Precision medicine and enrichment in sepsis

Sepsis is defined as a dysregulated host response to infection leading to life-threatening organ dysfunction. While this recent iteration of the sepsis definition rightly centralizes organ dysfunction, it does not reflect on the extensive heterogeneity in the host response observed in sepsis patient populations. Heterogeneity in sepsis has hindered the identification of effective therapeutic targets, with current treatment consisting of antimicrobials and supportive care. In order to address the shortcomings in identifying specific therapeutics for sepsis, the focus of various research activities turned towards developing precision medicine approaches. In particular, efforts aimed at stratifying patients into more homogenous subgroups having common dominant pathophysiological features and outcome trajectories, in turn facilitating the delineation of specific therapies. Here, I review current initiatives in prognostic and predictive enrichment strategies in sepsis patient populations, which will be key to identify patients who would benefit, or be harmed, from specific therapeutic interventions.peer-reviewe

Interleukin-27: a potential new sepsis biomarker exposed through genome-wide transcriptional profiling

Sepsis is a complex clinical condition that is driven predominantly by deviations from the orderly stereotypic immunological response to infection. Much effort has been undertaken in the search for biomarkers that can assist in discriminating critically ill patients with sterile inflammation from those with sepsis. Such biomarkers may aid the clinician in therapeutic decision making upon admission of a patient. Interleukin-27 may be such a discriminative biomarker, as suggested in the previous issue of Critical Care by a study of critically ill childre

The Adhesion G Protein-Coupled Receptor GPR97/ADGRG3 Is Expressed in Human Granulocytes and Triggers Antimicrobial Effector Functions

The adhesion family of G protein-coupled receptors (aGPCRs) comprises 33 members in human, several of which are distinctly expressed and functionally involved in polymorphonuclear cells (PMNs). As former work indicated the possible presence of the aGPCR GPR97 in granulocytes, we studied its cellular distribution, molecular structure, signal transduction, and biological function in PMNs. RNA sequencing and mass-spectrometry revealed abundant RNA and protein expression of ADGRG3/GPR97 in granulocyte precursors and terminally differentiated neutrophilic, eosinophilic, and basophilic granulocytes. Using a newly generated GPR97-specific monoclonal antibody, we confirmed that endogenous GPR97 is a proteolytically processed, dichotomous, N-glycosylated receptor. GPR97 was detected in tissue-infiltrating PMNs and upregulated during systemic inflammation. Antibody ligation of GPR97 increased neutrophil reactive oxygen species production and proteolytic enzyme activity, which is accompanied by an increase in mitogen-activated protein kinases and IκBα phosphorylation. In-depth analysis of the GPR97 signaling cascade revealed a possible switch from basal Gαs/cAMP-mediated signal transduction to a Gαi-induced reduction in cAMP levels upon mutation-induced activation of the receptor, in combination with an increase in downstream effectors of Gβγ, such as SRE and NF-κB. Finally, ligation of GPR97 increased the bacteria uptake and killing activity of neutrophils. We conclude that the specific presence of GPR97 regulates antimicrobial activity in human granulocytes

Immune suppression is associated with enhanced systemic inflammatory, endothelial and procoagulant responses in critically ill patients

Objective: Patients admitted to the Intensive Care Unit (ICU) oftentimes show immunological signs of immune suppression. Consequently, immune stimulatory agents have been proposed as an adjunctive therapy approach in the ICU. The objective of this study was to determine the relationship between the degree of immune suppression and systemic inflammation in patients shortly after admission to the ICU. Design: An observational study in two ICUs in the Netherlands. Methods: The capacity of blood leukocytes to produce cytokines upon stimulation with lipopolysaccharide (LPS) was measured in 77 patients on the first morning after ICU admission. Patients were divided in four groups based on quartiles of LPS stimulated tumor necrosis factor (TNF)-α release, reflecting increasing extents of immune suppression. 15 host response biomarkers indicative of aberrations in inflammatory pathways implicated in sepsis pathogenesis were measured in plasma. Results: A diminished capacity of blood leukocytes to produce TNF-α upon stimulation with LPS was accompanied by a correspondingly reduced ability to release of IL-1β and IL-6. Concurrently measured plasma concentrations of host response biomarkers demonstrated that the degree of reduction in TNF-α release by blood leukocytes was associated with increasing systemic inflammation, stronger endothelial cell activation, loss of endothelial barrier integrity and enhanced procoagulant responses. Conclusions: In patients admitted to the ICU the strongest immune suppression occurs in those who simultaneously display signs of stronger systemic inflammation. These findings may have relevance for the selection of patients eligible for administration of immune enhancing agents.peer-reviewe

