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An extended catalogue of ncRNAs in Streptomyces coelicolor reporting abundant tmRNA, RNase-P RNA and RNA fragments derived from pre-ribosomal RNA leader sequences. Arch Microbiol 2022; 204:582. [PMID: 36042049 DOI: 10.1007/s00203-022-03203-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 08/05/2022] [Accepted: 08/18/2022] [Indexed: 11/02/2022]
Abstract
Streptomyces coelicolor is a model organism for studying streptomycetes. This genus possesses relevant medical and economical roles, because it produces many biologically active metabolites of pharmaceutical interest, including the majority of commercialized antibiotics. In this bioinformatic study, the transcriptome of S. coelicolor has been analyzed to identify novel RNA species and quantify the expression of both annotated and novel transcripts in solid and liquid growth medium cultures at different times. The major characteristics disclosed in this study are: (i) the diffuse antisense transcription; (ii) the great abundance of transfer-messenger RNAs (tmRNA); (iii) the abundance of rnpB transcripts, paramount for the RNase-P complex; and (iv) the presence of abundant fragments derived from pre-ribosomal RNA leader sequences of unknown biological function. Overall, this study extends the catalogue of ncRNAs in S. coelicolor and suggests an important role of non-coding transcription in the regulation of biologically active molecule production.
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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: 0] [Impact Index Per Article: 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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Kurtz SL, De Pascalis R, Meierovics AI, Elkins KL. Deficiency in CCR2 increases susceptibility of mice to infection with an intracellular pathogen, Francisella tularensis LVS, but does not impair development of protective immunity. PLoS One 2021; 16:e0249142. [PMID: 33760886 PMCID: PMC7990183 DOI: 10.1371/journal.pone.0249142] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 03/11/2021] [Indexed: 12/24/2022] Open
Abstract
CCR2 is the major chemokine receptor that regulates appropriate trafficking of inflammatory monocytes, but the role of this chemokine receptor and its ligands during primary and secondary infection with intracellular infections remains incompletely understood. Here we used murine infection with the Live Vaccine Strain (LVS) of Francisella tularensis to evaluate the role of CCR2 during primary and secondary parenteral responses to this prototype intracellular bacterium. We find that mice deficient in CCR2 are highly compromised in their ability to survive intradermal infection with LVS, indicating the importance of this receptor during primary parenteral responses. Interestingly, this defect could not be readily attributed to the activities of the known murine CCR2 ligands MCP-1/CCL2, MCP-3/CCL7, or MCP-5/CCL12. Nonetheless, CCR2 knockout mice vaccinated by infection with low doses of LVS generated optimal T cell responses that controlled the intramacrophage replication of Francisella, and LVS-immune CCR2 knockout mice survived maximal lethal Francisella challenge. Thus, fully protective adaptive immune memory responses to this intracellular bacterium can be readily generated in the absence of CCR2.
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Affiliation(s)
- Sherry L. Kurtz
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, United States of America
- * E-mail: (KLE); (SLK)
| | - Roberto De Pascalis
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, United States of America
| | - Anda I. Meierovics
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, United States of America
| | - Karen L. Elkins
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, United States of America
- * E-mail: (KLE); (SLK)
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Raasch M, Fritsche E, Kurtz A, Bauer M, Mosig AS. Microphysiological systems meet hiPSC technology - New tools for disease modeling of liver infections in basic research and drug development. Adv Drug Deliv Rev 2019; 140:51-67. [PMID: 29908880 DOI: 10.1016/j.addr.2018.06.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 06/01/2018] [Accepted: 06/12/2018] [Indexed: 02/08/2023]
Abstract
Complex cell culture models such as microphysiological models (MPS) mimicking human liver functionality in vitro are in the spotlight as alternative to conventional cell culture and animal models. Promising techniques like microfluidic cell culture or micropatterning by 3D bioprinting are gaining increasing importance for the development of MPS to address the needs for more predictivity and cost efficiency. In this context, human induced pluripotent stem cells (hiPSCs) offer new perspectives for the development of advanced liver-on-chip systems by recreating an in vivo like microenvironment that supports the reliable differentiation of hiPSCs to hepatocyte-like cells (HLC). In this review we will summarize current protocols of HLC generation and highlight recently established MPS suitable to resemble physiological hepatocyte function in vitro. In addition, we are discussing potential applications of liver MPS for disease modeling related to systemic or direct liver infections and the use of MPS in testing of new drug candidates.
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Sunagar R, Kumar S, Namjoshi P, Rosa SJ, Hazlett KRO, Gosselin EJ. Evaluation of an outbred mouse model for Francisella tularensis vaccine development and testing. PLoS One 2018; 13:e0207587. [PMID: 30533047 PMCID: PMC6289435 DOI: 10.1371/journal.pone.0207587] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 11/03/2018] [Indexed: 01/06/2023] 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 the tools to assess these vaccines. Tularemia laboratory research has historically relied primarily upon a small number of inbred mouse strains, but the utility of such findings to outbred animals may be limited. Specifically, C57BL/6 mice are more susceptible than BALB/c mice to Ft infection and less easily protected against challenge with highly virulent type A Ft. Thus, depending on the inbred mouse strain used, one could be misled as to which immunogen(s)/vaccine will ultimately be effective in an outbred human population. Accordingly, we evaluated an outbred Swiss Webster (SW) mouse model in direct comparison to a well-established, inbred C57BL/6 mouse model. Mucosal vaccination with the live, attenuated Ft LVS superoxide dismutase (sodB) mutant demonstrated significantly higher protection in outbred SW mice compared to inbred C57BL/6 mice against Ft SchuS4 respiratory challenge. The protection observed in vaccinated outbred mice correlated with lower bacterial density, reduced tissue inflammation, and reduced levels of pro-inflammatory cytokine production. This protection was CD4+ and CD8+ T cell-dependent and characterized by lower titers of serum antibody (Ab) that qualitatively differed from vaccinated inbred mice. Enhanced protection of vaccinated outbred mice correlated with early and robust production of IFN-γ and IL-17A. Neutralizing Ab administered at the time of challenge revealed that IFN-γ was central to this protection, while IL-17A neutralization did not alter bacterial burden or survival. The present study demonstrates the utility of the outbred mouse as an alternative vaccination model for testing tularemia vaccines. Given the limited MHC repertoire in inbred mice, this outbred model is more analogous to the human in terms of immunological diversity.
