
| | - Shreya Das
- Microbiology Division, Defence Food Research Laboratory, Defence Research Development Organisation, Mysore, 570011, India
| | - Vikas Somani
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Shivakiran S Makam
- Microbiology Division, Defence Food Research Laboratory, Defence Research Development Organisation, Mysore, 570011, India
| | - Kingston J Joseph
- Microbiology Division, Defence Food Research Laboratory, Defence Research Development Organisation, Mysore, 570011, India.
| | - Rakesh Bhatnagar
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, 110067, India
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Tetrazole-Based trans-Translation Inhibitors Kill Bacillus anthracis Spores To Protect Host Cells. Antimicrob Agents Chemother 2017; 61:AAC.01199-17. [PMID: 28760903 DOI: 10.1128/aac.01199-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 07/21/2017] [Indexed: 12/29/2022] Open
Abstract
Bacillus anthracis, the causative agent of anthrax, remains a significant threat to humans, including potential use in bioterrorism and biowarfare. The capacity to engineer strains with increased pathogenicity coupled with the ease of disseminating lethal doses of B. anthracis spores makes it necessary to identify chemical agents that target and kill spores. Here, we demonstrate that a tetrazole-based trans-translation inhibitor, KKL-55, is bactericidal against vegetative cells of B. anthracis in culture. Using a fluorescent analog, we show that this class of compounds colocalizes with developing endospores and bind purified spores in vitro KKL-55 was effective against spores at concentrations close to its MIC for vegetative cells. Spore germination was inhibited at 1.2× MIC, and spores were killed at 2× MIC. In contrast, ciprofloxacin killed germinants at concentrations close to its MIC but did not prevent germination even at 32× MIC. Because toxins are released by germinants, macrophages infected by B. anthracis spores are killed early in the germination process. At ≥2× MIC, KKL-55 protected macrophages from death after infection with B. anthracis spores. Ciprofloxacin required concentrations of ≥8× MIC to exhibit a similar effect. Taken together, these data indicate that KKL-55 and related tetrazoles are good lead candidates for therapeutics targeting B. anthracis spores and suggest that there is an early requirement for trans-translation in germinating spores.
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Patel VI, Booth JL, Duggan ES, Cate S, White VL, Hutchings D, Kovats S, Burian DM, Dozmorov M, Metcalf JP. Transcriptional Classification and Functional Characterization of Human Airway Macrophage and Dendritic Cell Subsets. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2017; 198:1183-1201. [PMID: 28031342 PMCID: PMC5262539 DOI: 10.4049/jimmunol.1600777] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 11/28/2016] [Indexed: 12/20/2022]
Abstract
The respiratory system is a complex network of many cell types, including subsets of macrophages and dendritic cells that work together to maintain steady-state respiration. Owing to limitations in acquiring cells from healthy human lung, these subsets remain poorly characterized transcriptionally and phenotypically. We set out to systematically identify these subsets in human airways by developing a schema of isolating large numbers of cells by whole-lung bronchoalveolar lavage. Six subsets of phagocytic APC (HLA-DR+) were consistently observed. Aside from alveolar macrophages, subsets of Langerin+, BDCA1-CD14+, BDCA1+CD14+, BDCA1+CD14-, and BDCA1-CD14- cells were identified. These subsets varied in their ability to internalize Escherichia coli, Staphylococcus aureus, and Bacillus anthracis particles. All subsets were more efficient at internalizing S. aureus and B. anthracis compared with E. coli Alveolar macrophages and CD14+ cells were overall more efficient at particle internalization compared with the four other populations. Subsets were further separated into two groups based on their inherent capacities to upregulate surface CD83, CD86, and CCR7 expression levels. Whole-genome transcriptional profiling revealed a clade of "true dendritic cells" consisting of Langerin+, BDCA1+CD14+, and BDCA1+CD14- cells. The dendritic cell clade was distinct from a macrophage/monocyte clade, as supported by higher mRNA expression levels of several dendritic cell-associated genes, including CD1, FLT3, CX3CR1, and CCR6 Each clade, and each member of both clades, was discerned by specific upregulated genes, which can serve as markers for future studies in healthy and diseased states.
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Affiliation(s)
- Vineet I Patel
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
- Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
| | - J Leland Booth
- Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
| | - Elizabeth S Duggan
- Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
| | - Steven Cate
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
| | - Vicky L White
- Office of Aviation Medicine, Federal Aviation Administration, Oklahoma City, OK 73169
| | | | - Susan Kovats
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104; and
| | - Dennis M Burian
- Office of Aviation Medicine, Federal Aviation Administration, Oklahoma City, OK 73169
| | - Mikhail Dozmorov
- Department of Biostatistics, Virginia Commonwealth University, Richmond, VA 23298
| | - Jordan P Metcalf
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104;
- Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
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Progress toward the Development of a NEAT Protein Vaccine for Anthrax Disease. Infect Immun 2016; 84:3408-3422. [PMID: 27647868 DOI: 10.1128/iai.00755-16] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 09/10/2016] [Indexed: 01/05/2023] Open
Abstract
Bacillus anthracis is a sporulating Gram-positive bacterium that is the causative agent of anthrax and a potential weapon of bioterrorism. The U.S.-licensed anthrax vaccine is made from an incompletely characterized culture supernatant of a nonencapsulated, toxigenic strain (anthrax vaccine absorbed [AVA]) whose primary protective component is thought to be protective antigen (PA). AVA is effective in protecting animals and elicits toxin-neutralizing antibodies in humans, but enthusiasm is dampened by its undefined composition, multishot regimen, recommended boosters, and potential for adverse reactions. Improving next-generation anthrax vaccines is important to safeguard citizens and the military. Here, we report that vaccination with recombinant forms of a conserved domain (near-iron transporter [NEAT]), common in Gram-positive pathogens, elicits protection in a murine model of B. anthracis infection. Protection was observed with both Freund's and alum adjuvants, given subcutaneously and intramuscularly, respectively, with a mixed composite of NEATs. Protection correlated with an antibody response against the NEAT domains and a decrease in the numbers of bacteria in major organs. Anti-NEAT antibodies promote opsonophagocytosis of bacilli by alveolar macrophages. To guide the development of inactive and safe NEAT antigens, we also report the crystal structure of one of the NEAT domains (Hal) and identify critical residues mediating its heme-binding and acquisition activity. These results indicate that we should consider NEAT proteins in the development of an improved antianthrax vaccine.
