Tularensis Live Vaccine Strain Research Articles

Comparative analysis of absent in melanoma 2-inflammasome activation in Francisella tularensis and Francisella novicida.

Francisella tularensis is a highly virulent Gram-negative bacterium that causes the fatal zoonotic disease tularemia. The mechanisms and signaling pathways leading to the absent in melanoma 2 (Aim2) inflammasome activation have been elegantly elucidated using Francisella novicida as a model. Although not pathogenic for humans, F. novicida can cause tularemia in mice, and the inflammatory response it triggers is the polar opposite to that observed in mice infected with F. tularensis strains. This study aimed to understand the mechanisms of Aim2 inflammasome activation in F. tularensis-infected macrophages. The results reveal that macrophages infected with the F. tularensis live vaccine strain (LVS) induce lower levels of Aim2-dependent IL-1β than those infected with F. novicida. The suppression/weak activation of Aim2 in F. tularensis LVS-infected macrophages is due to the suppression of the cGAS-STING DNA-sensing pathway. Furthermore, the introduction of exogenous F. tularensis LVS DNA into the cytosol of the F. tularensis LVS-infected macrophages, alone or in conjunction with a priming signal, failed to restore IL-1β levels similar to those observed for F. novicida-infected macrophages. These results indicated that, in addition to the bacterial DNA, DNA from some other sources, specifically from the damaged mitochondria, might contribute to the robust Aim2-dependent IL-1β levels observed in F. novicida-infected macrophages. The results indicate that F. tularensis LVS induces mitophagy that may potentially prevent the leakage of mitochondrial DNA and the subsequent activation of the Aim2 inflammasome. Collectively, this study demonstrates that the mechanisms of Aim2 inflammasome activation established for F. novicida are not operative in F. tularensis.

IL-12p40 is essential but not sufficient for Francisella tularensis LVS clearance in chronically infected mice.

IL-12p40 plays an important role in F. tularensis Live Vaccine Strain (LVS) clearance that is independent of its functions as a part of the heterodimeric cytokines IL-12p70 or IL-23. In contrast to WT, p35, or p19 knockout (KO) mice, p40 KO mice infected with LVS develop a chronic infection that does not resolve. Here, we further evaluated the role of IL-12p40 in F. tularensis clearance. Despite reduced IFN-γ production, primed splenocytes from p40 KO and p35 KO mice appeared functionally similar to those from WT mice during in vitro co-culture assays of intramacrophage bacterial growth control. Gene expression analysis revealed a subset of genes that were upregulated in re-stimulated WT and p35 KO splenocytes, but not p40 KO splenocytes, and thus are candidates for involvement in F. tularensis clearance. To directly evaluate a potential mechanism for p40 in F. tularensis clearance, we reconstituted protein levels in LVS-infected p40 KO mice using either intermittent injections of p40 homodimer (p80) or treatment with a p40-producing lentivirus construct. Although both delivery strategies yielded readily detectable levels of p40 in sera and spleens, neither treatment had a measurable impact on LVS clearance by p40 KO mice. Taken together, these studies demonstrate that clearance of F. tularensis infection depends on p40, but p40 monomers and/or dimers alone are not sufficient.

ThioredoxinA1 Controls the Oxidative Stress Response of Francisella tularensis Live Vaccine Strain (LVS).

