The immunology of sepsis

Clinicopathological Correlation of Microbial Keratitis and Ahead: Is There a Corneal Sepsis?

Microbial, infectious keratitis is a relevant indication for penetrating keratoplasty. The requirement for transplantation results in histopathological examination of the entire thickness of the cornea. Although the clinical diagnosis is not always possible to confirm, pathology can support diagnostic evidence of clinical presentation and pathogenesis. This is achieved with multiple methods from cytology, histochemistry, immunohistology, molecular pathology and in rare cases electron microscopy. These allow tissue-based detection of previous and parallel diseases and the responsible pathogens. The failure of satisfactory clinicopathological correlation raises the question whether a suspected pathogen was not ultimately responsible for destroyed corneal tissue. The pathogenesis of keratitis requiring transplantation is not yet completely understood, also on the experimental level. The development of such a keratitis can lead to a clinical symptomatology which can be described as "threatening organ dysfunction", a term used in sepsis research. Considering recent literature, possible correlations between sepsis and microbial keratitis and their relation to histopathology are discussed.

Diagnostic and Predictive Values of Ferroptosis-Related Genes in Child Sepsis

Background

Early diagnosis of sepsis in children was essential to reducing mortality. This study aimed to explore the value of ferroptosis-related genes in children with sepsis.

Methods

We screened the septic children microarray dataset from the GEO database and analyzed the ferroptosis-related differentially expressed genes (DEGs). A functional analysis of ferroptosis-related DEGs was performed. The protein–protein interaction network was used to identify hub genes. We explored the immune landscape of sepsis and controls. The value of hub genes in diagnosing sepsis was tested in the training (GSE26440) and validation sets (GSE13904), and ELISA was used to verify their diagnostic value in children with sepsis in our hospital.

Results

A total of 2,103 DEGs in GSE26440 were obtained, of which ferroptosis-related DEGs were 34. Enrichment analysis showed significant enrichment in the ferroptosis and hypoxia pathways (i.e., HIF-1 pathway). The top three genes (HMOX1, MAPK14, TLR4) were selected as hub genes. Immunological analysis suggested that 10 cell types (i.e., CD8/CD4 T cells) were lower in sepsis. Immune checkpoint-related genes CD274 (PD-L1), HAVCR2 (TIM3), and SIGLEC15 were overexpressed in sepsis. The AUROC for the diagnosis of sepsis for HMOX1 and TLR4 ranged from 0.77 to 0.81, while the AUROC of MAPK14 reached 0.935 and 0.941 in the training and validation sets. Serum ELISA results of HMOX1 and TLR4 showed no significant difference in differentiating sepsis. The AUROC of MAPK14 was 0.877. When the diagnostic threshold was 74.852 ng/ml, the sensitivity and specificity were 0.906 and 0.719, respectively.

Conclusion

Ferroptosis-related gene MAPK14 is of considerable value in the early diagnosis of sepsis in children.

Potential of circulating lncRNA CASC2 as a biomarker in reflecting the inflammatory cytokines, multi-organ dysfunction, disease severity, and mortality in sepsis patients

BACKGROUND

Long noncoding RNA (lncRNA) cancer susceptibility candidate gene 2 (CASC2) inhibits inflammation and multi-organ dysfunction in various ways. The present study was intended to explore the potency of blood lncRNA CASC2 as a biomarker for sepsis management.

METHODS

Totally, 184 sepsis patients and 30 healthy controls were enrolled. The reverse transcription-quantitative polymerase chain reaction was used to detect lncRNA CASC2 expression in peripheral blood mononuclear cell samples from the subjects. Mortality during 28 days was recorded in sepsis patients.

RESULTS

LncRNA CASC2 was decreased in sepsis patients [median (interquartile range [IQR]): 0.473 (0.241-0.773)] by comparison to healthy controls [median (IQR): 1.019 (0.676-1.685)] (p < 0.001). In sepsis patients, lncRNA CASC2 was negatively correlated with Acute Physiology and Chronic Health Evaluation II (APACHE II) (p = 0.001), Sequential Organ Failure Assessment (SOFA) (p < 0.001), SOFA-respiratory system (p = 0.010), SOFA-coagulation (p = 0.020), SOFA-liver (p = 0.019), and SOFA-renal (p = 0.010) scores, but was not related to SOFA-nervous (p = 0.466) and SOFA-cardio vascular system (p = 0.059) scores. Additionally, lncRNA CASC2 was negatively related to tumor necrosis factor-α (p = 0.024), interleukin (IL)-1β (p = 0.013), and IL-17A (p = 0.002), but was not linked to IL-6 (p = 0.112) or IL-10 (p = 0.074). Furthermore, lncRNA CASC2 was lower in sepsis deaths [median (IQR): 0.286 (0.166-0.475)] than in survivors [median (IQR): 0.534 (0.296-0.811)] (p < 0.001). Simultaneously, Kaplan-Meier (KM) curve analysis also observed that lncRNA CASC2 was inversely related to accumulating mortality in sepsis patients (p = 0.003). While lncRNA CASC2 could independently predict lower mortality risk.

