Soluble ST2 and CD163 as Potential Biomarkers to Differentiate Primary Hemophagocytic Lymphohistiocytosis from Macrophage Activation Syndrome

Genetic and clinical characteristics of primary hemophagocytic lymphohistiocytosis in children

To analyze the genetic variation and prognosis of primary hemophagocytic lymphohistiocytosis (pHLH) in children and the clinical features of isolated central nervous system HLH (CNS-HLH). We retrospectively analyzed the clinical and genetic data of 480 HLH children admitted to our hospital from September 2017 to September 2022. There were 66 patients (13.75%) with pHLH, and the median age was 3.21 years (0.17-12.92 years). Variants in UNC13D (22/66, 33.33%), PRF1 (20/66, 30.30%) and XIAP (11/66, 16.67%) were the most common. More CNS involvement was observed in pHLH patients than in secondary hemophagocytic lymphohistiocytosis (sHLH) patients (50% vs. 25.3%, P = 0.001). Eight pHLH patients had isolated CNS-HLH at onset, which progressed to systemic HLH within 10-30 days to several years. Among them, five patients who underwent hematopoietic stem cell transplantation (HSCT) survived without CNS sequelae, and the three patients who did not undergo HSCT died of disease progression or recurrence. Determination of natural killer (NK) cell cytotoxicity and CD107a levels had low sensitivity and specificity in the diagnosis of pHLH, especially in patients with PRF1 and XIAP mutations. The 3-year overall survival (OS) was significantly lower in pHLH patients than in sHLH patients (74.5% ± 14.7% vs. 89.2% ± 3.53%, P = 0.021) and in patients with CNS involvement than in those without (53.8% ± 26.07% vs. 94.4% ± 10.58%, P = 0.012). There was a significant difference in OS among pHLH patients with different gene variants (P = 0.032); patients with PRF1 variants had poor 3-year OS, and patients with XIAP variants had good 3-year OS (50% ± 28.22% and 100%, respectively). pHLH patients with distinct variants have different prognoses. Isolated CNS-HLH patients are easily misdiagnosed, and HSCT may be beneficial for these patients. Determination of NK cell cytotoxicity and CD107a levels cannot precisely distinguish pHLH from sHLH.

Proteomic Analysis of Pediatric Hemophagocytic Lymphohistiocytosis: a Comparative Study with Healthy Controls, Sepsis, Critical Ill, and Active Epstein-Barr virus Infection to Identify Altered Pathways and Candidate Biomarkers

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome characterized by excessive activation of the immune system, along with uncontrolled proliferation of activated macrophages and lymphocytes. The clinical features of HLH often overlap with the clinical features of other severe inflammatory conditions such as sepsis, hindering accurate and timely diagnosis. In this study, we performed a data-independent acquisition mass spectrometry-based plasma proteomic analysis of 33 pediatric patients with HLH compared with four control groups: 39 healthy children, 43 children with sepsis, 39 children hospitalized in the pediatric intensive care unit without confirmed infections, and 21 children with acute Epstein-Barr virus infection. Proteomic comparisons between the HLH group and each of the control groups showed that HLH was characterized by alterations in complement and coagulation cascades, neutrophil extracellular trap formation, and platelet activation pathways. We identified eight differentially expressed proteins in patients with HLH, including plastin-2 (LCP1), vascular cell adhesion protein 1, fibrinogen beta chain, fibrinogen gamma chain, serum amyloid A-4 protein, extracellular matrix protein 1, apolipoprotein A-I, and albumin. LCP1 emerged as a candidate diagnostic marker for HLH with an area under the curve (AUC) of 0.97 in the original cohort and an AUC of 0.90 (sensitivity = 0.83 and specificity = 1.0) in the validation cohort. Complement C1q subcomponent subunit B was associated with disease severity in patients with HLH. Based on comparisons with multiple control groups, this study provides a proteomic profile and candidate biomarkers of HLH, offering researchers novel information to improve the understanding of this condition.

