scholarly journals Construction and Characterization of an Attenuated Purine Auxotroph in a Francisella tularensis Live Vaccine Strain

2006 ◽  
Vol 74 (8) ◽  
pp. 4452-4461 ◽  
Author(s):  
Roger Pechous ◽  
Jean Celli ◽  
Renee Penoske ◽  
Stanley F. Hayes ◽  
Dara W. Frank ◽  
...  
Keyword(s):  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Defined Medium ◽  
Live Vaccine ◽  
Live Vaccine Strain ◽  
Lethal Challenge ◽  
Significant Attenuation ◽  
Infected Cells

ABSTRACT Francisella tularensis is a facultative intracellular pathogen and is the etiological agent of tularemia. It is capable of escaping from the phagosome, replicating to high numbers in the cytosol, and inducing apoptosis in macrophages of a variety of hosts. F. tularensis has received significant attention recently due to its potential use as a bioweapon. Currently, there is no licensed vaccine against F. tularensis, although a partially protective live vaccine strain (LVS) that is attenuated in humans but remains fully virulent for mice was previously developed. An F. tularensis LVS mutant deleted in the purMCD purine biosynthetic locus was constructed and partially characterized by using an allelic exchange strategy. The F. tularensis LVS ΔpurMCD mutant was auxotrophic for purines when grown in defined medium and exhibited significant attenuation in virulence when assayed in murine macrophages in vitro or in BALB/c mice. Growth and virulence defects were complemented by the addition of the purine precursor hypoxanthine or by introduction of purMCDN in trans. The F. tularensis LVS ΔpurMCD mutant escaped from the phagosome but failed to replicate in the cytosol or induce apoptotic and cytopathic responses in infected cells. Importantly, mice vaccinated with a low dose of the F. tularensis LVSΔ purMCD mutant were fully protected against subsequent lethal challenge with the LVS parental strain. Collectively, these results suggest that F. tularensis mutants deleted in the purMCD biosynthetic locus exhibit characteristics that may warrant further investigation of their use as potential live vaccine candidates.

scholarly journals T-bet Regulates Immunity to Francisella tularensis Live Vaccine Strain Infection, Particularly in Lungs

2014 ◽  
Vol 82 (4) ◽  
pp. 1477-1490 ◽  
Author(s):  
Amanda A. Melillo ◽  
Oded Foreman ◽  
Catharine M. Bosio ◽  
Karen L. Elkins
Keyword(s):  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Live Vaccine ◽  
Interleukin 17 ◽  
Live Vaccine Strain ◽  
Respiratory Protection ◽  
Necrosis Factor Alpha ◽  
Secondary Challenge ◽  
Ifn Γ

ABSTRACTUpregulation of the transcription factor T-bet is correlated with the strength of protection against secondary challenge with the live vaccine strain (LVS) ofFrancisella tularensis. Thus, to determine if this mediator had direct consequences in immunity to LVS, we examined its role in infection. Despite substantialin vivogamma interferon (IFN-γ) levels, T-bet-knockout (KO) mice infected intradermally (i.d.) or intranasally (i.n.) with LVS succumbed to infection with doses 2 log units less than those required for their wild-type (WT) counterparts, and exhibited significantly increased bacterial burdens in the lung and spleen. Lungs of LVS-infected T-bet-KO mice contained fewer lymphocytes and more neutrophils and interleukin-17 than WT mice. LVS-vaccinated T-bet-KO mice survived lethal LVS intraperitoneal secondary challenge but not high doses of LVS i.n. challenge, independently of the route of vaccination. Immune T lymphocytes from the spleens of i.d. LVS-vaccinated WT or KO mice controlled intracellular bacterial replication in anin vitrococulture system, but cultures with T-bet-KO splenocyte supernatants contained less IFN-γ and increased amounts of tumor necrosis factor alpha. In contrast, immune T-bet-KO lung lymphocytes were greatly impaired in controlling intramacrophage growth of LVS; this functional defect is the likely mechanism underpinning the lack of respiratory protection. Taken together, T-bet is important in host resistance to primary LVS infection and i.n. secondary challenge. Thus, T-bet represents a true, useful correlate for immunity to LVS.

scholarly journals In vitro and in vivo characterization of chimeric duck Tembusu virus based on Japanese encephalitis live vaccine strain SA14-14-2

2016 ◽  
Vol 97 (7) ◽  
pp. 1551-1556 ◽  
Author(s):  
Hong-Jiang Wang ◽  
Long Liu ◽  
Xiao-Feng Li ◽  
Qing Ye ◽  
Yong-Qiang Deng ◽  
...  
Keyword(s):  
Vaccine Strain ◽  
Japanese Encephalitis ◽  
Live Vaccine ◽  
Live Vaccine Strain ◽  
Duck Tembusu Virus ◽  
Tembusu Virus ◽  
In Vivo Characterization

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 An In Vitro Model System Used To Study Adherence and Invasion of Francisella tularensis Live Vaccine Strain in Nonphagocytic Cells

