Increased concentrations of the soluble mannose receptor in serum from patients with pneumococcal bacteraemia, and prediction of survival

sMR and PTX3 levels associate with COVID-19 outcome and survival but not with Long COVID

Biomarkers for monitoring COVID-19 disease course are lacking. Study aim was to identify biomarkers associated with disease severity, survival, long-term outcome, and Long COVID. As excessive macrophages activation is a hallmark of COVID-19 and complement activation is key in this, we selected the following proteins involved in these processes: PTX3, C1q, C1-INH, C1s/C1-INH, and sMR. EDTA-plasma concentrations were measured in 215 patients and 47 controls using ELISA. PTX3, sMR, C1-INH, and C1s/C1-INH levels were associated with disease severity. PTX3 and sMR were also associated with survival and long-term immune recovery. Lastly, sMR levels associate with ICU admittance. sMR (AUC 0.85) and PTX3 (AUC 0.78) are good markers for disease severity, especially when used in combination (AUC 0.88). No association between biomarker levels and Long COVID was observed. sMR has not previously been associated with COVID-19 disease severity, ICU admittance or survival and may serve as marker for disease course.

CD163 and CD206 expression define distinct macrophage subsets involved in active ANCA-associated glomerulonephritis

INTRODUCTION

Macrophages are key players in the immunopathology of anti-neutrophil cytoplasmic antibody (ANCA) mediated-vasculitis (AAV) with glomerulonephritis (ANCA GN). Different macrophage phenotypes are expected to play distinct roles in ANCA GN. Macrophages expressing CD163 and CD206 are found in lesions associated with ANCA GN. Hence, we aimed to investigate the clinicopathological significance of CD206 and CD163 in ANCA GN in a multicenter retrospective cohort study.

MATERIAL AND METHODS

Patients with ANCA-associated vasculitis, with clinical data, serum and urine samples were included from three cohorts. Serum soluble CD206 (ssCD206) and urinary soluble CD163 (usCD163) levels were measured. Human kidney tissue samples (n = 53) were stained for CD206 and CD163 using immunohistochemistry and immunofluorescence, and findings were correlated with clinical and pathological data.

RESULTS

In total, 210 patients were included (i.e., ANCA GN, n = 134; AAV without GN, n = 24; AAV in remission n = 52). Increased levels of both ssCD206 and usCD163 were seen in ANCA GN. High levels of ssCD206 declined after reaching remission, however, ssCD206 did not improve the accuracy of usCD163 to detect ANCA GN. Soluble markers correlated with histopathological findings. CD163⁺CD206^- macrophages were found in the glomerulus and may play pivotal roles in glomerulonephritis, whereas CD206⁺CD163^- and CD206⁺CD163⁺ macrophages were located tubulointerstitially and likely play a more prominent role in ANCA-associated tubulointerstitial inflammation. In ANCA GN patients increasing levels of ssCD206 increased the risk for end-stage renal disease and mortality.

CONCLUSIONS

Our results confirm and extend the notion that CD206⁺ and CD163⁺ macrophages are prominent components of the cellular infiltrate in ANCA GN. We found distinct macrophage phenotypes that may play distinct roles in the immunopathology of ANCA GN and elaborate on a potential mechanism underlying the findings of this study. usCD163 remains an excellent marker to detect active ANCA GN, whereas ssCD206 seems a more prominent marker for risk prediction.

CD206+CD68+ mono-macrophages and serum soluble CD206 level are increased in antineutrophil cytoplasmic antibodies associated glomerulonephritis

Background

Antineutrophil Cytoplasmic Antibodies (ANCA) associated glomerulonephritis (AGN) is a group of autoimmune diseases and mono-macrophages are involved in its glomerular injuries. In this study, we aim to investigate the role of CD206⁺ mono-macrophages in AGN.

Methods

27 AGN patients (14 active AGN, 13 remissive AGN) together with healthy controls (n = 9), disease controls (n = 6) and kidney function adjusted controls (n = 9) from Department of Nephrology, Ruijin hospital were recruited. Flow cytometry was used to study proportion of CD206⁺ cells in peripheral blood. Immunohistochemistry for CD206 staining was performed and CD206 expression was scored in different kidney regions. Serum soluble CD206 (sCD206) was measured by enzyme-linked immunosorbent assay (ELISA). We also generated murine myeloperoxidase (MPO) (muMPO) ANCA by immunizing Mpo^−/− mice. Mouse bone marrow-derived macrophages (BMDMs) from wild C57BL/6 mice and peripheral blood mononuclear cell (PBMC) derived macrophages from healthy donors were treated with MPO ANCA with or without its inhibitor AZD5904 to investigate the effects of MPO-ANCA on CD206 expression.