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Affiliation(s)
- Raju Sunagar
- Department of Immunology & Microbial Disease, Albany Medical College, Albany, NY, United States of America
| | - Sudeep Kumar
- Department of Immunology & Microbial Disease, Albany Medical College, Albany, NY, United States of America
| | - Prachi Namjoshi
- Department of Immunology & Microbial Disease, Albany Medical College, Albany, NY, United States of America
| | - Sarah J. Rosa
- Department of Immunology & Microbial Disease, Albany Medical College, Albany, NY, United States of America
| | - Karsten R. O. Hazlett
- Department of Immunology & Microbial Disease, Albany Medical College, Albany, NY, United States of America
| | - Edmund J. Gosselin
- Department of Immunology & Microbial Disease, Albany Medical College, Albany, NY, United States of America
- * E-mail:
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In Vivo Intradermal Delivery of Bacteria by Using Microneedle Arrays. Infect Immun 2018; 86:IAI.00406-18. [PMID: 29986891 DOI: 10.1128/iai.00406-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 06/19/2018] [Indexed: 01/23/2023] Open
Abstract
Infectious diseases propagated by arthropod vectors, such as tularemia, are commonly initiated via dermal infection of the skin. However, due to the technical difficulties in achieving accurate and reproducible dermal deposition, intradermal models are less commonly used. To overcome these limitations, we used microneedle arrays (MNAs), which are micron-scale polymeric structures, to temporarily disrupt the barrier function of the skin and deliver a bacterial inoculum directly to the dermis of an animal. MNAs increase reliability by eliminating leakage of the inoculum or blood from the injection site, thereby providing a biologically relevant model for arthropod-initiated disease. Here, we validate the use of MNAs as a means to induce intradermal infection using a murine model of tularemia initiated by Francisella novicida We demonstrate targeted delivery of the MNA bolus to the dermal layer of the skin, which subsequently led to innate immune cell infiltration. Additionally, F. novicida-coated MNAs were used to achieve lethality in a dose-dependent manner in C57BL/6 mice. The immune profile of infected mice mirrored that of established F. novicida infection models, consisting of markedly increased serum levels of interleukin-6 and keratinocyte chemoattractant, splenic T-cell depletion, and an increase in splenic granulocytes, together confirming that MNAs can be used to reproducibly induce tularemia-like pathogenesis in mice. When MNAs were used to immunize mice using an attenuated F. novicida mutant (F. novicida ΔlpxD1), all immunized mice survived a lethal subcutaneous challenge. Thus, MNAs can be used to effectively deliver viable bacteria in vivo and provide a novel avenue to study intradermally induced microbial diseases in animal models.
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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: 0.2] [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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Increased Resistance to Intradermal Francisella tularensis LVS Infection by Inactivation of the Sts Phosphatases. Infect Immun 2017. [PMID: 28630061 DOI: 10.1128/iai.00406-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Suppressor of TCR signaling proteins (Sts-1 and Sts-2) are two homologous phosphatases that negatively regulate signaling pathways in a number of hematopoietic lineages, including T lymphocytes. Mice lacking Sts expression are characterized by enhanced T cell responses. Additionally, a recent study demonstrated that Sts-/- mice are profoundly resistant to systemic infection by Candida albicans, with resistance characterized by enhanced survival, more rapid fungal clearance in key peripheral organs, and an altered inflammatory response. To investigate the role of Sts in the primary host response to infection by a bacterial pathogen, we evaluated the response of Sts-/- mice to infection by a Gram-negative bacterial pathogen. Francisella tularensis is a facultative bacterial pathogen that replicates intracellularly within a variety of cell types and is the causative agent of tularemia. Francisella infections are characterized by a delayed immune response, followed by an intense inflammatory reaction that causes widespread tissue damage and septic shock. Herein, we demonstrate that mice lacking Sts expression are significantly resistant to infection by the live vaccine strain (LVS) of F. tularensis Resistance is characterized by reduced lethality following high-dose intradermal infection, an altered cytokine response in the spleen, and enhanced bacterial clearance in multiple peripheral organs. Sts-/- bone marrow-derived monocytes and neutrophils, infected with F. tularensis LVS ex vivo, display enhanced restriction of intracellular bacteria. These observations suggest the Sts proteins play an important regulatory role in the host response to bacterial infection, and they underscore a role for Sts in regulating functionally relevant immune response pathways.
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Lampe EO, Tandberg JI, Rishovd AL, Winther-Larsen HC. Francisella noatunensis ssp. noatunensis iglC deletion mutant protects adult zebrafish challenged with acute mortality dose of wild-type strain. DISEASES OF AQUATIC ORGANISMS 2017; 123:123-140. [PMID: 28262634 DOI: 10.3354/dao03087] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The intracellular fish pathogen Francisella noatunensis remains an unsolved problem for aquaculture worldwide and an efficient vaccine is needed. In Francisella sp., IglC is an important virulence factor necessary for intracellular growth and escape from phagolysosomes. Deletion of the intracellular growth locus C (iglC) in Francisella sp. causes attenuation, but vaccine potential has only been attributed to ΔiglC from Francisella noatunensis ssp. orientalis, a warm-water fish pathogen. A ΔiglC mutant was constructed in the cold-water fish pathogen F. noatunensis ssp. noatunensis (Fnn), which causes francisellosis in Atlantic cod; the mutant was assessed in primary head kidney leucocytes from Atlantic cod. Fluorescence microscopy revealed reduced growth, while qPCR revealed an initial increase followed by a reduction in mutant genomes. Mutant-infected cod leucocytes presented higher interleukin 1 beta (il1β) and interleukin 8 (il8) transcription than wild-type (WT)-infected cells. Two doses of mutant and WT were tested in an adult zebrafish model whereupon 3 × 109 CFU caused acute disease and 3 × 107 CFU caused low mortality regardless of strain. However, splenomegaly developed only in the WT-infected zebrafish. Immunization with 7 × 106 CFU of Fnn ΔiglC protected zebrafish against challenge with a lethal dose of Fnn WT, and bacterial load was minimized within 28 d. Immunized fish had lower interleukin 6 (il6) and il8 transcription in kidney and prolonged interferon-gamma (ifng) transcription in spleens after challenge compared with non-immunized fish. Our data suggest an immunogenic potential of Fnn ΔiglC and indicate important cytokines associated with francisellosis pathogenesis and protection.
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Affiliation(s)
- Elisabeth O Lampe
- Center for Integrative Microbiology and Evolution, Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, 0316 Oslo, Norway
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Aloni-Grinstein R, Schuster O, Yitzhaki S, Aftalion M, Maoz S, Steinberger-Levy I, Ber R. Isolation of Francisella tularensis and Yersinia pestis from Blood Cultures by Plasma Purification and Immunomagnetic Separation Accelerates Antibiotic Susceptibility Determination. Front Microbiol 2017; 8:312. [PMID: 28293231 PMCID: PMC5329073 DOI: 10.3389/fmicb.2017.00312] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 02/15/2017] [Indexed: 01/16/2023] Open
Abstract
The early symptoms of tularemia and plague, which are caused by Francisella tularensis and Yersinia pestis infection, respectively, are common to other illnesses, resulting in a low index of suspicion among clinicians. Moreover, because these diseases can be treated only with antibiotics, rapid isolation of the bacteria and antibiotic susceptibility testing (AST) are preferable. Blood cultures of patients may serve as a source for bacteria isolation. However, due to the slow growth rates of F. tularensis and Y. pestis on solid media, isolation by plating blood culture samples on proper agar plates may require several days. Thus, improving the isolation procedure prior to antibiotic susceptibility determination is a major clinically relevant need. In this study, we developed a rapid, selective procedure for the isolation of F. tularensis and Y. pestis from blood cultures. We examined drop-plating and plasma purification followed by immunomagnetic separation (IMS) as alternative isolation methods. We determined that replacing the classical isolation method with drop-plating is advantageous with respect to time at the expense of specificity. Hence, we also examined isolation by IMS. Sub-localization of F. tularensis within blood cultures of infected mice has revealed that the majority of the bacteria are located within the extracellular fraction, in the plasma. Y. pestis also resides within the plasma. Therefore, the plasma fraction was isolated from blood cultures and subjected to an IMS procedure using polyclonal anti-F. tularensis live vaccine strain (LVS) or anti-Y. pestis antibodies conjugated to 50-nm nano-beads. The time required to reach an inoculum of sufficient bacteria for AST was shortest when using the plasma and IMSs for both bacteria, saving up to 2 days of incubation for F. tularensis and 1 day for Y. pestis. Our isolation procedure provides a proof of concept for the clinical relevance of rapid isolation for AST from F. tularensis- and Y. pestis-infected patients.
