Multi-Omic blood analysis reveals differences in innate inflammatory sensitivity between species

Vertebrates differ greatly in responses to pro-inflammatory agonists such as bacterial lipopolysaccharide (LPS), complicating use of animal models to study human sepsis or inflammatory disorders. We compared transcriptomes of resting and LPS-exposed blood from six LPS-sensitive species (rabbit, pig, sheep, cow, chimpanzee, human) and four LPS-resilient species (mice, rats, baboon, rhesus), as well as plasma proteomes and lipidomes. Unexpectedly, at baseline, sensitive species already had enhanced expression of LPS-responsive genes relative to resilient species. After LPS stimulation, maximally different genes in resilient species included genes that detoxify LPS, diminish bacterial growth, discriminate sepsis from SIRS, and play roles in autophagy and apoptosis. The findings reveal the molecular landscape of species differences in inflammation, and may inform better selection of species for pre-clinical models.

Bifunctional Small Molecules Enhance Neutrophil Activities Against Aspergillus fumigatus in vivo and in vitro

Aspergillosis is difficult to treat and carries a high mortality rate in immunocompromised patients. Neutrophils play a critical role in control of infection but may be diminished in number and function during immunosuppressive therapies. Here, we measure the effect of three bifunctional small molecules that target Aspergillus fumigatus and prime neutrophils to generate a more effective response against the pathogen. The molecules combine two moieties joined by a chemical linker: a targeting moiety (TM) that binds to the surface of the microbial target, and an effector moiety (EM) that interacts with chemoattractant receptors on human neutrophils. We report that the bifunctional compounds enhance the interactions between primary human neutrophils and A. fumigatus in vitro, using three microfluidic assay platforms. The bifunctional compounds significantly enhance the recruitment of neutrophils, increase hyphae killing by neutrophils in a uniform concentration of drug, and decrease hyphal tip growth velocity in the presence of neutrophils compared to the antifungal targeting moiety alone. We validated that the bifunctional compounds are also effective in vivo, using a zebrafish infection model with neutrophils expressing the appropriate EM receptor. We measured significantly increased phagocytosis of A. fumigatus conidia by neutrophils expressing the EM receptor in the presence of the compounds compared to receptor-negative cells. Finally, we demonstrate that treatment with our lead compound significantly improved the antifungal activity of neutrophils from immunosuppressed patients ex vivo. This type of bifunctional compounds strategy may be utilized to redirect the immune system to destroy fungal, bacterial, and viral pathogens.

Haptoglobin improves shock, lung injury, and survival in canine pneumonia

During the last half-century, numerous antiinflammatory agents were tested in dozens of clinical trials and have proven ineffective for treating septic shock. The observation in multiple studies that cell-free hemoglobin (CFH) levels are elevated during clinical sepsis and that the degree of increase correlates with higher mortality suggests an alternative approach. Human haptoglobin binds CFH with high affinity and, therefore, can potentially reduce iron availability and oxidative activity. CFH levels are elevated over approximately 24-48 hours in our antibiotic-treated canine model of S. aureus pneumonia that simulates the cardiovascular abnormalities of human septic shock. In this 96-hour model, resuscitative treatments, mechanical ventilation, sedation, and continuous care are translatable to management in human intensive care units. We found, in this S. aureus pneumonia model inducing septic shock, that commercial human haptoglobin concentrate infusions over 48-hours bind canine CFH, increase CFH clearance, and lower circulating iron. Over the 96-hour study, this treatment was associated with an improved metabolic profile (pH, lactate), less lung injury, reversal of shock, and increased survival. Haptoglobin binding compartmentalized CFH to the intravascular space. This observation, in combination with increasing CFHs clearance, reduced available iron as a potential source of bacterial nutrition while decreasing the ability for CFH and iron to cause extravascular oxidative tissue injury. In contrast, haptoglobin therapy had no measurable antiinflammatory effect on elevations in proinflammatory C-reactive protein and cytokine levels. Haptoglobin therapy enhances normal host defense mechanisms in contrast to previously studied antiinflammatory sepsis therapies, making it a biologically plausible novel approach to treat septic shock.

Different bactericidal and inflammatory activities of human and mouse blood

Mouse models often serve as a selective gate for drugs developed to treat patients with inflammation and sepsis. However, mice are much more resistant than humans to intravenous challenge with LPS, a cell wall component of Gram-negative bacteria. It is common to detect up to 106 CFU/ml of live bacteria in the blood in many mouse models of bacterial challenge but less than 100 CFU/ml of bacteria in the blood of human adults with Gram-negative sepsis. These substantial differences between mice and humans during infections are unexplained, unstudied and usually ignored.

We studied and compared the growth of four encapsulated, clinically relevant strains of Escherichia coli (O4:K54:H5, O16:K1:H6, O18:K1:H7, O25:K5:H1) and Pseudomonas aeruginosa 12.4.4 in fresh human and mouse blood at 37°C for 30, 90 and 180 minutes. We also measured TNF and IL-6 levels in the supernatants, and performed a phagocytosis assay by using fluorescein isothiocyanate-labeled heat-killed bacteria incubated with human and mouse blood followed by flow cytometry. We found that E. coli and P. aeruginosa multiplied in mouse blood and plasma, but that the colony counts of each were decreased in human blood and plasma. More E. coli and P. aeruginosa were phagocytosed by leukocytes in human than those in mouse blood, but this difference reflected larger numbers of neutrophils in human blood than in mouse blood. Large amounts of pro-inflammatory cytokines TNF and IL-6 were detected in human but not in mouse blood after live bacterial inoculation. In conclusion, our results suggest that bacterial killing, phagocytosis, and cytokine induction in the blood compartment of patients with Gram-negative bacteremia may not be well mimicked in mouse models of bacterial challenge.

Endothelial dysfunction inhibits the ability of haptoglobin to prevent hemoglobin-induced hypertension

Intravascular hemolysis produces injury in a variety of human diseases including hemoglobinopathies, malaria, and sepsis. The adverse effects of increased plasma hemoglobin are partly mediated by depletion of nitric oxide (NO) and result in vasoconstriction. Circulating plasma proteins haptoglobin and hemopexin scavenge extracellular hemoglobin and cell-free heme, respectively. The ability of human haptoglobin or hemopexin to inhibit the adverse effects of NO scavenging by circulating murine hemoglobin was tested in C57Bl/6 mice. In healthy awake mice, the systemic hemodynamic effects of intravenous coinfusion of cell-free hemoglobin and exogenous haptoglobin or of cell-free hemoglobin and hemopexin were compared with the hemodynamic effects of infusion of cell-free hemoglobin or control protein (albumin) alone. We also studied the hemodynamic effects of infusing hemoglobin and haptoglobin as well as injecting either hemoglobin or albumin alone in mice fed a high-fat diet (HFD) and in diabetic (db/db) mice. Coinfusion of a 1:1 weight ratio of haptoglobin but not hemopexin with cell-free hemoglobin prevented hemoglobin-induced systemic hypertension in healthy awake mice. In mice fed a HFD and in diabetic mice, coinfusion of haptoglobin mixed with an equal mass of cell-free hemoglobin did not reverse hemoglobin-induced hypertension. Haptoglobin retained cell-free hemoglobin in plasma, but neither haptoglobin nor hemopexin affected the ability of hemoglobin to scavenge NO ex vivo. In conclusion, in healthy C57Bl/6 mice with normal endothelium, coadministration of haptoglobin but not hemopexin with cell-free hemoglobin prevents acute hemoglobin-induced systemic hypertension by compartmentalizing cell-free hemoglobin in plasma. In murine diseases associated with endothelial dysfunction, haptoglobin therapy appears to be insufficient to prevent hemoglobin-induced vasoconstriction.NEW & NOTEWORTHY Coadministraton of haptoglobin but not hemopexin with cell-free hemoglobin prevents hemoglobin-induced systemic hypertension in mice with a normal endothelium. In contrast, treatment with the same amount of haptoglobin is unable to prevent hemoglobin-induced vasoconstriction in mice with hyperlipidemia or diabetes mellitus, disorders that are associated with endothelial dysfunction.