Results

The proportion of peripheral CD206⁺CD68⁺ cells in active AGN patients were significantly higher than that in remissive patients (p < 0.001), healthy controls (p < 0.001) and kidney function adjusted controls (p < 0.001). Serum sCD206 level in active AGN patients was higher than that in healthy controls (p < 0.05) and remissive patients (p < 0.01). Immunohistochemistry showed CD206 was highly expressed in different kidney regions including fibrinoid necrosis or crescent formation, glomeruli, periglomerular and tubulointerstitial compartment in active AGN patients in comparison with disease controls. Further studies showed MPO ANCA could induce CD206 expression in BMDMs and PBMC derived macrophages and such effects could be reversed by its inhibitor AZD5904.

Conclusion

ANCA could induce CD206 expression on mono-macrophages and CD206⁺ mono-macrophages are activated in AGN. CD206 might be involved in the pathogenesis of AAV and may be a potential target for the disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-022-00529-w.

Lipid scavenging macrophages and inflammation

Macrophages are professional phagocytes, indispensable for maintenance of tissue homeostasis and integrity. Depending on their resident tissue, macrophages are exposed to highly diverse metabolic environments. Adapted to their niche, they can contribute to local metabolic turnover through metabolite uptake, conversion, storage and release. Disturbances in tissue homeostasis caused by infection, inflammation or damage dramatically alter the local milieu, impacting macrophage activation status and metabolism. In the case of persisting stimuli, defective macrophage responses ensue, which can promote tissue damage and disease. Especially relevant herein are disbalances in lipid rich environments, where macrophages are crucially involved in lipid uptake and turnover, preventing lipotoxicity. Lipid uptake is to a large extent facilitated by macrophage expressed scavenger receptors that are dynamically regulated and important in many metabolic diseases. Here, we review the receptors mediating lipid uptake and summarize recent findings on their role in health and disease. We further highlight the underlying pathways driving macrophage lipid acquisition and their impact on myeloid metabolic remodelling.

Soluble mannose receptor induces proinflammatory macrophage activation and metaflammation

Proinflammatory activation of macrophages in metabolic tissues is critically important in the induction of obesity-induced metaflammation. Here, we demonstrate that the soluble mannose receptor (sMR) plays a direct functional role in both macrophage activation and metaflammation. We show that sMR binds CD45 on macrophages and inhibits its phosphatase activity, leading to an Src/Akt/NF-κB-mediated cellular reprogramming toward an inflammatory phenotype both in vitro and in vivo. Remarkably, increased serum sMR levels were observed in obese mice and humans and directly correlated with body weight. Importantly, enhanced sMR levels increase serum proinflammatory cytokines, activate tissue macrophages, and promote insulin resistance. Altogether, our results reveal sMR as regulator of proinflammatory macrophage activation, which could constitute a therapeutic target for metaflammation and other hyperinflammatory diseases.

Soluble collectin-12 mediates C3-independent docking of properdin that activates the alternative pathway of complement

Properdin stabilizes the alternative C3 convertase (C3bBb), whereas its role as pattern-recognition molecule mediating complement activation is disputed for decades. Previously, we have found that soluble collectin-12 (sCL-12) synergizes complement alternative pathway (AP) activation. However, whether this observation is C3 dependent is unknown. By application of the C3-inhibitor Cp40, we found that properdin in normal human serum bound to Aspergillus fumigatus solely in a C3b-dependent manner. Cp40 also prevented properdin binding when properdin-depleted serum reconstituted with purified properdin was applied, in analogy with the findings achieved by C3-depleted serum. However, when opsonized with sCL-12, properdin bound in a C3-independent manner exclusively via its tetrameric structure and directed in situ C3bBb assembly. In conclusion, a prerequisite for properdin binding and in situ C3bBb assembly was the initial docking of sCL-12. This implies a new important function of properdin in host defense bridging pattern recognition and specific AP activation.

