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Harrell JE, Roy CJ, Gunn JS, McLachlan JB. Current vaccine strategies and novel approaches to combatting Francisella infection. Vaccine 2024; 42:2171-2180. [PMID: 38461051 DOI: 10.1016/j.vaccine.2024.02.086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 01/23/2024] [Accepted: 02/27/2024] [Indexed: 03/11/2024]
Abstract
Tularemia is caused by subspecies of Francisella tularensis and can manifest in a variety of disease states, with the pneumonic presentation resulting in the greatest mortality. Despite decades of research, there are no approved vaccines against F. tularensis in the United States. Traditional vaccination strategies, such as live-attenuated or subunit vaccines, are not favorable due to inadequate protection or safety concerns. Because of this, novel vaccination strategies are needed to combat tularemia. Here we discuss the current state of and challenges to the tularemia vaccine field and suggest novel vaccine approaches going forward that might be better suited for protecting against F. tularensis infection.
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Affiliation(s)
- Jaikin E Harrell
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Chad J Roy
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - John S Gunn
- Center for Microbial Pathogenesis, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA, Infectious Diseases Institute, The Ohio State University, Columbus, Ohio, USA, Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, USA
| | - James B McLachlan
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112, USA.
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2
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Zhao M, Zhai Y, Zai X, Mao Y, Hu E, Wei Z, Li Y, Li K, Liu Y, Xu J, Yu R, Chen W. Comparative evaluation of protective immunity against Francisella tularensis induced by subunit or adenovirus-vectored vaccines. Front Cell Infect Microbiol 2023; 13:1195314. [PMID: 37305410 PMCID: PMC10248143 DOI: 10.3389/fcimb.2023.1195314] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 05/16/2023] [Indexed: 06/13/2023] Open
Abstract
Tularemia is a highly contagious disease caused by infection with Francisella tularensis (Ft), a pathogenic intracellular gram-negative bacterium that infects a wide range of animals and causes severe disease and death in people, making it a public health concern. Vaccines are the most effective way to prevent tularemia. However, there are no Food and Drug Administration (FDA)-approved Ft vaccines thus far due to safety concerns. Herein, three membrane proteins of Ft, Tul4, OmpA, and FopA, and a molecular chaperone, DnaK, were identified as potential protective antigens using a multifactor protective antigen platform. Moreover, the recombinant DnaK, FopA, and Tul4 protein vaccines elicited a high level of IgG antibodies but did not protect against challenge. In contrast, protective immunity was elicited by a replication-defective human type 5 adenovirus (Ad5) encoding the Tul4, OmpA, FopA, and DnaK proteins (Ad5-Tul4, Ad5-OmpA, Ad5-FopA, and Ad5-DnaK) after a single immunization, and all Ad5-based vaccines stimulated a Th1-biased immune response. Moreover, intramuscular and intranasal vaccination with Ad5-Tul4 using the prime-boost strategy effectively eliminated Ft lung, spleen and liver colonization and provided nearly 80% protection against intranasal challenge with the Ft live vaccine strain (LVS). Only intramuscular, not intranasal vaccination, with Ad5-Tul4 protected mice from intraperitoneal challenge. This study provides a comprehensive comparison of protective immunity against Ft provided by subunit or adenovirus-vectored vaccines and suggests that mucosal vaccination with Ad5-Tul4 may yield desirable protective efficacy against mucosal infection, while intramuscular vaccination offers greater overall protection against intraperitoneal tularemia.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Rui Yu
- *Correspondence: Rui Yu, ; Wei Chen,
| | - Wei Chen
- *Correspondence: Rui Yu, ; Wei Chen,
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Suresh RV, Bradley EW, Higgs M, Russo VC, Alqahtani M, Huang W, Bakshi CS, Malik M. Nlrp3 Increases the Host's Susceptibility to Tularemia. Front Microbiol 2021; 12:725572. [PMID: 34690967 PMCID: PMC8527020 DOI: 10.3389/fmicb.2021.725572] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/08/2021] [Indexed: 11/13/2022] Open
Abstract
Francisella tularensis (F. tularensis) is a Gram-negative, intracellular bacterium and the causative agent of a fatal human disease known as tularemia. The CDC has classified F. tularensis as a Tier 1 Category A select agent based on its ease of aerosolization, low infectious dose, past use as a bioweapon, and the potential to be used as a bioterror agent. Francisella has a unique replication cycle. Upon its uptake, Francisella remains in the phagosomes for a short period and then escapes into the cytosol, where the replication occurs. Francisella is recognized by cytosolic pattern recognition receptors, Absent In Melanoma 2 (Aim2) and Nacht LRR and PYD domains containing Protein 3 (Nlrp3). The recognition of Francisella ligands by Aim2 and Nlrp3 triggers the assembly and activation of the inflammasome. The mechanism of activation of Aim2 is well established; however, how Nlrp3 inflammasome is activated in response to F. tularensis infection is not known. Unlike Aim2, the protective role of Nlrp3 against Francisella infection is not fully established. This study investigated the role of Nlrp3 and the potential mechanisms through which Nlrp3 exerts its detrimental effects on the host in response to F. tularensis infection. The results from in vitro studies demonstrate that Nlrp3 dampens NF-κB and MAPK signaling, and pro-inflammatory cytokine production, which allows replication of F. tularensis in infected macrophages. In vivo, Nlrp3 deficiency results in differential expression of several genes required to induce a protective immune response against respiratory tularemia. Nlrp3-deficient mice mount a stronger innate immune response, clear bacteria efficiently with minimal organ damage, and are more resistant to Francisella infection than their wild-type counterparts. Together, these results demonstrate that Nlrp3 enhances the host's susceptibility to F. tularensis by modulating the protective innate immune responses. Collectively, this study advances our understanding of the detrimental role of Nlrp3 in tularemia pathogenesis.