CONCLUSION

Circulating lncRNA CASC2 inadequacy indicates the release of inflammatory cytokines, severe multi-organ injuries, and increased mortality in sepsis patients.

Effect of intravenous clarithromycin in patients with sepsis, respiratory and multiple organ dysfunction syndrome: a randomized clinical trial

Background

Clarithromycin may act as immune-regulating treatment in sepsis and acute respiratory dysfunction syndrome. However, clinical evidence remains inconclusive. We aimed to evaluate whether clarithromycin improves 28-day mortality among patients with sepsis, respiratory and multiple organ dysfunction syndrome.

Methods

We conducted a multicenter, randomized, clinical trial in patients with sepsis. Participants with ratio of partial oxygen pressure to fraction of inspired oxygen less than 200 and more than 3 SOFA points from systems other than the respiratory function were enrolled between December 2017 and September 2019. Patients were randomized to receive 1 gr of clarithromycin or placebo intravenously once daily for 4 consecutive days. The primary endpoint was 28-day all-cause mortality. Secondary outcomes were 90-day mortality; sepsis response (defined as at least 25% decrease in SOFA score by day 7); sepsis recurrence; and differences in peripheral blood cell populations and leukocyte transcriptomics.

Results

Fifty-five patients were allocated to each arm. By day 28, 27 (49.1%) patients in the clarithromycin and 25 (45.5%) in the placebo group died (risk difference 3.6% [95% confidence interval (CI) − 15.7 to 22.7]; P = 0.703, adjusted OR 1.03 [95%CI 0.35–3.06]; P = 0.959). There were no statistical differences in 90-day mortality and sepsis response. Clarithromycin was associated with lower incidence of sepsis recurrence (OR 0.21 [95%CI 0.06–0.68]; P = 0.012); significant increase in monocyte HLA-DR expression; expansion of non-classical monocytes; and upregulation of genes involved in cholesterol homeostasis. Serious and non-serious adverse events were equally distributed.

Conclusions

Clarithromycin did not reduce mortality among patients with sepsis with respiratory and multiple organ dysfunction. Clarithromycin was associated with lower sepsis recurrence, possibly through a mechanism of immune restoration.

Clinical trial registration clinicaltrials.gov identifier NCT03345992 registered 17 November 2017; EudraCT 2017-001056-55.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04055-4.

Clinical Value of Prognostic Nutritional Index and Neutrophil-to-Lymphocyte Ratio in Prediction of the Development of Sepsis-Induced Kidney Injury

Background

Sepsis-related acute kidney injury (S-AKI) is a frequent complication of hospitalized patients and is linked to increased morbidity and mortality. Early prediction and detection remain conducive to optimizing treatment strategies and limiting further insults. This study was aimed at evaluating the potential predictive value of the combined prognostic nutrition index (PNI) and neutrophil-to-lymphocyte ratio (NLR) to predict the risk of AKI in septic patients.

Methods

In this retrospective study, 1238 adult patients with sepsis who were admitted to the First Affiliated Hospital of Xi'an Jiaotong University from January 2015 to June 2021 were enrolled. Patients were divided into two groups: the non-AKI group (n = 731) and the S-AKI group (n = 507). Univariate and multivariate logistic regression analyses were performed to screen the independent predictive factors of S-AKI. A receiver operating characteristic (ROC) curve was used to evaluate the predictive value of PNI and NLR.

Results

Multivariate logistic regression analysis indicated that age, chronic liver disease, cardiovascular disease, respiratory rate (RR), white blood cells (WBC), blood urea nitrogen (BUN), creatinine (CRE), international normalized ratio (INR), neutrophil-to-lymphocyte ratio (NLR), and prognostic nutrition index (PNI) were independent prognostic factors of S-AKI. In the three models, the adjusted OR of PNI for S-AKI was 0.802 (0.776-0.829), 0.801 (0.775-0.829), and 0.717 (0.666-0.772), while that of NLR was 1.094 (1.078-1.111), 1.097 (1.080-1.114), and 1.044 (1.016-1.072), respectively. In addition, the area under the ROC curve of the PNI plus NLR group was significantly greater than that of the CRE plus BUN group (0.801, 95% CI: 0.775-0.827 vs. 0.750, 95% CI: 0.722-0.778, respectively; P < 0.001).

