[Show abstract][Hide abstract] ABSTRACT: Inflammation is mediated mainly by leukocytes which express both toll-like receptor 4 (TLR4) and Fc gamma receptors (FcγR). Dysregulated activation of leukocytes via exogenous and endogenous ligands of TLR4 results in a large number of inflammatory disorders that underlie a variety of human diseases. Thus, differentially blocking inflammatory cells while sparing structural cells, which are FcγR negative, represents an elegant strategy when targeting the underlying causes of human diseases. Here, we report a novel tethering mechanism of the Fv and Fc portions of anti-TLR4 blocking antibodies that achieves increased potency on inflammatory cells. In the presence of ligand, e.g., lipopolysaccharide (LPS), TLR4 trafficks into glycolipoprotein microdomains, forming concentrated protein platforms that include FcγRs. This clustering produces a microenvironment allowing anti-TLR4 antibodies to co-engage TLR4 and FcγRs, increasing their avidity and thus substantially increasing their inhibitory potency. Tethering of antibodies to both TLR4 and FcγRs proves valuable at ameliorating inflammation in vivo. This novel mechanism of action therefore has the potential to enable selective intervention of relevant cell types in TLR4-driven diseases.
Journal of Biological Chemistry 04/2014; · 4.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The spread of microorganisms in hospitals is an important public health threat, and yet few studies have assessed how human microbial communities (microbiota) evolve in the hospital setting. Studies conducted so far have mainly focused on a limited number of bacterial species, mostly pathogenic ones and primarily during outbreaks. We explored the bacterial community diversity of the microbiota from oral and respiratory samples of intubated patients hospitalized in the intensive care unit and we discuss the technical challenges that may arise while using culture-independent approaches to study these types of samples.
Frontiers in Cellular and Infection Microbiology 01/2014; 4:65. · 2.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Fibroblast growth factor 21 (FGF21) is a key regulator in glucose and lipid metabolism and its plasma levels have been showed to be increased in humans in different situations such as type 2 diabetes, obesity and nonalcoholic fatty liver disease but also in animal models of sepsis and pancreatitis. FGF21 is considered as a pharmacological candidate in conditions associated with insulin resistance. The aim of this study was to compare FGF21 plasma levels in patients with sepsis, in patients with a systemic inflammatory response syndrome (SIRS), and in healthy controls. We measured FGF21 plasma concentrations in 22 patients with established sepsis, in 11 with SIRS, and in 12 healthy volunteers. Here, we show that FGF21 levels were significantly higher in plasma from patients with sepsis and SIRS in comparison to healthy controls. Also, FGF21 levels were significantly higher in patients with sepsis than in those with noninfectious SIRS. FGF21 plasma levels measured at study entry correlated positively with the APACHE II score, but not with procalcitonin levels, nor with C-reactive protein, classical markers of sepsis. Plasma concentrations of FGF21 peaked near the onset of shock and rapidly decreased with clinical improvement. Taken together, these results indicate that circulating levels of FGF21 are increased in patients presenting sepsis and SIRS and suggest a role of FGF21 in inflammation. Further studies are needed to explore the potential role of FGF21 in sepsis as a potential therapeutic target.
[Show abstract][Hide abstract] ABSTRACT: In the context of worldwide increasing antimicrobial resistance, good antimicrobial prescribing in more needed than ever; unfortunately, information available to clinicians often are insufficient to rely on. Biomarkers might provide help for decision-making and improve antibiotic management. The purpose of this expert panel review was to examine currently available literature on the potential role of biomarkers to improve antimicrobial prescribing, by answering three questions: 1) Which are the biomarkers available for this purpose?; 2) What is their potential role in the initiation of antibiotic therapy?; and 3) What is their role in the decision to stop antibiotic therapy? To answer these questions, studies reviewed were limited to recent clinical studies (<15 years), involving a substantial number of patients (>50) and restricted to controlled trials and meta-analyses for answering questions 2 and 3. With regard to the first question concerning routinely available biomarkers, which might be useful for antibiotic management of acute infections, these are currently limited to C-reactive protein (CRP) and procalcitonin (PCT). Other promising biomarkers that may prove useful in the near future but need to undergo more extensive clinical testing include sTREM-1, SuPAr, ProADM, and presepsine. New approaches to biomarkers of infections include point-of-care testing and genomics.
