Patients with cancer and sepsis trials: an unfair representation?

Approximately 20% of sepsis cases are thought to occur in patients with cancer. Thus, such patients are an important cohort to be represented and characterised among sepsis trials. However, patients with cancer are commonly excluded from sepsis trials, although the extent to which is unknown. In this opinion article, we discuss our findings that suggest that patients with cancer are being under-represented in sepsis trials, often with an unclear rationale. We question the validity of generalising results from sepsis trials to heterogenous cancer populations and call for wider inclusion of patients with cancer to bridge this knowledge gap in sepsis management.

Sotrovimab restores neutralization against current Omicron subvariants in patients with blood cancer.

Wu et al. report that patients with hematologic malignancies have reduced immunity against SARS-CoV-2 Omicron subvariants and Sotrovimab retains neutralizing capacity against all tested Omicron subvariants.

AXL Expression on Homeostatic Resident Liver Macrophages Is Reduced in Cirrhosis Following GAS6 Production by Hepatic Stellate Cells.

BACKGROUND & AIMS: AXL and MERTK expression on circulating monocytes modulated immune responses in patients with cirrhosis (CD14+HLA-DR+AXL+) and acute-on-chronic liver failure (CD14+MERTK+). AXL expression involved enhanced efferocytosis, sustained phagocytosis, but reduced tumor necrosis factor-α/interleukin-6 production and T-cell activation, suggesting a homeostatic function. Axl was expressed on murine airway in tissues contacting the external environment, but not interstitial lung- and tissue-resident synovial lining macrophages. Here, we assessed AXL expression on tissue macrophages in patients with cirrhosis. METHODS: Using multiplexed immunofluorescence we compared AXL expression in liver biopsies in cirrhosis (n = 22), chronic liver disease (n = 8), non-cirrhotic portal hypertension (n = 4), and healthy controls (n = 4). Phenotype and function of isolated primary human liver macrophages were characterized by flow cytometry (cirrhosis, n = 11; control, n = 14) ex vivo. Also, AXL expression was assessed on peritoneal (n = 29) and gut macrophages (n = 16) from cirrhotic patients. Regulation of AXL expression was analyzed in vitro and ex vivo using primary hepatic stellate cells (HSCs), LX-2 cells, and GAS6 in co-culture experiments. RESULTS: AXL was expressed on resident (CD68+) but not tissue-infiltrating (MAC387+) liver macrophages, hepatocytes, HSCs, or sinusoidal endothelial cells. Prevalence of hepatic CD68+AXL+ cells significantly decreased with cirrhosis progression: (healthy, 90.2%; Child-Pugh A, 76.1%; Child-Pugh B, 64.5%; and Child-Pugh C, 18.7%; all P < .05) and negatively correlated with Model for End-Stage Liver Disease and C-reactive protein (all P < .05). AXL-expressing hepatic macrophages were CD68highHLA-DRhighCD16highCD206high. AXL expression also decreased on gut and peritoneal macrophages from cirrhotic patients but increased in regional lymph nodes. GAS6, enriched in the cirrhotic liver, appeared to be secreted by HSCs and down-regulate AXL in vitro. CONCLUSIONS: Decreased AXL expression on resident liver macrophages in advanced cirrhosis, potentially in response to activated HSC-secreted GAS6, suggests a role for AXL in the regulation of hepatic immune homeostasis.

Sepsis biomarkers and diagnostic tools with a focus on machine learning.

Over the last years, there have been advances in the use of data-driven techniques to improve the definition, early recognition, subtypes characterisation, prognostication and treatment personalisation of sepsis. Some of those involve the discovery or evaluation of biomarkers or digital signatures of sepsis or sepsis sub-phenotypes. It is hoped that their identification may improve timeliness and accuracy of diagnosis, suggest physiological pathways and therapeutic targets, inform targeted recruitment into clinical trials, and optimise clinical management. Given the complexities of the sepsis response, panels of biomarkers or models combining biomarkers and clinical data are necessary, as well as specific data analysis methods, which broadly fall under the scope of machine learning. This narrative review gives a brief overview of the main machine learning techniques (mainly in the realms of supervised and unsupervised methods) and published applications that have been used to create sepsis diagnostic tools and identify biomarkers.