Outer membrane protein A (OmpA), peptidoglycan-associated lipoprotein (PAL), and murein lipoprotein (MLP) are released in experimental Gram-negative sepsis

We previously showed that Escherichia coli bacteria incubated in normal human serum release complexes that contain three conserved Gram-negative bacterial outer membrane proteins (OMPs) and LPS. We have identified the OMPs as outer membrane protein A (OmpA), peptidoglycan-associated lipoprotein (PAL), and murein lipoprotein (MLP). These OMPs are conserved among enteric Gram-negative bacteria and are bound by IgG in antisera raised to heat-killed rough bacteria such as E. coli J5 (J5 IgG). The present experiments were performed to further analyze the release of these OMPs in a rat wound infection model of sepsis. Plasma was collected from thermally injured rats with E. coli O18 sepsis and filtered. LPS was affinity-purified from plasma filtrates using monoclonal antibody specific for the O-polysaccharide side chain of E. coli O18 LPS. Plasma filtrates were also incubated with J5 IgG conjugated to magnetic beads. Affinity-purified samples were analyzed for the OMPs by immunoblotting. OmpA, PAL, and MLP were released into septic rat blood in complexes with LPS. PAL was consistently present in samples affinity-purified using J5 IgG. The results indicate that OmpA, PAL, and MLP are released and circulate in experimental Gram-negative sepsis and suggest that a proportion of released OMPs are tightly associated with LPS.

TALF peptide-immunoglobulin G conjugates that bind lipopolysaccharide

Several peptides mimicking the amino acid sequence of Tachypleus anti-LPS factor (TALF) bind LPS with high affinity and some neutralize LPS in vitro and in vivo (Kloczewiak M., Black K.M., Loiselle P., Cavaillon J-M., Wainwright N., Warren H.S. Synthetic peptides that mimic the binding site of horseshoe crab anti-lipopolysaccharide factor. J Infect Dis 1994; 170: 1490-1497). Two such peptides, TALF29-59 and TALF41-53, were covalently coupled to human IgG via a disulfide bond using the heterobifunctional linker, N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP). The resulting peptide-lgG conjugates contained 4-8 moles peptide per mole IgG and were evaluated for the ability to bind and neutralize LPS. Both conjugates bound LPS in a LPS capture Western blot assay. In a fluid-phase radioimmunoassay, half-maximal binding of 5 μg/ml LPS by many different Escherichia coli strains occurred at 50-100 μg/ml for both conjugates. Coagulation of Limulus amoebocyte lysate was only minimally inhibited by 5 μg/ml of each conjugate. Our data suggest that TALF peptide-lgG conjugates bind LPS with high affinity, but only weakly neutralize LPS. These studies provide an initial step towards the development of peptide-lgG preparations that might be useful for the treatment of Gram-negative sepsis by binding and clearing LPS.

Alterations in Systemic Extracellular Heme and Hemopexin Are Associated With Adverse Clinical Outcomes in Ugandan Children With Severe Malaria

Background. Malaria remains a major cause of global mortality. Extracellular heme, released during malaria-induced hemolysis, mediates a number of pathogenic processes associated with vascular and organ injury. Hemopexin (hpx) facilitates the degradation of extracellular heme. In this study, we explore the hypothesis that dysregulation of the heme-hpx axis is associated with disease severity, acute kidney injury (AKI), and outcome.

Methods. Plasma levels of hemin and hpx (at admission, day 3, and day 14) were assessed in children with severe malaria in Jinja, Uganda.

Results. The ratio of heme to hpx was higher at admission and decreased with recovery (median, 0.043 [interquartile range {IQR}, 0.007–0.239] on day 1, 0.024 [IQR, 0.005–0.126] on day 3, and 0.008 [IQR, 0.002–0.022] on day 14; P < .001). Ratios of heme to hpx at admission were higher in children with as compared to those without severe anemia (median, 0.124 [IQR, 0.024–0.431] vs 0.016 [IQR, 0.003–0.073]; P < .0001), children with as compared to those without respiratory distress (median, 0.063 [IQR, 0.017–0.413] vs 0.020 [IQR, 0.004–0.124]; P < .01), and children with as opposed to those without stage 3 AKI (median, 0.354 [IQR, 0.123–2.481] vs 0.037 [IQR, 0.005–0.172], P < .01). The heme to hpx ratio at admission was associated with 6-month mortality (median, 0.148 [IQR, 0.042–0.500] vs 0.039 [IQR, 0.007–0.172]; P = .012).

Conclusions. The ratio of heme to hpx is associated with disease severity and adverse clinical outcomes in Ugandan children, and dysregulation of the heme axis may contribute to malaria pathogenesis.

Haptoglobin or Hemopexin Therapy Prevents Acute Adverse Effects of Resuscitation After Prolonged Storage of Red Cells

BACKGROUND

Extracellular hemoglobin and cell-free heme are toxic breakdown products of hemolyzed erythrocytes. Mammals synthesize the scavenger proteins haptoglobin and hemopexin, which bind extracellular hemoglobin and heme, respectively. Transfusion of packed red blood cells is a lifesaving therapy for patients with hemorrhagic shock. Because erythrocytes undergo progressive deleterious morphological and biochemical changes during storage, transfusion of packed red blood cells that have been stored for prolonged intervals (SRBCs; stored for 35-40 days in humans or 14 days in mice) increases plasma levels of cell-free hemoglobin and heme. Therefore, in patients with hemorrhagic shock, perfusion-sensitive organs such as the kidneys are challenged not only by hypoperfusion but also by the high concentrations of plasma hemoglobin and heme that are associated with the transfusion of SRBCs.

METHODS

To test whether treatment with exogenous human haptoglobin or hemopexin can ameliorate adverse effects of resuscitation with SRBCs after 2 hours of hemorrhagic shock, mice that received SRBCs were given a coinfusion of haptoglobin, hemopexin, or albumin.

RESULTS

Treatment with haptoglobin or hemopexin but not albumin improved the survival rate and attenuated SRBC-induced inflammation. Treatment with haptoglobin retained free hemoglobin in the plasma and prevented SRBC-induced hemoglobinuria and kidney injury. In mice resuscitated with fresh packed red blood cells, treatment with haptoglobin, hemopexin, or albumin did not cause harmful effects.

CONCLUSIONS

In mice, the adverse effects of transfusion with SRBCs after hemorrhagic shock are ameliorated by treatment with either haptoglobin or hemopexin. Haptoglobin infusion prevents kidney injury associated with high plasma hemoglobin concentrations after resuscitation with SRBCs. Treatment with the naturally occurring human plasma proteins haptoglobin or hemopexin may have beneficial effects in conditions of severe hemolysis after prolonged hypotension.