2007 ◽  
Vol 75 (6) ◽  
pp. 3178-3182 ◽  
Author(s):  
Stephen R. Lindemann ◽  
Molly K. McLendon ◽  
Michael A. Apicella ◽  
Bradley D. Jones
Keyword(s):  
Francisella Tularensis ◽  
Vaccine Strain ◽  
In Vitro Model ◽  
Cytochalasin D ◽  
Live Vaccine ◽  
Live Vaccine Strain ◽  
Intracellular Growth ◽  
Phagocytic Cells ◽  
Vitro Model

ABSTRACT In observing Francisella tularensis interactions with nonphagocytic cell lines in vitro, we noted significant adherence, invasion, and intracellular growth of the bacteria within these cells. F. tularensis live vaccine strain invasion of nonprofessional phagocytic cells is inhibited by cytochalasin D and nocodazole, suggesting that both the actin and microtubule cytoskeletons are important for invasion.

scholarly journals A Defined O-Antigen Polysaccharide Mutant of Francisella tularensis Live Vaccine Strain Has Attenuated Virulence while Retaining Its Protective Capacity

2007 ◽  
Vol 75 (5) ◽  
pp. 2591-2602 ◽  
Author(s):  
Shite Sebastian ◽  
Simon T. Dillon ◽  
Jillian G. Lynch ◽  
LeeAnn T. Blalock ◽  
Emmy Balon ◽  
...  
Keyword(s):  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Lethal Dose ◽  
Live Vaccine ◽  
Effective Vaccine ◽  
Live Vaccine Strain ◽  
Virulence Determinants ◽  
Protective Capacity ◽  
O Antigen

ABSTRACT Francisella tularensis, the causative agent of tularemia, has been designated a CDC category A select agent because of its low infective dose (<10 CFU), its ready transmission by aerosol, and its ability to produce severe morbidity and high mortality. The identification and characterization of this organism's virulence determinants will facilitate the development of a safe and effective vaccine. We report that inactivation of the wbtA-encoded dehydratase of the O-antigen polysaccharide (O-PS) locus of the still-unlicensed live vaccine strain of F. tularensis (LVS) results in a mutant (the LVS wbtA mutant) with remarkably attenuated virulence. Western blot analysis and immune electron microscopy studies associate this loss of virulence with a complete lack of surface O-PS expression. A likely mechanism for attenuation is shown to be the transformation from serum resistance in the wild-type strain to serum sensitivity in the mutant. Despite this significant attenuation in virulence, the LVS wbtA mutant remains immunogenic and confers protective immunity on mice against challenge with an otherwise lethal dose of either F. tularensis LVS or a fully virulent clinical isolate of F. tularensis type B. Recognition and characterization of the pivotal role of O-PS in the virulence of this intracellular bacterial pathogen may have broad implications for the creation of a safe and efficacious vaccine.

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.

scholarly journals Inactivated Francisella tularensis Live Vaccine Strain Protects against Respiratory Tularemia by Intranasal Vaccination in an Immunoglobulin A-Dependent Fashion

2007 ◽  
Vol 75 (5) ◽  
pp. 2152-2162 ◽  
Author(s):  
Shawn D. Baron ◽  
Rajendra Singh ◽  
Dennis W. Metzger
Keyword(s):  
Francisella Tularensis ◽  
Vaccine Strain ◽  
Serum Antibody ◽  
Immunoglobulin A ◽  
Live Vaccine ◽  
Interleukin 12 ◽  
Live Vaccine Strain ◽  
Lethal Challenge ◽  
Mucosal Vaccination ◽  
Ifn Γ

ABSTRACT Francisella tularensis is a gram-negative intracellular bacterium that is considered to be a potential category A biological weapon due to its extreme virulence. Although vaccination with the attenuated live vaccine strain (LVS) of F. tularensis can protect against lethal challenge, use of inactivated or subunit forms as vaccine candidates for induction of protective antibody responses has not been fully evaluated. In the present study, we examined whether immune protection in the lung could be stimulated by intranasal administration of inactivated LVS together with interleukin-12 (IL-12) as an adjuvant. LVS was inactivated by heat, paraformaldehyde treatment, or exposure to UV, and inactivation of the preparations was confirmed by assessing bacterial growth and the survival of mice after direct inoculation. We found that mucosal vaccination with inactivated LVS provided 90 to 100% protection in mice after lethal intranasal challenge with 104 CFU of LVS, and this protection was dependent on inclusion of exogenous IL-12 during vaccine administration. Survival of vaccinated mice after live bacterial challenge was correlated with reduced bacterial burden, decreased pulmonary inflammation, increased serum antibody titers, and lower levels of gamma interferon (IFN-γ), tumor necrosis factor alpha, and IL-6 in the lungs, livers, and spleens. Whereas NK cells were primarily responsible for the production of IFN-γ in unvaccinated, challenged animals, vaccinated mice had increased levels of lung IFN-γ+ CD4+ T cells after challenge. Significantly, mice genetically deficient in immunoglobulin A (IgA) expression were unable to survive lethal challenge after vaccination. These results are the first results to demonstrate that IgA-mediated protection against lethal respiratory tularemia occurs after mucosal vaccination with inactivated F. tularensis LVS.

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