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Chen J, Son HN, Hill JJ, Srinivasan S, Su FY, Stayton PS, Convertine AJ, Ratner DM. Nanostructured glycopolymer augmented liposomes to elucidate carbohydrate-mediated targeting. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2016; 12:2031-2041. [DOI: 10.1016/j.nano.2016.05.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 04/15/2016] [Accepted: 05/02/2016] [Indexed: 12/20/2022]
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Le Gars M, Haustant M, Klezovich-Bénard M, Paget C, Trottein F, Goossens PL, Tournier JN. Mechanisms of Invariant NKT Cell Activity in Restraining Bacillus anthracis Systemic Dissemination. THE JOURNAL OF IMMUNOLOGY 2016; 197:3225-3232. [PMID: 27605012 DOI: 10.4049/jimmunol.1600830] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 08/12/2016] [Indexed: 12/31/2022]
Abstract
Exogenous activation of invariant NKT (iNKT) cells by the superagonist α-galactosylceramide (α-GalCer) can protect against cancer, autoimmune diseases, and infections. In the current study, we investigated the effect of α-GalCer against Bacillus anthracis infection, the agent of anthrax. Using an experimental model of s.c. B. anthracis infection (an encapsulated nontoxigenic strain), we show that concomitant administration of α-GalCer delayed B. anthracis systemic dissemination and prolonged mouse survival. Depletion of subcapsular sinus CD169-positive macrophages by clodronate-containing liposome was associated with a lack of iNKT cell activation in the draining lymph nodes (dLNs) and prevented the protective effect of α-GalCer on bacterial dissemination out of the dLNs. Production of IFN-γ triggered chemokine (C-C motif) ligand 3 synthesis and recruitment of neutrophils in the dLNs, leading to the restraint of B. anthracis dissemination. Our data highlight a novel immunological pathway leading to the control of B. anthracis infection, a finding that might lead to improved therapeutics based on iNKT cells.
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Affiliation(s)
- Mathieu Le Gars
- Pathogénie des Toxi-Infections Bactériennes, Département de Microbiologie, Institut Pasteur, 75724 Paris, France;
| | - Michel Haustant
- Pathogénie des Toxi-Infections Bactériennes, Département de Microbiologie, Institut Pasteur, 75724 Paris, France
| | - Maria Klezovich-Bénard
- Pathogénie des Toxi-Infections Bactériennes, Département de Microbiologie, Institut Pasteur, 75724 Paris, France
| | - Christophe Paget
- Centre d'Infection et d'Immunité de Lille, INSERM U1019, CNRS UMR 8204, Universitaire de Lille, Centre Hospitalier Régional Universitaire de Lille-Institut Pasteur de Lille, 59000 Lille, France
| | - François Trottein
- Centre d'Infection et d'Immunité de Lille, INSERM U1019, CNRS UMR 8204, Universitaire de Lille, Centre Hospitalier Régional Universitaire de Lille-Institut Pasteur de Lille, 59000 Lille, France
| | - Pierre L Goossens
- Pathogénie des Toxi-Infections Bactériennes, Département de Microbiologie, Institut Pasteur, 75724 Paris, France
| | - Jean-Nicolas Tournier
- Pathogénie des Toxi-Infections Bactériennes, Département de Microbiologie, Institut Pasteur, 75724 Paris, France.,Unité Interactions Hôte-Agents Pathogènes, Institut de Recherche Biomédicale des Armées, 91223 Brétigny-sur-Orge, France; and.,Ecole du Val-de-Grâce, 75005 Paris, France
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The Exosporium Layer of Bacterial Spores: a Connection to the Environment and the Infected Host. Microbiol Mol Biol Rev 2016; 79:437-57. [PMID: 26512126 DOI: 10.1128/mmbr.00050-15] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Much of what we know regarding bacterial spore structure and function has been learned from studies of the genetically well-characterized bacterium Bacillus subtilis. Molecular aspects of spore structure, assembly, and function are well defined. However, certain bacteria produce spores with an outer spore layer, the exosporium, which is not present on B. subtilis spores. Our understanding of the composition and biological functions of the exosporium layer is much more limited than that of other aspects of the spore. Because the bacterial spore surface is important for the spore's interactions with the environment, as well as being the site of interaction of the spore with the host's innate immune system in the case of spore-forming bacterial pathogens, the exosporium is worthy of continued investigation. Recent exosporium studies have focused largely on members of the Bacillus cereus family, principally Bacillus anthracis and Bacillus cereus. Our understanding of the composition of the exosporium, the pathway of its assembly, and its role in spore biology is now coming into sharper focus. This review expands on a 2007 review of spore surface layers which provided an excellent conceptual framework of exosporium structure and function (A. O. Henriques and C. P. Moran, Jr., Annu Rev Microbiol 61:555-588, 2007, http://dx.doi.org/10.1146/annurev.micro.61.080706.093224). That review began a process of considering outer spore layers as an integrated, multilayered structure rather than simply regarding the outer spore components as independent parts.
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Animal Models for the Pathogenesis, Treatment, and Prevention of Infection by Bacillus anthracis. Microbiol Spectr 2016; 3:TBS-0001-2012. [PMID: 26104551 DOI: 10.1128/microbiolspec.tbs-0001-2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
This article reviews the characteristics of the major animal models utilized for studies on Bacillus anthracis and highlights their contributions to understanding the pathogenesis and host responses to anthrax and its treatment and prevention. Advantages and drawbacks associated with each model, to include the major models (murine, guinea pig, rabbit, nonhuman primate, and rat), and other less frequently utilized models, are discussed. Although the three principal forms of anthrax are addressed, the main focus of this review is on models for inhalational anthrax. The selection of an animal model for study is often not straightforward and is dependent on the specific aims of the research or test. No single animal species provides complete equivalence to humans; however, each species, when used appropriately, can contribute to a more complete understanding of anthrax and its etiologic agent.
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do Vale A, Cabanes D, Sousa S. Bacterial Toxins as Pathogen Weapons Against Phagocytes. Front Microbiol 2016; 7:42. [PMID: 26870008 PMCID: PMC4734073 DOI: 10.3389/fmicb.2016.00042] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/11/2016] [Indexed: 12/31/2022] Open
Abstract
Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favor microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response. In this review we will focus on bacterial toxins that act from the extracellular milieu and hinder the function of macrophages and neutrophils. In particular, we will concentrate on toxins from Gram-positive and Gram-negative bacteria that manipulate cell signaling or induce cell death by either imposing direct damage to the host cells cytoplasmic membrane or enzymatically modifying key eukaryotic targets. Outcomes regarding pathogen dissemination, host damage and disease progression will be discussed.
