Myeloid-related proteins 8 and 14 are specifically secreted during interaction of phagocytes and activated endothelium and are useful markers for monitoring disease activity in pauciarticular-onset juvenile rheumatoid arthritis

Serum Levels of S100A8/A9 as a Biomarker of Disease Activity in Patients with IgA Vasculitis

S100A8/A9 protein is a well-known marker of disease activity or severity in many autoimmune and autoinflammatory diseases, but there have not been many studies about the role of S100A8/A9 in IgA vasculitis (IgAV). The aim of our study was to evaluate S100A8/A9 as a possible biomarker of activity in IgAV. We measured the serum levels of S100A8/A9 in pediatric patients with IgA vasculitis at the onset of the disease, after three months, and after six months. We compared these levels between patients with active disease, remission, and a control group, and assessed their correlation with disease activity and other markers of inflammation. Patients with active disease had significantly higher levels of serum S100A8/A9 (median ± SD) than those in the control group at the beginning of the disease (5740 ± 3157 ng/mL vs. 1447 ± 858.3 ng/mL; p < 0.0001), but also three months and six months after disease onset (p < 0.001). There was a positive correlation between S100A8/A9 serum levels and disease activity (p = 0.0003). Patients with active disease had significantly higher levels of S100A8/A9 than those in remission three months after disease onset (p = 0.0260). There was a correlation between S100A8/A9 and C-reactive protein, the C3 component of complement, ferritin, and fibrinogen. Serum levels of S100A8/A9 were also higher in patients with greater skin areas covered with rash. We demonstrated that serum levels of S100A8/A9 correlated well with disease activity and other biomarkers of inflammation in children with IgAV. According to our results, serum S100A8/A9 may be a good indicator of active disease in IgAV.

S100A4 a classical DAMP as a therapeutic target in fibrosis

Fibrosis regardless of aetiology is characterised by persistently activated myofibroblasts that are contractile and secrete excessive amounts of extracellular matrix molecules that leads to loss of organ function. Damage-Associated Molecular Patterns (DAMPs) are endogenous host-derived molecules that are released from cells dying or under stress that can be triggered by a variety of insults, either chemical or physical, leading to an inflammatory response. Among these DAMPs is S100A4, part of the S100 family of calcium binding proteins that participate in a variety of cellular processes. S100A4 was first described in context of cancer as a pro-metastatic factor. It is now appreciated that aside from its role in cancer promotion, S100A4 is intimately involved in tissue fibrosis. The extracellular form of S100A4 exerts its effects through multiple receptors including Toll-Like Receptor 4 and RAGE to evoke signalling cascades involving downstream mediators facilitating extracellular matrix deposition and myofibroblast generation and can play a role in persistent activation of myofibroblasts. S100A4 may be best understood as an amplifier of inflammatory and fibrotic processes. S100A4 appears critical in systemic sclerosis pathogenesis and blocking the extracellular form of S100A4 in vivo in various animal models of disease mitigates fibrosis and may even reverse established disease. This review appraises S100A4's position as a DAMP and its role in fibrotic conditions and highlight therapeutically targeting this protein to halt fibrosis, suggesting that it is a tractable target.

Serum Calprotectin Levels in Different Subtypes of Juvenile Idiopathic Arthritis (JIA) and Its Correlation with Quantitative CRP and JADAS-27

OBJECTIVE

To study the serum calprotectin levels in children with juvenile idiopathic arthritis (JIA) and correlate it with C-reactive protein (CRP) and the Juvenile Arthritis Disease Activity Score-27 (JADAS-27).

METHODS

This was a cross-sectional observational study done between November 2017 and March 2019. Fifty treatment-naive children, aged 1 to 18 y with the diagnosis of JIA as per the International League of Associations of Rheumatology (ILAR) criteria were enrolled. Assessment of disease activity was done according to the Juvenile Arthritis Disease Activity Score (JADAS-27). Determination of serum calprotectin and CRP levels was done by immunoassay. The correlation between calprotectin levels with CRP and JADAS-27 was calculated.

RESULTS

Of the 50 patients with JIA included in the study, there were 18 female and 32 male children. The median age of presentation to the hospital was 9 y (IQR 5.82-13). The median JADAS-27 was 14 (IQR 6, 20.25). The median serum calprotectin level was 45,375 ng/mL (IQR 30,725, 52,270; range 8,560-63,160 ng/mL). The median CRP was 35.4 mg/L (IQR 3.48, 80.3; range 0.02 and 107.4 mg/L). The levels of calprotectin in different JIA subtypes were not statistically different using Kruskal-Wallis test. The study also demonstrated a positive correlation between serum calprotectin with CRP and the JADAS-27 (r = 0.418).

CONCLUSION

The calprotectin levels in JIA were significantly higher than those reported in the literature irrespective of the subtype. Serum calprotectin positively correlated with CRP and JADAS-27 in children with JIA.

S100A8/A9: An emerging player in sepsis and sepsis-induced organ injury

Sepsis, the foremost contributor to mortality in intensive care unit patients, arises from an uncontrolled systemic response to invading infections, resulting in extensive harm across multiple organs and systems. Recently, S100A8/A9 has emerged as a promising biomarker for sepsis and sepsis-induced organ injury, and targeting S100A8/A9 appeared to ameliorate inflammation-induced tissue damage and improve adverse outcomes. S100A8/A9, a calcium-binding heterodimer mainly found in neutrophils and monocytes, serves as a causative molecule with pro-inflammatory and immunosuppressive properties, which are vital in the pathogenesis of sepsis. Therefore, improving our comprehension of how S100A8/A9 acts as a pathological player in the development of sepsis is imperative for advancing research on sepsis. Our review is the first-to the best of our knowledge-to discuss the biology of S100A8/A9 and its release mechanisms, summarize recent advances concerning the vital roles of S100A8/A9 in sepsis and the consequential organ damage, and underscore its potential as a promising diagnostic biomarker and therapeutic target for sepsis.

The clinical and experimental treatment of Juvenile Idiopathic Arthritis

Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic disease in children and comprises of multiple subtypes. The most relevant disease subtypes, grouped upon current insight in disease mechanisms, are nonsystemic (oligo- and polyarticular) JIA and systemic JIA (sJIA). In this review, we summarize some of the main proposed mechanisms of disease in both nonsystemic and sJIA and discuss how current therapeutic modalities target some of the pathogenic immune pathways. Chronic inflammation in nonsystemic JIA is the result of a complex interplay between effector and regulatory immune cell subsets, with adaptive immune cells, specifically T-cell subsets and antigen-presenting cells, in a central role. There is, however, also innate immune cell contribution. SJIA is nowadays recognized as an acquired chronic inflammatory disorder with striking autoinflammatory features in the first phase of the disease. Some sJIA patients develop a refractory disease course, with indications for involvement of adaptive immune pathways as well. Currently, therapeutic strategies are directed at suppressing effector mechanisms in both non-systemic and sJIA. These strategies are often not yet optimally tuned nor timed to the known active mechanisms of disease in individual patients in both non-systemic and sJIA. We discuss current treatment strategies in JIA, specifically the 'Step-up' and 'Treat to Target approach' and explore how increased insight into the biology of disease may translate into future more targeted strategies for this chronic inflammatory disease at relevant time points: preclinical disease, active disease, and clinically inactive disease.

S100A8/A9-alarmin promotes local myeloid-derived suppressor cell activation restricting severe autoimmune arthritis

Immune-suppressive effects of myeloid-derived suppressor cells (MDSCs) are well characterized during anti-tumor immunity. The complex mechanisms promoting MDSC development and their regulatory effects during autoimmune diseases are less understood. We demonstrate that the endogenous alarmin S100A8/A9 reprograms myeloid cells to a T cell suppressing phenotype during autoimmune arthritis. Treatment of myeloid precursors with S100-alarmins during differentiation induces MDSCs in a Toll-like receptor 4-dependent manner. Consequently, knockout of S100A8/A9 aggravates disease activity in collagen-induced arthritis due to a deficit of MDSCs in local lymph nodes, which could be corrected by adoptive transfer of S100-induced MDSCs. Blockade of MDSC function in vivo aggravates disease severity in arthritis. Therapeutic application of S100A8 induces MDSCs in vivo and suppresses the inflammatory phenotype of S100A9ko mice. Accordingly, the interplay of T cell-mediated autoimmunity with a defective innate immune regulation is crucial for autoimmune arthritis, which should be considered for future innovative therapeutic options.

An explorative study on proteomic analyses related to inflammation and pain in children with juvenile idiopathic arthritis

BACKGROUND

Our aim was attempting to find proteins involved in the pain process and correlating with pain but not degree of inflammation in children with juvenile idiopathic arthritis (JIA), using a proteomics panel.

METHODS

A total of 87 plasma samples were collected from 51 children with JIA (51 at diagnosis in a higher disease activity state, 18 at follow-up in a lower disease activity state) and 18 healthy controls. Relative levels of 92 proteins related to a wide range of biological processes in inflammation were obtained using a proximity extension assay panel. Comparisons between children with and without JIA, in different disease categories, by juvenile disease activity score (JADAS27) and degree of pain on a visual analogue scale (VAS), were performed using parametric and non-parametric statistical methods.

RESULTS

Nineteen proteins involved in arthritic inflammation, such as interleukin 6 (IL-6) and S100 protein A12, were higher in patients with JIA than controls, seven decreased significantly during treatment, and 18 correlated significantly with JADAS27. Three proteins correlated with pain VAS scores in unadjusted analyses: the glial cell line-derived neurotrophic factor (GDNF), transforming growth factor beta, and IL-18R1. Levels of GDNF correlated significantly with pain VAS scores but not with JADAS27.