[Show abstract][Hide abstract] ABSTRACT: Biomarker-guided initiation of antibiotic therapy has been studied in four conditions: acute pancreatitis, lower respiratory tract infection (LRTI), meningitis, and sepsis in the ICU. In pancreatitis with suspected infected necrosis, initiating antibiotics best relies on fine-needle aspiration and demonstration of infected material. We suggest that PCT be measured to help predict infection; however, available data are insufficient to decide on initiating antibiotics based on PCT levels. In adult patients suspected of community-acquired LRTI, we suggest withholding antibiotic therapy when the serum PCT level is low (<0.25 ng/mL); in patients having nosocomial LRTI, data are insufficient to recommend initiating therapy based on a single PCT level or even repeated measurements. For children with suspected bacterial meningitis, we recommend using a decision rule as an aid to therapeutic decisions, such as the Bacterial Meningitis Score or the Meningitest(R); a single PCT level >=0.5 ng/mL also may be used, but false-negatives may occur. In adults with suspected bacterial meningitis, we suggest integrating serum PCT measurements in a clinical decision rule to help distinguish between viral and bacterial meningitis, using a 0.5 ng/mL threshold. For ICU patients suspected of community-acquired infection, we do not recommend using a threshold serum PCT value to help the decision to initiate antibiotic therapy; data are insufficient to recommend using PCT serum kinetics for the decision to initiate antibiotic therapy in patients suspected of ICU-acquired infection. In children, CRP can probably be used to help discontinue therapy, although the evidence is limited. In adults, antibiotic discontinuation can be based on an algorithm using repeated PCT measurements. In non-immunocompromised out- or in- patients treated for RTI, antibiotics can be discontinued if the PCT level at day 3 is < 0.25 ng/mL or has decreased by >80-90%, whether or not microbiological documentation has been obtained. For ICU patients who have nonbacteremic sepsis from a known site of infection, antibiotics can be stopped if the PCT level at day 3 is < 0.5 ng/mL or has decreased by >80% relative to the highest level recorded, irrespective of the severity of the infectious episode; in bacteremic patients, a minimal duration of therapy of 5 days is recommended.
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVE:: A hallmark of sepsis and severe systemic inflammatory response syndrome (SIRS) is the massive recruitment of immature neutrophils from the bone marrow into the circulation (left shift, band forms). Their capacity to participate in innate defense against bacteria is ill defined. We aimed at comparing various innate immune functions of mature vs. immature neutrophils circulating during sepsis and SIRS. DESIGN:: Prospective, observational cohort study. SETTING:: Tertiary level ICU and associated research laboratory. PATIENTS:: Thirty-three ICU patients with sepsis; 12 ICUs with SIRS; 32 healthy volunteers. INTERVENTIONS:: Twenty milliliters of whole heparinized blood was used for in vitro studies including neutrophil viability and apoptosis, surface expression of CD16, Toll-like receptors (1) 4 and TLR2, CD14, MD-2, HLA-DP,-DQ and -DR, and CXCR2, chemotaxis, phagocytosis, bacterial killing, and tumor necrosis factor (TNF)-α/interleukin (IL)-10 baseline intracellular cytokine levels. MEASUREMENTS AND MAIN RESULTS:: Immature neutrophils were capable of mediating important innate immune functions such as bacterial phagocytosis and killing via the production of reactive oxygen species, although less efficiently than mature neutrophils. Immature neutrophils had a longer life span and resistance to spontaneous apoptosis, and could mature ex vivo. They expressed lower levels of receptors for bacterial molecules such as CD14 and MD-2 and migrated less efficiently than mature granulocytes. Immature neutrophils had higher basal intracellular TNF-α/IL-10 ratio than that of mature neutrophils, suggesting a proinflammatory phenotype. No significant differences were observed between immature neutrophils isolated from patients with sepsis and those from patients with severe SIRS. CONCLUSIONS:: Despite their "immaturity", band forms are capable of mediating crucial innate immune functions during severe infections and sepsis. Their fate and capacity to mature in vivo remain to be determined.
