Involvement of innate and adaptive immunity in a murine model of coronary arteritis mimicking Kawasaki disease

B Cells at the Cross-Roads of Autoimmune Diseases and Auto-Inflammatory Syndromes

Whereas autoimmune diseases are mediated primarily by T and B cells, auto-inflammatory syndromes (AIFS) involve natural killer cells, macrophages, mast cells, dendritic cells, different granulocyte subsets and complement components. In contrast to autoimmune diseases, the immune response of patients with AIFS is not associated with a breakdown of immune tolerance to self-antigens. Focusing on B lymphocyte subsets, this article offers a fresh perspective on the multiple cross-talks between both branches of innate and adaptive immunity in mounting coordinated signals that lead to AIFS. By virtue of their potential to play a role in adaptive immunity and to exert innate-like functions, B cells can be involved in both promoting inflammation and mitigating auto-inflammation in disorders that include mevalonate kinase deficiency syndrome, Kawasaki syndrome, inflammatory bone disorders, Schnitzler syndrome, Neuro-Behçet's disease, and neuromyelitis optica spectrum disorder. Since there is a significant overlap between the pathogenic trajectories that culminate in autoimmune diseases, or AIFS, a more detailed understanding of their respective roles in the development of inflammation could lead to designing novel therapeutic avenues.

Intravenous Immunoglobulin Therapy Restores the Quantity and Phenotype of Circulating Dendritic Cells and CD4+ T Cells in Children With Acute Kawasaki Disease

Background

Intravenous immunoglobulin (IVIG) showed its therapeutic efficacy on Kawasaki disease (KD). However, the mechanisms by which it reduces systemic inflammation are not completely understood. Dendritic cells (DCs) and T cells play critical roles in the pathogenic processes of immune disorders. Assessing the quantity of DC subsets and T cells and identifying functional molecules present on these cells, which provide information about KD, in the peripheral blood may provide new insights into the mechanisms of immunoglobulin therapy.

Methods

In total, 54 patients with KD and 27 age-matched healthy controls (HCs) were included in this study. The number, percentage, and phenotype of DC subsets and CD4⁺ T cells in peripheral blood were analyzed through flow cytometry.

Results

Patients with KD exhibited fewer peripheral DC subsets and CD4⁺ T cells than HCs. Human leucocyte antigen-DR (HLA-DR) expression was reduced on CD1c⁺ myeloid DCs (CD1c⁺ mDCs), whereas that on plasmacytoid DCs (pDCs) did not change significantly. Both pDCs and CD1c⁺ mDCs displayed significantly reduced expression of co-stimulatory molecules, including CD40, CD86. pDCs and CD1c⁺ mDCs presented an immature or tolerant phenotype in acute stages of KD. Number of circulating pDC and CD1c⁺ mDC significantly inversely correlated with plasma interleukin-6 (IL-6) levels in KD patients pre-IVIG treatment. No significant differences were found concerning the DC subsets and CD4⁺ T cells in patients with KD with and without coronary artery lesions. Importantly, these altered quantity and phenotypes on DC subsets and CD4⁺ T cells were restored to a great extent post-IVIG treatment. T helper (Th) subsets including Th1 and Th2 among CD4⁺ T cells did not show alteration pre- and post-IVIG treatment, although the Th1-related cytokine IFN-γ level in plasma increased dramatically in patients with KD pre-IVIG treatment.

Conclusions

pDCs and CD1c⁺ mDCs presented an immature or tolerant phenotype in acute stages of KD, IVIG treatment restored the quantity and functional molecules of DCs and CD4⁺ T cells to distinct levels in vivo, indicating the involvement of DCs and CD4⁺ T cells in the inflammation in KD. The findings provide insights into the immunomodulatory actions of IVIG in KD.

Anakinra Treatment in Patients with Acute Kawasaki Disease with Coronary Artery Aneurysms: A Phase I/IIa Trial

OBJECTIVES

To determine the safety, pharmacokinetics, and immunomodulatory effects of 2-6 weeks of anakinra therapy in patients with acute Kawasaki disease with a coronary artery aneurysm (CAA).

STUDY DESIGN

We performed a Phase I/IIa dose-escalation study of anakinra (2-11 mg/kg/day) in 22 patients with acute Kawasaki disease with CAA. We measured interleukin (IL)-1RA concentrations after the first dose and trough levels up to study week 6. Markers of inflammation and coronary artery z-scores were assessed pretreatment and at 48 hours, 2 weeks, and 6 weeks after initiation of therapy.

RESULTS

Up to 6 weeks of anakinra (up to 11 mg/kg/day) was safe and well tolerated by the 22 participants (median age, 1.1 years), with no serious adverse events attributable to the study drug. All participants were treated with intravenous immunoglobulin (IVIG), and 20 also received infliximab (10 mg/kg) before initiation of anakinra. Serum levels of IL-6, IL-8, and tumor necrosis factor α decreased similarly in patients with Kawasaki disease treated with IVIG, infliximab, and anakinra compared with age- and sex-matched patients with Kawasaki disease treated only with IVIG and infliximab. Anakinra clearance increased with illness day at diagnosis. Simulations demonstrated that more frequent intravenous (IV) dosing may result in more sustained concentrations without significantly increasing the peak concentration compared with subcutaneous (SC) dosing.

