Prospective Validation of a Transcriptomic Metric in Severe Trauma

Infusion of young donor plasma components in older patients modifies the immune and inflammatory response to surgical tissue injury: a randomized clinical trial

BACKGROUND

Preclinical evidence suggests that young plasma has beneficial effects on multiple organ systems in aged mice. Whether young plasma exerts beneficial effects in an aging human population remains highly controversial. Despite lacking data, young donor plasma infusions have been promoted for age-related conditions. Given the preclinical evidence that young plasma exerts beneficial effects by attenuating inflammation, this study examined whether administering a young plasma protein fraction to an elderly population would exert anti-inflammatory and immune modulating effects in humans, using surgery as a tissue injury model.

METHODS

This double-blind, placebo-controlled study enrolled and randomized 38 patients undergoing major joint replacement surgery. Patients received four separate infusions of a plasma protein fraction derived from young donors, or placebo one day before surgery, before and after surgery on the day of surgery, and one day after surgery. Blood specimens for proteomic and immunological analyses were collected before each infusion. Based on the high-content assessment of circulating plasma proteins with single-cell analyses of peripheral immune cells, proteomic signatures and cell-type-specific signaling responses that separated the treatment groups were derived with regression models.

RESULTS

Elastic net regression models revealed that administration a young plasma protein fraction significantly altered the proteomic (AUC = 0.796, p = 0.002) and the cellular immune response (AUC 0.904, p < 0.001) to surgical trauma resulting in signaling pathway- and cell type-specific anti-inflammatory immune modulation. Affected proteomic pathways regulating inflammation included JAK-STAT, NF-kappa B, and MAPK (p < 0.001). These findings were confirmed at the cellular level as the MAPK and JAK/STAT signaling responses were diminished and IkB, the negative regulator of NFkB, was elevated in adaptive immune cells.

CONCLUSION

Reported findings provide a first proof of principle in humans that a young plasma protein fraction actively regulates inflammatory and immune responses in an elderly population. They provide a solid rationale for elucidating active principles in young plasma that may be of therapeutic benefits for a range of age-related pathologies.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03981419.

International multi-cohort analysis identifies novel framework for quantifying immune dysregulation in critical illness: results of the SUBSPACE consortium

Progress in the management of critical care syndromes such as sepsis, Acute Respiratory Distress Syndrome (ARDS), and trauma has slowed over the last two decades, limited by the inherent heterogeneity within syndromic illnesses. Numerous immune endotypes have been proposed in sepsis and critical care, however the overlap of the endotypes is unclear, limiting clinical translation. The SUBSPACE consortium is an international consortium that aims to advance precision medicine through the sharing of transcriptomic data. By evaluating the overlap of existing immune endotypes in sepsis across over 6,000 samples, we developed cell-type specific signatures to quantify dysregulation in these immune compartments. Myeloid and lymphoid dysregulation were associated with disease severity and mortality across all cohorts. This dysregulation was not only observed in sepsis but also in ARDS, trauma, and burn patients, indicating a conserved mechanism across various critical illness syndromes. Moreover, analysis of randomized controlled trial data revealed that myeloid and lymphoid dysregulation is linked to differential mortality in patients treated with anakinra or corticosteroids, underscoring its prognostic and therapeutic significance. In conclusion, this novel immunology-based framework for quantifying cellular compartment dysregulation offers a valuable tool for prognosis and therapeutic decision-making in critical illness.

Multiple organ failure: What you need to know

ABSTRACT

Multiple organ failure (MOF) remains a significant challenge for the acute care surgeon, often leading to poor patient outcomes. This comprehensive review explores the etiology, pathophysiology, clinical presentation, diagnosis, management strategies, prognosis, and prevention strategies associated with MOF and chronic critical illness. Understanding the intricate etiology and pathophysiology of MOF and chronic critical illness is essential for effectively managing these syndromes and developing targeted treatment strategies aimed at mitigating the underlying inflammatory, immune, and microvascular disturbances, in order to redirect patients onto a trajectory of recovery.

