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Find video protocols related to scientific articles indexed in Pubmed.
Human TLR10 is an anti-inflammatory pattern-recognition receptor.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 10-06-2014
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Toll-like receptor (TLR)10 is the only pattern-recognition receptor without known ligand specificity and biological function. We demonstrate that TLR10 is a modulatory receptor with mainly inhibitory effects. Blocking TLR10 by antagonistic antibodies enhanced proinflammatory cytokine production, including IL-1?, specifically after exposure to TLR2 ligands. Blocking TLR10 after stimulation of peripheral blood mononuclear cells with pam3CSK4 (Pam3Cys) led to production of 2,065 ± 106 pg/mL IL-1? (mean ± SEM) in comparison with 1,043 ± 51 pg/mL IL-1? after addition of nonspecific IgG antibodies. Several mechanisms mediate the modulatory effects of TLR10: on the one hand, cotransfection in human cell lines showed that TLR10 acts as an inhibitory receptor when forming heterodimers with TLR2; on the other hand, cross-linking experiments showed specific induction of the anti-inflammatory cytokine IL-1 receptor antagonist (IL-1Ra, 16 ± 1.7 ng/mL, mean ± SEM). After cross-linking anti-TLR10 antibody, no production of IL-1? and other proinflammatory cytokines could be found. Furthermore, individuals bearing TLR10 polymorphisms displayed an increased capacity to produce IL-1?, TNF-?, and IL-6 upon ligation of TLR2, in a gene-dose-dependent manner. The modulatory effects of TLR10 are complex, involving at least several mechanisms: there is competition for ligands or for the formation of heterodimer receptors with TLR2, as well as PI3K/Akt-mediated induction of the anti-inflammatory cytokine IL-1Ra. Finally, transgenic mice expressing human TLR10 produced fewer cytokines when challenged with a TLR2 agonist. In conclusion, to our knowledge we demonstrate for the first time that TLR10 is a modulatory pattern-recognition receptor with mainly inhibitory properties.
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Persistent Lyme Empiric Antibiotic Study Europe (PLEASE) - design of a randomized controlled trial of prolonged antibiotic treatment in patients with persistent symptoms attributed to Lyme borreliosis.
BMC Infect. Dis.
PUBLISHED: 08-29-2014
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BackgroundLyme borreliosis, a potentially severe tick-borne infection caused by Borrelia burgdorferi, can cause multi-system inflammatory disease. The incidence has been increasing, as has the number of patients with persistent symptoms attributed to Borrelia. These symptoms, also referred to as post-Lyme disease syndrome, may follow an erythema migrans or other Lyme manifestations, and include pain, fatigue, and cognitive disturbances. The optimal duration of treatment for these symptoms is a subject of controversy. The PLEASE study is designed to determine whether prolonged antibiotic treatment leads to better patient outcome than standard treatment.Methods/DesignThe PLEASE study is a double-blind, randomized, placebo-controlled trial. Based on power analysis and compensating for possible loss to follow-up, a minimum of 255 patients with borreliosis-attributed persistent symptoms are included. These symptoms are either (a) temporally related to an erythema migrans or otherwise proven symptomatic borreliosis, or (b) accompanied by a positive B. burgdorferi IgG or IgM immunoblot. All patients receive open-label ceftriaxone for two weeks. Patients are then randomized (ratio 1:1:1) to blinded oral follow-up treatment for 12 weeks with (I) doxycycline, (II) clarithromycin combined with hydroxychloroquine, or (III) placebo. The primary outcome is the physical component summary score (PCS) of the RAND-36 Health Status Inventory (RAND SF-36) at week 14. Secondary outcomes include physical and mental aspects of health-related quality of life (assessed by the subscales of the RAND SF-36), fatigue, neuropsychological evaluation, physical activity, and cost-effectiveness.DiscussionThis article describes the background and design issues of the PLEASE study protocol. The results of this study may provide evidence for prescribing or withholding prolonged antibiotic treatment.Trial registrationClinicalTrials.gov: NCT01207739, Netherlands Trial Register: NTR2469.
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Antibiotic mixing through impacted bone grafts does not seem indicated in two-stage cemented hip revisions for septic loosening.
Hip Int
PUBLISHED: 07-31-2014
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Impaction bone grafts (IBG) in two-stage revision for prosthetic hip infection (PHI) might be more susceptible for infection, therefore antibiotic mixing through these grafts has been suggested. However, outcomes have not been compared with IBG without antibiotics and no long-term results are available. Therefore, we evaluated long-term infection-free outcome after the use of IBG without antibiotic supplement in two-stage revision for PHI. Patients were divided into positive (group 1, n = 8) and negative (group 2, n = 28) cultures at re-implantation and followed up to 18 years after re-implantation. Five of 36 patients died from non-orthopaedic causes (median 37, range 24-149 months). Five patients had a re-operation not related to infection (median 39, range 7-140 months). These were censored in the Kaplan-Meier estimator at the last outpatient evaluation. We found an overall re-infection rate of 2.8% within two years, which matches comparative studies in which antibiotic impregnated bone grafts had been used. In group 1, there was one re-infection after 44 months. In group 2, all three infections occurred within 56 months with an estimated infection-free percentage at 10 years of 87% (95% CI 66-96). Follow-up should be extended beyond two years and randomised clinical trials are needed for further comparison with IBG impregnated with antibiotics.
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Cytokine production assays reveal discriminatory immune defects in adults with recurrent infections and noninfectious inflammation.
Clin. Vaccine Immunol.
PUBLISHED: 05-28-2014
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Cytokine production assays have been primarily used in research settings studying novel immunodeficiencies. We sought to determine the diagnostic value of cytokine production assays in patients with recurrent and/or severe infectious diseases (IDs) without known immunodeficiencies and unclassified noninfectious inflammatory disorders (NIIDs). We retrospectively examined cytokine production in whole-blood and peripheral blood mononuclear cell samples from 157 adult patients. A cytokine production rate of <5% of that of healthy controls was considered defective. While monocyte-derived cytokine (tumor necrosis factor alpha [TNF-?], interleukin-1? [IL-1?], and IL-6) production was rarely affected, 30% of all included patients had deficient production of interferon gamma (IFN-?), IL-17A, or IL-22. Twenty-five percent of the NIID patients displayed defective IFN-? production, whereas IL-17A production was generally unaffected. In the group of ID patients, defective IFN-? production was found in 19% and 14% of the patients with viral and bacterial infections, respectively, and in 38%, 24%, and 50% of patients with mycobacterial, mucocutaneous, and invasive fungal infections, respectively. Defective IL-17A and IL-22 production was mainly confined to ID patients with mucocutaneous fungal infections. In conclusion, cytokine production assays frequently detect defective Th1 responses in patients with mycobacterial or fungal infections, in contrast to patients with respiratory tract infections or isolated bacterial infections. Defective IL-17A and IL-22 production was primarily found in patients with fungal infections, while monocyte-derived cytokine production was unaffected. Thus, lymphocyte-derived cytokine production assays are helpful in the diagnostic workup of patients with recurrent infections and suspected immunodeficiencies and have the potential to reveal immune defects that might guide adjunctive immunomodulatory therapy.
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Role of autophagy genetic variants for the risk of Candida infections.
Med. Mycol.
PUBLISHED: 04-08-2014
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Candida albicans can cause candidemia in neutropenic and critically ill patients and oropharyngeal candidiasis in human immunodeficiency virus (HIV)-positive patients with low CD4(+) counts. Because all patients at risk do not develop Candida infections, it is possible that a patient's genetic background might play a role in his or her susceptibility to infection. Autophagy mediates pathogen clearance and modulation of inflammation. Our aim was to assess the effect of genetic variations in the ATG16L1 and IRGM autophagy genes on the susceptibility of patients with candidemia and oropharyngeal candidiasis. We assessed genetic variations in the ATG16L1 and IRGM genes in a cohort of candidemia patients of both African and European origin. In addition, we evaluated the effect of these polymorphisms on the susceptibility to oropharyngeal candidiasis of an HIV-positive cohort from Tanzania. Functional studies have been performed to assess the effect of the ATG16L1 and IRGM genetic variants on both in vitro and in vivo cytokine production. The results indicate that ATG16L1 variants modulate production of tumor necrosis factor-alpha, but not other cytokines, while no effects were seen in the presence of IRGM polymorphisms. In addition, no significant associations between the single-nucleotide polymorphisms in the ATG16L1 and IRGM genetic variants and the incidence of candidemia or oropharyngeal candidiasis were identified. Despite moderate effects on the modulation of proinflammatory cytokine production, genetic variation in the autophagy genes ATG16L1 and IRGM has a minor impact on the susceptibility to both mucosal and systemic Candida infections.
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Interferon-gamma as adjunctive immunotherapy for invasive fungal infections: a case series.
BMC Infect. Dis.