Francisella tularensis is an intracellular, Gram-negative bacterium known for causing a disease known as tularemia in the Northern Hemisphere. F. tularensis is classified as a category A select agent by the CDC based on its possible use as a bioterror agent. F. tularensis overcomes oxidative stress encountered during its growth in the environment or host macrophages by encoding antioxidant enzymes such as superoxide dismutases, catalase, and alkylhydroperoxy reductase. These antioxidant enzymes are regulated by the oxidative stress response regulator, OxyR. In addition to these antioxidant enzymes, F. tularensis also encodes two thioredoxins, TrxA1 (FTL_0611) and TrxA2 (FTL_1224); however, their role in the oxidative stress response of F. tularensis is not known. This study investigated the role of thioredoxins of F. tularensis in the oxidative stress response and intracellular survival. Our results demonstrate that TrxA1 but not TrxA2 plays a major role in the oxidative stress response of F. tularensis. Most importantly, this study elucidates a novel mechanism through which the TrxA1 of F. tularensis controls the oxidative stress response by regulating the expression of the master regulator, oxyR. Further, TrxA1 is required for the intramacrophage survival and growth of Francisella. Overall, this study describes a novel role of thioredoxin, TrxA1, in regulating the oxidative stress response of F. tularensis. IMPORTANCE The role of thioredoxins in the oxidative stress response of F. tularensis is not known. This study demonstrates that of the two thioredoxins, TrxA1 is vital to counter the oxidative stress in F. tularensis live vaccine strain (LVS). Furthermore, this study shows differences in the well-studied thioredoxins of Escherichia coli. First, the expression of TrxA1 of F. tularensis is independent of the oxidative stress response regulator, OxyR. Second and most importantly, TrxA1 regulates the expression of oxyR and, therefore, the OxyR-dependent oxidative stress response of F. tularensis. Overall, this study reports a novel regulatory role of TrxA1 of F. tularensis in the oxidative stress response.

Itaconate indirectly influences expansion of effector T cells following vaccination with Francisella tularensis live vaccine strain

The metabolite itaconate plays a critical role in modulating inflammatory responses among macrophages infected with intracellular pathogens. However, the ability of itaconate to influence developing T cells responses is poorly understood. To determine if itaconate contributes to the quality of T cell mediated immunity against intracellular infection, we used Francisella tularensis as a model of vaccine induced immunity. Following vaccination with F. tularensis live vaccine strain, itaconate deficient mice (ACOD KO) had a prolonged primary infection but were more resistant to secondary infection with virulent F. tularensis relative to wild type controls. Improved resistance to secondary challenge was associated with both increased numbers and effector function of CD4+ and CD8+ T cells in ACOD KO mice. However, additional data suggest that improved T cell responses was not T cell intrinsic. These data underscore the consequences of metabolic perturbations within antigen presenting cells on the development of vaccine-elicited immune responses.

Macrophages Demonstrate Guanylate-Binding Protein-Dependent and Bacterial Strain-Dependent Responses to Francisella tularensis.

Francisella tularensis is a facultative intracellular bacterium and the etiological agent of tularemia, a zoonotic disease. Infection of monocytic cells by F. tularensis can be controlled after activation with IFN-γ; however, the molecular mechanisms whereby the control is executed are incompletely understood. Recently, a key role has been attributed to the Guanylate-binding proteins (GBPs), interferon-inducible proteins involved in the cell-specific immunity against various intracellular pathogens. Here, we assessed the responses of bone marrow-derived murine macrophages (BMDM) and GBP-deficient BMDM to F. tularensis strains of variable virulence; the highly virulent SCHU S4 strain, the human live vaccine strain (LVS), or the widely used surrogate for F. tularensis, the low virulent F. novicida. Each of the strains multiplied rapidly in BMDM, but after addition of IFN-γ, significant GBP-dependent control of infection was observed for the LVS and F. novicida strains, whereas there was no control of the SCHU S4 infection. However, no differences in GBP transcription or translation were observed in the infected cell cultures. During co-infection with F. novicida and SCHU S4, significant control of both strains was observed. Patterns of 18 cytokines were very distinct between infected cell cultures and high levels were observed for almost all cytokines in F. novicida-infected cultures and very low levels in SCHU S4-infected cultures, whereas levels in co-infected cultures for a majority of cytokines showed intermediate levels, or levels similar to those of F. novicida-infected cultures. We conclude that the control of BMDM infection with F. tularensis LVS or F. novicida is GBP-dependent, whereas SCHU S4 was only controlled during co-infection. Since expression of GBP was similar regardless of infecting agent, the findings imply that SCHU S4 has an inherent ability to evade the GBP-dependent anti-bacterial mechanisms.