Up-regulated serum levels of soluble CD25 and soluble CD163 in pediatric patients with SARS-CoV-2

Similar to hemophagocytic lymphohistiocytosis (HLH), some patients with SARS-CoV-2 have cytokine storm. Serum soluble interleukin-2 receptor (sCD25) and soluble CD163 (sCD163) are potential diagnostic biomarkers for HLH that help in guiding its treatment. This study was the first to investigate serum sCD25 and sCD163 levels in SARS-CoV-2. Serum sCD25 and sCD163 were measured by ELISA in 29 patients with SARS-CoV-2, aged between 2 months and 16 years (13 had COVID-19 and 16 had multisystem inflammatory syndrome in children (MIS-C)), in comparison to 30 age- and sex-matched healthy control children and 10 patients with HLH. Levels of these markers were re-measured in 21 patients with SARS-CoV-2 who were followed up 3 months after recovery. Patients with SARS-CoV-2 had significantly higher serum sCD25 and sCD163 than healthy control children (P < 0.001). SARS-CoV-2 patients had significantly higher sCD25 than patients with HLH (P < 0.05). Serum sCD25 was a good differentiating marker between patients with SARS-CoV-2 and HLH. Although there was a significant decrease of serum sCD25 and sCD163 of the 21 SARS-CoV-2 patients who were followed up, these levels were still significantly higher than the healthy controls levels (P < 0.001).  Conclusion: Serum sCD25 and sCD163 levels were up-regulated in SARS-CoV-2 patients. Serum sCD25 was a good differentiating marker between SARS-CoV-2 and HLH. This initial report requires further studies, on large scales, to investigate the relationship between SARS-CoV-2 and both sCD25 and sCD163, including the disease severity and outcome. The therapeutic role of sCD25 and sCD163 antagonists should also be studied in SARS-CoV-2 patients. What is Known: • Similar to hemophagocytic lymphohistiocytosis (HLH), some patients with COVID-19 have cytokine storm due to excessive pro-inflammatory host response. • Serum soluble interleukin-2 receptor (sCD25) and soluble CD163 (sCD163) are potential diagnostic biomarkers for HLH. Monitoring of serum sCD25 and sCD163 levels can also help in guiding the treatment. What is New: • Serum sCD25 and sCD163 levels are up-regulated in patients with COVID-19, including patients presenting with multisystem inflammatory syndrome in children (MIS-C). • Serum sCD25 is a good differentiating marker between SARS-CoV-2 and HLH.

From Anti-SARS-CoV-2 Immune Response to the Cytokine Storm via Molecular Mimicry

The aim of this study was to investigate the role of molecular mimicry in the cytokine storms associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Human proteins endowed with anti-inflammatory activity were assembled and analyzed for peptide sharing with the SARS-CoV-2 spike glycoprotein (gp) using public databases. It was found that the SARS-CoV-2 spike gp shares numerous pentapeptides with anti-inflammatory proteins that, when altered, can lead to cytokine storms characterized by diverse disorders such as systemic multiorgan hyperinflammation, macrophage activation syndrome, ferritinemia, endothelial dysfunction, and acute respiratory syndrome. Immunologically, many shared peptides are part of experimentally validated epitopes and are also present in pathogens to which individuals may have been exposed following infections or vaccinal routes and of which the immune system has stored memory. Such an immunologic imprint might trigger powerful anamnestic secondary cross-reactive responses, thus explaining the raging of the cytokine storm that can occur following exposure to SARS-CoV-2. In conclusion, the results support molecular mimicry and the consequent cross-reactivity as a potential mechanism in SARS-CoV-2-induced cytokine storms, and highlight the role of immunological imprinting in determining high-affinity, high-avidity, autoimmune cross-reactions as a pathogenic sequela associated with anti-SARS-CoV-2 vaccines.