CONCLUSIONS

Plasma levels of 18 of 92 tested proteins correlated with degree of disease activity. Levels of three proteins correlated with pain, and levels of one, GDNF, originating from neural cells, correlated with pain without correlating with inflammatory degree, suggesting that it may play a role in pain in JIA. Further studies in larger cohorts are warranted.

Inflammatory Biomarkers Can Differentiate Acute Lymphoblastic Leukemia with Arthropathy from Juvenile Idiopathic Arthritis Better Than Standard Blood Tests

OBJECTIVE

To evaluate the predictive value of biomarkers of inflammation like phagocyte-related S100 proteins and a panel of inflammatory cytokines in order to differentiate the child with acute lymphoblastic leukemia (ALL) from juvenile idiopathic arthritis (JIA).

STUDY DESIGN

In this cross-sectional study, we measured S100A9, S100A12, and 14 cytokines in serum from children with ALL (n = 150, including 27 with arthropathy) and JIA (n = 236). We constructed predictive models computing areas under the curve (AUC) as well as predicted probabilities in order to differentiate ALL from JIA. Logistic regression was used for predictions of ALL risk, considering the markers as the respective exposures. We performed internal validation using repeated 10-fold cross-validation and recalibration, adjusted for age.

RESULTS

In ALL, the levels of S100A9, S100A12, interleukin (IL)-1 beta, IL-4, IL-13, IL-17, matrix metalloproteinase-3, and myeloperoxidase were low compared with JIA (P < .001). IL-13 had an AUC of 100% (95% CI 100%-100%) due to no overlap between the serum levels in the 2 groups. Further, IL-4 and S100A9 had high predictive performance with AUCs of 99% (95% CI 97%-100%) and 98% (95% CI 94%-99%), respectively, exceeding both hemoglobin, platelets, C-reactive protein, and erythrocyte sedimentation rate.

CONCLUSIONS

The biomarkers S100A9, IL-4, and IL-13 might be valuable markers to differentiate ALL from JIA.

Complex regulation of alarmins S100A8/A9 and secretion via gasdermin D pores exacerbates autoinflammation in familial Mediterranean fever

BACKGROUND

Familial Mediterranean fever (FMF), caused by mutations in the pyrin-encoding MEFV gene, is characterized by uncontrolled caspase-1 activation and IL-1β secretion. A similar mechanism drives inflammation in cryopyrin-associated periodic fever syndrome (CAPS) caused by mutations in NLRP3. CAPS and FMF, however, result in largely different clinical manifestations, pointing to additional, autoinflammatory pathways involved in FMF. Another hallmark of FMF is extraordinarily high expression of S100A8 and S100A9. These alarmins are ligands of Toll-like receptor 4 and amplifiers of inflammation. However, the relevance of this inflammatory pathway for the pathogenesis of FMF is unknown.

OBJECTIVE

This study investigated whether mutations in pyrin result in specific secretion of S100A8/A9 alarmins through gasdermin D pores' amplifying FMF pathology.

METHODS

S100A8/A9 levels in FMF patients were quantified by enzyme-linked immunosorbent assay. In vitro models with knockout cell lines and specific protein inhibitors were used to unravel the S100A8/A9 secretion mechanism. The impact of S100A8/A9 to the pathophysiology of FMF was analyzed with FMF (MEFVV726A/V726A) and S100A9-/- mouse models. Pyrin-S100A8/A9 interaction was investigated by coimmunoprecipitation, immunofluorescence, and enzyme-linked immunosorbent assay studies.

RESULTS

The S100A8/A9 complexes directly interacted with pyrin. Knocking out pyrin, caspase-1, or gasdermin D inhibited the secretion of these S100 alarmins. Inflammatory S100A8/A9 dimers were inactivated by tetramer formation. Blocking this inactivation by targeted S100A9 deletion in a murine FMF model demonstrated the relevance of this novel autoinflammatory pathway in FMF.

CONCLUSION

This is the first proof that members of the S100 alarmin family are released in a pyrin/caspase-1/gasdermin D-dependent pathway and directly drive autoinflammation in vivo.

Gene expression of S100a8/a9 predicts Staphylococcus aureus-induced septic arthritis in mice

Septic arthritis is the most aggressive joint disease associated with high morbidity and mortality. The interplay of the host immune system with the invading pathogens impacts the pathophysiology of septic arthritis. Early antibiotic treatment is crucial for a better prognosis to save the patients from severe bone damage and later joint dysfunction. To date, there are no specific predictive biomarkers for septic arthritis. Transcriptome sequencing analysis identified S100a8/a9 genes to be highly expressed in septic arthritis compared to non-septic arthritis at the early course of infection in an Staphylococcus aureus septic arthritis mouse model. Importantly, downregulation of S100a8/a9 mRNA expression at the early course of infection was noticed in mice infected with the S. aureus Sortase A/B mutant strain totally lacking arthritogenic capacity compared with the mice infected with parental S. aureus arthritogenic strain. The mice infected intra-articularly with the S. aureus arthritogenic strain significantly increased S100a8/a9 protein expression levels in joints over time. Intriguingly, the synthetic bacterial lipopeptide Pam2CSK4 was more potent than Pam3CSK4 in inducing S100a8/a9 release upon intra-articular injection of these lipopeptides into the mouse knee joints. Such an effect was dependent on the presence of monocytes/macrophages. In conclusion, S100a8/a9 gene expression may serve as a potential biomarker to predict septic arthritis, enabling the development of more effective treatment strategies.

Heterogeneous effects of S100 proteins during cell interactions between immune cells and stromal cells from synovium or skin

Cell interactions represent an important mechanism involved in the pathogenesis of chronic inflammation. The key S100 proteins A8 and A9 have been studied in several models of chronic inflammatory diseases with highly heterogeneous conclusions. In this context, the aim of this study was to determine the role of cell interactions on S100 protein production and their effect on cytokine production during cell interactions, between immune and stromal cells from synovium or skin. Peripheral blood mononuclear cells (PBMC) were cultured alone or with synoviocytes or skin fibroblasts, with or without phytohemagglutinin, exogenous A8, A9, A8/A9 proteins or anti-A8/A9 antibody. Production of IL-6, IL-1β, IL-17, TNF, A8, A9, and A8/A9 was measured by ELISA. Cell interactions with synoviocytes had no effect on A8, A9, or A8/A9 secretion, while cell interactions with skin fibroblasts decreased A8 production. This highlights the importance of stromal cell origin. The addition of S100 proteins in co-cultures with synoviocytes did not increase the production of IL-6, IL-17, or IL-1β, except for an increase of IL-6 secretion with A8. The presence of anti-S100A8/A9 antibody did not show obvious effects. Low concentration or absence of serum in the culture medium decreased the production of IL-17, IL-6, and IL-1β but despite these conditions, the addition of S100 proteins did not increase cytokine secretion. In conclusion, the role of A8/A9 in cell interactions during chronic inflammation appears complex and heterogeneous, depending on multiple factors, notably the origin of stromal cells that can affect their secretion.

Pre-treatment calprotectin (MRP8/14) provides no added value to testing CRP alone in terms of predicting response to TNF inhibitors in rheumatoid arthritis in a post hoc analysis

OBJECTIVES

The inflammatory protein calprotectin (MRP8/14) has been identified as a promising biomarker of treatment response in rheumatoid arthritis (RA). Our aim was to test MRP8/14 as a biomarker of response to tumour necrosis factor (TNF)-inhibitors in the largest RA cohort to date and to compare with C-reactive protein (CRP).

METHODS

Serum MRP8/14 was measured in 470 patients with RA about to commence treatment with adalimumab (n=196) or etanercept (n=274). Additionally, MRP8/14 was measured in the 3-month sera of 179 adalimumab-treated patients. Response was determined using European League against Rheumatism (EULAR) response criteria calculated using the traditional 4-component (4C) DAS28-CRP and alternate validated versions using 3-component (3C) and 2-component (2C), clinical disease activity index (CDAI) improvement criteria and change in individual outcome measures. Logistic/linear regression models were fitted for response outcome.

RESULTS

In the 3C and 2C models, patients with RA were 1.92 (CI: 1.04 to 3.54) and 2.03 (CI: 1.09 to 3.78) times more likely to be classified as EULAR responders if they had high (75th quartile) pre-treatment levels of MRP8/14 compared with low (25th quartile). No significant associations were observed for the 4C model. When only using CRP as a predictor, in the 3C and 2C analyses, patients above the 75th quartile were 3.79 (CI: 1.81 to 7.93) and 3.58 (CI: 1.74 to 7.35) times more likely to be EULAR responders and addition of MRP8/14 did not significantly improve model fit (p values=0.62 and 0.80, respectively). No significant associations were observed in the 4C analysis. Exclusion of CRP from the outcome measure (CDAI) did not result in any significant associations with MRP8/14 (OR 1.00 (CI: 0.99 to 1.01), suggesting that the associations were due to the correlation with CRP and that there is no additional utility of MRP8/14 beyond use of CRP in patients with RA starting TNFi therapy.

CONCLUSION

Beyond correlation with CRP, we found no evidence to suggest that MRP8/14 explains additional variability in response to TNFi in patients with RA over and above CRP alone.