Conclusions

PNI and NLR have been identified as readily available and independent predictors in septic patients with S-AKI. PNI, in combination with NLR, is of vital significance for early warning and efficient intervention of S-AKI and is superior to combined BUN and CRE.

Necroptosis, Pyroptosis, Ferroptosis in Sepsis and Treatment

ABSTRACT

As a global major health problem and a leading cause of death, sepsis is defined as a failure of homeostasis, which is mainly initiated by an infection and followed by sustained excessive inflammation until immune suppression. Despite advances in the identification and management of clinical sepsis, morbidity, and mortality remain high. In addition, clinical trials have failed to yield promising results. In recent years, the mechanism of regulated cell death (RCD) in sepsis has attracted more and more attention, because these dying cells could release a large number of danger signals which contribute to inflammatory responses and exacerbation of sepsis, providing a new direction for us to make treatment strategy. Here we summarize mechanisms of several forms of RCD in sepsis including necroptosis, pyroptosis, ferroptosis. In conclusion, targeting RCD is considered a promising approach to treat sepsis.

Advances in Immune Monitoring Approaches for Sepsis-Induced Immunosuppression

Sepsis represents a life-threatening organ dysfunction due to an aberrant host response. Of note is that majority of patients have experienced a severe immune depression during and after sepsis, which is significantly correlated with the occurrence of nosocomial infection and higher risk of in-hospital death. Nevertheless, the clinical sign of sepsis-induced immune paralysis remains highly indetectable and ambiguous. Given that, specific yet robust biomarkers for monitoring the immune functional status of septic patients are of prominent significance in clinical practice. In turn, the stratification of a subgroup of septic patients with an immunosuppressive state will greatly contribute to the implementation of personalized adjuvant immunotherapy. In this review, we comprehensively summarize the mechanism of sepsis-associated immunosuppression at the cellular level and highlight the recent advances in immune monitoring approaches targeting the functional status of both innate and adaptive immune responses.

Transcriptome-Based Dissection of Intracranial Aneurysms Unveils an “Immuno-Thermal” Microenvironment and Defines a Pathological Feature-Derived Gene Signature for Risk Estimation

Immune inflammation plays an essential role in the formation and rupture of intracranial aneurysm (IA). However, the current limited knowledge of alterations in the immune microenvironment of IA has hampered the mastery of pathological mechanisms and technological advances, such as molecular diagnostic and coated stent-based molecular therapy. In this study, seven IA datasets were enrolled from the GEO database to decode the immune microenvironment and relevant biometric alterations. The ssGSEA algorithm was employed for immune infiltration assessment. IAs displayed abundant immune cell infiltration, activated immune-related pathways, and high expression of immune-related genes. Several immunosuppression cells and genes were also coordinately upregulated in IAs. Five immune-related hub genes, including CXCL10, IL6, IL10, STAT1, and VEGFA, were identified from the protein-protein interaction network and further detected at the protein level. CeRNA networks and latent drugs targeting the hub genes were predicted for targeted therapy reference. Two gene modules recognized via WCGNA were functionally associated with contractile smooth muscle loss and extracellular matrix metabolism, respectively. In blood datasets, a pathological feature-derived gene signature (PFDGS) for IA diagnosis and rupture risk prediction was established using machine learning. Patients with high PFDGS scores may possess adverse biological alterations and present with a high risk of morbidity or IA rupture, requiring more vigilance or prompt intervention. Overall, we systematically unveiled an “immuno-thermal” microenvironment characterized by co-enhanced immune activation and immunosuppression in IA, which provides a novel insight into molecular pathology. The PFDGS is a promising signature for optimizing risk surveillance and clinical decision-making in IA patients.

Is blood lymphocyte count a prognostic biomarker in Staphylococcus aureus bacteremia?

Lymphopenia is common in patients with sepsis and associated with mortality. Immune-stimulatory therapies likely to restore T-cells count and function are under investigation in sepsis. Our study aimed to assess whether lymphopenia is a reliable prognostic biomarker in Staphylococcus aureus bacteremia. We conducted an ancillary study of the prospective VIRSTA Study including 574 patients with S. aureus bacteremia in two tertiary care centers. Neither lymphocyte count at the onset nor lymphocyte change during the first 4 days was associated with 12-week mortality. These results highlight the importance of characterizing the immune profile of patients with sepsis according to the cause before investigating immunostimulatory therapies to restore lymphocyte proliferation and function.