PUBLISHED: 03-14-2014
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Invasive fungal infections are very severe infections associated with high mortality rates, despite the availability of new classes of antifungal agents. Based on pathophysiological mechanisms and limited pre-clinical and clinical data, adjunctive immune-stimulatory therapy with interferon-gamma (IFN-?) may represent a promising candidate to improve outcome of invasive fungal infections by enhancing host defence mechanisms.
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AIDS-related mycoses: the way forward.
Trends Microbiol.
PUBLISHED: 03-04-2014
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The contribution of fungal infections to the morbidity and mortality of HIV-infected individuals is largely unrecognized. A recent meeting highlighted several priorities that need to be urgently addressed, including improved epidemiological surveillance, increased availability of existing diagnostics and drugs, more training in the field of medical mycology, and better funding for research and provision of treatment, particularly in developing countries.
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The discriminative capacity of soluble Toll-like receptor (sTLR)2 and sTLR4 in inflammatory diseases.
BMC Immunol.
PUBLISHED: 02-13-2014
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BackgroundThe extracellular domains of cytokine receptors are released during inflammation, but little is known about the shedding of Toll-like receptors (TLR) and whether they can be used as diagnostic biomarkers.MethodsThe release of sTLR2 and sTLR4 was studied in in-vitro stimulations, as well as in-vivo during experimental human endotoxemia (n¿=¿11, 2 ng/kg LPS), and in plasma of 394 patients with infections (infectious mononucleosis, measles, respiratory tract infections, bacterial sepsis and candidemia) or non-infectious inflammation (Crohn¿s disease, gout, rheumatoid arthritis, autoinflammatory syndromes and pancreatitis). Using C-statistics, the value of sTLR2 and sTLR4 levels for discrimination between infections and non-infectious inflammatory diseases, as well as between viral and bacterial infections was analyzed.ResultsIn-vitro, peripheral blood mononuclear cells released sTLR2 and sTLR4 by exposure to microbial ligands. During experimental human endotoxemia, plasma concentrations peaked after 2 hours (sTLR4) and 4 hours (sTLR2). sTLR4 did not correlate with cytokines, but sTLR2 correlated positively with TNF¿ (rs¿=¿0.80, P¿<¿0.05), IL-6 (rs¿=¿0.65, P¿<¿0.05), and IL-1Ra (rs¿=¿0.57, P¿=¿0.06), and negatively with IL-10 (rs¿=¿-0.58, P¿=¿0.06), respectively. sTLR4 had a similar area under the ROC curve [AUC] for differentiating infectious and non-infectious inflammation compared to CRP: 0.72 (95% CI 0.66-0.79) versus 0.74 (95% CI 0.69-0.80) [P¿=¿0.80], while sTLR2 had a lower AUC: 0.60 (95% CI 0.54-0.66) [P¿=¿0.0004]. CRP differentiated bacterial infections better from viral infections than sTLR2 and sTLR4: AUC 0.94 (95% CI 0.90-0.96) versus 0.58 (95% CI 0.51-0.64) and 0.75 (95% CI 0.70-0.80), respectively [P¿<¿0.0001 for both].ConclusionssTLRs are released into the circulation, and suggest the possibility to use sTLRs as diagnostic tool in inflammatory conditions.
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Immunochip SNP array identifies novel genetic variants conferring susceptibility to candidaemia.
Nat Commun
PUBLISHED: 01-07-2014
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Candidaemia is the fourth most common cause of bloodstream infection, with a high mortality rate of up to 40%. Identification of host genetic factors that confer susceptibility to candidaemia may aid in designing adjunctive immunotherapeutic strategies. Here we hypothesize that variation in immune genes may predispose to candidaemia. We analyse 118,989 single-nucleotide polymorphisms (SNPs) across 186 loci known to be associated with immune-mediated diseases in the largest candidaemia cohort to date of 217 patients of European ancestry and a group of 11,920 controls. We validate the significant associations by comparison with a disease-matched control group. We observe significant association between candidaemia and SNPs in the CD58 (P = 1.97 × 10(-11); odds ratio (OR) = 4.68), LCE4A-C1orf68 (P = 1.98 × 10(-10); OR = 4.25) and TAGAP (P = 1.84 × 10(-8); OR = 2.96) loci. Individuals carrying two or more risk alleles have an increased risk for candidaemia of 19.4-fold compared with individuals carrying no risk allele. We identify three novel genetic risk factors for candidaemia, which we subsequently validate for their role in antifungal host defence.
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Gene polymorphisms in pattern recognition receptors and susceptibility to idiopathic recurrent vulvovaginal candidiasis.
Front Microbiol
PUBLISHED: 01-01-2014
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Approximately 5% of women suffer from recurrent vulvovaginal candidiasis (RVVC). It has been hypothesized that genetic factors play an important role in the susceptibility to RVVC. The aim of this study was to assess the effect of genetic variants of genes encoding for pattern recognition receptors (PRRs) on susceptibility to RVVC.
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Voriconazole or amphotericin B as primary therapy yields distinct early serum galactomannan trends related to outcomes in invasive aspergillosis.
PLoS ONE
PUBLISHED: 01-01-2014
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An improved number of anti-fungal drugs are currently available for the treatment of invasive aspergillosis (IA). While serial galactomannan index (GMI) measurement can be used to monitor response to treatment, the extent to which different anti-fungal regimens can affect galactomannan levels is unknown. In 147 IA patients receiving either voriconazole (VCZ) or conventional amphotericin B (CAB) in a multicentre clinical trial, we performed post-hoc analyses of GMI trends in relation to outcomes. The generalized estimation equations approach was used to estimate changes in the effect size for GMI over time within patients. Patients who received VCZ primary therapy and had good treatment response 12 weeks later showed earlier decreases in GMI values at Week 1 and Week 2 (p = 0.001 and 0.046 respectively) as compared to patients who only received CAB. At end-of-randomized therapy (EORT), which was a pre-set secondary assessment point for all patients who switched from randomized primary (CAB or VCZ) to an alternative anti-fungal drug, treatment failure was associated with increasing GMI at Weeks 1 and 2 in CAB-primary treated patients (p = 0.022 and 0.046 respectively). These distinct trends highlight the variations in GMI kinetics with the use of different anti-fungal drugs and their implications in relation to IA treatment response.
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The role of Dectin-2 for host defense against systemic infection with Candida glabrata.
Infect. Immun.
PUBLISHED: 12-16-2013
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Although Candida glabrata is an important pathogenic Candida species, relatively little is known about its innate immune recognition. Here we explore the potential role of Dectin-2 for host defense against C. glabrata. Dectin-2-deficient (Dectin-2(-/-)) mice were found to be more susceptible to C. glabrata infections, showing a defective fungal clearance in kidneys, but not in the liver. The increased susceptibility to infection was accompanied by lower production of T helper 1 (Th1) and Th17-derived cytokines by splenocytes of Dectin-2(-/-) mice, while macrophage-derived cytokines were less affected. These defects were associated with a moderate, yet significant, decreased phagocytosis of the fungus by the Dectin-2(-/-) macrophages and neutrophils. Neutrophils of Dectin-2(-/-) mice also displayed a lower production of reactive oxygen species (ROS) upon challenge with opsonized C. glabrata or C. albicans. This study suggests that Dectin-2 is important in host defense against C. glabrata and provides new insights in the host defense mechanisms against this important fungal pathogen.
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CX3CR1-dependent renal macrophage survival promotes Candida control and host survival.
J. Clin. Invest.
PUBLISHED: 05-29-2013
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Systemic Candida albicans infection causes high morbidity and mortality and is associated with neutropenia; however, the roles of other innate immune cells in pathogenesis are poorly defined. Here, using a mouse model of systemic candidiasis, we found that resident macrophages accumulated in the kidney, the main target organ of infection, and formed direct contacts with the fungus in vivo mainly within the first few hours after infection. Macrophage accumulation and contact with Candida were both markedly reduced in mice lacking chemokine receptor CX3CR1, which was found almost exclusively on resident macrophages in uninfected kidneys. Infected Cx3cr1-/- mice uniformly succumbed to Candida-induced renal failure, but exhibited clearance of the fungus in all other organs tested. Renal macrophage deficiency in infected Cx3cr1-/- mice was due to reduced macrophage survival, not impaired proliferation, trafficking, or differentiation. In humans, the dysfunctional CX3CR1 allele CX3CR1-M280 was associated with increased risk of systemic candidiasis. Together, these data indicate that CX3CR1-mediated renal resident macrophage survival is a critical innate mechanism of early fungal control that influences host survival in systemic candidiasis.
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An elevated pro-inflammatory cytokine response is linked to development of amphotericin B-induced nephrotoxicity.
J. Antimicrob. Chemother.
PUBLISHED: 04-03-2013
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The underlying mechanism for amphotericin B-induced acute kidney injury (AKI) remains poorly understood and may be immunologically mediated. We assessed whether the development of nephrotoxicity is linked to a distinct cytokine profile in patients receiving amphotericin B deoxycholate (AmBD).
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Candida albicans primes TLR cytokine responses through a Dectin-1/Raf-1-mediated pathway.