CONCLUSIONS

Both IV and SC anakinra are safe in infants and children with acute Kawasaki disease and CAA. IV dosing every 8-12 hours during the acute hospitalization of patients with Kawasaki disease may result in a sustained concentration while avoiding frequent SC injections. The efficacy of a short course of IV therapy during hospitalization should be studied. TRIAL REGISTRATION CLINICALTRIALS.GOV: NCT02179853.

Profile of Urinary Cytokines in Kawasaki Disease: Non-Invasive Markers

This cohort study aimed to investigate urinary cytokines expression to help identify a less invasive method of cytokine detection for Kawasaki disease (KD). Patients with confirmed KD were recruited. Patients with fever or urinary tract infection (UTI) were enrolled as control groups. Urinary samples were collected before and 3 days after intravenous immunoglobulin (IVIG) treatment. The levels of cytokines were detected by MILLPLEX^® MAP human multiplex assay. All cytokines, i.e., epidermal growth factor (EGF), interferon (IFN)-γ, interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-9, IL-10, IL-13, IL-17A, IL-33, interferon-gamma-induced protein (IP)-10, macrophage inflammatory protein (MIP)-1β, tumor necrosis factor (TNF)-α, and vascular endothelial growth factor (VEGF) except monocyte chemoattractant protein (MCP)-1 were significantly higher in the KD group, compared with the fever-control (FC) group, whereas the expressions of IFN-γ, IL-1β, IL-6, IL-8, IL-17A, IL-33, MCP-1, MIP-1β, and TNF-α were significantly lower in the urine of KD patients, as compared with the UTI group. The expressions of EGF, IFN-γ, IL-8, IL-13, and IL-17A were higher in the urine of KD patients than in the FC group, whereas the level of IL-1β was lower in KD than in the UTI group after age adjustment by logistic regression. Levels of IL-6, IL-8, IL-13, IP-10, and MCP-1 were significantly higher in the pre-IVIG urine of KD patients than in the post-IVIG treatment group. Additionally, urine IL-4 and blood C-reactive protein were higher in the KD group with coronary artery lesion (CAL) than in the non-CAL group. Results of this study provide a new view of urinary cytokine expression in the disease progress of KD, which may help clinicians to predict and prevent morbidity early and non-invasively.

The up-to-date pathophysiology of Kawasaki disease

Kawasaki disease (KD) is an acute systemic vasculitis of an unknown aetiology. A small proportion of children exposed to severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) or infected by Yersinia reproducibly develop principal symptoms of KD in various ethnic areas, but not in all studies. These microbes provoke a rapid cell‐damaging process, called ‘pyroptosis’, which is characterised by a subsequent release of proinflammatory cellular components from damaged endothelial and innate immune cells. In agreement with these molecular events, patients with KD show elevated levels of damage‐associated molecular patterns derived from cell death. In addition, an overwhelming amount of oxidative stress‐associated molecules, including oxidised phospholipids or low‐density lipoproteins, are generated as by‐products of inflammation during the acute phase of the disease. These molecules induce abnormalities in the acquired immune system and activate innate immune and vascular cells to produce a range of proinflammatory molecules such as cytokines, chemokines, proteases and reactive oxygen species. These responses further recruit immune cells to the arterial wall, wherein inflammation and oxidative stress closely interact and mutually amplify each other. The inflammasome, a key component of the innate immune system, plays an essential role in the development of vasculitis in KD. Thus, innate immune memory, or ‘trained immunity’, may promote vasculitis in KD. Hence, this review will be helpful in understanding the pathophysiologic pathways leading to the development of principal KD symptoms and coronary artery lesions in patients with KD, as well as in subsets of patients with SARS‐CoV‐2 and Yersinia infections.

KCa3.1 Inhibition of Macrophages Suppresses Inflammatory Response Leading to Endothelial Damage in a Cell Model of Kawasaki Disease

Purpose

Macrophages-mediated inflammation is linked with endothelial damage of Kawasaki disease (KD). KCa3.1, a calcium-activated potassium channel, modulates inflammation of macrophages. However, little is known about the role of KCa3.1 in inflammation by macrophages involved in KD. Hence, this study is aimed to explore the potential role of KCa3.1 in regulating inflammatory response by macrophages and subsequent vascular injury in an in vitro model of KD.

Methods

RAW264.7 cells were stimulated with Lactobacillus casei cell wall extract (LCWE) with or without TRAM-34 or PDTC or AG490. Subsequently, mouse coronary artery endothelial cells (MCAECs) were incubated with RAW264.7 cells-conditioned medium to mimic local inflammatory lesions in KD. CCKi8 assay was used to evaluate cell viability. The mRNA levels of inflammatory mediators were detected by qRT-PCR. Expressions of KCa3.1, MCAECs injury-associated molecules, proteins involved in signal pathways of nuclear factor-κB (NF-κB), signal transducers and activators of transcription (STAT) 3 and p38 were evaluated by Western blot.

Results

Our study showed that LCWE increased KCa3.1 protein level in RAW264.7 macrophages and KCa3.1 inhibition by TRAM-34 notably suppressed the expression of pro-inflammatory molecules in LCWE-treated macrophages via blocking the activation of NF-κB and STAT3 pathways. Besides, the inflammation and damage of MCAECs were attenuated in the TRAM-34-treated group compared with the KD model group. This vascular protective role was dependent on the down-regulation of NF-κB and STAT3 signal pathways, which was confirmed by using inhibitors of NF-κB and STAT3.