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Affiliation(s)
- Ragavan V. Suresh
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, NY, United States
| | - Elizabeth W. Bradley
- Department of Basic and Clinical Sciences, Albany College of Pharmacy and Health Sciences, Albany, NY, United States
| | - Matthew Higgs
- Department of Basic and Clinical Sciences, Albany College of Pharmacy and Health Sciences, Albany, NY, United States
| | - Vincenzo C. Russo
- Department of Basic and Clinical Sciences, Albany College of Pharmacy and Health Sciences, Albany, NY, United States
| | - Maha Alqahtani
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, NY, United States
| | - Wiehua Huang
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, NY, United States
| | - Chandra Shekhar Bakshi
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, NY, United States
| | - Meenakshi Malik
- Department of Basic and Clinical Sciences, Albany College of Pharmacy and Health Sciences, Albany, NY, United States
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Aim2 and Nlrp3 Are Dispensable for Vaccine-Induced Immunity against Francisella tularensis Live Vaccine Strain. Infect Immun 2021; 89:e0013421. [PMID: 33875472 DOI: 10.1128/iai.00134-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Francisella tularensis is a facultative, intracellular, Gram-negative bacterium that causes a fatal disease known as tularemia. Due to its extremely high virulence, ease of spread by aerosolization, and potential to be used as a bioterror agent, F. tularensis is classified by the CDC as a tier 1 category A select agent. Previous studies have demonstrated the roles of the inflammasome sensors absent in melanoma 2 (AIM2) and NLRP3 in the generation of innate immune responses to F. tularensis infection. However, contributions of both the AIM2 and NLRP3 to the development of vaccine-induced adaptive immune responses against F. tularensis are not known. This study determined the contributions of Aim2 and Nlrp3 inflammasome sensors to vaccine-induced immune responses in a mouse model of respiratory tularemia. We developed a model to vaccinate Aim2- and Nlrp3-deficient (Aim2-/- and Nlrp3-/-) mice using the emrA1 mutant of the F. tularensis live vaccine strain (LVS). The results demonstrate that the innate immune responses in Aim2-/- and Nlrp3-/- mice vaccinated with the emrA1 mutant differ from those of their wild-type counterparts. However, despite these differences in the innate immune responses, both Aim2-/- and Nlrp3-/- mice are fully protected against an intranasal lethal challenge dose of F. tularensis LVS. Moreover, the lack of both Aim2 and Nlrp3 inflammasome sensors does not affect the production of vaccination-induced antibody and cell-mediated responses. Overall, this study reports a novel finding that both Aim2 and Nlrp3 are dispensable for vaccination-induced immunity against respiratory tularemia caused by F. tularensis.
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Mohammadi N, Lindgren H, Golovliov I, Eneslätt K, Yamamoto M, Martin A, Henry T, Sjöstedt A. Guanylate-Binding Proteins Are Critical for Effective Control of Francisella tularensis Strains in a Mouse Co-Culture System of Adaptive Immunity. Front Cell Infect Microbiol 2020; 10:594063. [PMID: 33363054 PMCID: PMC7758253 DOI: 10.3389/fcimb.2020.594063] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 11/06/2020] [Indexed: 11/14/2022] Open
Abstract
Francisella tularensis is a Select Agent that causes the severe disease tularemia in humans and many animal species. The bacterium demonstrates rapid intracellular replication, however, macrophages can control its replication if primed and activation with IFN-γ is known to be essential, although alone not sufficient, to mediate such control. To further investigate the mechanisms that control intracellular F. tularensis replication, an in vitro co-culture system was utilized containing splenocytes obtained from naïve or immunized C57BL/6 mice as effectors and infected bone marrow-derived wild-type or chromosome-3-deficient guanylate-binding protein (GBP)-deficient macrophages. Cells were infected either with the F. tularensis live vaccine strain (LVS), the highly virulent SCHU S4 strain, or the surrogate for F. tularensis, F. novicida. Regardless of strain, significant control of the bacterial replication was observed in co-cultures with wild-type macrophages and immune splenocytes, but not in cultures with immune splenocytes and GBPchr3-deficient macrophages. Supernatants demonstrated very distinct, infectious agent-dependent patterns of 23 cytokines, whereas the cytokine patterns were only marginally affected by the presence or absence of GBPs. Levels of a majority of cytokines were inversely correlated to the degree of control of the SCHU S4 and LVS infections, but this was not the case for the F. novicida infection. Collectively, the co-culture assay based on immune mouse-derived splenocytes identified a dominant role of GBPs for the control of intracellular replication of various F. tularensis strains, regardless of their virulence, whereas the cytokine patterns markedly were dependent on the infectious agents, but less so on GBPs.
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Affiliation(s)
- Nasibeh Mohammadi
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Helena Lindgren
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Igor Golovliov
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Kjell Eneslätt
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Masahiro Yamamoto
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka, Japan
| | - Amandine Martin
- CIRI, Centre International de Recherche en Infectiologie, Inserm U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Univ Lyon, Lyon, France
| | - Thomas Henry
- CIRI, Centre International de Recherche en Infectiologie, Inserm U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Univ Lyon, Lyon, France
| | - Anders Sjöstedt
- Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
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Sutera V, Hennebique A, Lopez F, Fernandez N, Schneider D, Maurin M. Genomic trajectories to fluoroquinolone resistance in Francisella tularensis subsp. holarctica live vaccine strain. Int J Antimicrob Agents 2020; 56:106153. [PMID: 32911069 DOI: 10.1016/j.ijantimicag.2020.106153] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 07/04/2020] [Accepted: 08/29/2020] [Indexed: 11/16/2022]
Abstract
OBJECTIVES Fluoroquinolone (FQ)-resistant mutants were previously selected from the live vaccine strain (LVS) of Francisella tularensis (F. tularensis) subsp. holarctica. This study further characterised all genetic changes that occurred in these mutants during the evolutionary trajectory toward high-level FQ resistance, and their potential impact on F. tularensis antibiotic resistance and intracellular fitness. METHODS The whole genomes of FQ-resistant mutants were determined and compared with those of their parental strain. All detected mutations were evaluated for their potential impact on FQ resistance and intracellular multiplication of F. tularensis. RESULTS As compared with the parental LVS genome, 28 mutations were found in the derived FQ-resistant mutants. These mutations involved all genes encoding type II topoisomerases (i.e. gyrA, gyrB, parC, and parE). Interestingly, some of them were not previously associated with FQ resistance, warranting further characterisation. Mutations associated with FQ resistance were also found in other genes, including three encoding proteins involved in transport processes. Most of the detected mutations did not alter multiplication of the corresponding mutants in J774 cells. In contrast, all mutations at locus FTL_0439 encoding FupA/B, a membrane protein involved in iron transport, were associated with FQ resistance and fitness loss. CONCLUSION FQ resistance in F. tularensis is complex and may involve single or combined mutations in genes encoding type II topoisomerases, transport systems and FupA/B. In vivo studies are now required to assess the potential role of these mutations in FQ treatment failures.
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Affiliation(s)
- Vivien Sutera
- Centre National de Référence Francisella tularensis, Laboratoire de Bactériologie, Institut de Biologie et de Pathologie, CHU Grenoble Alpes, Grenoble, France; Laboratoire Techniques de l'Ingénierie Médicale et de la Complexité Informatique - Mathématiques et Applications (TIMC-IMAG), Univ. Grenoble Alpes, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
| | - Aurélie Hennebique
- Centre National de Référence Francisella tularensis, Laboratoire de Bactériologie, Institut de Biologie et de Pathologie, CHU Grenoble Alpes, Grenoble, France; Laboratoire Techniques de l'Ingénierie Médicale et de la Complexité Informatique - Mathématiques et Applications (TIMC-IMAG), Univ. Grenoble Alpes, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
| | - Fabrice Lopez
- Technological Advances for Genomics and Clinics (TAGC), Univ. Aix-Marseille II, Marseille, France; Transcriptomic and Genomic Marseille-Luminy (TGML), IBiSA platform, Marseille, France
| | - Nicolas Fernandez
- Technological Advances for Genomics and Clinics (TAGC), Univ. Aix-Marseille II, Marseille, France; Transcriptomic and Genomic Marseille-Luminy (TGML), IBiSA platform, Marseille, France
| | - Dominique Schneider
- Laboratoire Techniques de l'Ingénierie Médicale et de la Complexité Informatique - Mathématiques et Applications (TIMC-IMAG), Univ. Grenoble Alpes, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
| | - Max Maurin
- Centre National de Référence Francisella tularensis, Laboratoire de Bactériologie, Institut de Biologie et de Pathologie, CHU Grenoble Alpes, Grenoble, France; Laboratoire Techniques de l'Ingénierie Médicale et de la Complexité Informatique - Mathématiques et Applications (TIMC-IMAG), Univ. Grenoble Alpes, Centre National de la Recherche Scientifique (CNRS), Grenoble, France.