J. Immunol.
PUBLISHED: 03-08-2013
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The immune system is essential to maintain homeostasis with resident microbial populations, ensuring that the symbiotic host-microbial relationship is maintained. In parallel, commensal microbes significantly shape mammalian immunity at the host mucosal surface, as well as systemically. Candida albicans is an opportunistic pathogen that lives as a commensal on skin and mucosa of healthy individuals. Little is known about its capacity to modulate responses toward other microorganisms, such as colonizing bacteria (e.g., intestinal microorganisms). The aim of this study was to assess the cytokine production of PBMCs induced by commensal bacteria when these cells were primed by C. albicans. We show that C. albicans and ?-1,3-glucan induce priming of human primary mononuclear cells and this leads to enhanced cytokine production upon in vitro stimulation with TLR ligands and bacterial commensals. This priming requires the ?-1,3-glucan receptor dectin-1 and the noncanonical Raf-1 pathway. In addition, although purified mannans cannot solely mediate the priming, the presence of mannosyl residues in the cell wall of C. albicans is nevertheless required. In conclusion, C. albicans is able to modify cytokine responses to TLR ligands and colonizing bacteria, which is likely to impact the inflammatory reaction during mucosal diseases.
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Genetic basis for recurrent vulvo-vaginal candidiasis.
Curr Infect Dis Rep
PUBLISHED: 01-29-2013
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Vulvovaginal candidiasis (VVC) is a frequent disease affecting more than 75% of all women at least once in their lifetime. Up to 8% of them suffer from recurrent VVC (RVVC) characterized by at least three episodes each year. Several risk factors, such as antibiotic use, diabetes, or pregnancy, are known, but the vast majority of women with RVVC develop the infection without having any risk factor, implying that a genetic component most likely plays an important role in the susceptibility to RVVC. This review summarizes the immunogenetic alterations that lead to an increased susceptibility to vaginal infections with Candida albicans. Different mutations and polymorphisms in innate immune genes alter the mucosal immune response against fungi and are likely to have an important role in susceptibility to RVVC. A better understanding of the genetic and immunological mechanisms leading to RVVC is important for both the understanding of the pathophysiology of the disease and the design of novel therapeutic strategies.
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Genetic susceptibility to Candida infections.
EMBO Mol Med
PUBLISHED: 01-14-2013
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Candida spp. are medically important fungi causing severe mucosal and life-threatening invasive infections, especially in immunocompromised hosts. However, not all individuals at risk develop Candida infections, and it is believed that genetic variation plays an important role in host susceptibility. On the one hand, severe fungal infections are associated with monogenic primary immunodeficiencies such as defects in STAT1, STAT3 or CARD9, recently discovered as novel clinical entities. On the other hand, more common polymorphisms in genes of the immune system have also been associated with fungal infections such as recurrent vulvovaginal candidiasis and candidemia. The discovery of the genetic susceptibility to Candida infections can lead to a better understanding of the pathogenesis of the disease, as well as to the design of novel immunotherapeutic strategies. This review is part of the review series on host-pathogen interactions. See more reviews from this series.
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Functional genomics identifies type I interferon pathway as central for host defense against Candida albicans.
Nat Commun
PUBLISHED: 01-10-2013
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Candida albicans is the most common human fungal pathogen causing mucosal and systemic infections. However, human antifungal immunity remains poorly defined. Here by integrating transcriptional analysis and functional genomics, we identified Candida-specific host defence mechanisms in humans. Candida induced significant expression of genes from the type I interferon pathway in human peripheral blood mononuclear cells. This unexpectedly prominent role of type I interferon pathway in anti-Candida host defence was supported by additional evidence. Polymorphisms in type I interferon genes modulated Candida-induced cytokine production and were correlated with susceptibility to systemic candidiasis. In in vitro experiments, type I interferons skewed Candida-induced inflammation from a Th17 response towards a Th1 response. Patients with chronic mucocutaneous candidiasis displayed defective expression of genes in the type I interferon pathway. These findings indicate that the type I interferon pathway is a main signature of Candida-induced inflammation and has a crucial role in anti-Candida host defence in humans.
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Cytokine gene polymorphisms and the outcome of invasive candidiasis: a prospective cohort study.
Clin. Infect. Dis.
PUBLISHED: 12-05-2011
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?Candida bloodstream infections cause significant morbidity and mortality among hospitalized patients. Although clinical and microbiological factors affecting prognosis have been identified, the impact of genetic variation in the innate immune responses mediated by cytokines on outcomes of infection remains to be studied.
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Variation in genes of ?-glucan recognition pathway and susceptibility to opportunistic infections in HIV-positive patients.
Immunol. Invest.
PUBLISHED: 10-12-2011
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Opportunistic infections are the main cause of morbidity and death among HIV-positive patients. Most of these infections are linked to the immunodeficiency due to low CD4+ counts. However, not all patients with low CD4+ counts are equally susceptible to infections, and we hypothesize that variability in genes of innate immunity may also play an important role. The dectin-1/CARD9 pathway is crucial for recognition of both fungal and bacterial pathogens. The aim of this study was to assess the possible association between the occurrence of opportunistic infections and single nucleotide polymorphisms in DECTIN-1 and CARD9 in a cohort of 187 HIV-infected patients. The incidence of oropharyngeal candidiasis and other opportunistic infections was not influenced by either the Y238X DECTIN-1 or the S12N CARD9 polymorphism. Surprisingly however, the prevalence of pneumonia was significantly higher in patients bearing the defective variant DECTIN-1 allele. These results suggest a role of dectin-1 in the host defense against respiratory bacterial infections, and future studies are warranted to confirm this association.
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Cost-effectiveness of routine (18)F-FDG PET/CT in high-risk patients with gram-positive bacteremia.
J. Nucl. Med.
PUBLISHED: 10-07-2011
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Gram-positive bacteremia has a high morbidity and mortality rate of approximately 30%. Delayed diagnosis of clinically silent metastatic infectious foci is an important indicator for a complicated outcome. (18)F-FDG PET/CT allows detection of focal infection, resulting in lower relapse rates and mortality. Here, we present a cost-effectiveness analysis associated with introduction of (18)F-FDG PET/CT for patients with gram-positive bacteremia.
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Role of interleukin-23 (IL-23) receptor signaling for IL-17 responses in human Lyme disease.
Infect. Immun.
PUBLISHED: 09-06-2011
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Interleukin-23 (IL-23) is known to play a crucial role in the development and maintenance of T helper 17 cells. It has been previously demonstrated that IL-17 is involved in experimental Lyme arthritis, caused by Borrelia burgdorferi bacteria. However, the precise role of the IL-23 receptor (IL-23R) for the B. burgdorferi-induced IL-17 responses or human Lyme disease has not yet been elucidated. IL-23R single nucleotide polymorphism (SNP) rs11209026 was genotyped using the TaqMan assay. Functional studies were performed using peripheral blood mononuclear cells, and cytokines were measured using enzyme-linked immunosorbent assay (ELISA). Dose-dependent production of IL-23 and IL-17 by B. burgdorferi could be observed. Interestingly, when IL-23 bioactivity was inhibited by a specific antibody against IL-23p19, IL-17 production was significantly downregulated. In contrast, production of gamma interferon (IFN-?) was not affected after the blockade of IL-23 activity. Moreover, individuals bearing a single nucleotide polymorphism in the IL-23R gene (Arg381Gln) produced significantly less IL-17 after B. burgdorferi stimulation compared with that of the individuals bearing the wild type. Despite lower IL-17 production, the IL-23R gene polymorphism did not influence the development of chronic Lyme disease in a cohort of patients with Lyme disease. This study demonstrates that IL-23R signaling is needed for B. burgdorferi-induced IL-17 production in vitro and that an IL-23R gene SNP leads to impaired IL-17 production. However, the IL-23R gene polymorphism is not crucial for the pathogenesis of chronic Lyme.
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Genetic variation in the dectin-1/CARD9 recognition pathway and susceptibility to candidemia.
J. Infect. Dis.
PUBLISHED: 09-02-2011
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Candidemia is an important cause of morbidity and mortality in critically ill patients or patients undergoing invasive treatments. Dectin-1 is the main ?-glucan receptor, and patients with a complete deficiency of either dectin-1 or its adaptor molecule CARD9 display persistent mucosal infections with Candida albicans. The role of genetic variation of DECTIN-1 and CARD9 genes on the susceptibility to candidemia is unknown.
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STAT1 hyperphosphorylation and defective IL12R/IL23R signaling underlie defective immunity in autosomal dominant chronic mucocutaneous candidiasis.