Conclusion

This study demonstrates that KCa3.1 blockade of macrophages suppresses inflammatory reaction leading to mouse coronary artery endothelial cell injury in a cell model of KD by hampering the activation of NF-κB and STAT3 signaling pathway. These findings imply that KCa3.1 may be a potential therapeutic target for KD.

Characterization of the T Cell Response to Lactobacillus casei Cell Wall Extract in Children With Kawasaki Disease and Its Potential Role in Vascular Inflammation

KD is an acute febrile illness and systemic vasculitis of unknown etiology among young children, which can cause coronary artery abnormalities and aneurysms (CAA) and is the leading cause of acquired heart disease among children in the US. Lactobacillus casei cell wall extract (LCWE) induces in mice a vasculitis following intraperitoneal injection defined by the activation of macrophages, dendritic cells and CD8+ cytotoxic T cells leading to aortitis, coronary arteritis, aneurysms and myocarditis that strongly mimic the immunopathology and the cardiac lesions observed in children with Kawasaki disease (KD). To address a potential pathogenic role of LCWE-specific T cells in human vascular inflammation, we studied the activation of circulating CD4+ and CD8+ T cells ex vivo in response to LCWE in 3 cohorts: (1) KD children 2-3 weeks after fever onset, (2) age-similar healthy children controls, (3) healthy adult controls. In all subjects studied, pro-inflammatory CD4+ and CD8+T cells responded to LCWE with no significant differences. Peripherally-induced regulatory T cells (iTreg) also responded to LCWE and potentially reverted to Th17, as suggested by the detection of IL-17 in culture supernatants. Central memory T cells were also detectable and were more abundant in adults. The potential homing to the vessels of LCWE-specific T cells was suggested by the expression of CCR6 and CD31. In conclusion, a non-pathogenic, LCWE-specific T cell repertoire could lead to KD depending upon priming conditions, genetic factors and immune activation by other antigens.

Antibodies and Immunity During Kawasaki Disease

The cause of Kawasaki disease (KD), the leading cause of acquired heart disease in children, is currently unknown. Epidemiology studies support that an infectious disease is involved in at least starting the inflammatory cascade set off during KD. Clues from epidemiology support that humoral immunity can have a protective effect. However, the role of the immune system, particularly of B cells and antibodies, in pathogenesis of KD is still unclear. Intravenous immunoglobulin (IVIG) and other therapies targeted at modulating inflammation can prevent development of coronary aneurysms. A number of autoantibody responses have been reported in children with KD and antibodies have been generated from aneurysmal plasma cell infiltrates. Recent reports show that children with KD have similar plasmablast responses as other children with infectious diseases, further supporting an infectious starting point. As ongoing studies are attempting to identify the etiology of KD through study of antibody responses, we sought to review the role of humoral immunity in KD pathogenesis, treatment, and recovery.

Kawasaki disease: pathophysiology and insights from mouse models

Kawasaki disease is an acute febrile illness and systemic vasculitis of unknown aetiology that predominantly afflicts young children, causes coronary artery aneurysms and can result in long-term cardiovascular sequelae. Kawasaki disease is the leading cause of acquired heart disease among children in the USA. Coronary artery aneurysms develop in some untreated children with Kawasaki disease, leading to ischaemic heart disease and myocardial infarction. Although intravenous immunoglobulin (IVIG) treatment reduces the risk of development of coronary artery aneurysms, some children have IVIG-resistant Kawasaki disease and are at increased risk of developing coronary artery damage. In addition, the lack of specific diagnostic tests and biomarkers for Kawasaki disease make early diagnosis and treatment challenging. The use of experimental mouse models of Kawasaki disease vasculitis has considerably improved our understanding of the pathology of the disease and helped characterize the cellular and molecular immune mechanisms contributing to cardiovascular complications, in turn leading to the development of innovative therapeutic approaches. Here, we outline the pathophysiology of Kawasaki disease and summarize and discuss the progress gained from experimental mouse models and their potential therapeutic translation to human disease.

This Review outlines the pathophysiology of Kawasaki disease and discusses the progress gained from experimental mouse models and their potential therapeutic translation to human disease.

Kawasaki disease is a childhood systemic vasculitis leading to the development of coronary artery aneurysms; it is the leading cause of acquired heart disease in children in developed countries.

The cause of Kawasaki disease is unknown, although it is suspected to be triggered by an unidentified infectious pathogen in genetically predisposed children.

Kawasaki disease might not be a normal immune response to an unusual environmental stimulus, but rather a genetically determined unusual and uncontrolled immune response to a common stimulus.

Although the aetiological agent in humans is unknown, mouse models of Kawasaki disease vasculitis demonstrate similar pathological features and have substantially accelerated discoveries in the field.

Genetic and transcriptomic analysis of blood samples from patients with Kawasaki disease and experimental evidence generated using mouse models have demonstrated the critical role of IL-1β in the pathogenesis of this disease and the therapeutic potential of targeting this pathway (currently under investigation in clinical trials).

A Comprehensive Update on Kawasaki Disease Vasculitis and Myocarditis

PURPOSE OF THE REVIEW

Kawasaki disease (KD) is a childhood systemic vasculitis of unknown etiology that causes coronary artery aneurysms (CAA), and if left undiagnosed can result in long-term cardiovascular complications and adult cardiac disease. Up to 20% of KD children fail to respond to IVIG, the mainstay of therapy, highlighting the need for novel therapeutic strategies. Here we review the latest findings in the field regarding specific etiology, genetic associations, and advancements in treatment strategies to prevent coronary aneurysms.