Liver-related effects of chronic hepatitis C antiviral treatment

More than five years ago, the treatment of hepatitis C virus infection was revolutionized with the introduction of all-oral direct-acting antiviral (DAA) drugs. They proved highly efficient in curing patients with chronic hepatitis C (CHC), including patients with cirrhosis. The new DAA treatments were alleged to induce significant improvements in clinical outcome and prognosis, but the exact cause of the expected benefit was unclear. Further, little was known about how the underlying liver disease would be affected during and after viral clearance. In this review, we describe and discuss the liver-related effects of the new treatments in regards to both pathophysiological aspects, such as macrophage activation, and the time-dependent effects of therapy, with specific emphasis on inflammation, structural liver changes, and liver function, as these factors are all related to morbidity and mortality in CHC patients. It seems clear that antiviral therapy, especially the achievement of a sustained virologic response has several beneficial effects on liver-related parameters in CHC patients with advanced liver fibrosis or cirrhosis. There seems to be a time-dependent effect of DAA therapy with viral clearance and the resolution of liver inflammation followed by more discrete changes in structural liver lesions. These improvements lead to favorable effects on liver function, followed by an improvement in cognitive dysfunction and portal hypertension. Overall, the data provide knowledge on the several beneficial effects of DAA therapy on liver-related parameters in CHC patients suggesting short- and long-term improvements in the underlying disease with the promise of an improved long-term prognosis.

Macrophage Activation Markers, CD163 and CD206, in Acute-on-Chronic Liver Failure

Macrophages facilitate essential homeostatic functions e.g., endocytosis, phagocytosis, and signaling during inflammation, and express a variety of scavenger receptors including CD163 and CD206, which are upregulated in response to inflammation. In healthy individuals, soluble forms of CD163 and CD206 are constitutively shed from macrophages, however, during inflammation pathogen- and damage-associated stimuli induce this shedding. Activation of resident liver macrophages viz. Kupffer cells is part of the inflammatory cascade occurring in acute and chronic liver diseases. We here review the existing literature on sCD163 and sCD206 function and shedding, and potential as biomarkers in acute and chronic liver diseases with a particular focus on Acute-on-Chronic Liver Failure (ACLF). In multiple studies sCD163 and sCD206 are elevated in relation to liver disease severity and established as reliable predictors of morbidity and mortality. However, differences in expression- and shedding-stimuli for CD163 and CD206 may explain dissimilarities in prognostic utility in patients with acute decompensation of cirrhosis and ACLF.

Macrophage Mannose Receptor CD206 Predicts Prognosis in Community-acquired Pneumonia

CD206, a mannose receptor, is mainly expressed on the surface of alternatively activated macrophages where it acts as a pattern recognition receptor and plays a role in innate and adaptive immunity. This study investigated serum soluble CD206 (sCD206) levels in community-acquired pneumonia (CAP) and examined their clinical significance. sCD206 concentrations were measured in the sera of two independent cohorts with CAP (127 and 125 patients, respectively) and 42 controls. The expression of CD206 in the lung from autopsied cases was also examined. Patients with CAP showed significantly elevated sCD206 levels than did the controls (p < 0.0001). Notably, fatal CAP patients had more than two-fold higher sCD206 concentrations than survivors in both cohorts (p < 0.0001). Serum sCD206 concentrations were associated with Pneumonia Severity Index (PSI) and CURB-65 values. Importantly, even fatal CAP patients classified as PSI I-IV, CURB65 0–2 or age <75 years had comparatively higher levels of sCD206 than those classified as PSI V, CURB-65 3–5 or age ≥75 years. Immunohistochemically, the infiltration of CD206⁺ macrophages was found in the lungs of fatal cases. Elevated levels of sCD206 are associated with CAP prognosis, suggesting sCD206 might be a potential biomarker to predict severity for CAP.

The soluble mannose receptor (sMR/sCD206) in critically ill patients with invasive fungal infections, bacterial infections or non-infectious inflammation: a secondary analysis of the EPaNIC RCT

Background

Invasive fungal infections (IFI) are difficult to diagnose, especially in critically ill patients. As the mannose receptor (MR) is shed from macrophage cell surfaces after exposure to fungi, we investigate whether its soluble serum form (sMR) can serve as a biomarker of IFI.