Plasma Levels of MRP-8/14 Associate With Neutrophil Recovery, Bacterial Bloodstream Infections, and Engraftment Syndrome Following Pediatric Allogeneic Hematopoietic Stem Cell Transplantation

Neutrophil engraftment is essential for the successful outcome after allogeneic hematopoietic stem cell transplantation (HSCT), but neutrophil activation may also induce transplant-related complications. Myeloid-related protein (MRP)-8/14 is expressed in granulocytes during inflammatory conditions and secreted in response to tissue damage along with the release of pro-inflammatory cytokines together with leukocyte recruitment and activation. In this study, we investigated associations between levels of the neutrophil activition marker MRP-8/14, neutrophil recovery and toxicities after pediatric HSCT. We included 73 children undergoing allogeneic HSCT using bone marrow or peripheral blood stem cell grafts from matched sibling or unrelated donors. Plasma levels of MRP-8/14 were measured by enzyme-linked immunosorbent assay from preconditioning until 6 months after transplantation. Overall, MRP-8/14 levels decreased from pre-conditioning to a nadir at day 7 and then rose again until day 28, preceding the reappearance of neutrophils. MRP-8/14 levels were significantly reduced at day 14 in patients with delayed neutrophil engraftment compared with patients who engrafted by day 21 (0.20 versus 0.48 μg/mL, P = .0012) and in patients who developed bacterial bloodstream infections compared to patients without this complication (0.2 versus 0.36 μg/mL, P = .048). Patients developing engraftment syndrome had significantly elevated MRP-8/14 levels at day 7 and 21 compared to patients without engraftment syndrome (0.32 versus 0.2 μg/mL, P = .042 and 1.9 versus 0.80 μg/mL, P = .039, respectively), as well as increased neutrophil counts from day 9 to 25 (P ≤ .016). Similarly, neutrophil counts were increased at day 13 to 17 in patients with acute graft-versus-host disease grade III-IV compared with grade 0-II. This study is the first to monitor neutrophil activation by MRP-8/14 in HSCT patients in relation to infectious, as well as noninfectious post-transplantation complications. Our results provide increased insights into the pathophysiology of these complications, and further studies should explore the potential use of MRP-8/14 as a clinically useful biomarker.

Proinflammatory S100A9 stimulates TLR4/NF-κB signaling pathways causing enhanced phagocytic capacity of microglial cells

Alzheimer's disease (AD) is the main cause of dementia, affecting the increasingly aging population. Growing evidence indicates that neuro-inflammation plays crucial roles, e.g., the association between AD risk genes with innate immune functions. In this study, we demonstrate that moderate concentrations of pro-inflammatory cytokine S100A9 regulate immune response of BV2 microglial cells, i.e., the phagocytic capacity, reflected by elevated number of 1 μm diameter Dsred-stained latex beads in the cytoplasm. In contrast, at high S100A9 concentrations, both the viability and phagocytic capacity of BV2 cells drop substantially. Furthermore, it is uncovered that S100A9 affects phagocytosis of microglia via NF-κB signaling pathways. Application of related target-specific drugs, i.e., IKK and TLR4 inhibitors, effectively suppresses BV2 cells' immune responses. These results suggest that pro-inflammatory S100A9 activates microglial phagocytosis, and possibly contributes to the clearance of amyloidogenic species at the early stage of AD.

Patients with SARS-CoV-2-Induced Viral Sepsis Simultaneously Show Immune Activation, Impaired Immune Function and a Procoagulatory Disease State

BACKGROUND

It is widely accepted that SARS-CoV-2 causes a dysregulation of immune and coagulation processes. In severely affected patients, viral sepsis may result in life endangering multiple organ dysfunction. Furthermore, most therapies for COVID-19 patients target either the immune system or coagulation processes. As the exact mechanism causing SARS-CoV-2-induced morbidity and mortality was unknown, we started an in-depth analysis of immunologic and coagulation processes.

METHODS

127 COVID-19 patients were treated at the University Hospital Essen, Germany, between May 2020 and February 2022. Patients were divided according to their maximum COVID-19 WHO ordinal severity score (WHO 0-10) into hospitalized patients with a non-severe course of disease (WHO 4-5, n = 52) and those with a severe course of disease (WHO 6-10, n = 75). Non-infected individuals served as healthy controls (WHO 0, n = 42). Blood was analyzed with respect to cell numbers, clotting factors, as well as pro- and anti-inflammatory mediators in plasma. As functional parameters, phagocytosis and inflammatory responses to LPS and antigen-specific stimulation were determined in monocytes, granulocytes, and T cells using flow cytometry.

FINDINGS

In the present study, immune and coagulation systems were analyzed simultaneously. Interestingly, many severe COVID-19 patients showed an upregulation of pro-inflammatory mediators and at the same time clear signs of immunosuppression. Furthermore, severe COVID-19 patients not only exhibited a disturbed immune system, but in addition showed a pronounced pro-coagulation phenotype with impaired fibrinolysis. Therefore, our study adds another puzzle piece to the already complex picture of COVID-19 pathology implying that therapies in COVID-19 must be individualized.

CONCLUSION

Despite years of research, COVID-19 has not been understood completely and still no therapies exist, fitting all requirements and phases of COVID-19 disease. This observation is highly reminiscent to sepsis. Research in sepsis has been going on for decades, while the disease is still not completely understood and therapies fitting all patients are lacking as well. In both septic and COVID-19 patients, immune activation can be accompanied by immune paralysis, complicating therapeutic intervention. Accordingly, therapies that lower immune activation may cause detrimental effects in patients, who are immune paralyzed by viral infections or sepsis. We therefore suggest individualizing therapies and to broaden the spectrum of immunological parameters analyzed before therapy. Only if the immune status of a patient is understood, can a therapeutic intervention be successful.

The Role of Serum Calprotectin in Defining Disease Outcomes in Non-Systemic Juvenile Idiopathic Arthritis: A Pilot Study

Serum calprotectin (MRP8/14) is currently being studied as a promising biomarker of disease activity and outcome in patients with juvenile idiopathic arthritis (JIA) but the data in the literature are conflicting. The aim of our study was to investigate the potential role of serum calprotectin as biomarker of disease activity and flare/remission in a group of nsJIA patients during a follow-up period of 18 months. In this prospective longitudinal study, two groups of patients with ns-JIA (55 active patients and 56 patients in remission according to Wallace's criteria) and a control group (50 children) were recruited at baseline from January 2020 to September 2021. JIA patients were followed for up to 18 months at four timepoints: 3 months (T1), 6 months (T2), 12 months (T3) and 18 months (T4). At each timepoint, the following were recorded: JADAS27, blood counts, ESR, CRP, albumin, ferritin and serum calprotectin. To illustrate the performance of calprotectin, Kaplan-Meier curves were constructed from baseline to relapse/remission, dichotomizing patients at baseline in positive/negative on the basis progressive calprotectin cut-offs. Associations between baseline factors and relapse were determined using Cox regression models. Multivariate models were constructed to analyze the effect of covariates. Comparing baseline clinical and laboratory data of the three groups (active vs. inactive JIA vs. controls), only serum calprotectin reached statistical significance (active patients vs. inactive (p = 0.0016) and vs. controls (p = 0.0012)). In the inactive group, during the 18 months of follow up, 31 patients (55.3%) had a relapse. Comparing the baseline data of relapsers vs. non-relapsers, serum calprotectin showed higher levels (p = 0.001) in relapsers. In survival analysis, a log rank test showed significant differences of up to 12 ng/mL (p = 0.045). Multivariate Cox regression confirmed that only baseline calprotectin levels were independently associated with disease recurrence. In the active group, in the 12 months of follow-up, 19 patients (38%) entered remission of the disease. In addition, in this group, the only statistical difference at the baseline was the value of MPR8/14 (p = 0.0001). Log rank test showed significant differences up to 10 ng/mL (p = 0.003). In the multivariate Cox regression, serum calprotectin levels at baseline were independently associated with remission. In conclusion, our study would suggest a dual role for calprotectin in predicting future relapse and treatment response in patients with nsJIA, thus influencing therapeutic decisions and management of these patients during follow up.

Circulatory levels of alarmins in patients with non-segmental vitiligo: Potential biomarkers for disease diagnosis and activity/severity assessment

Background

Non-segmental vitiligo (NSV) is an autoimmune skin disorder that is difficult to determine disease activity/severity and thus to treat. Alarmins have emerged as promising biomarkers in various diseases, so further confirmation of their potential roles in NSV would be of considerable value. With the present work, we aimed to determine the serum levels of alarmins in patients with NSV, correlate these alarmins with disease activity and severity, and analyze the predictive value of the combination of these markers.

Methods

104 NSV patients and 56 healthy controls were enrolled at the Xijing Hospital of Fourth Military Medical University between September 1, 2018, and June 30, 2019. The serum levels of alarmins (including IL-33, IL-1α, S100A9, S100A12, S100B, and HMGB1) were measured with enzyme-linked immunosorbent assays. The predictive performance of these biomarkers was evaluated with the area under the receiver operating characteristic curve (AUC), sensitivity, specificity, and other representative statistics.

Results

A total of 104 patients with NSV (mean [SD] age, 34.2 [13.0] years; 62 [59.6%] male) and 56 healthy controls (mean [SD] age, 34.8 [13.5] years; 34 [60.7%] male) were enrolled. For vitiligo diagnosis, S100B had the highest sensitivity (92.31%), whereas HMGB1 had the highest specificity (85.71%); the combination of IL-1α, S100B, S100A9, and HMGB1 increased the AUC value to 0.925, with a sensitivity of 87.50% and a specificity of 85.71%. Multivariate logistic regression analysis showed S100B (OR, 1.019; 95% CI, 1.002-1.038; P =0.03), S100A9 (OR, 1.002; 95% CI, 1.001-1.003; P<0.001), and HMGB1 (OR, 1.915; 95% CI, 1.186-3.091; P =0.008) were significantly associated with vitiligo activity. S100A9 had the highest accuracy in discriminating patients at the active stage from the stable stage, with an AUC value of 0.827. The combination of these alarmins had an AUC value of 0.860 to assess disease activity, with a sensitivity of 90.00% and a specificity of 72.97%. Furthermore, S100B (r=0.61, P <0.001), S100A9 (r=0.33, P <0.001), and HMGB1 (r = 0.51, P <0.001) levels were positively correlated with the affected body surface area (BSA) in NSV patients.

