Monocyte Differentiation and Heterogeneity: Inter-Subset and Interindividual Differences.

The three subsets of human monocytes, classical, intermediate, and nonclassical, show phenotypic heterogeneity, particularly in their expression of CD14 and CD16. This has enabled researchers to delve into the functions of each subset in the steady state as well as in disease. Studies have revealed that monocyte heterogeneity is multi-dimensional. In addition, that their phenotype and function differ between subsets is well established. However, it is becoming evident that heterogeneity also exists within each subset, between health and disease (current or past) states, and even between individuals. This realisation casts long shadows, impacting how we identify and classify the subsets, the functions we assign to them, and how they are examined for alterations in disease. Perhaps the most fascinating is evidence that, even in relative health, interindividual differences in monocyte subsets exist. It is proposed that the individual's microenvironment could cause long-lasting or irreversible changes to monocyte precursors that echo to monocytes and through to their derived macrophages. Here, we will discuss the types of heterogeneity recognised in monocytes, the implications of these for monocyte research, and most importantly, the relevance of this heterogeneity for health and disease.

Daily combined measurement of platelet count and presepsin concentration can predict in-hospital death of patients with severe coronavirus disease 2019 (COVID-19).

The purpose of this study was to classify patients with severe COVID-19 into more detailed risk groups using coagulation/fibrinolysis, inflammation/immune response, and alveolar/myocardial damage biomarkers, as well as to identify prognostic markers for these patients. These biomarkers were measured every day for eight intensive care unit days in 54 adult patients with severe COVID-19. The patients were classified into survivor (n = 40) and non-survivor (n = 14) groups. Univariate and multivariate analyses showed that the combined measurement of platelet count and presepsin concentrations may be the most valuable for predicting in-hospital death, and receiver operating characteristic curve analysis further confirmed this result (area under the curve = 0.832). Patients were consequently classified into three groups (high-, medium-, and low-risk) on the basis of their cutoff values (platelet count 53 × 103/µL, presepsin 714 pg/mL). The Kaplan-Meier curve for 90-day survival by each group showed that the 90-day mortality rate significantly increased as risk level increased (P < 0.01 by the log-rank test). Daily combined measurement of platelet count and presepsin concentration may be useful for predicting in-hospital death and classifying patients with severe COVID-19 into more detailed risk groups.

Presepsin as a diagnostic and prognostic biomarker of severe bacterial infections and COVID-19.

We aimed to develop presepsin as a marker of diagnosis of severe infections of either bacterial and viral origin. The derivation cohort was recruited from 173 hospitalized patients with acute pancreatitis or post-operative fever or infection suspicion aggravated by at least one sign of the quick sequential organ failure assessment (qSOFA). The first validation cohort was recruited from 57 admissions at the emergency department with at least one qSOFA sign and the second validation cohort from 115 patients with COVID-19 pneumonia. Presepsin was measured in plasma by the PATHFAST assay. Concentrations more than 350 pg/ml had sensitivity 80.2% for sepsis diagnosis in the derivation cohort (adjusted odds ratio 4.47; p < 0.0001). In the derivation cohort, sensitivity for 28-day mortality prognosis was 91.5% (adjusted odds ratio 6.82; p: 0.001). Concentrations above 350 pg/ml had sensitivity 93.3% for the diagnosis of sepsis in the first validation cohort; this was 78.3% in the second validation cohort of COVID-19 aiming at the early diagnosis of acute respiratory distress syndrome necessitating mechanical ventilation. The respective sensitivity for 28-day mortality was 85.7% and 92.3%. Presepsin may be a universal biomarker for the diagnosis of severe infections of bacterial origin and prediction of unfavorable outcome.

Histidine-rich glycoprotein as a novel predictive biomarker of postoperative complications in intensive care unit patients: a prospective observational study.