RECENT FINDINGS

Recent discoveries using the Lactobacillus casei cell wall extract (LCWE)-induced KD vasculitis mouse model have accelerated the study of KD pathophysiology and have advanced treatment strategies including clinical trials for IL-1R antagonist, Anakinra. KD remains an elusive pediatric vasculitis syndrome and is the leading cause of acquired heart disease among children in the USA and developed countries. Advancements in combination treatment for refractory KD with further understanding of novel genetic risk factors serve as a solid foundation for future research endeavors in the field.

Kawasaki disease in infants less than one year of age: an Italian cohort from a single center

Background and aims

Few data are currently available for Kawasaki disease (KD) below 12 months especially in Caucasians. This study aims to analyze clinical and laboratory features of KD among an Italian cohort of infants.

Methods

A retrospective chart review of KD children aged less than 1 year at time of disease onset between January 2008–December 2017 was performed. Clinical data, laboratory parameters, instrumental findings, treatment and outcome were collected in a customized database.

Results

Among 113 KD patients, 32 (28.3%) were younger than 1 year. Nineteen patients aged below 6 months, and three below 3 months. The median age was 5.7 ± 2.7 months. The mean time to diagnosis was 7 ± 3 days and was longer in the incomplete forms (8 ± 4 vs 6 ± 1 days). Conjunctival injection was present in 26 patients (81.2%); rash in 25 (78.1%); extremity changes in 18 (56.2%); mucosal changes in 13 (40.6%,) and lymphadenopathy only in 7 (21.8%). Mucosal changes were the least common features in incomplete forms (18.2%). Twenty-two patients (68.7%) had incomplete KD. Nineteen (59.4%) had cardiac involvement, of whom 13 (59.0%) had incomplete form. ESR, PCR and platelet values were higher in complete KD; especially, ESR resulted significantly higher in complete forms (80 ± 25.7 mm/h vs 50 ± 28.6 mm/h; p = 0.01). Conversely, AST level was statistically significant higher in patients with incomplete forms (95.4 ± 132.7 UI/L vs 29.8 ± 13.2 UI/L; p = 0.03). All patients received IVIG. Response was reported in 26/32 patients; 6 cases needed a second dose of IVIG and one required a dose of anakinra.

Conclusion

In our cohort, incomplete disease was commonly found, resulting in delayed diagnoses and poor cardiac prognosis. Infants with incomplete KD seem to have a more severe disease and a greater predilection for coronary involvement than those with complete KD. AST was significantly higher in incomplete forms, thus AST levels might be a new finding in incomplete forms’ diagnosis. Eventually, we highlight a higher resistance to IVIG treatment. To our knowledge this is the first study involving an Italian cohort of patients with KD below 12 months.

Recognition of alpha-mannan by dectin 2 is essential for onset of Kawasaki disease-like murine vasculitis induced by Candida albicans cell-wall polysaccharide

Objectives: Using a murine model of systemic Kawasaki disease (KD)-like vasculitis induced by Candida albicans cell-wall-derived mannan · β-glucan · protein complexes, the objective was to elucidate the relationships of β-glucan receptor dectin-1 (D1) and α-mannan receptor dectin-2 (D2) to the onset of that vasculitis.Methods: The incidence and histological severity of vasculitis were compared among mice lacking the genes for D1 or D2 (i.e. D1^-/- and D2^-/-) and wild-type (WT) mice.Results: The incidences of vasculitis in the three animal groups were 100% (18/18) in the WT group, 100% (18/18) in the D1^-/- group, and 0% (0/18) in the D2^-/- group. In the WT and D1^-/- mice, severe inflammatory cell infiltration, consisting mainly of neutrophils and macrophages, was seen in the aortic root and the coronary arteries. On the other hand, in the D2^-/- mice, not even mild vascular lesions such as endoarteritis were seen.Conclusion: Recognition of α-mannan by D2 played an important role in the onset of vasculitis in the studied murine model.

B Cells and Antibodies in Kawasaki Disease

The etiology of Kawasaki disease (KD), the leading cause of acquired heart disease in children, is currently unknown. Epidemiology supports a relationship of KD to an infectious disease. Several pathological mechanisms are being considered, including a superantigen response, direct invasion by an infectious etiology or an autoimmune phenomenon. Treating affected patients with intravenous immunoglobulin is effective at reducing the rates of coronary aneurysms. However, the role of B cells and antibodies in KD pathogenesis remains unclear. Murine models are not clear on the role for B cells and antibodies in pathogenesis. Studies on rare aneurysm specimens reveal plasma cell infiltrates. Antibodies generated from these aneurysmal plasma cell infiltrates showed cross-reaction to intracellular inclusions in the bronchial epithelium of a number of pathologic specimens from children with KD. These antibodies have not defined an etiology. Notably, a number of autoantibody responses have been reported in children with KD. Recent studies show acute B cell responses are similar in children with KD compared to children with infections, lending further support of an infectious disease cause of KD. Here, we will review and discuss the inconsistencies in the literature in relation to B cell responses, specific antibodies, and a potential role for humoral immunity in KD pathogenesis or diagnosis.