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Affiliation(s)
- Ana do Vale
- Host Interaction and Response, Instituto de Investigação e Inovação em Saúde, Universidade do PortoPorto, Portugal; Group of Fish Immunology and Vaccinology, Instituto de Biologia Molecular e Celular, Universidade do PortoPorto, Portugal
| | - Didier Cabanes
- Host Interaction and Response, Instituto de Investigação e Inovação em Saúde, Universidade do PortoPorto, Portugal; Group of Molecular Microbiology, Instituto de Biologia Molecular e Celular, Universidade do PortoPorto, Portugal
| | - Sandra Sousa
- Host Interaction and Response, Instituto de Investigação e Inovação em Saúde, Universidade do PortoPorto, Portugal; Group of Molecular Microbiology, Instituto de Biologia Molecular e Celular, Universidade do PortoPorto, Portugal
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Goossens PL, Tournier JN. Crossing of the epithelial barriers by Bacillus anthracis: the Known and the Unknown. Front Microbiol 2015; 6:1122. [PMID: 26500645 PMCID: PMC4598578 DOI: 10.3389/fmicb.2015.01122] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 09/28/2015] [Indexed: 12/15/2022] Open
Abstract
Anthrax, caused by Bacillus anthracis, a Gram-positive spore-forming bacterium, is initiated by the entry of spores into the host body. There are three types of human infection: cutaneous, inhalational, and gastrointestinal. For each form, B. anthracis spores need to cross the cutaneous, respiratory or digestive epithelial barriers, respectively, as a first obligate step to establish infection. Anthrax is a toxi-infection: an association of toxemia and rapidly spreading infection progressing to septicemia. The pathogenicity of Bacillus anthracis mainly depends on two toxins and a capsule. The capsule protects bacilli from the immune system, thus promoting systemic dissemination. The toxins alter host cell signaling, thereby paralyzing the immune response of the host and perturbing the endocrine and endothelial systems. In this review, we will mainly focus on the events and mechanisms leading to crossing of the respiratory epithelial barrier, as the majority of studies have addressed inhalational infection. We will discuss the critical gaps of knowledge that need to be addressed to gain a comprehensive view of the initial steps of inhalational anthrax. We will then discuss the few data available on B. anthracis crossing the cutaneous and digestive epithelia.
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Affiliation(s)
- Pierre L Goossens
- Pathogénie des Toxi-Infections Bactériennes, Institut Pasteur , Paris, France
| | - Jean-Nicolas Tournier
- Pathogénie des Toxi-Infections Bactériennes, Institut Pasteur , Paris, France ; Unité Interactions Hôte-Agents Pathogènes, Institut de Recherche Biomédicale des Armées , Brétigny-sur-Orge, France ; Ecole du Val-de-Grâce , Paris, France
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Global metabolomic analysis of a mammalian host infected with Bacillus anthracis. Infect Immun 2015; 83:4811-25. [PMID: 26438791 DOI: 10.1128/iai.00947-15] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 09/23/2015] [Indexed: 12/21/2022] Open
Abstract
Whereas DNA provides the information to design life and proteins provide the materials to construct it, the metabolome can be viewed as the physiology that powers it. As such, metabolomics, the field charged with the study of the dynamic small-molecule fluctuations that occur in response to changing biology, is now being used to study the basis of disease. Here, we describe a comprehensive metabolomic analysis of a systemic bacterial infection using Bacillus anthracis, the etiological agent of anthrax disease, as the model pathogen. An organ and blood analysis identified approximately 400 metabolites, including several key classes of lipids involved in inflammation, as being suppressed by B. anthracis. Metabolite changes were detected as early as 1 day postinfection, well before the onset of disease or the spread of bacteria to organs, which testifies to the sensitivity of this methodology. Functional studies using pharmacologic inhibition of host phospholipases support the idea of a role of these key enzymes and lipid mediators in host survival during anthrax disease. Finally, the results are integrated to provide a comprehensive picture of how B. anthracis alters host physiology. Collectively, the results of this study provide a blueprint for using metabolomics as a platform to identify and study novel host-pathogen interactions that shape the outcome of an infection.
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Cote CK, Welkos SL. Anthrax Toxins in Context of Bacillus anthracis Spores and Spore Germination. Toxins (Basel) 2015; 7:3167-78. [PMID: 26287244 PMCID: PMC4549744 DOI: 10.3390/toxins7083167] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 08/08/2015] [Accepted: 08/11/2015] [Indexed: 11/18/2022] Open
Abstract
The interaction of anthrax toxin or toxin components with B. anthracis spores has been demonstrated. Germinating spores can produce significant amounts of toxin components very soon after the initiation of germination. In this review, we will summarize the work performed that has led to our understanding of toxin and spore interactions and discuss the complexities associated with these interactions.
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Affiliation(s)
- Christopher K Cote
- United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Bacteriology Division, 1425 Porter Street, Fort Detrick, Frederick, MD 21702-5011, USA.
| | - Susan L Welkos
- United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Bacteriology Division, 1425 Porter Street, Fort Detrick, Frederick, MD 21702-5011, USA.
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Sheldon JR, Heinrichs DE. Recent developments in understanding the iron acquisition strategies of gram positive pathogens. FEMS Microbiol Rev 2015; 39:592-630. [DOI: 10.1093/femsre/fuv009] [Citation(s) in RCA: 166] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2015] [Indexed: 12/26/2022] Open
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Goel AK. Anthrax: A disease of biowarfare and public health importance. World J Clin Cases 2015; 3:20-33. [PMID: 25610847 PMCID: PMC4295216 DOI: 10.12998/wjcc.v3.i1.20] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 10/23/2014] [Accepted: 10/31/2014] [Indexed: 02/05/2023] Open
Abstract
Bioterrorism has received a lot of attention in the first decade of this century. Biological agents are considered attractive weapons for bioterrorism as these are easy to obtain, comparatively inexpensive to produce and exhibit widespread fear and panic than the actual potential of physical damage. Bacillus anthracis (B. anthracis), the etiologic agent of anthrax is a Gram positive, spore forming, non-motile bacterium. This is supposed to be one of the most potent BW agents because its spores are extremely resistant to natural conditions and can survive for several decades in the environment. B. anthracis spores enter the body through skin lesion (cutaneous anthrax), lungs (pulmonary anthrax), or gastrointestinal route (gastrointestinal anthrax) and germinate, giving rise to the vegetative form. Anthrax is a concern of public health also in many countries where agriculture is the main source of income including India. Anthrax has been associated with human history for a very long time and regained its popularity after Sept 2001 incidence in United States. The present review article describes the history, biology, life cycle, pathogenicity, virulence, epidemiology and potential of B. anthracis as biological weapon.
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Khavrutskii IV, Legler PM, Friedlander AM, Wallqvist A. A reaction path study of the catalysis and inhibition of the Bacillus anthracis CapD γ-glutamyl transpeptidase. Biochemistry 2014; 53:6954-67. [PMID: 25334088 DOI: 10.1021/bi500623c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The CapD enzyme of Bacillus anthracis is a γ-glutamyl transpeptidase from the N-terminal nucleophile hydrolase superfamily that covalently anchors the poly-γ-D-glutamic acid (pDGA) capsule to the peptidoglycan. The capsule hinders phagocytosis of B. anthracis by host cells and is essential for virulence. The role CapD plays in capsule anchoring and remodeling makes the enzyme a promising target for anthrax medical countermeasures. Although the structure of CapD is known, and a covalent inhibitor, capsidin, has been identified, the mechanisms of CapD catalysis and inhibition are poorly understood. Here, we used a computational approach to map out the reaction steps involved in CapD catalysis and inhibition. We found that the rate-limiting step of either CapD catalysis or inhibition was a concerted asynchronous formation of the tetrahedral intermediate with a barrier of 22-23 kcal/mol. However, the mechanisms of these reactions differed for the two amides. The formation of the tetrahedral intermediate with pDGA was substrate-assisted with two proton transfers. In contrast, capsidin formed the tetrahedral intermediate in a conventional way with one proton transfer. Interestingly, capsidin coupled a conformational change in the catalytic residue of the tetrahedral intermediate to stretching of the scissile amide bond. Furthermore, capsidin took advantage of iminol-amide tautomerism of its diacetamide moiety to convert the tetrahedral intermediate to the acetylated CapD. As evidence of the promiscuous nature of CapD, the enzyme cleaved the amide bond of capsidin by attacking it on the opposite side compared to pDGA.