BACKGROUND: Decrease in histidine-rich glycoprotein (HRG) was reported as a cause of dysregulation of the coagulation-fibrinolysis and immune systems, leading to multi-organ failure, and it may be a biomarker for sepsis, ventilator-associated pneumonia, preeclampsia, and coronavirus disease 2019. However, the usefulness of HRG in perioperative management remains unclear. This study aimed to assess the usefulness of HRG as a biomarker for predicting postoperative complications. METHODS: This was a single-center, prospective, observational study of 150 adult patients who were admitted to the intensive care unit after surgery. Postoperative complications were defined as those having a grade II or higher in the Clavien-Dindo classification, occurring within 7 days after surgery. The primary outcome was HRG levels in the patients with and without postoperative complications. The secondary outcome was the ability of HRG, white blood cell, C-reactive protein, procalcitonin, and presepsin to predict postoperative complications. Data are presented as number and median (interquartile range). RESULTS: The incidence of postoperative complications was 40%. The HRG levels on postoperative day 1 were significantly lower in patients who developed postoperative complications (n = 60; 21.50 [18.12-25.74] µg/mL) than in those who did not develop postoperative complications (n = 90; 25.46 [21.05-31.63] µg/mL). The Harrell C-index scores for postoperative complications were HRG, 0.65; white blood cell, 0.50; C-reactive protein, 0.59; procalcitonin, 0.73; and presepsin, 0.73. HRG was independent predictor of postoperative complications when adjusted for age, the presence of preoperative cardiovascular comorbidities, American Society of Anesthesiologists Physical Status Classification, operative time, and the volume of intraoperative bleeding (adjusted hazard ratio = 0.94; 95% confidence interval, 0.90-0.99). CONCLUSIONS: The HRG levels on postoperative day 1 could predict postoperative complications. Hence, HRG may be a useful biomarker for predicting postoperative complications.

Single cell RNA-seq resolution revealed CCR1+/SELL+/XAF+ CD14 monocytes mediated vascular endothelial cell injuries in Kawasaki disease and COVID-19.

INTRODUCTION: The COVID-19 pandemic provide the opportunities to explore the numerous similarities in clinical symptoms with Kawasaki disease (KD), including severe vasculitis. Despite this, the underlying mechanisms of vascular injury in both KD and COVID-19 remain elusive. To identify these mechanisms, this study employs single-cell RNA sequencing to explore the molecular mechanisms of immune responses in vasculitis, and validate the results through in vitro experiments. METHOD: The single-cell RNA sequencing (scRNA-seq) analysis of peripheral blood mononuclear cells (PBMCs) was carried out to investigate the molecular mechanisms of immune responses in vasculitis in KD and COVID-19. The analysis was performed on PBMCs from six children diagnosed with complete KD, three age-matched KD healthy controls (KHC), six COVID-19 patients (COV), three influenza patients (FLU), and four healthy controls (CHC). The results from the scRNA-seq analysis were validated through flow cytometry and immunofluorescence experiments on additional human samples. Subsequently, monocyte adhesion assays, immunofluorescence, and quantitative polymerase chain reaction (qPCR) were used to analyze the damages to endothelial cells post-interaction with monocytes in HUVEC and THP1 cultures. RESULTS: The scRNA-seq analysis revealed the potential cellular types involved and the alterations in genetic transcriptions in the inflammatory responses. The findings indicated that while the immune cell compositions had been altered in KD and COV patients, and the ratio of CD14+ monocytes were both elevated in KD and COV. While the CD14+ monocytes share a large scale of same differentiated expressed geens between KD and COV. The differential activation of CD14 and CD16 monocytes was found to respond to both endothelial and epithelial dysfunctions. Furthermore, SELL+/CCR1+/XAF1+ CD14 monocytes were seen to enhance the adhesion and damage to endothelial cells. The results also showed that different types of B cells were involved in both KD and COV, while only the activation of T cells was recorded in KD. CONCLUSION: In conclusion, our study demonstrated the role of the innate immune response in the regulation of endothelial dysfunction in both KD and COVID-19. Additionally, our findings indicate that the adaptive immunity activation differs between KD and COVID-19. Our results demonstrate that monocytes in COVID-19 exhibit adhesion to both endothelial cells and alveolar epithelial cells, thus providing insight into the mechanisms and shared phenotypes between KD and COVID-19.

Endotoxin tolerance and low activation of TLR-4/NF-κB axis in monocytes of COVID-19 patients.