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Affiliation(s)
- Ronit Aloni-Grinstein
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological ResearchNess-Ziona, Israel
| | - Ofir Schuster
- Department of Infectious diseases, Israel Institute for Biological ResearchNess-Ziona, Israel
| | - Shmuel Yitzhaki
- Department of Infectious diseases, Israel Institute for Biological ResearchNess-Ziona, Israel
| | - Moshe Aftalion
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological ResearchNess-Ziona, Israel
| | - Sharon Maoz
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological ResearchNess-Ziona, Israel
| | - Ida Steinberger-Levy
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological ResearchNess-Ziona, Israel
| | - Raphael Ber
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological ResearchNess-Ziona, Israel
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Rennert K, Otto P, Funke H, Huber O, Tomaso H, Mosig AS. A human macrophage-hepatocyte co-culture model for comparative studies of infection and replication of Francisella tularensis LVS strain and subspecies holarctica and mediasiatica. BMC Microbiol 2016; 16:2. [PMID: 26739172 PMCID: PMC4704405 DOI: 10.1186/s12866-015-0621-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 12/29/2015] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Francisella tularensis, a gram-negative bacterium replicates intracellularly within macrophages and efficiently evades the innate immune response. It is able to infect and replicate within Kupffer cells, specialized tissue macrophages of the liver, and to modulate the immune response upon infection to its own advantage. Studies on Francisella tularensis liver infection were mostly performed in animal models and difficult to extrapolate to the human situation, since human infections and clinical observations are rare. RESULTS Using a human co-culture model of macrophages and hepatocytes we investigated the course of infection of three Francisella tularensis strains (subspecies holarctica--wildtype and live vaccine strain, and mediasiatica--wildtype) and analyzed the immune response triggered upon infection. We observed that hepatocytes support the intracellular replication of Franciscella species in macrophages accompanied by a specific immune response inducing TNFα, IL-1β, IL-6 and fractalkine (CX3CL1) secretion and the induction of apoptosis. CONCLUSIONS We could demonstrate that this human macrophage/hepatocyte co-culture model reflects strain-specific virulence of Francisella tularensis. We developed a suitable tool for more detailed in vitro studies on the immune response upon liver cell infection by F. tularensis.
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Affiliation(s)
- Knut Rennert
- Institute of Biochemistry II, Jena University Hospital, 07743, Jena, Germany.
| | - Peter Otto
- Institute of Bacterial Infections and Zoonoses (IBIZ), Friedrich-Loeffler-Institute, Federal Research Institute for Animal Health, 07743, Jena, Germany.
| | - Harald Funke
- Molecular Hemostaseology, Jena University Hospital, 07743, Jena, Germany.
| | - Otmar Huber
- Institute of Biochemistry II, Jena University Hospital, 07743, Jena, Germany. .,Center for Sepsis Control and Care, Jena University Hospital, Jena, 07747, Germany.
| | - Herbert Tomaso
- Institute of Bacterial Infections and Zoonoses (IBIZ), Friedrich-Loeffler-Institute, Federal Research Institute for Animal Health, 07743, Jena, Germany.
| | - Alexander S Mosig
- Institute of Biochemistry II, Jena University Hospital, 07743, Jena, Germany. .,Center for Sepsis Control and Care, Jena University Hospital, Jena, 07747, Germany.
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Hill TM, Gilchuk P, Cicek BB, Osina MA, Boyd KL, Durrant DM, Metzger DW, Khanna KM, Joyce S. Border Patrol Gone Awry: Lung NKT Cell Activation by Francisella tularensis Exacerbates Tularemia-Like Disease. PLoS Pathog 2015; 11:e1004975. [PMID: 26068662 PMCID: PMC4465904 DOI: 10.1371/journal.ppat.1004975] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 05/26/2015] [Indexed: 12/19/2022] Open
Abstract
The respiratory mucosa is a major site for pathogen invasion and, hence, a site requiring constant immune surveillance. The type I, semi-invariant natural killer T (NKT) cells are enriched within the lung vasculature. Despite optimal positioning, the role of NKT cells in respiratory infectious diseases remains poorly understood. Hence, we assessed their function in a murine model of pulmonary tularemia—because tularemia is a sepsis-like proinflammatory disease and NKT cells are known to control the cellular and humoral responses underlying sepsis. Here we show for the first time that respiratory infection with Francisella tularensis live vaccine strain resulted in rapid accumulation of NKT cells within the lung interstitium. Activated NKT cells produced interferon-γ and promoted both local and systemic proinflammatory responses. Consistent with these results, NKT cell-deficient mice showed reduced inflammatory cytokine and chemokine response yet they survived the infection better than their wild type counterparts. Strikingly, NKT cell-deficient mice had increased lymphocytic infiltration in the lungs that organized into tertiary lymphoid structures resembling induced bronchus-associated lymphoid tissue (iBALT) at the peak of infection. Thus, NKT cell activation by F. tularensis infection hampers iBALT formation and promotes a systemic proinflammatory response, which exacerbates severe pulmonary tularemia-like disease in mice. NKT cells are innate-like lymphocytes with a demonstrated role in a wide range of diseases. Often cited for their ability to rapidly produce a variety of cytokines upon activation, they have long been appreciated for their ability to “jump-start” the immune system and to shape the quality of both the innate and adaptive response. This understanding of their function has been deduced from in vitro experiments or through the in vivo administration of highly potent, chemically synthesized lipid ligands, which may not necessarily reflect a physiologically relevant response as observed in a natural infection. Using a mouse model of pulmonary tularemia, we report that intranasal infection with the live vaccine strain of F. tularensis rapidly activates NKT cells and promotes systemic inflammation, increased tissue damage, and a dysregulated immune response resulting in increased morbidity and mortality in infected mice. Our data highlight the detrimental effects of NKT cell activation and identify a potential new target for therapies against pulmonary tularemia.
