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Virulence of Francisella tularensis Subspecies holarctica Biovar japonica and Phenotypic Change during Serial Passages on Artificial Media. Microorganisms 2020; 8:microorganisms8121881. [PMID: 33261098 PMCID: PMC7760542 DOI: 10.3390/microorganisms8121881] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 11/25/2020] [Accepted: 11/25/2020] [Indexed: 01/01/2023] Open
Abstract
Francisella tularensis (F. tularensis) is the etiological agent of the zoonotic disease tularemia. F. tularensis subspecies holarctica biovar japonica has rarely been isolated in Japan and is considered to have moderate virulence, although the biological properties of fresh isolates have not been analyzed in detail. Here, we analyzed the virulence of two strains of F. tularensis subspecies holarctica biovar japonica (NVF1 and KU-1) and their phenotypic stability during serial passages in Eugon chocolate agar (ECA) and Chamberlain's chemically defined medium (CDM) based agar (CDMA). C57BL/6 mice intradermally inoculated with 101 colony-forming units of NVF1 or KU-1 died within 9 days, with a median time to death of 7.5 and 7 days, respectively. Both NVF1 and KU-1 strains passaged on ECA 10 times had comparable virulence prior to passaging, whereas strains passaged on ECA 20 times and on CDMA 50 times were attenuated. Attenuated strains had decreased viability in 0.01% H2O2 and lower intracellular growth rates, suggesting both properties are important for F. tularensis virulence. Additionally, passage on ECA of the KU-1 strains altered lipopolysaccharide antigenicity and bacterial susceptibility to β-lactam antibiotics. Our data demonstrate F. tularensis strain virulence in Japan and contribute to understanding phenotypic differences between natural and laboratory environments.
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The Sensor Kinase QseC Regulates the Unlinked PmrA Response Regulator and Downstream Gene Expression in Francisella. J Bacteriol 2020; 202:JB.00321-20. [PMID: 32839173 DOI: 10.1128/jb.00321-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/13/2020] [Indexed: 12/22/2022] Open
Abstract
The facultative intracellular bacterial pathogen Francisella tularensis is the causative agent of tularemia in humans and animals. Gram-negative bacteria utilize two-component regulatory systems (TCS) to sense and respond to their changing environment. No classical, tandemly arranged sensor kinase and response regulator TCS genes exist in the human virulent Francisella tularensis subsp. tularensis, but orphaned members are present. PmrA is an orphan response regulator responsible for intramacrophage growth and virulence; however, the regulation of PmrA activity is not understood. We and others have shown that PmrA represses the expression of priM, described to encode an antivirulence determinant. By screening a mutant library for increased priM promoter activity, we identified the sensor kinase homolog QseC as an upstream regulator of priM expression, and this regulation is in part dependent upon the aspartate phosphorylation site of PmrA (D51). Several examined environmental signals, including epinephrine, which is reported to activate QseC in other bacteria, do not affect priM expression in a manner dependent on PmrA. Intramacrophage survival assays also question the finding that PriM is an antivirulence factor. Thus, these data suggest that the PmrA-regulated gene priM is modulated by the QseC-PmrA (QseB) TCS in Francisella IMPORTANCE The disease tularemia is caused by the highly infectious Gram-negative pathogen Francisella tularensis This bacterium encodes few regulatory factors (e.g., two-component systems [TCS]). PmrA, required for intramacrophage survival and virulence in the mouse model, is encoded by an orphan TCS response regulator gene. It is unclear how PmrA is responsive to environmental signals to regulate loci, including the PmrA-repressed gene priM We identify an orphan sensor kinase (QseC) that is required for priM repression and further explore both environmental signals that might regulate the QseC-PmrA TCS and the function of PriM.