Higher endotoxin in the circulation may indicate a compromised state of host immune response against coinfections in severe COVID-19 patients. We evaluated the inflammatory response of monocytes from COVID-19 patients after lipopolysaccharide (LPS) challenge. Whole blood samples of healthy controls, patients with mild COVID-19, and patients with severe COVID-19 were incubated with LPS for 2 h. Severe COVID-19 patients presented higher LPS and sCD14 levels in the plasma than healthy controls and mild COVID-19 patients. In non-stimulated in vitro condition, severe COVID-19 patients presented higher inflammatory cytokines and PGE-2 levels and CD14 + HLA-DRlow monocytes frequency than controls. Moreover, severe COVID-19 patients presented higher NF-κB p65 phosphorylation in CD14 + HLA-DRlow, as well as higher expression of TLR-4 and NF-κB p65 phosphorylation in CD14 + HLA-DRhigh compared to controls. The stimulation of LPS in whole blood of severe COVID-19 patients leads to lower cytokine production but higher PGE-2 levels compared to controls. Endotoxin challenge with both concentrations reduced the frequency of CD14 + HLA-DRlow in severe COVID-19 patients, but the increases in TLR-4 expression and NF-κB p65 phosphorylation were more pronounced in both CD14 + monocytes of healthy controls and mild COVID-19 patients compared to severe COVID-19 group. We conclude that acute SARS-CoV-2 infection is associated with diminished endotoxin response in monocytes. KEY MESSAGES: Severe COVID-19 patients had higher levels of LPS and systemic IL-6 and TNF-α. Severe COVID-19 patients presented higher CD14+HLA-DRlow monocytes. Increased TLR-4/NF-κB axis was identified in monocytes of severe COVID-19. Blunted production of cytokines after whole blood LPS stimulation in severe COVID-19. Lower TLR-4/NF-κB activation in monocytes after LPS stimulation in severe COVID-19.

Increased frequency of CD14+HLA-DR-/low cells in type 2 diabetes patients with poor glycemic control.

AIMS: Type 2 diabetes (T2DM) is associated with alterations of the immune response and T2DM patients have an increased risk for infections and certain sorts of cancers. Although CD14+HLA-DR-/low cells have emerged as important mediators of immunosuppression in several pathologies, including cancer and non-malignant diseases, the presence of these cells in T2DM is not fully characterized. METHODS: In this study, we evaluated the frequency of CD14+HLA-DR-/low cells in non-obese T2DM patients and their association with glycemic control. Peripheral blood mononuclear cells were isolated from healthy controls (HC, n = 24) and non-obese T2DM patients (n = 25), the population was evaluated by flow cytometry, and an analysis of correlation between cell frequencies and clinical variables was performed. RESULTS: CD14+HLA-DR-/low monocytes were expanded in patients with T2DM compared to HC regardless of weight. Among the subjects with T2DM, the frequency of CD14+HLA-DR-/low was higher in patients with poor glycemic control (HbA1c > 9%) compared to those with better glycemic control (HbA1c < 9%) and, positively correlated with the years since the diagnosis of T2DM, the age of the patients and the glycemic index. CONCLUSIONS: An increased frequency of CD14+HLA-DR-/low cells in the blood of T2DM patients was recorded. The influence of hyperglycemia seems to be independent of obesity, but related to glycemic control and age.

The significance of a novel inflammatory biomarker, presepsin, in predicting disease prognosis in patients with COVID-19.

OBJECTIVE: This study aims at determining the significance of a novel inflammatory biomarker, presepsin, in predicting disease prognosis in patients with COVID-19. PATIENTS AND METHODS: This retrospective study was concluded at the University Hospital between April and August 2020. The study involved 88 COVID-19 patients (48 men and 40 women). The patients were categorized into two groups: the patients admitted to the COVID-19 clinic, described as the moderate COVID-19 patients (Group-1; n=44), and those admitted to the internal medicine outpatient clinic, who were the mild COVID-19 patients (Group-2; n=44). The groups were compared using inflammatory markers: presepsin, C-Reactive Protein to Albumin Ratio, Neutrophil to Lymphocyte Ratio, and procalcitonin. RESULTS: Serum presepsin levels (195.29 vs. 52.12 pg/ml) were significantly higher in the Group-1 compared to the Group-2 (p=0.001). The gender distribution and average age were similar in both groups (p > 0.05). While ferritin, lactate dehydrogenase, D-Dimer, platelet lymphocyte ratio, C-Reactive Protein to Albumin Ratio (p=0.001), erythrocyte sedimentation ratio, C-Reactive Protein and presepsin were significantly higher in the Group-1 compared to Group-2 (p<0.05), while hemoglobin and lymphocyte were significantly lower in the Group-1 than in Group-2 (p<0.05). CONCLUSIONS: Serum presepsin levels were found to be significantly higher in moderate clinical group COVID-19 patients compared to mild group. Presepsin, a new inflammatory biomarker, may be useful in predicting the prognosis and early treatment of COVID-19 infection.