Macrophage Selenoproteins Restrict Intracellular Replication of Francisella tularensis and Are Essential for Host Immunity.

The essential micronutrient Selenium (Se) is co-translationally incorporated as selenocysteine into proteins. Selenoproteins contain one or more selenocysteines and are vital for optimum immunity. Interestingly, many pathogenic bacteria utilize Se for various biological processes suggesting that Se may play a role in bacterial pathogenesis. A previous study had speculated that Francisella tularensis, a facultative intracellular bacterium and the causative agent of tularemia, sequesters Se by upregulating Se-metabolism genes in type II alveolar epithelial cells. Therefore, we investigated the contribution of host vs. pathogen-associated selenoproteins in bacterial disease using F. tularensis as a model organism. We found that F. tularensis was devoid of any Se utilization traits, neither incorporated elemental Se, nor exhibited Se-dependent growth. However, 100% of Se-deficient mice (0.01 ppm Se), which express low levels of selenoproteins, succumbed to F. tularensis-live vaccine strain pulmonary challenge, whereas 50% of mice on Se-supplemented (0.4 ppm Se) and 25% of mice on Se-adequate (0.1 ppm Se) diet succumbed to infection. Median survival time for Se-deficient mice was 8 days post-infection while Se-supplemented and -adequate mice was 11.5 and >14 days post-infection, respectively. Se-deficient macrophages permitted significantly higher intracellular bacterial replication than Se-supplemented macrophages ex vivo, corroborating in vivo observations. Since Francisella replicates in alveolar macrophages during the acute phase of pneumonic infection, we hypothesized that macrophage-specific host selenoproteins may restrict replication and systemic spread of bacteria. F. tularensis infection led to an increased expression of several macrophage selenoproteins, suggesting their key role in limiting bacterial replication. Upon challenge with F. tularensis, mice lacking selenoproteins in macrophages (TrspM) displayed lower survival and increased bacterial burden in the lung and systemic tissues in comparison to WT littermate controls. Furthermore, macrophages from TrspM mice were unable to restrict bacterial replication ex vivo in comparison to macrophages from littermate controls. We herein describe a novel function of host macrophage-specific selenoproteins in restriction of intracellular bacterial replication. These data suggest that host selenoproteins may be considered as novel targets for modulating immune response to control a bacterial infection.

Abstract MP56: Transcriptomic Analysis Of Francisella Tularensis Infected Lungs From Human Angiotensin-II Receptor Type-1 Over-expressing Hypertensive Mice

Human angiotensin-II receptor type-I (hAT1R) over-expression may cause adverse pathological outcomes due to renin-angiotensin system overactivity. We have shown that transgenic (TG) mice containing Hap-I (hypertensive genotype) of hAT1R gene are more prone to develop metabolic syndrome (MetS) disorders as compared to the TG mice with Hap-II (normotensive genotype). Aging together with an increased risk of hypertension, can affect multiple organ systems, including increased susceptibility to various pathogenic infections. The current study, therefore, was designed to examine the potential role of aging and hypertension on lung pathology and altered transcriptome, in our TG mice, in response to Francisella tularensis live vaccine strain (LVS) intranasal infection. Our results showed that in comparison to Hap-II, aged Hap-I TG mice had a significantly higher mortality post-infection; elevated lung pathology; and altered gene expression profile. Consistent with worsened phenotype in aged Hap-I mice post LVS infection, RNA-seq data from their lungs revealed that >1400 genes (p <0.005) were significantly altered. Bioinformatics analysis identified major alterations in canonical pathways related to immune responses including interferon signaling, antigen presentation, agranulocyte adhesion and dendritic cell maturation. These alterations in turn resulted in disorders including, lung infection, inflammation, and immunological diseases. Importantly, IFNG, STAT1, STAT3 and TNF were among the top upstream regulators significantly affected by LVS infection. Overall, these results provide a deeper insight in molecular signaling associated with hypertension associated lung infections in aged subjects.