Methods

This is a secondary analysis of the multicentre randomised controlled trial (EPaNIC, n = 4640) that investigated the impact of initiating supplemental parenteral nutrition (PN) early during critical illness (Early-PN) as compared to withholding it in the first week of intensive care (Late-PN). Serum sMR concentrations were measured in three matched patient groups (proven/probable IFI, n = 82; bacterial infection, n = 80; non-infectious inflammation, n = 77) on the day of antimicrobial initiation or matched intensive care unit day and the five preceding days, as well as in matched healthy controls (n = 59). Independent determinants of sMR concentration were identified via multivariable linear regression. Serum sMR time profiles were analysed with repeated-measures ANOVA. Predictive properties were assessed via area under the receiver operating curve (aROC).

Results

Serum sMR was higher in IFI patients than in all other groups (all p < 0.02), aROC to differentiate IFI from no IFI being 0.65 (p < 0.001). The ability of serum sMR to discriminate infectious from non-infectious inflammation was better with an aROC of 0.68 (p < 0.001). The sMR concentrations were already elevated up to 5 days before antimicrobial initiation and remained stable over time. Multivariable linear regression analysis showed that an infection or an IFI, higher severity of illness and sepsis upon admission were associated with higher sMR levels; urgent admission and Late-PN were independently associated with lower sMR concentrations.

Conclusion

Serum sMR concentrations were higher in critically ill patients with IFI than in those with a bacterial infection or with non-infectious inflammation. However, test properties were insufficient for diagnostic purposes.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2549-8) contains supplementary material, which is available to authorized users.

Soluble mannose receptor levels in blood correlate to disease severity in patients with community-acquired pneumonia

PURPOSE

Community-acquired pneumonia (CAP) is the most common form of pneumonia and is a leading infectious cause worldwide. Identification of patients that are at risk to develop severe disease has proven to be a major challenge. Soluble mannose receptor (sMR; sCD206) is a new serum marker for macrophage activation. Recent studies showed that sMR levels are increased in patients suffering from severe infections making it a potential biomarker for improved discrimination of disease severity. For measuring sMR, no standardized assay is available. Aim of this study is to develop an assay for standardized measurement of sMR. Next, this assay was used to assess sMR plasma levels for its ability to predict severe disease development in a patient cohort for community-acquired pneumonia.

METHODS

We developed a well-validated sandwich ELISA that enables standardized measurement of sMR in plasma and serum samples. Repeatability was tested by calculating the percentage coefficient of variation (%CV) within and between runs and within and between operators. sMR levels were assessed in a cohort of 100 patients with community-acquired pneumonia.

RESULTS

All %CV values were <10%, indicating low variation. Higher sMR levels were observed in patients with severe disease when compared to patients without severe disease development (p = 0.004). Patients with sMR levels between 100-430 ng/ml had 22.7% chance to develop severe disease whereas patients with levels between 430-1000 ng/ml had 33.3% chance to develop severe disease.

CONCLUSIONS

We suggest that sMR has potential as a new biomarker for the prediction of disease severity in patients with community-acquired pneumonia.

The macrophage activation marker sMR as a diagnostic and prognostic marker in patients with acute infectious disease with or without sepsis

Sepsis is a leading cause of mortality. This study aims to assess the utility of the soluble mannose receptor (sMR) as a biomarker of sepsis and mortality in patients hospitalized with suspected infection. Using an in-house ELISA assay the concentration of sMR was analyzed in the serum of patients from three prospective studies. Using Sepsis-3 guidelines, patients were stratified as no infection (NI, n = 68), verified infection without sepsis (NSEP, n = 133) and verified infection with sepsis (SEP, n = 190). Adverse outcome was assessed as death before 28 days. We show that the sensitivity of sMR to predict mortality [area under curve (AUC) = 0.77] exceeded the sensitivity of procalcitonin (PCT, AUC = 0.63), C-reactive protein (CRP, AUC = 0.61) and the macrophage soluble receptor, CD163 (sCD163, AUC = 0.74), while it was less accurate to predict diagnosis of sepsis [AUC(sMR) = 0.69 vs. AUC(PCT) = 0.79, AUC(CRP) = 0.71 and AUC(sCD163) = 0.66]. Median sMR was significantly higher in the group with SEP (0.55 mg/L), compared with the groups without sepsis (NI and NSEP) (0.39 mg/L, p < .0001), and among those who died compared to those who survived (0.89 mg/L vs. 0.44 mg/L, p < .0001). Our results, and the current literature, support further evaluation of sMR as a biomarker of sepsis and mortality among patients hospitalized with suspected infection.

