scholarly journals TolC-Dependent Modulation of Host Cell Death by the Francisella tularensis Live Vaccine Strain

2014 ◽  
Vol 82 (5) ◽  
pp. 2068-2078 ◽  
Author(s):  
Christopher R. Doyle ◽  
Ji-An Pan ◽  
Patricio Mena ◽  
Wei-Xing Zong ◽  
David G. Thanassi
Keyword(s):  
Cell Death ◽  
Immune Responses ◽  
Host Cell ◽  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Live Vaccine ◽  
Live Vaccine Strain ◽  
Type I ◽  
Content Type ◽  
Host Cell Death

ABSTRACTFrancisella tularensisis a facultative intracellular, Gram-negative pathogen and the causative agent of tularemia. We previously identified TolC as a virulence factor of theF. tularensislive vaccine strain (LVS) and demonstrated that a ΔtolCmutant exhibits increased cytotoxicity toward host cells and elicits increased proinflammatory responses compared to those of the wild-type (WT) strain. TolC is the outer membrane channel component used by the type I secretion pathway to export toxins and other bacterial virulence factors. Here, we show that the LVS delays activation of the intrinsic apoptotic pathway in a TolC-dependent manner, both during infection of primary macrophages and during organ colonization in mice. The TolC-dependent delay in host cell death is required forF. tularensisto preserve its intracellular replicative niche. We demonstrate that TolC-mediated inhibition of apoptosis is an active process and not due to defects in the structural integrity of the ΔtolCmutant. These findings support a model wherein the immunomodulatory capacity ofF. tularensisrelies, at least in part, on TolC-secreted effectors. Finally, mice vaccinated with the ΔtolCLVS are protected from lethal challenge and clear challenge doses faster than WT-vaccinated mice, demonstrating that the altered host responses to primary infection with the ΔtolCmutant led to altered adaptive immune responses. Taken together, our data demonstrate that TolC is required for temporal modulation of host cell death during infection byF. tularensisand highlight how shifts in the magnitude and timing of host innate immune responses may lead to dramatic changes in the outcome of infection.

scholarly journals Diverse Myeloid and Lymphoid Cell Subpopulations Produce Gamma Interferon during Early Innate Immune Responses to Francisella tularensis Live Vaccine Strain

2008 ◽  
Vol 76 (9) ◽  
pp. 4311-4321 ◽  
Author(s):  
Roberto De Pascalis ◽  
Betsy C. Taylor ◽  
Karen L. Elkins
Keyword(s):  
T Cells ◽  
Immune Responses ◽  
Nk Cells ◽  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Live Vaccine ◽  
Innate Immune ◽  
Live Vaccine Strain ◽  
Ifn Γ ◽  
Cell Subpopulations

ABSTRACT Francisella tularensis, a small gram-negative intracellular bacterium responsible for causing tularemia, is highly pathogenic and classified as a category A agent of bioterrorism. As for other intracellular pathogens, successful protective immune responses to Francisella tularensis require rapid and efficient induction of gamma interferon (IFN-γ) production. Studies using intracellular bacteria such as Listeria monocytogenes as well as Francisella suggest that natural killer (NK) and T cells are important sources of IFN-γ. However, comprehensive characterization of specific sources of IFN-γ produced during Francisella infection in vivo remains incomplete, and depletion of NK cells before infection of mice with the F. tularensis live vaccine strain (LVS) has little impact on the course or outcome of infection. In this study, we determined the cell subpopulations that respond quickly to intradermal F. tularensis LVS infection of mice by producing IFN-γ within hours to a few days. Splenic and liver lymphocytes were obtained from LVS-infected mice and analyzed for IFN-γ mRNA by reverse transcription-PCR, for intracellular cytokine expression by multiparameter flow cytometry, and for ex vivo production of IFN-γ protein by enzyme-linked immunosorbent assay. Cells producing IFN-γ were readily detectable by day 3 after infection, and numbers progressively increased through days 5 to 7. Importantly, the cell types responsible for IFN-γ production were much more varied than expected: these included not only NK cells and T cells, which might be predicted, but also other cells, including dendritic cells (DCs), “NK DCs,” NK T cells, and neutrophils. Most importantly, since RAG-1 knockout mice appeared to exhibit a frequency of IFN-γ-producing cells comparable to that of intact wild-type mice, early IFN-γ production by innate immune cells does not depend on the presence of T or B cells.

scholarly journals Transcriptome analysis of human immune responses following live vaccine strain (LVS) Francisella tularensis vaccination