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Freudenberger Catanzaro KC, Inzana TJ. The Francisella tularensis Polysaccharides: What Is the Real Capsule? Microbiol Mol Biol Rev 2020; 84:e00065-19. [PMID: 32051235 PMCID: PMC7018499 DOI: 10.1128/mmbr.00065-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Francisella tularensis is a tier 1 select agent responsible for tularemia in humans and a wide variety of animal species. Extensive research into understanding the virulence factors of the bacterium has been ongoing to develop an efficacious vaccine. At least two such virulence factors are described as capsules of F. tularensis: the O-antigen capsule and the capsule-like complex (CLC). These two separate entities aid in avoiding host immune defenses but have not been clearly differentiated. These components are distinct and differ in composition and genetic basis. The O-antigen capsule consists of a polysaccharide nearly identical to the lipopolysaccharide (LPS) O antigen, whereas the CLC is a heterogeneous complex of glycoproteins, proteins, and possibly outer membrane vesicles and tubes (OMV/Ts). In this review, the current understanding of these two capsules is summarized, and the historical references to "capsules" of F. tularensis are clarified. A significant amount of research has been invested into the composition of each capsule and the genes involved in synthesis of the polysaccharide portion of each capsule. Areas of future research include further exploration into the molecular regulation and pathways responsible for expression of each capsule and further elucidating the role that each capsule plays in virulence.
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Affiliation(s)
- Kelly C Freudenberger Catanzaro
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia, USA
| | - Thomas J Inzana
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia, USA
- Virginia Tech Carilion School of Medicine, Roanoke, Virginia, USA
- College of Veterinary Medicine, Long Island University, Brookville, New York, USA
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Nualnoi T, Kirosingh A, Basallo K, Hau D, Gates-Hollingsworth MA, Thorkildson P, Crump RB, Reed DE, Pandit S, AuCoin DP. Immunoglobulin G subclass switching impacts sensitivity of an immunoassay targeting Francisella tularensis lipopolysaccharide. PLoS One 2018; 13:e0195308. [PMID: 29630613 PMCID: PMC5890998 DOI: 10.1371/journal.pone.0195308] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 03/20/2018] [Indexed: 01/15/2023] Open
Abstract
The CDC Tier 1 select agent Francisella tularensis is a small, Gram-negative bacterium and the causative agent of tularemia, a potentially life-threatening infection endemic in the United States, Europe and Asia. Currently, there is no licensed vaccine or rapid point-of-care diagnostic test for tularemia. The purpose of this research was to develop monoclonal antibodies (mAbs) specific to the F. tularensis surface-expressed lipopolysaccharide (LPS) for a potential use in a rapid diagnostic test. Our initial antigen capture ELISA was developed using murine IgG3 mAb 1A4. Due to the low sensitivity of the initial assay, IgG subclass switching, which is known to have an effect on the functional affinity of a mAb, was exploited for the purpose of enhancing assay sensitivity. The ELISA developed using the IgG1 or IgG2b mAbs from the subclass-switch family of 1A4 IgG3 yielded improved assay sensitivity. However, surface plasmon resonance (SPR) demonstrated that the functional affinity was decreased as a result of subclass switching. Further investigation using direct ELISA revealed the potential self-association of 1A4 IgG3, which could explain the higher functional affinity and higher assay background seen with this mAb. Additionally, the higher assay background was found to negatively affect assay sensitivity. Thus, enhancement of the assay sensitivity by subclass switching is likely due to the decrease in assay background, simply by avoiding the self-association of IgG3.