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Affiliation(s)
- Timothy M. Hill
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Pavlo Gilchuk
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Veterans Administration Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Basak B. Cicek
- Department of Immunology, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - Maria A. Osina
- Department of Psychology and Human Development, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Kelli L. Boyd
- Veterans Administration Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Douglas M. Durrant
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, New York, United States of America
| | - Dennis W. Metzger
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, New York, United States of America
| | - Kamal M. Khanna
- Department of Immunology, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - Sebastian Joyce
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Veterans Administration Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
- * E-mail:
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13
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Steiner DJ, Furuya Y, Metzger DW. Host-pathogen interactions and immune evasion strategies in Francisella tularensis pathogenicity. Infect Drug Resist 2014; 7:239-51. [PMID: 25258544 PMCID: PMC4173753 DOI: 10.2147/idr.s53700] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Francisella tularensis is an intracellular Gram-negative bacterium that causes life-threatening tularemia. Although the prevalence of natural infection is low, F. tularensis remains a tier I priority pathogen due to its extreme virulence and ease of aerosol dissemination. F. tularensis can infect a host through multiple routes, including the intradermal and respiratory routes. Respiratory infection can result from a very small inoculum (ten organisms or fewer) and is the most lethal form of infection. Following infection, F. tularensis employs strategies for immune evasion that delay the immune response, permitting systemic distribution and induction of sepsis. In this review we summarize the current knowledge of F. tularensis in an immunological context, with emphasis on the host response and bacterial evasion of that response.
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Affiliation(s)
- Don J Steiner
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY, USA
| | - Yoichi Furuya
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY, USA
| | - Dennis W Metzger
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY, USA
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14
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Tacrine can suppress immune response to tularemia in BALB/c mouse model. J Appl Biomed 2013. [DOI: 10.2478/v10136-012-0021-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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15
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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: 43] [Impact Index Per Article: 3.9] [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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16
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Flick-Smith HC, Fox MA, Hamblin KA, Richards MI, Jenner DC, Laws TR, Phelps AL, Taylor C, Harding SV, Ulaeto DO, Atkins HS. Assessment of antimicrobial peptide LL-37 as a post-exposure therapy to protect against respiratory tularemia in mice. Peptides 2013; 43:96-101. [PMID: 23500517 DOI: 10.1016/j.peptides.2013.02.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 02/28/2013] [Accepted: 02/28/2013] [Indexed: 11/20/2022]
Abstract
Early activation of the innate immune response is important for protection against infection with Francisella tularensis live vaccine strain (LVS) in mice. The human cathelicidin antimicrobial peptide LL-37 is known to have immunomodulatory properties, and therefore exogenously administered LL-37 may be suitable as an early post-exposure therapy to protect against LVS infection. LL-37 has been evaluated for immunostimulatory activity in uninfected mice and for activity against LVS in macrophage assays and protective efficacy when administered post-challenge in a mouse model of respiratory tularemia. Increased levels of pro-inflammatory cytokine IL-6, chemokines monocyte chemoattractant protein 1 (MCP-1) and CXCL1 with increased neutrophil influx into the lungs were observed in uninfected mice after intranasal administration of LL-37. Following LVS challenge, LL-37 administration resulted in increased IL-6, IL-12 p70, IFNγ and MCP-1 production, a slowing of LVS growth in the lung, and a significant extension of mean time to death compared to control mice. However, protection was transient, with the LL-37 treated mice eventually succumbing to infection. As this short course of nasally delivered LL-37 was moderately effective at overcoming the immunosuppressive effects of LVS infection this suggests that a more sustained treatment regimen may be an effective therapy against this pathogen.
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Affiliation(s)
- Helen C Flick-Smith
- Biomedical Sciences Department, Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire SP4 0JQ, United Kingdom.
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17
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Identification of a live attenuated vaccine candidate for tularemia prophylaxis. PLoS One 2013; 8:e61539. [PMID: 23613871 PMCID: PMC3629233 DOI: 10.1371/journal.pone.0061539] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 03/11/2013] [Indexed: 12/25/2022] Open
Abstract
Francisella tularensis is the causative agent of a fatal human disease, tularemia. F. tularensis was used in bioweapon programs in the past and is now classified as a category A select agent owing to its possible use in bioterror attacks. Despite over a century since its discovery, an effective vaccine is yet to be developed. In this study four transposon insertion mutants of F. tularensis live vaccine strain (LVS) in Na/H antiporter (FTL_0304), aromatic amino acid transporter (FTL_0291), outer membrane protein A (OmpA)-like family protein (FTL_0325) and a conserved hypothetical membrane protein gene (FTL_0057) were evaluated for their attenuation and protective efficacy against F. tularensis SchuS4 strain. All four mutants were 100–1000 fold attenuated for virulence in mice than parental F. tularensis. Except for the FTL_0304, single intranasal immunization with the other three mutants provided 100% protection in BALB/c mice against intranasal challenge with virulent F. tularensis SchuS4. Differences in the protective ability of the FTL_0325 and FTL_0304 mutant which failed to provide protection against SchuS4 were investigated further. The results indicated that an early pro-inflammatory response and persistence in host tissues established a protective immunity against F. tularensis SchuS4 in the FTL_0325 immunized mice. No differences were observed in the levels of serum IgG antibodies amongst the two vaccinated groups. Recall response studies demonstrated that splenocytes from the FTL_0325 mutant immunized mice induced significantly higher levels of IFN-γ and IL-17 cytokines than the FTL_0304 immunized counterparts indicating development of an effective memory response. Collectively, this study demonstrates that persistence of the vaccine strain together with its ability to induce an early pro-inflammatory innate immune response and strong memory responses can discriminate between successful and failed vaccinations against tularemia. This study describes a live attenuated vaccine which may prove to be an ideal vaccine candidate for prevention of respiratory tularemia.
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18
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Kurtz SL, Foreman O, Bosio CM, Anver MR, Elkins KL. Interleukin-6 is essential for primary resistance to Francisella tularensis live vaccine strain infection. Infect Immun 2013; 81:585-97. [PMID: 23230288 PMCID: PMC3553820 DOI: 10.1128/iai.01249-12] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 12/03/2012] [Indexed: 11/20/2022] Open
Abstract
We employed Francisella tularensis live vaccine strain (LVS) to study mechanisms of protective immunity against intracellular pathogens and, specifically, to understand protective correlates. One potential molecular correlate identified previously was interleukin-6 (IL-6), a cytokine with pleotropic roles in immunity, including influences on T and B cell functions. Given its role as an immune modulator and the correlation with successful anti-LVS vaccination, we examined the role IL-6 plays in the host response to LVS. IL-6-deficient (IL-6 knockout [KO]) mice infected with LVS intradermally or intranasally or anti-IL-6-treated mice, showed greatly reduced 50% lethal doses compared to wild-type (WT) mice. Increased susceptibility was not due to altered splenic immune cell populations during infection or decreased serum antibody production, as IL-6 KO mice had similar compositions of each compared to WT mice. Although LVS-infected IL-6 KO mice produced much less serum amyloid A and haptoglobin (two acute-phase proteins) than WT mice, there were no other obvious pathophysiological differences between LVS-infected WT and IL-6 KO mice. IL-6 KO or WT mice that survived primary LVS infection also survived a high-dose LVS secondary challenge. Using an in vitro overlay assay that measured T cell activation, cytokine production, and abilities of primed splenocytes to control intracellular LVS growth, we found that IL-6 KO total splenocytes or purified T cells were slightly defective in controlling intracellular LVS growth but were equivalent in cytokine production. Taken together, IL-6 is an integral part of a successful immune response to primary LVS infection, but its exact role in precipitating adaptive immunity remains elusive.
