scholarly journals MyD88 Mediates Instructive Signaling in Dendritic Cells and Protective Inflammatory Response during Rickettsial Infection

2016 ◽  
Vol 84 (4) ◽  
pp. 883-893 ◽  
Author(s):  
Jeremy Bechelli ◽  
Claire Smalley ◽  
Xuemei Zhao ◽  
Barbara Judy ◽  
Patricia Valdes ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Inflammatory Response ◽  
Spotted Fever ◽  
Host Susceptibility ◽  
Rickettsia Conorii ◽  
Spotted Fever Group ◽  
Rickettsial Infection ◽  
Content Type ◽  
Ifn Γ

Spotted fever group rickettsiae cause potentially life-threatening infections throughout the world. Several members of the Toll-like receptor (TLR) family are involved in host response to rickettsiae, and yet the mechanisms by which these TLRs mediate host immunity remain incompletely understood. In the present study, we found that host susceptibility of MyD88−/−mice to infection withRickettsia conoriiorRickettsia australiswas significantly greater than in wild-type (WT) mice, in association with severely impaired bacterial clearancein vivo.R. australis-infected MyD88−/−mice showed significantly lower expression levels of gamma interferon (IFN-γ), interleukin-6 (IL-6), and IL-1β, accompanied by significantly fewer inflammatory infiltrates of macrophages and neutrophils in infected tissues, than WT mice. The serum levels of IFN-γ, IL-12, IL-6, and granulocyte colony-stimulating factor were significantly reduced, while monocyte chemoattractant protein 1, macrophage inflammatory protein 1α, and RANTES were significantly increased in infected MyD88−/−mice compared to WT mice. Strikingly,R. australisinfection was incapable of promoting increased expression of MHC-IIhighand production of IL-12p40 in MyD88−/−bone marrow-derived dendritic cells (BMDCs) compared to WT BMDCs, although costimulatory molecules were upregulated in both types of BMDCs. Furthermore, the secretion levels of IL-1β byRickettsia-infected BMDCs and in the sera of infected mice were significantly reduced in MyD88−/−mice compared to WT controls, suggesting thatin vitroandin vivoproduction of IL-1β is MyD88 dependent. Taken together, our results suggest that MyD88 signaling mediates instructive signals in DCs and secretion of IL-1β and type 1 immune cytokines, which may account for the protective inflammatory response during rickettsial infection.

scholarly journals Nonselective Persistence of a Rickettsia conorii Extrachromosomal Plasmid during Mammalian Infection

2016 ◽  
Vol 84 (3) ◽  
pp. 790-797 ◽  
Author(s):  
Sean P. Riley ◽  
Abigail I. Fish ◽  
Daniel A. Garza ◽  
Kaikhushroo H. Banajee ◽  
Emma K. Harris ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Genetic Manipulation ◽  
Fluorescent Proteins ◽  
Spotted Fever ◽  
Rickettsia Conorii ◽  
Mediterranean Spotted Fever ◽  
Extrachromosomal Dna ◽  
Content Type

Scientific analysis of the genusRickettsiais undergoing a rapid period of change with the emergence of viable genetic tools. The development of these tools for the mutagenesis of pathogenic bacteria will permit forward genetic analysis ofRickettsiapathogenesis. Despite these advances, uncertainty still remains regarding the use of plasmids to study these bacteria inin vivomammalian models of infection, namely, the potential for virulence changes associated with the presence of extrachromosomal DNA and nonselective persistence of plasmids in mammalian models of infection. Here, we describe the transformation ofRickettsia conoriiMalish 7 with the plasmid pRam18dRGA[AmTrCh]. TransformedR. conoriistably maintains this plasmid in infected cell cultures, expresses the encoded fluorescent proteins, and exhibits growth kinetics in cell culture similar to those of nontransformedR. conorii. Using a well-established murine model of fatal Mediterranean spotted fever, we demonstrate thatR. conorii(pRam18dRGA[AmTrCh]) elicits the same fatal outcomes in animals as its untransformed counterpart and, importantly, maintains the plasmid throughout infection in the absence of selective antibiotic pressure. Interestingly, plasmid-transformedR. conoriiwas readily observed both in endothelial cells and within circulating leukocytes. Together, our data demonstrate that the presence of an extrachromosomal DNA element in a pathogenic rickettsial species does not affect eitherin vitroproliferation orin vivoinfectivity in models of disease and that plasmids such as pRam18dRGA[AmTrCh] are valuable tools for the further genetic manipulation of pathogenic rickettsiae.