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Affiliation(s)
- Teerapat Nualnoi
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States of America
| | - Adam Kirosingh
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States of America
| | - Kaitlin Basallo
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States of America
| | - Derrick Hau
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States of America
| | | | - Peter Thorkildson
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States of America
| | - Reva B. Crump
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States of America
| | - Dana E. Reed
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States of America
| | - Sujata Pandit
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States of America
| | - David P. AuCoin
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States of America
- * E-mail:
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Kinkead LC, Whitmore LC, McCracken JM, Fletcher JR, Ketelsen BB, Kaufman JW, Jones BD, Weiss DS, Barker JH, Allen LAH. Bacterial lipoproteins and other factors released by Francisella tularensis modulate human neutrophil lifespan: Effects of a TLR1 SNP on apoptosis inhibition. Cell Microbiol 2017; 20. [PMID: 29063667 PMCID: PMC5764820 DOI: 10.1111/cmi.12795] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/10/2017] [Accepted: 10/15/2017] [Indexed: 12/21/2022]
Abstract
Francisella tularensis infects several cell types including neutrophils, and aberrant neutrophil accumulation contributes to tissue destruction during tularaemia. We demonstrated previously that F. tularensis strains Schu S4 and live vaccine strain markedly delay human neutrophil apoptosis and thereby prolong cell lifespan, but the bacterial factors that mediate this aspect of virulence are undefined. Herein, we demonstrate that bacterial conditioned medium (CM) can delay apoptosis in the absence of direct infection. Biochemical analyses show that CM contained F. tularensis surface factors as well as outer membrane components. Our previous studies excluded roles for lipopolysaccharide and capsule in apoptosis inhibition, and current studies of [14C] acetate‐labelled bacteria argue against a role for other bacterial lipids in this process. At the same time, studies of isogenic mutants indicate that TolC and virulence factors whose expression requires FevR or MglA were also dispensable, demonstrating that apoptosis inhibition does not require Type I or Type VI secretion. Instead, we identified bacterial lipoproteins (BLPs) as active factors in CM. Additional studies of isolated BLPs demonstrated dose‐dependent neutrophil apoptosis inhibition via a TLR2‐dependent mechanism that is significantly influenced by a common polymorphism, rs5743618, in human TLR1. These data provide fundamental new insight into pathogen manipulation of neutrophil lifespan and BLP function.
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Affiliation(s)
- Lauren C Kinkead
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - Laura C Whitmore
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Jenna M McCracken
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA
| | - Joshua R Fletcher
- Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, USA
| | - Brandi B Ketelsen
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Iowa City VA Health Care System, Iowa City, Iowa, USA
| | - Justin W Kaufman
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Bradley D Jones
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA.,Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, USA
| | - David S Weiss
- Emory Vaccine Center, Emory University, Atlanta, Georgia, USA
| | - Jason H Barker
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA.,Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Lee-Ann H Allen
- Inflammation Program, University of Iowa, Iowa City, Iowa, USA.,Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, USA.,Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA.,Iowa City VA Health Care System, Iowa City, Iowa, USA
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The metabolic enzyme fructose-1,6-bisphosphate aldolase acts as a transcriptional regulator in pathogenic Francisella. Nat Commun 2017; 8:853. [PMID: 29021545 PMCID: PMC5636795 DOI: 10.1038/s41467-017-00889-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Accepted: 08/02/2017] [Indexed: 12/31/2022] Open
Abstract
The enzyme fructose-bisphosphate aldolase occupies a central position in glycolysis and gluconeogenesis pathways. Beyond its housekeeping role in metabolism, fructose-bisphosphate aldolase has been involved in additional functions and is considered as a potential target for drug development against pathogenic bacteria. Here, we address the role of fructose-bisphosphate aldolase in the bacterial pathogen Francisella novicida. We demonstrate that fructose-bisphosphate aldolase is important for bacterial multiplication in macrophages in the presence of gluconeogenic substrates. In addition, we unravel a direct role of this metabolic enzyme in transcription regulation of genes katG and rpoA, encoding catalase and an RNA polymerase subunit, respectively. We propose a model in which fructose-bisphosphate aldolase participates in the control of host redox homeostasis and the inflammatory immune response.The enzyme fructose-bisphosphate aldolase (FBA) plays central roles in glycolysis and gluconeogenesis. Here, Ziveri et al. show that FBA of the pathogen Francisella novicida acts, in addition, as a transcriptional regulator and is important for bacterial multiplication in macrophages.
