Adam Linder

Heparin-Binding Protein: An Early Marker of Circulatory Failure in Sepsis

BACKGROUND The early detection of circulatory failure in patients with sepsis is important for successful treatment. Heparin-binding protein (HBP), released from activated neutrophils, is a potent inducer of vascular leakage. In this study, we investigated whether plasma levels of HBP could be used as an early diagnostic marker for severe sepsis with hypotension. METHODS A prospective study of 233 febrile adult patients with a suspected infection was conducted. Patients were classified into 5 groups on the basis of systemic inflammatory response syndrome criteria, organ failure, and the final diagnosis. Blood samples obtained at enrollment were analyzed for the concentrations of HBP, procalcitonin, interleukin-6, lactate, C-reactive protein, and the number of white blood cells. RESULTS Twenty-six patients were diagnosed with severe sepsis and septic shock, 44 patients had severe sepsis without septic shock, 100 patients had sepsis, 43 patients had an infection without sepsis, and 20 patients had an inflammatory response caused by a noninfectious disease. A plasma HBP level > or = 15 ng/mL was a better indicator of severe sepsis (with or without septic shock) than any other laboratory parameter investigated (sensitivity, 87.1%; specificity, 95.1%; positive predictive value, 88.4%; negative predictive value, 94.5%). Thirty-two of the 70 patients with severe sepsis were sampled for up to 12 h before signs of circulatory failure appeared, and in 29 of these patients, HBP plasma concentrations were already elevated. CONCLUSION In febrile patients, high plasma levels of HBP help to identify patients with an imminent risk of developing sepsis with circulatory failure.

Small Acute Increases in Serum Creatinine Are Associated with Decreased Long-Term Survival in the Critically Ill

RATIONALE Long-term outcomes after acute kidney injury (AKI) are poorly described. OBJECTIVES We hypothesized that one single episode of minimal (stage 1) AKI is associated with reduced long-term survival compared with no AKI after recovery from critical illness. METHODS A prospective cohort of 2,010 intensive care unit (ICU) patients admitted to the ICU between years 2000 and 2009 at a provincial tertiary care hospital. Development of AKI was determined according to the KDIGO classification and mortality up to 10 years after ICU admission was recorded. MEASUREMENTS AND MAIN RESULTS Of the 1,844 eligible patients, 18.4% had AKI stage 1, 12.1% had stage 2, 26.5% had stage 3, and 43.0% had no AKI. The 28-day, 1-year, 5-year, and 10-year survival rates were 67.1%, 51.8%, 44.1%, and 36.3% in patients with mild AKI, which was significantly worse compared with the critically ill patients with no AKI at any time (P < 0.01). The unadjusted 10-year mortality hazard ratio was 1.53 (95% confidence interval, 1.2-2.0) for 28-day survivors with stage 1 AKI compared with critically ill patients with no AKI. Adjusted 10-year mortality risk was 1.26 (1.0-1.6). After propensity matching stage 1 AKI with no AKI patients, mild AKI was still significantly associated with decreased 10-year survival (P = 0.036). CONCLUSIONS Patients with one episode of mild AKI have significantly lower long-term survival rates than critically ill patients with no AKI. Close medical follow-up of these patients may be warranted and mechanistic research is required to understand how AKI influences long-term events.

Cathelicidin LL-37 in Severe Streptococcus pyogenes Soft Tissue Infections in Humans

ABSTRACT Severe soft tissue infections, such as necrotizing fasciitis and severe cellulitis, caused by group A streptococci (GAS) are rapidly progressing life-threatening infections characterized by massive bacterial loads in the tissue even late after the onset of infection. Antimicrobial peptides are important components of the innate host defense, and cathelicidins have been shown to protect against murine necrotic skin infections caused by GAS. However, it has been demonstrated that the streptococcal cysteine protease SpeB proteolytically inactivates the human cathelicidin LL-37 in vitro. Here we have investigated the expression of LL-37 and its interaction with GAS and SpeB during acute severe soft tissue infections by analyses of patient tissue biopsy specimens. The results showed large amounts of LL-37, both the proform (hCAP18) and the mature peptide, in the tissue. Confocal microscopy identified neutrophils as the main source of the peptide. A distinct colocalization between the bacteria and LL-37 could be noted, and bacterial loads showed positive correlation to the LL-37 levels. Areas with high LL-37 levels coincided with areas with large amounts of SpeB. Confocal microscopy confirmed strong colocalization of GAS, SpeB, and LL-37 at the bacterial surface. Taken together, the findings of this study provide in vivo support of the hypothesis that SpeB-mediated inactivation of LL-37 at the streptococcal surface represents a bacterial resistance mechanism at the infected tissue site in patients with severe GAS tissue infections.

Plasma concentrations of Gas6 (growth arrest specific protein 6) and its soluble tyrosine kinase receptor sAxl in sepsis and systemic inflammatory response syndromes.