Identification of CD163 as an antiinflammatory receptor for HMGB1-haptoglobin complexes

Secreted by activated cells or passively released by damaged cells, extracellular HMGB1 is a prototypical damage-associated molecular pattern (DAMP) inflammatory mediator. During the course of developing extracorporeal approaches to treating injury and infection, we inadvertently discovered that haptoglobin, the acute phase protein that binds extracellular hemoglobin and targets cellular uptake through CD163, also binds HMGB1. Haptoglobin-HMGB1 complexes elicit the production of antiinflammatory enzymes (heme oxygenase-1) and cytokines (e.g., IL-10) in WT but not in CD163-deficient macrophages. Genetic disruption of haptoglobin or CD163 expression significantly enhances mortality rates in standardized models of intra-abdominal sepsis in mice. Administration of haptoglobin to WT and to haptoglobin gene-deficient animals confers significant protection. These findings reveal a mechanism for haptoglobin modulation of the inflammatory action of HMGB1, with significant implications for developing experimental strategies targeting HMGB1-dependent inflammatory diseases.

Gut Microbiota-Induced Immunoglobulin G Controls Systemic Infection by Symbiotic Bacteria and Pathogens

The gut microbiota is compartmentalized in the intestinal lumen and induces local immune responses, but it remains unknown whether the gut microbiota can induce systemic response and contribute to systemic immunity. We report that selective gut symbiotic gram-negative bacteria were able to disseminate systemically to induce immunoglobulin G (IgG) response, which primarily targeted gram-negative bacterial antigens and conferred protection against systemic infections by E. coli and Salmonella by directly coating bacteria to promote killing by phagocytes. T cells and Toll-like receptor 4 on B cells were important in the generation of microbiota-specific IgG. We identified murein lipoprotein (MLP), a highly conserved gram-negative outer membrane protein, as a major antigen that induced systemic IgG homeostatically in both mice and humans. Administration of anti-MLP IgG conferred crucial protection against systemic Salmonella infection. Thus, our findings reveal an important function for the gut microbiota in combating systemic infection through the induction of protective IgG.

A Critical Reappraisal of Prolonged Neutropenia as a Risk Factor for Invasive Pulmonary Aspergillosis

Prolonged neutropenia is generally thought to be the major factor for invasive pulmonary aspergillosis (IPA). In the present study, we characterize the frequency, severity, and duration of neutropenia that immediately precedes IPA. Prolonged neutropenia was identified in only one third of all IPA cases and occurred exclusively in hematologic patients.

Microfluidic assay for precise measurements of mouse, rat, and human neutrophil chemotaxis in whole-blood droplets

Animal models of human disease differ in innate immune responses to stress, pathogens, or injury. Precise neutrophil phenotype measurements could facilitate interspecies comparisons. However, such phenotype comparisons could not be performed accurately with the use of current assays, as they require the separation of neutrophils from blood using species-specific protocols, and they introduce distinct artifacts. Here, we report a microfluidic technology that enables robust characterization of neutrophil migratory phenotypes in a manner independent of the donor species and performed directly in a droplet of whole blood. The assay relies on the particular ability of neutrophils to deform actively during chemotaxis through microscale channels that block the advance of other blood cells. Neutrophil migration is measured directly in blood, in the presence of other blood cells and serum factors. Our measurements reveal important differences among migration counts, velocity, and directionality among neutrophils from 2 common mouse strains, rats, and humans.

Purified and Recombinant Hemopexin: Protease Activity and Effect on Neutrophil Chemotaxis

Infusion of the heme-binding protein hemopexin has been proposed as a novel approach to decrease heme-induced inflammation in settings of red blood cell breakdown, but questions have been raised as to possible side effects related to protease activity and inhibition of chemotaxis. We evaluated protease activity and effects on chemotaxis of purified plasma hemopexin obtained from multiple sources as well as a novel recombinant fusion protein Fc-hemopexin. Amidolytic assay was performed to measure the protease activity of several plasma-derived hemopexin and recombinant Fc-hemopexin. Hemopexin was added to the human monocyte culture in the presence of lipopolysaccharides (LPS), and also injected into mice intravenously (i.v.) 30 min before inducing neutrophil migration via intraperitoneal (i.p.) injection of thioglycolate. Control groups received the same amount of albumin. Protease activity varied widely between hemopexins. Recombinant Fc-hemopexin bound heme, inhibited the synergy of heme with LPS on tumor necrosis factor (TNF) production from monocytes, and had minor but detectable protease activity. There was no effect of any hemopexin preparation on chemotaxis, and purified hemopexin did not alter the migration of neutrophils into the peritoneal cavity of mice. Heme and LPS synergistically induced the release of LTB4 from human monocytes, and hemopexin blocked this release, as well as chemotaxis of neutrophils in response to activated monocyte supernatants. These results suggest that hemopexin does not directly affect chemotaxis through protease activity, but may decrease heme-driven chemotaxis and secondary inflammation by attenuating the induction of chemoattractants from monocytes. This property could be beneficial in some settings to control potentially damaging inflammation induced by heme.

Dysregulation of the haem-haemopexin axis is associated with severe malaria in a case-control study of Ugandan children

BACKGROUND

Malaria is associated with haemolysis and the release of plasma haem. Plasma haem can cause endothelial injury and organ dysfunction, and is normally scavenged by haemopexin to limit toxicity. It was hypothesized that dysregulation of the haem-haemopexin pathway contributes to severe and fatal malaria infections.

METHODS

Plasma levels of haemin (oxidized haem), haemopexin, haptoglobin, and haemoglobin were quantified in a case-control study of Ugandan children with Plasmodium falciparum malaria. Levels at presentation were compared in children with uncomplicated malaria (UM; n = 29), severe malarial anaemia (SMA; n = 27) or cerebral malaria (CM; n = 31), and evaluated for utility in predicting fatal (n = 19) vs non-fatal (n = 39) outcomes in severe disease. A causal role for haemopexin was assessed in a pre-clinical model of experimental cerebral malaria (ECM), following disruption of mouse haemopexin gene (hpx). Analysis was done using Kruskall Wallis tests, Mann-Whitney tests, log-rank tests for survival, and repeated measures ANOVA.

RESULTS

In Ugandan children presenting with P. falciparum malaria, haemin levels were higher and haemopexin levels were lower in SMA and CM compared to children with UM (haemin, p < 0.01; haemopexin, p < 0.0001). Among all cases of severe malaria, elevated levels of haemin and cell-free haemoglobin at presentation were associated with subsequent mortality (p < 0.05). Compared to ECM-resistant BALB/c mice, susceptible C57BL/6 mice had lower circulating levels of haemopexin (p < 0.01), and targeted deletion of the haemopexin gene, hpx, resulted in increased mortality compared to their wild type littermates (p < 0.05).

CONCLUSIONS

These data indicate that plasma levels of haemin and haemopexin measured at presentation correlate with malaria severity and levels of haemin and cell-free haemoglobin predict outcome in paediatric severe malaria. Mechanistic studies in the ECM model support a causal role for the haem-haemopexin axis in ECM pathobiology.