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Vaccine-Mediated Mechanisms Controlling Francisella tularensis SCHU S4 Growth in a Rat Co-Culture System. Pathogens 2020; 9:pathogens9050338. [PMID: 32365846 PMCID: PMC7280961 DOI: 10.3390/pathogens9050338] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 04/22/2020] [Accepted: 04/28/2020] [Indexed: 12/15/2022] Open
Abstract
Francisella tularensis causes the severe disease tularemia. In the present study, the aim was to identify correlates of protection in the rat co-culture model by investigating the immune responses using two vaccine candidates conferring distinct degrees of protection in rat and mouse models. The immune responses were characterized by use of splenocytes from naïve or Live vaccine strain- (LVS) or ∆clpB/∆wbtC-immunized Fischer 344 rats as effectors and bone marrow-derived macrophages infected with the highly virulent strain SCHU S4. A complex immune response was elicited, resulting in cytokine secretion, nitric oxide production, and efficient control of the intracellular bacterial growth. Addition of LVS-immune splenocytes elicited a significantly better control of bacterial growth than ∆clpB/∆wbtC splenocytes. This mirrored the efficacy of the vaccine candidates in the rat model. Lower levels of IFN-γ, TNF, fractalkine, IL-2, and nitrite were present in the co-cultures with ∆clpB/∆wbtC splenocytes than in those with splenocytes from LVS-immunized rats. Nitric oxide was found to be a correlate of protection, since the levels inversely correlated to the degree of protection and inhibition of nitric oxide production completely reversed the growth inhibition of SCHU S4. Overall, the results demonstrate that the co-culture assay with rat-derived cells is a suitable model to identify correlates of protection against highly virulent strains of F. tularensis
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An O-Antigen Glycoconjugate Vaccine Produced Using Protein Glycan Coupling Technology Is Protective in an Inhalational Rat Model of Tularemia. J Immunol Res 2018; 2018:8087916. [PMID: 30622981 PMCID: PMC6304830 DOI: 10.1155/2018/8087916] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 08/22/2018] [Accepted: 09/10/2018] [Indexed: 12/18/2022] Open
Abstract
There is a requirement for an efficacious vaccine to protect people against infection from Francisella tularensis, the etiological agent of tularemia. The lipopolysaccharide (LPS) of F. tularensis is suboptimally protective against a parenteral lethal challenge in mice. To develop a more efficacious subunit vaccine, we have used a novel biosynthetic technique of protein glycan coupling technology (PGCT) that exploits bacterial N-linked glycosylation to recombinantly conjugate F. tularensis O-antigen glycans to the immunogenic carrier protein Pseudomonas aeruginosa exoprotein A (ExoA). Previously, we demonstrated that an ExoA glycoconjugate with two glycosylation sequons was capable of providing significant protection to mice against a challenge with a low-virulence strain of F. tularensis. Here, we have generated a more heavily glycosylated conjugate vaccine and evaluated its efficacy in a Fischer 344 rat model of tularemia. We demonstrate that this glycoconjugate vaccine protected rats against disease and the lethality of an inhalational challenge with F. tularensis Schu S4. Our data highlights the potential of this biosynthetic approach for the creation of next-generation tularemia subunit vaccines.
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Sunagar R, Kumar S, Rosa SJ, Hazlett KRO, Gosselin EJ. Differential In Vitro Cultivation of Francisella tularensis Influences Live Vaccine Protective Efficacy by Altering the Immune Response. Front Immunol 2018; 9:1594. [PMID: 30042767 PMCID: PMC6048226 DOI: 10.3389/fimmu.2018.01594] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 06/27/2018] [Indexed: 11/13/2022] Open
Abstract
Francisella tularensis (Ft) is a biothreat agent for which there is no FDA-approved human vaccine. Currently, there are substantial efforts underway to develop both vaccines and improved tools to assess these vaccines. Ft expresses distinct sets of antigens (Ags) in vivo as compared to those expressed in vitro. Importantly, Ft grown in brain-heart infusion medium (BHIM) more closely mimics the antigenic profile of macrophage-grown Ft when compared to Mueller-Hinton medium (MHM)-grown Ft. Thus, we predicted that when used as a live vaccine BHIM-grown Ft (BHIM-Ft) would provide better protection, as compared to MHM-Ft. We first determined if there was a difference in growth kinetics between BHIM and MHM-Ft. We found that BHIM-Ft exhibited an initial growth advantage ex vivo that manifests as slightly hastened intracellular replication as compared to MHM-Ft. We also observed that BHIM-Ft exhibited an initial growth advantage in vivo represented by rapid bacterial expansion and systemic dissemination associated with a slightly shorter mean survival time of naive animals. Next, using two distinct strains of Ft LVS (WT and sodB), we observed that mice vaccinated with live BHIM-Ft LVS exhibited significantly better protection against Ft SchuS4 respiratory challenge compared to MHM-Ft-immunized mice. This enhanced protection correlated with lower bacterial burden, reduced tissue inflammation, and reduced pro-inflammatory cytokine production late in infection. Splenocytes from BHIM-Ft sodB-immunized mice contained more CD4+, effector, memory T-cells, and were more effective at limiting intracellular replication of Ft LVS in vitro. Concurrent with enhanced killing of Ft LVS, BHIM-Ft sodB-immune splenocytes produced significantly higher levels of IFN-γ and IL-17A cytokines than their MHM-Ft sodB-immunized counterparts indicating development of a more effective T cell memory response when immunizing mice with BHIM-Ft.