Presepsin Predicts Severity and Secondary Bacterial Infection in COVID-19 by Bioinformatics Analysis.

Introduction: Novel coronavirus pneumonia (COVID-19) is an acute respiratory disease caused by the novel coronavirus SARS-CoV-2. Severe and critical illness, especially secondary bacterial infection (SBI) cases, accounts for the vast majority of COVID-19-related deaths. However, the relevant biological indicators of COVID-19 and SBI are still unclear, which significantly limits the timely diagnosis and treatment. Methods: The differentially expressed genes (DEGs) between severe COVID-19 patients with SBI and without SBI were screened through the analysis of GSE168017 and GSE168018 datasets. By performing Gene Ontology (GO) enrichment analysis for significant DEGs, significant biological processes, cellular components, and molecular functions were selected. To understand the high-level functions and utilities of the biological system, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was performed. By analyzing protein-protein interaction (PPI) and key subnetworks, the core DEGs were found. Results: 85 DEGs were upregulated, and 436 DEGs were downregulated. The CD14 expression was significantly increased in the SBI group of severe COVID-19 patients (P < 0.01). The area under the curve (AUC) of CD14 in the SBI group in severe COVID-19 patients was 0.9429. The presepsin expression was significantly higher in moderate to severe COVID-19 patients (P < 0.05). Presepsin has a diagnostic value for moderate to severe COVID-19 with the AUC of 0.9732. The presepsin expression of COVID-19 patients in the nonsurvivors was significantly higher than that in the survivors (P < 0.05). Conclusion: Presepsin predicts severity and SBI in COVID-19 and may be associated with prognosis in COVID-19.

Usefulness of monocyte distribution width and presepsin for early assessment of disease severity in COVID-19 patients.

Early predictors of severe coronavirus disease 2019 (COVID-19) would identify patients requiring intensive care. Recently, the monocyte distribution width (MDW) and presepsin level have been used for the early diagnosis of sepsis. Here, we assessed the utility of MDW and presepsin for the early assessment of COVID-19 severity. Eighty-seven inpatients with confirmed COVID-19 were enrolled and divided into 3 groups by the type of respiratory support: (1) mechanical ventilation or high-flow nasal cannula oxygen therapy (MVHF-OT), (2) conventional oxygen therapy, and (3) no oxygen therapy. We measured the complete blood count; MDW; erythrocyte sedimentation rate; and the levels of presepsin, C-reactive protein, procalcitonin, lactate dehydrogenase, ferritin, Krebs von den Lungen-6 (KL-6), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibody. Thirteen (14.9%) patients on MVHF-OT exhibited a significantly higher mortality and a longer hospital stay than did the others. The MDW and presepsin levels were significantly elevated on admission, and correlated with COVID-19 severity (both P < .001). Notably, only the MDW correlated significantly with symptoms in the no oxygen therapy group (P < .012). In the first week after admission, the MDW fell and no longer differed among the groups. The KL-6 level did not differ by disease severity at any time. Neutralizing antibodies were detected in 74 patients (91.4%) and the level of neutralization correlated significantly with COVID-19 severity (P < .001). The MDW and presepsin are useful indicators for early assessment of disease severity in COVID-19 patients.

Prognostic Utility of Procalcitonin, Presepsin, and the VACO Index for Predicting 30-day Mortality in Hospitalized COVID-19 Patients.