Correction: Immunologic Consequences of Francisella tularensis Live Vaccine Strain Infection: Role of the Innate Immune Response in Infection and Immunity.

Cole, L. E., K. L. Elkins, S. M. Michalek, N. Qureshi, L. J. Eaton, P. Rallabhandi, N. Cuesta, and S. N. Vogel. 2006. Immunologic consequences of Francisella tularensis live vaccine strain infection: role of the innate immune response in infection and immunity. J. Immunol. 176: [6888–6899][1].

Francisella tularensis induces Th1 like MAIT cells conferring protection against systemic and local infection

Mucosal-associated Invariant T (MAIT) cells are recognized for their antibacterial functions. The protective capacity of MAIT cells has been demonstrated in murine models of local infection, including in the lungs. Here we show that during systemic infection of mice with Francisella tularensis live vaccine strain results in evident MAIT cell expansion in the liver, lungs, kidney and spleen and peripheral blood. The responding MAIT cells manifest a polarised Th1-like MAIT-1 phenotype, including transcription factor and cytokine profile, and confer a critical role in controlling bacterial load. Post resolution of the primary infection, the expanded MAIT cells form stable memory-like MAIT-1 cell populations, suggesting a basis for vaccination. Indeed, a systemic vaccination with synthetic antigen 5-(2-oxopropylideneamino)-6-d-ribitylaminouracil in combination with CpG adjuvant similarly boosts MAIT cells, and results in enhanced protection against both systemic and local infections with different bacteria. Our study highlights the potential utility of targeting MAIT cells to combat a range of bacterial pathogens.

Chronically Hypertensive Transgenic Mice Expressing Human AT1R Haplotype‐I Exhibit Increased Susceptibility To Francisella Tularensis

Angiotensin receptor type 1 (AT1R), a G-protein coupled receptor mediates the effect of angiotensin-II and contributes to the pathophysiological consequences of metabolic disorders leading to vascular remodeling, hypertension, and end-organ damage. Genetic variations that increase human AT1R (hAT1R) expression can cause above pathological outcomes due to renin-angiotensin system overactivity. Previously we have shown that transgenic (TG) mice containing haplotype-I (Hap-I, hypertensive genotype) of human AT1R gene are more prone to develop the metabolic syndrome (MetS) related disorders as compared to the TG mice containing haplotype-II (Hap-II, normotensive genotype). We have also shown that as compared to Hap-II, the aged Hap-I TG mice overexpress the hAT1R gene resulting in an increase in blood pressure, inflammatory molecules, and renal dysfunction. Aging together with an increased risk of hypertension, can affect multiple organ systems in a complex manner, including susceptibility to various infections. The current study, therefore, was designed to examine the potential effect of aging and associated MetS disorders in our hAT1R containing TG mice model, in response to the infection by Francisella tularensis live vaccine strain (LVS) inhalation. Our results show that Hap-I TG mice have a significantly high mortality rate two weeks post-infection as compared to the Hap-II animals. Histochemical analysis of lung tissues from adult and aged animals show a comparatively elevated pathology in mice containing Hap-I of hAT1R. The lung tissue and plasma from Hap-I TG mice also show a relatively higher bacterial load five days post-infection. Preliminary RT-PCR experiments show increased inflammatory markers like IL-6, TGF-β, TNF-α, CRP and redox markers like NOX1, NOX4 in lung tissues of Hap-I TG mice. These studies suggest that haplotype dependent over-expression of hAT1R gene, leads to an enhanced mortality and lung pathology to F. tularensis LVS infection, which gets aggravated in aged animals. Clinically, our results may help in exploring the role of AT1R induced hypertension in pulmonary infections.

Aim2 and Nlrp3 Are Dispensable for Vaccine-Induced Immunity against Francisella tularensis Live Vaccine Strain.