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Affiliation(s)
- Raju Sunagar
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY, United States
| | - Sudeep Kumar
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY, United States
| | - Sarah J Rosa
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY, United States
| | - Karsten R O Hazlett
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY, United States
| | - Edmund J Gosselin
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY, United States
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Mansour AA, Banik S, Suresh RV, Kaur H, Malik M, McCormick AA, Bakshi CS. An Improved Tobacco Mosaic Virus (TMV)-Conjugated Multiantigen Subunit Vaccine Against Respiratory Tularemia. Front Microbiol 2018; 9:1195. [PMID: 29922267 PMCID: PMC5996085 DOI: 10.3389/fmicb.2018.01195] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 05/16/2018] [Indexed: 12/22/2022] Open
Abstract
Francisella tularensis, the causative agent of the fatal human disease known as tularemia is classified as a Category A Select Agent by the Centers for Disease Control. No licensed vaccine is currently available for prevention of tularemia in the United States. Previously, we published that a tri-antigen tobacco mosaic virus (TMV) vaccine confers 50% protection in immunized mice against respiratory tularemia caused by F. tularensis. In this study, we refined the TMV-vaccine formulation to improve the level of protection in immunized C57BL/6 mice against respiratory tularemia. We developed a tetra-antigen vaccine by conjugating OmpA, DnaK, Tul4, and SucB proteins of Francisella to TMV. CpG was also included in the vaccine formulation as an adjuvant. Primary intranasal (i.n.) immunization followed by two booster immunizations with the tetra-antigen TMV vaccine protected 100% mice against i.n. 10LD100 challenges dose of F. tularensis live vaccine strain (LVS). Mice receiving three immunization doses of tetra-antigen TMV vaccine showed only transient body weight loss, cleared the infection rapidly, and showed minimal histopathological lesions in lungs, liver, and spleen following a lethal respiratory challenge with F. tularensis LVS. Mice immunized with the tetra-antigen TMV vaccine also induced strong ex vivo recall responses and were protected against a lethal challenge as late as 163 days post-primary immunization. Three immunization with the tetra-antigen TMV vaccine also induced a stronger humoral immune response predominated by IgG1, IgG2b, and IgG2c antibodies than mice receiving only a single or two immunizations. Remarkably, a single dose protected 40% of mice, while two doses protected 80% of mice from lethal pathogen challenge. Immunization of Interferon-gamma (IFN-γ)-deficient mice with the tetra-antigen TMV vaccine demonstrated an absolute requirement of IFN-γ for the generation of protective immune response against a lethal respiratory challenge with F. tularensis LVS. Collectively, this study further demonstrates the feasibility of TMV as an efficient platform for the delivery of multiple F. tularensis antigens and that tetra-antigen TMV vaccine formulation provides complete protection, and induces long-lasting protective and memory immune responses against respiratory tularemia caused by F. tularensis LVS.
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Affiliation(s)
- Ahd A Mansour
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY, United States
| | - Sukalyani Banik
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY, United States
| | - Ragavan V Suresh
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY, United States
| | - Hardeep Kaur
- College of Pharmacy, Touro University California, Vallejo, CA, United States
| | - Meenakshi Malik
- Department of Basic and Clinical Sciences, School of Arts and Sciences, Albany College of Pharmacy and Health Sciences, Albany, NY, United States
| | - Alison A McCormick
- College of Pharmacy, Touro University California, Vallejo, CA, United States
| | - Chandra S Bakshi
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY, United States
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11
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Jia Q, Horwitz MA. Live Attenuated Tularemia Vaccines for Protection Against Respiratory Challenge With Virulent F. tularensis subsp. tularensis. Front Cell Infect Microbiol 2018; 8:154. [PMID: 29868510 PMCID: PMC5963219 DOI: 10.3389/fcimb.2018.00154] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 04/24/2018] [Indexed: 12/11/2022] Open
Abstract
Francisella tularensis is the causative agent of tularemia and a Tier I bioterrorism agent. In the 1900s, several vaccines were developed against tularemia including the killed "Foshay" vaccine, subunit vaccines comprising F. tularensis protein(s) or lipoproteins(s) in an adjuvant formulation, and the F. tularensis Live Vaccine Strain (LVS); none were licensed in the U.S.A. or European Union. The LVS vaccine retains toxicity in humans and animals-especially mice-but has demonstrated efficacy in humans, and thus serves as the current gold standard for vaccine efficacy studies. The U.S.A. 2001 anthrax bioterrorism attack spawned renewed interest in vaccines against potential biowarfare agents including F. tularensis. Since live attenuated-but not killed or subunit-vaccines have shown promising efficacy and since vaccine efficacy against respiratory challenge with less virulent subspecies holarctica or F. novicida, or against non-respiratory challenge with virulent subsp. tularensis (Type A) does not reliably predict vaccine efficacy against respiratory challenge with virulent subsp. tularensis, the route of transmission and species of greatest concern in a bioterrorist attack, in this review, we focus on live attenuated tularemia vaccine candidates tested against respiratory challenge with virulent Type A strains, including homologous vaccines derived from mutants of subsp. holarctica, F. novicida, and subsp. tularensis, and heterologous vaccines developed using viral or bacterial vectors to express F. tularensis immunoprotective antigens. We compare the virulence and efficacy of these vaccine candidates with that of LVS and discuss factors that can significantly impact the development and evaluation of live attenuated tularemia vaccines. Several vaccines meet what we would consider the minimum criteria for vaccines to go forward into clinical development-safety greater than LVS and efficacy at least as great as LVS, and of these, several meet the higher standard of having efficacy ≥LVS in the demanding mouse model of tularemia. These latter include LVS with deletions in purMCD, sodBFt , capB or wzy; LVS ΔcapB that also overexpresses Type VI Secretion System (T6SS) proteins; FSC200 with a deletion in clpB; the single deletional purMCD mutant of F. tularensis SCHU S4, and a heterologous prime-boost vaccine comprising LVS ΔcapB and Listeria monocytogenes expressing T6SS proteins.
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Affiliation(s)
- Qingmei Jia
- Division of Infectious Diseases, Department of Medicine, 37-121 Center for Health Sciences, School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Marcus A. Horwitz
- Division of Infectious Diseases, Department of Medicine, 37-121 Center for Health Sciences, School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
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Eneslätt K, Golovliov I, Rydén P, Sjöstedt A. Vaccine-Mediated Mechanisms Controlling Replication of Francisella tularensis in Human Peripheral Blood Mononuclear Cells Using a Co-culture System. Front Cell Infect Microbiol 2018; 8:27. [PMID: 29468144 PMCID: PMC5808333 DOI: 10.3389/fcimb.2018.00027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 01/23/2018] [Indexed: 11/17/2022] Open
Abstract
Cell-mediated immunity (CMI) is normally required for efficient protection against intracellular infections, however, identification of correlates is challenging and they are generally lacking. Francisella tularensis is a highly virulent, facultative intracellular bacterium and CMI is critically required for protection against the pathogen, but how this is effectuated in humans is poorly understood. To understand the protective mechanisms, we established an in vitro co-culture assay to identify how control of infection of F. tularensis is accomplished by human cells and hypothesized that the model will mimic in vivo immune mechanisms. Non-adherent peripheral blood mononuclear cells (PBMCs) were expanded with antigen and added to cultures with adherent PBMC infected with the human vaccine strain, LVS, or the highly virulent SCHU S4 strain. Intracellular numbers of F. tularensis was followed for 72 h and secreted and intracellular cytokines were analyzed. Addition of PBMC expanded from naïve individuals, i.e., those with no record of immunization to F. tularensis, generally resulted in little or no control of intracellular bacterial growth, whereas addition of PBMC from a majority of F. tularensis-immune individuals executed static and sometimes cidal effects on intracellular bacteria. Regardless of infecting strain, statistical differences between the two groups were significant, P < 0.05. Secretion of 11 cytokines was analyzed after 72 h of infection and significant differences with regard to secretion of IFN-γ, TNF, and MIP-1β was observed between immune and naïve individuals for LVS-infected cultures. Also, in LVS-infected cultures, CD4 T cells from vaccinees, but not CD8 T cells, showed significantly higher expression of IFN-γ, MIP-1β, TNF, and CD107a than cells from naïve individuals. The co-culture system appears to identify correlates of immunity that are relevant for the understanding of mechanisms of the protective host immunity to F. tularensis.