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Affiliation(s)
- Ilja V Khavrutskii
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command , Fort Detrick, Maryland 21702, United States
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Hutt JA, Lovchik JA, Drysdale M, Sherwood RL, Brasel T, Lipscomb MF, Lyons CR. Lethal factor, but not edema factor, is required to cause fatal anthrax in cynomolgus macaques after pulmonary spore challenge. THE AMERICAN JOURNAL OF PATHOLOGY 2014; 184:3205-16. [PMID: 25285720 DOI: 10.1016/j.ajpath.2014.08.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 08/01/2014] [Accepted: 08/21/2014] [Indexed: 11/27/2022]
Abstract
Inhalational anthrax is caused by inhalation of Bacillus anthracis spores. The ability of B. anthracis to cause anthrax is attributed to the plasmid-encoded A/B-type toxins, edema toxin (edema factor and protective antigen) and lethal toxin (lethal factor and protective antigen), and a poly-d-glutamic acid capsule. To better understand the contribution of these toxins to the disease pathophysiology in vivo, we used B. anthracis Ames strain and isogenic toxin deletion mutants derived from the Ames strain to examine the role of lethal toxin and edema toxin after pulmonary spore challenge of cynomolgus macaques. Lethal toxin, but not edema toxin, was required to induce sustained bacteremia and death after pulmonary challenge with spores delivered via bronchoscopy. After intravenous challenge with bacilli to model the systemic phase of infection, lethal toxin contributed to bacterial proliferation and subsequent host death to a greater extent than edema toxin. Deletion of protective antigen resulted in greater loss of virulence after intravenous challenge with bacilli than deletion of lethal toxin or edema toxin alone. These findings are consistent with the ability of anti-protective antigen antibodies to prevent anthrax and suggest that lethal factor is the dominant toxin that contributes to the escape of significant numbers of bacilli from the thoracic cavity to cause anthrax after inhalation challenge with spores.
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Affiliation(s)
- Julie A Hutt
- Lovelace Respiratory Research Institute, Albuquerque, New Mexico; Center for Infectious Disease & Immunity, University of New Mexico Health Science Center, Albuquerque, New Mexico.
| | - Julie A Lovchik
- Center for Infectious Disease & Immunity, University of New Mexico Health Science Center, Albuquerque, New Mexico; Department of Internal Medicine, University of New Mexico Health Science Center, Albuquerque, New Mexico
| | - Melissa Drysdale
- Center for Infectious Disease & Immunity, University of New Mexico Health Science Center, Albuquerque, New Mexico; Department of Internal Medicine, University of New Mexico Health Science Center, Albuquerque, New Mexico
| | | | - Trevor Brasel
- Lovelace Respiratory Research Institute, Albuquerque, New Mexico
| | - Mary F Lipscomb
- Department of Pathology, University of New Mexico Health Science Center, Albuquerque, New Mexico
| | - C Rick Lyons
- Center for Infectious Disease & Immunity, University of New Mexico Health Science Center, Albuquerque, New Mexico; Department of Internal Medicine, University of New Mexico Health Science Center, Albuquerque, New Mexico
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Abstract
Reactive oxygen species (ROS) are deadly weapons used by phagocytes and other cell types, such as lung epithelial cells, against pathogens. ROS can kill pathogens directly by causing oxidative damage to biocompounds or indirectly by stimulating pathogen elimination by various nonoxidative mechanisms, including pattern recognition receptors signaling, autophagy, neutrophil extracellular trap formation, and T-lymphocyte responses. Thus, one should expect that the inhibition of ROS production promote infection. Increasing evidences support that in certain particular infections, antioxidants decrease and prooxidants increase pathogen burden. In this study, we review the classic infections that are controlled by ROS and the cases in which ROS appear as promoters of infection, challenging the paradigm. We discuss the possible mechanisms by which ROS could promote particular infections. These mechanisms are still not completely clear but include the metabolic effects of ROS on pathogen physiology, ROS-induced damage to the immune system, and ROS-induced activation of immune defense mechanisms that are subsequently hijacked by particular pathogens to act against more effective microbicidal mechanisms of the immune system. The effective use of antioxidants as therapeutic agents against certain infections is a realistic possibility that is beginning to be applied against viruses.
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Affiliation(s)
- Claudia N Paiva
- Departamento de Imunologia, Instituto de Microbiologia , CCS Bloco D, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
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Alvarez Z, Abel-Santos E. Potential use of inhibitors of bacteria spore germination in the prophylactic treatment of anthrax andClostridium difficile-associated disease. Expert Rev Anti Infect Ther 2014; 5:783-92. [PMID: 17914913 DOI: 10.1586/14787210.5.5.783] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Spore germination is the first step in establishing Bacillus and Clostridium infections. Germination is triggered by the binding of small molecules by the resting spore. Subsequently, the activated spore secretes dipicolinic acid and calcium, the spore core is rehydrated and spore structures are degraded. Inhibition of any of the germination-related events will prevent development to the vegetative stage. Inhibition of spore germination has been studied intensively in the prevention of food spoilage. In this perspective, we propose that similar approaches could be used in the prophylactic control of Bacillus anthracis and Clostridium difficile infections. Inhibition of B. anthracis spore germination could protect military and first-line emergency personnel at high risk for anthrax exposure. Inhibition of C. difficile could prevent human C. difficile-associated disease during antibiotic treatment of immunocompromised patients.
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Affiliation(s)
- Zadkiel Alvarez
- Department of Chemistry, University of Nevada, 4505 Maryland Parkway, Campus Box 4003, Las Vegas, NV 89154, USA.
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Gutting B. Deterministic models of inhalational anthrax in New Zealand white rabbits. Biosecur Bioterror 2014; 12:29-41. [PMID: 24527843 PMCID: PMC3934436 DOI: 10.1089/bsp.2013.0067] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Accepted: 12/09/2013] [Indexed: 11/12/2022]
Abstract
Computational models describing bacterial kinetics were developed for inhalational anthrax in New Zealand white (NZW) rabbits following inhalation of Ames strain B. anthracis. The data used to parameterize the models included bacterial numbers in the airways, lung tissue, draining lymph nodes, and blood. Initial bacterial numbers were deposited spore dose. The first model was a single exponential ordinary differential equation (ODE) with 3 rate parameters that described mucociliated (physical) clearance, immune clearance (bacterial killing), and bacterial growth. At 36 hours postexposure, the ODE model predicted 1.7×10⁷ bacteria in the rabbit, which agreed well with data from actual experiments (4.0×10⁷ bacteria at 36 hours). Next, building on the single ODE model, a physiological-based biokinetic (PBBK) compartmentalized model was developed in which 1 physiological compartment was the lumen of the airways and the other was the rabbit body (lung tissue, lymph nodes, blood). The 2 compartments were connected with a parameter describing transport of bacteria from the airways into the body. The PBBK model predicted 4.9×10⁷ bacteria in the body at 36 hours, and by 45 hours the model showed all clearance mechanisms were saturated, suggesting the rabbit would quickly succumb to the infection. As with the ODE model, the PBBK model results agreed well with laboratory observations. These data are discussed along with the need for and potential application of the models in risk assessment, drug development, and as a general aid to the experimentalist studying inhalational anthrax.