VaxCelerate II: rapid development of a self-assembling vaccine for Lassa fever

Development of effective vaccines against emerging infectious diseases (EID) can take as much or more than a decade to progress from pathogen isolation/identification to clinical approval. As a result, conventional approaches fail to produce field-ready vaccines before the EID has spread extensively. Lassa is a prototypical emerging infectious disease endemic to West Africa for which no successful vaccine is available. We established the VaxCelerate Consortium to address the need for more rapid vaccine development by creating a platform capable of generating and pre-clinically testing a new vaccine against specific pathogen targets in less than 120 d A self-assembling vaccine is at the core of the approach. It consists of a fusion protein composed of the immunostimulatory Mycobacterium tuberculosis heat shock protein 70 (MtbHSP70) and the biotin binding protein, avidin. Mixing the resulting protein (MAV) with biotinylated pathogen-specific immunogenic peptides yields a self-assembled vaccine (SAV). To meet the time constraint imposed on this project, we used a distributed R&D model involving experts in the fields of protein engineering and production, bioinformatics, peptide synthesis/design and GMP/GLP manufacturing and testing standards. SAV immunogenicity was first tested using H1N1 influenza specific peptides and the entire VaxCelerate process was then tested in a mock live-fire exercise targeting Lassa fever virus. We demonstrated that the Lassa fever vaccine induced significantly increased class II peptide specific interferon-γ CD4(+) T cell responses in HLA-DR3 transgenic mice compared to peptide or MAV alone controls. We thereby demonstrated that our SAV in combination with a distributed development model may facilitate accelerated regulatory review by using an identical design for each vaccine and by applying safety and efficacy assessment tools that are more relevant to human vaccine responses than current animal models.

Hemopexin in severe inflammation and infection: mouse models and human diseases

Introduction

Cell-free plasma hemoglobin is associated with poor outcome in patients with sepsis. Extracellular hemoglobin and secondarily released heme amplify inflammation in the presence of microbial TLR ligands and/or endogenous mediators. Hemopexin, a plasma protein that binds heme with extraordinary affinity, blocks these effects and has been proposed as a possible treatment approach to decrease inflammation in critically ill patients.

Methods

We studied mouse models of endotoxemia, burn wound infections and peritonitis in order to assess if a repletion strategy for hemopexin might be reasonable. We also measured hemopexin in small numbers of three patient populations that might be logical groups for hemopexin therapy: patients with sepsis and ARDS, patients with severe burns, and premature infants.

Results

Despite severe disease, mean plasma hemopexin levels were increased above baseline in each murine model. However, plasma hemopexin levels were decreased or markedly decreased in many patients in each of the three patient populations.

Conclusions

Potentially different behavior of hemopexin in mice and humans may be important to consider when utilizing murine models to represent acute human inflammatory diseases in which heme plays a role. The findings raise the possibility that decreased hemopexin could result in insufficiently neutralized or cleared heme in some patients with ARDS, burns, or in premature infants who might be candidates to benefit from hemopexin administration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0885-x) contains supplementary material, which is available to authorized users.

Nutritional vitamin D supplementation in dialysis: a randomized trial

BACKGROUND AND OBJECTIVES

Vitamin D (25-hydroxyvitamin D; 25[OH]D) deficiency is common in patients initiating long-term hemodialysis, but the safety and efficacy of nutritional vitamin D supplementation in this population remain uncertain.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This randomized, placebo-controlled, parallel-group multicenter trial compared two doses of ergocalciferol with placebo between October 2009 and March 2013. Hemodialysis patients (n=105) with 25(OH)D levels ≤32 ng/ml from 32 centers in the Northeast United States were randomly assigned to oral ergocalciferol, 50,000 IU weekly (n=36) or monthly (n=33), or placebo (n=36) for a 12-week treatment period. The primary endpoint was the achievement of vitamin D sufficiency (25[OH]D >32 ng/ml) at the end of the 12-week treatment period. Survival was assessed through 1 year.

RESULTS

Baseline characteristics were similar across all arms, with overall mean±SD 25(OH)D levels of 21.9±6.9 ng/ml. At 12 weeks, vitamin D sufficiency (25[OH]D >32 ng/ml) was achieved in 91% (weekly), 66% (monthly), and 35% (placebo) (P<0.001). Mean 25(OH)D was significantly higher in both the weekly (49.8±2.3 ng/ml; P<0.001) and monthly (38.3±2.4 ng/ml; P=0.001) arms compared with placebo (27.4±2.3 ng/ml). Calcium, phosphate, parathyroid hormone levels, and active vitamin D treatment did not differ between groups. All-cause and cause-specific hospitalizations and adverse events were similar between groups during the intervention period. Lower all-cause mortality among ergocalciferol-treated participants was not statistically significant (hazard ratio, 0.28; 95% confidence interval, 0.07 to 1.19).

CONCLUSIONS

Oral ergocalciferol can increase 25(OH)D levels in incident hemodialysis patients without significant alterations in blood calcium, phosphate, or parathyroid hormone during a 12-week period.

Spontaneous neutrophil migration patterns during sepsis after major burns

Finely tuned to respond quickly to infections, neutrophils have amazing abilities to migrate fast and efficiently towards sites of infection and inflammation. Although neutrophils ability to migrate is perturbed in patients after major burns, no correlations have yet been demonstrated between altered migration and higher rate of infections and sepsis in these patients when compared to healthy individuals. To probe if such correlations exist, we designed microfluidic devices to quantify the neutrophil migration phenotype with high precision. Inside these devices, moving neutrophils are confined in channels smaller than the neutrophils and forced to make directional decisions at bifurcations and around posts. We employed these devices to quantify neutrophil migration across 18 independent parameters in 74 blood samples from 13 patients with major burns and 3 healthy subjects. Blinded, retrospective analysis of clinical data and neutrophil migration parameters revealed that neutrophils isolated from blood samples collected during sepsis migrate spontaneously inside the microfluidic channels. The spontaneous neutrophil migration is a unique phenotype, typical for patients with major burns during sepsis and often observed one or two days before the diagnosis of sepsis is confirmed. The spontaneous neutrophil migration phenotype is rare in patients with major burns in the absence of sepsis, and is not encountered in healthy individuals. Our findings warrant further studies of neutrophils and their utility for early diagnosing and monitoring sepsis in patients after major burns.

Strategies to improve drug development for sepsis

Sepsis, a common and potentially fatal systemic illness, is triggered by microbial infection and often leads to impaired function of the lungs, kidneys or other vital organs. Since the early 1980s, a large number of therapeutic agents for the treatment of sepsis have been evaluated in randomized controlled clinical trials. With few exceptions, the results from these trials have been disappointing, and no specific therapeutic agent is currently approved for the treatment of sepsis. To improve upon this dismal record, investigators will need to identify more suitable therapeutic targets, improve their approaches for selecting candidate compounds for clinical development and adopt better designs for clinical trials.

Intestinal alkaline phosphatase promotes gut bacterial growth by reducing the concentration of luminal nucleotide triphosphates

The intestinal microbiota plays a pivotal role in maintaining human health and well-being. Previously, we have shown that mice deficient in the brush-border enzyme intestinal alkaline phosphatase (IAP) suffer from dysbiosis and that oral IAP supplementation normalizes the gut flora. Here we aimed to decipher the molecular mechanism by which IAP promotes bacterial growth. We used an isolated mouse intestinal loop model to directly examine the effect of exogenous IAP on the growth of specific intestinal bacterial species. We studied the effects of various IAP targets on the growth of stool aerobic and anaerobic bacteria as well as on a few specific gut organisms. We determined the effects of ATP and other nucleotides on bacterial growth. Furthermore, we examined the effects of IAP on reversing the inhibitory effects of nucleotides on bacterial growth. We have confirmed that local IAP bioactivity creates a luminal environment that promotes the growth of a wide range of commensal organisms. IAP promotes the growth of stool aerobic and anaerobic bacteria and appears to exert its growth promoting effects by inactivating (dephosphorylating) luminal ATP and other luminal nucleotide triphosphates. We observed that compared with wild-type mice, IAP-knockout mice have more ATP in their luminal contents, and exogenous IAP can reverse the ATP-mediated inhibition of bacterial growth in the isolated intestinal loop. In conclusion, IAP appears to promote the growth of intestinal commensal bacteria by inhibiting the concentration of luminal nucleotide triphosphates.