PLoS ONE
PUBLISHED: 07-19-2011
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We recently reported the genetic cause of autosomal dominant chronic mucocutaneous candidiasis (AD-CMC) as a mutation in the STAT1 gene. In the present study we show that STAT1 Arg274Trp mutations in the coiled-coil (CC) domain is the genetic cause of AD-CMC in three families of patients. Cloning and transfection experiments demonstrate that mutated STAT1 inhibits IL12R/IL-23R signaling, with hyperphosphorylation of STAT1 as the likely underlying molecular mechanism. Inhibition of signaling through the receptors for IL-12 and IL-23 leads to strongly diminished Th1/Th17 responses and hence to increased susceptibility to fungal infections. The challenge for the future is to translate this knowledge into novel strategies for the treatment of this severe immunodeficiency.
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Ocular manifestations of candidemia.
Clin. Infect. Dis.
PUBLISHED: 07-19-2011
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Ocular candidiasis is a major complication of candidemia. The incidence, risk factors, and outcome of eye involvement during candidemia are largely unknown. We prospectively studied the ocular manifestations of candidemia in a large, worldwide, randomized multicenter trial that compared voriconazole with amphotericin B followed by fluconazole for the treatment of candidemia.
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18F-FDG PET/CT for diagnosing infectious complications in patients with severe neutropenia after intensive chemotherapy for haematological malignancy or stem cell transplantation.
Eur. J. Nucl. Med. Mol. Imaging
PUBLISHED: 07-10-2011
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Between 30 and 50% of febrile neutropenic episodes are accounted for by infection. C-reactive protein (CRP) is a nonspecific parameter for infection and inflammation but might be employed as a trigger for diagnosis. The aim of the study was to evaluate whether (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT can be used to detect inflammatory foci in neutropenic patients with elevated CRP and whether it helps to direct treatment.
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STAT1 mutations in autosomal dominant chronic mucocutaneous candidiasis.
N. Engl. J. Med.
PUBLISHED: 06-29-2011
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Chronic mucocutaneous candidiasis (CMC) is characterized by susceptibility to candida infection of skin, nails, and mucous membranes. Patients with recessive CMC and autoimmunity have mutations in the autoimmune regulator AIRE. The cause of autosomal dominant CMC is unknown.
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Immune response to Aspergillus fumigatus in compromised hosts: from bedside to bench.
Future Microbiol
PUBLISHED: 06-08-2011
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The relevance of studies aimed at understanding host immune response against Aspergillus fumigatus takes on much significance given that all patients with invasive aspergillosis are invariably immunocompromised. This article attempts to correlate relevant findings from recent experimental studies to clinical observations made by the physician at the bedside. It is hoped that the increased understanding of host-fungus immune interaction may pave the way for the development of new management strategies against this difficult-to-treat fungal disease.
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TLR1/TLR2 heterodimers play an important role in the recognition of Borrelia spirochetes.
PLoS ONE
PUBLISHED: 05-23-2011
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After infection with Borrelia species, the risk for developing Lyme disease varies significantly between individuals. Recognition of Borrelia by the immune system is mediated by pattern recognition receptors (PRRs), such as TLRs. While TLR2 is the main recognition receptor for Borrelia spp., little is known about the role of TLR1 and TLR6, which both can form functionally active heterodimers with TLR2. Here we investigated the recognition of Borrelia by both murine and human TLR1 and TLR6. Peritoneal macrophages from TLR1- and TLR6- gene deficient mice were isolated and exposed to Borrelia. Human PBMCs were stimulated with Borrelia with or without specific TLR1 and TLR6 blocking using specific antibodies. Finally, the functional consequences of TLR polymorphisms on Borrelia-induced cytokine production were assessed. Splenocytes isolated from both TLR1-/- and TLR6-/- mice displayed a distorted Th1/Th2 cytokine balance after stimulation with B.burgdorferi, while no differences in pro-inflammatory cytokine production were observed. In contrast, blockade of TLR1 with specific neutralizing antibodies led to decreased cytokine production by human PBMCs after exposure to B.burgdorferi. Blockade of human TLR6 did not lead to suppression of cytokine production. When PBMCs from healthy individuals bearing polymorphisms in TLR1 were exposed to B.burgdorferi, a remarkably decreased in vitro cytokine production was observed in comparison to wild-type controls. TLR6 polymorphisms lead to a minor modified cytokine production. This study indicates a dominant role for TLR1/TLR2 heterodimers in the induction of the early inflammatory response by Borrelia spirochetes in humans.
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The dectin-1/inflammasome pathway is responsible for the induction of protective T-helper 17 responses that discriminate between yeasts and hyphae of Candida albicans.
J. Leukoc. Biol.
PUBLISHED: 04-29-2011
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In the mucosa, the immune pathways discriminating between colonizing and invasive Candida, thus inducing tolerance or inflammation, are poorly understood. Th17 responses induced by Candida albicans hyphae are central for the activation of mucosal antifungal immunity. An essential step for the discrimination between yeasts and hyphae and induction of Th17 responses is the activation of the inflammasome by C. albicans hyphae and the subsequent release of active IL-1? in macrophages. Inflammasome activation in macrophages results from differences in cell-wall architecture between yeasts and hyphae and is partly mediated by the dectin-1/Syk pathway. These results define the dectin-1/inflammasome pathway as the mechanism that enables the host immune system to mount a protective Th17 response and distinguish between colonization and tissue invasion by C. albicans.
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The inflammasome drives protective Th1 and Th17 cellular responses in disseminated candidiasis.
Eur. J. Immunol.
PUBLISHED: 04-13-2011
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The Nlrp3 inflammasome has been proposed to play an important role in antifungal host defense. However, studies exploring the role of the inflammasome in antifungal host defense have been limited to the direct effects on IL-1? processing. Although IL-1? has important direct effects on the innate immune response, important effects of the caspase-1-dependent cytokines IL-1? and IL-18 are exerted on the initiation of the adaptive Th1 and Th17 cellular responses. No studies have been employed to assess the impact of the inflammasome on the Th1/Th17 defense mechanisms in vivo during candidiasis. In the present study, we demonstrate an essential role for caspase-1 and ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain) in disseminated candidiasis through regulating antifungal Th1 and Th17 responses. Caspase-1(-/-) and ASC(-/-) mice display diminished Th1/Th17 responses, followed by increased fungal outgrowth and lower survival. These observations identify a critical role for the inflammasome in controlling protective adaptive immune responses during invasive fungal infection.
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Inflammasome-independent modulation of cytokine response by autophagy in human cells.
PLoS ONE
PUBLISHED: 03-15-2011
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Autophagy is a cell housekeeping mechanism that has recently received attention in relation to its effects on the immune response. Genetic studies have identified candidate loci for Crohns disease susceptibility among autophagy genes, while experiments in murine macrophages from ATG16L1 deficient mice have shown that disruption of autophagy increases processing of IL-1? and IL-18 through an inflammasome-dependent manner. Using complementary approaches either inducing or inhibiting autophagy, we describe modulatory effects of autophagy on proinflammatory cytokine production in human cells. Inhibition of basal autophagy in human peripheral blood mononuclear cells (PBMCs) significantly enhances IL-1? after stimulation with TLR2 or TLR4 ligands, while at the same time reducing the production of TNF?. In line with this, induction of autophagy by starvation inhibited IL-1? production. These effects of autophagy were not exerted at the processing step, as inflammasome activation was not influenced. In contrast, the effect of autophagy on cytokine production was on transcription level, and possibly involving the inhibition of p38 mitogen activated protein kinase (MAPK) phosphorylation. In conclusion, autophagy modulates the secretion of proinflammatory cytokines in human cells through an inflammasome-independent pathway, and this is a novel mechanism that may be targeted in inflammatory diseases.
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TREM-1 interaction with the LPS/TLR4 receptor complex.
Eur. Cytokine Netw.
PUBLISHED: 03-12-2011
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Triggering receptor expressed on myeloid cells 1 (TREM-1) is an activating receptor expressed on neutrophils and monocytes that amplifies inflammation induced by stimulation of pattern-recognition receptors. In this study, several lines of evidence are presented that TREM-1 interacts with the toll-like receptor 4 (TLR4) receptor complex, or is a component of this complex. Blocking anti-TREM-1 antibodies specifically inhibited LPS-induced TNF-? production, while the alternative approach of blocking TLR4 by a specific inhibitor led to a down-regulation of the effects of TREM-1 cross-linking. These data are in line with the TLR4-TREM1 co-localization in human neutrophils and suggests that, at least some of the biological effects of TREM-1 may be due to its interaction with the TLR4/LPS-receptor complex.
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Recognition and blocking of innate immunity cells by Candida albicans chitin.
Infect. Immun.
PUBLISHED: 02-28-2011
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Chitin is a skeletal cell wall polysaccharide of the inner cell wall of fungal pathogens. As yet, little about its role during fungus-host immune cell interactions is known. We show here that ultrapurified chitin from Candida albicans cell walls did not stimulate cytokine production directly but blocked the recognition of C. albicans by human peripheral blood mononuclear cells (PBMCs) and murine macrophages, leading to significant reductions in cytokine production. Chitin did not affect the induction of cytokines stimulated by bacterial cells or lipopolysaccharide (LPS), indicating that blocking was not due to steric masking of specific receptors. Toll-like receptor 2 (TLR2), TLR4, and Mincle (the macrophage-inducible C-type lectin) were not required for interactions with chitin. Dectin-1 was required for immune blocking but did not bind chitin directly. Cytokine stimulation was significantly reduced upon stimulation of PBMCs with heat-killed chitin-deficient C. albicans cells but not with live cells. Therefore, chitin is normally not exposed to cells of the innate immune system but is capable of influencing immune recognition by blocking dectin-1-mediated engagement with fungal cell walls.