The injured monocyte: The link to chronic critical illness and mortality following injury

BACKGROUND

This study aimed to understand the altered innate immune response in severely injured patients leading to chronic critical illness (CCI). Specifically, it focused on characterizing the monocyte populations and their correlation with CCI development and long-term complications.

METHODS

Over a 3-year period, we monitored patients with severe injuries for up to 1-year postinjury. Chronic critical illness was defined as an ICU stay exceeding 14 days with persistent organ failure. Blood samples were collected on Days 1 and 5 for monocyte phenotypic expression analysis using cytometry by time flight. The monocyte subpopulations studied were classical (CL), intermediate (INT), and nonclassical (NC), along with cell surface receptor expression and activation.

RESULTS

Out of 80 enrolled patients, 26 (32.5%) developed CCI. Patients with CCI had more severe injuries (Injury Severity Score, 32.4 + 5.2 vs. 29.6 + 4.1, p = 0.01) and received a higher number of red blood cells (8.9 + 4.1 vs. 4.7 + 3.8 units, p < 0.01) compared with those without CCI. In patients with CCI, the NC monocytes were significantly reduced by over twofold early, and significantly increased later, compared with those without CCI. Moreover, significant changes in intracellular cytokine expression and cell receptors were observed within each monocyte subpopulation in patients with CCI, indicating an increased proinflammatory phenotype but decreased phagocytic capacity and antigen presentation. The development of CCI and the presence of this unique monocyte phenotype were associated with a significantly increased risk of infection, discharge to a long-term care facility, and 1-year mortality of 27%.

CONCLUSION

Development of CCI following severe injury is associated with significant long-term morbidity and unacceptably high mortality. The altered NC phenotype with reduced phagocytic capacity and antigen presentation in patients developing CCI after severe injury is appears partially responsible. Early identification of this unique phenotype may help predict and treat patients at risk for CCI, leading to improved outcomes.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level III.

Utilizing predictive machine-learning modelling unveils feature-based risk assessment system for hyperinflammatory patterns and infectious outcomes in polytrauma

Purpose

Earlier research has identified several potentially predictive features including biomarkers associated with trauma, which can be used to assess the risk for harmful outcomes of polytraumatized patients. These features encompass various aspects such as the nature and severity of the injury, accompanying health conditions, immune and inflammatory markers, and blood parameters linked to organ functioning, however their applicability is limited. Numerous indicators relevant to the patients` outcome are routinely gathered in the intensive care unit (ICU) and recorded in electronic medical records, rendering them suitable predictors for risk assessment of polytraumatized patients.

Methods

317 polytraumatized patients were included, and the influence of 29 clinical and biological features on the complication patterns for systemic inflammatory response syndrome (SIRS), pneumonia and sepsis were analyzed with a machine learning workflow including clustering, classification and explainability using SHapley Additive exPlanations (SHAP) values. The predictive ability of the analyzed features within three days after admission to the hospital were compared based on patient-specific outcomes using receiver-operating characteristics.

Results

A correlation and clustering analysis revealed that distinct patterns of injury and biomarker patterns were observed for the major complication classes. A k-means clustering suggested four different clusters based on the major complications SIRS, pneumonia and sepsis as well as a patient subgroup that developed no complications. For classification of the outcome groups with no complications, pneumonia and sepsis based on boosting ensemble classification, 90% were correctly classified as low-risk group (no complications). For the high-risk groups associated with development of pneumonia and sepsis, 80% of the patients were correctly identified. The explainability analysis with SHAP values identified the top-ranking features that had the largest impact on the development of adverse outcome patterns. For both investigated risk scenarios (infectious complications and long ICU stay) the most important features are SOFA score, Glasgow Coma Scale, lactate, GGT and hemoglobin blood concentration.

Conclusion

The machine learning-based identification of prognostic feature patterns in patients with traumatic injuries may improve tailoring personalized treatment modalities to mitigate the adverse outcomes in high-risk patient clusters.