2007 ◽  
Vol 44 (12) ◽  
pp. 3173-3184 ◽  
Author(s):  
Claudette L. Fuller ◽  
Katherine C. Brittingham ◽  
Mark W. Porter ◽  
Matthew J. Hepburn ◽  
Patricia L. Petitt ◽  
...  
Keyword(s):  
Immune Responses ◽  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Transcriptome Analysis ◽  
Live Vaccine ◽  
Live Vaccine Strain ◽  
Human Immune

Dominance of human innate immune responses in primary Francisella tularensis live vaccine strain vaccination

2006 ◽  
Vol 117 (5) ◽  
pp. 1186-1188 ◽  
Author(s):  
Claudette L. Fuller ◽  
Katherine C. Brittingham ◽  
Matthew J. Hepburn ◽  
James W. Martin ◽  
Patricia L. Petitt ◽  
...  
Keyword(s):  
Immune Responses ◽  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Live Vaccine ◽  
Innate Immune ◽  
Live Vaccine Strain ◽  
Innate Immune Responses

scholarly journals Francisella tularensis Live Vaccine Strain Folate Metabolism and Pseudouridine Synthase Gene Mutants Modulate Macrophage Caspase-1 Activation

2012 ◽  
Vol 81 (1) ◽  
pp. 201-208 ◽  
Author(s):  
Tyler K. Ulland ◽  
Ann M. Janowski ◽  
Blake W. Buchan ◽  
Matthew Faron ◽  
Suzanne L. Cassel ◽  
...  
Keyword(s):  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Live Vaccine ◽  
Live Vaccine Strain ◽  
Wild Type ◽  
Content Type ◽  
Pseudouridine Synthase ◽  
Caspase 1

Francisella tularensisis a Gram-negative bacterium and the causative agent of the disease tularemia. Escape ofF. tularensisfrom the phagosome into the cytosol of the macrophage triggers the activation of the AIM2 inflammasome through a mechanism that is not well understood. Activation of the AIM2 inflammasome results in autocatalytic cleavage of caspase-1, resulting in the processing and secretion of interleukin-1β (IL-1β) and IL-18, which play a crucial role in innate immune responses toF. tularensis. We have identified the5-formyltetrahydrofolate cycloligasegene (FTL_0724) as being important forF. tularensislive vaccine strain (LVS) virulence. Infection of micein vivowith aF. tularensisLVSFTL_0724mutant resulted in diminished mortality compared to infection of mice with wild-type LVS. TheFTL_0724mutant also induced increased inflammasome-dependent IL-1β and IL-18 secretion and cytotoxicity in macrophagesin vitro. In contrast, infection of macrophages with aF. tularensisLVSrluD pseudouridine synthase(FTL_0699) mutant resulted in diminished IL-1β and IL-18 secretion from macrophagesin vitrocompared to infection of macrophages with wild-type LVS. In addition, theFTL_0699mutant was not attenuatedin vivo. These findings further illustrate thatF. tularensisLVS possesses numerous genes that influence its ability to activate the inflammasome, which is a key host strategy to control infection with this pathogenin vivo.

scholarly journals Genetic Screen inChlamydia muridarumReveals Role for an Interferon-Induced Host Cell Death Program in Antimicrobial Inclusion Rupture

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Amanda M. Giebel ◽  
Shuai Hu ◽  
Krithika Rajaram ◽  
Ryan Finethy ◽  
Evelyn Toh ◽  
...  
Keyword(s):  
Cell Death ◽  
Immune Responses ◽  
Host Cell ◽  
Host Defense ◽  
Genetic Screen ◽  
Content Type ◽  
Host Immune Responses ◽  
Interferon Stimulated Genes ◽  
Host Cell Death ◽  
Ifn Γ