scholarly journals Differential Interaction of Dendritic Cells with Rickettsia conorii: Impact on Host Susceptibility to Murine Spotted Fever Rickettsiosis

2007 ◽  
Vol 75 (6) ◽  
pp. 3112-3123 ◽  
Author(s):  
Rong Fang ◽  
Nahed Ismail ◽  
Lynn Soong ◽  
Vsevolod L. Popov ◽  
Ted Whitworth ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Spotted Fever ◽  
Interleukin 12 ◽  
Mouse Strains ◽  
Rickettsia Conorii ◽  
Spotted Fever Group ◽  
C3h Mice

ABSTRACT Spotted fever group rickettsioses are emerging and reemerging infectious diseases, some of which are life-threatening. In order to understand how dendritic cells (DCs) contribute to the host resistance or susceptibility to rickettsial diseases, we first characterized the in vitro interaction of rickettsiae with bone marrow-derived DCs (BMDCs) from resistant C57BL/6 (B6) and susceptible C3H/HeN (C3H) mice. In contrast to the exclusively cytosolic localization within endothelial cells, rickettsiae efficiently entered and localized in both phagosomes and cytosol of BMDCs from both mouse strains. Rickettsia conorii-infected BMDCs from resistant mice harbored higher bacterial loads compared to C3H mice. R. conorii infection induced maturation of BMDCs from both mouse strains as judged by upregulated expression of classical major histocompatibility complex (MHC) and costimulatory molecules. Compared to C3H counterparts, B6 BMDCs exhibited higher expression levels of MHC class II and higher interleukin-12 (IL-12) p40 production upon rickettsial infection and were more potent in priming naïve CD4+ T cells to produce gamma interferon. In vitro DC infection and T-cell priming studies suggested a delayed CD4+ T-cell activation and suppressed Th1/Th2 cell development in C3H mice. The suppressive CD4+ T-cell responses seen in C3H mice were associated with a high frequency of Foxp3+ T regulatory cells promoted by syngeneic R. conorii-infected BMDCs in the presence of IL-2. These data suggest that rickettsiae can target DCs to stimulate a protective type 1 response in resistant hosts but suppressive adaptive immunity in susceptible hosts.

scholarly journals The Rickettsial OmpB β-Peptide of Rickettsia conorii Is Sufficient To Facilitate Factor H-Mediated Serum Resistance

2012 ◽  
Vol 80 (8) ◽  
pp. 2735-2743 ◽  
Author(s):  
Sean P. Riley ◽  
Jennifer L. Patterson ◽  
Juan J. Martinez
Keyword(s):  
Human Serum ◽  
Spotted Fever ◽  
Factor H ◽  
Rickettsia Conorii ◽  
Serum Resistance ◽  
Mediterranean Spotted Fever ◽  
Spotted Fever Group ◽  
Serum Complement ◽  
Additional Function ◽  
Content Type

ABSTRACTPathogenic species of the spotted fever groupRickettsiaare subjected to repeated exposures to the host complement system through cyclic infections of mammalian and tick hosts. The serum complement machinery is a formidable obstacle for bacteria to overcome if they endeavor to endure this endozoonotic cycle. We have previously demonstrated that that the etiologic agent of Mediterranean spotted fever,Rickettsia conorii, is susceptible to complement-mediated killing only in the presence of specific monoclonal antibodies. We have also shown that in the absence of particular neutralizing antibody,R. conoriiis resistant to the effects of serum complement. We therefore hypothesized that the interactions between fluid-phase complement regulators and conserved rickettsial outer membrane-associated proteins are critical to mediate serum resistance. We demonstrate here thatR. conoriispecifically interacts with the soluble host complement inhibitor, factor H. Depletion of factor H from normal human serum rendersR. conoriimore susceptible to C3 and membrane attack complex deposition and to complement-mediated killing. We identified the autotransporter protein rickettsial OmpB (rOmpB) as a factor H ligand and further demonstrate that the rOmpB β-peptide is sufficient to mediate resistance to the bactericidal properties of human serum. Taken together, these data reveal an additional function for the highly conserved rickettsial surface cell antigen, rOmpB, and suggest that the ability to evade complement-mediated clearance from the hematogenous circulation is a novel virulence attribute for this class of pathogens.