Protective Effect of Poria Cocos Polysaccharides on Fecal Peritonitis-Induced Sepsis in Mice Through Inhibition of Oxidative Stress, Inflammation, Apoptosis, and Reduction of Treg Cells

This study was conducted to investigate the potential pharmacological effects of Poria cocos polysaccharides (PCPs) on fecal-induced peritonitis (FIP) mice. Consequently, the fecal peritonitis (FP)-induced septic mice with the higher levels of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), IL-1β, malondialdehyde (MDA), myeloperoxidase (MPO), histopathological lesion and bacterial burden, and lower levels of superoxide dismutase (SOD) and glutathione (GSH). Interestingly, PCP pre-treatment reduced inflammatory cytokines and oxidative stress in plasma and spleen and improved the resistance to FIP. Inflammatory infiltration and cell death in thymus or splenic tissue were alleviated with PCP pretreatment. Furthermore, Treg cells were moderated in the spleen with PCP pre-administration. In addition, PCP pretreatment downregulated Annexin-V in the thymus of FP-induced septic mice, and apoptosis of splenic cells was dose-dependent. In conclusion, PCPs have pharmacological and biological effects on FP-induced septic mice, and its molecular mechanism is related to antioxidative, anti-inflammation, anti-apoptosis, and the reduction of Treg activity in splenic cells.

Identification of Immune-Related Genes Concurrently Involved in Critical Illnesses Across Different Etiologies: A Data-Driven Analysis

Severe trauma and sepsis can lead to multiple organ dysfunction syndrome, which is a leading cause of death in intensive care units with mortality rates in excess of 50%. In addition to infection, the degree of immuno-inflammatory response also influences the outcome. The genomic changes observed after a variety of pathophysiological insults, such as trauma, sepsis, burns are similar, and consist of innate immune activation and adaptive immunity suppression. However, the characteristics of the shared mechanisms of aforementioned critical illnesses and the clinical relevance remain less explored. In the present study, we performed a data analysis to identify functional genes concurrently involved in critical illnesses across differing etiologies (trauma and sepsis derived from community-acquired pneumonia/abdominal source) and explored the shared signaling pathways these common genes involved in to gain insight into the underlying molecular mechanisms. A number of immune-related biological functions were found to be dysregulated in both trauma and sepsis in the present study, so we continued to identify immune-related common genes, profiled the immune cell proportion, and explored the relationships between them. The diagnostic and prognostic value of the immune-related common genes was also evaluated to address their potential clinical utilization as novel biomarkers. Notably, we identified a list of 14 immune-related genes concurrently dysregulated in trauma and sepsis showing favorable diagnostic value, among which S100P can predict prognosis of sepsis patients. Moreover, a spectrum of immune cell subsets including naïve B cells, CD8+ T cells, CD4+ memory resting T cells, activated NK cells, resting dendritic cells, plasma cells, Tregs, macrophages M0 and macrophages M1 was found to be concurrently dysregulated in both trauma and sepsis, and a close relation between above identified immune-related genes and immune cell subsets was observed. Our data-driven findings lay a foundation for future research to elucidate the pathophysiology regarding the aspect of inflammatory and immune response in critical illnesses, and suggest future studies focus on interpreting the function roles of the identified immune-related genes, as well as the reactive immune cell subsets.

Risk Factors and Outcome of Sepsis in Traumatic Patients and Pathogen Detection Using Metagenomic Next-Generation Sequencing

Objective

Sepsis, a life-threatening clinical syndrome, is a leading cause of mortality after experiencing multiple traumas. Once diagnosed with sepsis, patients should be given an appropriate empiric antimicrobial treatment followed by the specific antibiotic therapy based on blood culture due to its rapid progression to tissue damage and organ failure. In this study, we aimed to analyze the risk factors and outcome of sepsis in traumatic patients and to investigate the performance of metagenomic next-generation sequencing (mNGS) compared with standard microbiological diagnostics in post-traumatic sepsis.

Methods

The study included 528 patients with multiple traumas among which there were 142 cases with post-traumatic sepsis. Patients' demographic and clinical data were recorded. The outcome measures included mortality during the emergency intensive care unit (EICU), EICU length of stay (LOS), all-cause 28-day mortality, and total ventilator days in 28 days after admission. A total of 89 blood samples from 89 septic patients underwent standard microbiological blood cultures and 89 samples of peripheral blood (n = 21), wound secretion (n = 41), bronchoalveolar lavage fluid (BALF) (19), ascites (n = 5), and sputum (n = 3) underwent mNGS. Pathogen detection was compared between standard microbiological blood cultures and mNGS.