The persistent inflammation, immunosuppression, and catabolism syndrome 10 years later

With the implementation of new intensive care unit (ICU) therapies in the 1970s, multiple organ failure (MOF) emerged as a fulminant inflammatory phenotype leading to early ICU death. Over the ensuing decades, with fundamental advances in care, this syndrome has evolved into a lingering phenotype of chronic critical illness (CCI) leading to indolent late post-hospital discharge death. In 2012, the University of Florida (UF) Sepsis Critical Illness Research Center (SCIRC) coined the term Persistent Inflammation, Immunosuppression, and Catabolism Syndrome (PICS) to provide a mechanistic framework to study CCI in surgical patients. This was followed by a decade of research into PICS-CCI in surgical ICU patients in order to define the epidemiology, dysregulated immunity, and long-term outcomes after sepsis. Other focused studies were performed in trauma ICU patients and emergency department sepsis patients. Early deaths were surprisingly low (4%); 63% experienced rapid recovery. Unfortunately, 33% progressed to CCI, of which 79% had a poor post-discharge disposition and 41% were dead within one year. These patients had biomarker evidence of PICS, and these biomarkers enhanced clinical prediction models for dismal one-year outcomes. Emergency myelopoiesis appears to play a central role in the observed persistent immune dysregulation that characterizes PICS-CCI. Older patients were especially vulnerable. Disturbingly, over half of the older CCI patients were dead within one year and older CCI survivors remained severely disabled. Although CCI is less frequent (20%) after major trauma, PICS appears to be a valid concept. This review will specifically detail the epidemiology of CCI, PICS biomarkers, effect of site of infection, acute kidney injury, effect on older patients, dysfunctional high-density lipoproteins, sarcopenia/cachexia, emergency myelopoiesis, dysregulated erythropoiesis, and potential therapeutic interventions.

A review of UF SCIRC’s research efforts characterizing CCI, PICS biomarkers, effect of site of infection, acute kidney injury, effects on older patients, dysfunctional high-density lipoproteins, sarcopenia/cachexia, emergency myelopoiesis, and dysregulated erythropoiesis.

Lipidomic signatures align with inflammatory patterns and outcomes in critical illness

Alterations in lipid metabolism have the potential to be markers as well as drivers of pathobiology of acute critical illness. Here, we took advantage of the temporal precision offered by trauma as a common cause of critical illness to identify the dynamic patterns in the circulating lipidome in critically ill humans. The major findings include an early loss of all classes of circulating lipids followed by a delayed and selective lipogenesis in patients destined to remain critically ill. The previously reported survival benefit of early thawed plasma administration was associated with preserved lipid levels that related to favorable changes in coagulation and inflammation biomarkers in causal modelling. Phosphatidylethanolamines (PE) were elevated in patients with persistent critical illness and PE levels were prognostic for worse outcomes not only in trauma but also severe COVID-19 patients. Here we show selective rise in systemic PE as a common prognostic feature of critical illness.

Multi-Omic Admission-Based Prognostic Biomarkers Identified by Machine Learning Algorithms Predict Patient Recovery and 30-Day Survival in Trauma Patients

Admission-based circulating biomarkers for the prediction of outcomes in trauma patients could be useful for clinical decision support. It is unknown which molecular classes of biomolecules can contribute biomarkers to predictive modeling. Here, we analyzed a large multi-omic database of over 8500 markers (proteomics, metabolomics, and lipidomics) to identify prognostic biomarkers in the circulating compartment for adverse outcomes, including mortality and slow recovery, in severely injured trauma patients. Admission plasma samples from patients (n = 129) enrolled in the Prehospital Air Medical Plasma (PAMPer) trial were analyzed using mass spectrometry (metabolomics and lipidomics) and aptamer-based (proteomics) assays. Biomarkers were selected via Least Absolute Shrinkage and Selection Operator (LASSO) regression modeling and machine learning analysis. A combination of five proteins from the proteomic layer was best at discriminating resolvers from non-resolvers from critical illness with an Area Under the Receiver Operating Characteristic curve (AUC) of 0.74, while 26 multi-omic features predicted 30-day survival with an AUC of 0.77. Patients with traumatic brain injury as part of their injury complex had a unique subset of features that predicted 30-day survival. Our findings indicate that multi-omic analyses can identify novel admission-based prognostic biomarkers for outcomes in trauma patients. Unique biomarker discovery also has the potential to provide biologic insights.