scholarly journals Activation of ASC Inflammasome Driven by Toll-Like Receptor 4 Contributes to Host Immunity against Rickettsial Infection

2020 ◽  
Vol 88 (4) ◽  
Author(s):  
Claire Rumfield ◽  
Ilirjana Hyseni ◽  
Jere W. McBride ◽  
David H. Walker ◽  
Rong Fang
Keyword(s):  
Host Susceptibility ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Content Type ◽  
Ifn Γ ◽  
Human Infections ◽  
Deficient Mice ◽  
Dependent Mechanism

ABSTRACT Rickettsiae are cytosolically replicating, obligately intracellular bacteria causing human infections worldwide with potentially fatal outcomes. We previously showed that Rickettsia australis activates ASC inflammasome in macrophages. In the present study, host susceptibility of ASC inflammasome-deficient mice to R. australis was significantly greater than that of C57BL/6 (B6) controls and was accompanied by increased rickettsial loads in various organs. Impaired host control of R. australis in vivo in ASC−/− mice was associated with dramatically reduced levels of interleukin 1β (IL-1β), IL-18, and gamma interferon (IFN-γ) in sera. The intracellular concentrations of R. australis in bone marrow-derived macrophages (BMMs) of TLR4−/− and ASC−/− mice were significantly greater than those in BMMs of B6 controls, highlighting the important role of inflammasome and these molecules in controlling rickettsiae in macrophages. Compared to B6 BMMs, TLR4−/− BMMs failed to secrete a significant level of IL-1β and had reduced expression levels of pro-IL-1β in response to infection with R. australis, suggesting that rickettsiae activate ASC inflammasome via a Toll-like receptor 4 (TLR4)-dependent mechanism. Further mechanistic studies suggest that the lipopolysaccharide (LPS) purified from R. australis together with ATP stimulation led to cleavage of pro-caspase-1 and pro-IL-1β, resulting in TLR4-dependent secretion of IL-1β. Taken together, these observations indicate that activation of ASC inflammasome, most likely driven by interaction of TLR4 with rickettsial LPS, contributes to host protective immunity against R. australis. These findings provide key insights into defining the interactions of rickettsiae with the host innate immune system.

scholarly journals Significant Growth by Rickettsia Species within Human Macrophage-Like Cells Is a Phenotype Correlated with the Ability to Cause Disease in Mammals

Pathogens ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 228
Author(s):  
M. Nathan Kristof ◽  
Paige E. Allen ◽  
Lane D. Yutzy ◽  
Brandon Thibodaux ◽  
Christopher D. Paddock ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Spotted Fever ◽  
Growth Characteristic ◽  
Human Macrophage ◽  
Rickettsia Conorii ◽  
Spotted Fever Group ◽  
Rocky Mountain Spotted Fever ◽  
Phagocytic Cells ◽  
Pathogenic Potential ◽  
Rickettsia Species

Rickettsia are significant sources of tick-borne diseases in humans worldwide. In North America, two species in the spotted fever group of Rickettsia have been conclusively associated with disease of humans: Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, and Rickettsia parkeri, the cause of R. parkeri rickettsiosis. Previous work in our lab demonstrated non-endothelial parasitism by another pathogenic SFG Rickettsia species, Rickettsia conorii, within THP-1-derived macrophages, and we have hypothesized that this growth characteristic may be an underappreciated aspect of rickettsial pathogenesis in mammalian hosts. In this work, we demonstrated that multiple other recognized human pathogenic species of Rickettsia, including R. rickettsii, R. parkeri, Rickettsia africae, and Rickettsiaakari can grow within target endothelial cells as well as within PMA-differentiated THP-1 cells. In contrast, Rickettsia bellii, a Rickettsia species not associated with disease of humans, and R. rickettsii strain Iowa, an avirulent derivative of pathogenic R. rickettsii, could invade both cell types but proliferate only within endothelial cells. Further analysis revealed that similar to previous studies on R. conorii, other recognized pathogenic Rickettsia species could grow within the cytosol of THP-1-derived macrophages and avoided localization with two different markers of lysosomal compartments; LAMP-2 and cathepsin D. R. bellii, on the other hand, demonstrated significant co-localization with lysosomal compartments. Collectively, these findings suggest that the ability of pathogenic rickettsial species to establish a niche within macrophage-like cells could be an important factor in their ability to cause disease in mammals. These findings also suggest that analysis of growth within mammalian phagocytic cells may be useful to predict the pathogenic potential of newly isolated and identified Rickettsia species.