Conclusions

Serum S100B, S100A9, and HMGB1 might be biomarkers for diagnosing and assessing the activity/severity of NSV, either used alone or in combination.

The alarmins high mobility group box protein 1 and S100A8/A9 display different inflammatory profiles after acute knee injury

OBJECTIVE

To compare the concentrations of high mobility group box 1 protein (HMGB1) and S100A8/A9 in synovial fluid between patients with knee injuries and osteoarthritis (OA), and knee healthy subjects. To investigate associations of alarmin levels with different joint injuries and with biomarkers of inflammation, Wnt signaling, complement system, bone and cartilage degradation.

METHODS

HMGB1 and S100A8/A9 were measured in synovial fluid by immunoassays in patients with knee injuries, with OA and from knee healthy subjects, and were related to time from injury and with biomarkers obtained from previous studies. Hierarchical cluster and enrichment analyses of biomarkers associated to HMGB1 and S100A8/A9 were performed.

RESULTS

The synovial fluid HMGB1 and S100A8/A9 concentrations were increased early after knee injury; S100A8/A9 levels were negatively associated to time after injury and was lower in the old compared to recent injury group, while HMGB1 was not associated to time after injury. The S100A8/A9 levels were also increased in OA. The initial inflammatory response was similar between the alarmins, and HMGB1 and S100A8/A9 shared 9 out of 20 enriched pathways. The alarmins displayed distinct response profiles, HMGB1 being associated to cartilage biomarkers while S100A8/A9 was associated to proinflammatory cytokines.

CONCLUSIONS

HMGB1 and S100A8/A9 are increased as an immediate response to knee trauma. While they share many features in inflammatory and immunoregulatory mechanisms, S100A8/A9 and HMGB1 are associated to different downstream responses, which may have impact on the OA progression after acute knee injuries.

Myeloid-related protein 8/14 in plasma and serum in patients with new-onset juvenile idiopathic arthritis in real-world setting in a single center

OBJECTIVE

The aim of this study was to analyze the usefulness of myeloid-related protein 8/14 (MRP8/14) in the prediction of disease course in a real-world setting for patients with new-onset juvenile idiopathic arthritis (JIA), to identify the relationship between MRP8/14 and disease activity using the physician's global assessment of disease activity (PGA), and determine whether the MRP8/14 levels measured in serum and plasma are equally useful.

METHODS

In this prospective follow-up study, 87 new-onset non-systemic JIA patients were studied. Blood and synovial fluid samples were collected prior to any antirheumatic medication use. MRP8/14 was measured from serum (S-MRP8/14), plasma (P-MRP8/14), and synovial fluid samples using ELISA.

RESULTS

The baseline MRP8/14 blood levels were significantly higher in patients using synthetic antirheumatic drugs than in patients with no systemic medications at 1 year after diagnosis in serum (mean 298 vs. 198 ng/ml, P < 0.001) and in plasma (mean 291 vs. 137 ng/ml, P = 0.001). MRP8/14 levels at the time of JIA diagnosis were higher in patients who started methotrexate during 1.5-year follow-up compared to those who achieved long-lasting inactive disease status without systemic medications (serum: mean 298 vs. 219 ng/ml, P = 0.006 and plasma: 296 vs. 141 ng/ml, P = 0.001). P-MRP8/14 was the most effective predictive variable for disease activity (by PGA) in linear multivariate regression model (combined to ESR, CRP, leukocytes, and neutrophils), whereas S-MRP8/14 was not significant.

CONCLUSION

Blood MRP8/14 levels at baseline seem to predict disease course in new-onset JIA patients. P-MRP8/14 might be better than S-MRP8/14 when assessing disease activity at the time of JIA diagnosis.

S100A8 in Serum, Urine, and Saliva as a Potential Biomarker for Systemic Lupus Erythematosus

Objectives

This study aimed to elucidate the potential of serum, urine, and saliva S100 calcium-binding protein A8 protein (S100A8) levels as biomarkers for systemic lupus erythematosus (SLE).

Methods

Serum, urine, and saliva samples were obtained from 249 patients with SLE from the Ajou lupus cohort and 52 age- and sex-matched healthy controls (HCs). The concentrations of S100A8 were quantified using an ELISA, and a receiver operating characteristic curve was used to analyze whether they may be used as biomarkers for diagnosing SLE.

Results

Among 249 SLE patients included in our study, the mean SLE disease activity index (SLEDAI)-2K was 7.16 ± 5.61, and the number of patients with lupus flare was 11. Patients with SLE showed a 2.7-fold increase in serum S100A8 levels compared with that in HCs (1,890.6 vs. 709 pg/ml, p &lt; 0.001). In urine and saliva, the average S100A8 levels were significantly higher in patients with SLE compared with those in HCs (urine, 2,029.4 vs. 1,096.7 pg/ml, p = 0.001; saliva, 290,496.3 vs. 47,742 pg/ml, p &lt; 0.001). For SLE diagnosis, the area under the receiver operating characteristic curve was 0.831 for serum S100A8 (95% CI, 0.765–0.897), 0.751 for urine S100A8 (95% CI, 0.648–0.854), and 0.729 for salivary S100A8 (95% CI, 0.646–0.812). Pearson’s correlation analysis showed that S100A8 in serum, urine, and saliva was significantly associated with the SLEDAI (r = 0.267, p &lt; 0.001; r = 0.274, p &lt; 0.001; and r = 0.629, p &lt; 0.001, respectively). Among the clinical manifestations, nephritis was the most influential factor related to SLE in the concentration of S100A8 in serum, urine, and saliva.

Conclusion

This is the first study to show that the expression of S100A8 in serum, urine, and saliva is significantly higher in patients with SLE than in HCs and is associated with disease activity markers. Therefore, we suggest that S100A8 protein could be a potential biomarker for SLE.

S100A8 (rs3806232) gene polymorphism and S100A8 serum level in psoriasis vulgaris patients: A preliminary study

BACKGROUND

S100A8 single nucleotide polymorphism (SNP) and S100A8 blood level are related to many inflammatory disorders with no available conclusion in psoriasis.

AIM

to evaluate the possible role of S100A8 in psoriasis pathogenesis through analyzing its S100A8 (rs3806232) gene polymorphism and S100A8 serum level in psoriasis vulgaris patients, in addition to correlate the detected results with severity psoriasis in those patients.

METHODS

This case-control study was conducted on 50 patients having psoriasis vulgaris, and 26 controls. Severity of psoriasis was evaluated using psoriasis area and severity index (PASI) score. S100A8 serum level and S100A8 (rs3806232) SNP were evaluated by ELISA and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) respectively.

RESULTS

Serum S100A8 level was significantly higher in psoriatic patients than controls and was positively correlated with PASI score (r=0.826, p<0.001). S100A8 (rs3806232) AA genotype and A allele were significantly increased among psoriasis patients than controls (p<0.001) increasing risk of psoriasis development by about 5, 12 and 6 times than AG, GG and G allele. AA genotype was significantly associated with psoriasis severity (p=0.005), and high S100A8 serum levels (P= 0.018).

CONCLUSIONS

Circulating S100A8 could associated with disease severity and have an active role in psoriasis pathogenesis. S100A8 (rs3806232) SNP (AA genotype and A allele) might contribute to development and severity of psoriasis in the Egyptian population.

Analytical and clinical evaluation of DiaSorin Liaison® Calprotectin fecal assay adapted for serum samples

Background

Calprotectin is a calcium‐binding protein that can be measured in serum, plasma, and feces. Increased serum and plasma calprotectin concentrations have been found in chronic inflammatory rheumatic disorders. An analytical and clinical evaluation of the DiaSorin Liaison® fecal Calprotectin assay using LIAISON® XL was performed.

Methods

The protocol included an analytical and clinical evaluation in which imprecision, the linearity of dilution, differences between serum and plasma samples and method comparison with CalproLab™ ELISA kit were assessed. Serum calprotectin concentrations in active (n = 26) and remission (n = 23) rheumatoid arthritis (RA) patients were compared.

Results

The intra‐day and inter‐day analytical imprecision CVs ranged from 2.9% to 4.0% and 2.7% to 10.4%, respectively. Correlation between measured and expected values was high (R > 0.99), indicating good linearity. The Wilcoxon signed‐rank test showed that serum and plasma matched samples presented statistically significant differences (p < 0.001) being the highest concentrations of calprotectin observed in serum samples. Deming regression equation was as follows: Diasorin calprotectin (μg/ml) = −0.32 (95% CI: −0.65 ‐ −0.05) +1.58 (95% CI: 1.42–1.79).* Calprolab calprotectin (μg/ml). Significantly higher serum calprotectin levels were found in RA patients with active disease when compared to patients with low disease activity or in clinical remission (mean ± SD) [(3.35 μg/ml ± 1.55) vs. (1.63 μg/ml ± 0.52), p < 0.001] and these levels correlated well with all disease activity indices.

Conclusions

The DiaSorin Liaison® fecal Calprotectin assay adapted for serum samples showed adequate technical performances and the clinical performances were similar to other assays.