BACKGROUND: Biomarkers and clinical indices have been investigated for predicting mortality in patients with coronavirus disease (COVID-19). We explored the prognostic utility of procalcitonin (PCT), presepsin, and the Veterans Health Administration COVID-19 (VACO) index for predicting 30-day-mortality in COVID-19 patients. METHODS: In total, 54 hospitalized COVID-19 patients were enrolled. PCT and presepsin levels were measured using the Elecsys BRAHMS PCT assay (Roche Diagnostics GmbH, Mannheim, Germany) and HISCL Presepsin assay (Sysmex, Kobe, Japan), respectively. The VACO index was calculated based on age, sex, and comorbidities. PCT and presepsin levels and the VACO index were compared using ROC curve, Kaplan-Meier method, and reclassification analysis for the 30-day mortality. RESULTS: ROC curve analysis was used to measure PCT and presepsin levels and the VACO index to predict 30-day mortality; the optimal cut-off values were 0.138 ng/mL for PCT, 717 pg/mL for presepsin, and 12.1% for the VACO index. On Kaplan-Meier survival analysis, hazard ratios (95% confidence interval) were 15.9 (4.1-61.3) for PCT, 26.3 (6.4-108.0) for presepsin, and 6.0 (1.7-21.1) for the VACO index. On reclassification analysis, PCT and presepsin in addition to the VACO index significantly improved the prognostic value of the index. CONCLUSIONS: This study demonstrated the prognostic utility of measuring PCT and presepsin levels and the VACO index in COVID-19 patients. The biomarkers in addition to the clinical index were more useful than the index alone for predicting clinical outcomes in COVID-19 patients.

Presepsin levels in neonatal cord blood are not influenced by maternal SARS-CoV-2 infection.

OBJECTIVES: Coronavirus disease (COVID-19) can present with various symptoms and can involve multiple organs. Women infected during pregnancy have a higher incidence of obstetrical complications and infants born to "positive" mothers may get the infection with different manifestations. Presepsin seems to be a promising sepsis biomarker in adults and neonates. The aim of this study was to assess if presepsin levels in neonatal cord blood could be influenced by maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. METHODS: A total of 119 neonates born from women with a confirmed diagnosis of SARS-CoV-2 infection were enrolled and presepsin levels of cord blood samples were collected. All neonates were tested for SARS-CoV-2 infection at birth and after 48-72 h. RESULTS: The median presepsin value in umbilical cord blood samples collected after birth was 455 pg/mL. Presepsin levels were not influenced by maternal symptoms of COVID-19, weight for gestational age, or delivery mode, and did not significantly differ between infants with and without adverse neonatal outcomes. Infants hospitalized for more than 5 days had a significantly higher presepsin level at birth rather than those discharged up to 4 days of life. Three infants with positive nasopharyngeal swab at birth had higher Presepsin levels than two infants tested positive at 48 h. CONCLUSIONS: This is the first study reporting cord presepsin levels in term and preterm infants born to mothers with COVID-19, that appeared to be not influenced by maternal clinical presentation. However, further studies are needed to explain the mechanisms of P-SEP increase in neonates exposed to perinatal maternal SARS-CoV-2 infection or with an indeterminate/possible SARS-CoV-2 infection in the same neonates.

SCD14-ST and New Generation Inflammatory Biomarkers in the Prediction of COVID-19 Outcome.

Since no definitive cure for COVID-19 is available so far, one of the challenges against the disease is understanding the clinical features and the laboratory inflammatory markers that can differentiate among different severity grades of the disease. The aim of the present study is a comprehensive and longitudinal evaluation of SCD14-ST and other new inflammatory markers, as well as cytokine storm molecules and current inflammatory parameters, in order to define a panel of biomarkers that could be useful for a better prognostic prediction of COVID-19 mortality. SCD14-ST, as well as the inflammatory markers IL-6, IL-10, SuPAR and sRAGE, were measured in plasma-EDTA of ICU COVID-19 positive patients. In this longitudinal study, SCD14-ST resulted significantly higher in patients who eventually died compared to those who were discharged from the ICU. The results suggest that the new infection biomarker SCD14-ST, in addition to new generation inflammatory biomarkers, such as SuPAR, sRAGE and the cytokines IL-6 and IL-10, can be a useful prognostic tool associated with canonical inflammatory parameters, such as CRP, to predict SARS-CoV-2 outcome in ICU patients.

Serum stratifin and presepsin as candidate biomarkers for early detection of COVID-19 disease progression.