ABSTRACTInterferon-regulated immune defenses protect mammals from pathogenically diverse obligate intracellular bacterial pathogens of the genusChlamydia. Interferon gamma (IFN-γ) is especially important in controlling the virulence ofChlamydiaspecies and thus impacts the modeling of human chlamydial infection and disease in mice. How IFN-γ contributes to cell-autonomous defenses againstChlamydiaspecies and how these pathogens evade IFN-γ-mediated immunity in their natural hosts are not well understood. We conducted a genetic screen which identified 31IFN-γ-sensitive (Igs) mutants of the mouse model pathogenChlamydia muridarum. Genetic suppressor analysis and lateral gene transfer were used to map the phenotype of one of these mutants, Igs4, to a missense mutation in a putative chlamydial inclusion membrane protein, TC0574. We observed the lytic destruction of Igs4-occupied inclusions and accompanying host cell death in response to IFN-γ priming or various proapoptotic stimuli. However, Igs4 was insensitive to IFN-γ-regulated cell-autonomous defenses previously implicated in anti-Chlamydia trachomatishost defense in mice. Igs4 inclusion integrity was restored by caspase inhibitors, indicating that the IFN-γ-mediated destruction of Igs4 inclusions is dependent upon the function of caspases or related prodeath cysteine proteases. We further demonstrated that the Igs4 mutant is immune restricted in an IFN-γ-dependent manner in a mouse infection model, thereby implicating IFN-γ-mediated inclusion destruction and host cell death as potentin vivohost defense mechanisms to which wild-typeC. muridarumis resistant. Overall, our results suggest thatC. muridarumevolved resistance mechanisms to counter IFN-γ-elicited programmed cell death and the associated destruction of intravacuolar pathogens.IMPORTANCEMultiple obligatory intracellular bacteria in the genusChlamydiaare important pathogens. In humans, strains ofC. trachomatiscause trachoma, chlamydia, and lymphogranuloma venereum. These diseases are all associated with extended courses of infection and reinfection that likely reflect the ability of chlamydiae to evade various aspects of host immune responses. Interferon-stimulated genes, driven in part by the cytokine interferon gamma, restrict the host range of variousChlamydiaspecies, but how these pathogens evade interferon-stimulated genes in their definitive host is poorly understood. VariousChlamydiaspecies can inhibit death of their host cells and may have evolved this strategy to evade prodeath signals elicited by host immune responses. We present evidence that chlamydia-induced programmed cell death resistance evolved to counter interferon- and immune-mediated killing ofChlamydia-infected cells.

scholarly journals Differing Effects of Interleukin-10 on Cutaneous and Pulmonary Francisella tularensis Live Vaccine Strain Infection

2013 ◽  
Vol 81 (6) ◽  
pp. 2022-2027 ◽  
Author(s):  
Dennis W. Metzger ◽  
Sharon L. Salmon ◽  
Girish Kirimanjeswara
Keyword(s):  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Pulmonary Infection ◽  
Interleukin 10 ◽  
Live Vaccine ◽  
Live Vaccine Strain ◽  
Content Type ◽  
Infectious Dose ◽  
Therapeutic Benefits

ABSTRACTWe investigated the role of interleukin-10 (IL-10) in cutaneous and pulmonary infection withFrancisella tularensis. We found that after intradermal challenge of mice with the live vaccine strain (LVS) ofF. tularensis, splenic IL-10 levels increased rapidly and reached a peak 5 days after infection. However, IL-10 expression after infection was detrimental, since IL-10−/−mice showed increased bacterial clearance and were resistant to an infectious dose (>106CFU/mouse) that was uniformly lethal for IL-10+/+mice. Furthermore, IL-10+/+mice treated with neutralizing anti-IL-10R monoclonal antibody were able to survive lethal cutaneous LVS challenge. The presence of IL-10 appeared to restrain the expression of IL-17, since high levels of splenic IL-17 were observed after intradermal LVS infection only in IL-10−/−mice. Furthermore, treatment with neutralizing anti-IL-17R antibody ablated the enhanced survival observed in IL-10−/−mice. However, neutralization of IL-10 activity in IL-17R−/−mice failed to provide protection. Thus, IL-10 suppresses a protective IL-17 response that is necessary for resistance to cutaneous LVS infection. Surprisingly, however, IL-10−/−mice were significantly more susceptible to pulmonary infection with LVS. Finally, although IL-10 is a critical and novel regulator of immunity toF. tularensisLVS infection, its effects were masked during infection with the highly virulent SchuS4 strain. Taken together, these findings suggest that differentially regulating expression of the IL-10 pathway in various tissues could ultimately have prophylactic and therapeutic benefits for protection against tularemia.

scholarly journals Increased Susceptibility of IgA-Deficient Mice to Pulmonary Francisella tularensis Live Vaccine Strain Infection

2013 ◽  
Vol 81 (9) ◽  
pp. 3434-3441 ◽  
Author(s):  
Yoichi Furuya ◽  
Girish S. Kirimanjeswara ◽  
Sean Roberts ◽  
Dennis W. Metzger
Keyword(s):  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Early Time ◽  
Iga Deficiency ◽  
Live Vaccine ◽  
Interleukin 12 ◽  
Live Vaccine Strain ◽  
Content Type ◽  
Ifn Γ ◽  
Increased Susceptibility