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Affiliation(s)
- Kjell Eneslätt
- Department of Clinical Microbiology, Clinical Bacteriology, and Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden
| | - Igor Golovliov
- Department of Clinical Microbiology, Clinical Bacteriology, and Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden
| | - Patrik Rydén
- Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden
| | - Anders Sjöstedt
- Department of Clinical Microbiology, Clinical Bacteriology, and Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden
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Tian D, Uda A, Park ES, Hotta A, Fujita O, Yamada A, Hirayama K, Hotta K, Koyama Y, Azaki M, Morikawa S. Evaluation of Francisella tularensis ΔpdpC as a candidate live attenuated vaccine against respiratory challenge by a virulent SCHU P9 strain of Francisella tularensis in a C57BL/6J mouse model. Microbiol Immunol 2018; 62:24-33. [PMID: 29171073 DOI: 10.1111/1348-0421.12555] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 11/16/2017] [Accepted: 11/20/2017] [Indexed: 12/11/2022]
Abstract
Francisella tularensis, which causes tularemia, is an intracellular gram-negative bacterium. F. tularensis has received significant attention in recent decades because of its history as a biological weapon. Thus, development of novel vaccines against tularemia has been an important goal. The attenuated F. tularensis strain ΔpdpC, in which the pathogenicity determinant protein C gene (pdpC) has been disrupted by TargeTron mutagenesis, was investigated as a potential vaccine candidate for tularemia in the present study. C57BL/6J mice immunized s.c. with 1 × 106 CFUs of ΔpdpC were challenged intranasally with 100× the median lethal dose (LD50 ) of a virulent SCHU P9 strain 21 days post immunization. Protection against this challenge was achieved in 38% of immunized C57BL/6J mice administered 100 LD50 of this strain. Conversely, all unimmunized mice succumbed to death 6 days post challenge. Survival rates were significantly higher in vaccinated than in unimmunized mice. In addition, ΔpdpC was passaged serially in mice to confirm its stable attenuation. Low bacterial loads persisted in mouse spleens during the first to tenth passages. No statistically significant changes in the number of CFUs were observed during in vivo passage of ΔpdpC. The inserted intron sequences for disrupting pdpC were completely maintained even after the tenth passage in mice. Considering the stable attenuation and intron sequences, it is suggested that ΔpdpC is a promising tularemia vaccine candidate.
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Affiliation(s)
- Deyu Tian
- Laboratory of Veterinary Public Health, Department of Veterinary Medical Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan.,Department of Veterinary Science, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku, Tokyo 162-8640, Japan
| | - Akihiko Uda
- Department of Veterinary Science, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku, Tokyo 162-8640, Japan
| | - Eun-Sil Park
- Department of Veterinary Science, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku, Tokyo 162-8640, Japan
| | - Akitoyo Hotta
- Department of Veterinary Science, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku, Tokyo 162-8640, Japan
| | - Osamu Fujita
- Department of Veterinary Science, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku, Tokyo 162-8640, Japan
| | - Akio Yamada
- Laboratory of Veterinary Public Health, Department of Veterinary Medical Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan
| | - Kazuhiro Hirayama
- Laboratory of Veterinary Public Health, Department of Veterinary Medical Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan
| | - Kozue Hotta
- Laboratory of Veterinary Public Health, Department of Veterinary Medical Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan
| | - Yuuki Koyama
- Department of Veterinary Science, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku, Tokyo 162-8640, Japan.,Major Track of Applied Veterinary Science, Doctoral Course of the United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
| | - Mika Azaki
- Department of Integrated Science in Physics and Biology College of Humanities and Sciences, Nihon University, 3-25-40 Sakurajosui, Setagaya, Tokyo 156-8550, Japan
| | - Shigeru Morikawa
- Department of Veterinary Science, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku, Tokyo 162-8640, Japan.,Major Track of Applied Veterinary Science, Doctoral Course of the United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
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Golovliov I, Lindgren H, Eneslätt K, Conlan W, Mosnier A, Henry T, Sjöstedt A. An In Vitro Co-culture Mouse Model Demonstrates Efficient Vaccine-Mediated Control of Francisella tularensis SCHU S4 and Identifies Nitric Oxide as a Predictor of Efficacy. Front Cell Infect Microbiol 2016; 6:152. [PMID: 27933275 PMCID: PMC5122580 DOI: 10.3389/fcimb.2016.00152] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2016] [Accepted: 11/01/2016] [Indexed: 11/13/2022] Open
Abstract
Francisella tularensis is a highly virulent intracellular bacterium and cell-mediated immunity is critical for protection, but mechanisms of protection against highly virulent variants, such as the prototypic strain F. tularensis strain SCHU S4, are poorly understood. To this end, we established a co-culture system, based on splenocytes from naïve, or immunized mice and in vitro infected bone marrow-derived macrophages that allowed assessment of mechanisms controlling infection with F. tularensis. We utilized the system to understand why the clpB gene deletion mutant, ΔclpB, of SCHU S4 shows superior efficacy as a vaccine in the mouse model as compared to the existing human vaccine, the live vaccine strain (LVS). Compared to naïve splenocytes, ΔclpB-, or LVS-immune splenocytes conferred very significant control of a SCHU S4 infection and the ΔclpB-immune splenocytes were superior to the LVS-immune splenocytes. Cultures with the ΔclpB-immune splenocytes also contained higher levels of IFN-γ, IL-17, and GM-CSF and nitric oxide, and T cells expressing combinations of IFN-γ, TNF-α, and IL-17, than did cultures with LVS-immune splenocytes. There was strong inverse correlation between bacterial replication and levels of nitrite, an end product of nitric oxide, and essentially no control was observed when BMDM from iNOS-/- mice were infected. Collectively, the co-culture model identified a critical role of nitric oxide for protection against a highly virulent strain of F. tularensis.