A critical appraisal of the role of intracellular Ca2+-signaling pathways in Kawasaki disease

Kawasaki disease is a multi-systemic vasculitis that generally occurs in children and that can lead to coronary artery lesions. Recent studies showed that Kawasaki disease has an important genetic component. In this review, we discuss the single-nucleotide polymorphisms in the genes encoding proteins with a role in intracellular Ca²⁺ signaling: inositol 1,4,5-trisphosphate 3-kinase C, caspase-3, the store-operated Ca²⁺-entry channel ORAI1, the type-3 inositol 1,4,5-trisphosphate receptor, the Na⁺/Ca²⁺ exchanger 1, and phospholipase Cß4 and Cß1. An increase of the free cytosolic Ca²⁺ concentration is proposed to be a major factor in susceptibility to Kawasaki disease and disease outcome, but only for polymorphisms in the genes encoding the inositol 1,4,5-trisphosphate 3-kinase C and the Na⁺/Ca²⁺ exchanger 1, the free cytosolic Ca²⁺ concentration was actually measured and shown to be increased. Excessive cytosolic Ca²⁺ signaling can result in hyperactive calcineurin in T cells with an overstimulated nuclear factor of activated T cells pathway, in hypersecretion of interleukin-1ß and tumor necrosis factor-α by monocytes/macrophages, in increased urotensin-2 signaling, and in an overactivation of vascular endothelial cells.

Adjunctive therapies in Kawasaki disease

Despite the administration of intravenous immunoglobulin (IVIg) at a dose of 2 g/kg, approximately 3-5% of children with acute Kawasaki disease (KD) may develop coronary artery aneurysms. IVIg-resistance, defined as recrudescence of fever more than 36 h after IVIg completion, is a risk factor for coronary artery abnormalities. Thus, several adjunctive therapies are being evaluated for use in IVIg-resistant KD patients and in patients with coronary artery abnormalities. In this review the role of some of these adjunctive therapies in treatment of children with KD is discussed.

Association of Toll-like receptor 2-positive monocytes with coronary artery lesions and treatment nonresponse in Kawasaki disease

Purpose

Activation of Toll-like receptor 2 (TLR2) present on circulating monocytes in patients with Kawasaki disease (KD) can lead to the production of proinflammatory cytokines and interleukin-10 (IL-10). We aimed to determine the association of the frequency of circulating TLR2+/CD14+ monocytes (FTLR2%) with the outcomes of KD, as well as to compare FTLR2% to the usefulness of sIL-10.

Methods

The FTLR2% in patients with KD was measured by flow cytometry. Serum levels of IL-10 (sIL-10) were determined in 31 patients with KD before the initial treatment with intravenous immunoglobulin (IVIG) and in 21 febrile controls by using enzyme-linked immunosorbent assay. Patients were classified as having coronary artery lesions (CALs) based on the maximal internal diameters of the proximal right coronary artery and proximal left anterior descending coronary artery one month after the initial diagnosis.

Results

We found that FTLR2% greater than 92.62% predicted CALs with 80% sensitivity and 68.4% specificity, whereas FTLR2% more than 94.61% predicted IVIG resistance with 66.7% sensitivity and 71.4% specificity. Moreover, sIL-10 more than 15.52 pg/mL predicted CALs and IVIG resistance with 40% and 66.7% sensitivity, respectively, and 73.7% and 76.2% specificity, respectively.

Conclusion

We showed that measuring FTLR2% before the initial treatment could be useful in predicting CAL development with better sensitivity than sIL-10 and with results comparable to sIL-10 results for the prediction of IVIG resistance in patients with KD. However, further studies are necessary to validate FTLR2% as a marker of prognosis and severity of KD.

Identifying genetic hypomethylation and upregulation of Toll-like receptors in Kawasaki disease

Kawasaki disease (KD) is an acute febrile systemic vasculitis that occurs in children and is characterized by elevated levels of proinflammatory cytokines. Toll-like receptors (TLRs) serve as the sensor arm of the innate immune system and induce proinflammatory cytokine expressions.

We recruited a total of 18 paired KD patients, before intravenous immunoglobulin (IVIG) and at least 3 weeks after IVIG treatment, 18 healthy controls, and 18 febrile controls. For TLR genes and their cytosine-phosphate-guanine (CpG) markers, we used Affymetrix GeneChip^® Human Transcriptome Array 2.0 and Illumina HumanMethylation450 BeadChip to evaluate gene expression levels and methylation patterns, respectively.

KD patients demonstrated a significantly differential expression of TLR mRNA levels compared to both the healthy and febrile controls, with only TLR 3 and 7 not differing between the KD patients and the controls. After patients underwent IVIG treatment, the TLR mRNA levels, except for TLR3, decreased significantly in KD patients. In contrast, the methylation status of the CpG sites of TLR1, 2, 4, 6, 8, and 9 demonstrated an opposite tendency between the two stages of both the KD samples and the controls.

TLRs, particularly TLR1, 2, 4, 6, 8, and 9, may stimulate the immunopathogenesis of KD. These results are among the first to use TLRs to prove that a bacterial inflammatory response may trigger KD.

CD8+ T Cells Contribute to the Development of Coronary Arteritis in the Lactobacillus casei Cell Wall Extract-Induced Murine Model of Kawasaki Disease

OBJECTIVE

Kawasaki disease (KD) is the leading cause of acquired heart disease among children in developed countries. Coronary lesions in KD in humans are characterized by an increased presence of infiltrating CD3+ T cells; however, the specific contributions of the different T cell subpopulations in coronary arteritis development remain unknown. Therefore, we sought to investigate the function of CD4+ and CD8+ T cells, Treg cells, and natural killer (NK) T cells in the pathogenesis of KD.