IntroductionGas6, the protein product of the growth arrest specific gene 6, is present in human circulation at subnanomolar concentrations. It is secreted by endothelial cells and is important for the activation of endothelium during inflammation. Axl, the tyrosine kinase receptor for Gas6, is also present in endothelium and can be cleaved and released into the circulation. The soluble of form Axl (sAxl), which is present in plasma, can bind Gas6 and inhibit Axl-mediated cell signalling.MethodsWe have developed reproducible and accurate enzyme-linked immunosorbent assays for both Gas6 and sAxl and used them to investigate plasma samples from 70 patients with severe sepsis, 99 patients with sepsis, 42 patients with various infections causing fever but no systemic inflammatory response syndrome (SIRS), 20 patients with SIRS without verified infection, and 100 blood donors that served as controls. Correlations between Gas6 and sAxl concentrations and other commonly used analytes were investigated.ResultsThe patients with severe sepsis, sepsis, infection or SIRS had all increased concentrations of Gas6, approximately double compared to what was found in the controls. The concentrations of sAxl were also increased in the patient groups compared to the controls. Gas6 correlated with C-reactive protein, procalcitonin and interleukin 6, whereas sAxl correlated to bilirubin and procalcitonin.ConclusionsWe can confirm results of earlier studies showing that circulating Gas6 is increased in sepsis and related syndromes. sAxl is increased, but less pronounced than Gas6. The concentrations of Gas6 and sAxl correlate with a number of inflammatory markers, suggesting a role in systemic inflammation.

Antibody orientation at bacterial surfaces is related to invasive infection

Bacterial surface proteins switch the orientation of IgG binding depending on the antibody concentration of their environment.

Decreased plasma concentrations of apolipoprotein M in sepsis and systemic inflammatory response syndromes

IntroductionApolipoprotein M (apoM) is present in 5% of high-density lipoprotein (HDL) particles in plasma. It is a carrier of sphingosine-1-phosphate (S1P), which is important for vascular barrier protection. The aim was to determine the plasma concentrations of apoM during sepsis and systemic inflammatory response syndrome (SIRS) and correlate them to levels of apolipoprotein A-I (apoA1), apolipoprotein B (apoB), HDL-, and low-density lipoprotein (LDL)-cholesterol.MethodsPlasma samples from patients with (1), severe sepsis with shock (n = 26); (2), severe sepsis without shock (n = 44); (3), sepsis (n = 100); (4), infections without SIRS (n = 43); and (5) SIRS without infection (n = 20) were analyzed. The concentrations of apoM, apoA1, and apoB were measured with enzyme-linked immunosorbent assays (ELISAs). Total, HDL-, and LDL-cholesterol concentrations were measured with a commercial HDL/LDL cholesterol test.ResultsApoM concentrations correlated negatively to acute-phase markers. Thus, apoM behaved as a negative acute-phase protein. Decreased values were observed in all patient groups (P < 0.0001), with the most drastic decreases observed in the severely sick patients. ApoM levels correlated strongly to those of apoA1, apoB, HDL, and LDL cholesterol. The HDL and LDL cholesterol levels were low in all patient groups, as compared with controls (P < 0.0001), in particular, HDL cholesterol. ApoA1 and apoB concentrations were low only in the more severely affected patients.ConclusionsDuring sepsis and SIRS, the plasma concentrations of apoM decrease dramatically, the degree of decrease reflecting the severity of the disease. As a carrier for barrier-protective S1P in HDL, the decrease in apoM could contribute to the increased vascular leakage observed in sepsis and SIRS.

Elevated plasma levels of heparin-binding protein in intensive care unit patients with severe sepsis and septic shock

IntroductionRapid detection of, and optimized treatment for, severe sepsis and septic shock is crucial for successful outcome. Heparin-binding protein (HBP), a potent inducer of increased vascular permeability, is a potentially useful biomarker for predicting outcome in patients with severe infections. Our aim was to study the systemic release and dynamics of HBP in the plasma of patients with severe sepsis and septic shock in the ICU.MethodsA prospective study was conducted of two patient cohorts treated in the ICU at Karolinska University Hospital Huddinge in Sweden. A total of 179 patients was included, of whom 151 had sepsis (126 with septic shock and 25 patients with severe sepsis) and 28 a non-septic critical condition. Blood samples were collected at five time points during six days after admission.ResultsHBP levels were significantly higher in the sepsis group as compared to the control group. At admission to the ICU, a plasma HBP concentration of ≥15 ng/mL and/or a HBP (ng/mL)/white blood cell count (109/L) ratio of >2 was found in 87.2% and 50.0% of critically ill patients with sepsis and non-septic illness, respectively. A lactate level of >2.5 mmol/L was detected in 64.9% and 56.0% of the same patient groups. Both in the sepsis group (n = 151) and in the whole group (n = 179), plasma HBP concentrations at admission and in the last measured sample within the 144 hour study period were significantly higher among 28-day non-survivors as compared to survivors and in the sepsis group, an elevated HBP-level at baseline was associated with an increased case-fatality rate at 28 days.ConclusionsPlasma HBP levels were significantly higher in patients with severe sepsis or septic shock compared to patients with a non-septic illness in the ICU. HBP was associated with severity of disease and an elevated HBP at admission was associated with an increased risk of death. HBP that rises over time may identify patients with a deteriorating prognosis. Thus, repeated HBP measurement in the ICU may help monitor treatment and predict outcome in patients with severe infections.