The prognosis of patients with severe cases of COVID-19 is poor; thus, biomarkers for earlier prediction of COVID-19 progression are vital. We measured levels of five lung injury-related biomarkers, SP-D, KL-6, presepsin, kallistatin and stratifin, in serum samples collected serially during hospitalization from 31 patients with mild/moderate or severe/critical COVID-19 pneumonia, and their predictive performances were compared. Like the previously reported presepsin, a new biomarker candidate, stratifin, was significantly elevated with the onset of severe or critical symptoms in COVID-19 patients and decreased with symptom improvement. Notably, changes in stratifin and presepsin levels were distinctly earlier than those in SP-D, KL-6 and even SpO2/FiO2 values. Furthermore, serum levels of these biomarkers were significantly higher at the pre-severe stage (before the start of oxygen support) of patients who eventually advanced to severe/critical stages than in the patients who remained at the mild/moderate stage. These results were confirmed in an independent cohort, including 71 mild/moderate and 14 severe/critical patients, for whom the performance of stratifin and presepsin in discriminating between mild/moderate and pre-severe conditions of COVID-19 patients was superior to that of the SpO2/FiO2 ratio. Therefore, we concluded that stratifin and presepsin could be used as prognostic biomarkers for severe COVID-19 progression.

Predictive Values of Procalcitonin and Presepsin for Acute Kidney Injury and 30-Day Hospital Mortality in Patients with COVID-19.

Background and Objectives: Acute kidney injury (AKI) is a common complication in patients with coronavirus disease 2019 (COVID-19). We investigated the values of procalcitonin (PCT) and presepsin (PSS) for predicting AKI and 30-day hospital mortality in patients with COVID-19. Materials and Methods: We retrospectively evaluated 151 patients with COVID-19 who were admitted to the hospital via the emergency department. The diagnosis of AKI was based on the Kidney Disease: Improving Global Outcomes clinical practice guidelines. Results: The median patient age was 77 years, and 86 patients (57%) were male. Fifty-six patients (37.1%) developed AKI, and 19 patients (12.6%) died within 30 days of hospital admission. PCT and PSS levels were significantly higher in patients with AKI and non-survivors. The cutoff values of PCT levels for predicting AKI and mortality were 2.26 ng/mL (sensitivity, 64.3%; specificity, 89.5%) and 2.67 ng/mL (sensitivity, 68.4%; specificity, 77.3%), respectively. The cutoff values of PSS levels for predicting AKI and mortality were 572 pg/mL (sensitivity, 66.0%; specificity, 69.1%) and 865 pg/mL (sensitivity, 84.6%; specificity, 76.0%), respectively. Conclusion: PCT and PSS are valuable biomarkers for predicting AKI and 30-day hospital mortality in patients with COVID-19.

Viral load is associated with mitochondrial dysfunction and altered monocyte phenotype in acute severe SARS-CoV-2 infection.

Monocytes play a major role in the initial innate immune response to SARS-CoV-2. Although viral load may correlate with several clinical outcomes in COVID-19, much less is known regarding their impact on innate immune phenotype. We evaluated the monocyte phenotype and mitochondrial function in severe COVID-19 patients (n = 22) with different viral burden (determined by the median of viral load of the patients) at hospital admission. Severe COVID-19 patients presented lower frequency of CD14 + CD16- classical monocytes and CD39 expression on CD14 + monocytes, and higher frequency of CD14 + CD16 + intermediate and CD14-CD16 + nonclassical monocytes as compared to healthy controls independently of viral load. COVID-19 patients with high viral load exhibited increased GM-CSF, PGE-2 and lower IFN-α as compared to severe COVID-19 patients with low viral load (p < 0.05). CD14 + monocytes of COVID-19 patients with high viral load presented higher expression of PD-1 but lower HLA-DR on the cell surface than severe COVID-19 patients with low viral load. All COVID-19 patients presented decreased monocyte mitochondria membrane polarization, but high SARS-CoV-2 viral load was associated with increased mitochondrial reactive oxygen species. In this sense, higher viral load induces mitochondrial reactive oxygen species generation associated with exhaustion profile in CD14 + monocytes of severe COVID-19 patients. Altogether, these data shed light on new pathological mechanisms involving SARS-CoV-2 viral load on monocyte activation and mitochondrial function, which were associated with COVID-19 severity.