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The Y238X stop codon polymorphism in the human ?-glucan receptor dectin-1 and susceptibility to invasive aspergillosis.
J. Infect. Dis.
PUBLISHED: 01-17-2011
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Dectin-1 is the major receptor for fungal ?-glucans on myeloid cells. We investigated whether defective Dectin-1 receptor function, because of the early stop codon polymorphism Y238X, enhances susceptibility to invasive aspergillosis (IA) in at-risk patients.
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The classical CD14?? CD16? monocytes, but not the patrolling CD14? CD16? monocytes, promote Th17 responses to Candida albicans.
Eur. J. Immunol.
PUBLISHED: 01-14-2011
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In the present study, we investigated the functional differences between cluster of differentiation (CD)14(++) CD16(-) and CD14(+) CD16(+) monocytes during anti-Candida host defense. CD14(++) CD16(-) are the "classical" monocytes and represent the majority of circulating monocytes in humans, while CD14(+) CD16(+) monocytes patrol the vasculature for maintenance of tissue integrity and repair. Both monocyte subsets inhibited the germination of live Candida albicans, and there was no difference in their capacity to phagocytose and kill Candida. Although production of IL-6 and IL-10 induced by C. albicans was found to be similar between monocyte subsets, IL-1? and prostaglandin E2 (PGE2) production was higher in CD14(++) CD16(-) compared with CD14(+) CD16(+) monocytes. In line with the increased production of IL-1? and PGE2, central mediators for inducing Th17 responses, CD14(++) CD16(-) monocytes induced greater Th17 responses upon stimulation with heat-killed C. albicans yeast. The percentage of cells that expressed mannose receptor (MR) was higher in the CD14(++) CD16(-) monocyte subset, and MR-specific stimulation induced higher Th17 responses only in co-cultures of CD14(++) CD16(-) monocytes and CD4 lymphocytes. In conclusion, both monocyte subsets have potent innate antifungal properties, but only CD14(++) CD16(-) monocytes are capable of inducing a potent Th17 response to C. albicans, an important component of antifungal host defense.
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1,25-dihydroxyvitamin D3 modulates cytokine production induced by Candida albicans: impact of seasonal variation of immune responses.
J. Infect. Dis.
PUBLISHED: 01-12-2011
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Our interest in immunological effects produced by vitamin D(3) (1,25(OH)(2)D(3)) and its therapeutic potential prompted us to examine the role of 1,25(OH)(2)D(3) on cytokine production by Candida albicans.
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Host-microbe interactions in stem cell transplantation: recognizing Candida in infection and inflammation.
Virulence
PUBLISHED: 12-24-2010
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Host-pathogen interactions at epithelial barriers play an important role in health and disease. This also applies to the clinical setting of stem cell transplantation (SCT) in which deregulated sensing of microbes and their cell wall components by pattern recognition receptors (PRRs) can contribute to inflammatory and infectious complications. The role of Candida species herein has recently been rediscovered since a loss-of-function Y238X polymorphism in dectin-1, a C-type lectin receptor recognizing the ?-1,3-glucan motif of Candida, resulted in diminished membrane expression and lower cytokine responses upon ?-1,3-glucan recognition, and was associated with increased Candida colonization of SCT recipients, rendering them at risk for candidaemia. In addition, Candida colonization was associated with an increased incidence of acute graft-versus-host disease (GvHD), but only in those individuals with the wild-type dectin-1 allele. The Th17 mediated immune responses might provide a common link in these processes, as they have recently been implicated in anti-Candida immunity as well as the pathogenesis of GvHD. These new insights suggest that immunogenetics could contribute to a more individualized risk-based strategy for managing SCT recipients, for example concerning antifungal prophylaxis. In addition, modulating host-pathogen interactions by selectively modulating PRR activity could be exploited in SCT to achieve better outcomes.
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Severe Candida spp. infections: new insights into natural immunity.
Int. J. Antimicrob. Agents
PUBLISHED: 12-03-2010
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Invasive infections caused by Candida spp. are associated with high mortality. Colonisation by Candida spp. and the capacity of the host to recognise them as potential pathogens are essential steps in the development of these infections. The major pathogen-associated molecular patterns of Candida are mannoproteins, glucans and chitins, which are recognised by C-type lectin pattern recognition receptors such as the mannose receptor, dectin-1 and dectin-2. By the secretion of proteases and toxins, and the formation of hyphae and biofilms, Candida spp. are able to enhance their virulence and pathogenicity. Studies in patients with relatively rare immunodeficiencies, such as dectin-1 deficiency, CARD9 deficiency, chronic mucocutaneous candidiasis, hyper-IgE/Jobs syndrome and chronic granulomatous disease, have shown the role of dectin-1 and its signalling pathway, which involves interleukins 17 and 22, defensins and phagocytic cells, in defence against Candida. These studies also provide insights into how acquired risk factors for fungal infection operate, and may lead to new approaches for immunotherapy.
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The Candida Th17 response is dependent on mannan- and beta-glucan-induced prostaglandin E2.
Int. Immunol.
PUBLISHED: 11-08-2010
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The fungus Candida albicans is a potent inducer of the T(h)17 response. Prostaglandin E2 (PGE2) is a strong pro-inflammatory mediator, which has proven to be essential for the T(h)17 response. In this study, we have investigated the role of PGE2 in the T(h)17 response induced by C. albicans in humans. PBMC were stimulated with C. albicans in the absence or presence of a non-steroidal anti-inflammatory drug (NSAID). In separate experiments, PGE2 or the prostlaglandin receptors agonists butaprost or misoprostol were added to the cells. PBMC were also stimulated with fungal components and small interfering RNA for mannose receptor (MR) was performed. PGE2 and cytokines were measured by ELISA or luminex, and the source of IL-17 production was determined using FACS analysis. Blocking Candida-induced PGE2 production by an NSAID resulted in decreased IL-17 and IL-22 production and inhibited expression of RAR-related orphan receptor gamma T mRNA. Furthermore, when PGE2 production was blocked, IL-6, IL-23 and IL-10 were decreased, while tumor necrosis factor ? increased. Stimulation with PGE2 or E prostanoid (EP)2/EP4 agonists restored IL-17 production. Candida albicans mannan was the only fungal component that was able to directly induce PGE2 and silencing of the MR resulted in a reduction of Candida-induced PGE2. ?-Glucan engagement of dectin-1 synergistically increased Toll-like receptor 2 (TLR2)-induced PGE2 production. These data provide evidence that PGE2 pathway is important for the T(h)17 response induced by C. albicans and that PGE2 is induced by the fungal components mannan and ?-glucan that are recognized by the MR and the dectin-1/TLR2 pathway, respectively.
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Differential susceptibility to lethal endotoxaemia in mice deficient in IL-1?, IL-1? or IL-1 receptor type I.
APMIS
PUBLISHED: 10-11-2010
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The role of intereukin-1 (IL-1) in mortality caused by endotoxaemia remains controversial. While IL-1 receptor antagonist (IL-1Ra) protects mice from lethal endotoxaemia, mice deficient in IL-1? (IL-1??(?/)?) display normal susceptibility to lipopolysaccharide (LPS). The aim of this study was to identify the source of these discrepancies. Mice deficient in IL-1?, IL-1? or IL-1R type I were injected intraperitoneally with Escherichia coli or Salmonella typhimurium LPS. Survival of the mice was examined and compared with C57/Bl6 wild-type mice. In addition, serum cytokine concentrations were determined after LPS challenge and in vitro cytokine production by peritoneal macrophages was analysed. Clearance of radioactive IL-1? was examined in IL-1??(/)? and wild-type mice. IL-1??(/)? mice were normally susceptible to endotoxaemia and cytokine production did not differ from that in control mice. Surprisingly, LPS mortality in IL-1??(/)? mice was significantly greater than that in control mice, accompanied by higher interferon-? release. These effects were mediated by a distorted homeostasis of IL-1RI receptors, as shown by a strongly delayed clearance of IL-1?. In contrast to the IL-1??(/)? and IL-1??(/)? mice, IL-1RI?(/)? mice were completely resistant to high doses of LPS. In conclusion, IL-1RI-mediated signals are crucial in mediating mortality occurring as a result of lethal endotoxaemia. Investigation of IL-1-mediated pathways in IL-1 knock-out mice is complicated by a distorted homeostasis of IL-1Rs.
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Early proinflammatory cytokines and C?reactive protein trends as predictors of outcome in invasive Aspergillosis.