Francisella tularensis is a facultative, intracellular, Gram-negative bacterium that causes a fatal disease known as tularemia. Due to its extremely high virulence, ease of spread by aerosolization, and potential to be used as a bioterror agent, F. tularensis is classified by the CDC as a tier 1 category A select agent. Previous studies have demonstrated the roles of the inflammasome sensors absent in melanoma 2 (AIM2) and NLRP3 in the generation of innate immune responses to F. tularensis infection. However, contributions of both the AIM2 and NLRP3 to the development of vaccine-induced adaptive immune responses against F. tularensis are not known. This study determined the contributions of Aim2 and Nlrp3 inflammasome sensors to vaccine-induced immune responses in a mouse model of respiratory tularemia. We developed a model to vaccinate Aim2- and Nlrp3-deficient (Aim2-/- and Nlrp3-/-) mice using the emrA1 mutant of the F. tularensis live vaccine strain (LVS). The results demonstrate that the innate immune responses in Aim2-/- and Nlrp3-/- mice vaccinated with the emrA1 mutant differ from those of their wild-type counterparts. However, despite these differences in the innate immune responses, both Aim2-/- and Nlrp3-/- mice are fully protected against an intranasal lethal challenge dose of F. tularensis LVS. Moreover, the lack of both Aim2 and Nlrp3 inflammasome sensors does not affect the production of vaccination-induced antibody and cell-mediated responses. Overall, this study reports a novel finding that both Aim2 and Nlrp3 are dispensable for vaccination-induced immunity against respiratory tularemia caused by F. tularensis.

Deficiency in CCR2 increases susceptibility of mice to infection with an intracellular pathogen, Francisella tularensis LVS, but does not impair development of protective immunity.

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.

Guanylate-Binding Proteins Are Critical for Effective Control of Francisella tularensis Strains in a Mouse Co-Culture System of Adaptive Immunity.

Francisella tularensis is a Select Agent that causes the severe disease tularemia in humans and many animal species. The bacterium demonstrates rapid intracellular replication, however, macrophages can control its replication if primed and activation with IFN-γ is known to be essential, although alone not sufficient, to mediate such control. To further investigate the mechanisms that control intracellular F. tularensis replication, an in vitro co-culture system was utilized containing splenocytes obtained from naïve or immunized C57BL/6 mice as effectors and infected bone marrow-derived wild-type or chromosome-3-deficient guanylate-binding protein (GBP)-deficient macrophages. Cells were infected either with the F. tularensis live vaccine strain (LVS), the highly virulent SCHU S4 strain, or the surrogate for F. tularensis, F. novicida. Regardless of strain, significant control of the bacterial replication was observed in co-cultures with wild-type macrophages and immune splenocytes, but not in cultures with immune splenocytes and GBP chr3-deficient macrophages. Supernatants demonstrated very distinct, infectious agent-dependent patterns of 23 cytokines, whereas the cytokine patterns were only marginally affected by the presence or absence of GBPs. Levels of a majority of cytokines were inversely correlated to the degree of control of the SCHU S4 and LVS infections, but this was not the case for the F. novicida infection. Collectively, the co-culture assay based on immune mouse-derived splenocytes identified a dominant role of GBPs for the control of intracellular replication of various F. tularensis strains, regardless of their virulence, whereas the cytokine patterns markedly were dependent on the infectious agents, but less so on GBPs.

Complete Genome Sequence of Francisella tularensis Live Vaccine Strain NR-28537 (BEI Master Cell Bank).

The genome of Francisella tularensis live vaccine strain NR-28537 was sequenced by a hybrid approach utilizing an Oxford Nanopore Technologies R9 flow cell and an Illumina MiSeq platform. De novo assembly of the resulting long and short reads produced a single-contig whole-genome sequence.