Functional immune responses against SARS-CoV-2 variants of concern after fourth COVID-19 vaccine dose or infection in patients with blood cancer.

Patients with blood cancer continue to have a greater risk of inadequate immune responses following three COVID-19 vaccine doses and risk of severe COVID-19 disease. In the context of the CAPTURE study (NCT03226886), we report immune responses in 80 patients with blood cancer who received a fourth dose of BNT162b2. We measured neutralizing antibody titers (NAbTs) using a live virus microneutralization assay against wild-type (WT), Delta, and Omicron BA.1 and BA.2 and T cell responses against WT and Omicron BA.1 using an activation-induced marker (AIM) assay. The proportion of patients with detectable NAb titers and T cell responses after the fourth vaccine dose increased compared with that after the third vaccine dose. Patients who received B cell-depleting therapies within the 12 months before vaccination have the greatest risk of not having detectable NAbT. In addition, we report immune responses in 57 patients with breakthrough infections after vaccination.

Evolution of practice patterns in the management of acute respiratory distress syndrome: A secondary analysis of two successive randomized controlled trials.

PURPOSE: We sought to examine changes in acute respiratory distress syndrome (ARDS) management over a 12-year period of two successive randomized trials. METHODS: Analyses included baseline data, from eligible patients, prior to influence of trial protocols, and daily study data, from randomized patients, of variables not determined by trial protocols. Mixed linear regressions examined changes in practice year-on-year. RESULTS: A total of 2376 patients met the inclusion criteria. Over the 12-year period, baseline tidal volume index decreased (9.0 to 7.0 ml/kg, p < 0.001), plateau pressures decreased (30.8 to 29.0 cmH2O, p < 0.05), and baseline positive end-expiratory pressures increased (10.8 to 13.2 cmH2O, p < 0.001). Volume-controlled ventilation declined from 29.4 to 14.0% (p < 0.01). Use of corticosteroids increased (baseline: 7.7 to 30.3%; on study: 32.6 to 61.2%; both p < 0.001), as did neuromuscular blockade (baseline: 12.3 to 24.5%; on study: 55.5 to 70.0%; both p < 0.01). Inhaled nitric oxide use increased (24.9 to 65.8%, p < 0.05). We observed no significant change in prone positioning (16.2 to 18.9%, p = 0.70). CONCLUSIONS: Clear trends were apparent in tidal volume, airway pressures, ventilator modes, adjuncts and rescue therapies. With the exception of prone positioning, and outside the context of rescue therapy, these trends appear consistent with the evolving literature on ARDS management.

Natural history, trajectory, and management of mechanically ventilated COVID-19 patients in the United Kingdom.