Chronic Critical Illness Elicits a Unique Circulating Leukocyte Transcriptome in Sepsis Survivors

Surgical sepsis has evolved into two major subpopulations: patients who rapidly recover, and those who develop chronic critical illness (CCI). Our primary aim was to determine whether CCI sepsis survivors manifest unique blood leukocyte transcriptomes in late sepsis that differ from transcriptomes among sepsis survivors with rapid recovery. In a prospective cohort study of surgical ICU patients, genome-wide expression analysis was conducted on total leukocytes in human whole blood collected on days 1 and 14 from sepsis survivors who rapidly recovered or developed CCI, defined as ICU length of stay ≥ 14 days with persistent organ dysfunction. Both sepsis patients who developed CCI and those who rapidly recovered exhibited marked changes in genome-wide expression at day 1 which remained abnormal through day 14. Although summary changes in gene expression were similar between CCI patients and subjects who rapidly recovered, CCI patients exhibited differential expression of 185 unique genes compared with rapid recovery patients at day 14 (p < 0.001). The transcriptomic patterns in sepsis survivors reveal an ongoing immune dyscrasia at the level of the blood leukocyte transcriptome, consistent with persistent inflammation and immune suppression. Furthermore, the findings highlight important genes that could compose a prognostic transcriptomic metric or serve as therapeutic targets among sepsis patients that develop CCI.

Analysis of the Plasma Metabolome after Trauma, Novel Circulating Sphingolipid Signatures, and In-Hospital Outcomes

BACKGROUND

Trauma is the leading cause of death and disability for individuals under age 55. Many severely injured trauma patients experience complicated clinical courses despite appropriate initial therapy. We sought to identify novel circulating metabolomic signatures associated with clinical outcomes following trauma.

STUDY DESIGN

Untargeted metabolomics and circulating plasma immune mediator analysis was performed on plasma collected during 3 post-injury time periods (<6 hours [h], 6 h-24h, day 2-day 5) in critically ill trauma patients enrolled between April 2004 and May 2013 at UPMC Presbyterian Hospital in Pittsburgh, PA. Inclusion criteria were age ≥ 18 years, blunt mechanism, ICU admission, and expected survival ≥ 24 h. Exclusion criteria were isolated head injury, spinal cord injury, and pregnancy. Exploratory endpoints included length of stay (overall and ICU), ventilator requirements, nosocomial infection, and Marshall organ dysfunction (MOD) score. The top 50 metabolites were isolated using repeated measures ANOVA and multivariate empirical Bayesian analysis for further study.

RESULTS

Eighty-six patients were included for analysis. Sphingolipids were enriched significantly (chi-square, p < 10-6) among the top 50 metabolites. Clustering of sphingolipid patterns identified 3 patient subclasses: nonresponders (no time-dependent change in sphingolipids, n = 41), sphingosine/sphinganine-enhanced (n = 24), and glycosphingolipid-enhanced (n = 21). Compared with the sphingolipid-enhanced subclasses, nonresponders had longer mean length of stay, more ventilator days, higher MOD scores, and higher circulating levels of proinflammatory immune mediators IL-6, IL-8, IL-10, MCP1/CCL2, IP10/CXCL10, and MIG/CXCL9 (all p < 0.05), despite similar Injury Severity Scores (p = 0.12).

CONCLUSIONS

Metabolomic analysis identified broad alterations in circulating plasma sphingolipids after blunt trauma. Circulating sphingolipid signatures and their association with both clinical outcomes and circulating inflammatory mediators suggest a possible link between sphingolipid metabolism and the immune response to trauma.