Atg5-Deficient Mice Infected with Francisella tularensis LVS Demonstrate Increased Survival and Less Severe Pathology in Internal Organs

Francisella tularensis is a highly virulent intracellular pathogen that proliferates within various cell types and can infect a multitude of animal species. Francisella escapes the phagosome rapidly after infection and reaches the host cell cytosol where bacteria undergo extensive replication. Once cytosolic, Francisella becomes a target of an autophagy-mediated process. The mechanisms by which autophagy plays a role in replication of this cytosolic pathogen have not been fully elucidated. In vitro, F. tularensis avoids degradation via autophagy and the autophagy process provides nutrients that support its intracellular replication, but the role of autophagy in vivo is unknown. Here, we investigated the role of autophagy in the pathogenesis of tularemia by using transgenic mice deficient in Atg5 in the myeloid lineage. The infection of Atg5-deficient mice with Francisella tularensis subsp. holarctica live vaccine strain (LVS) resulted in increased survival, significantly reduced bacterial burden in the mouse organs, and less severe histopathological changes in the spleen, liver and lung tissues. The data highlight the contribution of Atg5 in the pathogenesis of tularemia in vivo.

CXCL16 Stimulates Antigen-Induced MAIT Cell Accumulation but Trafficking During Lung Infection Is CXCR6-Independent.

Mucosa-associated invariant T (MAIT) cells are a unique T cell subset that contributes to protective immunity against microbial pathogens, but little is known about the role of chemokines in recruiting MAIT cells to the site of infection. Pulmonary infection with Francisella tularensis live vaccine strain (LVS) stimulates the accrual of large numbers of MAIT cells in the lungs of mice. Using this infection model, we find that MAIT cells are predominantly CXCR6+ but do not require CXCR6 for accumulation in the lungs. However, CXCR6 does contribute to long-term retention of MAIT cells in the airway lumen after clearance of the infection. We also find that MAIT cells are not recruited from secondary lymphoid organs and largely proliferate in situ in the lungs after infection. Nevertheless, the only known ligand for CXCR6, CXCL16, is sufficient to drive MAIT cell accumulation in the lungs in the absence of infection when administered in combination with the MAIT cell antigen 5-OP-RU. Overall, this new data advances the understanding of mechanisms that facilitate MAIT cell accumulation and retention in the lungs.

Immune lymphocytes halt replication of Francisella tularensis LVS within the cytoplasm of infected macrophages

Francisella tularensis is a highly infectious intracellular bacterium that causes tularemia by invading and replicating in mammalian myeloid cells. Francisella primarily invades host macrophages, where it escapes phagosomes within a few hours and replicates in the cytoplasm. Less is known about how Francisella traffics within macrophages or exits into the extracellular environment for further infection. Immune T lymphocytes control the replication of Francisella within macrophages in vitro by a variety of mechanisms, but nothing is known about intracellular bacterial trafficking in the face of such immune pressure. Here we used a murine model of infection with a Francisella attenuated live vaccine strain (LVS), which is under study as a human vaccine, to evaluate the hypothesis that immune T cells control intramacrophage bacterial growth by re-directing bacteria into toxic intracellular compartments of infected macrophages. We visualized the interactions of lymphocytes and LVS-infected macrophages using confocal microscopy and characterized LVS intramacrophage trafficking when co-cultured with immune lymphocytes. We focused on the late stages of infection after bacteria escape from phagosomes, through bacterial replication and the death of macrophages. We found that the majority of LVS remained cytosolic in the absence of immune pressure, eventually resulting in macrophage death. In contrast, co-culture of LVS-infected macrophages with LVS-immune lymphocytes halted LVS replication and inhibited the spread of LVS infection between macrophages, but bacteria did not return to vacuoles such as lysosomes or autophagosomes and macrophages did not die. Therefore, immune lymphocytes directly limit intracellular bacterial replication within the cytoplasm of infected macrophages.