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Holland KM, Rosa SJ, Kristjansdottir K, Wolfgeher D, Franz BJ, Zarrella TM, Kumar S, Sunagar R, Singh A, Bakshi CS, Namjoshi P, Barry EM, Sellati TJ, Kron SJ, Gosselin EJ, Reed DS, Hazlett KRO. Differential Growth of Francisella tularensis, Which Alters Expression of Virulence Factors, Dominant Antigens, and Surface-Carbohydrate Synthases, Governs the Apparent Virulence of Ft SchuS4 to Immunized Animals. Front Microbiol 2017; 8:1158. [PMID: 28690600 PMCID: PMC5479911 DOI: 10.3389/fmicb.2017.01158] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 06/07/2017] [Indexed: 12/29/2022] Open
Abstract
The gram-negative bacterium Francisella tularensis (Ft) is both a potential biological weapon and a naturally occurring microbe that survives in arthropods, fresh water amoeba, and mammals with distinct phenotypes in various environments. Previously, we used a number of measurements to characterize Ft grown in Brain-Heart Infusion (BHI) broth as (1) more similar to infection-derived bacteria, and (2) slightly more virulent in naïve animals, compared to Ft grown in Mueller Hinton Broth (MHB). In these studies we observed that the free amino acids in MHB repress expression of select Ft virulence factors by an unknown mechanism. Here, we tested the hypotheses that Ft grown in BHI (BHI-Ft) accurately displays a full protein composition more similar to that reported for infection-derived Ft and that this similarity would make BHI-Ft more susceptible to pre-existing, vaccine-induced immunity than MHB-Ft. We performed comprehensive proteomic analysis of Ft grown in MHB, BHI, and BHI supplemented with casamino acids (BCA) and compared our findings to published “omics” data derived from Ft grown in vivo. Based on the abundance of ~1,000 proteins, the fingerprint of BHI-Ft is one of nutrient-deprived bacteria that—through induction of a stringent-starvation-like response—have induced the FevR regulon for expression of the bacterium's virulence factors, immuno-dominant antigens, and surface-carbohydrate synthases. To test the notion that increased abundance of dominant antigens expressed by BHI-Ft would render these bacteria more susceptible to pre-existing, vaccine-induced immunity, we employed a battery of LVS-vaccination and S4-challenge protocols using MHB- and BHI-grown Ft S4. Contrary to our hypothesis, these experiments reveal that LVS-immunization provides a barrier to infection that is significantly more effective against an MHB-S4 challenge than a BHI-S4 challenge. The differences in apparent virulence to immunized mice are profoundly greater than those observed with primary infection of naïve mice. Our findings suggest that tularemia vaccination studies should be critically evaluated in regard to the growth conditions of the challenge agent.
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Affiliation(s)
- Kristen M Holland
- Department of Immunology and Microbial Disease, Albany Medical CollegeAlbany, NY, United States
| | - Sarah J Rosa
- Department of Immunology and Microbial Disease, Albany Medical CollegeAlbany, NY, United States
| | | | - Donald Wolfgeher
- Department of Molecular Genetics and Cell Biology, University of ChicagoChicago, IL, United States
| | - Brian J Franz
- Department of Immunology and Microbial Disease, Albany Medical CollegeAlbany, NY, United States
| | - Tiffany M Zarrella
- Department of Immunology and Microbial Disease, Albany Medical CollegeAlbany, NY, United States
| | - Sudeep Kumar
- Department of Immunology and Microbial Disease, Albany Medical CollegeAlbany, NY, United States
| | - Raju Sunagar
- Department of Immunology and Microbial Disease, Albany Medical CollegeAlbany, NY, United States
| | - Anju Singh
- Trudeau InstituteSaranac Lake, NY, United States
| | - Chandra S Bakshi
- Department of Microbiology and Immunology, New York Medical CollegeValhalla, NY, United States
| | - Prachi Namjoshi
- Department of Immunology and Microbial Disease, Albany Medical CollegeAlbany, NY, United States
| | - Eileen M Barry
- School of Medicine, University of MarylandBaltimore, MD, United States
| | | | - Stephen J Kron
- Department of Molecular Genetics and Cell Biology, University of ChicagoChicago, IL, United States
| | - Edmund J Gosselin
- Department of Immunology and Microbial Disease, Albany Medical CollegeAlbany, NY, United States
| | - Douglas S Reed
- Center for Vaccine Research, University of PittsburghPittsburgh, PA, United States
| | - Karsten R O Hazlett
- Department of Immunology and Microbial Disease, Albany Medical CollegeAlbany, NY, United States
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