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Affiliation(s)
- Igor Golovliov
- Laboratory for Molecular Infection Medicine Sweden, Department of Clinical Microbiology, Clinical Bacteriology, and Umeå University Umeå, Sweden
| | - Helena Lindgren
- Laboratory for Molecular Infection Medicine Sweden, Department of Clinical Microbiology, Clinical Bacteriology, and Umeå University Umeå, Sweden
| | - Kjell Eneslätt
- Laboratory for Molecular Infection Medicine Sweden, Department of Clinical Microbiology, Clinical Bacteriology, and Umeå University Umeå, Sweden
| | - Wayne Conlan
- National Research Council Canada, Institute for Biological Sciences Ottawa, ON, Canada
| | - Amandine Mosnier
- Centre International de Recherche en Infectiologie, Institut national de la santé et de la recherche médicale, U1111 Lyon, France
| | - Thomas Henry
- Centre International de Recherche en Infectiologie, Institut national de la santé et de la recherche médicale, U1111 Lyon, France
| | - Anders Sjöstedt
- Laboratory for Molecular Infection Medicine Sweden, Department of Clinical Microbiology, Clinical Bacteriology, and Umeå University Umeå, Sweden
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Rowe HM, Huntley JF. From the Outside-In: The Francisella tularensis Envelope and Virulence. Front Cell Infect Microbiol 2015; 5:94. [PMID: 26779445 PMCID: PMC4688374 DOI: 10.3389/fcimb.2015.00094] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 12/07/2015] [Indexed: 12/20/2022] Open
Abstract
Francisella tularensis is a highly-infectious bacterium that causes the rapid, and often lethal disease, tularemia. Many studies have been performed to identify and characterize the virulence factors that F. tularensis uses to infect a wide variety of hosts and host cell types, evade immune defenses, and induce severe disease and death. This review focuses on the virulence factors that are present in the F. tularensis envelope, including capsule, LPS, outer membrane, periplasm, inner membrane, secretion systems, and various molecules in each of aforementioned sub-compartments. Whereas, no single bacterial molecule or molecular complex single-handedly controls F. tularensis virulence, we review here how diverse bacterial systems work in conjunction to subvert the immune system, attach to and invade host cells, alter phagosome/lysosome maturation pathways, replicate in host cells without being detected, inhibit apoptosis, and induce host cell death for bacterial release and infection of adjacent cells. Given that the F. tularensis envelope is the outermost layer of the bacterium, we highlight herein how many of these molecules directly interact with the host to promote infection and disease. These and future envelope studies are important to advance our collective understanding of F. tularensis virulence mechanisms and offer targets for future vaccine development efforts.
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Affiliation(s)
- Hannah M Rowe
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences Toledo, OH, USA
| | - Jason F Huntley
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences Toledo, OH, USA
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Rabadi SM, Sanchez BC, Varanat M, Ma Z, Catlett SV, Melendez JA, Malik M, Bakshi CS. Antioxidant Defenses of Francisella tularensis Modulate Macrophage Function and Production of Proinflammatory Cytokines. J Biol Chem 2015; 291:5009-21. [PMID: 26644475 DOI: 10.1074/jbc.m115.681478] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Indexed: 11/06/2022] Open
Abstract
Francisella tularensis, the causative agent of a fatal human disease known as tularemia, has been used in the bioweapon programs of several countries in the past, and now it is considered a potential bioterror agent. Extreme infectivity and virulence of F. tularensis is due to its ability to evade immune detection and to suppress the host's innate immune responses. However, Francisella-encoded factors and mechanisms responsible for causing immune suppression are not completely understood. Macrophages and neutrophils generate reactive oxygen species (ROS)/reactive nitrogen species as a defense mechanism for the clearance of phagocytosed microorganisms. ROS serve a dual role; at high concentrations they act as microbicidal effector molecules that destroy intracellular pathogens, and at low concentrations they serve as secondary signaling messengers that regulate the expression of various inflammatory mediators. We hypothesized that the antioxidant defenses of F. tularensis maintain redox homeostasis in infected macrophages to prevent activation of redox-sensitive signaling components that ultimately result in suppression of pro-inflammatory cytokine production and macrophage microbicidal activity. We demonstrate that antioxidant enzymes of F. tularensis prevent the activation of redox-sensitive MAPK signaling components, NF-κB signaling, and the production of pro-inflammatory cytokines by inhibiting the accumulation of ROS in infected macrophages. We also report that F. tularensis inhibits ROS-dependent autophagy to promote its intramacrophage survival. Collectively, this study reveals novel pathogenic mechanisms adopted by F. tularensis to modulate macrophage innate immune functions to create an environment permissive for its intracellular survival and growth.
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Affiliation(s)
- Seham M Rabadi
- From the Department of Microbiology and Immunology, New York Medical College, Valhalla, New York 10595
| | - Belkys C Sanchez
- From the Department of Microbiology and Immunology, New York Medical College, Valhalla, New York 10595
| | - Mrudula Varanat
- From the Department of Microbiology and Immunology, New York Medical College, Valhalla, New York 10595
| | - Zhuo Ma
- the Department of Basic and Social Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York 12208, and
| | - Sally V Catlett
- the Department of Basic and Social Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York 12208, and
| | - Juan Andres Melendez
- the Colleges of Nanoscale Science and Engineering, State University of New York Polytechnic Institute, Albany, New York 12203
| | - Meenakshi Malik
- the Department of Basic and Social Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York 12208, and
| | - Chandra Shekhar Bakshi
- From the Department of Microbiology and Immunology, New York Medical College, Valhalla, New York 10595,
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Development of a Multivalent Subunit Vaccine against Tularemia Using Tobacco Mosaic Virus (TMV) Based Delivery System. PLoS One 2015; 10:e0130858. [PMID: 26098553 PMCID: PMC4476615 DOI: 10.1371/journal.pone.0130858] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 05/26/2015] [Indexed: 11/21/2022] Open
Abstract
Francisella tularensis is a facultative intracellular pathogen, and is the causative agent of a fatal human disease known as tularemia. F. tularensis is classified as a Category A Biothreat agent by the CDC based on its use in bioweapon programs by several countries in the past and its potential to be used as an agent of bioterrorism. No licensed vaccine is currently available for prevention of tularemia. In this study, we used a novel approach for development of a multivalent subunit vaccine against tularemia by using an efficient tobacco mosaic virus (TMV) based delivery platform. The multivalent subunit vaccine was formulated to contain a combination of F. tularensis protective antigens: OmpA-like protein (OmpA), chaperone protein DnaK and lipoprotein Tul4 from the highly virulent F. tularensis SchuS4 strain. Two different vaccine formulations and immunization schedules were used. The immunized mice were challenged with lethal (10xLD100) doses of F. tularensis LVS on day 28 of the primary immunization and observed daily for morbidity and mortality. Results from this study demonstrate that TMV can be used as a carrier for effective delivery of multiple F. tularensis antigens. TMV-conjugate vaccine formulations are safe and multiple doses can be administered without causing any adverse reactions in immunized mice. Immunization with TMV-conjugated F. tularensis proteins induced a strong humoral immune response and protected mice against respiratory challenges with very high doses of F. tularensis LVS. This study provides a proof-of-concept that TMV can serve as a suitable platform for simultaneous delivery of multiple protective antigens of F. tularensis. Refinement of vaccine formulations coupled with TMV-targeting strategies developed in this study will provide a platform for development of an effective tularemia subunit vaccine as well as a vaccination approach that may broadly be applicable to many other bacterial pathogens.
