Soluble triggering receptor expressed on myeloid cells 1 as an anti-inflammatory mediator in sepsis

The Prognostic Value of Serum Soluble TREM-1 on Outcome in Adult Patients with Sepsis

Increased soluble triggering receptor expressed on myeloid cells 1 (sTREM-1) levels have been reported in patients with sepsis. We tested the hypotheses that serum sTREM-1 levels increase in the early phase of sepsis and decrease after sepsis under appropriate treatment and that sTREM-1 levels can predict therapeutic outcomes. One hundred and fifty-five patients prospectively underwent blood samples including biochemical data, sTREM-1, and biomarkers on endothelial dysfunction as well as clinical severity index examinations. Blood samples from Days 1, 4, and 7 after admission were checked. For comparison, 50 healthy subjects were selected as healthy control. Those patients who had sepsis had significantly higher sTREM-1 levels than those of healthy control. sTREM-1 levels positively correlated with biomarkers for endothelial dysfunction (ICAM-1, VCAM-1, and E-selectin) and lactate level as well as clinical severity index (maximum 24 h APACHE score and Sequential Organ Failure Assessment (SOFA) score) upon admission. sTREM-1 concentrations were significantly higher from Day 1 to Day 7 in the non-survivors than in the survivors. A stepwise logistic regression analysis showed only sTREM-1 level and maximum 24 h SOFA score upon admission were significantly associated with fatality. Area under the receiver operating characteristic curve analysis for the diagnostic accuracy of sTREM-1 in sepsis-related fatality gave a value of 0.726, with a cutoff value of 384.6 pg/mL (sensitivity = 80.8% and specificity = 61.5%). sTREM-1 level may be valuable in auxiliary diagnosis, and it can serve as a useful biomarker as a screening service and follow-up therapeutic outcomes in sepsis.

Soluble Triggering Receptors Expressed on Myeloid Cells-1 as a Neonatal Ventilator-Associated Pneumonia Biomarker

Background

Neonatal ventilator-associated pneumonia (NVAP) is one of the main infections acquired in hospitals, and soluble triggering receptors expressed on myeloid cells-1 (sTREM-1) are a TREM-1 subtype that can be released into the blood or bodily fluids during an infection.

Methods

The patients included in the present study were divided into three groups: the NVAP group, the first control group, and the second control group (n = 20, each). Children requiring respiratory treatment were assigned to the NVAP group, newborns who received mechanical ventilation and had neonatal respiratory distress syndrome were assigned to the first control group, and newborns with normal X-ray and electrocardiogram results but no non-pulmonary infection was assigned to the second control group. The blood and bronchoalveolar lavage fluid (BALF) sTREM-1 levels in all newborns were analyzed.

Results

The acute-phase blood and BALF sTREM-1 levels were significantly higher in the NVAP group than in the first control group, and the blood sTREM-1 expression level was lower in the second control group than in the NVAP group.

Conclusion

The present results suggest that sTREM-1 might be a useful biomarker for NVAP prediction in the Department of Pediatrics.

Biomarker-Guided Individualization of Antibiotic Therapy

Treatment failure of antibiotic therapy due to insufficient efficacy or occurrence of toxicity is a major clinical challenge, and is expected to become even more urgent with the global rise of antibiotic resistance. Strategies to optimize treatment in individual patients are therefore of crucial importance. Currently, therapeutic drug monitoring plays an important role in optimizing antibiotic exposure to reduce treatment failure and toxicity. Biomarker-based strategies may be a powerful tool to further quantify and monitor antibiotic treatment response, and reduce variation in treatment response between patients. Host response biomarkers, such as CRP, procalcitonin, IL-6, and presepsin, could potentially carry significant information to be utilized for treatment individualization. To achieve this, the complex interactions among immune system, pathogen, drug, and biomarker need to be better understood and characterized. The purpose of this tutorial is to discuss the use and evidence of currently available biomarker-based approaches to inform antibiotic treatment. To this end, we also included a discussion on how treatment response biomarker data from preclinical, healthy volunteer, and patient-based studies can be further characterized using pharmacometric and system pharmacology based modeling approaches. As an illustrative example of how such modeling strategies can be used, we describe a case study in which we quantitatively characterize procalcitonin dynamics in relation to antibiotic treatments in patients with sepsis.

TREM-1 isoforms in bacterial infections: to immune modulation and beyond

The triggering receptor expressed on myeloid cells 1 (TREM-1) is an innate immunity receptor associated with the amplification of inflammation in sterile and non-sterile inflammatory disorders. Since its first description, the two isoforms of the receptor, membrane and soluble (mTREM-1 and sTREM-1, respectively) have been largely explored in the immunopathogenesis of several bacterial diseases and sepsis. The role of the receptor in these scenarios seems to be at least partly dependent on the source/type of bacteria, host and context. As uncontrolled inflammation is a result of several bacterial infections, the inhibition of the receptor has been considered as a promising approach to treat such conditions. Further, sTREM-1 has been explored as a biomarker for diagnosis and/or prognosis of several bacterial diseases. Therefore, this review aims to provide an updated insight into how the receptor influences and is influenced by bacterial infections, highlighting the advances regarding the use/manipulation of TREM-1 isoforms in biomedical research and clinical practice.

Quercetin Alleviates LPS-Induced Depression-Like Behavior in Rats via Regulating BDNF-Related Imbalance of Copine 6 and TREM1/2 in the Hippocampus and PFC

Quercetin is a polyphenol with multiple biological activities, and results of our preliminary study showed that it could shorten the immobility time of mice in the forced swimming test and tail suspending test. The aim of this study was to investigate its effects on the behavioral performance of lipopolysaccharide (LPS)-challenged rats and explore the potential mechanism. The results showed that intragastrical administration of quercetin (40 mg/kg) could improve the bodyweight gain of LPS-challenged rats, increase the saccharin preference index in the saccharin preference test and the novel arm preference index in the Y-maze, and decrease the immobility time in the FST. However, it showed no significant effect on the performance of LPS-challenged rats in the Morris water maze and the plasma concentrations of nesfatin-1, C-reactive protein (CRP), and IL-6. Results of western blot showed that the expression levels of BDNF, Copine 6, p-TrkB, and the triggering receptors expressed on myeloid cells (TREM) 1 were decreased in both the hippocampus and the prefrontal cortex (PFC) of LPS-challenged rats, while the expression of TREM2 was increased. The protein expression of synapsin-1 was decreased in the hippocampus without significant changes in the PFC. These imbalance protein expressions could be balanced by treatment with quercetin. The results suggested that quercetin could alleviate LPS-induced depression-like behaviors and impairment of learning and memory in rats, the mechanism of which might be involved with regulating the BDNF-related imbalance expression of Copine 6 and TREM1/2 in the hippocampus and the PFC.

Prediction of mortality in adult patients with sepsis using six biomarkers: a systematic review and meta-analysis

Background

Angiopoietin-1 (Ang-1) and 2 (Ang-2), high mobility group box 1 (HMGB1), soluble receptor for advanced glycation endproducts (sRAGE), soluble triggering receptor expressed on myeloid cells 1 (sTREM1), and soluble urokinase-type plasminogen activator receptor (suPAR) have shown promising results for predicting all-cause mortality in critical care patients. The aim of our systematic review and meta-analysis was to assess the prognostic value of these biomarkers for mortality in adult patients with sepsis.

Methods

A systematic literature search of the MEDLINE, PubMed, EMBASE, and Cochrane Library databases, for articles in English published from 01.01.1990 onwards, was conducted. The systematic review focused exclusively on observational studies of adult patients with sepsis, any randomized trials were excluded. For the meta-analysis, only studies which provide biomarker concentrations within 24 h of admission in sepsis survivors and nonsurvivors were included. Results are presented as pooled mean differences (MD) between nonsurvivors and survivors with 95% confidence interval for each of the six biomarkers. Studies not included in the quantitative analysis were narratively summarized. The risk of bias was assessed in all included studies using the Quality in Prognosis Studies (QUIPS) tool.