The soluble mannose receptor (sMR) is elevated in alcoholic liver disease and associated with disease severity, portal hypertension, and mortality in cirrhosis patients

Background and aims

Hepatic macrophages (Kupffer cells) are involved in the immunopathology of alcoholic liver disease (ALD). The mannose receptor (MR, CD206), expressed primarily by macrophages, mediates endocytosis, antigen presentation and T-cell activation. A soluble form, sMR, has recently been identified in humans.

We aimed to study plasma sMR levels and its correlation with disease severity and survival in ALD patients.

Methods

We included 50 patients with alcoholic hepatitis (AH), 68 alcoholic cirrhosis (AC) patients (Child-Pugh A (23), B (24), C (21)), and 21 healthy controls (HC). Liver status was described by the Glasgow Alcoholic Hepatitis Score (GAHS), Child-Pugh (CP) and MELD-scores, and in AC patients the hepatic venous pressure gradient (HVPG) was measured by liver vein catheterisation. We used Kaplan-Meier statistics for short-term survival (84-days) in AH patients and long-term (4 years) in AC patients. We measured plasma sMR by ELISA.

Results

Median sMR concentrations were significantly elevated in AH 1.32(IQR:0.69) and AC 0.46(0.5) compared to HC 0.2(0.06) mg/L; p<0.001 and increased in a stepwise manner with the CP-score (p<0.001). In AC sMR predicted portal hypertension (HVPG ≥10 mmHg) with an area under the Receiver Operator Characteristics curve of 0.86 and a high sMR cut-off (>0.43 mg/l) was associated with increased mortality (p = 0.005).

Conclusion

The soluble mannose receptor is elevated in alcoholic liver disease, especially in patients with AH. Its blood level predicts portal hypertension and long-term mortality in AC patients.

Preoperative serum macrophage activated biomarkers soluble mannose receptor (sMR) and soluble haemoglobin scavenger receptor (sCD163), as novel markers for the diagnosis and prognosis of gastric cancer

Soluble mannose receptor (sMR) and soluble haemoglobin scavenger receptor (sCD163) are macrophage activation markers which have previously been demonstrated to be increased in patients with inflammation, auto-immunity and malignancies. To investigate the clinical diagnostic and prognostic significance of preoperative serum sMR and sCD163, the present study investigated 143 gastric cancer (GC) patients, 66 subjects with benign gastric disease and 59 healthy controls, using an ELISA assay. Preoperative serum levels of sMR and sCD163 ranged from 0.165 to 0.885 µg/ml (median=0.374 µg/ml) and from 0.291 to 1.760 µg/ml (median=0.628 µg/ml) in GC patients, respectively. The expression levels of sMR and sCD163 were elevated compared with all controls (P<0.0001). Receiver operating characteristic analyses suggested that the optimum diagnostic cut-offs for sMR and sCD163 were 0.3405 µg/ml [area under curve (AUC) 0.7284, sensitivity 61.54%, and specificity 73.60%] and 0.6645 µg/ml (AUC 0.7766, sensitivity 53.85%, and specificity 86.40%), respectively. Notably, the measurement of serum sMR and sCD163 levels in conjugation, markedly enhanced the diagnostic accuracy (AUC 0.8490, sensitivity 70.63% and specificity 84.00%). Preoperative serum sMR and sCD163 levels correlated significantly with serum carcinoembryonic antigen, CA199, CA724 and CA125 concentrations in GC patients (P<0.05), however this association was not observed with sMR and CA724. High preoperative serum sMR and sCD163 levels correlated significantly with shorter overall survival (P=0.0041; P<0.0001, respectively) and were demonstrated to act as adverse prognostic factors (P=0.006; P<0.001, respectively). Furthermore, preoperative serum sMR and sCD163 levels correlated positively with the degree of lymphatic and distant metastasis of GC. In conclusion, preoperative serum sMR and sCD163 may be novel diagnostic and prognostic markers for GC and further studies are required in order to elucidate the underlying molecular mechanisms of sMR and CD163 in the development and progression of GC.