J. Infect. Dis.
PUBLISHED: 10-01-2010
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Monitoring treatment response in invasive aspergillosis is challenging, because an immunocompromised host may not exhibit reliable symptoms and clinical signs. Cytokines play a pivotal role in mediating host immune response to infection; therefore, the profiling of biomarkers may be an appropriate surrogate for disease status.
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Epithelial sensing of fungal invasion.
Cell Host Microbe
PUBLISHED: 09-14-2010
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The mechanisms discriminating mucosal colonization from invasion by Candida albicans are unclear. In this issue, Moyes et al. show that epithelial cells discriminate between colonizing yeasts and invading hyphae by mechanisms involving c-Fos and MKP1 phosphatase, opening up new avenues for understanding the pathophysiology of mucosal fungal infections.
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Early treatment of candidemia in adults: a review.
Med. Mycol.
PUBLISHED: 09-06-2010
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Invasive candidiasis is associated with high mortality, particularly in adults. Retrospective studies show that shorter times to treatment are correlated with a lower risk of death. A number of factors can be used to predict which patients would benefit from antifungal prophylaxis or early (pre-emptive or empirical) therapy. Detection of the fungal cell wall component (1?3)-?-D-glucan (BDG) shows promise as an early biomarker of invasive fungal infection and may be useful in identifying patients who would benefit from early antifungal treatment. To date, no consistent early treatment strategy has evolved. Proof-of-concept studies are needed to assess the role of pre-emptive and empirical therapy in ICU patients and the relevance of BDG as an early marker of infection.
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ICU-acquired immunosuppression and the risk for secondary fungal infections.
Med. Mycol.
PUBLISHED: 08-18-2010
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Sepsis and related infectious syndromes, including nosocomial infections, represent a major but largely under recognized healthcare problem worldwide, accounting for thousands of deaths every year. After a short pro-inflammatory phase, severely injured ICU patients enter a stage of protracted immunosuppression illustrated by reactivation of dormant viruses or infections due to microorganisms, including fungi, which are normally pathogenic solely in immunocompromised hosts. This brief review will focus on immune dysfunctions described so far in ICU patients regarding monocytes and T lymphocytes (as examples for innate and adaptive immune cells) and on their potential use as biomarkers for identification of patients at risk of secondary nosocomial infections and for guidance of immunotherapy. Finally, we will more specifically focus on the risk for fungal infections in ICU patients, and on the potential beneficial effects of adjunctive therapy not only to prevent these infections, but also to reinforce immune responses once they are already diagnosed.
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Pathogenesis of invasive candidiasis.
Curr Opin Crit Care
PUBLISHED: 08-17-2010
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Disseminated candidiasis remains a life-threatening disease in the ICU. The development of invasive disease with Candida albicans is dependent on multiple factors, such as colonization and efficient host defense at the mucosa. In the present review, we describe the host defense mechanisms against Candida that are responsible for counteracting mucosal invasion, and eliminating the pathogen once invasion has taken place.
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18F-FDG PET/CT for detection of metastatic infection in gram-positive bacteremia.
J. Nucl. Med.
PUBLISHED: 07-21-2010
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The timely detection of metastatic infectious foci in gram-positive bacteremia is crucial, because these foci often require prolonged antibiotic treatment or drainage. The diagnosis of metastatic infectious foci is difficult because localizing symptoms are often absent. We investigated whether (18)F-FDG PET/CT was able to detect such foci and whether detection influenced clinical outcome.
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Candida albicans dampens host defense by downregulating IL-17 production.
J. Immunol.
PUBLISHED: 07-12-2010
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IL-17 is one of the key cytokines that stimulate host defense during a Candida infection. Several studies have demonstrated the capacity of Candida albicans to induce a Th17 response. Surprisingly, experiments employing live C. ablicans demonstrated a specific downregulation of host IL-17 secretion in human blood mononuclear cells (PBMCs). By avoiding the direct contact of live C. albicans and PBMCs, we demonstrate that this inhibition effect is mediated by a soluble factor released by live C. albicans. However, this effect is due neither to the releasing of C. albicans pathogen-associated molecular patterns nor to the alteration of different Th cell subtypes. Rather, we found that live C. albicans shifts tryptophan metabolism by inhibiting IDO expression away from kynurenines and toward 5-hydroxytryptophan metabolites. In addition, we show that these latter 5-hydroxytryptophan metabolites inhibit IL-17 production. In conclusion, live C. albicans inhibits host Th17 responses by modulatory effects on tryptophan metabolism.
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Genetic variation of innate immune genes in HIV-infected african patients with or without oropharyngeal candidiasis.
J. Acquir. Immune Defic. Syndr.
PUBLISHED: 06-26-2010
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The occurrence of oropharyngeal candidiasis (OPC) in combination with HIV disease progression is a very common phenomenon. However, not all HIV-infected patients develop OPC, even when they progress to low CD4 T-cell counts. Because T-cell immunity is defective in AIDS, the innate defence mechanisms are likely to have a central role in antifungal immunity in these patients. We investigated whether genetic variations in the innate immune genes DECTIN-1, TLR2, TLR4, TIRAP, and CASPASE-12 are associated with the presence of OPC in HIV-infected subjects from East Africa.
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Novel strategies for the prevention and treatment of Candida infections: the potential of immunotherapy.
FEMS Microbiol. Rev.
PUBLISHED: 06-10-2010
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Infections caused by Candida spp. continue to be a substantial cause of disease burden, especially in immunocompromised patients. New approaches are needed to improve the outcome of patients suffering from Candida infections, because it seems unlikely that the established standard treatment will drastically lower the morbidity of mucocutaneous Candida infections and the high mortality associated with invasive candidiasis. New insights into the mechanisms of the anti-Candida host response have contributed to the design of novel immunotherapeutic approaches that have been proposed as adjuvant therapy in Candida infections. This review presents an overview of novel strategies in the prevention and treatment of Candida infections, with a special focus on adjuvant immunotherapy.
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Recognition of Borrelia burgdorferi by NOD2 is central for the induction of an inflammatory reaction.
J. Infect. Dis.
PUBLISHED: 05-06-2010
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Toll-like receptor 2 (TLR2) plays an important role in the recognition of Borrelia bacteria, the causative agent of Lyme disease, but the existence and importance of additional receptors in this process has been hypothesized. In the present study, we confirmed the role played by TLR2 in the recognition of Borrelia bacteria but also demonstrated a crucial role for the intracellular peptidoglycan receptor NOD2 for sensing the spirochete. Cells from individuals who were homozygous for the loss-of-function mutation 3020insC in the NOD2 gene were defective with respect to cytokine release after stimulation with Borrelia species, and this was confirmed in peritoneal macrophages from mice lacking RICK, the adaptor molecule used by NOD2. In contrast, NOD1 played no major role in the recognition of Borrelia spirochetes. This raises the intriguing possibility that recognition of Borrelia spirochetes is exerted by TLR2 in combination with NOD2 and that both receptors are necessary for an effective induction of cytokines by Borrelia species. The interplay between TLR2 and NOD2 might not only be necessary for the induction of a proper immune response but may also contribute to inflammatory-induced pathology.
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The inflammasome-mediated caspase-1 activation controls adipocyte differentiation and insulin sensitivity.
Cell Metab.
PUBLISHED: 04-19-2010
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Obesity-induced inflammation originating from expanding adipose tissue interferes with insulin sensitivity. Important metabolic effects have been recently attributed to IL-1? and IL-18, two members of the IL-1 family of cytokines. Processing of IL-1? and IL-18 requires cleavage by caspase-1, a cysteine protease regulated by a protein complex called the inflammasome. We demonstrate that the inflammasome/caspase-1 governs adipocyte differentiation and insulin sensitivity. Caspase-1 is upregulated during adipocyte differentiation and directs adipocytes toward a more insulin-resistant phenotype. Treatment of differentiating adipocytes with recombinant IL-1? and IL-18, or blocking their effects by inhibitors, reveals that the effects of caspase-1 on adipocyte differentiation are largely conveyed by IL-1?. Caspase-1 and IL-1? activity in adipose tissue is increased both in diet-induced and genetically induced obese animal models. Conversely, mice deficient in caspase-1 are more insulin sensitive as compared to wild-type animals. In addition, differentiation of preadipocytes isolated from caspase-1(-/-) or NLRP3(-/-) mice resulted in more metabolically active fat cells. In vivo, treatment of obese mice with a caspase-1 inhibitor significantly increases their insulin sensitivity. Indirect calorimetry analysis revealed higher fat oxidation rates in caspase-1(-/-) animals. In conclusion, the inflammasome is an important regulator of adipocyte function and insulin sensitivity, and caspase-1 inhibition may represent a novel therapeutic target in clinical conditions associated with obesity and insulin resistance.
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Influence of genetic variations in TLR4 and TIRAP/Mal on the course of sepsis and pneumonia and cytokine release: an observational study in three cohorts.