Critical care medicine 01/2013; · 6.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Experimentally, erythropoietin (EPO) has nephroprotective as well as immunomodulatory properties when administered after ischemic renal injury. We tested the hypothesis that different doses of recombinant human EPO administered to patients after cardiac surgery would minimize kidney lesions and the systemic inflammatory response, thereby decreasing acute kidney injury (AKI) incidence. METHODS: In this double-blinded randomized control study, 80 patients admitted to the ICU post-cardiac surgery were randomized by computer to receive intravenously isotonic saline (n = 40) versus alpha-Epoetin (n = 40): either 40000 IU (n = 20) or 20000 IU (n = 20). The study lasted one year. The primary outcome was the change in urinary NGAL concentration from baseline and 48 h after EPO injection. Creatinine, cystatine C and urinary NGAL levels were measured on the day of randomization and 2--4 days after EPO injection. To assess acute inflammatory response, serum cytokines (IL6 and IL8) were measured at randomization and four days after r-HuEPO injection. Patients and care-takers were blinded for the assignment. RESULTS: No patient was excluded after randomization. Patient groups did not differ in terms of age, gender, comorbidities and renal function at randomization. The rate of AKI assessed by AKIN criteria was 22.5% in our population. EPO treatment did not significantly modify the difference in uNGAl between 48 hours and randomization compared to placebo [2.5 ng/ml (-17.3; 22.5) vs 0.7 ng/ml (-31.77; 25.15), p = 0.77] and the incidence of AKI was similar. Inflammatory cytokines levels were not influenced by EPO treatment. Mortality and hospital stays were similar between the groups and no adverse event was recorded. CONCLUSION: In this randomized-controlled trial, alpha-Epoetin administrated after cardiac surgery, although safe, demonstrated neither nephroprotective nor anti-inflammatory properties.Trial registration numberNCT00676234.
[Show abstract][Hide abstract] ABSTRACT: Systemic inflammation is very prevalent among critically ill patients, particularly those with extensive tissue injury. Although downstream mediators (cytokines) and effector cells (phagocytes) have been identified, proximal mediators originating from injured tissues remained elusive. Alarmins ("danger signals") released by necrotic/injured cells have been identified recently and certainly play a role in triggering local and systemic inflammation in critically ill patients. The most promising alarmin candidates are of mitochondrial origin, i.e. mitochondrial DNA and the chemotactic factor fMet-Leu-Phe (fMLP). ATP also is released from necrotic tissues and stimulates the assembly of the inflammasome, leading to the production of proinflammatory cytokines, such as interleukin (IL)-1SZ. The identification of novel alarmins opens new therapeutic avenues for the treatment of severe SIRS, and SIRS-dependent organ dysfunction.
[Show abstract][Hide abstract] ABSTRACT: Recognition of microbial molecules by mammalian host receptors is essential to mount an immune response. Hexaacylated LPS is the prototypic example of a bacterial molecule recognized by the receptor complex TLR4/MD-2 with its lipid A moiety, whereas bacterial lipopeptides are recognized by TLR2. Here we show that a series of synthetic triacylated lipid A-like molecules are weak Toll-like receptor (TLR) agonists (mainly TLR2 agonists) but very potent TLR4/MD-2 antagonists (submicromolar range). Not only do they block human cell responses to LPS but also to whole gram-negative bacteria, and they inhibit the phagocytosis of gram-negative bacteria. These compounds may represent promising immunomodulatory agents.
Journal of Biological Chemistry 03/2012; 287(20):16121-31. · 4.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bacterial sepsis is a major threat in neonates born prematurely, and is associated with elevated morbidity and mortality. Little is known on the innate immune response to bacteria among extremely premature infants.