Results

The systematic literature search retrieved 2285 articles. In total, we included 44 studies in the qualitative analysis, of which 28 were included in the meta-analysis. The pooled mean differences in biomarker concentration (nonsurvivors − survivors), measured at onset of sepsis, are listed as follows: (1) Ang-1: − 2.9 ng/ml (95% CI − 4.1 to − 1.7, p < 0.01); (2) Ang-2: 4.9 ng/ml (95% CI 2.6 to 7.1, p < 0.01); (3) HMGB1: 1.2 ng/ml (95% CI 0.0 to 2.4, p = 0.05); (4) sRAGE: 1003 pg/ml (95% CI 628 to 1377, p < 0.01); (5) sTREM-1: 87 pg/ml (95% CI 2 to 171, p = 0.04); (6) suPAR: 5.2 ng/ml (95% CI 4.5 to 6.0, p < 0.01).

Conclusions

Ang-1, Ang-2, and suPAR provide beneficial prognostic information about mortality in adult patients with sepsis. The further development of standardized assays and the assessment of their performance when included in panels with other biomarkers may be recommended.

Trial registration This study was recorded on PROSPERO, prospective register of systematic reviews, under the registration ID: CRD42018081226

The diagnostic roles of neutrophil in bloodstream infections

Bloodstream infections remain a leading cause of death worldwide, despite advances in critical care and understanding of the pathophysiology and treatment strategies. No specific biomarkers or therapy are available for these conditions. Neutrophils play a critical role in controlling infection and it is suggested that their migration and antimicrobial activity are impaired during sepsis which contribute to the dysregulation of immune responses. Recent studies further demonstrated that interruption or reversal of the impaired migration and antimicrobial function of neutrophils improves the outcome of sepsis in animal models. In this review, we provide an overview of the associated diagnostic biomarkers involved neutrophils in sepsis, and discuss the potential of neutrophils as a target to specifically predict the outcome of sepsis.

Diagnostic effectiveness of soluble triggering receptor expressed on myeloid cells-1 in sepsis, severe sepsis and septic shock

INTRODUCTION

Sensitivities and specificities of clinical signs and biochemical tests in sepsis diagnosis are not satisfactory. The aim of the study was to assess the diagnostic usefulness of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) in sepsis, severe sepsis and septic shock against interleukin-6 (IL-6), C-reactive protein (CRP) and procalcitonin (PCT).

MATERIAL AND METHODS

A prospective, observational study was conducted in 85 adults with sepsis, severe sepsis or septic shock and 22 with non-infective systemic inflammatory response syndrome (NI-SIRS). Serum levels of sTREM-1, CRP, PCT and IL-6 were measured on admission.

RESULTS

Median serum sTREM-1 concentrations were higher in severe sepsis (540 pg/ml) and septic shock (536 pg/ml) in comparison with NI-SIRS patients (p < 0.05). There were no differences in sTREM-1 levels between NI-SIRS and sepsis. Similarly, CRP, PCT and IL-6 were significantly elevated in patients with severe sepsis and septic shock in comparison with NI-SIRS. The receiver operating characteristic curve analysis for diagnosis of severe sepsis showed higher discriminative value for CRP and IL-6 (AUC = 0.909, 95% CI: 0.829-0.99 and AUC = 0.854, 95% CI: 0.728-0.980, respectively) than sTREM-1 (AUC = 0.733, 95% CI: 0.596-0.870). In septic shock the highest AUC was found for CRP (AUC = 0.938, 95% CI: 0.872-1.0), lower for IL-6 (AUC = 0.869, 95% CI: 0.751-0.987), PCT (AUC = 0.828, 95% CI: 0.71-0.945) and sTREM-1 (AUC = 0.705, 95% CI: 0.553-0.856).

CONCLUSIONS

Serum level of sTREM-1 has lower effectiveness as a diagnostic biomarker in severe sepsis and septic shock, in comparison with CRP and IL-6.

An immunohistochemical study of the diagnostic value of TREM-1 as marker for fatal sepsis cases

Triggering receptor expressed on myeloid cells-1 (TREM-1) is produced and up-regulated by exposure of myeloid cells to lipopolysaccharides or other components of either bacterial or fungal origin, which causes it to be strongly expressed on phagocytes that accumulate in inflamed areas. Because TREM-1 participates in septic shock and in amplifying the inflammatory response to bacterial and fungal infections, we believe it could be an immunohistochemical marker for postmortem diagnosis of sepsis. We tested the anti-TREM-1 antibody in 28 cases of death by septic shock and divided them into two groups. The diagnosis was made according to the criteria of the Surviving Sepsis Campaign. In all cases, blood cultures were positive. The first group was comprised subjects that presented high ante-mortem serum procalcitonin and the soluble form of TREM-1 (s-TREM-1) values. The second group comprised subjects in which s-TREM-1 was not measured ante-mortem. We used samples of brain, heart, lung, liver and kidney for each case to test the anti-TREM-1 antibody. A semiquantitative evaluation of the immunohistochemical findings was made. In lung samples, we found immunostaining in the cells of the monocyte line in 24 of 28 cases, which suggests that TREM-1 is produced principally by cells of the monocyte line. In liver tissue, we found low TREM-staining in the hepatocyte cytoplasm, duct epithelium, the portal-biliary space and blood vessel. In kidney tissue samples, we found the TREM-1 antibody immunostaining in glomeruli and renal tubules. We also found TREM-1 staining in the lumen of blood vessels. Immunohistochemical staining using the anti-TREM-1 antibody can be useful for postmortem diagnosis of sepsis.

A first-in-man safety and pharmacokinetics study of nangibotide, a new modulator of innate immune response through TREM-1 receptor inhibition

AIMS

The peptide nangibotide is the first clinical-stage agent targeting the immunoreceptor TREM-1 (triggering receptor expressed on myeloid cells-1) and is being investigated as a novel therapy for acute inflammatory disorders such as septic shock. This first-in-man, randomized, double-blind, ascending dose, placebo-controlled Phase I study evaluated the safety, tolerability and pharmacokinetics of nangibotide.

METHODS

Twenty-seven healthy subjects (aged 18-45 years) were randomized into eight groups. Nangibotide was administered as a single continuous intravenous infusion. The first two groups received a single i.v. dose of 1 and 10 mg, respectively, over 15 min. Subsequent groups were randomized in a product : placebo ratio of 3:1 at doses ranging from 0.03 to 6 mg kg^-1  h^-1 over 7 h 45 min, preceded by a 15-minute loading dose of up to 5 mg kg^-1 .

RESULTS

Nangibotide was safe and well tolerated up to the highest dose tested. There were only few adverse events and they were mild in severity and considered unrelated to treatment. Nangibotide displayed dose-proportional PK properties, with a clearance of 6.6 l kg^-1  h^-1 for a subject of 70 kg and a 3 min effective half-life, which are compatible with extensive enzymatic metabolism in blood. Central and peripheral volumes of distribution were 16.7 l and 15.9 l respectively, indicating limited distribution of the drug mainly in blood and interstitial fluid. No circulating anti-drug antibodies were detectable up to 28 days after administration.

CONCLUSIONS

The novel immunomodulator nangibotide displayed favourable safety and PK profiles at all doses, including expected pharmacologically active doses, and warrants further clinical development.