PURPOSE: The trajectory of mechanically ventilated patients with coronavirus disease 2019 (COVID-19) is essential for clinical decisions, yet the focus so far has been on admission characteristics without consideration of the dynamic course of the disease in the context of applied therapeutic interventions. METHODS: We included adult patients undergoing invasive mechanical ventilation (IMV) within 48 h of intensive care unit (ICU) admission with complete clinical data until ICU death or discharge. We examined the importance of factors associated with disease progression over the first week, implementation and responsiveness to interventions used in acute respiratory distress syndrome (ARDS), and ICU outcome. We used machine learning (ML) and Explainable Artificial Intelligence (XAI) methods to characterise the evolution of clinical parameters and our ICU data visualisation tool is available as a web-based widget ( https://www.CovidUK.ICU ). RESULTS: Data for 633 adults with COVID-19 who underwent IMV between 01 March 2020 and 31 August 2020 were analysed. Overall mortality was 43.3% and highest with non-resolution of hypoxaemia [60.4% vs17.6%; P < 0.001; median PaO2/FiO2 on the day of death was 12.3(8.9-18.4) kPa] and non-response to proning (69.5% vs.31.1%; P < 0.001). Two ML models using weeklong data demonstrated an increased predictive accuracy for mortality compared to admission data (74.5% and 76.3% vs 60%, respectively). XAI models highlighted the increasing importance, over the first week, of PaO2/FiO2 in predicting mortality. Prone positioning improved oxygenation only in 45% of patients. A higher peak pressure (OR 1.42[1.06-1.91]; P < 0.05), raised respiratory component (OR 1.71[ 1.17-2.5]; P < 0.01) and cardiovascular component (OR 1.36 [1.04-1.75]; P < 0.05) of the sequential organ failure assessment (SOFA) score and raised lactate (OR 1.33 [0.99-1.79]; P = 0.057) immediately prior to application of prone positioning were associated with lack of oxygenation response. Prone positioning was not applied to 76% of patients with moderate hypoxemia and 45% of those with severe hypoxemia and patients who died without receiving proning interventions had more missed opportunities for prone intervention [7 (3-15.5) versus 2 (0-6); P < 0.001]. Despite the severity of gas exchange deficit, most patients received lung-protective ventilation with tidal volumes less than 8 mL/kg and plateau pressures less than 30cmH2O. This was despite systematic errors in measurement of height and derived ideal body weight. CONCLUSIONS: Refractory hypoxaemia remains a major association with mortality, yet evidence based ARDS interventions, in particular prone positioning, were not implemented and had delayed application with an associated reduced responsiveness. Real-time service evaluation techniques offer opportunities to assess the delivery of care and improve protocolised implementation of evidence-based ARDS interventions, which might be associated with improvements in survival.

A Wolf in Sheep's Clothing: Systemic Immune Activation Post Immunotherapy.

Introduction: Immune checkpoint inhibitors (ICIs) are increasingly a standard of care for many cancers; these agents can result in immune-related adverse events (irAEs) including fever, which is common but can rarely be associated with systemic immune activation (SIA or acquired HLH). Methods: All consecutive patients receiving ICIs in the Drug Development Unit of the Royal Marsden Hospital between May 2014 and November 2019 were retrospectively reviewed. Patients with fever ≥ 38°C or chills/rigors (without fever) ≤ 6 weeks of commencing ICIs were identified for clinical data collection. Results: Three patients met diagnostic criteria for SIA/HLH with median time to onset of symptoms of 10 days. We describe the clinical evolution, treatment used, and outcomes for these patients. High-dose steroids are used first-line with other treatments, such as tocilizumab, immunoglobulin and therapeutic plasmapheresis can be considered for steroid-refractory SIA/HLH. Conclusion: SIA/HLH post ICI is a rare but a potentially fatal irAE that presents with fever and a constellation of nonspecific symptoms. Early recognition and timely treatment are key to improving outcomes.

The National Institute for Health Research Critical Care Research Priority Setting Survey 2018.

INTRODUCTION: Defining research priorities in intensive care is key to determining appropriate allocation of funding. Several topics were identified from the 2014 James Lind Alliance priority setting exercise conducted with the Intensive Care Society. The James Lind Alliance process included significant (and vital) patient/public contribution, but excluded professionals without a bedside role. As a result it may have failed to identify potential early-stage translational research topics, which are more likely identified by medical and/or academic members of relevant specialist basic science groups. The objective of the present project was to complement the James Lind Alliance project by generating an updated list of research priorities by facilitating academic research input. METHOD: A survey was conducted by the National Institute for Health Research (NIHR) to identify the key research priorities from intensive care clinicians, including allied health professionals and academics, along with any evolving themes arising from translational research. Feasibility of all identified topics were then discussed and allocated to themes by a joint clinical academics/NIHR focus group. RESULTS: The survey was completed by 94 intensive care clinicians (including subspecialists), academics and allied health professions. In total, 203 research questions were identified, with the top five themes focusing on: appropriate case selection (e.g. who and when to treat; 24%), ventilation (7%), sepsis (6%), delirium (5%) and rehabilitation (5%). DISCUSSION: Utilising a methodology distinct from that employed by the James Lind Alliance process, from a broad spectrum of intensive care clinicians/scientists, enabled identification of a variety of priority research areas. These topics can now inform not only the investigator-led research agenda, but will also be considered in due course by the NIHR for potential future funding calls.