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Affiliation(s)
- Sherry L. Kurtz
- 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, Rockville, Maryland, USA
| | - Oded Foreman
- The Jackson Laboratory, Sacramento, California, USA
| | - Catharine M. Bosio
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, NIAID, NIH, Hamilton, Montana, USA
| | - Miriam R. Anver
- Pathology/Histotechnology Laboratory, SAIC—Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Karen L. Elkins
- 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, Rockville, Maryland, USA
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19
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Genetic identification of unique immunological responses in mice infected with virulent and attenuated Francisella tularensis. Microbes Infect 2010; 13:261-75. [PMID: 21070859 DOI: 10.1016/j.micinf.2010.10.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Revised: 10/27/2010] [Accepted: 10/29/2010] [Indexed: 11/22/2022]
Abstract
Francisella tularensis is a category A select agent based on its infectivity and virulence but disease mechanisms in infection remain poorly understood. Murine pulmonary models of infection were therefore employed to assess and compare dissemination and pathology and to elucidate the host immune response to infection with the highly virulent Type A F. tularensis strain Schu4 versus the less virulent Type B live vaccine strain (LVS). We found that dissemination and pathology in the spleen was significantly greater in mice infected with F. tularensis Schu4 compared to mice infected with F. tularensis LVS. Using gene expression profiling to compare the response to infection with the two F. tularensis strains, we found that there were significant differences in the expression of genes involved in the apoptosis pathway, antigen processing and presentation pathways, and inflammatory response pathways in mice infected with Schu4 when compared to LVS. These transcriptional differences coincided with marked differences in dissemination and severity of organ lesions in mice infected with the Schu4 and LVS strains. Therefore, these findings indicate that altered apoptosis, antigen presentation and production of inflammatory mediators explain the differences in pathogenicity of F. tularensis Schu4 and LVS.
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20
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Bronchus-associated lymphoid tissue (BALT) and survival in a vaccine mouse model of tularemia. PLoS One 2010; 5:e11156. [PMID: 20585390 PMCID: PMC2886834 DOI: 10.1371/journal.pone.0011156] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2010] [Accepted: 05/27/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Francisella tularensis causes severe pulmonary disease, and nasal vaccination could be the ideal measure to effectively prevent it. Nevertheless, the efficacy of this type of vaccine is influenced by the lack of an effective mucosal adjuvant. METHODOLOGY/PRINCIPAL FINDINGS Mice were immunized via the nasal route with lipopolysaccharide isolated from F. tularensis and neisserial recombinant PorB as an adjuvant candidate. Then, mice were challenged via the same route with the F. tularensis attenuated live vaccine strain (LVS). Mouse survival and analysis of a number of immune parameters were conducted following intranasal challenge. Vaccination induced a systemic antibody response and 70% of mice were protected from challenge as showed by their improved survival and weight regain. Lungs from mice recovering from infection presented prominent lymphoid aggregates in peribronchial and perivascular areas, consistent with the location of bronchus-associated lymphoid tissue (BALT). BALT areas contained proliferating B and T cells, germinal centers, T cell infiltrates, dendritic cells (DCs). We also observed local production of antibody generating cells and homeostatic chemokines in BALT areas. CONCLUSIONS These data indicate that PorB might be an optimal adjuvant candidate for improving the protective effect of F. tularensis antigens. The presence of BALT induced after intranasal challenge in vaccinated mice might play a role in regulation of local immunity and long-term protection, but more work is needed to elucidate mechanisms that lead to its formation.
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21
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Gregory SH, Chen WH, Mott S, Palardy JE, Parejo NA, Heninger S, Anderson CA, Artenstein AW, Opal SM, Cross AS. Detoxified endotoxin vaccine (J5dLPS/OMP) protects mice against lethal respiratory challenge with Francisella tularensis SchuS4. Vaccine 2010; 28:2908-15. [PMID: 20170768 DOI: 10.1016/j.vaccine.2010.01.067] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 12/23/2009] [Accepted: 01/10/2010] [Indexed: 10/19/2022]
Abstract
Francisella tularensis is a category A select agent. J5dLPS/OMP is a novel vaccine construct consisting of detoxified, O-polysaccharide side chain-deficient, lipopolysaccharide non-covalently complexed with the outer membrane protein of N. meningitidis group B. Immunization elicits high-titer polyclonal antibodies specific for the highly-conserved epitopes expressed within the glycolipid core that constitutes gram-negative bacteria (e.g., F. tularensis). Mice immunized intranasally with J5dLPS/OMP exhibited protective immunity to intratracheal challenge with the live vaccine strain, as well as the highly-virulent SchuS4 strain, of F. tularensis. The efficacy of J5dLPS/OMP vaccine suggests its potential utility in immunizing the general population against several different gram-negative select agents concurrently.
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Affiliation(s)
- Stephen H Gregory
- Department of Medicine, Rhode Island Hospital and The Warren Alpert Medical School of Brown University, 55 Claverick Street, Providence, RI 02903, USA.
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22
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Oyston PCF, Griffiths R. Francisella virulence: significant advances, ongoing challenges and unmet needs. Expert Rev Vaccines 2010; 8:1575-85. [PMID: 19863250 DOI: 10.1586/erv.09.114] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Francisella tularensis, the causative agent of tularemia, is an organism of concern as a potential biowarfare agent. Progress towards understanding the molecular basis of pathogenicity has been hampered by a lack of tools with which to manipulate the pathogen. However, the availability of genome sequence data for a range of strains and the development of a range of plasmids and mutagenesis protocols for use in Francisella has resulted in a huge advance in understanding. No licensed vaccine is yet available. Various approaches towards a new vaccine are being evaluated, but novel adjuvants and delivery systems are needed to induce the complex response required for immunity. Better animal models to more accurately represent human responses to infection are also required.
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23
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Elkins KL, Colombini SM, Meierovics AI, Chu MC, Chou AY, Cowley SC. Survival of secondary lethal systemic Francisella LVS challenge depends largely on interferon gamma. Microbes Infect 2010; 12:28-36. [DOI: 10.1016/j.micinf.2009.09.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Revised: 06/06/2009] [Accepted: 09/17/2009] [Indexed: 11/26/2022]
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24
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Aged mice display an altered pulmonary host response to Francisella tularensis live vaccine strain (LVS) infections. Exp Gerontol 2009; 45:91-6. [PMID: 19825409 DOI: 10.1016/j.exger.2009.10.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 08/27/2009] [Accepted: 10/06/2009] [Indexed: 11/19/2022]
Abstract
Aging is a complex phenomenon that has been shown to affect many organ systems including the innate and adaptive immune systems. The current study was designed to examine the potential effect of immunosenescence on the pulmonary immune response using a Francisella tularensis live vaccine strain (LVS) inhalation infection model. F. tularensis is a Gram-negative intracellular pathogen that can cause a severe pneumonia. In this study both young (8-12 week old) and aged (20-24 month old) mice were infected intranasally with LVS. Lung tissues from young and aged mice were used to assess pathology, recruitment of immune cell types and cytokine expression levels at various times post infection. Bacterial burdens were also assessed. Interestingly, the lungs of aged animals harbored fewer organisms at early time points of infection (day 1, day 3) compared with their younger counterparts. In addition, only aged animals displayed small perivascular aggregates at these early time points that appeared mostly mononuclear in nature. However, the kinetics of infiltrating polymorphonuclear neutrophils (PMNs) and increased cytokine levels measured in the bronchial alveolar lavage fluid (BALF) were delayed in infected aged animals relative to young infected animals with neutrophils appearing at day 5 post infection (PI) in the aged animals as opposed to day 3 PI in the young infected animals. Also evident were alterations in the ratios of mononuclear to PMNs at distinct post infection times. The above evidence indicates that aged mice elicit an altered immune response in the lung to respiratory F. tularensis LVS infections compared to their younger counterparts.