Expression level of 12-amino acid triggering receptor on myeloid cells-like transcript 1 derived peptide alleviates lipopolysaccharide-induced acute lung injury in mice

Acute lung injury (ALI) is a critical illness with a high morbidity and mortality rate due to severe inflammation in the lungs. The effects and underlying mechanism of the triggering receptor expressed on myeloid cells‑1 (TREM‑1)‑like transcript‑1‑derived peptide (LR12) on ALI remain unclear. The aim of the present study was to determine whether LR12 attenuates lipopolysaccharide (LPS)‑induced ALI and elucidate the mechanism underlying it. Male C57BL/6 mice were randomly assigned to three groups as follows: Sham group, LPS + scramble group and LPS + LR12 group. Normal saline (NS) or LPS was administrated by intratracheal instillation, and NS, LR12 or LR12 scramble was administered intraperitoneally 30 min later. The treatment was repeated every 3 h three times. Mice were sacrificed 24 h later. Pulmonary pathological changes, the lung wet/dry weight ratio, the macrophage and neutrophil counts in bronchoalveolar lavage fluid and myeloperoxidase (MPO) activity in the lung tissues were observed. The inflammatory cytokines were evaluated by enzyme‑linked immunosorbent assay and lung neutrophil infiltration was detected by immunohistochemistry. Nuclear factor (NF)‑κB p65 and TREM‑1 were analyzed by western blotting, and the activation of NF‑κB was detected by electrophoretic mobility shift assay. LPS‑induced pathohistological injury, edema and neutrophil infiltration were significantly alleviated by TREM‑1 inhibitor, LR12. The proinflammatory cytokines [interleukin (IL)‑6, IL‑1β, tumor necrosis factor‑α] and chemokines (keratinocyte chemokine and monocyte chemoattractant protein‑1) were significantly reduced, whereas the anti‑inflammatory cytokines, IL‑10 were significantly increased by LR12. LR12 was identified to significantly decrease p65 expression levels in the nucleus and inhibit the activity of NF‑κB. Furthermore, LR12 alleviated LPS‑induced ALI by reducing the expression of TREM‑1, increasing the release of soluble TREM‑1 and inhibiting activation of the NF-κB signaling pathway.

Soluble TREM-1 Serum Level can Early Predict Mortality of Patients with Sepsis, Severe Sepsis and Septic Shock

Early prognostic prediction of sepsis is essential in adjusting therapeutic protocols to prevent deterioration and reduce mortality. We compared the predictive value of the serum concentration of the soluble triggering receptor expressed on myeloid cells 1 (sTREM-1) for 28-day mortality and for the development of severe sepsis or septic shock on the third day with the levels of interleukin (IL)-6, C-reactive protein (CRP) and procalcitonin (PCT). The study was conducted on 85 patients with sepsis. sTREM-1, CRP, PCT and IL-6 concentrations were measured upon study inclusion (day 0) and on days 1, 2, 3 and 5. APACHE II, SAPS II and SOFA scores were analyzed. The sTREM-1 levels (pg/ml) were higher in non-survivors than in survivors at admission (773 vs. 391, p < 0.001) and on days 1, 2, 3 and 5. In predicting the development of severe sepsis, the highest AUCs were found for PCT (0.744, 95% CI 0.638–0.85) and sTREM-1 (0.664, 95% CI 0.55–0.778); and in septic shock prediction, for PCT (0.766, 95% CI 0.665–0.867) and IL-6 (0.707, 95% CI 0.595–0.819). sTREM-1 positively correlated with APACHE II, SAPS II and SOFA scores. At inclusion, significant AUC for predicting 28-day mortality was 0.772 for the sTREM-1 (95% CI 0.672–0.871), 0.858 for APACHE II (95% CI 0.768–0.948), 0.847 for SAPS II (95% CI 0.733–0.96), 0.806 for SOFA score (95% CI 0.698–0.915). sTREM-1 can early predict the 28-day sepsis mortality, although its effectiveness is lower in comparison with clinical severity scores.

Ex vivo Stimulation of Lymphocytes with IL-10 Mimics Sepsis-Induced Intrinsic T-Cell Alterations

Profound T-cell alterations are observed in septic patients in association with increased risk of secondary infection and mortality. The pathophysiological mechanisms leading to such dysfunctions are not completely understood and direct and indirect mechanisms have been described. In this study we evaluated whether ex vivo stimulation of lymphocytes with IL-10, an immunosuppressive cytokine released at the systemic level during sepsis, could mimic sepsis-induced intrinsic T-cell alterations. We showed that recombinant human IL-10 priming of T cells altered their proliferative response to anti-CD2/CD3/CD28 antibody-coated beads and PHA stimulations, in a dose-dependent manner independently of accessory cells. This priming also significantly decreased T-cell secretion of IL-2 and IFNγ following stimulation. Furthermore, we demonstrated that IL-10 reduction of T-cell functionality was associated with increased FOXP3 expression in CD4⁺CD25⁺CD127^- regulatory T cells as observed in sepsis. Finally, we found that blocking the increased IL-10 concentration in plasma from septic shock patients increased the proliferative response of responding T cells from healthy controls. We describe here an ex vivo model recapitulating features of sepsis-induced intrinsic T-cell alterations. This should help, in further studies, to decipher the pathophysiological mechanisms of T-cell alterations induced after septic shock.

Soluble triggering receptor expressed on myeloid cell-1 (sTREM-1): a potential biomarker for the diagnosis of infectious diseases

Sensitive and useful biomarkers for the diagnosis and prognosis of infectious diseases have been widely developed. An example of these biomarkers is triggering receptor expressed on myeloid cell-1 (TREM-1), which is a cell surface receptor expressed on monocytes/macrophages and neutrophils. TREM-1 amplifies inflammation by activating the TREM-1/DAP12 pathway. This pathway is triggered by the interaction of TREM-1 with ligands or stimulation by bacterial lipopolysaccharide. Consequently, pro-inflammatory cytokines and chemokines are secreted. Soluble TREM-1 (sTREM-1) is a special form of TREM-1 that can be directly tested in human body fluids and well-known biomarker for infectious diseases. sTREM-1 level can be potentially used for the early diagnosis and prognosis prediction of some infectious diseases, including infectious pleural effusion, lung infections, sepsis, bacterial meningitis, viral infections (e.g., Crimean Congo hemorrhagic fever and dengue fever), fungal infections (e.g., Aspergillus infection), and burn-related infections. sTREM-1 is a more sensitive and specific biomarker than traditional indices, such as C-reactive protein and procalcitonin levels, for these infectious diseases. Therefore, sTREM-1 is a feasible biomarker for the targeted therapy and rapid and early diagnosis of infectious diseases.

Soluble membrane receptors, interleukin 6, procalcitonin and C reactive protein as prognostic markers in patients with severe sepsis and septic shock

Background

The objective of this study was to explore the diagnostic and prognostic value of soluble triggering receptor expressed on myeloid cell 1 (sTREM-1), soluble cluster of differentiation 14 (sCD14), soluble cluster of differentiation 163 (sCD163), interleukin-6 (IL-6), procalcitonin (PCT), and C-reactive protein (CRP) serum levels for patients with severe sepsis and septic shock in an intensive care unit (ICU).

Methods

Fifty patients admitted at the ICU with the diagnosis of severe sepsis or septic shock were studied. SOFA and APACHE II scores as well as serum biomarkers were measured at days 0, 2 and 5. The influence of these variables on 28-day mortality was analyzed. Twenty healthy individuals served as controls.

Results

Baseline serum concentrations of sTREM-1, sCD163, IL-6 and PCT correlated with SOFA score. Only sTREM-1 levels correlated with APACHE II score. The 28-day mortality rate for all patients was 42%. The absence of risk factors for infection, presence of septic shock, baseline values of sCD14 and decrease of PCT and IL-6 from baseline to day 5 were variables associated to mortality in the univariate analysis. The unique independent factor associated to mortality in the multivariate analysis was a decrease of PCT higher than 50% from days 0 to 5.

Conclusions

Serum levels of sTREM-1 are correlated with the severity of sepsis. A 50% decrease of PCT was the unique variable associated with survival in the multivariate analysis.