Monocytes mediate homing of circulating microvesicles to the pulmonary vasculature during low-grade systemic inflammation.

Microvesicles (MVs), a plasma membrane-derived subclass of extracellular vesicles, are produced and released into the circulation during systemic inflammation, yet little is known of cell/tissue-specific uptake of MVs under these conditions. We hypothesized that monocytes contribute to uptake of circulating MVs and that their increased margination to the pulmonary circulation and functional priming during systemic inflammation produces substantive changes to the systemic MV homing profile. Cellular uptake of i.v.-injected, fluorescently labelled MVs (J774.1 macrophage-derived) in vivo was quantified by flow cytometry in vascular cell populations of the lungs, liver and spleen of C57BL6 mice. Under normal conditions, both Ly6Chigh and Ly6Clow monocytes contributed to MV uptake but liver Kupffer cells were the dominant target cell population. Following induction of sub-clinical endotoxemia with low-dose i.v. LPS, MV uptake by lung-marginated Ly6Chigh monocytes increased markedly, both at the individual cell level (~2.5-fold) and through substantive expansion of their numbers (~8-fold), whereas uptake by splenic macrophages was unchanged and uptake by Kupffer cells actually decreased (~50%). Further analysis of MV uptake within the pulmonary vasculature using a combined model approach of in vivo macrophage depletion, ex vivo isolated perfused lungs and in vitro lung perfusate cell-based assays, indicated that Ly6Chigh monocytes possess a high MV uptake capacity (equivalent to Kupffer cells), that is enhanced directly by endotoxemia and ablated in the presence of phosphatidylserine (PS)-enriched liposomes and ß3 integrin receptor blocking peptide. Accordingly, i.v.-injected PS-enriched liposomes underwent a redistribution of cellular uptake during endotoxemia similar to MVs, with enhanced uptake by Ly6Chigh monocytes and reduced uptake by Kupffer cells. These findings indicate that monocytes, particularly lung-marginated Ly6Chigh subset monocytes, become a dominant target cell population for MVs during systemic inflammation, with significant implications for the function and targeting of endogenous and therapeutically administered MVs, lending novel insights into the pathophysiology of pulmonary vascular inflammation.

The Coagulation and Immune Systems Are Directly Linked through the Activation of Interleukin-1α by Thrombin.

Ancient organisms have a combined coagulation and immune system, and although links between inflammation and hemostasis exist in mammals, they are indirect and slower to act. Here we investigated direct links between mammalian immune and coagulation systems by examining cytokine proproteins for potential thrombin protease consensus sites. We found that interleukin (IL)-1α is directly activated by thrombin. Thrombin cleaved pro-IL-1α at a site perfectly conserved across disparate species, indicating functional importance. Surface pro-IL-1α on macrophages and activated platelets was cleaved and activated by thrombin, while tissue factor, a potent thrombin activator, colocalized with pro-IL-1α in the epidermis. Mice bearing a mutation in the IL-1α thrombin cleavage site (R114Q) exhibited defects in efficient wound healing and rapid thrombopoiesis after acute platelet loss. Thrombin-cleaved IL-1α was detected in humans during sepsis, pointing to the relevance of this pathway for normal physiology and the pathogenesis of inflammatory and thrombotic diseases.