Immunological Endotyping of Chronic Critical Illness After Severe Sepsis

Improved management of severe sepsis has been one of the major health care accomplishments of the last two decades. Due to enhanced recognition and improved management of severe sepsis, in-hospital mortality has been reduced by up to 40%. With that good news, a new syndrome has unfortunately replaced in-hospital multi-organ failure and death. This syndrome of chronic critical illness (CCI) includes sepsis patients who survive the early "cytokine or genomic storm," but fail to fully recover, and progress into a persistent state of manageable organ injury requiring prolonged intensive care. These patients are commonly discharged to long-term care facilities where sepsis recidivism is high. As many as 33% of sepsis survivors develop CCI. CCI is the result, at least in part, of a maladaptive host response to chronic pattern-recognition receptor (PRR)-mediated processes. This maladaptive response results in dysregulated myelopoiesis, chronic inflammation, T-cell atrophy, T-cell exhaustion, and the expansion of suppressor cell functions. We have defined this panoply of host responses as a persistent inflammatory, immune suppressive and protein catabolic syndrome (PICS). Why is this important? We propose that PICS in survivors of critical illness is its own common, unique immunological endotype driven by the constant release of organ injury-associated, endogenous alarmins, and microbial products from secondary infections. While this syndrome can develop as a result of a diverse set of pathologies, it represents a shared outcome with a unique underlying pathobiological mechanism. Despite being a common outcome, there are no therapeutic interventions other than supportive therapies for this common disorder. Only through an improved understanding of the immunological endotype of PICS can rational therapeutic interventions be designed.

Distinct immunologic endotypes are associated with clinical trajectory after severe blunt trauma and hemorrhagic shock

BACKGROUND

The genomic/cytokine "storm" after severe trauma is well described. However, the differing composition, magnitude and resolution of this response, and its relationship to clinical outcomes remain unclear.

METHODS

This is a secondary analysis of a prospective longitudinal cohort study of severely injured trauma patients in hemorrhagic shock. Peripheral blood sampling was performed at 0.5, 1, 4, 7, 14, and 28 days after injury for measurement of circulating immune biomarkers. K-means clustering using overall mean and trajectory slope of selected immunologic biomarkers were used to identify distinct temporal immunologic endotypes. Endotypes were compared with known clinical trajectories defined as early death (<14 days), chronic critical illness (CCI) (ICU length of stay of ≥14 days with persistent organ dysfunction), and rapid recovery (RAP) (ICU length of stay of <14 days with organ recovery).

RESULTS

The cohort included 102 subjects enrolled across 2 level 1 trauma centers. We identified three distinct immunologic endotypes (iA, iB, and iC), each with unique associations to clinical trajectory. Endotype iA (n = 47) exhibited a moderate initial proinflammatory response followed by a return to immunologic homeostasis, with a primary clinical trajectory of RAP (n = 44, 93.6%). Endotype iB (n = 44) exhibited an early hyperinflammatory response with persistent inflammation and immunosuppression, with the highest incidence of CCI (n = 10, 22.7%). Endotype iC (n = 11) exhibited a similar hyperinflammatory response, but with rapid return to immunologic homeostasis and a predominant trajectory of RAP (n = 9, 81.8%). Patients with endotype iB had the highest severity/duration of organ dysfunction and highest incidence of nosocomial infections (50%, p = 0.001), and endotype iB was the predominant endotype of patients who developed CCI (10 of 13 patients, 76.9%; p = 0.002).

CONCLUSION

We identified three distinct immunologic endotypes after severe injury differing the magnitude and duration of the early response. The clinical trajectory of CCI is characterized by an endotype (iB) defined by persistent alteration in inflammation/immunosuppression and is associated with poor clinical outcomes.

LEVEL OF EVIDENCE

Prognostic, level III.