New parameters for childhood ventilator associated pneumonia diagnosis

PURPOSE

Our aim is to determine whether the presence of soluble triggering receptor expressed on myeloid cells-1 (s-TREM-1) of bronchoalveolar lavage fluid (BALF), serum procalcitonin levels (PCT), and Clinical Pulmonary Infection Score (CPIS) have diagnostic value in children with VAP.

METHODS

All children followed in pediatric intensive care unit (PICU) who were mechanically ventilated at least for 48 hr between January 2014 and December 2015 were enrolled into our study. BALF sample was obtained via non-bronchoscopic method from the children with VAP suspicion (case group) and s-TREM-1 levels were measured. Furthermore we calculated CPIS and measured serum PCT levels. Same procedures were applied to the control group who were admitted to PICU without infectious problems and who were not under antimicrobial therapy. First we compared the case group with the control group and then we compared the quantitative culture confirmed and non-confirmed VAP cases among themselves.

RESULTS

Case group (n:58) had significant higher PCT and s-TREM-1 levels compared to control group (n:58). The VAP confirmed cases had higher s-TREM-1, PCT ve CPIS levels compared to non-confirmed VAP cases. s-TREM-1, PCT ve CPIS variables were found to be independent risk factors for VAP. The cutoff values for s-TREM-1, CPIS, and PCT, are 281 pg/ml, 6, and 1.9 ng/ml, respectively. The patients whose s-TREM-1, CPIS, and PCT values above the cutoff levels were found to have higher cumulative VAP rate.

CONCLUSIONS

s-TREM-1 of BALF, serum PCT levels, and CPIS are useful predictors for ventilator-associated pneumonia diagnosis in children. Pediatr Pulmonol. 2017;52:119-128. © 2016 Wiley Periodicals, Inc.

Significance of soluble triggering receptor expressed on myeloid cells-1 elevation in patients admitted to the intensive care unit with sepsis

Background

Among septic patients admitted to the intensive care unit (ICU), early recognition of those with the highest risk of death is of paramount importance. Since clinical judgment is sometimes uncertain biomarkers could provide additional information likely to guide critical illness management. We evaluated the prognostic value of soluble Triggering Receptor Expressed by Myeloid cells 1 (sTREM-1), procalcitonin (PCT) and leucocyte surface expression of CD64.

Methods

This was a prospective cohort study, which included 190 septic patient admitted to the ICU in two hospitals. Blood samples for biomarker measurements were obtained upon admission and thereafter. The Simplified Acute Physiology Score (SAPS) II and the Sequential Organ Failure Assessment (SOFA) score were calculated. The primary outcome was all-cause death in the ICU.

Results

The mortality rate reached 25.8 %. The best predictive value of the three biomarkers was obtained with baseline sTREM-1, although clinical scores outperformed this. Accuracy was greater in patients without prior exposure to antibiotics and in those with proven bacterial infection. Adding sTREM-1 levels to SAPS II increased its specificity to 98 %. The soluble TREM-1 level, core temperature and SAPS II value were the only independent predictors of death after adjustment for potential confounders. A decrease in sTREM-1 with time was also more pronounced in survivors than in non-survivors.

Conclusions

sTREM-1 was found to be the best prognostic biomarker among those tested. Both baseline values and variations with time seemed relevant. Although SAPS II outperformed sTREM-1 regarding the prediction of ICU survival, the biomarker could provide additional information.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1893-4) contains supplementary material, which is available to authorized users.

Association of decreased serum sTREM-1 level with the severity of coronary artery disease: Inhibitory effect of sTREM-1 on TNF-α- and oxLDL-induced inflammatory reactions in endothelial cells

Soluble triggering receptor expressed on myeloid cells 1 (sTREM-1) is closely involved in autoimmune diseases and inflammatory reactions. We aimed to investigate whether serum sTREM-1 is related to coronary artery disease (CAD) and to evaluate the biological effects of sTREM-1 in cell experiments.This cross-sectional study included 263 consecutive patients with angiographically documented CAD, who were admitted for diagnosis and interventional treatment of CAD (CAD group), with 162 participants without CAD serving as controls (control group). Serum levels of sTREM-1 and high sensitivity C reactive protein (hsCRP) were determined in all participants. In cell experiments, the influence of sTREM-1 on tumor necrosis factor-α (TNF-α)- or oxidized low-density lipoprotein (oxLDL)-induced inflammatory reactions was evaluated in human umbilical vein endothelial cells (HUVECs).Serum level of sTREM-1 was significantly lower in CAD patients than in controls (P < 0.001). sTREM-1 values were related to the number of diseased coronary arteries (Spearman r = -0.413, P < 0.001) and the severity represented by Gensini score (Pearson r = -0.336, P < 0.001). Multivariable logistic regression analysis revealed that decreased sTREM-1 were independent determinants of CAD (OR = 0.428, P < 0.001). In cell experiments, recombinant sTREM-1 protein concentration-dependently inhibited the expression of IL-1β, IL-6, TNF-α, VCAM-1, and ICAM-1 induced by TNF-α or oxLDL in HUVECs.This study demonstrates that decreased serum sTREM-1 level is significantly associated with the presence and severity of CAD. sTREM-1 restrains inflammatory reaction in endothelial cells, suggesting that it might be a potential vascular protective factor.

Soluble TREM-1 as a diagnostic and prognostic biomarker in patients with septic shock: an observational clinical study

OBJECTIVES

The impact of TREM-1-mediated inflammation was investigated in different inflammatory settings.

METHODS

Secondary analyses of an observational clinical pilot study, including 60 patients with septic shock, 30 postoperative controls and 30 healthy volunteers.

RESULTS

Plasma levels of sTREM-1 were found to identify patients with septic shock more effectively than procalcitonin and C-reactive protein. Moreover, sTREM-1 was identified to be an early predictor for survival in patients with septic shock.

CONCLUSION

Due to its diagnostic as well as prognostic value in sepsis syndrome, implementation of sTREM-1 measurements in routine diagnostics should be taken into account.

Role of sTREM-1 in predicting mortality of infection: a systematic review and meta-analysis

OBJECTIVES

Several studies have investigated the prognostic value of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) in patients with infection. However, the result was controversial. Thus, the purpose of the present meta-analysis was to determine the prognostic value of the sTREM-1 level in predicting mortality at the initial stage of infection.

METHODS

The literature was searched in the PubMed, EMBASE, Web of Knowledge and Cochrane databases. A 2×2 contingency table was constructed on the basis of mortality and sTREM-1 levels in patients with infection. 2 authors independently judged study eligibility and extracted data. The prognostic value of sTREM-1 in predicting mortality was determined using a bivariate meta-analysis model. Q-test and I(2) index were used to test heterogeneity.

RESULTS

9 studies were selected from 803 studies. An elevated sTREM-1 level was associated with a higher risk of death in infection, with pooled risk ratio (RR) was 2.54 (95% CI 1.77 to 3.65) using a random-effects model (I(2)=53.8%). With the bivariate random-effects regression model, the pooled sensitivity and specificity of sTREM-1 to predict mortality in infection were 0.75 (95% CI 0.61 to 0.86) and 0.66 (95% CI 0.54 to 0.75), respectively. The diagnostic OR was 6 (95% CI 3 to 10). The overall area under the summary receiver operator characteristic (SROC) curve was 0.76 (95% CI 0.72 to 0.79). When we calculated the sepsis subgroup, the pooled RR was 2.98 (95% CI 2.19 to 4.40). The pooled sensitivity and specificity were 0.74 (95% CI 0.58 to 0.85) and 0.72 (95% CI 0.62 to 0.80), respectively. The overall area under the SROC curve was 0.78 (95% CI 0.74 to 0.81).

CONCLUSIONS

Elevated sTREM-1 concentrations had a moderate prognostic significance in assessing the mortality of infection in adult patients. However, sTREM-1 alone is insufficient to predict mortality as a biomarker.