Mesenchymal stem cells enhance NOX2-dependent reactive oxygen species production and bacterial killing in macrophages during sepsis.

Human mesenchymal stem/stromal cells (MSCs) have been reported to produce an M2-like, alternatively activated phenotype in macrophages. In addition, MSCs mediate effective bacterial clearance in pre-clinical sepsis models. Thus, MSCs have a paradoxical antimicrobial and anti-inflammatory response that is not understood.Here, we studied the phenotypic and functional response of monocyte-derived human macrophages to MSC exposure in vitroMSCs induced two distinct, coexistent phenotypes: M2-like macrophages (generally elongated morphology, CD163+, acute phagosomal acidification, low NOX2 expression and limited phagosomal superoxide production) and M1-like macrophages characterised by high levels of phagosomal superoxide production. Enhanced phagosomal reactive oxygen species production was also observed in alveolar macrophages from a rodent model of pneumonia-induced sepsis. The production of M1-like macrophages was dependent on prostaglandin E2 and phosphatidylinositol 3-kinase. MSCs enhanced human macrophage phagocytosis of unopsonised bacteria and enhanced bacterial killing compared with untreated macrophages. Bacterial killing was significantly reduced by blockade of NOX2 using diphenyleneiodonium, suggesting that M1-like cells are primarily responsible for this effect. MSCs also enhanced phagocytosis and polarisation of M1-like macrophages derived from patients with severe sepsis.The enhanced antimicrobial capacity (M1-like) and inflammation resolving phenotype (M2-like) may account for the paradoxical effect of these cells in sepsis in vivo.

Intravascular donor monocytes play a central role in lung transplant ischaemia-reperfusion injury.

RATIONALE: Primary graft dysfunction in lung transplant recipients derives from the initial, largely leukocyte-dependent, ischaemia-reperfusion injury. Intravascular lung-marginated monocytes have been shown to play key roles in experimental acute lung injury, but their contribution to lung ischaemia-reperfusion injury post transplantation is unknown. OBJECTIVE: To define the role of donor intravascular monocytes in lung transplant-related acute lung injury and primary graft dysfunction. METHODS: Isolated perfused C57BL/6 murine lungs were subjected to warm ischaemia (2 hours) and reperfusion (2 hours) under normoxic conditions. Monocyte retention, activation phenotype and the effects of their depletion by intravenous clodronate-liposome treatment on lung inflammation and injury were determined. In human donor lung transplant samples, the presence and activation phenotype of monocytic cells (low side scatter, 27E10+, CD14+, HLA-DR+, CCR2+) were evaluated by flow cytometry and compared with post-implantation lung function. RESULTS: In mouse lungs following ischaemia-reperfusion, substantial numbers of lung-marginated monocytes remained within the pulmonary microvasculature, with reduced L-selectin and increased CD86 expression indicating their activation. Monocyte depletion resulted in reductions in lung wet:dry ratios, bronchoalveolar lavage fluid protein, and perfusate levels of RAGE, MIP-2 and KC, while monocyte repletion resulted in a partial restoration of the injury. In human lungs, correlations were observed between pre-implantation donor monocyte numbers/their CD86 and TREM-1 expression and post-implantation lung dysfunction at 48 and 72 hours. CONCLUSIONS: These results indicate that lung-marginated intravascular monocytes are retained as a 'passenger' leukocyte population during lung transplantation, and play a key role in the development of transplant-associated ischaemia-reperfusion injury.

In vivo compartmental analysis of leukocytes in mouse lungs.