We compared innate immune functions to bacteria commonly causing sepsis in 21 infants of less than 28 wks of gestational age, 24 infants born between 28 and 32 wks of gestational age, 25 term newborns and 20 healthy adults. Levels of surface expression of innate immune receptors (CD14, TLR2, TLR4, and MD-2) for Gram-positive and Gram-negative bacteria were measured in cord blood leukocytes at the time of birth. The cytokine response to bacteria of those leukocytes as well as plasma-dependent opsonophagocytosis of bacteria by target leukocytes was also measured in the presence or absence of interferon-γ. Leukocytes from extremely premature infants expressed very low levels of receptors important for bacterial recognition. Leukocyte inflammatory responses to bacteria and opsonophagocytic activity of plasma from premature infants were also severely impaired compared to term newborns or adults. These innate immune defects could be corrected when blood from premature infants was incubated ex vivo 12 hrs with interferon-γ.
Premature infants display markedly impaired innate immune functions, which likely account for their propensity to develop bacterial sepsis during the neonatal period. The fetal innate immune response progressively matures in the last three months in utero. Ex vivo treatment of leukocytes from premature neonates with interferon-γ reversed their innate immune responses deficiency to bacteria. These data represent a promising proof-of-concept to treat premature newborns at the time of delivery with pharmacological agents aimed at maturing innate immune responses in order to prevent neonatal sepsis.
PLoS ONE 01/2012; 7(3):e32863. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mechanical ventilation (MV) could prime the lung toward an inflammatory response if exposed to another insult such as bacterial invasion. The underlying mechanisms are not so far clear. Toll-like receptors (TLRs) allow the host to recognize selectively bacterial pathogens and in turn to trigger an immune response. We therefore hypothesized that MV modulates TLR2 expression and in turn modifies responsiveness to agonists such as bacterial lipopeptide (BLP).
Both in vitro and in vivo experiments were conducted. First, TLR2 expression and protein were measured in the A549 pulmonary epithelial cell line submitted to 8-hour cyclic stretch (20% elongation; 20/minute rate). After a 24-hour period of cyclic stretch, the inflammatory response of the A549 cells to the synthetic BLP, Pam3CSK4, was tested after 8 hours of exposure. In a second set of experiments, healthy anesthetized and paralyzed rabbits were submitted to 8-hour MV (tidal volume = 12 ml/kg, zero end-expiratory pressure; FIO2 = 50%; respiratory rate = 20/minute) before being sacrificed for TLR2 lung expression assessment. The lung inflammatory response to BLP was then tested in animals submitted to 24-hour MV before being sacrificed 8 hours after the tracheal instillation of Pam3CSK4.
Cyclic stretch of human pulmonary epithelial cell lines increased both TLR2 mRNA and protein expression. Cells submitted to cyclic stretch also increased IL-6 and IL-8 secretion in response to Pam3CSK4, a classical TLR2 ligand. A mild-stretch MV protocol induced a 60-fold increase of TLR2 mRNA expression in lung tissue when compared with spontaneously breathing controls. Moreover, the combination of MV and airway exposure to Pam3CSK4 acted synergistically in causing lung inflammation and injury.
Mild-stretch MV increases lung expression of TLR2 and sensitizes the lung to bacterial TLR2 ligands. This may account for the propensity of mechanically ventilated patients to develop acute lung injury in the context of airway bacterial colonization/infection.
Critical care (London, England) 07/2011; 15(4):R181. · 4.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background. Leptospirosis is a spirochetal zoonosis with complex clinical features including renal and liver failure. Case report. We report the case of a Swiss fisherman presenting with leptospirosis. After initial improvement, refractory septic shock and severe liver and kidney failure developed. The expected mortality was estimated at 90% with clinical scores. The patient underwent plasma exchanges and high-volume hemofiltration (HVHF) with complete recovery of hepatic and kidney functions. Discussion. Plasma exchanges and HVHF may confer survival benefit on patients with severe leptospirosis, refractory septic shock, and multiple-organ failure.