Rectal microbiota are coupled with altered cytokine production capacity following community-acquired pneumonia hospitalization

Human studies describing the immunomodulatory role of the intestinal microbiota in systemic infections are lacking. Here, we sought to relate microbiota profiles from 115 patients with community-acquired pneumonia (CAP), both on hospital admission and following discharge, to concurrent circulating monocyte and neutrophil function. Rectal microbiota composition did not explain variation in cytokine responses in acute CAP (median 0%, IQR 0.0%-1.9%), but did one month following hospitalization (median 4.1%, IQR 0.0%-6.6%, p = 0.0035). Gene expression analysis of monocytes showed that undisrupted microbiota profiles following hospitalization were associated with upregulated interferon, interleukin-10, and G-protein-coupled-receptor-ligand-binding pathways. While CAP is characterized by profoundly distorted gut microbiota, the effects of these disruptions on cytokine responses and transcriptional profiles during acute infection were absent or modest. However, rectal microbiota were related to altered cytokine responses one month following CAP hospitalization, which may provide insights into potential mechanisms contributing to the high risk of recurrent infections following hospitalization.peer-reviewe

Enhancing sepsis biomarker development: key considerations from public and private perspectives.

Implementation of biomarkers in sepsis and septic shock in emergency situations, remains highly challenging. This viewpoint arose from a public-private 3-day workshop aiming to facilitate the transition of sepsis biomarkers into clinical practice. The authors consist of international academic researchers and clinician-scientists and industry experts who gathered (i) to identify current obstacles impeding biomarker research in sepsis, (ii) to outline the important milestones of the critical path of biomarker development and (iii) to discuss novel avenues in biomarker discovery and implementation. To define more appropriately the potential place of biomarkers in sepsis, a better understanding of sepsis pathophysiology is mandatory, in particular the sepsis patient's trajectory from the early inflammatory onset to the late persisting immunosuppression phase. This time-varying host response urges to develop time-resolved test to characterize persistence of immunological dysfunctions. Furthermore, age-related difference has to be considered between adult and paediatric septic patients. In this context, numerous barriers to biomarker adoption in practice, such as lack of consensus about diagnostic performances, the absence of strict recommendations for sepsis biomarker development, cost and resources implications, methodological validation challenges or limited awareness and education have been identified. Biomarker-guided interventions for sepsis to identify patients that would benefit more from therapy, such as sTREM-1-guided Nangibotide treatment or Adrenomedullin-guided Enibarcimab treatment, appear promising but require further evaluation. Artificial intelligence also has great potential in the sepsis biomarker discovery field through capability to analyse high volume complex data and identify complex multiparametric patient endotypes or trajectories. To conclude, biomarker development in sepsis requires (i) a comprehensive and multidisciplinary approach employing the most advanced analytical tools, (ii) the creation of a platform that collaboratively merges scientific and commercial needs and (iii) the support of an expedited regulatory approval process

Monocyte state 1 (MS1) cells in critically ill patients with sepsis or non-infectious conditions: association with disease course and host response

Background: Sepsis is a life-threatening condition arising from an aberrant host response to infection. Recent single-cell RNA sequencing investigations identified an immature bone-marrow-derived CD14+ monocyte phenotype with immune suppressive properties termed “monocyte state 1” (MS1) in patients with sepsis. Our objective was to determine the association of MS1 cell profiles with disease presentation, outcomes, and host response characteristics. Methods: We used the transcriptome deconvolution method (CIBERSORTx) to estimate the percentage of MS1 cells from blood RNA profiles of patients with sepsis admitted to the intensive care unit (ICU). We compared these profiles to ICU patients without infection and to healthy controls. Host response dysregulation was further studied by gene co-expression network and gene set enrichment analyses of blood leukocytes, and measurement of 15 plasma biomarkers indicative of pathways implicated in sepsis pathogenesis. Results: Sepsis patients (n = 332) were divided into three equally-sized groups based on their MS1 cell levels (low, intermediate, and high). MS1 groups did not differ in demographics or comorbidities. The intermediate and high MS1 groups presented with higher disease severity and more often had shock. MS1 cell abundance did not differ between survivors and non-survivors, or between patients who did or did not acquire a secondary infection. Higher MS1 cell percentages were associated with downregulation of lymphocyte-related and interferon response genes in blood leukocytes, with concurrent upregulation of inflammatory response pathways, including tumor necrosis factor signaling via nuclear factor-κB. Previously described sepsis host response transcriptomic subtypes showed different MS1 cell abundances, and MS1 cell percentages positively correlated with the “quantitative sepsis response signature” and “molecular degree of perturbation” scores. Plasma biomarker levels, indicative of inflammation, endothelial cell activation, and coagulation activation, were largely similar between MS1 groups. In ICU patients without infection (n = 215), MS1 cell percentages and their relation with disease severity, shock, and host response dysregulation were highly similar to those in sepsis patients. Conclusions: High MS1 cell percentages are associated with increased disease severity and shock in critically ill patients with sepsis or a non-infectious condition. High MS1 cell abundance likely indicates broad immune dysregulation, entailing not only immunosuppression but also anomalies reflecting exaggerated inflammatory responses. Graphical abstract: (Figure presented.