Serum Calprotectin a Potential Biomarker in Juvenile Idiopathic Arthritis: A Meta-Analysis

Juvenile idiopathic arthritis (JIA) is the most common inflammatory chronic disease affecting children and adolescents. Today, there are no specific biomarkers of inflammation. Therefore, it is important to identify new markers as predictors of disease activity. Recently, some researchers have directed their interest toward a protein, calprotectin (CLP), as a potential biomarker. The primary objective of our systematic review and meta-analysis was to analyze the possible role of CLP in JIA. Method: A literature search was conducted using PubMed, EMBASE, Scopus, Science Direct on 10 August 2021. The selection of studies was made using the PRISMA 2020 guidelines. Cohen’s d with 95% CI and p-value were used as a measure of effect size. The random effects model was used to account for different sources of variation among studies. Heterogeneity was assessed using Q statistics and I². The publication bias was analyzed and represented by a funnel plot, and funnel plot symmetry was assessed with Egger’s test. Results: Our results at follow-up showed a statistically significant difference between patients with active disease compared to patients with inactive disease: 0.39 (0.16; 0.62), p = 0.001; without statistical heterogeneity. Another important aspect that emerged were the differences between the systemic disease form and any form of inactive disease showing a different concentration of calprotectin: 0.74 (0.40; 1.08), p < 0.001; without statistical heterogeneity. On the other hand, meta-regression analyses performed on gender, age, duration of disease, percentage of patients with ANA+ or RF+, medium value of ESR or CRP were not statistically significant. A statistically significant difference in serum calprotectin concentration between patients with JIA and healthy controls were observed. In fact, it presented lower values in the control group. Conclusions: The use of serum CLP could represent, in the future, a useful tool in JIA in order to stratify disease activity more accurately and may aid a more tailored approach to drug of choice in children with JIA. Further studies are needed to evaluate CLP as a predictor of flare in combination with other potential biomarkers of subclinical disease activity.

S100A8 and S100A9, biomarkers of SARS-Cov2-infected patients, suppress HIV replication in primary macrophages

S100A8 and S100A9 are members of the Alarmin family; these proteins are abundantly expressed in neutrophils and form a heterodimer complex. Recently, both proteins were identified as novel biomarkers of SARS-CoV-2 infection and were shown to play key roles in inducing an aggressive inflammatory response by mediating the release of large amounts of pro-inflammatory cytokines, called the “cytokine storm.” Although co-infection with SARS-CoV-2 in people living with HIV-1 may result in an immunocompromised status, the role of the S100A8/A9 complex in HIV-1 replication in primary T cells and macrophages is still unclear. Here, we evaluated the roles of the proteins in HIV replication to elucidate their functions. We found that the complex had no impact on virus replication in both cell types; however, the subunits of S100A8 and S100A9 inhibits HIV in macrophages. These findings provide important insights into the regulation of HIV viral loads in SARS-CoV2 co-infection.

Cancer-associated fibroblasts induce an aggressive phenotypic shift in non-malignant breast epithelial cells via interleukin-8 and S100A8

Cancer-associated fibroblasts (CAFs) in the tumor microenvironment have been associated with tumor progression in breast cancer. Although crosstalk between breast cancer cells and CAFs has been studied, the effect of CAFs on non-neoplastic breast epithelial cells is not fully understood to date. Here, we investigated the effect of CAFs on aggressive phenotypes in non-neoplastic MCF10A breast epithelial cells. CAFs induced epithelial-to-mesenchymal transition (EMT) and invasive phenotype in MCF10A cells. S100A8, a potential prognostic marker in several cancers, was markedly increased in MCF10A cells by CAFs. S100A8 was crucial for CAFs-induced invasive phenotype of MCF10A cells. Among cytokines increased by CAFs, interleukin (IL)-8 induced S100A8 through transcription factors p65 NF-κB and C/EBPβ. In a xenograft mouse model with MCF10A cells and CAFs, tumor was not developed, suggesting that coinjection with CAFs may not be sufficient for in vivo tumorigenicity of MCF10A cells. Xenograft mouse tumor models with MDA-MB-231 breast carcinoma cells provided an in vivo evidence for the effect of CAFs on breast cancer progression as well as a crucial role of IL-8 in tumor growth and S100A8 expression in vivo. Using a tissue microarray of human breast cancer, we showed that S100A8 expression was correlated with poor outcomes. S100A8 expression was more frequently detected in cancer-adjacent normal human breast tissues than in normal breast tissues. Together, this study elucidated a novel mechanism for the acquisition of invasive phenotype of non-neoplastic breast cells induced by CAFs, suggesting that targeting IL-8 and S100A8 may be an effective strategy against breast cancer.

IL-8 and IFN-γ as Preoperative Predictors of the Outcome of Tonsillectomy

OBJECTIVES

Tonsillectomy (TE) and tonsillotomy (TO) due to recurrent episodes of acute tonsillitis (RAT) belong to the most frequent surgical procedures. However, an adequate objective marker predicting the outcome of TE/TO preoperatively is missing.

METHODS

Patients with RAT who underwent TE/TO (n = 31) were included in this pilot study. A panel of cytokines and chemokines in serum and saliva were determined preoperatively. Health-related quality of life was assessed pre- and postoperatively by the Tonsillectomy Outcome Inventory-14.

RESULTS

Health-related quality of life improved significantly after surgery. Increased serum levels of interleukin-8 (IL-8) and interferon gamma (IFN-γ) are associated with a less successful outcome. No correlation between the number of acute tonsillitis episodes and the health-related quality of life after TE or TO could be observed.

CONCLUSIONS

Tonsillectomy and TO improve health-related quality of life independently from the number of past acute tonsillitis episodes. Interleukin-8 and IFN-γ in serum may serve as promising markers, predicting the benefit of TE or TO for patients preoperatively.

Serum calprotectin (S100A8/A9): a promising biomarker in diagnosis and follow-up in different subgroups of juvenile idiopathic arthritis

Introduction

In the management of juvenile idiopathic arthritis (JIA), there is a lack of diagnostic and prognostic biomarkers. This study assesses the use of serum calprotectin (sCal) as a marker to monitor disease activity, and as a classification and prognosis tool of response to treatment or risk of flares in patients with JIA.

Methods

Eighty-one patients with JIA from the CAP48 multicentric cohort were included in this study, as well as 11 non-paediatric healthy controls. An ELISA method was used to quantify sCal with a commercial kit.

Results

Patients with an active disease compared with healthy controls and with patients with inactive disease showed an eightfold and a twofold increased level of sCal, respectively. sCal was found to be correlated with the C-reactive protein (CRP) and even more strongly with the erythrocyte sedimentation rate. Evolution of DAS28 scores correlated well with evolution of sCal, as opposed to evolution of CRP. With regard to CRP, sCal could differentiate forms with active oligoarthritis from polyarthritis and systemic forms. However, sCal brought an added value compared with the CRP as a prognosis marker. Indeed, patients with active disease and reaching minimal disease activity (according to Juvenile Arthritis Disease Activity Score) at 6 months following the test had higher sCal levels, while patients with inactive disease had higher sCal levels if a flare was observed up to 3–9 months following the test.

Conclusions

This study confirms the potential uses of sCal as a biomarker in the diagnosis and follow-up of JIA.

Novel molecular biomarkers and diagnosis of acute appendicitis in children

Reliable and efficient diagnosis of pediatric appendicitis is essential for the establishment of a clinical management plan and improvement of patient outcomes. Current strategies used to diagnose a child presenting with a suspected appendicitis include laboratory studies, clinical scores and diagnostic imaging. Although these modalities work in conjunction with each other, one optimal diagnostic strategy has yet to be agreed upon. The recent introduction of precision medicine techniques such as genomics, transcriptomics, proteomics and metabolomics has increased both the diagnostic sensitivity and specificity of appendicitis. Using these novel strategies, the integration of precision medicine into clinical practice via point-of-care technologies is a plausible future. These technologies would assist in the screening, diagnosis and prognosis of pediatric appendicitis.

Maternal serum calprotectin level in intrahepatic cholestasis of pregnancy

AIM

This study aimed to investigate maternal serum levels of calprotectin in patients with intrahepatic cholestasis of pregnancy (ICP) and to compare these with serum calprotectin levels in healthy pregnant women.

METHODS

Ninety pregnant women (ICP group, n = 45; healthy control group, n = 45) were included in the study. The gestational age and body mass index of the participants in the two groups were similar. This prospective cross-sectional study was conducted between November 2019 and May 2020 in the perinatology department of University of Health Sciences Doctor Zekai Tahir Burak Women's Education Hospital, Ankara, Turkey. Patients were recruited from those attending the perinatology outpatient and inpatient clinics. Biochemical (alanine aminotransferase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), total bilirubin), fasting bile acid, hemogram, and calprotectin parameters of maternal blood were evaluated.

RESULTS

The mean fasting bile acid value in the ICP group was 30.3 ± 27.3 μmol, with severe ICP present in 11 (24.4%) patients. ALT, AST, LDH, total bilirubin, and mean platelet volume (MPV) values in the ICP group were higher and the red cell distribution width (RDW) value was lower than those in the control group (p < 0.001). The mean serum calprotectin levels in the control group and ICP group were 48.0 ± 10.4 and 765.4 ± 126.8 μg, respectively (p < 0.001). There was no significant correlation between serum fasting bile acid levels and serum calprotectin levels in the ICP group (p > 0.005).

CONCLUSION

Serum levels of calprotectin in patients with ICP were higher than those in healthy pregnant women. The serum calprotectin level may be an important diagnostic marker of ICP.