Protective role of TH17 cells in an FcγR targeting immunization strategy against the respiratory bacterial pathogen, Francisella tularensis

Abstract Francisella tularensis is a category A intracellular bacterial pathogen with no FDA approved vaccine. Understanding the immunological mechanisms involved in host defense can improve vaccine efficacy. Previously we have shown using an F. tularensis murine infection model that targets the inactivated bacterium (iFt) to Fcγ receptors on antigen presenting cells (APCs) using anti-LPS monoclonal antibodies (mAb-iFt) provides full protection against lethal pulmonary challenge with F. tularensis live vaccine strain (LVS). The protection provided by this mucosal vaccine strategy involves both innate and adaptive immune components, with a strong inflammatory response being critical for protection. This study focuses on elucidating the role of Th 17 cells, a T helper cell subpopulation involved in pathology and host defenses against bacterial pathogens. C57BL/6 mice were immunized with iFt and mAb-iFt on day 0 and 21 and then challenged i.n. with a lethal dose of LVS on day 35. Flow cytometry data revealed a significant population of Th17 cells (characterized as CD3+/CD4+/IL- 17a+/RORγ-T+ cells) in the lungs and spleen post-infection in the mAb-iFt immunized group when compared to PBS and iFt alone. Additionally, cytokine levels of IL-6 and TGF-β1 (two known synergistic Th17 polarizing cytokines) were elevated in the lungs and spleens of mAb-iFt immunized mice on days 2 and 5 post-infection when compared to iFt alone. Lastly, cytokine levels of IL-17a, an effector cytokine secreted predominantly by active Th17 cells, was shown to be significantly increased in mAb-iFt immunized mice when compared to iFt alone. Collectively, our data suggests that Th17 cells possess a protective role in the immune response to pulmonary F. tularensis infection.

Utilizing the Francisella tularensis Live Vaccine Strain as a novel vaccine platform against the Ebola Virus

GAGE PYLES and JOSEPH HORZEMPA, Department of Natural Sciences and Mathematics, West Liberty University, West Liberty, WV. Utilizing the Francisella tularensis Live Vaccine Strain as a novel vaccine platform against the Ebola Virus.Francisella tularensis and the Ebola Virus (EBOV) are classified by the Centers for Disease Control and Prevention as Category A select agents for their potential use in bioterrorism. The F. tularensis Live Vaccine Strain (LVS) has been shown to provide over 30 years of protective immunity against F. tularensis, while for EBOV there remains no clinically approved protective vaccine. Due to the immunogenic properties of LVS, we propose that LVS may be a promising vaccine platform, of which recombinant strains may be able to confer protection against both F. tularensis and other pathogenic microbes such as EBOV. To test this, a fusion protein consisting of the glycoprotein of EBOV (GP) and LpnA (an immunodominant outer-membrane lipoprotein of F. tularensis) has been created. This newly generated chimeric protein (LpnA-GP) will ultimately be expressed in LVS, and the efficacy of this strain as a vaccine against both pathogens will be determined.

Lipoprotein sorting as a potential target of resazomycins, a novel family of antibiotics

The prevalence of antibiotic-resistant bacterial infection has increased, promoting a global health concern. The significance of this resistance pertains to the limitation it places on effective and available microbial agents, resulting in a predicament worsened by the small number of antimicrobial agents introduced over the last couple of years. Therefore, new antibiotics must be developed with unique targets that are not susceptible to rapid antimicrobial resistance. With this stated, it is known that the Lol system is responsible for transporting lipoproteins to the outer membrane in Gram-negative bacteria which play essential roles in a wide variety of bacterial physiological processes. We have identified a novel family of compounds, resazomycins, which exhibit antimicrobial activity against select Gram-negative bacteria including the human pathogens Francisella tularensis and Neisseria gonorrhoeae. A common feature of resazomycin-sensitive bacteria is possession of a unique lipoprotein sorting system, LolDF. This complex differs from the LolCDE sorting complex found in most Gram-negative bacteria like Escherichia coli that are resistant to resazomycins. We sought to determine whether LolDF is the target of resazomycins by cloning the genes that encode the E. coli LolCDE transporter into an F. tularensis plasmid and then electroporated this plasmid into an attenuated F. tularensis live vaccine strain (LVS) to see if these would render the bacterium resistant to resazomycins. Thus far, LolCDE-expressing LVS exhibits no difference in susceptibility to resazomycins compared to wild-type LVS. Therefore, we are investigating the role of other F. tularensis genes insusceptibility to resazomycins.