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25
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Sharma J, Li Q, Mishra BB, Pena C, Teale JM. Lethal pulmonary infection with Francisella novicida is associated with severe sepsis. J Leukoc Biol 2009; 86:491-504. [PMID: 19401387 PMCID: PMC2735285 DOI: 10.1189/jlb.1208728] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 02/23/2009] [Accepted: 03/02/2009] [Indexed: 11/24/2022] Open
Abstract
The bacterial or host determinants of lethality associated with respiratory Francisella infections are currently unknown. No exo- or endotoxins that contribute to the severity of this disease have been identified. However, a deregulated host immune response upon infection is characterized by an initial 36- to 48-h delay followed by a rapid and excessive inflammatory response prior to death at 72-120 h. Here, we extend these findings by comparing host immune responses between sublethal and lethal respiratory infections of mice with an attenuated transposon mutant (Mut) of F. novicida (F.n.) strain U112 (sublethal) versus the wild-type (WT) strain (lethal). Infection with WT bacteria, but not the Mut, was characterized by sustained bacteremia and systemic dissemination of the pathogen with temporal increases in bacterial burdens in liver and spleen. Severe pathology with large foci of infiltrates associated with extensive tissue damage was evident in WT-infected lungs, and Mut-infected mice displayed much reduced pathology with intact lung architecture. Similar to other experimental models of severe sepsis, WT- but not the Mut-infected mice exhibited a robust increase in numbers of Gr1+ and CD11b+ cells, while displaying a significant depletion of alphabeta T cells. Further, a dramatic up-regulation of multiple cytokines and chemokines was observed only in lethal WT infection. In addition, an earlier and larger increased expression of S100A9, a known mediator of sepsis, was observed in WT-infected mice. Taken together, these results show that a hyperinflammatory host immune response, culminating in severe sepsis, is responsible for the lethal outcome of respiratory tularemia.
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Affiliation(s)
- Jyotika Sharma
- South Texas Center for Emerging Diseases and Department of Biology, University of Texas at San Antonio, San Antonio, Texas 78249-1644, USA
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26
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Vaccination with an attenuated strain of Francisella novicida prevents T-cell depletion and protects mice infected with the wild-type strain from severe sepsis. Infect Immun 2009; 77:4314-26. [PMID: 19635830 DOI: 10.1128/iai.00654-09] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Francisella tularensis is the causative agent of zoonotic tularemia, a severe pneumonia in humans, and Francisella novicida causes a similarly severe tularemia in mice upon inhalation. The correlates of protective immunity, as well as the virulence mechanisms of this deadly pathogen, are not well understood. In the present study, we compared the host immune responses of lethally infected and vaccinated mice to highlight the host determinants of protection from this disease. Intranasal infection with an attenuated mutant (Mut) of F. novicida lacking a 58-kDa hypothetical protein protected C57BL/6 mice from a subsequent challenge with the fully virulent wild-type strain U112 via the same route. The protection conferred by Mut vaccination was associated with reduced bacterial burdens in systemic organs, as well as the absence of bacteremia. Also, there was reduced lung pathology and associated cell death in the lungs of vaccinated mice. Both vaccinated and nonvaccinated mice displayed an initial 2-day delay in upregulation of signature inflammatory mediators after challenge. Whereas the nonvaccinated mice developed severe sepsis characterized by hypercytokinemia and T-cell depletion, the vaccinated mice displayed moderated cytokine induction and contained increased numbers of alphabeta T cells. The recall response in vaccinated mice consisted of a characteristic Th1-type response in terms of cytokines, as well as antibody isotypes. Our results show that a regulated Th1 type of cell-mediated and humoral immunity in the absence of severe sepsis is associated with protection from respiratory tularemia, whereas a deregulated host response leading to severe sepsis contributes to mortality.
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27
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Gregory SH, Mott S, Phung J, Lee J, Moise L, McMurry JA, Martin W, De Groot AS. Epitope-based vaccination against pneumonic tularemia. Vaccine 2009; 27:5299-306. [PMID: 19616492 DOI: 10.1016/j.vaccine.2009.06.101] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 06/23/2009] [Accepted: 06/30/2009] [Indexed: 10/20/2022]
Abstract
Francisella tularensis, the etiological agent of tularemia, is one of the most infectious bacterial pathogens known. No vaccine is currently approved for public use. Previously, we identified epitopes recognized specifically by T cells obtained from individuals following infection with F. tularensis. Here, we report that a subunit vaccine constructed based upon these epitopes elicited protective immunity in "humanized" HLA class II (DRB1*0401) transgenic mice. Vaccinated mice challenged intratracheally with a lethal dose of F. tularensis (Live Vaccine Strain) exhibited a rapid increase in pro-inflammatory cytokine production and diminished number of organisms in the lungs, and a concurrent increased rate of survival. These results demonstrate the efficacy of an epitope-based tularemia vaccine and suggest that such an approach might be widely applicable to the development of vaccines specific for intracellular bacterial pathogens.
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Affiliation(s)
- Stephen H Gregory
- Rhode Island Hospital and The Warren Alpert Medical School of Brown University, Providence, RI, United States.
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28
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Sharma J, Li Q, Mishra BB, Teale JM. Lethal pulmonary infection with Francisella novicida causes depletion of alphabeta T cells from lungs. Cell Immunol 2009; 257:1-4. [PMID: 19356746 DOI: 10.1016/j.cellimm.2009.03.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Revised: 03/11/2009] [Accepted: 03/12/2009] [Indexed: 11/25/2022]
Abstract
Respiratory Francisella infections induce a delayed innate immune response followed by a severe sepsis like condition. In this study, mice infected intranasally with Francisella novicida showed a depletion of alphabeta T cells in lungs while exhibiting large accumulations of other leukocytes correlating with disease severity. The depleted T cells were predominantly CD4(+). The alphabeta T cells in infected mice showed significantly higher levels of Annexin V binding than those in mock control mice suggesting increased apoptosis of T cells. These results suggest that lack of transition from an innate to adaptive host response is associated with lethality of respiratory tularemia.