Increased levels of S100A8/A9, IL-1ß and IL-18 as a novel biomarker for recurrent tonsillitis

Background

Acute tonsillitis represents one of the most frequent reasons patients seek primary medical care and otorhinolaryngology consultation. Therefore, recurrent episodes of acute tonsillitis (RAT), also called chronic tonsillitis, exhaust a substantial amount of medical and financial resources. Diagnosis of tonsillitis depends on a physical examination, which therefore does not allow for a reliable differentiation between viral and bacterial infection. However, the frequency of bacterial infections during the previous three years is currently being used as the major deciding factor in patient selection for tonsillectomy. The aim of the present study was to determine an objective biomarker to help in the identification of patients suffering from recurrent tonsillitis.

Results

By analyzing a panel of cytokines and chemokines in serum and saliva of patients with RAT compared to healthy controls, increased levels of IL-1ß (153.7 ± 48.5 pg/ml vs 23.3 ± 6.6 pg/ml, p = 0.021), IL-18 (120.2 ± 16.5 vs 50.6 ± 9.3 pg/ml, p = 0.007) and/or S100A8/A9 (996 ± 102 ng/ml vs 546 ± 86 ng/ml, p = 0.042) could be observed in patients suffering from RAT. Cut-off values of these parameters were determined and combined to a new RAT-score allowing for reliable identification of patients suffering from recurrent tonsillitis with a sensitivity of 95% and a specificity of 88%.

Conclusion

The RAT-score represents the first objective criterion as a tool for the diagnosis of recurrent tonsillitis and it also improves patient selection for tonsillectomy.

Reactivation of dormant tumor cells by modified lipids derived from stress-activated neutrophils

Tumor recurrence years after seemingly successful treatment of primary tumors is one of the major causes of mortality in patients with cancer. Reactivation of dormant tumor cells is largely responsible for this phenomenon. Using dormancy models of lung and ovarian cancer, we found a specific mechanism, mediated by stress and neutrophils, that may govern this process. Stress hormones cause rapid release of proinflammatory S100A8/A9 proteins by neutrophils. S100A8/A9 induce activation of myeloperoxidase, resulting in accumulation of oxidized lipids in these cells. Upon release from neutrophils, these lipids up-regulate the fibroblast growth factor pathway in tumor cells, causing tumor cell exit from the dormancy and formation of new tumor lesions. Higher serum concentrations of S100A8/A9 were associated with shorter time to recurrence in patients with lung cancer after complete tumor resection. Targeting of S100A8/A9 or β2-adrenergic receptors abrogated stress-induced reactivation of dormant tumor cells. These observations demonstrate a mechanism linking stress and specific neutrophil activation with early recurrence in cancer.

Association of Diverse Staphylococcus aureus Populations with Pseudomonas aeruginosa Coinfection and Inflammation in Cystic Fibrosis Airway Infection

Staphylococcus aureus is one of the most common pathogens isolated from the airways of cystic fibrosis (CF) patients and often persists for extended periods. There is limited knowledge about the diversity of S. aureus in CF. We hypothesized that increased diversity of S. aureus would impact CF lung disease. Therefore, we conducted a 1-year observational prospective study with 14 patients with long-term S. aureus infection. From every sputum, 40 S. aureus isolates were chosen and characterized in terms of phenotypic appearance (size, hemolysis, mucoidy, and pigmentation), important virulence traits such as nuclease activity, biofilm formation, and molecular typing by spa sequence typing. Data about coinfection with Pseudomonas aeruginosa and clinical parameters such as lung function, exacerbation, and inflammatory markers in blood (C-reactive protein [CRP], interleukin 6 [IL-6], and S100A8/9 [calprotectin]) were collected. From 58 visits of 14 patients, 2,319 S. aureus isolates were distinguished into 32 phenotypes (PTs) and 50 spa types. The Simpson diversity index (SDI) was used to calculate the phenotypic and genotypic diversity, revealing a high diversity of PTs ranging from 0.19 to 0.87 among patients, while the diversity of spa types of isolates was less pronounced. The SDI of PTs was positively associated with P. aeruginosa coinfection and inflammatory parameters, with IL-6 being the most sensitive parameter. Also, coinfection with P. aeruginosa was associated with mucoid S. aureus and S. aureus with high nuclease activity. Our analyses showed that in CF patients with long-term S. aureus airway infection, a highly diverse and dynamic S. aureus population was present and associated with P. aeruginosa coinfection and inflammation. IMPORTANCE Staphylococcus aureus can persist for extended periods in the airways of people with cystic fibrosis (CF) in spite of antibiotic therapy and high numbers of neutrophils, which fail to eradicate this pathogen. Therefore, S. aureus needs to adapt to this hostile niche. There is only limited knowledge about the diversity of S. aureus in respiratory specimens. We conducted a 1-year prospective study with 14 patients with long-term S. aureus infection and investigated 40 S. aureus isolates from every sputum in terms of phenotypic appearance, nuclease activity, biofilm formation, and molecular typing. Data about coinfection with Pseudomonas aeruginosa and clinical parameters such as lung function, exacerbation, and inflammatory markers in blood were collected. Thirty-two phenotypes (PTs) and 50 spa types were distinguished. Our analyses revealed that in CF patients with long-term S. aureus airway infection, a highly diverse and dynamic S. aureus population was associated with P. aeruginosa coinfection and inflammation.

Impact of Exercise Intensity on Calprotectin Levels in Healthy Volunteers and Patients with Inflammatory Rheumatic Diseases

Exercise influences inflammatory response and immune system performance. The regular practice of a moderate activity positively regulates immunity and the inflammatory process, while intensive training depresses it and enhances inflammatory marker secretion. Calprotectin is involved in the inflammatory process, promoting neutrophil recruitment, cell degranulation, and inflammatory mediators. Furthermore, calprotectin has been associated with various inflammatory diseases, including inflammatory rheumatic diseases. The present review explores the effect of exercise on calprotectin levels in both healthy and inflammatory rheumatic conditions. Data show that the intensity duration and the type of exercise modulate calprotectin levels and participant inflammatory status. The exact role of calprotectin in the exercise response is yet unknown. Calprotectin could constitute an interesting biomarker for monitoring both the effect of exercise on the inflammatory process in healthy volunteers and the efficiency of exercise treatment programs in a patient with inflammatory rheumatic disease.

Calprotectin in Lung Diseases

Calprotectin (CLP) is a heterodimer formed by two S-100 calcium-binding cytosolic proteins, S100A8 and S100A9. It is a multifunctional protein expressed mainly by neutrophils and released extracellularly by activated or damaged cells mediating a broad range of physiological and pathological responses. It has been more than 20 years since the implication of S100A8/A9 in the inflammatory process was shown; however, the evaluation of its role in the pathogenesis of respiratory diseases or its usefulness as a biomarker for the appropriate diagnosis and prognosis of lung diseases have only gained attention in recent years. This review aimed to provide current knowledge regarding the potential role of CLP in the pathophysiology of lung diseases and describe how this knowledge is, up until now, translated into daily clinical practice. CLP is involved in numerous cellular processes in lung health and disease. In addition to its anti-microbial functions, CLP also serves as a molecule with pro- and anti-tumor properties related to cell survival and growth, angiogenesis, DNA damage response, and the remodeling of the extracellular matrix. The findings of this review potentially introduce CLP in daily clinical practice within the spectrum of respiratory diseases.

MRP8/14 and neutrophil elastase for predicting treatment response and occurrence of flare in patients with juvenile idiopathic arthritis

Objective

To study two neutrophil activation markers, myeloid-related protein (MRP) 8/14 and neutrophil elastase (NE), for their ability to predict treatment response and flare in patients with JIA.

Methods

Using samples from two cohorts (I and II), we determined MRP8/14 and NE levels of 32 (I) and 81 (II) patients with new-onset, DMARD-naïve arthritis and compared patients who responded to treatment (defined as fulfilling ≥ adjusted ACRpedi50 response and/or inactive disease) with non-responders (defined as fulfilling < adjusted ACRpedi50 response and/or active disease) at 6 and 12 months. Secondly, we compared biomarker levels of 54 (I) and 34 (II) patients with clinically inactive disease who did or did not suffer from a flare of arthritis after 6 or 12 months. Receiver operating characteristic analyses were carried out to study the predictive value of MRP8/14 and NE for treatment response and flare.

Results

For both cohorts, baseline MRP8/14 and NE levels for patients who did or did not respond to treatment were not different. Also, MRP8/14 and NE levels were not different in patients who did or did not flare. Receiver operating characteristic analysis of MRP8/14 and NE demonstrated areas under the curve <0.7 in both cohorts.

Conclusion

In our cohorts, MRP8/14 and NE could not predict treatment response. Also, when patients had inactive disease, neither marker could predict flares.

S100A8/A9 in Myocardial Infarction: A Promising Biomarker and Therapeutic Target

Myocardial infarction (MI), the main cause of cardiovascular-related deaths worldwide, has long been a hot topic because of its threat to public health. S100A8/A9 has recently attracted an increasing amount of interest as a crucial alarmin that regulates the pathogenesis of cardiovascular disease after its release from myeloid cells. However, the role of S100A8/A9 in the etiology of MI is not well understood. Here, we elaborate on the critical roles and potential mechanisms of S100A8/A9 driving the pathogenesis of MI. First, cellular source of S100A8/A9 in infarcted heart is discussed. Then we highlight the effect of S100A8/A9 heterodimer in the early inflammatory period and the late reparative period of MI as well as myocardial ischemia/reperfusion (I/R) injury. Moreover, the predictive value of S100A8/A9 for the risk of recurrence of cardiovascular events is elucidated. Therefore, this review focuses on the molecular mechanisms of S100A8/A9 in MI pathogenesis to provide a promising biomarker and therapeutic target for MI.

