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O’Brien DK, Ribot WJ, Chabot DJ, Scorpio A, Tobery SA, Jelacic TM, Wu Z, Friedlander AM. The capsule of Bacillus anthracis protects it from the bactericidal activity of human defensins and other cationic antimicrobial peptides. PLoS Pathog 2022; 18:e1010851. [PMID: 36174087 PMCID: PMC9560598 DOI: 10.1371/journal.ppat.1010851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 10/13/2022] [Accepted: 09/04/2022] [Indexed: 12/04/2022] Open
Abstract
During infection, Bacillus anthracis bacilli encounter potent antimicrobial peptides (AMPs) such as defensins. We examined the role that B. anthracis capsule plays in protecting bacilli from defensins and other cationic AMPs by comparing their effects on a fully virulent encapsulated wild type (WT) strain and an isogenic capsule-deficient capA mutant strain. We identified several human defensins and non-human AMPs that were capable of killing B. anthracis. The human alpha defensins 1–6 (HNP-1-4, HD-5-6), the human beta defensins 1–4 (HBD-1-4), and the non-human AMPs, protegrin, gramicidin D, polymyxin B, nisin, and melittin were all capable of killing both encapsulated WT and non-encapsulated capA mutant B. anthracis. However, non-encapsulated capA mutant bacilli were significantly more susceptible than encapsulated WT bacilli to killing by nearly all of the AMPs tested. We demonstrated that purified capsule bound HBD-2, HBD-3, and HNP-1 in an electrophoretic mobility shift assay. Furthermore, we determined that the capsule layer enveloping WT bacilli bound and trapped HBD-3, substantially reducing the amount reaching the cell wall. To assess whether released capsule might also play a protective role, we pre-incubated HBD-2, HBD-3, or HNP-1 with purified capsule before their addition to non-encapsulated capA mutant bacilli. We found that free capsule completely rescued the capA mutant bacilli from killing by HBD-2 and -3 while killing by HNP-1 was reduced to the level observed with WT bacilli. Together, these results suggest an immune evasion mechanism by which the capsule, both that enveloping the bacilli and released fragments, contributes to virulence by binding to and inhibiting the antimicrobial activity of cationic AMPs. Bacillus anthracis causes anthrax after spores infect the skin, respiratory tract, or gastrointestinal tract. Antimicrobial peptides (AMPs), such as defensins, are a first line of host defense that B. anthracis encounters in all of these tissues. B. anthracis bacteria are covered by a capsule that protects them from being engulfed and destroyed by phagocytic immune cells. In this study, we found that the capsule also provides protection from AMPs. An encapsulated B. anthracis strain is resistant to killing by multiple AMPs from humans and other species compared to an otherwise identical strain that is not encapsulated. By binding defensins the capsule surrounding the bacilli reduces the amount that gets to the bacterial cell wall where it can do damage. B. anthracis bacteria release large fragments of capsule in the host during infection and during growth in culture. We found that purified released capsule can bind defensins and reduce killing of non-encapsulated B. anthracis. Thus, both capsule covering the bacteria and capsule shed by the bacteria can contribute to the pathogenicity of B. anthracis by providing protection from AMPs. Our study reveals a new mechanism by which B. anthracis capsule contributes to virulence.