A novel anti-human IL-1R7 antibody reduces IL-18-mediated inflammatory signaling

Unchecked inflammation can result in severe diseases with high mortality, such as macrophage activation syndrome (MAS). MAS and associated cytokine storms have been observed in COVID-19 patients exhibiting systemic hyperinflammation. Interleukin-18 (IL-18), a proinflammatory cytokine belonging to the IL-1 family, is elevated in both MAS and COVID-19 patients, and its level is known to correlate with the severity of COVID-19 symptoms. IL-18 binds its specific receptor IL-1 receptor 5 (IL-1R5, also known as IL-18 receptor alpha chain), leading to the recruitment of the coreceptor, IL-1 receptor 7 (IL-1R7, also known as IL-18 receptor beta chain). This heterotrimeric complex then initiates downstream signaling, resulting in systemic and local inflammation. Here, we developed a novel humanized monoclonal anti-IL-1R7 antibody to specifically block the activity of IL-18 and its inflammatory signaling. We characterized the function of this antibody in human cell lines, in freshly obtained peripheral blood mononuclear cells (PBMCs) and in human whole blood cultures. We found that the anti-IL-1R7 antibody significantly suppressed IL-18-mediated NFκB activation, reduced IL-18-stimulated IFNγ and IL-6 production in human cell lines, and reduced IL-18-induced IFNγ, IL-6, and TNFα production in PBMCs. Moreover, the anti-IL-1R7 antibody significantly inhibited LPS- and Candida albicans–induced IFNγ production in PBMCs, as well as LPS-induced IFNγ production in whole blood cultures. Our data suggest that blocking IL-1R7 could represent a potential therapeutic strategy to specifically modulate IL-18 signaling and may warrant further investigation into its clinical potential for treating IL-18-mediated diseases, including MAS and COVID-19.

Do COVID-19 Infections Result in a Different Form of Secondary Hemophagocytic Lymphohistiocytosis

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in significant morbidity and mortality across the world, with no current effective treatments available. Recent studies suggest the possibility of a cytokine storm associated with severe COVID-19, similar to the biochemical profile seen in hemophagocytic lymphohistiocytosis (HLH), raising the question of possible benefits that could be derived from targeted immunosuppression in severe COVID-19 patients. We reviewed the literature regarding the diagnosis and features of HLH, particularly secondary HLH, and aimed to identify gaps in the literature to truly clarify the existence of a COVID-19 associated HLH. Diagnostic criteria such as HScore or HLH-2004 may have suboptimal performance in identifying COVID-19 HLH-like presentations, and criteria such as soluble CD163, NK cell activity, or other novel biomarkers may be more useful in identifying this entity.

Monitoring immunomodulation in patients with sepsis

Introduction: This review aims to summarize current progress of the last ten years in the development of biomarkers used for classifying the immune response of the septic host and for monitoring the efficacy of the applied adjunctive immunotherapy.Areas covered: An extensive search of the literature was performed. In this review the authors discuss available biomarkers of host immune response in sepsis toward two directions; immunosuppression and hyperinflammation. Ferritin, sCD163, sIL-2 ra, and IL-18 may help in the diagnosis of macrophage activation syndrome (MAS) complicating sepsis whereas lymphopenia, decreased HLA-DR expression on monocytes, overexpression of Programmed cell death protein-1 (PD-1)/Programmed death-ligand 1 (PD-L1) and IL-10 are indicators of sepsis-induced immunosuppression. Novel approaches in the classification of immune state in sepsis include Myeloid-Derived Suppressor Cells (MDSC) and specific endotypes, defined by gene expression and molecular techniques.Expert opinion: HLA-DR and ferritin are the most commonly used biomarkers to monitor immunomodulation in clinical practice whereas developing specific sepsis endotypes is the future target. New immunotherapy trials in sepsis need to incorporate biomarkers for a personalized treatment.

The role of interleukin-18 in the diagnosis and monitoring of hemophagocytic lymphohistiocytosis/macrophage activation syndrome - a systematic review

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening, hyperinflammatory disorder, characterized by multiorgan failure, fever and cytopenias. The diagnosis of HLH and its subtype Macrophage Activation Syndrome (MAS) remains a challenge. Interleukin 18 (IL-18) is emerging as a potential biomarker for HLH/MAS but is currently not a part of diagnostic criteria. This systematic review aimed to assess the potential role of IL-18 in the diagnosis and monitoring of HLH and MAS, and was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed and Embase were searched on 30 January 2020. Studies included all subtypes of HLH and a range of underlying disorders in both children and adults. A total of 14 studies were included. Generally, serum IL-18 was elevated in both primary and secondary HLH (> 1000 pg/ml) compared with other inflammatory conditions and with healthy individuals; thus, serum IL-18 may be able to discriminate between HLH and other inflammatory conditions. Significantly increased IL-18 (> 10 000 pg/ml) was also consistently described in MAS compared with other subtypes of HLH. The ability of IL-18 to distinguish MAS from systemic juvenile idiopathic arthritis (JIA) is less unambiguous, as IL-18 levels > 100 000 pg/ml were described in sJIA patients both with and without MAS. IL-18 may help to differentiate between HLH subtypes and other inflammatory conditions. As HLH and MAS are rare disorders, only few and relatively small studies exist on the subject. Larger, prospective multi-center studies are called for to assess the diagnostic precision of IL-18 for HLH and MAS.

