Interaction of Mycoplasma hominis PG21 with Human Dendritic Cells: Interleukin-23-Inducing Mycoplasmal Lipoproteins and Inflammasome Activation of the Cell

ABSTRACT Mycoplasma hominis lacks a cell wall, and lipoproteins anchored to the extracellular side of the plasma membrane are in direct contact with the host components. A Triton X-114 extract of M. hominis enriched with lipoproteins was shown to stimulate the production of interleukin-23 (IL-23) by human dendritic cells (hDCs). The inflammasome activation of the host cell has never been reported upon M. hominis infection. We studied here the interaction between M. hominis PG21 and hDCs by analyzing both the inflammation-inducing mycoplasmal lipoproteins and the inflammasome activation of the host cell. IL-23-inducing lipoproteins were determined using a sequential extraction strategy with two nondenaturing detergents, Sarkosyl and Triton X-114, followed by SDS-PAGE separation and mass spectrometry identification. The activation of the hDC inflammasome was assessed using PCR array and enzyme-linked immunosorbent assay (ELISA). We defined a list of 24 lipoproteins that could induce the secretion of IL-23 by hDCs, 5 with a molecular mass between 20 and 35 kDa and 19 with a molecular mass between 40 and 100 kDa. Among them, lipoprotein MHO_4720 was identified as potentially bioactive, and a synthetic lipopeptide corresponding to the N-terminal part of the lipoprotein was subsequently shown to induce IL-23 release by hDCs. Regarding the hDC innate immune response, inflammasome activation with caspase-dependent production of IL-1β was observed. After 24 h of coincubation of hDCs with M. hominis, downregulation of the NLRP3-encoding gene and of the adaptor PYCARD-encoding gene was noticed. Overall, this study provides insight into both protagonists of the interaction of M. hominis and hDCs. IMPORTANCE Mycoplasma hominis is a human urogenital pathogen involved in gynecologic and opportunistic infections. M. hominis lacks a cell wall, and its membrane contains many lipoproteins that are anchored to the extracellular side of the plasma membrane. In the present study, we focused on the interaction between M. hominis and human dendritic cells and examined both sides of the interaction, the mycoplasmal lipoproteins involved in the activation of the host cell and the immune response of the cell. On the mycoplasmal side, we showed for the first time that M. hominis lipoproteins with high molecular mass were potentially bioactive. On the cell side, we reported an activation of the inflammasome, which is involved in the innate immune response.

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Faculty Opinions recommendation of The IL-12 Response of Primary Human Dendritic Cells and Monocytes to Toxoplasma gondii Is Stimulated by Phagocytosis of Live Parasites Rather Than Host Cell Invasion.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.725957291.793518980 ◽

2016 ◽

Author(s):

Frank Seeber

Keyword(s):

Dendritic Cells ◽

Toxoplasma Gondii ◽

Host Cell ◽

Cell Invasion ◽

Host Cell Invasion ◽

Human Dendritic Cells

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Inflammasome Activation Contributes to Interleukin-23 Production in Response to Clostridium difficile

mBio ◽

10.1128/mbio.02386-14 ◽

2015 ◽

Vol 6 (1) ◽

Cited By ~ 31

Author(s):

Carrie A. Cowardin ◽

Sarah A. Kuehne ◽

Erica L. Buonomo ◽

Chelsea S. Marie ◽

Nigel P. Minton ◽

...

Keyword(s):