Evaluation and Validation of the Detection of soluble Triggering Receptor Expressed on Myeloid Cells 1 by Enzyme-linked immunosorbent Assay

Triggering receptor expressed on myeloid cells (TREM)-1 plays an important role in innate immune responses and is upregulated under infectious as well as non-infectious conditions. In addition, a soluble TREM-1 variant (sTREM-1) is detectable in sera or bronchoalveolar-lavage fluids from patients. Currently, various studies are difficult to compare, since the methods of detection by enzyme-linked immunosorbent assays (ELISA) vary among different research groups. In this study, we compared three different s-TREM-1 specific ELISAs and identified individual assay characteristics finding notable differences in sTREM-1 concentrations in part depending on the employed buffers. Investigating potential confounding factors for sTREM-1 detection, serum heat-inactivation (HI) showed improved recovery compared to non-HI (NHI) serum, reproducible by addition of complement and re-heat-inactivation. Hence we identified complement as a heat-sensitive confounder in some sTREM-1 ELISAs. We conclude that it is difficult to directly compare data of several studies, in particular if different ELISAs are engaged. Immunoassays for research use only are in general hampered by lack of standardization. Further standardization is needed until sTREM-1 ELISA is capable for better reproducibility of studies and clinical application.

Host response biomarkers in sepsis: overview on sTREM-1 detection

The diagnosis of sepsis, and especially its differentiation from sterile inflammation, may be challenging. TREM-1, the triggering receptor expressed on myeloid cells-1, is an amplifier of the innate immune response. Its soluble form acts as a decoy for the natural TREM-1 ligand and dampens its activation. In this chapter, we review the numerous studies that have evaluated the usefulness of sTREM-1 concentration determination for the diagnosis and the prognosis evaluation of sepsis or localized infection. Nowadays, sandwich ELISA kits are available and the assay is described.

sTREM-1 predicts intensive care unit and 28-day mortality in cancer patients with severe sepsis and septic shock

INTRODUCTION

The innate immune response molecules and their use as a predictor of mortality in cancer patients with severe sepsis and septic shock are poorly investigated.

OBJECTIVE

To analyze the value of interleukin (IL)-1ß, IL-6, IL-8, IL-10, IL-12, tumor necrosis factor α (TNF-α), soluble triggering receptor expressed on myeloid cells 1 (sTREM-1), and high-mobility group box 1 (HMGB-1) as predictors of mortality in cancer patients with severe sepsis and septic shock compared with septic patients without malignancies.

DESIGN

Prospective, observational cohort study.

SETTING

Tertiary level adult intensive care unit (ICU).

SUBJECTS

Seventy-five patients with severe sepsis or septic shock, 40 with cancer and 35 without.

INTERVENTIONS AND MEASUREMENTS

Laboratory data were collected at ICU admission, 24 and 48 hours after. Plasma concentrations of HMGB-1 and sTREM-1 were measured by enzyme-linked immunosorbent assay, whereas cytokines were measured by cytometric bead array.

RESULTS

Intensive care unit mortality in cancer and noncancer patients was 40% and 28.6% (P = .29), and 28-day mortality was 45% and 34.3% (P = .34). Proinflammatory cytokines IL-1ß, IL-6, IL-8, IL-12, and TNF-α showed significantly higher values in the cancer group. Interleukin-10 at 48 hours (P = .01), sTREM-1 in all measurements (P < .01) and HMGB-1 at 24 hours (P < .01) showed significantly lower values in the cancer group. In addition, for the cancer group, sTREM-1 at 24 hours (P = .02) and 48 hours (P = .01) showed higher levels in nonsurvivors patients. The area under the receiver operating characteristic curve for predicting ICU mortality for sTREM-1 was 0.73 (95% confidence interval, 0.57-0.89; P = .01). Multivariate logistic analysis showed that the days spent in mechanical ventilation and levels of sTREM-1 and IL-1ß at 48 hours were independent predictors of ICU mortality; corticosteroids requirement and levels of sTREM-1 and TNF-α at 24 hours were independent predictors of 28-day mortality.

CONCLUSIONS

Patients with cancer have different immune profile in sepsis when compared with patients without cancer, as demonstrated for levels of cytokines, sTREM-1 and HMGB-1. sTREM-1 and days spent in mechanical ventilation proved to be good predictors of ICU and 28-day mortality in cancer patients.

Ventilator-Associated Pneumonia: When to hold the breath?

Ventilator-associated pneumonia (VAP) is the most common infection in mechanically ventilated patients, and carries the highest mortality. An early diagnosis and definitive management not only reduces the overall mortality, but also brings down the burden of health care to the patient by reducing the cost, length of Intensive Care Unit (ICU) stay, duration of mechanical ventilation, and so on. Out of the various scoring systems, the Clinical Pulmonary Infection Score (CPIS) calculation for VAP has a good sensitivity (72%) and specificity (85%) and the targeted antibiotic therapy in the appropriate dosage is found to be more beneficial than empirical treatment. Although controversies persist on several issues, preventive strategies like head elevation by 30 degrees, cuff pressure monitoring, avoidance of sedatives and muscle relaxants, and so on, have been found to reduce the occurrence of VAP.

Dexamethasone Down-Regulates Expression of Triggering Receptor Expressed on Myeloid Cells-1: Evidence for a TNFα-Related Effect

Objectives: To investigate the effect of dexamethasone on triggering receptor expressed on myeloid cells-1 (TREM-1).

Methods: Wild-type and tumor necrosis factor (TNF^−/−) mice were pre-treated with saline, dexamethasone, or hydrocortisone and exposed to a lethal infection of Pseudomonas aeruginosa. Mortality and TREM-1 on neutrophil membranes was measured after sacrifice. U937 human monocytic cells were stimulated with lipopolysaccharide (LPS) or heat-killed P. aeruginosa without or with dexamethasone or hydrocortisone, and cell-surface TREM-1 and soluble TREM-1 (sTREM-1) were quantified. Expression of TREM-1 and sTREM-1 was also studied in LPS-stimulated U937 cells incubated in the absence or presence of TNFα or anti-TNFα antibody.

Results: Pre-treatment with dexamethasone, but not hydrocortisone, prolonged animal survival. Mice pre-treated with dexamethasone showed decreased expression of TREM-1 on neutrophils. In U937 cells, LPS or heat-killed P. aeruginosa induced the expression of TREM-1 and the release of sTREM-1. U937 TREM-1 and sTREM-1 were decreased upon addition of dexamethasone but not hydrocortisone. The suppressive effect of dexamethasone was enhanced in the presence of exogenous TNFα and lost in the presence of anti-TNFα antibody. In TNF^−/− mice, dexamethasone suppression of mortality and TREM-1 neutrophil expression was lost. Gene expression of TREM-1 in U937 monocytes was decreased after treatment with dexamethasone.

Conclusion: TREM-1/sTREM-1 is a novel site of action of dexamethasone. This action is associated with down-regulation of gene expression and is mediated by TNFα.

Expression of TREM-1 in hepatic stellate cells and prognostic value in hepatitis B-related hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a typical inflammation-related malignancy characterized by high postoperative recurrence and metastasis. Although several inflammatory cells and inflammatory signatures have been linked to poor prognosis, the inflammation-associated molecular mechanisms of HCC development and progression are largely unknown. Here we show that triggering receptor expressed in myeloid cells (TREM)-1, a transmembrane receptor expressing in myeloid cells, was also expressed in tumor-activated hepatic stellate cells (HSCs) and associated with the aggressive behavior of HCC cells. Enzyme-linked immunosorbent assay was used to measure the expression levels of soluble TREM-1 (sTREM-1) in activated hepatic stellate cells supernatant and 92 preoperative and postoperative plasmas of patients with malignancy and/or benign liver tumor/disease, respectively. Expression levels of TREM-1 were assessed by immunohistochemistry in tissue microarray from 240 patients with HCC. As a result, increased secretion of sTREM-1 from activated HSCs was observed after co-culture with HCC cell lines (P < 0.001), and conditioned medium collected from activated HSCs/cancer associated myofibroblasts (CAMFs) with or without agonist/inhibitor of TREM-1 significantly changed the migratory ability of HCC cells. The levels of sTREM-1 were significantly higher in patients with HCC than those with benign liver tumors (P < 0.005). Peritumoral density of TREM-1 was shown to be an independent prognosis predictor according to univariate (P < 0.001 for both overall survival and time to recurrence) and multivariate analysis (P = 0.008 for overall survival; P = 0.005 for time to recurrence). Thus, these observations suggest that TREM-1 is related to the aggressive tumor behavior and has potential value as a prognostic factor for HCC.