Intestinal alkaline phosphatase prevents metabolic syndrome in mice

Metabolic syndrome comprises a cluster of related disorders that includes obesity, glucose intolerance, insulin resistance, dyslipidemia, and fatty liver. Recently, gut-derived chronic endotoxemia has been identified as a primary mediator for triggering the low-grade inflammation responsible for the development of metabolic syndrome. In the present study we examined the role of the small intestinal brush-border enzyme, intestinal alkaline phosphatase (IAP), in preventing a high-fat-diet-induced metabolic syndrome in mice. We found that both endogenous and orally supplemented IAP inhibits absorption of endotoxin (lipopolysaccharides) that occurs with dietary fat, and oral IAP supplementation prevents as well as reverses metabolic syndrome. Furthermore, IAP supplementation improves the lipid profile in mice fed a standard, low-fat chow diet. These results point to a potentially unique therapy against metabolic syndrome in at-risk humans.

Intestinal alkaline phosphatase inhibits the proinflammatory nucleotide uridine diphosphate

Uridine diphosphate (UDP) is a proinflammatory nucleotide implicated in inflammatory bowel disease. Intestinal alkaline phosphatase (IAP) is a gut mucosal defense factor capable of inhibiting intestinal inflammation. We used the malachite green assay to show that IAP dephosphorylates UDP. To study the anti-inflammatory effect of IAP, UDP or other proinflammatory ligands (LPS, flagellin, Pam3Cys, or TNF-α) in the presence or absence of IAP were applied to cell cultures, and IL-8 was measured. UDP caused dose-dependent increase in IL-8 release by immune cells and two gut epithelial cell lines, and IAP treatment abrogated IL-8 release. Costimulation with UDP and other inflammatory ligands resulted in a synergistic increase in IL-8 release, which was prevented by IAP treatment. In vivo, UDP in the presence or absence of IAP was instilled into a small intestinal loop model in wild-type and IAP-knockout mice. Luminal contents were applied to cell culture, and cytokine levels were measured in culture supernatant and intestinal tissue. UDP-treated luminal contents induced more inflammation on target cells, with a greater inflammatory response to contents from IAP-KO mice treated with UDP than from WT mice. Additionally, UDP treatment increased TNF-α levels in intestinal tissue of IAP-KO mice, and cotreatment with IAP reduced inflammation to control levels. Taken together, these studies show that IAP prevents inflammation caused by UDP alone and in combination with other ligands, and the anti-inflammatory effect of IAP against UDP persists in mouse small intestine. The benefits of IAP in intestinal disease may be partly due to inhibition of the proinflammatory activity of UDP.

Cerebrospinal fluid proteome of patients with acute Lyme disease

During acute Lyme disease, bacteria can disseminate to the central nervous system (CNS), leading to the development of meningitis and other neurologic symptoms. Here we have analyzed pooled cerebrospinal fluid (CSF) allowing a deep view into the proteome for patients diagnosed with early disseminated Lyme disease and CSF inflammation. Additionally, we analyzed individual patient samples and quantified differences in protein abundance employing label-free quantitative mass spectrometry-based methods. We identified 108 proteins that differ significantly in abundance in patients with acute Lyme disease from controls. Comparison between infected patients and control subjects revealed differences in proteins in the CSF associated with cell death localized to brain synapses and others that likely originate from brain parenchyma.

Prevalence and outcomes of antimicrobial treatment for Staphylococcus aureus bacteremia in outpatients with ESRD

Staphylococcus bacteremia is a common and life-threatening medical emergency, but it is treatable with appropriate antibiotic therapy. To identify opportunities that may reduce morbidity and mortality associated with S. aureus, we analyzed data from 293,094 chronic hemodialysis outpatients to characterize practices of antibiotic selection. In the study population, the overall rate of bacteremia was 15.4 per 100 outpatient-years; the incidence rate for methicillin-sensitive (MSSA) was 2.1 per 100 outpatient-years, and the incidence rate for methicillin-resistant (MRSA) S. aureus was 1.9 per 100 outpatient-years. One week after the collection of the index blood culture, 56.1% of outpatients with MSSA bacteremia were receiving vancomycin, and 16.7% of outpatients with MSSA were receiving cefazolin. Among MSSA-bacteremic patients who did not die or get hospitalized 1 week after blood culture collection, use of cefazolin was associated with a 38% lower risk for hospitalization or death compared with vancomycin (adjusted HR=0.62, 95% CI=0.46-0.84). In conclusion, vancomycin is commonly used to treat MSSA bacteremia in outpatients receiving chronic dialysis, but there may be more risk of treatment failure than observed among those individuals who receive a β-lactam antibiotic such as cefazolin.

Identification of hemopexin as an anti-inflammatory factor that inhibits synergy of hemoglobin with HMGB1 in sterile and infectious inflammation

Hemoglobin is released from lysed RBCs in numerous clinical settings. High mobility group box 1 (HMGB1) is a nuclear and cytosolic DNA-binding protein released from injured cells that has been shown to play an important role in inducing inflammation. Because both of these endogenous molecules are frequently present in sites of necrosis and inflammation, we studied their interaction on the activation of macrophages. We report in this article that hemoglobin and HMGB1 synergize to activate mouse macrophages to release significantly increased proinflammatory cytokines. Addition of microbial ligands that activate through TLR2 or TLR4 resulted in further significant increases, in a "three-way" synergy between endogenous and microbial ligands. The synergy was strongly suppressed by hemopexin (Hx), an endogenous heme-binding plasma protein. The findings suggest that hemoglobin may play an important role in sterile and infectious inflammation, and that endogenous Hx can modulate this response. Administration of Hx may be beneficial in clinical settings characterized by elevated extracellular hemoglobin and HMGB1.

Identification of hemopexin as an anti-inflammatory factor that inhibits hemoglobin synergy with HMGB1 in sterile and infectious inflammation (172.11)

In many clinical settings such as trauma, infections and other hemorrhagic diseases, multiple endogenous substances are released into the extracellular space, including hemoglobin (Hb) from degrading RBC and HMGB1, an intracellular DNA-binding protein that has been shown to be pro-inflammatory, from injured or immune cells. We studied the effects of Hb and HMGB1 on the activation of macrophages. In the supernatant of cultured bone marrow-derived macrophages from C57BL/6 or C3H/HeN mice, significantly increased levels of pro-inflammatory cytokines (TNF and IL-6) were detected when Hb was added with HMGB1 compared to the culture with HMGB1 alone ( P &lt; 0.01), while Hb itself did not induce detectable TNF and IL-6. This synergistic effect was also present in the culture of TLR2 knockout and TLR4 deficient (C3H/HeJ) macrophages. Addition of hemopexin (Hx), an endogenous heme-binding plasma protein, significantly decreased TNF and IL-6 induced by Hb and HMGB1 (P &lt; 0.01). Co-incubation of microbial ligands LPS or Pam3Cys with Hb and HMGB1 in the culture resulted in further dramatic increases of TNF and IL-6 that were also significantly decreased by Hx (P &lt; 0.01). These findings suggest that Hb may play an important role in amplifying sterile as well as infectious inflammation, and that endogenous Hx may play a role in controlling it. Administration of Hx could be a beneficial strategy in clinical settings where extracellular Hb and HMGB1 are both present.

Benchmarking outcomes in the critically injured trauma patient and the effect of implementing standard operating procedures

OBJECTIVE

To determine and compare outcomes with accepted benchmarks in trauma care at 7 academic level I trauma centers in which patients were treated on the basis of a series of standard operating procedures (SOPs).