Heparin-binding protein: A diagnostic marker of acute bacterial meningitis*

Background:The early detection of bacterial meningitis is crucial for successful outcome. Heparin-binding protein, a potent inducer of increased vascular permeability, is released from activated neutrophils in severe sepsis. Objective:In this study we investigated whether heparin-binding protein levels in cerebrospinal fluid could be used as a diagnostic marker for acute bacterial meningitis. Design:One prospective and one retrospective patient cohort from two university hospitals in Sweden were analyzed. Setting and Patients:Cerebrospinal fluid samples were collected from 174 patients with suspected central nervous system infection. Thirty-seven patients with acute community-acquired bacterial meningitis, four patients with neurosurgical bacterial meningitis, 29 patients with viral meningitis or encephalitis, seven patients with neuroborreliosis, and 97 control patients were included. Interventions:None. Measurements and Main Results:Cerebrospinal fluid samples were analyzed for the concentrations of heparin-binding protein, lactate, protein, glucose, neutrophils, and mononuclear cells. Heparin-binding protein levels were significantly higher (p < .01) in patients with acute bacterial meningitis (median 376 ng/mL, range 12–858 ng/mL) than in patients with viral central nervous system infection (median 4.7 ng/mL, range 3.0–41 ng/mL) or neuroborreliosis (median 3.6 ng/mL, range 3.2–10 ng/mL) or in control patients with a normal cerebrospinal fluid cell count (median 3.5 ng/mL, range 2.4–8.7 ng/mL). In the prospectively studied group, a heparin-binding protein concentration exceeding 20 ng/mL gave a sensitivity of 100%, a specificity of 99.2%, and positive and negative predictive values of 96.2% and 100%, respectively, in diagnosing acute bacterial meningitis. The area under the receiver-operating characteristic curve for heparin-binding protein was 0.994, which was higher than for the other investigated parameters. Conclusion:Elevated cerebrospinal fluid levels of heparin-binding protein distinguish between patients with acute bacterial meningitis and patients with other central nervous system infections.

An Endotoxin Tolerance Signature Predicts Sepsis and Organ Dysfunction at Initial Clinical Presentation

Background Sepsis involves aberrant immune responses to infection, but the exact nature of this immune dysfunction remains poorly defined. Bacterial endotoxins like lipopolysaccharide (LPS) are potent inducers of inflammation, which has been associated with the pathophysiology of sepsis, but repeated exposure can also induce a suppressive effect known as endotoxin tolerance or cellular reprogramming. It has been proposed that endotoxin tolerance might be associated with the immunosuppressive state that was primarily observed during late-stage sepsis. However, this relationship remains poorly characterised. Here we clarify the underlying mechanisms and timing of immune dysfunction in sepsis. Methods We defined a gene expression signature characteristic of endotoxin tolerance. Gene-set test approaches were used to correlate this signature with early sepsis, both newly and retrospectively analysing microarrays from 593 patients in 11 cohorts. Then we recruited a unique cohort of possible sepsis patients at first clinical presentation in an independent blinded controlled observational study to determine whether this signature was associated with the development of confirmed sepsis and organ dysfunction. Findings All sepsis patients presented an expression profile strongly associated with the endotoxin tolerance signature (p < 0.01; AUC 96.1%). Importantly, this signature further differentiated between suspected sepsis patients who did, or did not, go on to develop confirmed sepsis, and predicted the development of organ dysfunction. Interpretation Our data support an updated model of sepsis pathogenesis in which endotoxin tolerance-mediated immune dysfunction (cellular reprogramming) is present throughout the clinical course of disease and related to disease severity. Thus endotoxin tolerance might offer new insights guiding the development of new therapies and diagnostics for early sepsis.

Treatment of invasive streptococcal infection with a peptide derived from human high-molecular weight kininogen

Sepsis and septic shock remain an important medical problem, emphasizing the need to identify novel therapeutic opportunities. Hypovolemic hypotension, coagulation dysfunction, disturbed microcirculation, and multiorgan failure resulting from vascular leakage are often observed in these severe conditions. In the present study, we find that HKH20, a peptide derived from human high molecular weight kininogen (HK), down-regulates inflammatory reactions caused by Streptococcus pyogenes in a mouse model of sepsis. HK is a component of the pro-inflammatory and pro-coagulant contact system. Activation of the contact system in the bloodstream by S pyogenes leads to massive tissue damage in the lungs of the infected mice, which eventually results in the death of the animals. HKH20 inhibits activation of the contact system and protects mice with invasive S pyogenes infection from lung damage. In combination with clindamycin treatment, the peptide also significantly prolongs the survival of infected mice.