Crit Care
PUBLISHED: 04-07-2010
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It has been proposed that individual genetic variation contributes to the course of severe infections and sepsis. Recent studies of single nucleotide polymorphisms (SNPs) within the endotoxin receptor and its signaling system showed an association with the risk of disease development. This study aims to examine the response associated with genetic variations of TLR4, the receptor for bacterial LPS, and a central intracellular signal transducer (TIRAP/Mal) on cytokine release and for susceptibility and course of severe hospital acquired infections in distinct patient populations.
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Mycobacterium tuberculosis induces IL-17A responses through TLR4 and dectin-1 and is critically dependent on endogenous IL-1.
J. Leukoc. Biol.
PUBLISHED: 03-18-2010
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In the present study, we dissected the pathways that trigger the IL-17A responses by MTB. Dectin-1 and TLR4 were shown to be involved in MTB-induced IL-17A production, and blockade of the NOD2, TLR2, or MR had no effect on IL-17A. The MAPK Erk, known to mediate transcription of IL-1beta mRNA, was strongly involved in the IL-17A production induced by MTB. The intracellular enzymes caspase-1 and serine proteases, which process pro-IL-1beta into the active IL-1beta, were also crucial for the induction of IL-17A. Lastly, the MTB-induced IL-17A response was strongly dependent on signaling through the IL-1R but not the IL-6R pathway. In conclusion, the MTB-induced IL-17A response relies strongly on the endogenous IL-1 pathway and IL-1R signaling. TLR4 and dectin-1 are the main receptors responsible for mediating the signals responsible for IL-17A production by MTB. These findings contribute to a better understanding of the host response to mycobacteria and provide the opportunity to explore potential, novel, therapeutic strategies against TB.
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The role of nurses in the recognition and treatment of patients with sepsis in the emergency department: a prospective before-and-after intervention study.
Int J Nurs Stud
PUBLISHED: 03-16-2010
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In 2004, the Surviving Sepsis Campaign (SSC), a global initiative to reduce mortality from sepsis, was launched. Although the SSC supplies tools to measure and improve the quality of care for patients with sepsis, effective implementation remains troublesome and no recommendations concerning the role of nurses are given.
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IL-1beta processing in host defense: beyond the inflammasomes.
PLoS Pathog.
PUBLISHED: 02-26-2010
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Stimulation and release of proinflammatory cytokines is an essential step for the activation of an effective innate host defense, and subsequently for the modulation of adaptive immune responses. Interleukin-1beta (IL-1beta) and IL-18 are important proinflammatory cytokines that on the one hand activate monocytes, macropages, and neutrophils, and on the other hand induce Th1 and Th17 adaptive cellular responses. They are secreted as inactive precursors, and the processing of pro-IL-1beta and pro-IL-18 depends on cleavage by proteases. One of the most important of these enzymes is caspase-1, which in turn is activated by several protein platforms called the inflammasomes. Inflammasome activation differs in various cell types, and knock-out mice defective in either caspase-1 or inflammasome components have an increased susceptibility to several types of infections. However, in other infections and in models of sterile inflammation, caspase-1 seems to be less important, and alternative mechanisms such as neutrophil-derived serine proteases or proteases released from microbial pathogens can process and activate IL-1beta. In conclusion, IL-1beta/IL-18 processing during infection is a complex process in which the inflammasomes are only one of several activation mechanisms.
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Variable recognition of Candida albicans strains by TLR4 and lectin recognition receptors.
Med. Mycol.
PUBLISHED: 02-20-2010
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The role of TLR4 in the recognition of Candida albicans has been brought into question. In order to assess whether discrepancies in the literature are due to differences in the recognition of various C. albicans strains, we selected 14 different isolates of C. albicans to evaluate their recognition by TLR4 and lectin receptors. We demonstrate that recognition of cell wall structures by lectin receptors is a consistent characteristic independent of the C. albicans strain selected, while recognition by TLR4 is a more variable feature. These data were corroborated by the increased susceptibility of TLR4-/- mice to a C. albicans strain recognized by TLR4, but not to a strain in which recognition has been shown to be independent of this receptor. This suggests a heavier reliance of in vivo antifungal host defense on lectin receptors than on TLRs, a notion compatible with the clinical picture in individuals deficient in MyD88/TLRs or dectin-1/CARD9.
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Differential effects of IL-17 pathway in disseminated candidiasis and zymosan-induced multiple organ failure.
Shock
PUBLISHED: 02-18-2010
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The role of the IL-17 pathway in antifungal host defense is controversial. Several studies suggested that IL-17 is crucial for the protection against Candida infection, whereas other studies reported that IL-17 may contribute to inflammatory pathology and worsening of fungal disease. To address these discrepancies, we assessed the differential role of IL-17 pathway in two models of fungal sepsis: intravenous infection with live Candida albicans, in which fungal growth is the main cause of mortality, and zymosan-induced multiple organ failure, in which the inflammatory pathology drives the mortality. First, IL-17 receptor-deficient (IL-17RA) mice showed increased mortality and higher fungal loads in the kidneys in the model of disseminated candidiasis, partly caused by lower neutrophil recruitment in the IL-17RA mice. Second, IL-17RA mice were not protected against the multiorgan failure induced by zymosan. These data demonstrate that IL-17 does not have a major contribution to the inflammatory pathology leading to organ failure in fungal sepsis and support the concept that the IL-17 pathway is protective in antifungal host defense.
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A multifunctional mannosyltransferase family in Candida albicans determines cell wall mannan structure and host-fungus interactions.
J. Biol. Chem.
PUBLISHED: 02-17-2010
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The cell wall proteins of fungi are modified by N- and O-linked mannosylation and phosphomannosylation, resulting in changes to the physical and immunological properties of the cell. Glycosylation of cell wall proteins involves the activities of families of endoplasmic reticulum and Golgi-located glycosyl transferases whose activities are difficult to infer through bioinformatics. The Candida albicans MNT1/KRE2 mannosyl transferase family is represented by five members. We showed previously that Mnt1 and Mnt2 are involved in O-linked mannosylation and are required for virulence. Here, the role of C. albicans MNT3, MNT4, and MNT5 was determined by generating single and multiple MnTDelta null mutants and by functional complementation experiments in Saccharomyces cerevisiae. CaMnt3, CaMnt4, and CaMnt5 did not participate in O-linked mannosylation, but CaMnt3 and CaMnt5 had redundant activities in phosphomannosylation and were responsible for attachment of approximately half of the phosphomannan attached to N-linked mannans. CaMnt4 and CaMnt5 participated in N-mannan branching. Deletion of CaMNT3, CaMNT4, and CaMNT5 affected the growth rate and virulence of C. albicans, affected the recognition of the yeast by human monocytes and cytokine stimulation, and led to increased cell wall chitin content and exposure of beta-glucan at the cell wall surface. Therefore, the MNT1/KRE2 gene family participates in three types of protein mannosylation in C. albicans, and these modifications play vital roles in fungal cell wall structure and cell surface recognition by the innate immune system.
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Aspergillus fumigatus cell wall components differentially modulate host TLR2 and TLR4 responses.
Microbes Infect.
PUBLISHED: 02-13-2010
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Aspergillus fumigatus conidia attenuates host proinflammatory responses through modulation of Toll-like receptor (TLR)2 and TLR4 signaling, but the precise mechanisms that mediate this effect are not known. In the present study, the role of the Aspergillus cell wall polysaccharide constituents responsible for the modulation of host capability to mount a proinflammatory response was studied. Aspergillus cell wall fractions and its major components showed differential capabilities in modulating host TLR-mediated interleukin (IL)-6 production. Beta-glucan specifically suppressed TLR4-induced response, while alpha-glucan inhibited IL-6 induced through TLR2- and TLR4-stimulation. Galactomannan diminished TLR4-mediated response, while its inhibitory effects on TLR2-signaling were limited. Chitin, on the other hand, did not have significant immunomodulatory capability. The ability of the fungal cell wall to alter the immune signature of the pathogen may contribute to its virulence and the pathogenesis of co-infection.
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Activation of innate host defense mechanisms by Borrelia.
Eur. Cytokine Netw.
PUBLISHED: 02-12-2010
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Borrelia is the causative agent of Lyme disease, a widespread disease with important health consequences. Immune-mediated mechanisms are believed to play a major role in both host defense and in late complications of Lyme disease. Recognition of Borrelia and the initial activation of the innate immune system are important for host defense, as well as modulation of adaptive responses. Several classes of pattern recognition receptors (PRRs) have been suggested to be involved in the recognition of Borrelia: Toll-like receptors (TLRs), NOD-like receptors (NLRs) and C-type lectin receptors (CLRs). TLR2 has been found to be the most important receptor of the TLRs. The intracellular receptor NOD2, a member of the NLRs, might also play an important role in recognition. Mannose receptor is also involved in Borrelia recognition, but little is known about other CLRs such as dectin-1. After PRRs have recognized Borrelia, a signaling cascade is induced that leads to transcription of NF-kappaB, resulting in the production of pro-inflammatory cytokines. Understanding these pathways provides not only a better insight into the pathogenesis, but also provides potential, novel, therapeutic targets during active disease or post-infection complications.