METHODS

We addressed the function of T cell subsets in KD development by using a well-established murine model of Lactobacillus casei cell wall extract (LCWE)-induced KD vasculitis. We determined which T cell subsets were required for development of KD vasculitis by using several knockout murine strains and depleting monoclonal antibodies.

RESULTS

LCWE-injected mice developed coronary lesions characterized by the presence of inflammatory cell infiltrates. Frequently, this chronic inflammation resulted in complete occlusion of the coronary arteries due to luminal myofibroblast proliferation (LMP) as well as the development of coronary arteritis and aortitis. We found that CD8+ T cells, but not CD4+ T cells, NK T cells, or Treg cells, were required for development of KD vasculitis.

CONCLUSION

The LCWE-induced murine model of KD vasculitis mimics many histologic features of the disease in humans, such as the presence of CD8+ T cells and LMP in coronary artery lesions as well as epicardial coronary arteritis. Moreover, CD8+ T cells functionally contribute to the development of KD vasculitis in this murine model. Therapeutic strategies targeting infiltrating CD8+ T cells might be useful in the management of KD in humans.

IL-1 Inhibition May Have an Important Role in Treating Refractory Kawasaki Disease

Kawasaki disease (KD) is an acute inflammatory vasculitis occurring in young children before 5 years and representing at this age, the main cause of acquired heart disease. A single infusion of 2 g/kg of intravenous immunoglobulins along with aspirin has reduced the frequency of coronary artery aneurysms from 25 to 5%. However, 10-20% of patients do not respond to standard treatment and have an increased risk of cardiac complications and death. The development of more potent therapeutic approaches of KD is an urgent need. Phenotypical and immunological similarities between KD and systemic juvenile idiopathic arthritis led to the hypothesis that KD could be considered as an autoinflammatory disease. New insights regarding KD's pathogenesis have merged from the combination of genetic and transcriptomic data revealing the key role of interleukin-1 (IL-1) signaling in the pathogenesis of the vasculitis. Once activated, IL-1α and IL-1β trigger a local proinflammatory environment-inducing vasodilatation and attracting monocytes and neutrophils to sites causing tissue damage and stress. Both IL-1α and IL-1β have been shown to induce myocarditis and aneurysm formation in Lactobacillus casei cell-wall extract mouse model of KD; both being successfully improved with IL-1 blockade treatment such as anakinra. Treatment failure in patients with the high-risk inositol-triphosphate 3-kinase C genotype was associated with highest basal and stimulated intracellular calcium levels, increased cellular production of IL-1β, and IL-18, and higher circulating levels of both cytokines. Three clinical trials of IL-1 blockade enrolling KD patients are currently being conducted in Western Europe and in USA, they could change KD outcome.

Review: Found in Translation: International Initiatives Pursuing Interleukin-1 Blockade for Treatment of Acute Kawasaki Disease

The decision to move forward with three clinical trials of IL-1 blockade for treatment of acute Kawasaki disease is a case study in translational science. These trials were born on the one hand from transcriptome studies of host response during the acute disease coupled with animal model investigations of key immune signaling pathways and, on the other hand, out of clinical desperation to intervene in patients with severe inflammation in the setting of acute Kawasaki disease. The convergence of laboratory science and clinical observations led to the clinical trials described here and serves as a model for how such observations can be translated into new therapies.

Nociceptin reduces the inflammatory immune microenvironment in a conventional murine model of airway hyperresponsiveness

BACKGROUND

Nociceptin/orphanin FQ (N/OFQ) and its receptor (NOP) are involved in airway hyperresponsiveness (AHR) and inflammation. However, the role of nociceptin at modulating the inflammatory immune microenvironment in asthma is still unclear.

OBJECTIVE

To understand the role of N/OFQ in the regulation of a Th2-like environment, we used a conventional murine model of AHR.

METHODS

Balb/c and CD1 mice were sensitized to ovalbumin (OVA) and treated with saline solution or N/OFQ, at days 0 and 7. A group of Balb/c mice were killed at 7 and 14 days from the first sensitization for the inflammatory profile evaluation while a group of Balb/c and CD1 mice were aerosol-challenged from day 21 to 23 with OVA and killed 24 h later for functional evaluations.

RESULTS

In OVA-sensitized mice, N/OFQ significantly reduced IL-4+ CD4+ T cells in lymph nodes (LN) and IL-13 in the lungs, while it induced IFN-γ increase in the lung. The efflux of dendritic cells (DCs) to the mediastinic LN and into the lung of OVA-sensitized mice was reduced in N/OFQ-treated and sensitized mice. N/OFQ reduced the expression of CD80 on DCs, indicating its ability to modulate the activation of DCs. In a less prone Th2-like environment mice strain, such as CD1 mice, N/OFQ did not modify lung resistances as observed in BALB/c mice. Finally, spectroscopic data showed the N/OFQ was able to interact onto the membrane of DCs obtained from Balb/c rather than CD1 mice, indicating its ability to modulate AHR in a Th2-like environment with a direct activity on DCs.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data confirmed the capability of N/OFQ to modulate the immune microenvironment in the lung of Th2-biased, OVA-sensitized Balb/c mice, suggesting N/OFQ-NOP axis as a novel pharmacological tool to modulate the inflammatory immune microenvironment in asthma.