Clostridium Difficile ◽

Disease Severity ◽

Tissue Damage ◽

The United States ◽

Host Cells ◽

Inflammasome Activation ◽

Content Type ◽

Danger Signals ◽

Interleukin 23 ◽

Molecular Patterns

ABSTRACT Clostridium difficileis the most common hospital-acquired pathogen, causing antibiotic-associated diarrhea in over 250,000 patients annually in the United States. Disease is primarily mediated by toxins A and B, which induce potent proinflammatory signaling in host cells and can activate an ASC-containing inflammasome. Recent findings suggest that the intensity of the host response to infection correlates with disease severity. Our lab has identified the proinflammatory cytokine interleukin-23 (IL-23) as a pathogenic mediator during C. difficile infection (CDI). The mechanisms by which C. difficile induces IL-23, however, are not well understood, and the role of toxins A and B in this process is unclear. Here, we show that toxins A and B alone are not sufficient for IL-23 production but synergistically increase the amount of IL-23 produced in response to MyD88-dependent danger signals, including pathogen-associated molecular patterns (PAMPs) and host-derived damage associated molecular patterns (DAMPs). Danger signals also enhanced the secretion of IL-1β in response to toxins A and B, and subsequent IL-1 receptor signaling accounted for the majority of the increase in IL-23 that occurred in the presence of the toxins. Inhibition of inflammasome activation in the presence of extracellular K+likewise decreased IL-23 production. Finally, we found that IL-1β was increased in the serum of patients with CDI, suggesting that this systemic response could influence downstream production of pathogenic IL-23. Identification of the synergy of danger signals with toxins A and B via inflammasome signaling represents a novel finding in the mechanistic understanding of C. difficile-induced inflammation.IMPORTANCEClostridium difficileis among the leading causes of death due to health care-associated infection, and factors determining disease severity are not well understood. C. difficile secretes toxins A and B, which cause inflammation and tissue damage, and recent findings suggest that some of this tissue damage may be due to an inappropriate host immune response. We have found that toxins A and B, in combination with both bacterium- and host-derived danger signals, can induce expression of the proinflammatory cytokines IL-1β and IL-23. Our results demonstrate that IL-1β signaling enhances IL-23 production and could lead to increased pathogenic inflammation during CDI.

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Failure To Recruit Anti-Inflammatory CD103+Dendritic Cells and a Diminished CD4+Foxp3+Regulatory T Cell Pool in Mice That Display Excessive Lung Inflammation and Increased Susceptibility to Mycobacterium tuberculosis

Infection and Immunity ◽

10.1128/iai.05552-11 ◽

2012 ◽

Vol 80 (3) ◽

pp. 1128-1139 ◽

Cited By ~ 46

Author(s):

Chaniya Leepiyasakulchai ◽

Lech Ignatowicz ◽

Andrzej Pawlowski ◽

Gunilla Källenius ◽

Markus Sköld

Keyword(s):

Immune Response ◽

Dendritic Cells ◽

Mycobacterium Tuberculosis ◽

T Cell ◽

Bacterial Growth ◽

Lung Inflammation ◽

Chronic Infection ◽

Host Immune Response ◽

Content Type ◽

Tnf Α

Susceptibility toMycobacterium tuberculosisis characterized by excessive lung inflammation, tissue damage, and failure to control bacterial growth. To increase our understanding of mechanisms that may regulate the host immune response in the lungs, we characterized dendritic cells expressing CD103 (αEintegrin) (αE-DCs) and CD4+Foxp3+regulatory T (Treg) cells duringM. tuberculosisinfection. In resistant C57BL/6 and BALB/c mice, the number of lung αE-DCs increased dramatically duringM. tuberculosisinfection. In contrast, highly susceptible DBA/2 mice failed to recruit αE-DCs even during chronic infection. Even though tumor necrosis factor alpha (TNF-α) is produced by multiple DCs and macrophage subsets and is required for control of bacterial growth, αE-DCs remained TNF-α negative. Instead, αE-DCs contained a high number of transforming growth factor beta-producing cells in infected mice. Further, we show that Tregcells in C57BL/6 and DBA/2 mice induce gamma interferon during pulmonary tuberculosis. In contrast to resistant mice, the Tregcell population was diminished in the lungs, but not in the draining pulmonary lymph nodes (PLN), of highly susceptible mice during chronic infection. Tregcells have been reported to inhibitM. tuberculosis-specific T cell immunity, leading to increased bacterial growth. Still, despite the reduced number of lung Tregcells in DBA/2 mice, the bacterial load in the lungs was increased compared to resistant animals. Our results show that αE-DCs and Tregcells that may regulate the host immune response are increased inM. tuberculosis-infected lungs of resistant mice but diminished in infected lungs of susceptible mice.

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Phagocytes from Mice Lacking the Sts Phosphatases Have an Enhanced Antifungal Response to Candida albicans

mBio ◽

10.1128/mbio.00782-18 ◽

2018 ◽

Vol 9 (4) ◽

Cited By ~ 8

Author(s):

David Frank ◽

Shamoon Naseem ◽

Gian Luigi Russo ◽

Cindy Li ◽

Kaustubh Parashar ◽

...