Hemorrhagic Shock Induces a Rapid Transcriptomic Shift of the Immune Balance in Leukocytes after Experimental Multiple Injury

The immune response following trauma represents a major driving force of organ dysfunction and poor outcome. Therefore, we investigated the influence of an additional hemorrhagic shock (HS) on the early posttraumatic immune dysbalance in the whole population of blood leukocytes. A well-established murine polytrauma (PT) model with or without an additional pressure-controlled HS (mean arterial pressure of 30 mmHg (±5 mmHg) for 60 mins, afterwards fluid resuscitation with balanced electrolyte solution four times the volume of blood drawn) was used. C57BL/6 mice were randomized into a control, PT, and PT + HS group with three animals in each group. Four hours after trauma, corresponding to three hours after induction of hemorrhage, RNA was isolated from all peripheral blood leukocytes, and a microarray analysis was performed. Enrichment analysis was conducted on selected genes strongly modulated by the HS. After additional HS in PT mice, the gene expression of pathways related to the innate immunity, such as IL-6 production, neutrophil chemotaxis, cell adhesion, and toll-like receptor signaling was upregulated, whereas pathways of the adaptive immune system, such as B- and T-cell activation as well as the MHC class II protein complex, were downregulated. These results demonstrate that an additional HS plays an important role in the immune dysregulation early after PT by shifting the balance to increased innate and reduced adaptive immune responses.

Iodine Redistribution During Trauma, Sepsis, and Hibernation: An Evolutionarily Conserved Response to Severe Stress

OBJECTIVE

We performed these studies to learn how iodine in the form of free iodide behaves during stress.

DESIGN

Prospective observational trial using samples obtained from human trauma patients and retrospective observational study using remnant samples from human sepsis patients and arctic ground squirrels. Preclinical interventional study using hind-limb ischemia and reperfusion injury in mice.

SETTING

Level I trauma center emergency room and ICU and animal research laboratories.

SUBJECTS

Adult human sepsis and trauma patients, wild-caught adult arctic ground squirrels, and sexually mature laboratory mice.

INTERVENTIONS

Ischemia and reperfusion injury was induced in mice by temporary application of tourniquet to one hind-limb. Iodide was administered IV just prior to reperfusion.

MEASUREMENTS AND MAIN RESULTS

Free iodide was measured using ion chromatography. Relative to iodide in plasma from normal donors, iodide was increased 17-fold in plasma from trauma patients and 26-fold in plasma from sepsis patients. In arctic ground squirrels, iodide increases over three-fold during hibernation. And during ischemia/reperfusion injury in mice, iodide accumulates in ischemic tissue and reduces both local and systemic tissue damage.

CONCLUSIONS

Iodide redistributes during stress and improves outcome after injury. Essential functions of iodide may have contributed to its evolutionary selection and be useful as a therapeutic intervention for human patients.

Preferential inhibition of adaptive immune system dynamics by glucocorticoids in patients after acute surgical trauma

Glucocorticoids (GC) are a controversial yet commonly used intervention in the clinical management of acute inflammatory conditions, including sepsis or traumatic injury. In the context of major trauma such as surgery, concerns have been raised regarding adverse effects from GC, thereby necessitating a better understanding of how GCs modulate the immune response. Here we report the results of a randomized controlled trial (NCT02542592) in which we employ a high-dimensional mass cytometry approach to characterize innate and adaptive cell signaling dynamics after a major surgery (primary outcome) in patients treated with placebo or methylprednisolone (MP). A robust, unsupervised bootstrap clustering of immune cell subsets coupled with random forest analysis shows profound (AUC = 0.92, p-value = 3.16E-8) MP-induced alterations of immune cell signaling trajectories, particularly in the adaptive compartments. By contrast, key innate signaling responses previously associated with pain and functional recovery after surgery, including STAT3 and CREB phosphorylation, are not affected by MP. These results imply cell-specific and pathway-specific effects of GCs, and also prompt future studies to examine GCs' effects on clinical outcomes likely dependent on functional adaptive immune responses.

Cellular Immunoprofile of Peritoneal Environment During a HIPEC Procedure

BACKGROUND

We characterized the peritoneal immune cellular profile during cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) in this pilot study.

METHODS

We prospectively performed flow cytometric analysis of peritoneal fluid collected at laparotomy and during HIPEC at 0, 30, 60, and 90 min. Analysis consisted of standard flow cytometric leukocyte gating and the use of antibodies for stem cells, B lymphocytes, T-helper, T-suppressor, and natural killer (NK) cells.