Results

The sepsis group and non-sepsis group exhibited significant differences regarding shock on admission, blood transfusion, mechanical ventilation, body temperature, heart rate, WBC count, neutrophil count, hematocrit, urea nitrogen, creatinine, CRP, D-D dimer, PCT, scores of APACHE II, sequential organ failure assessment (SOFA), and Injury Severity Score (ISS) on admission to the EICU, and Multiple Organ Dysfunction Syndromes (MODS) (P < 0.05). Multivariate logistic regression analysis showed that scores of APACHE II, SOFA, and ISS on admission, and MODS were independent risk factors for the occurrence of sepsis in patients with multiple traumas. The 28-day mortality was higher in the sepsis group than in the non-sepsis group (45.07% vs. 19.17%, P < 0.001). The mortality during the EICU was higher in the sepsis group than in the non-sepsis group (P=0.002). The LOS in the EICU in the sepsis group was increased compared with the non-sepsis group (P=0.004). The total ventilator days in 28 days after admission in the sepsis group was increased compared with the non-sepsis group (P < 0.001). Multivariate logistic regression analysis showed that septic shock, APACHE II score on admission, SOFA score, and MODS were independent risk factors of death for patients with post-traumatic sepsis. The positive detection rate of mNGS was 91.01% (81/89), which was significantly higher than that of standard microbiological blood cultures (39.33% (35/89)). Standard microbiological blood cultures and mNGS methods demonstrated double positive results in 33 (37.08%) specimens and double-negative results in 8 (8.99%) specimens, while 46 (51.69%) samples and 2 (2.25%) samples had positive results only with mNGS or culture alone, respectively.

Conclusion

Our study identifies risk factors for the incidence and death of sepsis in traumatic patients and shows that mNGS may serve as a better diagnostic tool for the identification of pathogens in post-traumatic sepsis than standard microbiological blood cultures.

Identification of Nine mRNA Signatures for Sepsis Using Random Forest

Sepsis has high fatality rates. Early diagnosis could increase its curating rates. There were no reliable molecular biomarkers to distinguish between infected and uninfected patients currently, which limit the treatment of sepsis. To this end, we analyzed gene expression datasets from the GEO database to identify its mRNA signature. First, two gene expression datasets (GSE154918 and GSE131761) were downloaded to identify the differentially expressed genes (DEGs) using Limma package. Totally 384 common DEGs were found in three contrast groups. We found that as the condition worsens, more genes were under disorder condition. Then, random forest model was performed with expression matrix of all genes as feature and disease state as label. After which 279 genes were left. We further analyzed the functions of 279 important DEGs, and their potential biological roles mainly focused on neutrophil threshing, neutrophil activation involved in immune response, neutrophil-mediated immunity, RAGE receptor binding, long-chain fatty acid binding, specific granule, tertiary granule, and secretory granule lumen. Finally, the top nine mRNAs (MCEMP1, PSTPIP2, CD177, GCA, NDUFAF1, CLIC1, UFD1, SEPT9, and UBE2A) associated with sepsis were considered as signatures for distinguishing between sepsis and healthy controls. Based on 5-fold cross-validation and leave-one-out cross-validation, the nine mRNA signature showed very high AUC.

The Human-Restricted Isoform of the α7 nAChR, CHRFAM7A: A Double-Edged Sword in Neurological and Inflammatory Disorders

CHRFAM7A is a relatively recent and exclusively human gene arising from the partial duplication of exons 5 to 10 of the α7 neuronal nicotinic acetylcholine receptor subunit (α7 nAChR) encoding gene, CHRNA7. CHRNA7 is related to several disorders that involve cognitive deficits, including neuropsychiatric, neurodegenerative, and inflammatory disorders. In extra-neuronal tissues, α7nAChR plays an important role in proliferation, differentiation, migration, adhesion, cell contact, apoptosis, angiogenesis, and tumor progression, as well as in the modulation of the inflammatory response through the “cholinergic anti-inflammatory pathway”. CHRFAM7A translates the dupα7 protein in a multitude of cell lines and heterologous systems, while maintaining processing and trafficking that are very similar to the full-length form. It does not form functional ion channel receptors alone. In the presence of CHRNA7 gene products, dupα7 can assemble and form heteromeric receptors that, in order to be functional, should include at least two α7 subunits to form the agonist binding site. When incorporated into the receptor, in vitro and in vivo data showed that dupα7 negatively modulated α7 activity, probably due to a reduction in the number of ACh binding sites. Very recent data in the literature report that the presence of the duplicated gene may be responsible for the translational gap in several human diseases. Here, we will review the studies that have been conducted on CHRFAM7A in different pathologies, with the intent of providing evidence regarding when and how the expression of this duplicated gene may be beneficial or detrimental in the pathogenesis, and eventually in the therapeutic response, to CHRNA7-related neurological and non-neurological diseases.

Network pharmacology prediction and molecular docking-based strategy to explore the potential mechanism of Huanglian Jiedu Decoction against sepsis

BACKGROUND

Huanglian Jiedu Decoction (HLJDD) is a classical herbal formula with potential efficacy in the treatment of sepsis. However, the main components and potential mechanisms of HLJDD remain unclear. This study aims to initially clarify the potential mechanism of HLJDD in the treatment of sepsis based on network pharmacology and molecular docking techniques.