BACKGROUND

Injury remains the leading cause of death for those younger than 45 years. This study describes the baseline patient characteristics and well-defined outcomes of persons hospitalized in the United States for severe blunt trauma.

METHODS

We followed 1637 trauma patients from 2003 to 2009 up to 28 hospital days using SOPs developed at the onset of the study. An extensive database on patient and injury characteristics, clinical treatment, and outcomes was created. These data were compared with existing trauma benchmarks.

RESULTS

The study patients were critically injured and were in shock. SOP compliance improved 10% to 40% during the study period. Multiple organ failure and mortality rates were 34.8% and 16.7%, respectively. Time to recovery, defined as the time until the patient was free of organ failure for at least 2 consecutive days, was developed as a new outcome measure. There was a reduction in mortality rate in the cohort during the study that cannot be explained by changes in the patient population.

CONCLUSIONS

This study provides the current benchmark and the overall positive effect of implementing SOPs for severely injured patients. Over the course of the study, there were improvements in morbidity and mortality rates and increasing compliance with SOPs. Mortality was surprisingly low, given the degree of injury, and improved over the duration of the study, which correlated with improved SOP compliance.

A genomic storm in critically injured humans

Critical injury in humans induces a genomic storm with simultaneous changes in expression of innate and adaptive immunity genes.

Human survival from injury requires an appropriate inflammatory and immune response. We describe the circulating leukocyte transcriptome after severe trauma and burn injury, as well as in healthy subjects receiving low-dose bacterial endotoxin, and show that these severe stresses produce a global reprioritization affecting >80% of the cellular functions and pathways, a truly unexpected “genomic storm.” In severe blunt trauma, the early leukocyte genomic response is consistent with simultaneously increased expression of genes involved in the systemic inflammatory, innate immune, and compensatory antiinflammatory responses, as well as in the suppression of genes involved in adaptive immunity. Furthermore, complications like nosocomial infections and organ failure are not associated with any genomic evidence of a second hit and differ only in the magnitude and duration of this genomic reprioritization. The similarities in gene expression patterns between different injuries reveal an apparently fundamental human response to severe inflammatory stress, with genomic signatures that are surprisingly far more common than different. Based on these transcriptional data, we propose a new paradigm for the human immunological response to severe injury.

Myocardial ischemia activates an injurious innate immune signaling via cardiac heat shock protein 60 and Toll-like receptor 4

Innate immune response after transient ischemia is the most common cause of myocardial inflammation and may contribute to injury, yet the detailed signaling mechanisms leading to such a response are not well understood. Herein we tested the hypothesis that myocardial ischemia activates interleukin receptor-associated kinase-1 (IRAK-1), a kinase critical for the innate immune signaling such as that of Toll-like receptors (TLRs), via a mechanism that involves heat shock proteins (HSPs) and TLRs. Coronary artery occlusion induced a rapid myocardial IRAK-1 activation within 30 min in wild-type (WT), TLR2(-/-), or Trif(-/-) mice, but not in TLR4(def) or MyD88(-/-) mice. HSP60 protein was markedly increased in serum or in perfusate of isolated heart following ischemia/reperfusion (I/R). In vitro, recombinant HSP60 induced IRAK-1 activation in cells derived from WT, TLR2(-/-), or Trif(-/-) mice, but not from TLR4(def) or MyD88(-/-) mice. Both myocardial ischemia- and HSP60-induced IRAK-1 activation was abolished by anti-HSP60 antibody. Moreover, HSP60 treatment of cardiomyocytes (CMs) led to marked activation of caspase-8 and -3, but not -9. Expression of dominant-negative mutant of Fas-associated death domain protein or a caspase-8 inhibitor completely blocked HSP60-induced caspase-8 activation, suggesting that HSP60 likely activates an apoptotic program via the death-receptor pathway. In vivo, I/R-induced myocardial apoptosis and cytokine expression were significantly attenuated in TLR4(def) mice or in WT mice treated with anti-HSP60 antibody compared with WT controls. Taken together, the current study demonstrates that myocardial ischemia activates an innate immune signaling via HSP60 and TLR4, which plays an important role in mediating apoptosis and inflammation during I/R.

A role for intestinal alkaline phosphatase in the maintenance of local gut immunity

BACKGROUND AND AIMS

Intestinal alkaline phosphatase (IAP) is a gut mucosal defense factor known to dephosphorylate lipopolysaccharide (LPS); however, the role of IAP in the gut response to luminal bacteria remains poorly defined. We investigated immune responses of wild-type (WT) and IAP-knockout (IAP-KO) mice to LPS and Salmonella typhimurium challenges.

METHODS

Cryostat sectioning and standard indirect immunohistochemical staining for major histocompatibility complex (MHC) class II molecules were performed on liver tissue from WT and IAP-KO mice. WT and IAP-KO mice were orally gavaged with S. typhimurium; bacterial translocation to mesenteric nodes, liver, and spleen was determined by tissue homogenization and plating. In other experiments, WT and IAP-KO mice received intraperitoneal injections of LPS, with subsequent quantification of complete blood counts and serum interleukin (IL)-6 by enzyme-linked immunosorbent assay (ELISA). WT and IAP-KO whole blood were plated and stimulated with LPS and Pam-3-Cys, followed by cytokine assays.

RESULTS

Immunohistologic liver examinations showed increased expression of MHC class II molecules in IAP-KO mice. Following S. typhimurium challenge, WT mice appeared moribund compared with IAP-KO mice, with increased bacterial translocation. WT mice had >50% decrease (P<.005) in platelets and 1.8-fold (P<.05) increased serum IL-6 compared with IAP-KO mice in response to LPS injections. IAP-KO whole-blood stimulation with LPS and Pam-3-Cys resulted in increased IL-6 and tumor necrosis factor (TNF)-alpha secretion compared with WT.

CONCLUSIONS

IAP-KO mice exhibit characteristics consistent with local LPS tolerance. Whole-blood response of IAP-KO mice did not reflect systemic tolerance. These data suggest that IAP is a local immunomodulating factor, perhaps regulating LPS-toll-like receptor 4 (TLR4) interaction between commensal microflora and intestinal epithelium.

Intestinal alkaline phosphatase has beneficial effects in mouse models of chronic colitis

BACKGROUND

The brush border enzyme intestinal alkaline phosphatase (IAP) functions as a gut mucosal defense factor and is protective against dextran sulfate sodium (DSS)-induced acute injury in rats. The present study evaluated the potential therapeutic role for orally administered calf IAP (cIAP) in two independent mouse models of chronic colitis: 1) DSS-induced chronic colitis, and 2) chronic spontaneous colitis in Wiskott-Aldrich Syndrome protein (WASP)-deficient (knockout) mice that is accelerated by irradiation.

METHODS

The wildtype (WT) and IAP knockout (IAP-KO) mice received four cycles of 2% DSS ad libitum for 7 days. Each cycle was followed by a 7-day DSS-free interval during which mice received either cIAP or vehicle in the drinking water. The WASP-KO mice received either vehicle or cIAP for 6 weeks beginning on the day of irradiation.

RESULTS

Microscopic colitis scores of DSS-treated IAP-KO mice were higher than DSS-treated WT mice (52±3.8 versus 28.8±6.6, respectively, P<0.0001). cIAP treatment attenuated the disease in both groups (KO=30.7±6.01, WT=18.7±5.0, P<0.05). In irradiated WASP-KO mice cIAP also attenuated colitis compared to control groups (3.3±0.52 versus 6.2±0.34, respectively, P<0.001). Tissue myeloperoxidase activity and proinflammatory cytokines were significantly decreased by cIAP treatment.