RESULTS

The mean peritoneal carcinomatosis index (PCI) score was 19.8 ± 11.5 (median 19). Twelve patients had a completeness of cytoreduction (CCR) score of 0-1, and three patients had a CCR score of ≥ 2 (20%). The proportion of peritoneal NK cells remained stable (p = 0.655) throughout perfusion. The CD4/CD8 ratio (p = 0.019) and granulocyte/lymphocyte ratio (p = 0.018) evolved during cytoreduction, with no further change during HIPEC. Two distinct temporal patterns of peritoneal T lymphocytes became evident (the 'high' and 'low' CD4/CD8 ratio groups) and patients maintained their high versus low peritoneal CD4/CD8 ratio status throughout the duration of HIPEC. High CD4/CD8 was associated with longer cytoreduction (p = 0.019) and borderline higher PCI score (p = 0.058). No association was identified with age (p = 0.131), sex (p = 1.000), CCR status (p = 0.580), occurrence of complication (p = 0.282), or ascites volume (p = 0.713).

CONCLUSION

The cellular immunoprofile of peritoneal fluid during HIPEC is stable but changes during cytoreduction. Two distinct immune groups emerged, based on CD4/CD8 ratios in the peritoneal perfusate. Further studies are warranted to evaluate peritoneal immunity and the clinical significance of novel peritoneal immune phenotype.

Persistently increased cell-free DNA concentrations only modestly contribute to outcome and host response in sepsis survivors with chronic critical illness

BACKGROUND

Although early survival from sepsis has improved with timely resuscitation and source control, survivors frequently experience persistent inflammation and develop chronic critical illness. We examined whether increased copy number of endogenous alarmins, mitochondrial DNA, and nuclear DNA are associated with the early "genomic storm" in blood leukocytes and the development of chronic critical illness in hospitalized patients with surgical sepsis.

METHODS

A prospective, observational, cohort study of critically ill septic patients was performed at a United States tertiary health care center. Blood samples were obtained at multiple time points after the onset of sepsis. Droplet Digital polymerase chain reaction (Bio-Rad Laboratories, Hercules, CA) was performed to quantify RHO (nuclear DNA) and MT-CO2 (mitochondrial DNA) copies in plasma. Leukocyte transcriptomic expression of 63 genes was also measured in whole blood.

RESULTS

We enrolled 112 patients with surgical sepsis. Two experienced early death, 69 recovered rapidly, and 41 developed chronic critical illness. Both mitochondrial DNA and nuclear DNA copy number were increased in all sepsis survivors, but early nuclear DNA, and not mitochondrial DNA, copy number was further increased in patients who developed chronic critical illness. Cell-free DNA copy number was associated with in-hospital but not long-term (180-day and 365-day) mortality and were only weakly correlated with leukocyte transcriptomics.

CONCLUSION

Increased cell-free DNA copy number persists in survivors of sepsis but is not strongly associated with leukocyte transcriptomics. Nuclear DNA but not mitochondrial DNA copy number is associated with adverse, short-term, clinical trajectories and outcomes.

Machine learning for the detection of early immunological markers as predictors of multi-organ dysfunction

The immune response to major trauma has been analysed mainly within post-hospital admission settings where the inflammatory response is already underway and the early drivers of clinical outcome cannot be readily determined. Thus, there is a need to better understand the immediate immune response to injury and how this might influence important patient outcomes such as multi-organ dysfunction syndrome (MODS). In this study, we have assessed the immune response to trauma in 61 patients at three different post-injury time points (ultra-early (<=1 h), 4-12 h, 48-72 h) and analysed relationships with the development of MODS. We developed a pipeline using Absolute Shrinkage and Selection Operator and Elastic Net feature selection methods that were able to identify 3 physiological features (decrease in neutrophil CD62L and CD63 expression and monocyte CD63 expression and frequency) as possible biomarkers for MODS development. After univariate and multivariate analysis for each feature alongside a stability analysis, the addition of these 3 markers to standard clinical trauma injury severity scores yields a Generalized Liner Model (GLM) with an average Area Under the Curve value of 0.92 ± 0.06. This performance provides an 8% improvement over the Probability of Survival (PS14) outcome measure and a 13% improvement over the New Injury Severity Score (NISS) for identifying patients at risk of MODS.