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Suresh RV, Ma Z, Sunagar R, Bhatty V, Banik S, Catlett SV, Gosselin EJ, Malik M, Bakshi CS. Preclinical testing of a vaccine candidate against tularemia. PLoS One 2015; 10:e0124326. [PMID: 25897786 PMCID: PMC4405390 DOI: 10.1371/journal.pone.0124326] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 03/02/2015] [Indexed: 11/18/2022] Open
Abstract
Tularemia is caused by a gram-negative, intracellular bacterial pathogen, Francisella tularensis (Ft). The history weaponization of Ft in the past has elevated concerns that it could be used as a bioweapon or an agent of bioterrorism. Since the discovery of Ft, three broad approaches adopted for tularemia vaccine development have included inactivated, live attenuated, or subunit vaccines. Shortcomings in each of these approaches have hampered the development of a suitable vaccine for prevention of tularemia. Recently, we reported an oxidant sensitive mutant of Ft LVS in putative EmrA1 (FTL_0687) secretion protein. The emrA1 mutant is highly sensitive to oxidants, attenuated for intramacrophage growth and virulence in mice. We reported that EmrA1 contributes to oxidant resistance by affecting the secretion of antioxidant enzymes SodB and KatG. This study investigated the vaccine potential of the emrA1 mutant in prevention of respiratory tularemia caused by Ft LVS and the virulent SchuS4 strain in C57BL/6 mice. We report that emrA1 mutant is safe and can be used at an intranasal (i. n.) immunization dose as high as 1x106 CFU without causing any adverse effects in immunized mice. The emrA1 mutant is cleared by vaccinated mice by day 14-21 post-immunization, induces minimal histopathological lesions in lungs, liver and spleen and a strong humoral immune response. The emrA1 mutant vaccinated mice are protected against 1000-10,000LD100 doses of i.n. Ft LVS challenge. Such a high degree of protection has not been reported earlier against respiratory challenge with Ft LVS using a single immunization dose with an attenuated mutant generated on Ft LVS background. The emrA1 mutant also provides partial protection against i.n. challenge with virulent Ft SchuS4 strain in vaccinated C57BL/6 mice. Collectively, our results further support the notion that antioxidants of Ft may serve as potential targets for development of effective vaccines for prevention of tularemia.
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Affiliation(s)
| | - Zhuo Ma
- Albany College of Pharmacy and Health Sciences, Albany, United States of America
| | - Raju Sunagar
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, United States of America
| | - Vivek Bhatty
- Department of Microbiology and Immunology, New York Medical College, Valhalla, United States of America
| | - Sukalyani Banik
- Department of Microbiology and Immunology, New York Medical College, Valhalla, United States of America
| | - Sally V. Catlett
- Albany College of Pharmacy and Health Sciences, Albany, United States of America
| | - Edmund J. Gosselin
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, United States of America
| | - Meenakshi Malik
- Albany College of Pharmacy and Health Sciences, Albany, United States of America
- * E-mail: (MM); (CSB)
| | - Chandra Shekhar Bakshi
- Department of Microbiology and Immunology, New York Medical College, Valhalla, United States of America
- * E-mail: (MM); (CSB)
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Kubelkova K, Macela A. Putting the Jigsaw Together - A Brief Insight Into the Tularemia. Open Life Sci 2015. [DOI: 10.1515/biol-2015-0013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
AbstractTularemia is a debilitating febrile and potentially fatal zoonotic disease of humans and other vertebrates caused by the Gram-negative bacterium Francisella tularensis. The natural reservoirs are small rodents, hares, and possibly amoebas in water. The etiological agent, Francisella tularensis, is a non-spore forming, encapsulated, facultative intracellular bacterium, a member of the γ-Proteobacteria class of Gram-negative bacteria. Francisella tularensis is capable of invading and replicating within phagocytic as well as non-phagocytic cells and modulate inflammatory response. Infection by the pulmonary, dermal, or oral routes, respectively, results in pneumonic, ulceroglandular, or oropharyngeal tularemia. The highest mortality rates are associated with the pneumonic form of this disease. All members of Francisella tularensis species cause more or less severe disease Due to their abilities to be transmitted to humans via multiple routes and to be disseminated via biological aerosol that can cause the disease after inhalation of even an extremely low infectious dose, Francisella tularensis has been classified as a Category A bioterrorism agent. The current standard of care for tularemia is treatment with antibiotics, as this therapy is highly effective if used soon after infection, although it is not, however, absolutely effective in all cases.
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Ren G, Champion MM, Huntley JF. Identification of disulfide bond isomerase substrates reveals bacterial virulence factors. Mol Microbiol 2014; 94:926-44. [PMID: 25257164 DOI: 10.1111/mmi.12808] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2014] [Indexed: 01/22/2023]
Abstract
Bacterial pathogens are exposed to toxic molecules inside the host and require efficient systems to form and maintain correct disulfide bonds for protein stability and function. The intracellular pathogen Francisella tularensis encodes a disulfide bond formation protein ortholog, DsbA, which previously was reported to be required for infection of macrophages and mice. However, the molecular mechanisms by which F. tularensis DsbA contributes to virulence are unknown. Here, we demonstrate that F. tularensis DsbA is a bifunctional protein that oxidizes and, more importantly, isomerizes complex disulfide connectivity in substrates. A single amino acid in the conserved cis-proline loop of the DsbA thioredoxin domain was shown to modulate both isomerase activity and F. tularensis virulence. Trapping experiments in F. tularensis identified over 50 F. tularensis DsbA substrates, including outer membrane proteins, virulence factors, and many hypothetical proteins. Six of these hypothetical proteins were randomly selected and deleted, revealing two novel proteins, FTL_1548 and FTL_1709, which are required for F. tularensis virulence. We propose that the extreme virulence of F. tularensis is partially due to the bifunctional nature of DsbA, that many of the newly identified substrates are required for virulence, and that the development of future DsbA inhibitors could have broad anti-bacterial implications.