Keyword(s):

Bone Marrow ◽

Immune Response ◽

Candida Albicans ◽

Tyrosine Kinase ◽

Critical Role ◽

Inflammasome Activation ◽

Wild Type ◽

Content Type ◽

Enhanced Production ◽

Immunological Mechanisms

ABSTRACT Mice lacking expression of the homologous phosphatases Sts-1 and Sts-2 (Sts−/− mice) are resistant to disseminated candidiasis caused by the fungal pathogen Candida albicans. To better understand the immunological mechanisms underlying the enhanced resistance of Sts−/− mice, we examined the kinetics of fungal clearance at early time points. In contrast to the rapid C. albicans growth seen in normal kidneys during the first 24 h postinfection, we observed a reduction in kidney fungal CFU within Sts−/− mice beginning at 12 to 18 h postinfection. This corresponds to the time period when large numbers of innate leukocytes enter the renal environment to counter the infection. Because phagocytes of the innate immune system are important for host protection against pathogenic fungi, we evaluated responses of bone marrow leukocytes. Relative to wild-type cells, Sts−/− marrow monocytes and bone marrow-derived dendritic cells (BMDCs) displayed a heightened ability to inhibit C. albicans growth ex vivo. This correlated with significantly enhanced production of reactive oxygen species (ROS) by Sts−/− BMDCs downstream of Dectin-1, a C-type lectin receptor that plays a critical role in stimulating host responses to fungi. We observed no visible differences in the responses of other antifungal effector pathways, including cytokine production and inflammasome activation, despite enhanced activation of the Syk tyrosine kinase downstream of Dectin-1 in Sts−/− cells. Our results highlight a novel mechanism regulating the immune response to fungal infections. Further understanding of this regulatory pathway could aid the development of therapeutic approaches to enhance protection against invasive candidiasis. IMPORTANCE Systemic candidiasis caused by fungal Candida species is becoming an increasingly serious medical problem for which current treatment is inadequate. Recently, the Sts phosphatases were established as key regulators of the host antifungal immune response. In particular, genetic inactivation of Sts significantly enhanced survival of mice infected intravenously with Candida albicans. The Sts−/− in vivo resistance phenotype is associated with reduced fungal burden and an absence of inflammatory lesions. To understand the underlying mechanisms, we studied phagocyte responses. Here, we demonstrate that Sts−/− phagocytes have heightened responsiveness to C. albicans challenge relative to wild-type cells. Our data indicate the Sts proteins negatively regulate phagocyte activation via regulating selective elements of the Dectin-1–Syk tyrosine kinase signaling axis. These results suggest that phagocytes lacking Sts respond to fungal challenge more effectively and that this enhanced responsiveness partially underlies the profound resistance of Sts−/− mice to systemic fungal challenge.

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Staphylococcus aureusImpairs the Function of and Kills Human Dendritic Cells via the LukAB Toxin

mBio ◽

10.1128/mbio.01918-18 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 12

Author(s):

Evelien T. M. Berends ◽

Xuhui Zheng ◽

Erin E. Zwack ◽

Mickaël M. Ménager ◽

Michael Cammer ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Dendritic Cells ◽