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Affiliation(s)
- David K. O’Brien
- United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, United States of America
| | - Wilson J. Ribot
- United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, United States of America
| | - Donald J. Chabot
- United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, United States of America
| | - Angelo Scorpio
- United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, United States of America
| | - Steven A. Tobery
- United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, United States of America
| | - Tanya M. Jelacic
- United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, United States of America
| | - Zhibin Wu
- Institute of Human Virology, University of Maryland Biotechnology Institute, Baltimore, Maryland, United States of America
| | - Arthur M. Friedlander
- United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, United States of America
- Department of Medicine, Uniformed University of Health Services, Bethesda, Maryland, United States of America
- * E-mail: ,
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Vietri NJ, Tobery SA, Chabot DJ, Ingavale S, Somerville BC, Miller JA, Schellhase CW, Twenhafel NA, Fetterer DP, Cote CK, Klimko CP, Boyer AE, Woolfitt AR, Barr JR, Wright ME, Friedlander AM. Clindamycin Protects Nonhuman Primates Against Inhalational Anthrax But Does Not Enhance Reduction of Circulating Toxin Levels When Combined With Ciprofloxacin. J Infect Dis 2021; 223:319-325. [PMID: 32697310 DOI: 10.1093/infdis/jiaa365] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 06/19/2020] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Inhalational anthrax is rare and clinical experience limited. Expert guidelines recommend treatment with combination antibiotics including protein synthesis-inhibitors to decrease toxin production and increase survival, although evidence is lacking. METHODS Rhesus macaques exposed to an aerosol of Bacillus anthracis spores were treated with ciprofloxacin, clindamycin, or ciprofloxacin + clindamycin after becoming bacteremic. Circulating anthrax lethal factor and protective antigen were quantitated pretreatment and 1.5 and 12 hours after beginning antibiotics. RESULTS In the clindamycin group, 8 of 11 (73%) survived demonstrating its efficacy for the first time in inhalational anthrax, compared to 9 of 9 (100%) with ciprofloxacin, and 8 of 11 (73%) with ciprofloxacin + clindamycin. These differences were not statistically significant. There were no significant differences between groups in lethal factor or protective antigen levels from pretreatment to 12 hours after starting antibiotics. Animals that died after clindamycin had a greater incidence of meningitis compared to those given ciprofloxacin or ciprofloxacin + clindamycin, but numbers of animals were very low and no definitive conclusion could be reached. CONCLUSION Treatment of inhalational anthrax with clindamycin was as effective as ciprofloxacin in the nonhuman primate. Addition of clindamycin to ciprofloxacin did not enhance reduction of circulating toxin levels.
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Affiliation(s)
- Nicholas J Vietri
- Division of Bacteriology, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Steven A Tobery
- Division of Bacteriology, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Donald J Chabot
- Division of Bacteriology, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Susham Ingavale
- Division of Bacteriology, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Brandon C Somerville
- Division of Bacteriology, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Jeremy A Miller
- Division of Bacteriology, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Chris W Schellhase
- Division of Pathology, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Nancy A Twenhafel
- Division of Pathology, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - David P Fetterer
- Division of Biostatistics, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Christopher K Cote
- Division of Bacteriology, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Christopher P Klimko
- Division of Bacteriology, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Anne E Boyer
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Adrian R Woolfitt
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - John R Barr
- National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Mary E Wright
- Division of Clinical Research, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, USA
| | - Arthur M Friedlander
- Headquarters, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA.,Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
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Waag DM, Chance TB, Trevino SR, Rossi FD, Fetterer DP, Amemiya K, Dankmeyer JL, Ingavale SS, Tobery SA, Zeng X, Kern SJ, Worsham PL, Cote CK, Welkos SL. Comparison of three non-human primate aerosol models for glanders, caused by Burkholderia mallei. Microb Pathog 2021; 155:104919. [PMID: 33915206 DOI: 10.1016/j.micpath.2021.104919] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 03/30/2021] [Accepted: 04/01/2021] [Indexed: 01/15/2023]
Abstract
Burkholderia mallei is a gram-negative obligate animal pathogen that causes glanders, a highly contagious and potentially fatal disease of solipeds including horses, mules, and donkeys. Humans are also susceptible, and exposure can result in a wide range of clinical forms, i.e., subclinical infection, chronic forms with remission and exacerbation, or acute and potentially lethal septicemia and/or pneumonia. Due to intrinsic antibiotic resistance and the ability of the organisms to survive intracellularly, current treatment regimens are protracted and complicated; and no vaccine is available. As a consequence of these issues, and since B. mallei is infectious by the aerosol route, B. mallei is regarded as a major potential biothreat agent. To develop optimal medical countermeasures and diagnostic tests, well characterized animal models of human glanders are needed. The goal of this study was to perform a head-to-head comparison of models employing three commonly used nonhuman primate (NHP) species, the African green monkey (AGM), Rhesus macaque, and the Cynomolgus macaque. The natural history of infection and in vitro clinical, histopathological, immunochemical, and bacteriological parameters were examined. The AGMs were the most susceptible NHP to B. mallei; five of six expired within 14 days. Although none of the Rhesus or Cynomolgus macaques succumbed, the Rhesus monkeys exhibited abnormal signs and clinical findings associated with B. mallei infection; and the latter may be useful for modeling chronic B. mallei infection. Based on the disease progression observations, gross and histochemical pathology, and humoral and cellular immune response findings, the AGM appears to be the optimal model of acute, lethal glanders infection. AGM models of infection by B. pseudomallei, the etiologic agent of melioidosis, have been characterized recently. Thus, the selection of the AGM species provides the research community with a single NHP model for investigations on acute, severe, inhalational melioidosis and glanders.