Endothelial Cell Inflammatory Reactions Are Altered in the Presence of E-Cigarette Extracts of Variable Nicotine

Exposure to tobacco smoke has been associated with heightened endothelial cell activities associated with cardiovascular diseases (CVD). Conversely, the exposure to nicotine both activates and inhibits particular endothelial cell functions. However, which constituent(s) of tobacco smoke is responsible for these changes is unknown, since toxic gases and fine particulate matter cannot be isolated. Electronic cigarette vapor allows us to isolate these constituents, providing us the ability to evaluate individual constituents. Here, we used e-cigarettes to (1) identify which constituents of tobacco products are most responsible for altered CVD functions and (2) elucidate the underlying risk of e-cigarette exposure. To accomplish this goal, endothelial cells were exposed to extracts produced from tobacco cigarettes or e-cigarettes. Endothelial cell inflammatory processes, viability, density and metabolic activity were observed. In general, a significant increase in complement deposition, the expression of the receptors for C1q, coupled with a decrease in cell proliferation and metabolic activity was observed. These results were independent of nicotine and the exposure to e-vapor was just as harmful as tobacco smoke extracts. Thus, the exposure to fine particulate matter and not toxic combustion gases or nicotine may be the most critical for regulating CVD progression.

Kawasaki Disease

Kawasaki disease is an acute, self-limited vasculitis of unknown etiology that occurs predominantly in infants and children. If not treated early with high-dose intravenous immunoglobulin, 1 in 5 children develop coronary artery aneurysms; this risk is reduced 5-fold if intravenous immunoglobulin is administered within 10 days of fever onset. Coronary artery aneurysms evolve dynamically over time, usually reaching a peak dimension by 6 weeks after illness onset. Almost all the morbidity and mortality occur in patients with giant aneurysms. Risk of myocardial infarction from coronary artery thrombosis is greatest in the first 2 years after illness onset. However, stenosis and occlusion progress over years. Indeed, Kawasaki disease is no longer a rare cause of acute coronary syndrome presenting in young adults. Both coronary artery bypass surgery and percutaneous intervention have been used to treat Kawasaki disease patients who develop myocardial ischemia as a consequence of coronary artery aneurysms and stenosis.

Rationale and study design for a phase I/IIa trial of anakinra in children with Kawasaki disease and early coronary artery abnormalities (the ANAKID trial)

BACKGROUND

Although Kawasaki disease (KD) is the most common cause of acquired heart disease in children and may result in coronary artery aneurysms (CAA) with an attendant risk of myocardial infarction, there is no recommended therapy to halt progression of arterial wall damage and prevent aneurysm formation in the acute phase of the vasculitis. While intravenous immunoglobulin (IVIG) reduces the risk of CAA, up to 20% of KD patients are IVIG resistant and have a higher risk for developing CAA. The IL-1 pro-inflammatory pathway is upregulated in children with acute KD and plays a critical role in the experimental animal model of KD. Thus, IL-1 is a logical therapeutic target.

OBJECTIVES

The goal of this study is to determine the safety, tolerability, pharmacokinetics, and immunomodulatory effects of anakinra, a recombinant human IL-1 receptor antagonist, in acute KD patients with coronary artery abnormalities on the baseline echocardiogram.

DESIGN

This is a two-center dose-escalation Phase I/IIa trial in 30 acute KD patients ≥8months old with a coronary artery Z score≥3.0 in the right coronary artery and/or left anterior descending artery or an aneurysm. Subjects will receive a 2- to 6-week course of anakinra by daily subcutaneous injection and will be assessed for resolution of inflammation and dose limiting toxicities (leukopenia, anaphylactoid reaction, or severe infection).

CONCLUSION

The safety and tolerability of blocking both IL-1α and Il-1β by anakinra will be evaluated as a strategy to prevent or attenuate coronary artery damage in infants and children with acute KD.

TRIAL REGISTRATION

Clinical Trials.gov # NCT02179853, registered June 28, 2014.

Interferon-gamma Genetic Polymorphism and Expression in Kawasaki Disease

Kawasaki disease (KD) is a systemic vasculitis of unknown etiology. IFNG gene encoding interferon (IFN)-γ, produced by natural killer cells and T cells, has been suggested to play an important role in the immunopathogenesis of Kawasaki disease. The aim of this study was to examin the correlation of gene polymorphisms of the IFNG gene and plasma levels of IFN-γ in KD patients and their outcomes.A total of 950 subjects (381 KD and 569 controls) were recruited. Three tagging single-nucleotide polymorphisms (rs2069718, rs1861493, rs2069705) were selected for TaqMan allelic discrimination assay. Clinical phenotypes, coronary artery lesions (CAL), coronary artery aneurysms (CAA) and intravenous immunoglobulin (IVIG) treatment outcomes were collected for analysis. Plasma IFN-γ levels were also measured with an enzyme-linked immunosorbent assay.Polymorphisms of the IFNG gene were significantly different between the normal controls and KD patients. The G allele of rs1861493 conferred a better response to IVIG treatment in KD patients. AA allele frequencies of rs1861493 were also associated with a significantly higher risk of CAA in KD patients. Furthermore, the plasma IFN-γ level was lower in the AA allele than in the GG allele of rs1861493 both before and after IVIG treatment in KD patients.This study provides the first evidence supporting an association between IFNG gene polymorphisms, susceptibility of KD, IVIG responsiveness, and plasma IFN-γ levels in KD patients.