Adaptive Immunity ◽

T Cell Activation ◽

Antigen Presenting Cells ◽

Infection Model ◽

High Morbidity ◽

Content Type ◽

Human Dendritic Cells ◽

Antigen Presenting

ABSTRACTStaphylococcus aureusis a human pathogen responsible for high morbidity and mortality worldwide. Recurrent infections with this bacterium are common, suggesting thatS. aureusthwarts the development of sterilizing immunity.S. aureusstrains that cause disease in humans produce up to five different bicomponent toxins (leukocidins) that target and lyse neutrophils, innate immune cells that represent the first line of defense againstS. aureusinfections. However, little is known about the role of leukocidins in blunting adaptive immunity. Here, we explored the effects of leukocidins on human dendritic cells (DCs), antigen-presenting cells required for the development of adaptive immunity. Using anex vivoinfection model of primary human monocyte-derived dendritic cells, we found thatS. aureus, including strains from different clonal complexes and drug resistance profiles, effectively kills DCs despite efficient phagocytosis. Although all purified leukocidins could kill DCs, infections with live bacteria revealed thatS. aureustargets and kills DCs primarily via the activity of leukocidin LukAB. Moreover, using coculture experiments performed with DCs and autologous CD4+T lymphocytes, we found that LukAB inhibits DC-mediated activation and proliferation of primary human T cells. Taken together, the data determined in the study reveal a novel immunosuppressive strategy ofS. aureuswhereby the bacterium blunts the development of adaptive immunity via LukAB-mediated injury of DCs.IMPORTANCEAntigen-presenting cells such as dendritic cells (DCs) fulfill an indispensable role in the development of adaptive immunity by producing proinflammatory cytokines and presenting microbial antigens to lymphocytes to trigger a faster, specific, and long-lasting immune response. Here, we studied the effect ofStaphylococcus aureustoxins on human DCs. We discovered that the leukocidin LukAB hinders the development of adaptive immunity by targeting human DCs. The ability ofS. aureusto blunt the function of DCs could help explain the high frequency of recurrentS. aureusinfections. Taken together, the results from this study suggest that therapeutically targeting theS. aureusleukocidins may boost effective innate and adaptive immune responses by protecting innate leukocytes, enabling proper antigen presentation and T cell activation.

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CD40 ligand-triggered human dendritic cells mount interleukin-23 responses that are further enhanced by danger signals

Molecular Immunology ◽

10.1016/j.molimm.2009.12.008 ◽

2010 ◽

Vol 47 (6) ◽

pp. 1255-1261 ◽

Cited By ~ 17

Author(s):

Linda Y. Sender ◽

Kathrin Gibbert ◽

Yasemin Suezer ◽

Heinfried H. Radeke ◽

Ulrich Kalinke ◽

...

Keyword(s):

Dendritic Cells ◽

Cd40 Ligand ◽

Danger Signals ◽

Interleukin 23 ◽

Human Dendritic Cells

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Differential regulation of interleukin 12 and interleukin 23 production in human dendritic cells

Journal of Experimental Medicine ◽

10.1084/jem.20071450 ◽

2008 ◽

Vol 205 (6) ◽

pp. 1447-1461 ◽

Cited By ~ 197

Author(s):

Franca Gerosa ◽

Barbara Baldani-Guerra ◽

Lyudmila A. Lyakh ◽

Giovanna Batoni ◽

Semih Esin ◽

...

Keyword(s):

Dendritic Cells ◽

Transforming Growth Factor ◽

Transforming Growth Factor Β ◽

Interleukin 12 ◽

Mycobacterium Tuberculosis H37rv ◽

Interleukin 23 ◽

Human Dendritic Cells ◽

Differential Ability ◽

Antigen Presenting ◽

Tlr2 Ligands

We analyzed interleukin (IL) 12 and IL-23 production by monocyte-derived dendritic cells (mono-DCs). Mycobacterium tuberculosis H37Rv and zymosan preferentially induced IL-23. IL-23 but not IL-12 was efficiently induced by the combination of nucleotide-binding oligodimerization domain and Toll-like receptor (TLR) 2 ligands, which mimics activation by M. tuberculosis, or by the human dectin-1 ligand β-glucan alone or in combination with TLR2 ligands, mimicking induction by zymosan. TLR2 ligands inhibited IL-12 and increased IL-23 production. DC priming with interferon (IFN) γ strongly increased IL-12 production, but was not required for IL-23 production and inhibited IL-23 production induced by β-glucan. The pattern of IL-12 and IL-23 induction was reflected in accumulation of the IL-12p35 and IL-23p19 transcripts, respectively, but not IL-12/23p40. Although IL-23, transforming growth factor β, and IL-6 contained in the supernatants of activated mono-DCs played a role in the induction of IL-17 by human CD4+ T cells, IL-1β, in combination with one or more of those factors, was required for IL-17 production, and its production determined the differential ability of the stimuli used to elicit mono-DCs to produce soluble factors directing IL-17 production. Thus, the differential ability of pathogens to induce antigen-presenting cells to produce cytokines regulates the immune response to infection.

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