METHODS

The principal components and corresponding protein targets of HLJDD were searched on TCMSP, BATMAN-TCM and ETCM and the compound-target network was constructed by Cytoscape3.8.2. Sepsis targets were searched on OMIM and DisGeNET databases. The intersection of compound target and disease target was obtained and the coincidence target was imported into STRING database to construct a PPI network. We further performed GO and KEGG enrichment analysis on the targets. Finally, molecular docking study was approved for the core target and the active compound.

RESULTS

There are 257 nodes and 792 edges in the component target network. The compounds with a higher degree value are quercetin, kaempferol, and wogonin. The protein with a higher degree in the PPI network is JUN, RELA, TNF. GO and KEGG analysis showed that HLJDD treatment of sepsis mainly involves positive regulation of transcription from RNA polymerase II promoter, negative regulation of apoptosis process, response to hypoxia and other biological processes. The signaling pathways mainly include PI3K-AKT, MAPK, TNF signaling pathway. The molecular docking results showed that quercetin, kaempferol and wogonin have higher affinity with JUN, RELA and TNF.

CONCLUSION

This study reveals the active ingredients and potential molecular mechanism of HLJDD in the treatment of sepsis, and provides a reference for subsequent basic research.

High levels of monocytic myeloid-derived suppressor cells are associated with favorable outcome in patients with pneumonia and sepsis with multi-organ failure

Background

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells with immunosuppressive functions sub-classified into monocytic and polymorphonuclear MDSCs (M-MDSCs and PMN-MDSCs). Clinical studies reported increased levels of MDSCs that were associated with poor outcome in sepsis patients. Since sepsis patients exhibit signs of inflammation and immunosuppression, MDSCs may provide benefit by dampening deleterious inflammation in some patients. To test this hypothesis, we measured MDSCs in critically ill sepsis patients with pneumonia and multi-organ dysfunctions and a high likelihood of death.

Methods

This was a prospective multicenter observational cohort study performed in eight ICUs in Athens and Thessaloniki, Greece, enrolling critically ill patients with pneumonia and sepsis with multi-organ dysfunctions. A flow cytometry approach using blood collected at study inclusion in tubes containing lyophilized antibodies combined to unsupervised clustering was developed to quantify M-MDSCs and PMN-MDSCs.

Results

Forty-eight patients were included, of whom 34 died within 90 days. At study inclusion, M-MDSCs and PMN-MDSCs were increased in sepsis patients when compared to healthy subjects (3.07% vs 0.96% and 22% vs 2.1% of leukocytes, respectively; p < 10^–4). Increased PMN-MDSCs were associated with secondary infections (p = 0.024) and new sepsis episodes (p = 0.036). M-MDSCs were more abundant in survivors than in patients who died within 28 days (p = 0.028). Stratification of patients according to M-MDSC levels revealed that high levels of M-MDSC were associated with reduced 90-day mortality (high vs low M-MDSCs: 47% vs 84% mortality, p = 0.003, hazard ratio [HR] = 3.2, 95% CI 1.4–7.2). Combining high M-MDSC levels with low Acute Physiology and Chronic Health Evaluation (APACHE) II score improved patient stratification (M-MDSCs^high/APACHE II^low vs M-MDSCs^low/APACHE II^low: 20% vs 80% 90-day mortality, p = 0.0096, HR = 7.2, 95% CI 1.6–32). In multivariate analyses high M-MDSCs remained correlated with improved survival in patients with low APACHE II score (p = 0.05, HR = 5.26, 95% CI 1.0–27.8).

Conclusion

This is the first study to associate high levels of M-MDSCs with improved survival in sepsis patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40635-022-00431-0.

Spatiotemporal Adaptations of Macrophage and Dendritic Cell Development and Function

Macrophages and conventional dendritic cells (cDCs) are distributed throughout the body, maintaining tissue homeostasis and tolerance to self and orchestrating innate and adaptive immunity against infection and cancer. As they complement each other, it is important to understand how they cooperate and the mechanisms that integrate their functions. Both are exposed to commensal microbes, pathogens, and other environmental challenges that differ widely among anatomical locations and over time. To adjust to these varying conditions, macrophages and cDCs acquire spatiotemporal adaptations (STAs) at different stages of their life cycle that determine how they respond to infection. The STAs acquired in response to previous infections can result in increased responsiveness to infection, termed training, or in reduced responses, termed paralysis, which in extreme cases can cause immunosuppression. Understanding the developmental stage and location where macrophages and cDCs acquire their STAs, and the molecular and cellular players involved in their induction, may afford opportunities to harness their beneficial outcomes and avoid or reverse their deleterious effects. Here we review our current understanding of macrophage and cDC development, life cycle, function, and STA acquisition before, during, and after infection. We propose a unified framework to explain how these two cell types adjust their activities to changing conditions over space and time to coordinate their immunosurveillance functions. Expected final online publication date for the Annual Review of Immunology, Volume 40 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Omics of endothelial cell dysfunction in sepsis