CONCLUSIONS

Endogenous IAP appears to play a role in protecting the host against chronic colitis. Orally administered cIAP exerts a protective effect in two independent mouse models of chronic colitis and may represent a novel therapy for human IBD.

Identification and interpretation of longitudinal gene expression changes in trauma

RATIONALE

The relationship between leukocyte gene expression and recovery of respiratory function after injury may provide information on the etiology of multiple organ dysfunction.

OBJECTIVES

To find a list of genes for which expression after injury predicts respiratory recovery, and to identify which networks and pathways characterize these genes.

METHODS

Blood was sampled at 12 hours and at 1, 4, 7, 21 and 28 days from 147 patients who had been admitted to the hospital after blunt trauma. Leukocyte gene expression was measured using Affymetrix oligonucleotide arrays. A linear model, fit to each probe-set expression value, was used to impute the gene expression trajectory over the entire follow-up period. The proportional hazards model score test was used to calculate the statistical significance of each probe-set trajectory in predicting respiratory recovery. A list of genes was determined such that the expected proportion of false positive results was less than 10%. These genes were compared to the Gene Ontology for 'response to stimulus' and, using Ingenuity software, were mapped into networks and pathways.

MEASUREMENTS AND MAIN RESULTS

The median time to respiratory recovery was 6 days. There were 170 probe-sets representing 135 genes that were found to be related to respiratory recovery. These genes could be mapped to nine networks. Two known pathways that were activated were antigen processing and presentation and JAK-signaling.

CONCLUSIONS

The examination of the relationship of gene expression over time with a patient's clinical course can provide information which may be useful in determining the mechanism of recovery or lack of recovery after severe injury.

Intestinal alkaline phosphatase preserves the normal homeostasis of gut microbiota

BACKGROUND AND AIMS

The intestinal microbiota plays a critical role in maintaining human health; however, the mechanisms governing the normal homeostatic number and composition of these microbes are largely unknown. Previously it was shown that intestinal alkaline phosphatase (IAP), a small intestinal brush border enzyme, functions as a gut mucosal defence factor limiting the translocation of gut bacteria to mesenteric lymph nodes. In this study the role of IAP in the preservation of the normal homeostasis of the gut microbiota was investigated.

METHODS

Bacterial culture was performed in aerobic and anaerobic conditions to quantify the number of bacteria in the stools of wild-type (WT) and IAP knockout (IAP-KO) C57BL/6 mice. Terminal restriction fragment length polymorphism, phylogenetic analyses and quantitative real-time PCR of subphylum-specific bacterial 16S rRNA genes were used to determine the compositional profiles of microbiotas. Oral supplementation of calf IAP (cIAP) was used to determine its effects on the recovery of commensal gut microbiota after antibiotic treatment and also on the colonisation of pathogenic bacteria.

RESULTS

IAP-KO mice had dramatically fewer and also different types of aerobic and anaerobic microbes in their stools compared with WT mice. Oral supplementation of IAP favoured the growth of commensal bacteria, enhanced restoration of gut microbiota lost due to antibiotic treatment and inhibited the growth of a pathogenic bacterium (Salmonella typhimurium).

CONCLUSIONS

IAP is involved in the maintenance of normal gut microbial homeostasis and may have therapeutic potential against dysbiosis and pathogenic infections.

Synergistic inflammation is induced by blood degradation products with microbial Toll-like receptor agonists and is blocked by hemopexin

Detection of microbial components by immune cells via Toll-like receptors (TLRs) with subsequent induction of inflammation is essential for host defense. However, an overactive immune response can cause tissue damage and sepsis. The endogenous molecule hemoglobin and its derivative heme are often released into tissue compartments where there is infection in the presence of degrading blood. We found that hemoglobin synergizes with multiple TLR agonists to induce high levels of tumor necrosis factor and interleukin-6 from macrophages and that this synergy is independent of TLR4 and MyD88. In contrast, heme synergized with some but not all TLR agonists studied. Furthermore, the synergy of both hemoglobin and heme with lipopolysaccharide was suppressed by hemopexin, a plasma heme-binding protein. These studies suggest that hemoglobin and heme may substantially contribute to microbe-induced inflammation when bacterial or viral infection coexists with blood degradation and that hemopexin may play a role in controlling inflammation in such settings.

Identification of specific targets for the gut mucosal defense factor intestinal alkaline phosphatase

Intestinal alkaline phosphatase (IAP) is a small intestinal brush border enzyme that has been shown to function as a gut mucosal defense factor, but its precise mechanism of action remains unclear. We investigated the effects of IAP on specific bacteria and bacterial components to determine its molecular targets. Purulent fluid from a cecal ligation and puncture model, specific live and heat-killed bacteria (Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes), and a variety of proinflammatory ligands (LPS, CpG DNA, Pam-3-Cys, flagellin, and TNF) were incubated with or without calf IAP (cIAP). Phosphate release was determined by using a malachite green assay. The various fluids were applied to target cells (THP-1, parent HT-29, and IAP-expressing HT-29 cells) and IL-8 secretion measured by ELISA. cIAP inhibited IL-8 induction by purulent fluid in THP-1 cells by >35% (P < 0.005). HT29-IAP cells had a reduced IL-8 response specifically to gram-negative bacteria; >90% reduction compared with parent cells (P < 0.005). cIAP had no effect on live bacteria but attenuated IL-8 induction by heat-killed bacteria by >40% (P < 0.005). cIAP exposure to LPS and CpG DNA caused phosphate release and reduced IL-8 in cell culture by >50% (P < 0.005). Flagellin exposure to cIAP also resulted in reduced IL-8 secretion by >40% (P < 0.005). In contrast, cIAP had no effect on TNF or Pam-3-Cys. The mechanism of IAP action appears to be through dephosphorylation of specific bacterial components, including LPS, CpG DNA, and flagellin, and not on live bacteria themselves. IAP likely targets these bacterially derived molecules in its role as a gut mucosal defense factor.

Resilience to bacterial infection: difference between species could be due to proteins in serum

Vertebrates vary in resistance and resilience to infectious diseases, and the mechanisms that regulate the trade-off between these often opposing protective processes are not well understood. Variability in the sensitivity of species to the induction of damaging inflammation in response to equivalent pathogen loads (resilience) complicates the use of animal models that reflect human disease. We found that induction of proinflammatory cytokines from macrophages in response to inflammatory stimuli in vitro is regulated by proteins in the sera of species in inverse proportion to their in vivo resilience to lethal doses of bacterial lipopolysaccharide over a range of 10,000-fold. This finding suggests that proteins in serum rather than intrinsic cellular differences may play a role in regulating variations in resilience to microbe-associated molecular patterns between species. The involvement of circulating proteins as key molecules raises hope that the process might be manipulated to create better animal models and potentially new drug targets.