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Borrelia species induce inflammasome activation and IL-17 production through a caspase-1-dependent mechanism.
Eur. J. Immunol.
PUBLISHED: 02-09-2010
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Borrelia burgdorferi spirochetes cause Lyme disease, which can result in severe clinical symptoms such as multiple joint inflammation and neurological disorders. IFN-? and IL-17 have been suggested to play an important role in the host defense against Borrelia, and in the immunopathology of Lyme disease. The caspase-1-dependent cytokine IL-1? has been linked to the generation of IL-17-producing T cells, whereas caspase-1-mediated IL-18 is crucial for IFN-? production. In this study, we show by using knockout mice the role of inflammasome-activated caspase-1 in the regulation of cytokine responses by B. burgdorferi. Caspase-1-deficient cells showed significantly less IFN-? and IL-17 production after Borrelia stimulation. A lack of IL-1? was responsible for the defective IL-17 production, whereas IL-18 was crucial for the IFN-? production. Caspase-1-dependent IL-33 played no role in the Borrelia-induced production of IL-1?, IFN-? or IL-17. In conclusion, we describe for the first time the role of the inflammasome-dependent caspase-1 activation of cytokines in the regulation of IL-17 production induced by Borrelia spp. As IL-17 has been implicated in the pathogenesis of chronic Lyme disease, these data suggest that caspase-1 targeting may represent a new immunomodulatory strategy for the treatment of complications of late stage Lyme disease.
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Reactive oxygen species-independent activation of the IL-1beta inflammasome in cells from patients with chronic granulomatous disease.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 01-26-2010
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Humans with chronic granulomatous diseases (CGDs) due to mutations in p47-phox have defective NADPH activity and thus cannot generate NADPH-dependent reactive oxygen species (ROS). The role of ROS in inflammation is controversial; some in vitro studies suggest that ROS are crucial for secretion of IL-1beta via inflammasome activation, whereas mice defective for ROS and patients with CGD have a proinflammatory phenotype. In this study, we evaluated activation of the IL-1beta inflammasome in cells from CGD patients. In contrast to previous studies using the small molecule diphenylene iodonium (DPI) as a ROS inhibitor, we found no decrease in either caspase-1 activation or secretion of IL-1beta and IL-18 in primary CGD monocytes. Moreover, activation of CGD monocytes by uric acid crystals induced a 4-fold higher level of IL-1beta secretion compared with that seen in monocytes from unaffected subjects, and this increase was not due to increased synthesis of the IL-1beta precursor. In addition, Western blot analysis of CGD cells revealed that caspase-1 activation was not decreased, but rather was increased compared with control cells. Examination of the effects exerted by the inhibition of ROS activity by DPI revealed that the decrease in IL-1beta secretion by DPI was actually due to inhibition of IL-1beta gene expression. Thus, inconsistent with the proinflammatory role of ROS, the present findings support the concept that ROS likely dampen inflammasome activation. The absence of ROS in CGD monocytes may explain the presence of an inflammatory phenotype characterized by granulomas and inflammatory bowel disease occurring in CGD patients.
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Treatment of knee prosthesis infections: evaluation of 15 patients over a 5-year period.
Int Orthop
PUBLISHED: 12-23-2009
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Our objective was to evaluate different treatment alternatives for total knee arthroplasty (TKA) infection and to compare outcomes depending on adherence to a current treatment algorithm. All patients treated for a first episode of TKA infection between January 2000 and July 2005 were included. Patient records were reviewed and data were extracted retrospectively. Fifteen patients were followed up for a median of 25 months. The cure rate in patients with two-stage exchange of knee prosthesis was higher than in patients who had débridement without implant removal (100 vs 37%, p = 0.03). Cure rates were not different between these two surgical approaches in ten patients who were treated according to a current treatment algorithm. Success rates for treatment of TKA infections varied considerably with the treatment strategy chosen. Our results support the use of existing algorithms to select patients who are eligible for débridement with retention of the prosthesis or need two-stage exchange of knee implants.
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Anti-Aspergillus human host defence relies on type 1 T helper (Th1), rather than type 17 T helper (Th17), cellular immunity.
Immunology
PUBLISHED: 12-02-2009
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Both interferon-gamma-producing type 1 T helper (Th1)- and interleukin-17 (IL-17)-producing Th17 cells have been proposed to be involved in anti-fungal host defence. Although invasive aspergillosis is one of the most severe human fungal infections, little is known regarding the relative importance of the Th1 versus Th17 cellular immune pathways for the human anti-Aspergillus host defence. Using human peripheral blood mononuclear cells and a system consisting of monocyte-derived macrophages with lymphocytes, we found that Aspergillus fumigatus is a weak inducer of human IL-17 but induces a strong Th1 response. These data were validated by the very low IL-17 levels in bronchoalveolar lavage fluid and serum of patients with invasive aspergillosis. Surprisingly, live A. fumigatus reduced IL-17 production induced by mitogenic stimuli. This effect was mediated through the propensity of A. fumigatus to metabolize tryptophan and release kynurenine, which modulates the inflammatory response through inhibition of IL-17 production. In conclusion, A. fumigatus does not stimulate production of IL-17 and human host defence against aspergillosis may not rely on potent Th17 responses.
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Human dectin-1 deficiency and mucocutaneous fungal infections.
N. Engl. J. Med.
PUBLISHED: 10-30-2009
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Mucocutaneous fungal infections are typically found in patients who have no known immune defects. We describe a family in which four women who were affected by either recurrent vulvovaginal candidiasis or onychomycosis had the early-stop-codon mutation Tyr238X in the beta-glucan receptor dectin-1. The mutated form of dectin-1 was poorly expressed, did not mediate beta-glucan binding, and led to defective production of cytokines (interleukin-17, tumor necrosis factor, and interleukin-6) after stimulation with beta-glucan or Candida albicans. In contrast, fungal phagocytosis and fungal killing were normal in the patients, explaining why dectin-1 deficiency was not associated with invasive fungal infections and highlighting the specific role of dectin-1 in human mucosal antifungal defense.
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Candida albicans releases soluble factors that potentiate cytokine production by human cells through a protease-activated receptor 1- and 2-independent pathway.
Infect. Immun.
PUBLISHED: 10-26-2009
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The innate immune system recognizes pathogen-associated molecular patterns (PAMPs) through pattern recognition receptors (PRR) and transduces downstream signaling to activate the host defense. Here we report that in addition to direct PAMP-PRR interactions, live Candida albicans cells can release soluble factors to actively potentiate interleukin-6 (IL-6) and IL-8 production induced in human mononuclear cells by the fungi. Although protease-activated receptor 1 (PAR1) and PAR2 ligation can moderately upregulate Toll-like receptor 4 (TLR4)-mediated IL-8 production, no effect on the C. albicans-induced cytokine was apparent. Similarly, the blockade of PAR signaling did not reverse the potentiation of cytokine production induced by soluble factors released by C. albicans. In conclusion, C. albicans releases soluble factors that potentiate cytokine release in a PAR1/2-independent manner. Thus, human PAR1 and PAR2 have a redundant role in the activation of human cells by C. albicans.
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Receptor recognition of and immune intracellular pathways for Veillonella parvula lipopolysaccharide.
Clin. Vaccine Immunol.
PUBLISHED: 10-14-2009
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Veillonella parvula is an anaerobic gram-negative coccus that is part of the normal flora of the animal and human mouth and gastrointestinal and genitourinary tracts. Oral V. parvula is involved in the development of early periodontal disease as well as different types of serious infections. Present data on molecular mechanisms responsible for innate immune response against Veillonella are very scanty. The aim of this study was to investigate the Toll-like receptor (TLR) pathways responsible for V. parvula lipopolysaccharide (LPS) and to identify the intracellular pathways induced by this recognition. V. parvula LPS stimulated tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) release in human peripheral blood mononuclear cells (PBMC) in a dose-dependent manner. Pretreatment of cells with a TLR4 antagonist significantly reduced TNF-alpha and IL-6 production in PBMC stimulated with either Veillonella or Escherichia coli LPS. However, V. parvula LPS was 10- to 100-fold less active than E. coli LPS for cytokine induction. TNF-alpha, IL-1beta, IL-6, and IL-10 were released in wild-type and TLR2(-/-), but not TLR4(-/-), mouse macrophage cultures. V. parvula LPS was able to activate the human PBMC p38 mitogen-activated protein kinase (MAPK). A specific p38 MAPK inhibitor strongly inhibited V. parvula LPS-induced TNF-alpha, IL-1beta, IL-6, and IL-10. In conclusion, V. parvula LPS is able to induce cytokine production in both human and murine in vitro models, although it is less effective than Enterobacteriaceae LPS. V. parvula LPS-stimulated cytokine induction, as well as p38 MAPK activation, are TLR4-dependent features.
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JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.