Association between age and the host response in critically ill patients with sepsis

Background: The association of ageing with increased sepsis mortality is well established. Nonetheless, current investigations on the influence of age on host response aberrations are largely limited to plasma cytokine levels while neglecting other pathophysiological sepsis domains like endothelial cell activation and function, and coagulation activation. The primary objective of this study was to gain insight into the association of ageing with aberrations in key host response pathways and blood transcriptomes in sepsis.Methods: We analysed the clinical outcome (n=1952), 16 plasma biomarkers providing insight in deregulation of specific pathophysiological domains (n=899), and blood leukocyte transcriptomes (n=488) of sepsis patients stratified according to age decades. Blood transcriptome results were validated in an independent sepsis cohort and compared with healthy individuals. se.Results: Older age was associated with increased mortality independent of comorbidities and disease severity. Ageing was associated with lower endothelial cell activation and dysfunction, and similar inflammation and coagulation activation, despite higher disease severity scores. Blood leukocytes of patients≥70 years, compared to patients<50 years, showed decreased expression of genes involved in cytokine signaling, and innate and adaptive immunity, and increased expression of genes involved in hemostasis and endothelial cell activation. The diminished expression of gene pathways related to innate immunity and cytokine signaling in subjects≥70 years was sepsis-induced, as healthy subjects≥70 years showed enhanced expression of these pathways compared to healthy individuals<50 years.Conclusions: This study provides novel evidence that older age is associated with relatively mitigated sepsis-induced endothelial cell activation and dysfunction, and a blood leukocyte transcriptome signature indicating impaired innate immune and cytokine signaling. These data suggest that age should be considered in patient selection in future sepsis trials targeting the immune system and/or the endothelial cell response.peer-reviewe

Intracellular pyruvate levels positively correlate with cytokine production capacity in tolerant monocytes from patients with pneumonia

Background: Community-acquired pneumonia (CAP) is responsible for a high morbidity and mortality worldwide. Monocytes are essential for pathogen recognition and the initiation of an innate immune response. Immune cells induce intracellular glycolysis upon activation to support several functions. Objective: To obtain insight in the metabolic profile of blood monocytes during CAP, with a focus on glycolysis and branching metabolic pathways, and to determine a possible association between intracellular metabolite levels and monocyte function. Methods: Monocytes were isolated from blood of patients with CAP within 24 h of hospital admission and from control subjects matched for age, sex and chronic comorbidities. Changes in glycolysis, oxidative phosphorylation (OXPHOS), tricarboxylic acid (TCA) cycle and the pentose phosphate pathway were investigated through RNA sequencing and metabolomics measurements. Monocytes were stimulated ex vivo with lipopolysaccharide (LPS) to determine their capacity to produce tumor necrosis factor (TNF), interleukin (IL)-1β and IL-10. Results: 50 patients with CAP and 25 non-infectious control subjects were studied. When compared with control monocytes, monocytes from patients showed upregulation of many genes involved in glycolysis, including PKM, the gene encoding pyruvate kinase, the rate limiting enzyme for pyruvate production. Gene set enrichment analysis of OXPHOS, the TCA cycle and the pentose phosphate pathway did not reveal differences between monocytes from patients and controls. Patients' monocytes had elevated intracellular levels of pyruvate and the TCA cycle intermediate α-ketoglutarate. Monocytes from patients were less capable of producing cytokines upon LPS stimulation. Intracellular pyruvate (but not α-ketoglutarate) concentrations positively correlated with IL-1β and IL-10 levels released by patients' (but not control) monocytes upon exposure to LPS. Conclusion: These results suggest that elevated intracellular pyruvate levels may partially maintain cytokine production capacity of hyporesponsive monocytes from patients with CAP.peer-reviewe