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Affiliation(s)
- Bradford Gutting
- Bradford Gutting, PhD, is a Toxicologist, Naval Surface Warfare Center Dahlgren Division (NSWCDD) , Dahlgren, Virginia
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The two CcdA proteins of Bacillus anthracis differentially affect virulence gene expression and sporulation. J Bacteriol 2013; 195:5242-9. [PMID: 24056109 DOI: 10.1128/jb.00917-13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The cytochrome c maturation system influences the expression of virulence factors in Bacillus anthracis. B. anthracis carries two copies of the ccdA gene, encoding predicted thiol-disulfide oxidoreductases that contribute to cytochrome c maturation, while the closely related organism Bacillus subtilis carries only one copy of ccdA. To investigate the roles of the two ccdA gene copies in B. anthracis, strains were constructed without each ccdA gene, and one strain was constructed without both copies simultaneously. Loss of both ccdA genes results in a reduction of cytochrome c production, an increase in virulence factor expression, and a reduction in sporulation efficiency. Complementation and expression analyses indicate that ccdA2 encodes the primary CcdA in B. anthracis, active in all three pathways. While CcdA1 retains activity in cytochrome c maturation and virulence control, it has completely lost its activity in the sporulation pathway. In support of this finding, expression of ccdA1 is strongly reduced when cells are grown under sporulation-inducing conditions. When the activities of CcdA1 and CcdA2 were analyzed in B. subtilis, neither protein retained activity in cytochrome c maturation, but CcdA2 could still function in sporulation. These observations reveal the complexities of thiol-disulfide oxidoreductase function in pathways relevant to virulence and physiology.
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Bacillus anthracis has two independent bottlenecks that are dependent on the portal of entry in an intranasal model of inhalational infection. Infect Immun 2013; 81:4408-20. [PMID: 24042112 DOI: 10.1128/iai.00484-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Bacillus anthracis can cause inhalational anthrax. Murine inhalational B. anthracis infections have two portals of entry, the nasal mucosa-associated lymphoid tissue (NALT) and the lumen of the lungs. Analysis of the dissemination from these sites is hindered because infections are asynchronous and asymptomatic until the hosts near death. To further understand and compare how B. anthracis disseminates from these two different environments, clonal analysis was employed using a library of equally virulent DNA-tagged clones of a luminescent Sterne strain. Luminescence was used to determine the origin of the infection and monitor the dissemination in vivo. The number of clones and their proportions in the portals of entry, lymph nodes draining the portals, and kidneys were analyzed. Clonal analysis indicated a bottleneck for both portals of entry, yet the extent and location of the reduction in represented clones differed between the routes. In NALT-based infections, all clones were found to germinate in the NALT, but they underwent a bottleneck as the infection spread to the cervical lymph node. However, lung-based infections underwent a bottleneck in a focal region of growth within the lung lumen and did not need to spread through the mediastinal lymph nodes to cause a systemic infection. Further, the average number of clones found in the kidney and the rate at which genetic drift was affecting the disseminated populations were significantly higher in lung-based infections. Collectively, the data suggested that differences in the host environment alter dissemination of B. anthracis depending on the site of initial colonization and growth.
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Wong CHY, Jenne CN, Petri B, Chrobok NL, Kubes P. Nucleation of platelets with blood-borne pathogens on Kupffer cells precedes other innate immunity and contributes to bacterial clearance. Nat Immunol 2013; 14:785-92. [PMID: 23770641 PMCID: PMC4972575 DOI: 10.1038/ni.2631] [Citation(s) in RCA: 260] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 04/25/2013] [Indexed: 12/13/2022]
Abstract
Using intravital imaging of the liver, we unveil a collaborative role for platelets with Kupffer cells (KCs) in eradicating bloodborne bacterial infections. Under basal conditions, platelets via glycoprotein Ib (GPIb) formed transient “touch-and-go” interactions with von Willebrand factor (vWF) constitutively expressed on KCs. Bacteria, such as Bacillus cereus and Methicillin-resistant Staphylococcus aureus (MRSA), were rapidly caught by KCs and triggered platelets to switch from “touch-and-go” to sustained GPIIb-mediated adhesion on the KC surface to encase the bacterium. Infected GpIbα−/− mice demonstrated increased endothelial and KC damage, leading to increased fluid leakage, significant polycythemia and rapid mortality. This study identifies a novel surveillance mechanism of intravascular macrophage by platelets that rapidly converts to a critical host response against bloodborne bacteria.
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Affiliation(s)
- Connie H Y Wong
- Calvin, Phoebe and Joan Snyder Institute for Chronic Diseases, Department of Physiology and Pharmacology, University of Calgary, Alberta, Canada
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Jenkins SA, Xu Y. Characterization of Bacillus anthracis persistence in vivo. PLoS One 2013; 8:e66177. [PMID: 23750280 PMCID: PMC3672131 DOI: 10.1371/journal.pone.0066177] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 05/07/2013] [Indexed: 02/07/2023] Open
Abstract
Pulmonary exposure to Bacillus anthracis spores initiates inhalational anthrax, a life-threatening infection. It is known that dormant spores can be recovered from the lungs of infected animals months after the initial spore exposure. Consequently, a 60-day course antibiotic treatment is recommended for exposed individuals. However, there has been little information regarding details or mechanisms of spore persistence in vivo. In this study, we investigated spore persistence in a mouse model. The results indicated that weeks after intranasal inoculation with B. anthracis spores, substantial amounts of spores could be recovered from the mouse lung. Moreover, spores of B. anthracis were significantly better at persisting in the lung than spores of a non-pathogenic Bacillus subtilis strain. The majority of B. anthracis spores in the lung were tightly associated with the lung tissue, as they could not be readily removed by lavage. Immunofluorescence staining of lung sections showed that spores associated with the alveolar and airway epithelium. Confocal analysis indicated that some of the spores were inside epithelial cells. This was further confirmed by differential immunofluorescence staining of lung cells harvested from the infected lungs, suggesting that association with lung epithelial cells may provide an advantage to spore persistence in the lung. There was no or very mild inflammation in the infected lungs. Furthermore, spores were present in the lung tissue as single spores rather than in clusters. We also showed that the anthrax toxins did not play a role in persistence. Together, the results suggest that B. anthracis spores have special properties that promote their persistence in the lung, and that there may be multiple mechanisms contributing to spore persistence.