Current treatment options and safety considerations when treating adult-onset Still's disease

INTRODUCTION

Adult onset Still disease (AOSD) is a rare systemic inflammatory condition. The clinical spectrum of this disease ranges from self-limiting forms with mild symptoms to life-threatening cases. Glucocorticoids and non-steroidal anti-inflammatory drugs (NSAIDs) represent the first line of therapy for AOSD, with add-on therapy with second-line drug reserved to steroid-dependent patients and in life-threatening cases. Currently, early treatment with conventional disease modifying anti-rheumatic drugs (DMARDs) and biologic agents blocking causal cytokines is advocated in patients with severe and recalcitrant clinical manifestations.

AREAS COVERED

This review analyzes the available controlled evidence and observational data regarding the efficacy and safety of conventional and biological pharmacological agents in the treatment of AOSD.

EXPERT OPINION

Non-steroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids are effective in controlling clinical manifestations in the majority of AOSD patients. Conventional DMARDs can be 20 effective in some severe and steroid-dependent cases of AOSD; however, anti-cytokine agents represent an effective and overall more suitable alternative in this specific subset of patients. IL-1 and IL-6 blockade are effective in treating systemic and articular inflammation of AOSD patients. IL-1 blockade also has an excellent safety profile and therefore represent the first choice of biologic treatment in this clinical scenario.

COVID-19 as part of the hyperferritinemic syndromes: the role of iron depletion therapy

SARS-CoV-2 infection is characterized by a protean clinical picture that can range from asymptomatic patients to life-threatening conditions. Severe COVID-19 patients often display a severe pulmonary involvement and develop neutrophilia, lymphopenia, and strikingly elevated levels of IL-6. There is an over-exuberant cytokine release with hyperferritinemia leading to the idea that COVID-19 is part of the hyperferritinemic syndrome spectrum. Indeed, very high levels of ferritin can occur in other diseases including hemophagocytic lymphohistiocytosis, macrophage activation syndrome, adult-onset Still's disease, catastrophic antiphospholipid syndrome and septic shock. Numerous studies have demonstrated the immunomodulatory effects of ferritin and its association with mortality and sustained inflammatory process. High levels of free iron are harmful in tissues, especially through the redox damage that can lead to fibrosis. Iron chelation represents a pillar in the treatment of iron overload. In addition, it was proven to have an anti-viral and anti-fibrotic activity. Herein, we analyse the pathogenic role of ferritin and iron during SARS-CoV-2 infection and propose iron depletion therapy as a novel therapeutic approach in the COVID-19 pandemic.

COVID-19 as part of the hyperferritinemic syndromes: the role of iron depletion therapy

SARS-CoV-2 infection is characterized by a protean clinical picture that can range from asymptomatic patients to life-threatening conditions. Severe COVID-19 patients often display a severe pulmonary involvement and develop neutrophilia, lymphopenia, and strikingly elevated levels of IL-6. There is an over-exuberant cytokine release with hyperferritinemia leading to the idea that COVID-19 is part of the hyperferritinemic syndrome spectrum. Indeed, very high levels of ferritin can occur in other diseases including hemophagocytic lymphohistiocytosis, macrophage activation syndrome, adult-onset Still's disease, catastrophic antiphospholipid syndrome and septic shock. Numerous studies have demonstrated the immunomodulatory effects of ferritin and its association with mortality and sustained inflammatory process. High levels of free iron are harmful in tissues, especially through the redox damage that can lead to fibrosis. Iron chelation represents a pillar in the treatment of iron overload. In addition, it was proven to have an anti-viral and anti-fibrotic activity. Herein, we analyse the pathogenic role of ferritin and iron during SARS-CoV-2 infection and propose iron depletion therapy as a novel therapeutic approach in the COVID-19 pandemic.