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Affiliation(s)
- David M Waag
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Taylor B Chance
- Pathology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Sylvia R Trevino
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Franco D Rossi
- Applied and Advanced Technology-Aerobiology, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - David P Fetterer
- Biostatistics Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Kei Amemiya
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Jennifer L Dankmeyer
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Susham S Ingavale
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Steven A Tobery
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Xiankun Zeng
- Pathology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Steven J Kern
- Biostatistics Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Patricia L Worsham
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
| | - Christopher K Cote
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA.
| | - Susan L Welkos
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA.
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Jelacic TM, Ribot WJ, Tobery SA, Chabot DJ, Friedlander AM. Poly-γ-Glutamic Acid Encapsulation of Bacillus anthracis Inhibits Human Dendritic Cell Responses. Immunohorizons 2021; 5:81-89. [PMID: 33563659 DOI: 10.4049/immunohorizons.2100004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 01/25/2021] [Indexed: 11/19/2022] Open
Abstract
The capsule of Bacillus anthracis is composed of a d isomer poly-γ-glutamic acid polymer, which is especially nonstimulatory to dendritic cells, even more so than similar mixed d, l isomer polymers from nonpathogenic Bacillus species. Capsule is an essential virulence factor for B. anthracis, protecting the bacilli from phagocytosis by innate immune cells. In this study, we demonstrate that encapsulation provides a further pathogenic advantage by shielding more inflammatory Ags on the bacillus surface, thereby reducing dendritic cell responses. We exposed human immature dendritic cells (DCs) to increasing multiplicities of infection (MOIs) of killed B. anthracis bacilli from the fully encapsulated wild-type Ames strain (WT) and an isogenic capsule-deficient strain (capA mutant). Both strains elicited robust cytokine responses, but IL-23, TNF-α, and IL-10 were significantly reduced in response to the encapsulated WT compared with capA mutant up to an MOI of 15. capA mutant bacilli could induce phenotypic maturation of immature DCs with upregulation of MHC classes I and II, CD83, and CCR7 at an MOI of 3.75, whereas encapsulated WT bacilli still did not induce significant upregulation of MHC classes I and II at an MOI of 15. DCs exposed to capA mutant bacilli (MOI 3.75) exhibited CCR7-dependent chemotaxis that was comparable to that of LPS-stimulated controls, whereas DCs exposed to encapsulated WT bacilli exhibited significantly less chemotaxis. We conclude that capsule shields more inflammatory surface Ags, delaying development of an adaptive immune response by reducing TNF-α, thereby inhibiting DC maturation.
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Affiliation(s)
- Tanya M Jelacic
- United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702; and
| | - Wilson J Ribot
- United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702; and
| | - Steven A Tobery
- United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702; and
| | - Donald J Chabot
- United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702; and
| | - Arthur M Friedlander
- United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702; and .,Department of Medicine, Uniformed Services University of Health Sciences, Bethesda, MD 20814
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Chua J, Bozue JA, Klimko CP, Shoe JL, Ruiz SI, Jensen CL, Tobery SA, Crumpler JM, Chabot DJ, Quirk AV, Hunter M, Harbourt DE, Friedlander AM, Cote CK. Formaldehyde and Glutaraldehyde Inactivation of Bacterial Tier 1 Select Agents in Tissues. Emerg Infect Dis 2019; 25:919-926. [PMID: 30681072 PMCID: PMC6478217 DOI: 10.3201/eid2505.180928] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
For safety, designated Select Agents in tissues must be inactivated and viability tested before the tissue undergoes further processing and analysis. In response to the shipping of samples of “inactivated” Bacillus anthracis that inadvertently contained live spores to nonregulated entities and partners worldwide, the Federal Register now mandates in-house validation of inactivation procedures and standardization of viability testing to detect live organisms in samples containing Select Agents that have undergone an inactivation process. We tested and validated formaldehyde and glutaraldehyde inactivation procedures for animal tissues infected with virulent B. anthracis, Burkholderia pseudomallei, Francisella tularensis, and Yersinia pestis. We confirmed that our fixation procedures for tissues containing these Tier 1 Select Agents resulted in complete inactivation and that our validated viability testing methods do not interfere with detection of live organisms. Institutions may use this work as a guide to develop and conduct their own testing to comply with the policy.