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Affiliation(s)
- Sarah A. Jenkins
- Center for Infectious and Inflammatory Diseases, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas, United States of America
| | - Yi Xu
- Center for Infectious and Inflammatory Diseases, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas, United States of America
- * E-mail:
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Alvarado I, Phui A, Elekonich MM, Abel-Santos E. Requirements for in vitro germination of Paenibacillus larvae spores. J Bacteriol 2013; 195:1005-11. [PMID: 23264573 PMCID: PMC3571325 DOI: 10.1128/jb.01958-12] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 12/12/2012] [Indexed: 01/03/2023] Open
Abstract
Paenibacillus larvae is the causative agent of American foulbrood (AFB), a disease affecting honey bee larvae. First- and second-instar larvae become infected when they ingest food contaminated with P. larvae spores. The spores then germinate into vegetative cells that proliferate in the midgut of the honey bee. Although AFB affects honey bees only in the larval stage, P. larvae spores can be distributed throughout the hive. Because spore germination is critical for AFB establishment, we analyzed the requirements for P. larvae spore germination in vitro. We found that P. larvae spores germinated only in response to l-tyrosine plus uric acid under physiologic pH and temperature conditions. This suggests that the simultaneous presence of these signals is necessary for spore germination in vivo. Furthermore, the germination profiles of environmentally derived spores were identical to those of spores from a biochemically typed strain. Because l-tyrosine and uric acid are the only required germinants in vitro, we screened amino acid and purine analogs for their ability to act as antagonists of P. larvae spore germination. Indole and phenol, the side chains of tyrosine and tryptophan, strongly inhibited P. larvae spore germination. Methylation of the N-1 (but not the C-3) position of indole eliminated its ability to inhibit germination. Identification of the activators and inhibitors of P. larvae spore germination provides a basis for developing new tools to control AFB.
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Affiliation(s)
| | - Andy Phui
- Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada, USA
| | | | - Ernesto Abel-Santos
- Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada, USA
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Sinha K, Bhatnagar R. Recombinant GroEL enhances protective antigen-mediated protection against Bacillus anthracis spore challenge. Med Microbiol Immunol 2012; 202:153-65. [PMID: 23263010 DOI: 10.1007/s00430-012-0280-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Accepted: 11/27/2012] [Indexed: 11/27/2022]
Abstract
The fatal inhalation infection caused by Bacillus anthracis results from a complex pathogenic cycle involving release of toxins by bacteria that germinate from spores. Currently available vaccines against anthrax consist of protective antigen (PA), one of the anthrax toxin components. However, these PA-based vaccines are only partially protective against spore challenge in mice. This shows that exclusive elicitation of high anti-PA titer does not directly correlate with protection. Here, we demonstrate that inclusion of GroEL of B. anthracis with PA elicits enhanced protection against anthrax spore challenge in mice. GroEL was included as it has been reported to be present both on the exosporium and in the secretome in addition to the cell surface of B. anthracis. It has also been found protective against other pathogens. In the present study, immunization with GroEL alone was also potent enough to induce high humoral and cell-mediated response and significantly prolonged the mean time to death in spore-challenged mice. As a surface antigen, opsonization of spores with anti-GroEL IgG showed increased uptake of treated spores and therefore accelerated rate of spore destruction by phagocytic cells leading to the protection of mice. We found that GroEL was able to enhance nitric oxide release from lymphocytes and also reduce bacterial load from the organs, probably through the activation of macrophages and over-expression of certain innate immunity receptors. Therefore, the present study emphasizes that GroEL is an effective immunomodulator against B. anthracis infection.
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Affiliation(s)
- Kanchan Sinha
- Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.
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Corre JP, Piris-Gimenez A, Moya-Nilges M, Jouvion G, Fouet A, Glomski IJ, Mock M, Sirard JC, Goossens PL. In vivo germination of Bacillus anthracis spores during murine cutaneous infection. J Infect Dis 2012; 207:450-7. [PMID: 23148288 DOI: 10.1093/infdis/jis686] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Germination is a key step for successful Bacillus anthracis colonization and systemic dissemination. Few data are available on spore germination in vivo, and the necessity of spore and host cell interactions to initiate germination is unclear. METHODS To investigate the early interactions between B. anthracis spores and cutaneous tissue, spores were inoculated in an intraperitoneal cell-free device in guinea pigs or into the pinna of mice. Germination and bacterial growth were analyzed through colony-forming unit enumeration and electron microscopy. RESULTS In the guinea pig model, germination occurred in vivo in the absence of cell contact. Similarly, in the mouse ear, germination started within 15 minutes after inoculation, and germinating spores were found in the absence of surrounding cells. Germination was not observed in macrophage-rich draining lymph nodes, liver, and spleen. Edema and lethal toxin production were not required for germination, as a toxin-deficient strain was as effective as a Sterne-like strain. B. anthracis growth was locally controlled for 6 hours. CONCLUSIONS Spore germination involving no cell interactions can occur in vivo, suggesting that diffusible germinants or other signals appear sufficient. Different host tissues display drastic differences in germination-triggering capacity. Initial control of bacterial growth suggests a therapeutic means to exploit host innate defenses to hinder B. anthracis colonization.
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Affiliation(s)
- Jean-Philippe Corre
- Toxines et Pathogénie Bactériennes, Pathogénie des Toxi-Infections Bactériennes, Centre National de la Recherche Scientifique, Paris, France
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Germination and amplification of anthrax spores by soil-dwelling amoebas. Appl Environ Microbiol 2012; 78:8075-81. [PMID: 22983962 DOI: 10.1128/aem.02034-12] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
While anthrax is typically associated with bioterrorism, in many parts of the world the anthrax bacillus (Bacillus anthracis) is endemic in soils, where it causes sporadic disease in livestock. These soils are typically rich in organic matter and calcium that promote survival of resilient B. anthracis spores. Outbreaks of anthrax tend to occur in warm weather following rains that are believed to concentrate spores in low-lying areas where runoff collects. It has been concluded that elevated spore concentrations are not the result of vegetative growth as B. anthracis competes poorly against indigenous bacteria. Here, we test an alternative hypothesis in which amoebas, common in moist soils and pools of standing water, serve as amplifiers of B. anthracis spores by enabling germination and intracellular multiplication. Under simulated environmental conditions, we show that B. anthracis germinates and multiplies within Acanthamoeba castellanii. The growth kinetics of a fully virulent B. anthracis Ames strain (containing both the pX01 and pX02 virulence plasmids) and vaccine strain Sterne (containing only pX01) inoculated as spores in coculture with A. castellanii showed a nearly 50-fold increase in spore numbers after 72 h. In contrast, the plasmidless strain 9131 showed little growth, demonstrating that plasmid pX01 is essential for growth within A. castellanii. Electron and time-lapse fluorescence microscopy revealed that spores germinate within amoebal phagosomes, vegetative bacilli undergo multiplication, and, following demise of the amoebas, bacilli sporulate in the extracellular milieu. This analysis supports our hypothesis that amoebas contribute to the persistence and amplification of B. anthracis in natural environments.