Persistent Oxidative Stress and Inflammasome Activation in CD14highCD16- Monocytes From COVID-19 Patients.

The poor outcome of the coronavirus disease-2019 (COVID-19), caused by SARS-CoV-2, is associated with systemic hyperinflammatory response and immunopathology. Although inflammasome and oxidative stress have independently been implicated in COVID-19, it is poorly understood whether these two pathways cooperatively contribute to disease severity. Herein, we found an enrichment of CD14highCD16- monocytes displaying inflammasome activation evidenced by caspase-1/ASC-speck formation in severe COVID-19 patients when compared to mild ones and healthy controls, respectively. Those cells also showed aberrant levels of mitochondrial superoxide and lipid peroxidation, both hallmarks of the oxidative stress response, which strongly correlated with caspase-1 activity. In addition, we found that NLRP3 inflammasome-derived IL-1ß secretion by SARS-CoV-2-exposed monocytes in vitro was partially dependent on lipid peroxidation. Importantly, altered inflammasome and stress responses persisted after short-term patient recovery. Collectively, our findings suggest oxidative stress/NLRP3 signaling pathway as a potential target for host-directed therapy to mitigate early COVID-19 hyperinflammation and also its long-term outcomes.

Could presepsin be an alternative marker in the early diagnosis of sepsis in COVID-19?

In critical patients with Coronavirus Disease (COVID-19), we investigated the diagnostic value of presepsin in the early diagnosis of superinfection with sepsis, and the effect of antibiotic treatment (AT) in the levels of presepsin and procalcitonin and C-reactive protein. A total of 68 critical patients with sepsis and septic shock in the intensive care unit and 20 outpatients (control group) with COVID-19 were taken. ICU patients (n = 68) were further divided into three groups. C(-)AT(-) had negative blood or tracheal aspirate cultures (C) and not AT on admission to ICU (n = 18), C(-)AT(+) had negative C and AT on admission to intensive care unit (n = 31) and C(+) had positive C (n = 19). Presepsin, procalcitonin, C-reactive protein results were compared between the groups. There were no significant relationships between presepsin levels with sepsis, septic shock, mortality, or length of stay in ICU in patients with COVID-19. For procalcitonin and C-reactive protein levels in C(-)AT(+) and C(+) groups were significantly higher than in control and C(-)AT(-) groups (p < .001). C-reactive protein levels in C(-)AT(-) group were significantly higher than in the control group (p < .001). PCT and CRP, there was no difference between C(-)AT(+) and C(+) groups, and procalcitonin there was no difference between control and C(-)AT(-) groups. Presepsin was not found as a useful biomarker for the prediction of sepsis in COVID-19 patients. These study findings indicate that procalcitonin and C-reactive protein may be an indicator of an early diagnostic marker for superinfection in critical COVID-19 patients.

Crystal Structures of Bat and Human Coronavirus ORF8 Protein Ig-Like Domain Provide Insights Into the Diversity of Immune Responses.

ORF8 is a viral immunoglobulin-like (Ig-like) domain protein encoded by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA genome. It tends to evolve rapidly and interfere with immune responses. However, the structural characteristics of various coronavirus ORF8 proteins and their subsequent effects on biological functions remain unclear. Herein, we determined the crystal structures of SARS-CoV-2 ORF8 (S84) (one of the epidemic isoforms) and the bat coronavirus RaTG13 ORF8 variant at 1.62 Å and 1.76 Å resolution, respectively. Comparison of these ORF8 proteins demonstrates that the 62-77 residues in Ig-like domain of coronavirus ORF8 adopt different conformations. Combined with mutagenesis assays, the residue Cys20 of ORF8 is responsible for forming the covalent disulfide-linked dimer in crystal packing and in vitro biochemical conditions. Furthermore, immune cell-binding assays indicate that various ORF8 (SARS-CoV-2 ORF8 (L84), ORF8 (S84), and RaTG13 ORF8) proteins have different interaction capabilities with human CD14+ monocytes in human peripheral blood. These results provide new insights into the specific characteristics of various coronavirus ORF8 and suggest that ORF8 variants may influence disease-related immune responses.