Proinflammatory S100A9 Regulates Differentiation and Aggregation of Neural Stem Cells

Inflammation is the primary pathological feature of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease. Proinflammatory molecules (e.g., S100A9) play important roles during the progression of the diseases by regulating behavior and fate of multiple cell types in the nervous system. Our earlier studies reveal that S100A9 is toxic to neurons, and its interaction with Aβ peptides leads to the formation of large nontoxic amyloidogenic aggregates, suggesting a protective role of coaggregation with Aβ amyloids. We herein demonstrate that S100A9 interacts with neural stem cells (NSCs) and causes NSC differentiation. In the brain of transgenic AD mouse models, we found large quantities of proinflammatory S100A9, which colocalizes with the differentiated NSCs. NSC sphere formation, which is a representative character of NSC stemness, is also substantially inhibited by S100A9. These results suggest that S100A9 is a representative marker for the inflammatory conditions in AD, and it promotes NSC differentiation. Intriguingly, in contrast to the death of both stem and differentiated NSCs caused by high S100A9 doses, S100A9 at a moderate concentration is toxic only to the early differentiated NSCs but not the stem cells. We therefore postulate that, at the early stage of AD, the expression of S100A9 leads to NSC differentiation, which remedies the neuron damage. The application of drugs, which help maintain NSC stemness (e.g., the platelet-derived growth factor, PDGF), may help overcome the acute inflammatory conditions and improve the efficacy of NSC transplantation therapy.

Role of Innate Immune Receptor TLR4 and its endogenous ligands in epileptogenesis

Understanding the interplay between the innate immune system, neuroinflammation, and epilepsy might offer a novel perspective in the quest of exploring new treatment strategies. Due to the complex pathology underlying epileptogenesis, no disease-modifying treatment is currently available that might prevent epilepsy after a plausible epileptogenic insult despite the advances in pre-clinical and clinical research. Neuroinflammation underlies the etiopathogenesis of epilepsy and convulsive disorders with Toll-like receptor (TLR) signal transduction being highly involved. Among TLR family members, TLR4 is an innate immune system receptor and lipopolysaccharide (LPS) sensor that has been reported to contribute to epileptogenesis by regulating neuronal excitability. Herein, we discuss available evidence on the role of TLR4 and its endogenous ligands, the high mobility group box 1 (HMGB1) protein, the heat shock proteins (HSPs) and the myeloid related protein 8 (MRP8), in epileptogenesis and post-traumatic epilepsy (PTE). Moreover, we provide an account of the promising findings of TLR4 modulation/inhibition in experimental animal models with therapeutic impact on seizures.

Serum calprotectin: a promising biomarker in rheumatoid arthritis and axial spondyloarthritis

Background

Calprotectin (S100A8/S100A9 protein) is known as a damage-associated molecular pattern (DAMP) protein and reflects mainly neutrophil activation. Serum calprotectin levels might be a good alternative to acute-phase protein as a biomarker in inflammatory rheumatic diseases. The aim of this study is to investigate the association of serum calprotectin with disease activity and severity in rheumatoid arthritis (RA), axial spondyloarthritis (axSpA), and psoriatic arthritis (PsA).

Methods

Serum calprotectin was measured in patients with RA, axSpA, and PsA from the prospective Swiss Clinical Quality Management (SCQM) registry. Asymptomatic first-degree relatives of RA patients were used as healthy controls (HC). Outcomes included swollen joint count (SJC), Disease Activity Score (DAS), Health Assessment questionnaire (HAQ), joint radiographs, and ultrasound power Doppler (USPD) score for RA; Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Ankylosing Spondylitis Disease Activity Score (ASDAS) and coxitis for axSpA; and SJC and Disease Activity Index for PSoriatic Arthritis (DAPSA) for PsA. Comparison of outcomes by calprotectin quartile levels was performed using Kruskal-Wallis tests for continuous outcomes or trend tests for categorical outcomes.

Results

A total of 1729 subjects [RA = 969, axSpA = 451, PsA = 237, and HC = 72] were included. Median levels of serum calprotectin were higher in each disease group compared to HC (p < 0.01). In RA patients, all clinical outcomes were statistically different between quartiles of serum calprotectin, indicating an association between calprotectin levels and higher disease activity (SJC, DAS, and USPD scores) and severity (joint radiographs and HAQ). In axSpA, an association between calprotectin levels and ASDAS score (p < 0.01) and prevalence of coxitis (p = 0.02) was observed. For PsA patients, SJC and DAPSA did not differ across calprotectin quartiles.

Conclusions

This large study supports the association of serum calprotectin levels with disease activity in both RA and axSpA, but not in PsA.

S100-Alarmins Are Essential Pilots of Postnatal Innate Immune Adaptation

The restricted capacity of newborn infants to mount inflammatory responses toward microbial challenges has traditionally been linked to the high risk of septic diseases during the neonatal period. In recent years, substantial evidence has been provided that this characteristic of the neonatal immune system is actually a meaningful physiologic state that is based on specific transiently active cellular and molecular mechanisms and required for a favorable course of postnatal immune adaptation. The identification of physiologically high amounts of S100-alarmins in neonates has been one of the crucial pieces in the puzzle that contributed to the change of concept. In this context, innate immune immaturity could be redefined and assigned to the epigenetic silence of adult-like cell-autonomous regulation at the beginning of life. S100-alarmins represent an alternative age-specific mechanism of immune regulation that protects neonates from hyperinflammatory immune responses. Here, we summarize how infants are provided with S100-alarmins and why these allow an uneventful clash between the innate immune system and the extrauterine world. The mode of action of S100-alarmins is highlighted including their tuning functions at multiple levels for establishing a state of homeostasis with the environment in the newborn individual.

Elevation of inflammatory S100A8/S100A9 complexes in intracranial aneurysms

BACKGROUND

Inflammation-related factors might give further insight into the pathophysiology of vessel wall inflammation and intracranial aneurysm (IA) rupture. One of these factors is the protein complex S100A8/A9, which is released by neutrophils, monocytes, and activated macrophages and is known for its role in cardiovascular disease.

OBJECTIVE

To determine if venous S100A8/A9 levels in patients with a ruptured IA (rIA) or unruptured IA (uIA) are elevated compared with a control group. Second, to assess differences between venous and intra-aneurysmal S100A8/A9 levels of rIA and uIA patients.

METHODS

A prospective case study was performed between June 2016 and May 2017 in patients harboring a ruptured or unruptured saccular IA. Primary outcome measures were individual S100A8/A9 serum concentrations as measured in venous and intra-aneurysmal blood samples during endovascular treatment. Venous serum S100A8/A9 concentrations from a healthy control group served as a reference.

RESULTS

We included 16 patients with either a rIA or uIA and 47 healthy controls. Venous S100A8/A9 concentrations were higher in aneurysm patients (rIA and uIA) than those of healthy controls (P≤0.001). S100A8/A9 concentrations were higher in intra-aneurysmal samples than in venous samples of rIA patients (P=0.011). This difference was not found in uIA patients (P=0.054). Intra-aneurysmal S100A8/A9 levels were higher in rIAs than in uIAs (P=0.04).

CONCLUSIONS

Venous S100A8/A9 levels are elevated in patients with both rIAs and uIAs compared with healthy controls and likely represents aneurysm wall inflammation. S100A8/A9 causes macrophage-induced inflammation and degeneration of the vessel wall which might explain higher intra-aneurysmal S100A8/A9 levels found in rIAs than in uIAs.

Molecular profile of the rat peri-infarct region four days after stroke: Study with MANF

The peri-infarct region after ischemic stroke is the anatomical location for many of the endogenous recovery processes; however, -the molecular events in the peri-infarct region remain poorly characterized. In this study, we examine the molecular profile of the peri-infarct region on post-stroke day four, a time when reparative processes are ongoing. We used a multiomics approach, involving RNA sequencing, and mass spectrometry-based proteomics and metabolomics to characterize molecular changes in the peri-infarct region. We also took advantage of our previously developed method to express transgenes in the peri-infarct region where self-complementary adeno-associated virus (AAV) vectors were injected into the brain parenchyma on post-stroke day 2. We have previously used this method to show that mesencephalic astrocyte-derived neurotrophic factor (MANF) enhances functional recovery from stroke and recruits phagocytic cells to the peri-infarct region. Here, we first analyzed the effects of stroke to the peri-infarct region on post-stroke day 4 in comparison to sham-operated animals, finding that strokeinduced changes in 3345 transcripts, 341 proteins, and 88 metabolites. We found that after stroke, genes related to inflammation, proliferation, apoptosis, and regeneration were upregulated, whereas genes encoding neuroactive ligand receptors and calcium-binding proteins were downregulated. In proteomics, we detected upregulation of proteins related to protein synthesis and downregulation of neuronal proteins. Metabolomic studies indicated that in after stroke tissue there is an increase in saccharides, sugar phosphates, ceramides and free fatty acids and a decrease of adenine, hypoxantine, adenosine and guanosine. We then compared the effects of post-stroke delivery of AAV1-MANF to AAV1-eGFP (enhanced green fluorescent protein). MANF administration increased the expression of 77 genes, most of which were related to immune response. In proteomics, MANF administration reduced S100A8 and S100A9 protein levels. In metabolomics, no significant differences between MANF and eGFP treatment were detected, but relative to sham surgery group, most of the changes in lipids were significant in the AAV-eGFP group only. This work describes the molecular profile of the peri-infarct region during recovery from ischemic stroke, and establishes a resource for further stroke studies. These results provide further support for parenchymal MANF as a modulator of phagocytic function.