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Paredes-Sabja D, Cofre-Araneda G, Brito-Silva C, Pizarro-Guajardo M, Sarker MR. Clostridium difficile spore-macrophage interactions: spore survival. PLoS One 2012; 7:e43635. [PMID: 22952726 PMCID: PMC3428350 DOI: 10.1371/journal.pone.0043635] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Accepted: 07/24/2012] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Clostridium difficile is the main cause of nosocomial infections including antibiotic associated diarrhea, pseudomembranous colitis and toxic megacolon. During the course of Clostridium difficile infections (CDI), C. difficile undergoes sporulation and releases spores to the colonic environment. The elevated relapse rates of CDI suggest that C. difficile spores has a mechanism(s) to efficiently persist in the host colonic environment. METHODOLOGY/PRINCIPAL FINDINGS In this work, we provide evidence that C. difficile spores are well suited to survive the host's innate immune system. Electron microscopy results show that C. difficile spores are recognized by discrete patchy regions on the surface of macrophage Raw 264.7 cells, and phagocytosis was actin polymerization dependent. Fluorescence microscopy results show that >80% of Raw 264.7 cells had at least one C. difficile spore adhered, and that ∼60% of C. difficile spores were phagocytosed by Raw 264.7 cells. Strikingly, presence of complement decreased Raw 264.7 cells' ability to phagocytose C. difficile spores. Due to the ability of C. difficile spores to remain dormant inside Raw 264.7 cells, they were able to survive up to 72 h of macrophage infection. Interestingly, transmission electron micrographs showed interactions between the surface proteins of C. difficile spores and the phagosome membrane of Raw 264.7 cells. In addition, infection of Raw 264.7 cells with C. difficile spores for 48 h produced significant Raw 264.7 cell death as demonstrated by trypan blue assay, and nuclei staining by ethidium homodimer-1. CONCLUSIONS/SIGNIFICANCE These results demonstrate that despite efficient recognition and phagocytosis of C. difficile spores by Raw 264.7 cells, spores remain dormant and are able to survive and produce cytotoxic effects on Raw 264.7 cells.
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Affiliation(s)
- Daniel Paredes-Sabja
- Laboratorio de Mecanismos de Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile.
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43
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Bacillus anthracis factors for phagosomal escape. Toxins (Basel) 2012; 4:536-53. [PMID: 22852067 PMCID: PMC3407891 DOI: 10.3390/toxins4070536] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 06/21/2012] [Accepted: 07/02/2012] [Indexed: 12/27/2022] Open
Abstract
The mechanism of phagosome escape by intracellular pathogens is an important step in the infectious cycle. During the establishment of anthrax, Bacillus anthracis undergoes a transient intracellular phase in which spores are engulfed by local phagocytes. Spores germinate inside phagosomes and grow to vegetative bacilli, which emerge from their resident intracellular compartments, replicate and eventually exit from the plasma membrane. During germination, B. anthracis secretes multiple factors that can help its resistance to the phagocytes. Here the possible role of B. anthracis toxins, phospholipases, antioxidant enzymes and capsules in the phagosomal escape and survival, is analyzed and compared with that of factors of other microbial pathogens involved in the same type of process.
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44
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Abstract
Inhalational anthrax is caused by the sporulating bacterium Bacillus anthracis. A current model for progression in mammalian hosts includes inhalation of bacterial spores, phagocytosis of spores in the nasal mucosa-associated lymphoid tissue (NALT) and lungs by macrophages and dendritic cells, trafficking of phagocytes to draining lymph nodes, germination of spores and multiplication of vegetative bacteria in the NALT and lymph nodes, and dissemination of bacteria via the bloodstream to multiple organs. In previous studies, the kinetics of infection varied greatly among mice, leading us to hypothesize the existence of a bottleneck past which very few spores (perhaps only one) progress to allow the infection to proceed. To test this hypothesis, we engineered three strains of B. anthracis Sterne, each marked with a different fluorescent protein, enabling visual differentiation of strains grown on plates. Mice were infected with a mixture of the three strains, the infection was allowed to proceed, and the strains colonizing the organs were identified. Although the inoculum consisted of approximately equal numbers of each of the three strains, the distal organs were consistently colonized by a majority of only one of the three strains, with the dominant strain varying among animals. Such dominance of one strain over the other two was also found at early time points in the cervical lymph nodes but not in the mediastinal lymph nodes. These results support the existence of a bottleneck in the infectious process.
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45
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Abstract
Sampling of mucosal antigens regulates immune responses but may also promote dissemination of mucosal pathogens. Lung dendritic cells (LDCs) capture antigens and traffic them to lung-draining lymph nodes (LDLNs) dependent on the chemokine receptor CCR7 (chemokine (C-C motif) receptor 7). LDCs also capture lung pathogens such as Bacillus anthracis (BA). However, we show here that the initial traffic of BA spores from lungs to LDLNs is largely independent of LDCs and CCR7, occurring instead in association with B cells. BA spores rapidly bound B cells in lungs and cultured mouse and human B cells. Binding was independent of the B-cell receptor (BCR). B cells instilled in the lungs trafficked to LDLNs and BA spore traffic to LDLNs was impaired by B-cell deficiency. Depletion of B cells also delayed death of mice receiving a lethal BA infection. These results suggest that mucosal B cells traffic BA, and possibly other antigens, from lungs to LDLNs.
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46
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Gutting BW, Nichols TL, Channel SR, Gearhart JM, Andrews GA, Berger AE, Mackie RS, Watson BJ, Taft SC, Overheim KA, Sherwood RL. Inhalational anthrax (Ames aerosol) in naïve and vaccinated New Zealand rabbits: characterizing the spread of bacteria from lung deposition to bacteremia. Front Cell Infect Microbiol 2012; 2:87. [PMID: 22919678 PMCID: PMC3417635 DOI: 10.3389/fcimb.2012.00087] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 06/06/2012] [Indexed: 12/21/2022] Open
Abstract
There is a need to better understand inhalational anthrax in relevant animal models. This understanding could aid risk assessment, help define therapeutic windows, and provide a better understanding of disease. The aim here was to characterize and quantify bacterial deposition and dissemination in rabbits following exposure to single high aerosol dose (> 100 LD50) of Bacillus anthracis (Ames) spores immediately following exposure through 36 h. The primary goal of collecting the data was to support investigators in developing computational models of inhalational anthrax disease. Rabbits were vaccinated prior to exposure with the human vaccine (Anthrax Vaccine Adsorbed, AVA) or were sham-vaccinated, and were then exposed in pairs (one sham and one AVA) so disease kinetics could be characterized in equally-dosed hosts where one group is fully protected and is able to clear the infection (AVA-vaccinated), while the other is susceptible to disease, in which case the bacteria are able to escape containment and replicate uncontrolled (sham-vaccinated rabbits). Between 4–5% of the presented aerosol dose was retained in the lung of sham- and AVA-vaccinated rabbits as measured by dilution plate analysis of homogenized lung tissue or bronchoalveolar lavage (BAL) fluid. After 6 and 36 h, >80% and >96%, respectively, of the deposited spores were no longer detected in BAL, with no detectable difference between sham- or AVA-vaccinated rabbits. Thereafter, differences between the two groups became noticeable. In sham-vaccinated rabbits the bacteria were detected in the tracheobronchial lymph nodes (TBLN) 12 h post-exposure and in the circulation at 24 h, a time point which was also associated with dramatic increases in vegetative CFU in the lung tissue of some animals. In all sham-vaccinated rabbits, bacteria increased in both TBLN and blood through 36 h at which point in time some rabbits succumbed to disease. In contrast, AVA-vaccinated rabbits showed small numbers of CFU in TBLN between 24 and 36 h post-exposure with small numbers of bacteria in the circulation only at 24 h post-exposure. These results characterize and quantify disease progression in naïve rabbits following aerosol administration of Ames spores which may be useful in a number of different research applications, including developing quantitative models of infection for use in human inhalational anthrax risk assessment.