The lung has a unique structure consisting of three functionally different compartments (alveolar, interstitial, and vascular) situated in an extreme proximity. Current methods to localize lung leukocytes using bronchoalveolar lavage and/or lung perfusion have significant limitations for determination of location and phenotype of leukocytes. Here we present a novel method using in vivo antibody labeling to enable accurate compartmental localization/quantification and phenotyping of mouse lung leukocytes. Anesthetized C57BL/6 mice received combined in vivo intravenous and intratracheal labeling with fluorophore-conjugated anti-CD45 antibodies, and lung single-cell suspensions were analyzed by flow cytometry. The combined in vivo intravenous and intratracheal CD45 labeling enabled robust separation of the alveolar, interstitial, and vascular compartments of the lung. In naive mice, the alveolar compartment consisted predominantly of resident alveolar macrophages. The interstitial compartment, gated by events negative for both intratracheal and intravenous CD45 staining, showed two conventional dendritic cell populations, as well as a Ly6C(lo) monocyte population. Expression levels of MHCII on these interstitial monocytes were much higher than on the vascular Ly6C(lo) monocyte populations. In mice exposed to acid aspiration-induced lung injury, this protocol also clearly distinguished the three lung compartments showing the dynamic trafficking of neutrophils and exudative monocytes across the lung compartments during inflammation and resolution. This simple in vivo dual-labeling technique substantially increases the accuracy and depth of lung flow cytometric analysis, facilitates a more comprehensive examination of lung leukocyte pools, and enables the investigation of previously poorly defined "interstitial" leukocyte populations during models of inflammatory lung diseases.

The role of ex vivo lung perfusion in lung transplantation.

Whilst lung transplantation is a viable solution for end-stage lung disease, donor shortages, donor lung inflammation and perioperative lung injury remain major limitations. Ex vivo lung perfusion has emerged as the next frontier in lung transplantation to address and overcome these limitations, with multicentre clinical trials ongoing in the UK, rest of Europe and North America. Our research seeks to identify the poorly understood cellular and molecular mechanisms of primary graft dysfunction through the development of an isolated perfused lung model of transplantation and investigation of the role of pulmonary inflammation in this paradigm.

Volutrauma, but not atelectrauma, induces systemic cytokine production by lung-marginated monocytes.

OBJECTIVES: Ventilator-induced lung injury has substantive impact on mortality of patients with acute respiratory distress syndrome. Although low tidal volume ventilation has been shown to reduce mortality, clinical benefits of open-lung strategy are controversial. In this study, we investigated the impact of two distinct forms of ventilator-induced lung injury, i.e., volutrauma and atelectrauma, on the progression of lung injury and inflammation, in particular alveolar and systemic cytokine production. DESIGN: Ex vivo study. SETTING: University research laboratory. SUBJECTS: C57BL/6 mice. INTERVENTIONS: Isolated, buffer-perfused lungs were allocated to one of three ventilatory protocols for 3 hours: control group received low tidal volume (7 mL/kg) with positive end-expiratory pressure (5 cm H2O) and regular sustained inflation; high-stretch group received high tidal volume (30-32 mL/kg) with positive end-expiratory pressure (3 cm H2O) and sustained inflation; and atelectasis group received the same tidal volume as control but neither positive end-expiratory pressure nor sustained inflation. MEASUREMENTS AND MAIN RESULTS: Both injurious ventilatory protocols developed comparable levels of physiological injury and pulmonary edema, measured by respiratory system mechanics and lavage fluid protein. High-stretch induced marked increases in proinflammatory cytokines in perfusate and lung lavage fluid, compared to control. In contrast, atelectasis had no effect on perfusate cytokines compared to control but did induce some up-regulation of lavage cytokines. Depletion of monocytes marginated within the lung microvasculature, achieved by pretreating mice with i.v. liposome-encapsulated clodronate, significantly attenuated perfusate cytokine levels, especially tumor necrosis factor, in the high-stretch, but not atelectasis group. CONCLUSIONS: Volutrauma (high-stretch), but not atelectrauma (atelectasis), directly activates monocytes within the pulmonary vasculature, leading to cytokine release into systemic circulation. We postulate this as a potential explanation why open-lung strategy has limited mortality benefits in ventilated critically ill patients.