Hemopexin down-regulates LPS-induced proinflammatory cytokines from macrophages

Detection of LPS in tissues is an integral component of innate immunity that acts to protect against invasion by Gram-negative bacteria. Plasma down-regulates LPS-induced cytokine production from macrophages, thereby limiting systemic inflammation in blood and distant tissues. To identify the protein(s) involved in this process, we used classical biochemical chromatographic techniques to identify fractions of mouse sera that suppress LPS-induced TNF from bone marrow-derived macrophages (BMDMs). Fractionation yielded microgram quantities of a protein that was identified by MS to be hemopexin (Hx). Mouse Hx purified on hemin-agarose beads and rhHx decreased the production of cytokines from BMDMs and peritoneal macrophages induced by LPS. Preincubation of LPS with Hx did not affect the activity of LPS on LAL, whereas preincubation of Hx with macrophages followed by washing resulted in decreased activity of these cells in response to LPS, suggesting that Hx acts on macrophages rather than LPS. Heme-free Hx did not stimulate HO-1 in the macrophages. Purified Hx also decreased TNF and IL-6 from macrophages induced by the synthetic TLR2 agonist Pam3Cys. Our data suggest that Hx, which is an acute-phase protein that increases during inflammation, limits TLR4 and TLR2 agonist-induced macrophage cytokine production directly through a mechanism distinct from HO-1.

A genomic score prognostic of outcome in trauma patients

Traumatic injuries frequently lead to infection, organ failure, and death. Health care providers rely on several injury scoring systems to quantify the extent of injury and to help predict clinical outcome. Physiological, anatomical, and clinical laboratory analytic scoring systems (Acute Physiology and Chronic Health Evaluation [APACHE], Injury Severity Score [ISS]) are utilized, with limited success, to predict outcome following injury. The recent development of techniques for measuring the expression level of all of a person's genes simultaneously may make it possible to develop an injury scoring system based on the degree of gene activation. We hypothesized that a peripheral blood leukocyte gene expression score could predict outcome, including multiple organ failure, following severe blunt trauma. To test such a scoring system, we measured gene expression of peripheral blood leukocytes from patients within 12 h of traumatic injury. cRNA derived from whole blood leukocytes obtained within 12 h of injury provided gene expression data for the entire genome that were used to create a composite gene expression score for each patient. Total blood leukocytes were chosen because they are active during inflammation, which is reflective of poor outcome. The gene expression score combines the activation levels of all the genes into a single number which compares the patient's gene expression to the average gene expression in uninjured volunteers. Expression profiles from healthy volunteers were averaged to create a reference gene expression profile which was used to compute a difference from reference (DFR) score for each patient. This score described the overall genomic response of patients within the first 12 h following severe blunt trauma. Regression models were used to compare the association of the DFR, APACHE, and ISS scores with outcome. We hypothesized that patients with a total gene response more different from uninjured volunteers would tend to have poorer outcome than those more similar. Our data show that for measures of poor outcome, such as infections, organ failures, and length of hospital stay, this is correct. DFR scores were associated significantly with adverse outcome, including multiple organ failure, duration of ventilation, length of hospital stay, and infection rate. The association remained significant after adjustment for injury severity as measured by APACHE or ISS. A single score representing changes in gene expression in peripheral blood leukocytes within hours of severe blunt injury is associated with adverse clinical outcomes that develop later in the hospital course. Assessment of genome-wide gene expression provides useful clinical information that is different from that provided by currently utilized anatomic or physiologic scores.

Passive immunization to outer membrane proteins MLP and PAL does not protect mice from sepsis

Multiple older studies report that immunoglobulin directed to rough mutant bacteria, such as E. coli J5, provides broad protection against challenge with heterologous strains of Gram-negative bacteria. This protection was initially believed to occur through binding of immunoglobulin to bacterial lipopolysaccharide (LPS). However, hundreds of millions of dollars have been invested in attempting to develop clinically-effective anti-LPS monoclonal antibodies without success, and no study has shown that IgG from this antiserum binds LPS. Identification of the protective mechanism would facilitate development of broadly protective human monoclonal antibodies for treating sepsis. IgG from this antiserum binds 2 bacterial outer membrane proteins: murein lipoprotein (MLP) and peptidoglycan-associated lipoprotein (PAL). Both of these outer membrane proteins are highly conserved, have lipid domains that are anchored in the bacterial membrane, are shed from bacteria in blebs together with LPS, and activate cells through Toll-like receptor 2. Our goal in the current work was to determine if passive immunization directed to MLP and PAL protects mice from Gram-negative sepsis. Neither monoclonal nor polyclonal IgG directed to MLP or PAL conferred survival protection in 3 different models of sepsis: cecal ligation and puncture, an infected burn model, and an infected fibrin clot model mimicking peritonitis. Our results are not supportive of the hypothesis that either anti-MLP or anti-PAL IgG are the protective antibodies in the previously described anti-rough mutant bacterial antisera. These studies suggest that a different mechanism of protection is involved.

MyD88-dependent and MyD88-independent pathways in synergy, priming, and tolerance between TLR agonists

TLRs sense components of microorganisms and are critical host mediators of inflammation during infection. Different TLR agonists can profoundly alter inflammatory effects of one another, and studies suggest that the sequence of exposure to TLR agonists may importantly impact on responses during infection. We tested the hypothesis that synergy, priming, and tolerance between TLR agonists follow a pattern that can be predicted based on differential engagement of the MyD88-dependent (D) and the MyD88-independent (I) intracellular signaling pathways. Inflammatory effects of combinations of D and I pathway agonists were quantified in vivo and in vitro. Experiments used several D-specific agonists, an I-specific agonist (poly(I:C)), and LPS, which acts through both the D and I pathways. D-specific agonists included: peptidoglycan-associated lipoprotein, Pam3Cys, flagellin, and CpG DNA, which act through TLR2 (peptidoglycan-associated lipoprotein and Pam3Cys), TLR5, and TLR9, respectively. D and I agonists were markedly synergistic in inducing cytokine production in vivo in mice. All of the D-specific agonists were synergistic with poly(I:C) in vitro in inducing TNF and IL-6 production by mouse bone marrow-derived macrophages. Pretreatment of bone marrow-derived macrophages with poly(I:C) led to a primed response to subsequent D-specific agonists and vice versa, as indicated by increased cytokine production, and increased NF-kappaB translocation. Pretreatment with a D-specific agonist augmented LPS-induced IFN-beta production. All D-specific agonists induced tolerance to one another. Thus, under the conditions studied here, simultaneous and sequential activation of both the D and I pathways causes synergy and priming, respectively, and tolerance is induced by agonists that act through the same pathway.

Passive immunization to outer membrane proteins MLP and PAL does not protect mice from sepsis

Multiple older studies report that immunoglobulin directed to rough mutant bacteria, such as E. coli J5, provides broad protection against challenge with heterologous strains of Gram-negative bacteria. This protection was initially believed to occur through binding of immunoglobulin to bacterial lipopolysaccharide (LPS). However, hundreds of millions of dollars have been invested in attempting to develop clinically-effective anti-LPS monoclonal antibodies without success, and no study has shown that IgG from this antiserum binds LPS. Identification of the protective mechanism would facilitate development of broadly protective human monoclonal antibodies for treating sepsis. IgG from this antiserum binds 2 bacterial outer membrane proteins: murein lipoprotein (MLP) and peptidoglycan-associated lipoprotein (PAL). Both of these outer membrane proteins are highly conserved, have lipid domains that are anchored in the bacterial membrane, are shed from bacteria in blebs together with LPS, and activate cells through Toll-like receptor 2. Our goal in the current work was to determine if passive immunization directed to MLP and PAL protects mice from Gram-negative sepsis. Neither monoclonal nor polyclonal IgG directed to MLP or PAL conferred survival protection in 3 different models of sepsis: cecal ligation and puncture, an infected burn model, and an infected fibrin clot model mimicking peritonitis. Our results are not supportive of the hypothesis that either anti-MLP or anti-PAL IgG are the protective antibodies in the previously described anti-rough mutant bacterial antisera. These studies suggest that a different mechanism of protection is involved.