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Bann JG. Anthrax toxin protective antigen--insights into molecular switching from prepore to pore. Protein Sci 2012; 21:1-12. [PMID: 22095644 DOI: 10.1002/pro.752] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The protective antigen is a key component of the anthrax toxin, as it allows entry of the enzymatic components edema factor and lethal factor into the host cell, through the formation of a membrane spanning pore. This event is absolutely critical for the pathogenesis of anthrax, and although we have yet to understand the mechanism of pore formation, recent developments have provided key insights into how this process may occur. Based on the available data, a model is proposed for the kinetic steps for protective antigen conversion from prepore to pore. In this model, the driving force for pore formation is the formation of the phi (ϕ)-clamp, a region that forms a leak-free seal around the translocating polypeptide. Formation of the ϕ-clamp elicits movements within the prepore that provide steric freedom for the subsequent conformational changes required to form the membrane spanning pore.
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Affiliation(s)
- James G Bann
- Department of Chemistry, Wichita State University, Wichita, Kansas 67260-0051, USA.
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48
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Gu C, Jenkins SA, Xue Q, Xu Y. Activation of the classical complement pathway by Bacillus anthracis is the primary mechanism for spore phagocytosis and involves the spore surface protein BclA. THE JOURNAL OF IMMUNOLOGY 2012; 188:4421-31. [PMID: 22442442 DOI: 10.4049/jimmunol.1102092] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Interactions between spores of Bacillus anthracis and macrophages are critical for the development of anthrax infections, as spores are thought to use macrophages as vehicles to disseminate in the host. In this study, we report a novel mechanism for phagocytosis of B. anthracis spores. Murine macrophage-like cell line RAW264.7, bone marrow-derived macrophages, and primary peritoneal macrophages from mice were used. The results indicated that activation of the classical complement pathway (CCP) was a primary mechanism for spore phagocytosis. Phagocytosis was significantly reduced in the absence of C1q or C3. C3 fragments were found deposited on the spore surface, and the deposition was dependent on C1q and Ca(2+). C1q recruitment to the spore surface was mediated by the spore surface protein BclA, as recombinant BclA bound directly and specifically to C1q and inhibited C1q binding to spores in a dose-dependent manner. C1q binding to spores lacking BclA (ΔbclA) was also significantly reduced compared with wild-type spores. In addition, deposition of both C3 and C4 as well as phagocytosis of spores were significantly reduced when BclA was absent, but were not reduced in the absence of IgG, suggesting that BclA, but not IgG, is important in these processes. Taken together, these results support a model in which spores actively engage CCP primarily through BclA interaction with C1q, leading to CCP activation and opsonophagocytosis of spores in an IgG-independent manner. These findings are likely to have significant implications on B. anthracis pathogenesis and microbial manipulation of complement.
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Affiliation(s)
- Chunfang Gu
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX 77030, USA
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Dixon SD, Janes BK, Bourgis A, Carlson PE, Hanna PC. Multiple ABC transporters are involved in the acquisition of petrobactin in Bacillus anthracis. Mol Microbiol 2012; 84:370-82. [PMID: 22429808 DOI: 10.1111/j.1365-2958.2012.08028.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In Bacillus anthracis the siderophore petrobactin is vital for iron acquisition and virulence. The petrobactin-binding receptor FpuA is required for these processes. Here additional components of petrobactin reacquisition are described. To identify these proteins, mutants of candidate permease and ATPase genes were generated allowing for characterization of multiple petrobactin ATP-binding cassette (ABC)-import systems. Either of two distinct permeases, FpuB or FatCD, is required for iron acquisition and play redundant roles in petrobactin transport. A mutant strain lacking both permeases, ΔfpuBΔfatCD, was incapable of using petrobactin as an iron source and exhibited attenuated virulence in a murine model of inhalational anthrax infection. ATPase mutants were generated in either of the permease mutant backgrounds to identify the ATPase(s) interacting with each individual permease channel. Mutants lacking the FpuB permease and FatE ATPase (ΔfpuBΔfatE) and a mutant lacking the distinct ATPases FpuC and FpuD generated in the ΔfatCD background (ΔfatCDΔfpuCΔfpuD) displayed phenotypic characteristics of a mutant deficient in petrobactin import. A mutant lacking all three of the identified ATPases (ΔfatEΔfpuCΔfpuD) exhibited the same growth defect in iron-depleted conditions. Taken together, these results provide the first description of the permease and ATPase proteins required for the import of petrobactin in B. anthracis.
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Affiliation(s)
- Shandee D Dixon
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48104, USA
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Updating perspectives on the initiation of Bacillus anthracis growth and dissemination through its host. Infect Immun 2012; 80:1626-33. [PMID: 22354031 DOI: 10.1128/iai.06061-11] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Since 1957, it has been proposed that the dissemination of inhalational anthrax required spores to be transported from the lumena of the lungs into the lymphatic system. In 2002, this idea was expanded to state that alveolar macrophages act as a "Trojan horse" capable of transporting spores across the lung epithelium into draining mediastinal lymph nodes. Since then, the Trojan horse model of dissemination has become the most widely cited model of inhalational infection as well as the focus of the majority of studies aiming to understand events initiating inhalational anthrax infections. However, recent observations derived from animal models of Bacillus anthracis infection are inconsistent with aspects of the Trojan horse model and imply that bacterial dissemination patterns during inhalational infection may be more similar to the cutaneous and gastrointestinal forms than previously thought. In light of these studies, it is of significant importance to reassess the mechanisms of inhalational anthrax dissemination, since it is this form of anthrax that is most lethal and of greatest concern when B. anthracis is weaponized. Here we propose a new "jailbreak" model of B. anthracis dissemination which applies to the dissemination of all common manifestations of the disease anthrax. The proposed model impacts the field by deemphasizing the role of host cells as conduits for dissemination and increasing the role of phagocytes as central players in innate defenses, while moving the focus toward interactions between B. anthracis and lymphoid and epithelial tissues.
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