Cell-free nuclear, but not mitochondrial, DNA concentrations correlate with the early host inflammatory response after severe trauma

Severe blunt trauma is associated with an early ‘genomic storm’ which causes simultaneous up- and down-regulation of host protective immunity. Excessive inflammation can lead to organ injury. In the absence of infection, the inflammatory response is presumably driven by release of endogenous alarmins called danger-associated molecular patterns (DAMPs), which initiate immune responses through pattern-recognition receptors (PRR). Here we examined the relationship between concentrations of cell-free (cf) nuclear DNA (ncDNA) and mitochondrial DNA (mtDNA) within 24 hours post trauma with circulating leukocyte transcriptomics and plasma IL-6 concentrations, as well as the patients’ clinical trajectories. In 104 patients enrolled from two level-1 trauma centers, ncDNA and mtDNA concentrations were increased within 24 hours of severe trauma, but only ncDNA concentrations correlated with leukocyte gene expression and outcomes. Surprisingly, ncDNA, not mtDNA concentrations, were significantly elevated in trauma patients who developed chronic critical illness versus rapid clinical recovery. Plasma IL-6 and leukocyte transcriptomics were better predictors of outcomes than cfDNA levels. Although mtDNA and ncDNA are significantly increased in the immediate post-trauma period, the dramatic inflammatory and gene expression changes seen after severe trauma are only weakly correlated with ncDNA concentrations, and more importantly, mtDNA concentrations are not associated with adverse clinical trajectories.

Physical proximity and functional cooperation of glycoprotein 130 and glycoprotein VI in platelet membrane lipid rafts

OBJECTIVE

Clinical and laboratory studies have demonstrated that platelets become hyperactive and prothrombotic in conditions of inflammation. We have previously shown that the proinflammatory cytokine interleukin (IL)-6 forms a complex with soluble IL-6 receptor α (sIL-6Rα) to prime platelets for activation by subthreshold concentrations of collagen. Upon being stimulated with collagen, the transcription factor signal transducer and activator of transcription (STAT) 3 in platelets is phosphorylated and dimerized to act as a protein scaffold to facilitate the catalytic action between the kinase Syk and the substrate phospholipase Cγ2 (PLCγ2) in collagen-induced signaling. However, it remains unknown how collagen induces phosphorylation and dimerization of STAT3.

METHODS AND RESULTS

We conducted complementary in vitro experiments to show that the IL-6 receptor subunit glycoprotein 130 (GP130) was in physical proximity to the collagen receptor glycoprotein VI (GPVI in membrane lipid rafts of platelets. This proximity allows collagen to induce STAT3 activation and dimerization, and the IL-6-sIL-6Rα complex to activate the kinase Syk and the substrate PLCγ2 in the GPVI signal pathway, resulting in an enhanced platelet response to collagen. Disrupting lipid rafts or blocking GP130-Janus tyrosine kinase (JAK)-STAT3 signaling abolished the cross-activation and reduced platelet reactivity to collagen.

CONCLUSION

These results demonstrate cross-talk between collagen and IL-6 signal pathways. This cross-talk could potentially provide a novel mechanism for inflammation-induced platelet hyperactivity, so the IL-6-GP130-JAK-STAT3 pathway has been identified as a potential target to block this hyperactivity.

Diagnosing and Managing Sepsis by Probing the Host Response to Infection: Advances, Opportunities, and Challenges

Sepsis is a major source of mortality and morbidity globally. Accurately diagnosing sepsis remains challenging due to the heterogeneous nature of the disease, and delays in diagnosis and intervention contribute to high mortality rates. Measuring the host response to infection enables more rapid diagnosis of sepsis than is possible through direct detection of the causative pathogen, and recent advances in host response diagnostics and prognostics hold promise for improving outcomes. The current review discusses recent advances in the technologies used to probe the host response to infection, particularly those based on transcriptomics. These are discussed in the context of contemporary approaches to diagnosing and prognosing sepsis, and recommendations are made for successful development and validation of host response technologies.