Phenotype of Innate Immune Cells in Uveitis Associated with Axial Spondyloarthritis- and Juvenile Idiopathic Arthritis-associated Uveitis

Purpose: To analyze circulating immune cells in patients with anterior uveitis (AU) associated to axial spondyloarthritis (SpA), or juvenile idiopathic arthritis (JIA).Methods: Venous blood samples were collected from healthy controls (n = 16), and either SpA (n = 19) or JIA (n = 23) patients with associated anterior uveitis (AU) during active flare, or after ≥3 months of inactivity. Frequencies of CD56⁺, MHC-I⁺, and S100A9⁺ monocytes, CCR7⁺ dendritic cells, CD56^+dim natural killer (NK) cells and CD3⁺CD56^bright T-cells were analyzed via flow cytometry. Serum S100A8/A9 levels were determined via ELISA.Results: SpA patients showed a reduced frequency of CD56^+dim NK cells during uveitis activity, a constitutively activated monocyte phenotype, and elevated S100A8/A9 serum levels. In contrast, JIAU patients showed elevated frequencies of CD56⁺ monocytes and CCR7⁺ DC.Conclusion: Phenotype of peripheral immune cells differ between patients, probably contributing to different courses of acute onset AU in SpA and insidious onset AU in JIAU patients.Abbreviations: AU: anterior uveitis, AR: arthritis, JIA: juvenile idiopathic arthritis, SpA: axial spondyloarthritis.

S100A8/S100A9 deficiency increases neutrophil activation and protective immune responses against invading infective L3 larvae of the filarial nematode Litomosoides sigmodontis

Neutrophils are essentially involved in protective immune responses against invading infective larvae of filarial nematodes. The present study investigated the impact of S100A8/S100A9 on protective immune responses against the rodent filarial nematode Litomosoides sigmodontis. S100A9 forms with S100A8 the heterodimer calprotectin, which is expressed by circulating neutrophils and monocytes and mitigates or amplifies tissue damage as well as inflammation depending on the immune environment. Mice deficient for S100A8/A9 had a significantly reduced worm burden in comparison to wildtype (WT) animals 12 days after infection (dpi) with infective L3 larvae, either by the vector or subcutaneous inoculation, the latter suggesting that circumventing natural immune responses within the epidermis and dermis do not alter the phenotype. Nevertheless, upon intradermal injection of L3 larvae, increased total numbers of neutrophils, eosinophils and macrophages were observed within the skin of S100A8/A9-/- mice. Furthermore, upon infection the bronchoalveolar and thoracic cavity lavage of S100A8/A9-/- mice showed increased concentrations of CXCL-1, CXCL-2, CXCL-5, as well as elastase in comparison to the WT controls. Neutrophils from S100A8/A9-/- mice exhibited an increased in vitro activation and reduced L3 larval motility more effectively in vitro compared to WT neutrophils. The depletion of neutrophils from S100A8/A9-/- mice prior to L. sigmodontis infection until 5dpi abrogated the protective effect and led to an increased worm burden, indicating that neutrophils mediate enhanced protective immune responses against invading L3 larvae in S100A8/A9-/- mice. Interestingly, complete circumvention of protective immune responses in the skin and the lymphatics by intravenous injection of L3 larvae reversed the phenotype and resulted in an increased worm burden in S100A8/A9-/- mice. In summary, our results reveal that lack of S100A8/S100A9 triggers L3-induced inflammatory responses, increasing chemokine levels, granulocyte recruitment as well as neutrophil activation and therefore impairs larval migration and susceptibility for filarial infection.

Role of S100 proteins in health and disease

The S100 family of proteins contains 25 known members that share a high degree of sequence and structural similarity. However, only a limited number of family members have been characterized in depth, and the roles of other members are likely undervalued. Their importance should not be underestimated however, as S100 family members function to regulate a diverse array of cellular processes including proliferation, differentiation, inflammation, migration and/or invasion, apoptosis, Ca²⁺ homeostasis, and energy metabolism. Here we detail S100 target protein interactions that underpin the mechanistic basis to their function, and discuss potential intervention strategies targeting S100 proteins in both preclinical and clinical situations.

Importance of superoxide dismutases A and M for protection of Staphylococcus aureus in the oxidative stressful environment of cystic fibrosis airways

Staphylococcus aureus is one of the earliest pathogens that persists the airways of cystic fibrosis (CF) patients and contributes to increased inflammation and decreased lung function. In contrast to other staphylococci, S. aureus possesses two superoxide dismutases (SODs), SodA and SodM, with SodM being unique to S. aureus. Both SODs arm S. aureus for its fight against oxidative stress, a by-product of inflammatory reactions. Despite complex investigations, it is still unclear if both enzymes are crucial for the special pathogenicity of S. aureus. To investigate the role of both SODs during staphylococcal persistence in CF airways, we analysed survival and gene expression of S. aureus CF isolates and laboratory strains in different CF-related in vitro and ex vivo settings. Bacteria located in inflammatory and oxidised CF sputum transcribed high levels of sodA and sodM. Especially expression values of sodM were remarkably higher in CF sputum than in bacterial in vitro cultures. Interestingly, also S. aureus located in airway epithelial cells expressed elevated transcript numbers of both SODs, indicating that S. aureus is exposed to oxidative stress at various sites within CF airways. Both enzymes promoted survival of S. aureus during polymorphonuclear leukocyte killing and seem to act compensatory, thereby giving evidence that the interwoven interaction of SodA and SodM contributes to S. aureus virulence and facilitates S. aureus persistence within CF airways.

Pathological roles of MRP14 in anemia and splenomegaly during experimental visceral leishmaniasis

Myeloid-related protein 14 (MRP14) belongs to the S100 calcium-binding protein family and is expressed in neutrophils and inflammatory macrophages. Increase in the number of MRP14+ cells or serum level of MRP14 is associated with various diseases such as autoimmune diseases and infectious diseases, suggesting the involvement of the molecule in pathogenesis of those diseases. In this study, to examine the pathological involvement of MRP14 during cutaneous and visceral leishmaniasis, wild-type (WT) and MRP14 knockout (MRP14KO) mice were infected with Leishmania major and L. donovani. Increase in the number of MRP14+ cells at the infection sites in wild-type mice was commonly found in the skin during L. major infection as well as the spleen and liver during L. donovani infection. In contrast, the influence of MRP14 to the pathology seemed different between the two infections. MRP14 depletion exacerbated the lesion development and ulcer formation in L. major infection. On the other hand, the depletion improved anemia and splenomegaly but not hepatomegaly at 24 weeks of L. donovani infection. These results suggest that, distinct from its protective role in CL, MRP14 is involved in exacerbation of some symptoms during VL.

Comparative proteomes change and possible role in different pathways of microRNA-21a-5p in a mouse model of spinal cord injury

Our previous study found that microRNA-21a-5p (miR-21a-5p) knockdown could improve the recovery of motor function after spinal cord injury in a mouse model, but the precise molecular mechanism remains poorly understood. In this study, a modified Allen's weight drop was used to establish a mouse model of spinal cord injury. A proteomics approach was used to understand the role of differential protein expression with miR-21a-5p knockdown, using a mouse model of spinal cord injury without gene knockout as a negative control group. We found that after introducing miR-21a-5p knockdown, proteins that played an essential role in the regulation of inflammatory processes, cell protection against oxidative stress, cell redox homeostasis, and cell maintenance were upregulated compared with the negative control group. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis identified enriched pathways in both groups, such as the oxidative phosphorylation pathway, which is relevant to Parkinson's disease, Huntington's disease, Alzheimer's disease, and cardiac muscle contraction. We also found that miR-21a-5p could be a potential biomarker for amyotrophic lateral sclerosis, as miR-21a-5p becomes deregulated in this pathway. These results indicate successful detection of some important proteins that play potential roles in spinal cord injury. Elucidating the relationship between these proteins and the recovery of spinal cord injury will provide a reference for future research of spinal cord injury biomarkers. All experimental procedures and protocols were approved by the Experimental Animal Ethics Committee of Shandong University of China on March 5, 2014.

Biomarkers for the Discrimination of Acute Kawasaki Disease From Infections in Childhood

Background: Kawasaki disease (KD) is a vasculitis of early childhood mimicking several infectious diseases. Differentiation between KD and infectious diseases is essential as KD's most important complication-the development of coronary artery aneurysms (CAA)-can be largely avoided by timely treatment with intravenous immunoglobulins (IVIG). Currently, KD diagnosis is only based on clinical criteria. The aim of this study was to evaluate whether routine C-reactive protein (CRP) and additional inflammatory parameters myeloid-related protein 8/14 (MRP8/14 or S100A8/9) and human neutrophil-derived elastase (HNE) could distinguish KD from infectious diseases. Methods and Results: The cross-sectional study included KD patients and children with proven infections as well as febrile controls. Patients were recruited between July 2006 and December 2018 in Europe and USA. MRP8/14, CRP, and HNE were assessed for their discriminatory ability by multiple logistic regression analysis with backward selection and receiver operator characteristic (ROC) curves. In the discovery cohort, the combination of MRP8/14+CRP discriminated KD patients (n = 48) from patients with infection (n = 105), with area under the ROC curve (AUC) of 0.88. The HNE values did not improve discrimination. The first validation cohort confirmed the predictive value of MRP8/14+CRP to discriminate acute KD patients (n = 26) from those with infections (n = 150), with an AUC of 0.78. The second validation cohort of acute KD patients (n = 25) and febrile controls (n = 50) showed an AUC of 0.72, which improved to 0.84 when HNE was included. Conclusion: When used in combination, the plasma markers MRP8/14, CRP, and HNE may assist in the discrimination of KD from both proven and suspected infection.