ABSTRACTFrancisella tularensis, the causative agent of tularemia, is most deadly in the pneumonic form; therefore, mucosal immunity is an important first line of defense against this pathogen. We have now evaluated the lethality of primaryF. tularensislive vaccine strain (LVS) pulmonary infection in mice that are defective in IgA (IgA−/−mice), the predominant mucosal Ig isotype. The results showed that IgA−/−mice were more susceptible than IgA+/+mice to intranasalF. tularensisLVS infection, despite developing higher levels of LVS-specific total, IgG, and IgM antibodies in the bronchoalveolar lavage specimens following infection. In addition, the absence of IgA resulted in a significant increase in bacterial loads and reduced survival. Interestingly, IgA−/−mice had lower pulmonary gamma interferon (IFN-γ) levels and decreased numbers of IFN-γ-secreting CD4+and CD8+T cells in the lung on day 9 postinfection compared to IgA+/+mice. Furthermore, IgA−/−mice displayed reduced interleukin 12 (IL-12) levels at early time points, and supplementing IgA−/−mice with IL-12 prior to LVS challenge induced IFN-γ production by NK cells and rescued them from mortality. Thus, IgA−/−mice are highly susceptible to primary pulmonary LVS infections not only because of IgA deficiency but also because of reduced IFN-γ responses.

scholarly journals Importance of PdpC, IglC, IglI, and IglG for Modulation of a Host Cell Death Pathway Induced by Francisella tularensis

2013 ◽  
Vol 81 (6) ◽  
pp. 2076-2084 ◽  
Author(s):  
Marie Lindgren ◽  
Kjell Eneslätt ◽  
Jeanette E. Bröms ◽  
Anders Sjöstedt
Keyword(s):  
Cell Death ◽  
Host Cell ◽  
Francisella Tularensis ◽  
Caspase 3 ◽  
Mitochondrial Damage ◽  
Content Type ◽  
Mitochondrial Superoxide ◽  
Cell Death Pathway ◽  
Host Cell Death ◽  
Nucleosome Formation

ABSTRACTModulation of host cell death pathways appears to be a prerequisite for the successful lifestyles of many intracellular pathogens. The facultative intracellular bacteriumFrancisella tularensisis highly pathogenic, and effective proliferation in the macrophage cytosol leading to host cell death is a requirement for its virulence. To better understand the prerequisites of this cell death, macrophages were infected with theF. tularensislive vaccine strain (LVS), and the effects were compared to those resulting from infections with deletion mutants lacking expression of either of thepdpC,iglC,iglG, origlIgenes, which encode components of theFrancisellapathogenicity island (FPI), a type VI secretion system. Within 12 h, a majority of the J774 cells infected with the LVS strain showed production of mitochondrial superoxide and, after 24 h, marked signs of mitochondrial damage, caspase-9 and caspase-3 activation, phosphatidylserine expression, nucleosome formation, and membrane leakage. In contrast, neither of these events occurred after infection with the ΔiglIor ΔiglCmutants, although the former strain replicated. The ΔiglGmutant replicated effectively but induced only marginal cytopathogenic effects after 24 h and intermediate effects after 48 h. In contrast, the ΔpdpCmutant showed no replication but induced marked mitochondrial superoxide production and mitochondrial damage, caspase-3 activation, nucleosome formation, and phosphatidylserine expression, although the effects were delayed compared to those obtained with LVS. The unique phenotypes of the mutants provide insights regarding the roles of individual FPI components for the modulation of the cytopathogenic effects resulting from theF. tularensisinfection.

scholarly journals Aim2 and Nlrp3 Are Dispensable For Vaccine-Induced Immunity Against Francisella tularensis Live Vaccine Strain

2021 ◽  
Author(s):  
Maha Alqahtani ◽  
Zhuo Ma ◽  
Kayla Fantone ◽  
Meenakshi Malik ◽  
Chandra Shekhar Bakshi
Keyword(s):  
Immune Responses ◽  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Nlrp3 Inflammasome ◽  
Live Vaccine ◽  
Innate Immune ◽  
Live Vaccine Strain ◽  
Innate Immune Responses ◽  
Lethal Challenge ◽  
Induced Immunity

Francisella tularensis (F. 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 the 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 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 in 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 in vaccine-induced immune responses in a mouse model of respiratory tularemia. We developed a model to vaccinate the Aim2 and Nlrp3-deficient mice (Aim2-/- and Nlrp3-/-) using the emrA1 mutant of 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 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 the 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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