During sepsis, defined as life-threatening organ dysfunction due to dysregulated host response to infection, systemic inflammation activates endothelial cells and initiates a multifaceted cascade of pro-inflammatory signaling events, resulting in increased permeability and excessive recruitment of leukocytes. Vascular endothelial cells share many common properties but have organ-specific phenotypes with unique structure and function. Thus, therapies directed against endothelial cell phenotypes are needed to address organ-specific endothelial cell dysfunction. Omics allow for the study of expressed genes, proteins and/or metabolites in biological systems and provide insight on temporal and spatial evolution of signals during normal and diseased conditions. Proteomics quantifies protein expression, identifies protein-protein interactions and can reveal mechanistic changes in endothelial cells that would not be possible to study via reductionist methods alone. In this review, we provide an overview of how sepsis pathophysiology impacts omics with a focus on proteomic analysis of mouse endothelial cells during sepsis/inflammation and its relationship with the more clinically relevant omics of human endothelial cells. We discuss how omics has been used to define septic endotype signatures in different populations with a focus on proteomic analysis in organ-specific microvascular endothelial cells during sepsis or septic-like inflammation. We believe that studies defining septic endotypes based on proteomic expression in endothelial cell phenotypes are urgently needed to complement omic profiling of whole blood and better define sepsis subphenotypes. Lastly, we provide a discussion of how in silico modeling can be used to leverage the large volume of omics data to map response pathways in sepsis.

Inhibiting KDM6A Demethylase Represses Long Non-Coding RNA Hotairm1 Transcription in MDSC During Sepsis

Myeloid-derived suppressor cells (MDSCs) prolong sepsis by promoting immunosuppression. We reported that sepsis MDSC development requires long non-coding RNA Hotairm1 interactions with S100A9. Using a mouse model that simulates the immunobiology of sepsis, we find that histone demethylase KDM6A promotes Hotairm1 transcription by demethylating transcription repression H3K27me3 histone mark. We show that chemical targeting of KDM6A by GSK-J4 represses Hotairm1 transcription, which coincides with decreases in transcription activation H3K4me3 histone mark and transcription factor PU.1 binding to the Hotairm1 promoter. We further show that immunosuppressive IL-10 cytokine promotes KDM6A binding at the Hotairm1 promoter. IL-10 knockdown repletes H3K27me3 and reduces Hotairm1 transcription. GSK-J4 treatment also relocalizes nuclear S100A9 protein to the cytosol. To support translation to human sepsis, we demonstrate that inhibiting H3K27me3 demethylation by KDM6A ex vivo in MDSCs from patients with protracted sepsis decreases Hotairm1 transcription. These findings suggest that epigenetic targeting of MDSCs in human sepsis might resolve post-sepsis immunosuppression and improve sepsis survival.

Machine learning models to predict in-hospital mortality in septic patients with diabetes

BACKGROUND

Sepsis is a leading cause of morbidity and mortality in hospitalized patients. Up to now, there are no well-established longitudinal networks from molecular mechanisms to clinical phenotypes in sepsis. Adding to the problem, about one of the five patients presented with diabetes. For this subgroup, management is difficult, and prognosis is difficult to evaluate.

METHODS

From the three databases, a total of 7,001 patients were enrolled on the basis of sepsis-3 standard and diabetes diagnosis. Input variable selection is based on the result of correlation analysis in a handpicking way, and 53 variables were left. A total of 5,727 records were collected from Medical Information Mart for Intensive Care database and randomly split into a training set and an internal validation set at a ratio of 7:3. Then, logistic regression with lasso regularization, Bayes logistic regression, decision tree, random forest, and XGBoost were conducted to build the predictive model by using training set. Then, the models were tested by the internal validation set. The data from eICU Collaborative Research Database (n = 815) and dtChina critical care database (n = 459) were used to test the model performance as the external validation set.

RESULTS

In the internal validation set, the accuracy values of logistic regression with lasso regularization, Bayes logistic regression, decision tree, random forest, and XGBoost were 0.878, 0.883, 0.865, 0.883, and 0.882, respectively. Likewise, in the external validation set 1, lasso regularization = 0.879, Bayes logistic regression = 0.877, decision tree = 0.865, random forest = 0.886, and XGBoost = 0.875. In the external validation set 2, lasso regularization = 0.715, Bayes logistic regression = 0.745, decision tree = 0.763, random forest = 0.760, and XGBoost = 0.699.