TREM-1 expression on neutrophils and monocytes of septic patients: relation to the underlying infection and the implicated pathogen

BACKGROUND

Current knowledge on the exact ligand causing expression of TREM-1 on neutrophils and monocytes is limited. The present study aimed at the role of underlying infection and of the causative pathogen in the expression of TREM-1 in sepsis.

METHODS

Peripheral venous blood was sampled from 125 patients with sepsis and 88 with severe sepsis/septic shock. The causative pathogen was isolated in 91 patients. Patients were suffering from acute pyelonephritis, community-acquired pneumonia (CAP), intra-abdominal infections (IAIs), primary bacteremia and ventilator-associated pneumonia or hospital-acquired pneumonia (VAP/HAP). Blood monocytes and neutrophils were isolated. Flow cytometry was used to estimate the TREM-1 expression from septic patients.

RESULTS

Within patients bearing intrabdominal infections, expression of TREM-1 was significantly lower on neutrophils and on monocytes at severe sepsis/shock than at sepsis. That was also the case for severe sepsis/shock developed in the field of VAP/HAP. Among patients who suffered infections by Gram-negative community-acquired pathogens or among patients who suffered polymicrobial infections, expression of TREM-1 on monocytes was significantly lower at the stage of severe sepsis/shock than at the stage of sepsis.

CONCLUSIONS

Decrease of the expression of TREM-1 on the membrane of monocytes and neutrophils upon transition from sepsis to severe sepsis/septic shock depends on the underlying type of infection and the causative pathogen.

Early serum levels of soluble triggering receptor expressed on myeloid cells-1 in septic patients: correlation with monocyte gene expression

PURPOSE

To define early kinetics of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) and of TREM-1 monocyte gene expression in critically ill patients with sepsis.

METHODS

Blood was sampled at regular time intervals from 105 patients with sepsis. Concentrations of tumour necrosis factor α (TNFα), interleukin (IL)-6, IL-8 and IL-10 and IL-12p70 and sTREM-1 were measured by an enzyme immunoassay. Blood mononuclear cells were isolated on day 0 from 20 patients and 10 healthy volunteers; RNA was extracted and gene expression of TREM-1 and TNFα were assessed by reverse transcriptase polymerase chain reaction.

RESULTS

Early serum concentrations of sTREM-1 were greater among patients with severe sepsis/shock than among patients with sepsis; those of TNFα, IL-6, IL-8 and IL-10 were pronounced among patients with septic shock. Gene transcripts of TNFα were lower among patients with severe sepsis/shock than among patients with sepsis; that was not the case for TREM-1. Early serum levels of sTREM-1 greater than 180 pg/mL were predictors of shorter duration of mechanical ventilation.

CONCLUSIONS

Although serum levels of sTREM-1 are increased early upon advent of severe sepsis/shock, gene expression of TREM-1 on monocytes in severe sepsis/shock is not increased. These findings add considerably to our knowledge on the pathophysiology of sepsis.

Triggering receptor expressed on myeloid cell 1

Sepsis is a common cause of morbidity and mortality in intensive care units. There is no gold standard for diagnosing sepsis because clinical and laboratory signs are neither sensitive nor specific enough and microbiological studies often show negative results. The triggering receptor expressed on myeloid cell 1 (TREM-1) is a member of the immunoglobulin superfamily. Its expression is upregulated on phagocytic cells in the presence of bacteria or fungi. This article reports on the potential usefulness of the assessment of the soluble form of TREM-1 in biologic fluids in the diagnosis of infection.

Dynamic changes of serum soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) reflect sepsis severity and can predict prognosis: a prospective study

BACKGROUND

We examined the utility of serum levels of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) for the diagnoses, severity assessments, and predicting the prognoses of patients with sepsis and compared sTREM-1 values with those of C-reactive protein (CRP) and procalcitonin (PCT).

METHODS

Fifty-two patients with sepsis were included: 15 sepsis cases and 37 severe sepsis cases (severe sepsis + septic shock). Serum levels of sTREM-1, CRP, and PCT were determined on days 1, 3, 5, 7, 10, and 14 after admission to an ICU.

RESULTS

Serum sTREM-1 levels of patients with severe sepsis were significantly higher than for those with sepsis on day 1 (240.6 pg/ml vs. 118.3 pg/ml; P < 0.01), but CRP and PCT levels were not significantly different between the two groups. The area under an ROC curve for sTREM-1 for severe sepsis patients was 0.823 (95% confidence interval: 0.690-0.957). Using 222.5 pg/ml of sTREM-1 as the cut-off value, the sensitivity was 59.5%, the specificity was 93.3%, the positive predictive value was 95.6%, the negative predictive value was 48.3%, the positive likelihood ratio was 8.92, and the negative likelihood ratio was 0.434. Based on 28-day survivals, sTREM-1 levels in the surviving group showed a tendency to decrease over time, while they tended to gradually increase in the non-surviving group. sTREM-1 levels in the non-surviving group were higher than those in the surviving group at all time points, whereas CRP and PCT levels showed a tendency to decrease over time in both groups. sTREM-1 levels and Sequential Organ Failure Assessment (SOFA) scores were positively correlated (r = 0.443; P < 0.001), and this correlation coefficient was greater than the correlation coefficients for both CRP and PCT.

CONCLUSIONS

Serum sTREM-1 levels reflected the severity of sepsis more accurately than those of CRP and PCT and were more sensitive for dynamic evaluations of sepsis prognosis.

Indication for a role of regulatory T cells for the advent of influenza A (H1N1)-related pneumonia

Regulatory T cells (T(regs) ) have an anti-inflammatory role. A former study in a limited number of patients found that absolute counts of T(regs) increase when infection by the new influenza H1N1 virus is complicated with pneumonia. These results generate the question if H1N1-related pneumonia is associated with a state of hypo-inflammation. A total of 135 patients were enrolled with blood sampling within less than 24 h from diagnosis; 23 with flu-like syndrome; 69 with uncomplicated H1N1-infection; seven with bacterial pneumonia; and 36 with H1N1-related pneumonia. T(regs) and CD14/HLA-DR co-expression were estimated by flow cytometry; concentrations of tumour necrosis factor-alpha (TNF-α), of interleukin (IL)-6 and of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) by an enzyme immunoassay; those of procalcitonin (PCT) by immuno-time-resolved amplified cryptate technology assay. Expression of human leucocyte antigen D-related (HLA-DR) on monocytes was similar between groups; absolute T(reg) counts were greater among patients with H1N1-related pneumonia than flu-like syndrome or H1N1-uncomplicated infection. Serum TNF-α of patients with bacterial pneumonia was greater than those of other groups, but IL-10 was similar between groups. Serum PCT was greater among patients with H1N1-related pneumonia and sTREM-1 among those with H1N1-related pneumonia. Regression analysis revealed that the most important factors related with the advent of pneumonia were the existence of underlying illnesses (P = 0·006) and of T(regs) equal to or above 16 mm(3) (P = 0·013). It is concluded that the advent of H1N1-related pneumonia is related to an early increase of the absolute T(reg) counts. This increase is probably not part of a hypo-inflammatory state of the host.