Administration of interleukin-12 and -18 enhancing the antitumor immunity of genetically modified dendritic cells that had been pulsed with Semliki Forest virus—mediated tumor complementary DNA

2002 ◽  
Vol 97 (5) ◽  
pp. 1184-1190 ◽  
Author(s):  
Ryuya Yamanaka ◽  
Naoki Yajima ◽  
Naoto Tsuchiya ◽  
Junpei Honma ◽  
Ryuichi Tanaka ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Antitumor Immunity ◽  
Semliki Forest Virus ◽  
Malignant Gliomas ◽  
Glioma Cells ◽  
Antitumor Effects ◽  
Content Type ◽  
Immunogene Therapy ◽  
Fine Print

Object. Immunogene therapy for malignant gliomas was further investigated in this study to improve its therapeutic efficacy. Methods. Dendritic cells (DCs) were isolated from bone marrow and pulsed with phosphate-buffered saline or Semliki Forest virus (SFV)—mediated 203 glioma complementary (c)DNA with or without systemic administration of interleukin (IL)-12 and IL-18 to treat mice bearing the 203 glioma. To study the immune mechanisms involved in tumor regression, the authors investigated tumor growth of an implanted 203 glioma model in T cell subset—depleted mice and in interferon (IFN) γ—neutralized mice. To examine the protective immunity produced by tumor inoculation, a repeated challenge of 203 glioma cells was given by injecting the cells into the left thighs of surviving mice and the growth of these cells was monitored. The authors demonstrated that the combined administration of SFV-cDNA, IL-12, and IL-18 produced significant antitumor effects against the growth of murine glioma cells in vivo and also can induce specific antitumor immunity. The synergic effects of the combination of SFV-cDNA, IL-12, and IL-18 in vivo were also observed to coincide with markedly augmented IFNγ production. The antitumor effects of this combined therapy are mediated by CD4+ and CD8+ T cells and by NK cells. These results indicate that the use of IL-18 and IL-12 in DC-based immunotherapy for malignant glioma is beneficial. Conclusions. Immunogene therapy combined with DC therapy, IL-12, and IL-18 may be an excellent candidate in the development of a new treatment protocol. The self-replicating SFV system may therefore provide a novel approach for the treatment of malignant gliomas.

scholarly journals Combined Action of Human Commensal Bacteria and Amorphous Silica Nanoparticles on the Viability and Immune Responses of Dendritic Cells

2017 ◽  
Vol 24 (10) ◽  
Author(s):  
Giulia Malachin ◽  
Elisa Lubian ◽  
Fabrizio Mancin ◽  
Emanuele Papini ◽  
Regina Tavano
Keyword(s):  
Dendritic Cells ◽  
Silica Nanoparticles ◽  
Amorphous Silica ◽  
Pathogenic Bacteria ◽  
Bacterial Species ◽  
Commensal Bacteria ◽  
Content Type ◽  
E Coli ◽  
Synergistic Induction ◽  
Ifn Γ

ABSTRACT Dendritic cells (DCs) regulate the host-microbe balance in the gut and skin, tissues likely exposed to nanoparticles (NPs) present in drugs, food, and cosmetics. We analyzed the viability and the activation of DCs incubated with extracellular media (EMs) obtained from cultures of commensal bacteria (Escherichia coli, Staphylococcus epidermidis) or pathogenic bacteria (Pseudomonas aeruginosa, Staphylococcus aureus) in the presence of amorphous silica nanoparticles (SiO2 NPs). EMs and NPs synergistically increased the levels of cytotoxicity and cytokine production, with different nanoparticle dose-response characteristics being found, depending on the bacterial species. E. coli and S. epidermidis EMs plus NPs at nontoxic doses stimulated the secretion of interleukin-1β (IL-1β), IL-12, IL-10, and IL-6, while E. coli and S. epidermidis EMs plus NPs at toxic doses stimulated the secretion of gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), IL-4, and IL-5. On the contrary, S. aureus and P. aeruginosa EMs induced cytokines only when they were combined with NPs at toxic concentrations. The induction of maturation markers (CD86, CD80, CD83, intercellular adhesion molecule 1, and major histocompatibility complex class II) by commensal bacteria but not by pathogenic ones was improved in the presence of noncytotoxic SiO2 NP doses. DCs consistently supported the proliferation and differentiation of CD4+ and CD8+ T cells secreting IFN-γ and IL-17A. The synergistic induction of CD86 was due to nonprotein molecules present in the EMs from all bacteria tested. At variance with this finding, the synergistic induction of IL-1β was prevalently mediated by proteins in the case of E. coli EMs and by nonproteins in the case of S. epidermidis EMs. A bacterial costimulus did not act on DCs after adsorption on SiO2 NPs but rather acted as an independent agonist. The inflammatory and immune actions of DCs stimulated by commensal bacterial agonists might be altered by the simultaneous exposure to engineered or environmental NPs.