CONCLUSION

The top three models for internal validation set were Bayes logistic regression, random forest, and XGBoost, whereas the top three models for external validation set 1 were random forest, logistic regression, and Bayes logistic regression. In addition, the top three models for the external validation set 2 were decision tree, random forest, and Bayes logistic regression. Random forest model performed well with the training and three validation sets. The most important features are age, albumin, and lactate.

Mannose-binding lectin gene polymorphism and the susceptibility of sepsis: A meta-analysis

Objective

To assess the association between the Mannose-binding lectin (MBL) gene polymorphism and the susceptibility to sepsis using a meta-analysis.

Methods

The publications were searched on PubMed, Embase, and Web of Science databases up to December 1, 2019 for relevant literature.

Results

A total of 32 studies (21 adult and 11 pediatric studies) were selected for analysis. Overall, in the three models of MBL +54 A/B gene polymorphisms, namely the dominant model BB + AB vs. AA ( p = 0.03), the recessive model BB vs. AB + AA ( p < 0.00001), and the allele model B vs. A ( p = 0.04), MBL +54 A/B was significantly related to the risk of sepsis. In the adult group, the MBL A/O gene polymorphism was associated with the risk of sepsis in the dominant model AO + OO vs. AA ( p = 0.006) as well as in the allele model O vs. A ( p = 0.04). The MBL +54 A/B gene polymorphism was significantly related to the risk of sepsis in the recessive model and, therefore, may increase the risk of sepsis. In the pediatric group, no polymorphic loci were significantly associated with sepsis in any of the three models. The results of the publication bias test demonstrated no publication bias in an unadjusted estimate of the relationship between MBL A/O and −211Y/X gene polymorphism and sepsis.

Conclusions

The polymorphisms of MBL that are related to the occurrence of sepsis are primarily A/O and +54 A/B, while −221Y/X and −550H/L have no clear relationship with the susceptibility of sepsis in various age groups or different models.

Construction and validation of a robust prognostic model based on immune features in sepsis

Purpose

Sepsis, with life-threatening organ failure, is caused by the uncontrolled host response to infection. Immune response plays an important role in the pathophysiology of sepsis. Immune-related genes (IRGs) are promising novel biomarkers that have been used to construct the diagnostic and prognostic model. However, an IRG prognostic model used to predict the 28-day mortality in sepsis was still limited. Therefore, the study aimed to develop a prognostic model based on IRGs to identify patients with high risk and predict the 28-day mortality in sepsis. Then, we further explore the circulating immune cell and immunosuppression state in sepsis.

Materials and methods

The differentially expressed genes (DEGs), differentially expressed immune-related genes (DEIRGs), and differentially expressed transcription factors (DETFs) were obtained from the GEO, ImmPort, and Cistrome databases. Then, the TFs-DEIRGs regulatory network and prognostic prediction model were constructed by Cox regression analysis and Pearson correlation analysis. The external datasets also validated the reliability of the prognostic model. Based on the prognostic DEIRGs, we developed a nomogram and conducted an independent prognosis analysis to explore the relationship between DEIRGs in the prognostic model and clinical features in sepsis. Besides, we further evaluate the circulating immune cells state in sepsis.

Results

A total of seven datasets were included in our study. Among them, GSE65682 was identified as a discovery cohort. The results of GSEA showed that there is a significant correlation between sepsis and immune response. Then, based on a P value <0.01, 69 prognostic DEIRGs were obtained and the potential molecular mechanisms of DEIRGs were also clarified. According to multivariate Cox regression analysis, 22 DEIRGs were further identified to construct the prognostic model and identify patients with high risk. The Kaplan-Meier survival analysis showed that high-risk groups have higher 28-day mortality than low-risk groups (P=1.105e-13). The AUC value was 0.879 which symbolized that the prognostic model had a better accuracy to predict the 28-day mortality. The external datasets also prove that the prognostic model had an excellent prediction value. Furthermore, the results of correlation analysis showed that patients with Mars1 might have higher risk scores than Mars2-4 (P=0.002). According to the previous study, Mars1 endotype was characterized by immunoparalysis. Thus, the sepsis patients in high-risk groups might exist the immunosuppression. Between the high-risk and low-risk groups, circulating immune cells types were significantly different, and risk score was significantly negatively correlated with naive CD4+ T cells (P=0.019), activated NK cells (P=0.0045), monocytes (P=0.0134), and M1 macrophages (P=0.0002).

Conclusions

Our study provides a robust prognostic model based on 22 DEIRGs which can predict 28-day mortality and immunosuppression status in sepsis. The higher risk score was positively associated with 28-day mortality and the development of immunosuppression. IRGs are a promising biomarker that might facilitate personalized treatments for sepsis.