Diagnostic value of triggering receptor expressed on myeloid cells-1 and C-reactive protein for patients with lung infiltrates: an observational study

Background

Differential diagnosis of patients with lung infiltrates remains a challenge. Triggering receptor expressed on myeloid cells (TREM)-1 is a neutrophil and monocyte receptor up-regulated during infection. The aim of this study was to evaluate the diagnostic accuracy of TREM-1 and of C-reactive protein (CRP) from patients with lung infiltrates to discern community acquired lung infections.

Methods

68 patients admitted to a medical ward with acute respiratory illness were enrolled in the study. Neutrophil and monocyte TREM-1 expression were measured by flow cytometry, sTREM-1 by an enzyme immunoassay and C-reactive protein by nephelometry. Clinical pulmonary infection score was recorded.

Results

34 patients were diagnosed with bacterial community acquired pneumonia (group A) and 34 with non-bacterial pulmonary disease (group B). Median serum TREM-1 concentration was 102.09 pg/ml in group A and lower than 15.10 pg/ml (p < 0.0001) in group B. Mean±SE neutrophil TREM-1 expression was 4.67 ± 0.53 MFI in group A and 2.64 ± 0.25 MFI (p = 0.001) in group B. Monocyte TREM-1 expression was 4.2 ± 0.42 MFI in group A and 2.64 ± 0.35 MFI (p = 0.007) in group B and mean±SE CRP was 18.03 ± 2 mg/ml in group A and 7.1 ± 1.54 mg/ml (p < 0.001) in group B. A cut-off of 19.53 pg/ml of sTREM-1 with sensitivity 82.6% and specificity 63% to discriminate between infectious and non-infectious pulmonary infiltrates was found. sTREM-1 at admission greater than 180 pg/ml was accompanied with unfavourable outcome.

Conclusion

TREM-1 myeloid expression and sTREM-1 are reliable markers of bacterial infection among patients with pulmonary infiltrates; sTREM-1 is a predictor of final outcome.

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

Introduction

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.

Methods

Three intensive care units in tertiary care university hospitals in Greece and Germany participated. 375 and 415 postoperative patients and 159 patients with ventilator associated pneumonia (VAP) were included. TLR4 and TIRAP/Mal polymorphisms in 375 general surgical patients were associated with risk of infection, clinical course and outcome. In two prospective studies, 415 patients following cardiac surgery and 159 patients with newly diagnosed VAP predominantly caused by Gram-negative bacteria were studied for cytokine levels in-vivo and after ex-vivo monocyte stimulation and clinical course.

Results

Patients simultaneously carrying polymorphisms in TIRAP/Mal and TLR4 and patients homozygous for the TIRAP/Mal SNP had a significantly higher risk of severe infections after surgery (odds ratio (OR) 5.5; confidence interval (CI): 1.34 - 22.64; P = 0.02 and OR: 7.3; CI: 1.89 - 28.50; P < 0.01 respectively). Additionally we found significantly lower circulating cytokine levels in double-mutant individuals with ventilator associated pneumonia and reduced cytokine production in an ex-vivo monocyte stimulation assay, but this difference was not apparent in TIRAP/Mal-homozygous patients. In cardiac surgery patients without infection, the cytokine release profiles were not changed when comparing different genotypes.

Conclusions

Carriers of mutations in sequential components of the TLR signaling system may have an increased risk for severe infections. Patients with this genotype showed a decrease in cytokine release when infected which was not apparent in patients with sterile inflammation following cardiac surgery.

Diagnostic utility of elevated serum soluble triggering receptor expressed on myeloid cells (sTREM)-1 in infected neonates

OBJECTIVE

To assess the value of serum levels of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) for early diagnosis of late-onset sepsis (LOS) in neonates, compared with interleukin-6 (IL-6).

DESIGN AND SETTING

Prospective, observational study in a single, level III neonatal intensive care unit of a university hospital.

PATIENTS

Fifty-two preterm and term neonates evaluated for suspected LOS were studied. Neonates were classified into two groups: infected [confirmed sepsis (n = 22) and possible sepsis (n = 9)] and noninfected neonates (n = 21).

MEASUREMENTS AND RESULTS

Serum sTREM-1 and IL-6 were measured (enzyme-linked immunosorbent assays) when signs suggestive of sepsis emerged. Infected neonates had significantly higher sTREM-1 (p = 0.004) and IL-6 (p < 0.0001) than noninfected neonates. Receiver operating characteristic (ROC) curve analysis resulted in significant areas under the curve (AUC) for both sTREM-1 (AUC = 0.733, p = 0.005) and IL-6 (AUC = 0.892, p = 0.001) for identification of infected neonates, with the difference between the two AUC not being significant. Further analysis documented acceptable diagnostic performance of sTREM-1 and IL-6, which was not improved, however, when the two markers were combined.

CONCLUSIONS

Serum sTREM-1 increases in infected neonates. Diagnostic accuracy of sTREM-1 either alone or in combination with IL-6 is not better than that of IL-6.

[Prognostic value of the sTREM-1 plasma values in patients with sepsis: a cohort study]

OBJECTIVE

To evaluate the association between plasma levels of soluble Triggering Receptor Expressed on Myeloid Cells-1 (sTREM-1) and mortality of patients with sepsis.

DESIGN

Prospective cohort study.

SETTING

Two general Intensive Care Units.

PATIENTS

Patients with sepsis in whom sTREM-1 plasma levels were determined daily in the first 3 days of their presentation.

VARIABLES OF INTEREST

Mortality at 28 days.

RESULTS

We analyzed 121 patients (23% severe sepsis, 44% septic shock, 33% non-severe sepsis). Mortality at 28 days was 24.8%. The initial sTREM-1 levels were slightly higher in nonsurvivors than in survivors (median 366.9 versus 266.5 pg/ml, p=0.2668). An increase in sTREM-1 levels higher than 90 pg/ml within the first 3 days (delta-TREM) was associated with an excess of mortality (hazard ratio [HR] 2.68, p=0.0047), with a sensitivity of 47% and a specificity of 78%. This excess of mortality disappeared after adjusting for severity by Cox analysis (adjusted HR 1.07, p=0.8665).

CONCLUSIONS

The increase in the levels of sTREM-1 during the first 3 days of evolution is associated with an excess of mortality in critically ill patients with sepsis. This is explained by the greater initial severity of these patients. The discriminative capacity of this finding is insufficient to be clinically useful.

Soluble TREM-1 is not suitable for distinguishing between systemic inflammatory response syndrome and sepsis survivors and nonsurvivors in the early stage of acute inflammation

BACKGROUND AND OBJECTIVE

To evaluate plasma levels of soluble TREM-1 (sTREM-1) in patients with systemic inflammatory response syndrome (SIRS), severe sepsis, and septic shock and to determine whether plasma sTREM-1 could be used as a diagnostic and prognostic marker in sepsis in the surgical ICU.

METHODS

The study was designed as an observational noninterventional clinical study in a surgical ICU of a university hospital. For this, 65 intensive care patients were enrolled within the first 24 h after onset of SIRS (n = 11), severe sepsis (n = 39) or septic shock (n = 15). In addition, 21 healthy volunteers served as controls. At days 0, 1, and 3 after diagnosis, plasma sTREM-1 was measured by ELISA.

RESULTS

Plasma sTREM-1 concentrations in healthy controls did not significantly differ from those in patients with SIRS, severe sepsis, or septic shock at days 0, 1, and 3. Survivors were defined as septic patients surviving for at least 28 days. There were no differences in plasma sTREM-1 levels between survivors (n = 22) and nonsurvivors (n = 27) on any day.

CONCLUSIONS

In this study in patients with SIRS, severe sepsis, or septic shock, plasma sTREM-1 levels were not elevated as compared with healthy controls. Measurement of plasma sTREM-1 did not distinguish between patients with SIRS, severe sepsis, or septic shock or between survivors and nonsurvivors. The suggested role of sTREM-1 as a diagnostic and prognostic marker in sepsis should be carefully verified.