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Affiliation(s)
- Jyotika Sharma
- Department of Biology, South Texas Center for Emerging Diseases, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249-1644, USA
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29
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Moreland JG, Hook JS, Bailey G, Ulland T, Nauseef WM. Francisella tularensis directly interacts with the endothelium and recruits neutrophils with a blunted inflammatory phenotype. Am J Physiol Lung Cell Mol Physiol 2009; 296:L1076-84. [PMID: 19346432 DOI: 10.1152/ajplung.90332.2008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Francisella tularensis, the causative agent of tularemia, is a highly virulent organism, especially when exposure occurs by inhalation. Recent data suggest that Francisella interacts directly with alveolar epithelial cells. Although F. tularensis causes septicemia and can live extracellularly in a murine infection model, there is little information about the role of the vascular endothelium in the host response. We hypothesized that F. tularensis would interact with pulmonary endothelial cells as a prerequisite to the clinically observed recruitment of neutrophils to the lung. Using an in vitro Transwell model system, we studied interactions between F. tularensis live vaccine strain (Ft LVS) and a pulmonary microvascular endothelial cell (PMVEC) monolayer. Organisms invaded the endothelium and were visualized within individual endothelial cells by confocal microscopy. Although these bacteria-endothelial cell interactions did not elicit production of the proinflammatory chemokines, polymorphonuclear leukocytes (PMN) were stimulated to transmigrate across the endothelium in response to Ft LVS. Moreover, transendothelial migration altered the phenotype of recruited PMN; i.e., the capacity of these PMN to activate NADPH oxidase and release elastase in response to subsequent stimulation was reduced compared with PMN that traversed PMVEC in response to Streptococcus pneumoniae. The blunting of PMN responsiveness required PMN transendothelial migration but did not require PMN uptake of Ft LVS, was not dependent on the presence of serum-derived factors, and was not reproduced by Ft LVS-conditioned medium. We speculate that the capacity of Ft LVS-stimulated PMVEC to support transendothelial migration of PMN without triggering release of IL-8 and monocyte chemotactic protein-1 and to suppress the responsiveness of transmigrated PMN to subsequent stimulation could contribute to the dramatic virulence during inhalational challenge with Francisella.
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Affiliation(s)
- Jessica G Moreland
- Dept. of Pediatrics, Division of Pediatric Critical Care, 200 Hawkins Dr./2JCP, Iowa City, IA 52242, USA.
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Hu Y, Coates ARM. Acute and persistent Mycobacterium tuberculosis infections depend on the thiol peroxidase TpX. PLoS One 2009; 4:e5150. [PMID: 19340292 PMCID: PMC2659749 DOI: 10.1371/journal.pone.0005150] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 03/09/2009] [Indexed: 12/03/2022] Open
Abstract
The macrophage is the natural niche of Mycobacterium tuberculosis infection. In order to combat oxidative and nitrosative stresses and persist in macrophages successfully, M. tuberculosis is endowed with a very efficient antioxidant complex. Amongst these antioxidant enzymes, TpX is the only one in M. tuberculosis with sequence homology to thiol peroxidase. Previous reports have demonstrated that the M. tuberculosis TpX protein functions as a peroxidase in vitro. It is the dominant antioxidant which protects M. tuberculosis against oxidative and nitrosative stresses. The level of the protein increases in oxidative stress. To determine the roles of tpx gene in M. tuberculosis survival and virulence in vivo, we constructed an M. tuberculosis strain lacking the gene. The characteristics of the mutant were examined in an in vitro stationary phase model, in response to stresses; in murine bone marrow derived macrophages and in an acute and an immune resistant model of murine tuberculosis. The tpx mutant became sensitive to H2O2 and NO compared to the wild type strain. Enzymatic analysis using bacterial extracts from the WT and the tpx mutant demonstrated that the mutant contains reduced peroxidase activity. As a result of this, the mutant failed to grow and survive in macrophages. The growth deficiency in macrophages became more pronounced after interferon-γ activation. In contrast, its growth was significantly restored in the macrophages of inducible nitric oxide synthase (iNOS or NOS2) knockout mice. Moreover, the tpx mutant was impaired in its ability to initiate an acute infection and to maintain a persistent infection. Its virulence was attenuated. Our results demonstrated that tpx is required for M. tuberculosis to deal with oxidative and nitrosative stresses, to survive in macrophages and to establish acute and persistent infections in animal tuberculosis models.
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Affiliation(s)
- Yanmin Hu
- Centre of Infection, Division of Cellular and Molecular Medicine, St George's University of London, London, United Kingdom
| | - Anthony R. M. Coates
- Centre of Infection, Division of Cellular and Molecular Medicine, St George's University of London, London, United Kingdom
- * E-mail:
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Ojeda SS, Wang ZJ, Mares CA, Chang TA, Li Q, Morris EG, Jerabek PA, Teale JM. Rapid dissemination of Francisella tularensis and the effect of route of infection. BMC Microbiol 2008; 8:215. [PMID: 19068128 PMCID: PMC2651876 DOI: 10.1186/1471-2180-8-215] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Accepted: 12/09/2008] [Indexed: 12/14/2022] Open
Abstract
Background Francisella tularensis subsp. tularensis is classified as a Category A bioweapon that is capable of establishing a lethal infection in humans upon inhalation of very few organisms. However, the virulence mechanisms of this organism are not well characterized. Francisella tularensis subsp. novicida, which is an equally virulent subspecies in mice, was used in concert with a microPET scanner to better understand its temporal dissemination in vivo upon intranasal infection and how such dissemination compares with other routes of infection. Adult mice were inoculated intranasally with F. tularensis subsp. novicida radiolabeled with 64Cu and imaged by microPET at 0.25, 2 and 20 hours post-infection. Results 64Cu labeled F. tularensis subsp. novicida administered intranasally or intratracheally were visualized in the respiratory tract and stomach at 0.25 hours post infection. By 20 hours, there was significant tropism to the lung compared with other tissues. In contrast, the images of radiolabeled F. tularensis subsp. novicida when administered intragastrically, intradermally, intraperitoneally and intravenouslly were more generally limited to the gastrointestinal system, site of inoculation, liver and spleen respectively. MicroPET images correlated with the biodistribution of isotope and bacterial burdens in analyzed tissues. Conclusion Our findings suggest that Francisella has a differential tissue tropism depending on the route of entry and that the virulence of Francisella by the pulmonary route is associated with a rapid bacteremia and an early preferential tropism to the lung. In addition, the use of the microPET device allowed us to identify the cecum as a novel site of colonization of Francisella tularensis subsp. novicida in mice.