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Affiliation(s)
- Guoping Ren
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, 43614, USA
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FTT0831c/FTL_0325 contributes to Francisella tularensis cell division, maintenance of cell shape, and structural integrity. Infect Immun 2014; 82:2935-48. [PMID: 24778115 DOI: 10.1128/iai.00102-14] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The Francisella FTT0831c/FTL_0325 gene encodes amino acid motifs to suggest it is a lipoprotein and that it may interact with the bacterial cell wall as a member of the OmpA-like protein family. Previous studies have suggested that FTT0831c is surface exposed and required for virulence of Francisella tularensis by subverting the host innate immune response (M. Mahawar et al., J. Biol. Chem. 287:25216-25229, 2012). We also found that FTT0831c is required for murine pathogenesis and intramacrophage growth of Schu S4, but we propose a different model to account for the proinflammatory nature of the resultant mutants. First, inactivation of FTL_0325 from live vaccine strain (LVS) or FTT0831c from Schu S4 resulted in temperature-dependent defects in cell viability and morphology. Loss of FTT0831c was also associated with an unusual defect in lipopolysaccharide O-antigen synthesis, but loss of FTL_0325 was not. Full restoration of these properties was observed in complemented strains expressing FTT0831c in trans, but not in strains lacking the OmpA motif, suggesting that cell wall contact is required. Finally, growth of the LVS FTL_0325 mutant in Mueller-Hinton broth at 37°C resulted in the appearance of membrane blebs at the poles and midpoint, prior to the formation of enlarged round cells that showed evidence of compromised cellular membranes. Taken together, these data are more consistent with the known structural role of OmpA-like proteins in linking the OM to the cell wall and, as such, maintenance of structural integrity preventing altered surface exposure or release of Toll-like receptor 2 agonists during rapid growth of Francisella in vitro and in vivo.
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Novel catanionic surfactant vesicle vaccines protect against Francisella tularensis LVS and confer significant partial protection against F. tularensis Schu S4 strain. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2013; 21:212-26. [PMID: 24351755 DOI: 10.1128/cvi.00738-13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Francisella tularensis is a Gram-negative immune-evasive coccobacillus that causes tularemia in humans and animals. A safe and efficacious vaccine that is protective against multiple F. tularensis strains has yet to be developed. In this study, we tested a novel vaccine approach using artificial pathogens, synthetic nanoparticles made from catanionic surfactant vesicles that are functionalized by the incorporation of either F. tularensis type B live vaccine strain (F. tularensis LVS [LVS-V]) or F. tularensis type A Schu S4 strain (F. tularensis Schu S4 [Schu S4-V]) components. The immunization of C57BL/6 mice with "bare" vesicles, which did not express F. tularensis components, partially protected against F. tularensis LVS, presumably through activation of the innate immune response, and yet it failed to protect against the F. tularensis Schu S4 strain. In contrast, immunization with LVS-V fully protected mice against intraperitoneal (i.p.) F. tularensis LVS challenge, while immunization of mice with either LVS-V or Schu S4-V partially protected C57BL/6 mice against an intranasal (i.n.) F. tularensis Schu S4 challenge and significantly increased the mean time to death for nonsurvivors, particularly following the i.n. and heterologous (i.e., i.p./i.n.) routes of immunization. LVS-V immunization, but not immunization with empty vesicles, elicited high levels of IgG against nonlipopolysaccharide (non-LPS) epitopes that were increased after F. tularensis LVS challenge and significantly increased early cytokine production. Antisera from LVS-V-immunized mice conferred passive protection against challenge with F. tularensis LVS. Together, these data indicate that functionalized catanionic surfactant vesicles represent an important and novel tool for the development of a safe and effective F. tularensis subunit vaccine and may be applicable for use with other pathogens.
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Chou AY, Kennett NJ, Nix EB, Schmerk CL, Nano FE, Elkins KL. Generation of protection against Francisella novicida in mice depends on the pathogenicity protein PdpA, but not PdpC or PdpD. Microbes Infect 2013; 15:816-27. [PMID: 23880085 DOI: 10.1016/j.micinf.2013.07.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 07/11/2013] [Accepted: 07/15/2013] [Indexed: 01/24/2023]
Abstract
Previous results suggest that mutations in most genes in the Francisella pathogenicity island (FPI) attenuate the bacterium. Using a mouse model, here we determined the impact of mutations in pdpA, pdpC, and pdpD in Francisella novicida on in vitro replication in macrophages, and in vivo immunogenicity. In contrast to most FPI genes, deletion of pdpC (FnΔpdpC) and pdpD (FnΔpdpD) from F. novicida did not impact growth in mouse bone-marrow derived macrophages. Nonetheless, both FnΔpdpC and FnΔpdpD were highly attenuated when administered intradermally. Infected mice produced relatively normal anti-F. novicida serum antibodies. Further, splenocytes from infected mice controlled intramacrophage Francisella replication, indicating T cell priming, and mice immunized by infection with FnΔpdpC or FnΔpdpD survived secondary lethal parenteral challenge with either F. novicida or Francisella tularensis LVS. In contrast, deletion of pdpA (FnΔpdpA) ablated growth in macrophages in vitro. FnΔpdpA disseminated and replicated poorly in infected mice, accompanied by development of some anti-F. novicida serum antibodies. However, primed Th1 cells were not detected, and vaccinated mice did not survive even low dose challenge with either F. novicida or LVS. Taken together, these results suggest that successful priming of Th1 cells, and protection against lethal challenge, depends on expression of PdpA.
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Affiliation(s)
- Alicia Y Chou
- Laboratory of Mycobacterial Diseases and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, 1401 Rockville Pike, HFM-431, Rockville, MD 20852, USA
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Dotson RJ, Rabadi SM, Westcott EL, Bradley S, Catlett SV, Banik S, Harton JA, Bakshi CS, Malik M. Repression of inflammasome by Francisella tularensis during early stages of infection. J Biol Chem 2013; 288:23844-57. [PMID: 23821549 DOI: 10.1074/jbc.m113.490086] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Francisella tularensis is an important human pathogen responsible for causing tularemia. F. tularensis has long been developed as a biological weapon and is now classified as a category A agent by the Centers for Disease Control because of its possible use as a bioterror agent. F. tularensis represses inflammasome; a cytosolic multi-protein complex that activates caspase-1 to produce proinflammatory cytokines IL-1β and IL-18. However, the Francisella factors and the mechanisms through which F. tularensis mediates these suppressive effects remain relatively unknown. Utilizing a mutant of F. tularensis in FTL_0325 gene, this study investigated the mechanisms of inflammasome repression by F. tularensis. We demonstrate that muted IL-1β and IL-18 responses generated in macrophages infected with F. tularensis live vaccine strain (LVS) or the virulent SchuS4 strain are due to a predominant suppressive effect on TLR2-dependent signal 1. Our results also demonstrate that FTL_0325 of F. tularensis impacts proIL-1β expression as early as 2 h post-infection and delays activation of AIM2 and NLRP3-inflammasomes in a TLR2-dependent fashion. An enhanced activation of caspase-1 and IL-1β observed in FTL_0325 mutant-infected macrophages at 24 h post-infection was independent of both AIM2 and NLRP3. Furthermore, F. tularensis LVS delayed pyroptotic cell death of the infected macrophages in an FTL_0325-dependent manner during the early stages of infection. In vivo studies in mice revealed that suppression of IL-1β by FTL_0325 early during infection facilitates the establishment of a fulminate infection by F. tularensis. Collectively, this study provides evidence that F. tularensis LVS represses inflammasome activation and that F. tularensis-encoded FTL_0325 mediates this effect.
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Affiliation(s)
- Rachel J Dotson
- Albany College of Pharmacy and Health Sciences, Albany, New York 12208, USA
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