scholarly journals Ursodeoxycholic Acid (UDCA) Mitigates the Host Inflammatory Response during Clostridioides difficile Infection by Altering Gut Bile Acids

2020 ◽  
Vol 88 (6) ◽  
Author(s):  
Jenessa A. Winston ◽  
Alissa J. Rivera ◽  
Jingwei Cai ◽  
Rajani Thanissery ◽  
Stephanie A. Montgomery ◽  
...  
Keyword(s):  
Immune Response ◽  
Bile Acid ◽  
Inflammatory Response ◽  
Innate Immune Response ◽  
Innate Immune ◽  
Colonization Resistance ◽  
Content Type ◽  
Clostridioides Difficile

ABSTRACT Clostridioides difficile infection (CDI) is associated with increasing morbidity and mortality posing an urgent threat to public health. Recurrence of CDI after successful treatment with antibiotics is high, thus necessitating discovery of novel therapeutics against this enteric pathogen. Administration of the secondary bile acid ursodeoxycholic acid (UDCA; ursodiol) inhibits the life cycles of various strains of C. difficile in vitro, suggesting that the FDA-approved formulation of UDCA, known as ursodiol, may be able to restore colonization resistance against C. difficile in vivo. However, the mechanism(s) by which ursodiol is able to restore colonization resistance against C. difficile remains unknown. Here, we confirmed that ursodiol inhibits C. difficile R20291 spore germination and outgrowth, growth, and toxin activity in a dose-dependent manner in vitro. In a murine model of CDI, exogenous administration of ursodiol resulted in significant alterations in the bile acid metabolome with little to no changes in gut microbial community structure. Ursodiol pretreatment resulted in attenuation of CDI pathogenesis early in the course of disease, which coincided with alterations in the cecal and colonic inflammatory transcriptome, bile acid-activated receptors nuclear farnesoid X receptor (FXR) and transmembrane G-protein-coupled membrane receptor 5 (TGR5), which are able to modulate the innate immune response through signaling pathways such as NF-κB. Although ursodiol pretreatment did not result in a consistent decrease in the C. difficile life cycle in vivo, it was able to attenuate an overly robust inflammatory response that is detrimental to the host during CDI. Ursodiol remains a viable nonantibiotic treatment and/or prevention strategy against CDI. Likewise, modulation of the host innate immune response via bile acid-activated receptors FXR and TGR5 represents a new potential treatment strategy for patients with CDI.

scholarly journals Characterization of Mutations in therpoB Gene in Naturally Rifampin-ResistantRickettsia Species

1999 ◽  
Vol 43 (10) ◽  
pp. 2400-2403 ◽  
Author(s):  
Michel Drancourt ◽  
Didier Raoult
Keyword(s):  
Spotted Fever ◽  
Single Point ◽  
Experimental Studies ◽  
Single Point Mutation ◽  
Rickettsia Conorii ◽  
Spotted Fever Group ◽  
Resistant Species ◽  
Encoding Gene ◽  
Group Species

ABSTRACT Rickettsiae are gram-negative, obligately intracellular bacteria responsible for arthropod-borne spotted fevers and typhus. Experimental studies have delineated a cluster of naturally rifampin-resistant spotted fever group species. We sequenced the 4,122- to 4,125-bp RNA polymerase β-subunit-encoding gene (rpoB) from typhus and spotted fever group representatives and obtained partial sequences for all naturally rifampin-resistant species. A single point mutation resulting in a phenylalanine-to-leucine change at position 973 of theRickettsia conorii rpoB sequence and present in all the rifampin-resistant species was absent in all the rifampin-susceptible species. rpoB-based phylogenetic relationships among these rickettsial species yielded topologies which were in accordance with previously published phylogenies.

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