Monocytes as a site of production of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) in the septic host

The role of blood monocytes in the secretion of soluble triggering receptor expressed on myeloiod cells (sTREM-1) was studied in 90 patients with septic syndrome due to ventilator-associated pneumonia. Blood monocytes were isolated on 7 consecutive d after initiation of symptoms. Monocytes were incubated in the absence or presence of LPS and concentrations of sTREM-1 and TNFalpha in cell supernatants and serum were estimated by an enzyme-immunoassay. sTREM-1 and TNFalpha were consistently present at detectable levels in the cell supernatants. LPS induced increased levels of TNFalpha but not of sTREM-1. Supernatants recovered from monocytes on d 1 showed levels of sTREM-1 higher than those recovered on any of the following 6 d (p<0.05); these levels were higher in non-survivors than in survivors. Supernatants recovered from monocytes on d 1 of patients with severe sepsis had elevated concentrations of sTREM-1 compared to patients with septic shock and similar to patients with sepsis. A negative correlation was found between levels of sTREM-1 in the cell supernatants and the percentage of apoptotic monocytes. In essence, the above results suggest that monocytes contribute to the production of sTREM-1 in the event of septic syndrome.

Angiopoietin-2 is increased in septic shock: evidence for the existence of a circulating factor stimulating its release from human monocytes

We aimed to investigate if angiopoietin-2 (Ang-2) participates in the septic process and what may be the role of monocytes as a site of release of Ang-2 in sepsis. Concentrations of Ang-2 were estimated in sera and in supernatants of monocytes derived form one already described cohort of 90 patients with septic syndrome due to ventilator-associated pneumonia (VAP). Mononuclear cells of 17 healthy volunteers were stimulated by serum of patients in the presence or absence of various intracellular pathway inhibitors. Ang-2 gene expression after stimulation was also tested. Ang-2 was higher in patients with septic shock compared to patients with sepsis, severe sepsis and controls. Ang-2 was significantly increased in non-survivors compared with survivors. Serum levels greater than 9700 pg/ml were accompanied by a 3.254 odds ratio for death (p: 0.033). Ang-2 release from monocytes of septic patients was slightly decreased after stimulation with lipopolysaccharide (LPS) of Escherichia coli O55:B5. Release of Ang-2 from healthy mononuclear cells was stimulated by serum of patients with shock but not by serum of non-shocked patients (p: 0.016). Release was decreased by LPS; increased in the presence of a TLR4 antagonist; and decreased by anti-TNF antibody. RNA transcripts of PBMCs after stimulation with serum of patients with septic shock were higher than those after LPS stimulation. It is concluded that Ang-2 is increased in serum in the event of septic shock and that its increase is related to unfavorable outcome. It seems that a circulating factor may exist in the serum of patients with septic shock that stimulates gene expression and subsequent release of Ang-2 from monocytes. TLR4 and TNFalpha modulate release of Ang-2.

Evidence for the participation of soluble triggering receptor expressed on myeloid cells-1 in the systemic inflammatory response syndrome after multiple trauma

BACKGROUND

Based on the implication of soluble triggering receptor expressed on myeloid cells (sTREM-1) in the septic cascade, it was investigated whether it participates or not in posttraumatic systemic inflammatory response syndrome (SIRS).

METHODS

Blood was sampled on days 1, 4, 7, and 15 from 69 patients with SIRS after multiple injuries and upon presentation of a septic complication. Concentrations of sTREM-1, tumor necrosis factor-alpha (TNFalpha), interleukin (IL)-6, IL-8, and interferon-gamma were determined by an enzyme immunoassay. Samples drawn on day 1 from 10 trauma patients without SIRS served as controls.

RESULTS

In 26 patients with SIRS without septic complication, sTREM-1, TNFalpha, and IL-8 remained stable over follow-up; IL-6 decreased and interferon-gamma increased on days 4 and 7 compared with day 1. TNFalpha was the only variable being higher upon advent of septic shock compared with patients without SIRS and upon presentation of SIRS, sepsis, and severe sepsis (p of comparisons with all subgroups <0.0001). Mortality of patients with sTREM-1 greater than 180 pg/mL was 5.3% compared with 28.0% of those with sTREM-1 lower than 180 pg/mL (p 0.035). sTREM-1 higher than 40 pg/mL had sensitivity 56.5% and specificity 91.7% for the differential diagnosis between SIRS and sepsis after multiple injuries.

CONCLUSIONS

This is the first study providing evidence about the participation of sTREM-1 in posttraumatic SIRS. Its levels are increased and remain constant over time in patients who did not develop any complications whereas it seems to behave as an anti-inflammatory mediator.

How well do serum sTREM-1 measurements prognosticate in septic shock?

The soluble triggering receptor expressed on myeloid cells (sTREM)-1 has emerged as a potentially useful biomarker for the diagnosis of sepsis. This study aimed to evaluate the prognostic utility of serum sTREM-1 in septic shock, in comparison with that of procalcitonin measurements. Thirty-one consecutive patients in a tertiary medical intensive care unit with septic shock were studied. sTREM-1 levels in blood were measured using a modified immunoblot array technique on days one to three of intensive care unit admission. Serum procalcitonin and interleukin (IL)-1beta, IL-6, IL-IO and tumour necrosis factor-alpha levels were also measured. No significant difference was observed in the sTREM-1 levels on the first three days between survivors and nonsurvivors. sTREM-1 levels moderately correlated with the Acute Physiology and Chronic Health Evaluation II and Sequential Organ Failure Assessment scores on day three, but did not correlate with vasopressor requirements, cytokine levels and the presence of bacteraemia. In contrast, procalcitonin levels were significantly higher in nonsurvivors than in survivors on days two and three. A significant relationship also existed between procalcitonin levels and the other variables. In conclusion, this study found that the prognostic utility of serum sTREM-1 in septic shock is poor and that procalcitonin measurements perform better in this regard.

Aging and neutrophils: there is still much to do

Human neutrophils are activated by a wide array of compounds through their receptors. This elicits their classical functions, such as chemotaxis, phagocytosis, and the production of reactive oxygen species (ROS). Upon stimulation, neutrophils also produce lipid and immune mediators and can present antigen through the major histocompatibility complex I (MHC-I). The age-related impairment of the classical functions of neutrophils is well described, but experimental evidence showing alterations in the production of mediators and antigen presentation with aging are lacking. This review highlights the role of neutrophils in age-related pathologies such as Alzheimer's disease, atherosclerosis, cancer, and autoimmune diseases. Furthermore, we discuss how aging potentially affects the production and release of mediators by human neutrophils in ways that may contribute to the development of these pathologies.

TLR4 polymorphisms, infectious diseases, and evolutionary pressure during migration of modern humans

Infectious diseases exert a constant evolutionary pressure on the genetic makeup of our innate immune system. Polymorphisms in Toll-like receptor 4 (TLR4) have been related to susceptibility to Gram-negative infections and septic shock. Here we show that two polymorphisms of TLR4, Asp299Gly and Thr399Ile, have unique distributions in populations from Africa, Asia, and Europe. Genetic and functional studies are compatible with a model in which the nonsynonymous polymorphism Asp299Gly has evolved as a protective allele against malaria, explaining its high prevalence in subSaharan Africa. However, the same allele could have been disadvantageous after migration of modern humans into Eurasia, putatively because of increased susceptibility to severe bacterial infections. In contrast, the Asp299Gly allele, when present in cosegregation with Thr399Ile to form the Asp299Gly/Thr399Ile haplotype, shows selective neutrality. Polymorphisms in TLR4 exemplify how the interaction between our innate immune system and the infectious pressures in particular environments may have shaped the genetic variations and function of our immune system during the out-of-Africa migration of modern humans.