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Affiliation(s)
- Sandra S Ojeda
- Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
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Host immune response and acute disease in a zebrafish model of Francisella pathogenesis. Infect Immun 2008; 77:914-25. [PMID: 19047404 DOI: 10.1128/iai.01201-08] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Members of the bacterial genus Francisella are highly virulent and infectious pathogens. New models to study Francisella pathogenesis in evolutionarily distinct species are needed to provide comparative insight, as the mechanisms of host resistance and pathogen virulence are not well understood. We took advantage of the recent discovery of a novel species of Francisella to establish a zebrafish/Francisella comparative model of pathogenesis and host immune response. Adult zebrafish were susceptible to acute Francisella-induced disease and suffered mortality in a dose-dependent manner. Using immunohistochemical analysis, we localized bacterial antigens primarily to lymphoid tissues and livers of zebrafish following infection by intraperitoneal injection, which corresponded to regions of local cellular necrosis. Francisella sp. bacteria replicated rapidly in these tissues beginning 12 h postinfection, and bacterial titers rose steadily, leveled off, and then decreased by 7 days postinfection. Zebrafish mounted a significant tissue-specific proinflammatory response to infection as measured by the upregulation of interleukin-1beta (IL-1beta), gamma interferon, and tumor necrosis factor alpha mRNA beginning by 6 h postinfection and persisting for up to 7 days postinfection. In addition, exposure of zebrafish to heat-killed bacteria demonstrated that the significant induction of IL-1beta was highly specific to live bacteria. Taken together, the pathology and immune response to acute Francisella infection in zebrafish share many features with those in mammals, highlighting the usefulness of this new model system for addressing both general and specific questions about Francisella host-pathogen interactions via an evolutionary approach.
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Bakshi CS, Malik M, Mahawar M, Kirimanjeswara GS, Hazlett KRO, Palmer LE, Furie MB, Singh R, Melendez JA, Sellati TJ, Metzger DW. An improved vaccine for prevention of respiratory tularemia caused by Francisella tularensis SchuS4 strain. Vaccine 2008; 26:5276-88. [PMID: 18692537 DOI: 10.1016/j.vaccine.2008.07.051] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Revised: 07/14/2008] [Accepted: 07/15/2008] [Indexed: 11/29/2022]
Abstract
Vaccination of mice with Francisella tularensis live vaccine strain (LVS) mutants described so far have failed to induce protection in C57BL/6 mice against challenge with the virulent strain F. tularensis SchuS4. We have previously reported that a mutant of F. tularensis LVS deficient in iron superoxide dismutase (sodB(Ft)) is hypersensitive to oxidative stress and attenuated for virulence in mice. Herein, we evaluated the efficacy of this mutant as a vaccine candidate against respiratory tularemia caused by F. tularensis SchuS4. C57BL/6 mice were vaccinated intranasally (i.n.) with the sodB(Ft) mutant and challenged i.n. with lethal doses of F. tularensis SchuS4. The level of protection against SchuS4 challenge was higher in sodB(Ft) vaccinated group as compared to the LVS vaccinated mice. sodB(Ft) vaccinated mice following SchuS4 challenge exhibited significantly reduced bacterial burden in lungs, liver and spleen, regulated production of pro-inflammatory cytokines and less severe histopathological lesions compared to the LVS vaccinated mice. The sodB(Ft) vaccination induced a potent humoral immune response and protection against SchuS4 required both CD4 and CD8 T cells in the vaccinated mice. sodB(Ft) mutants revealed upregulated levels of chaperonine proteins DnaK, GroEL and Bfr that have been shown to be important for generation of a potent immune response against Francisella infection. Collectively, this study describes an improved live vaccine candidate against respiratory tularemia that has an attenuated virulence and enhanced protective efficacy than the LVS.
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Affiliation(s)
- Chandra Shekhar Bakshi
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY 12208, USA.
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Neisseria meningitidis PorB, a Toll-like receptor 2 ligand, improves the capacity of Francisella tularensis lipopolysaccharide to protect mice against experimental tularemia. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2008; 15:1322-9. [PMID: 18614668 DOI: 10.1128/cvi.00125-08] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Francisella tularensis causes severe pneumonia that can be fatal if it is left untreated. Due to its potential use as a biological weapon, research is being conducted to develop an effective vaccine and to select and study adjuvant molecules able to generate a better and long-lasting protective effect. PorB, a porin from Neisseria meningitidis, is a well-established Toll-like receptor 2 ligand and has been shown to be a promising vaccine adjuvant candidate due to its ability to enhance the T-cell costimulatory activity of antigen-presenting cells both in vitro and in vivo. BALB/c mice were immunized with lipopolysaccharide (LPS) isolated from the F. tularensis subsp. holarctica live vaccine strain (LVS), with or without PorB from N. meningitidis, and the antibody levels induced during the vaccination regimen and the level of protection against intranasal challenge with LVS were determined. Antigen administered alone induced a specific F. tularensis LPS immunoglobulin M (IgM) response that was not maintained over the weeks and that conferred protection to only 25% of the mice. In contrast, F. tularensis LPS given in combination with neisserial PorB induced consistent levels of specific IgM throughout the immunization and increased the proportion of surviving mice to 70%. Postchallenge cytokine analysis showed that interleukin-6 (IL-6), monocyte chemoattractant protein 1, and gamma interferon were markers of mortality and that IL-1beta was a correlate of survival, independent of the presence of PorB as an adjuvant. These data indicate that neisserial PorB might be an optimal candidate adjuvant for improving the protective effect of F. tularensis LPS and other subunit vaccines against tularemia, but there is still a need to test its efficacy against virulent type A and type B F. tularensis strains.
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Cole LE, Santiago A, Barry E, Kang TJ, Shirey KA, Roberts ZJ, Elkins KL, Cross AS, Vogel SN. Macrophage proinflammatory response to Francisella tularensis live vaccine strain requires coordination of multiple signaling pathways. THE JOURNAL OF IMMUNOLOGY 2008; 180:6885-91. [PMID: 18453609 DOI: 10.4049/jimmunol.180.10.6885] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The macrophage proinflammatory response to Francisella tularensis (Ft) live vaccine strain (LVS) was shown previously to be TLR2 dependent. The observation that intracellular Ft LVS colocalizes with TLR2 and MyD88 inside macrophages suggested that Ft LVS might signal from within the phagosome. Macrophages infected with LVSDeltaiglC, a Ft LVS mutant that fails to escape from the phagosome, displayed greatly increased expression of a subset of TLR2-dependent, proinflammatory genes (e.g., Tnf) but decreased expression of others (e.g., Ifnb1). This latter subset was similarly mitigated in IFN-beta(-/-) macrophages indicating that while Ft LVS-induced TLR2 signaling is necessary, cytosolic sensing of Ft to induce IFN-beta is required for full induction of the macrophage proinflammatory response. Although LVSDeltaiglC greatly increased IL-1beta mRNA in wild-type macrophages, protein secretion was not observed. IL-1beta secretion was also diminished in Ft LVS-infected IFN-beta(-/-) macrophages. rIFN-beta failed to restore IL-1beta secretion in LVSDeltaiglC-infected macrophages, suggesting that signals in addition to IFN-beta are required for assembly of the inflammasome and activation of caspase-1. IFN-beta plays a central role in controlling the macrophage bacterial burden: bacterial recovery was greater in IFN-beta(-/-) than in wild-type macrophages and treatment of Ft LVS-infected macrophages with rIFN-beta or 5,6-dimethylxanthenone-4-acetic acid, a potent IFN-beta inducer, greatly decreased the intracellular Ft LVS burden. In toto, these observations support the hypothesis that the host inflammatory response to Ft LVS is complex and requires engagement of multiple signaling pathways downstream of TLR2 including production of IFN-beta via an unknown cytosolic sensor and activation of the inflammasome.
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Affiliation(s)
- Leah E Cole
- Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
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