Macrophage activation marker, soluble CD163, is an independent predictor of short-term mortality in patients with cirrhosis and bacterial infection

BACKGROUND & AIMS

Innate immune system dysfunction is common in advanced cirrhosis, with a central role of the monocyte/macrophage system. Monocytes and macrophages express the scavenger receptor CD163, which is regulated by inflammatory mediators. Cleavage of the receptor leads to the formation of soluble (s)CD163 that represents an anti-inflammatory response. We aimed to study the clinical importance of sCD163 in cirrhosis.

METHODS

Sera of 378 patients were assayed for sCD163 by ELISA [193 outpatients and 185 patients with acute decompensation (AD)]. A 5-year follow-up observational study was conducted to assess the possible association between sCD163 level and poor disease outcomes.

RESULTS

sCD163 level was associated with disease severity, but not with the presence of varices or prior variceal bleeding. In outpatients, sCD163 level did not predict the development of disease-specific complications or the long-term mortality. In patients with AD episode, sCD163 level was significantly higher compared to outpatients but only in the presence of bacterial infection (INF) (AD-INF:4586, AD-NON-INF:3792 and outpatients: 3538 ng/ml, P < 0.015 and P = 0.001, respectively). sCD163 level gradually increased according to severity of infection. During bacterial infections, high sCD163 level (>7000 ng/ml) was associated with increased mortality rate (42% vs. 17%, P < 0.001) and was identified as an independent predictor of 28-day mortality (hazard ratio:2.96, 95% confidence intervals:1.27-6.95) in multivariate Cox-regression model comprising aetiology, co-morbidity, model for end-stage liver disease score and leucocyte count as covariates.

CONCLUSIONS

High sCD163 level is useful to identify patients with high-risk of death during an AD episode complicated by bacterial infection. This finding serves as an additional hint towards the significance of anti-inflammatory response during bacterial infection.

Macrophage activation markers predict mortality in patients with liver cirrhosis without or with acute-on-chronic liver failure (ACLF)

BACKGROUND & AIMS

Activation of liver macrophages plays a key role in liver and systemic inflammation and may be involved in development and prognosis of acute-on-chronic liver failure (ACLF). We therefore measured the circulating macrophage activation markers soluble sCD163 and mannose receptor (sMR) and related them to the short-(1-3 months) and long-term (6 months) mortality in the cirrhosis patients of the CANONIC study.

METHODS

Eighty-six cirrhosis patients had no ascites and no ACLF, 580 had ascites but no ACLF; 100, 66, and 19 had ACLF-grade-I (ACLF-I), ACLF-II, and ACLF-III, respectively. The patients' clinical course was registered and their MELD, CLIF-C Acute Decompensation (AD), and CLIF-C ACLF-scores computed at inclusion.

RESULTS

We found a stepwise increase (p<0.001) in median sCD163 (5.68 (IQR: 3.86-9.60); 8.26 (5.02-12.34); 9.50 (5.37-17.91); 15.68 (10.12-19.42); 20.18 (15.26-32.20) mg/L) and sMR (0.60 (0.40-0.84); 0.81 (0.57-1.12); 0.81 (0.61-1.26); 1.17 (0.89-1.62); 1.41 (1.14-1.79)mg/L) with increasing grades of ACLF. Both sCD163 and sMR were independently associated with short and long-term mortality and showed equal or higher predictive accuracy than MELD, CLIF-C ACLF and CLIF-C AD scores. Addition of the macrophage markers to the clinical scores improved the prognostic efficacy: In ACLF patients sCD163 improved prediction of short-term mortality (C-index: 0.74 (0.67-0.80)) and in patients without ACLF sMR improved prediction of long-term mortality (C-index: 0.80 (0.76-0.85)).

CONCLUSIONS

The severity related increase in sCD163 and sMR and close association with mortality suggest a primary importance of inflammatory activation of liver macrophages in the emergence and course of ACLF. Accordingly, supplementation of the macrophage biomarkers to the platform of the clinical scores improved the prognostic performance beyond that of the original scores.