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Cote CK, Kaatz L, Reinhardt J, Bozue J, Tobery SA, Bassett AD, Sanz P, Darnell SC, Alem F, O'Brien AD, Welkos SL. Characterization of a multi-component anthrax vaccine designed to target the initial stages of infection as well as toxaemia. J Med Microbiol 2012; 61:1380-1392. [PMID: 22767539 DOI: 10.1099/jmm.0.045393-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Current vaccine approaches to combat anthrax are effective; however, they target only a single protein [the protective antigen (PA) toxin component] that is produced after spore germination. PA production is subsequently increased during later vegetative cell proliferation. Accordingly, several aspects of the vaccine strategy could be improved. The inclusion of spore-specific antigens with PA could potentially induce protection to initial stages of the disease. Moreover, adding other epitopes to the current vaccine strategy will decrease the likelihood of encountering a strain of Bacillus anthracis (emerging or engineered) that is refractory to the vaccine. Adding recombinant spore-surface antigens (e.g. BclA, ExsFA/BxpB and p5303) to PA has been shown to augment protection afforded by the latter using a challenge model employing immunosuppressed mice challenged with spores derived from the attenuated Sterne strain of B. anthracis. This report demonstrated similar augmentation utilizing guinea pigs or mice challenged with spores of the fully virulent Ames strain or a non-toxigenic but encapsulated ΔAmes strain of B. anthracis, respectively. Additionally, it was shown that immune interference did not occur if optimal amounts of antigen were administered. By administering the toxin and spore-based immunogens simultaneously, a significant adjuvant effect was also observed in some cases. Thus, these data further support the inclusion of recombinant spore antigens in next-generation anthrax vaccine strategies.
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Affiliation(s)
- C K Cote
- Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD 21702, USA
| | - L Kaatz
- Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD 21702, USA
| | - J Reinhardt
- Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD 21702, USA
| | - J Bozue
- Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD 21702, USA
| | - S A Tobery
- Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD 21702, USA
| | - A D Bassett
- Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD 21702, USA
| | - P Sanz
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA
| | - S C Darnell
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA
| | - F Alem
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA
| | - A D O'Brien
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA
| | - S L Welkos
- Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Frederick, MD 21702, USA
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Chabot DJ, Scorpio A, Tobery SA, Little SF, Norris SL, Friedlander AM. Anthrax capsule vaccine protects against experimental infection? Vaccine 2004; 23:43-7. [PMID: 15519706 DOI: 10.1016/j.vaccine.2004.05.029] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Revised: 05/11/2004] [Accepted: 05/13/2004] [Indexed: 11/25/2022]
Abstract
Efficacy of a poly-gamma-D-glutamic acid anthrax capsule vaccine was assessed in a mouse model of infection. Capsule by itself was protective against lethal challenge with a toxin(-), capsule(+) Bacillus anthracis strain. Conjugation of capsule to bovine serum albumin resulted in enhanced IgG anti-capsule antibodies measured by ELISA, but completely abrogated the protection. The protective unconjugated capsule vaccine elicited significantly higher IgM titers and opsonic activity than did the non-protective capsule conjugate. When tested against a fully virulent toxin(+), capsule(+) B. anthracis strain, neither capsule nor protective antigen alone was protective. However, the combination of the two protected against a lethal challenge. These results suggest that capsule may enhance the protection afforded by protective antigen vaccines against anthrax if opsonizing antibodies are produced. Surprisingly, some protection was also observed when protective antigen was conjugated to itself.
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Affiliation(s)
- Donald J Chabot
- US Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Frederick, MD 21701, USA.
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