Role of Interleukin-1 Signaling in a Mouse Model of Kawasaki Disease-Associated Abdominal Aortic Aneurysm

OBJECTIVE

Kawasaki disease (KD) is the most common cause of acquired cardiac disease in US children. In addition to coronary artery abnormalities and aneurysms, it can be associated with systemic arterial aneurysms. We evaluated the development of systemic arterial dilatation and aneurysms, including abdominal aortic aneurysm (AAA) in the Lactobacillus casei cell-wall extract (LCWE)-induced KD vasculitis mouse model.

METHODS AND RESULTS

We discovered that in addition to aortitis, coronary arteritis and myocarditis, the LCWE-induced KD mouse model is also associated with abdominal aorta dilatation and AAA, as well as renal and iliac artery aneurysms. AAA induced in KD mice was exclusively infrarenal, both fusiform and saccular, with intimal proliferation, myofibroblastic proliferation, break in the elastin layer, vascular smooth muscle cell loss, and inflammatory cell accumulation in the media and adventitia. Il1r(-/-), Il1a(-/-), and Il1b(-/-) mice were protected from KD associated AAA. Infiltrating CD11c(+) macrophages produced active caspase-1, and caspase-1 or NLRP3 deficiency inhibited AAA formation. Treatment with interleukin (IL)-1R antagonist (Anakinra), anti-IL-1α, or anti-IL-1β mAb blocked LCWE-induced AAA formation.

CONCLUSIONS

Similar to clinical KD, the LCWE-induced KD vasculitis mouse model can also be accompanied by AAA formation. Both IL-1α and IL-1β play a key role, and use of an IL-1R blocking agent that inhibits both pathways may be a promising therapeutic target not only for KD coronary arteritis, but also for the other systemic arterial aneurysms including AAA that maybe seen in severe cases of KD. The LCWE-induced vasculitis model may also represent an alternative model for AAA disease.

Recent Advances in Kawasaki Disease

Kawasaki disease (KD) is characterized with acute systemic vasculitis, occurs predominantly in children between 6 months to 5 years of age. Patients with this disease recover well and the disease is self-limited in most cases. Since it can lead to devastating cardiovascular complications, KD needs special attention. Recent reports show steady increases in the prevalence of KD in both Japan and Korea. However, specific pathogens have yet to be found. Recent advances in research on KD include searches for genetic susceptibility related to KD and research on immunopathogenesis based on innate and acquired immunity. Also, search for etiopathogenesis and treatment of KD has been actively sought after using animal models. In this paper, the recent progress of research on KD was discussed.

IL-1 Signaling Is Critically Required in Stromal Cells in Kawasaki Disease Vasculitis Mouse Model: Role of Both IL-1α and IL-1β

OBJECTIVE

Kawasaki disease (KD) is the most common cause of acute vasculitis and acquired cardiac disease among US children. We have previously shown that both TLR2/MyD88 and interleukin (IL)-1β signaling are required for the Lactobacillus casei cell wall extract-induced KD vasculitis mouse model. The objectives of this study were to investigate the cellular origins of IL-1 production, the role of CD11c(+) dendritic cells and macrophages, and the relative contribution of hematopoietic and stromal cells for IL-1 responsive cells, as well the MyD88 signaling, in Lactobacillus casei cell wall extract-induced KD mouse model of vasculitis.

APPROACH AND RESULTS

Using mouse knockout models and antibody depletion, we found that both IL-1α and IL-1β were required for Lactobacillus casei cell wall extract-induced KD. Both dendritic cells and macrophages were necessary, and we found that MyD88 signaling was required in both hematopoietic and stromal cells. However, IL-1 response and signaling were critically required in nonendothelial stromal cells, but not in hematopoietic cells.

CONCLUSIONS

Our results suggest that IL-1α and IL-1β, as well as CD11c(+) dendritic cells and macrophages, are essential for the development of KD vasculitis and coronary arteritis in this mouse model. Bone marrow chimera experiments suggest that MyD88 signaling is important in both hematopoietic and stromal cells, whereas IL-1 signaling and response are required only in stromal cells, but not in endothelial cells. Determining the role of IL-1α and IL-1β and of specific cell types in the KD vasculitis mouse model may have important implications for the design of more targeted therapies and understanding of the molecular mechanisms of KD immunopathologies.

Macrophages in vascular inflammation--From atherosclerosis to vasculitis

The spectrum of vascular inflammatory disease ranges from atherosclerosis and hypertension, widespread conditions affecting large proportions of the population, to the vasculitides, rare syndromes leading to fast and irreversible organ failure. Atherosclerosis progresses over decades, inevitably proceeding through multiple phases of disease and causes its major complications when the vessel wall lesion ruptures, giving rise to lumen-occlusive atherothrombosis. Vasculitides of medium and large arteries progress rapidly, causing tissue ischemia through lumen-occlusive intimal hyperplasia. In both disease entities, macrophages play a decisive role in pathogenesis, but function in the context of other immune cells that direct their differentiation and their functional commitments. In atherosclerosis, macrophages are involved in the removal of lipids and tissue debris and make a critical contribution to tissue damage and wall remodeling. In several of the vasculitides, macrophages contribute to granuloma formation, a microstructural platform optimizing macrophage-T-cell interactions, antigen containment and inflammatory amplification. By virtue of their versatility and plasticity, macrophages are able to promote a series of pathogenic functions, ranging from the release of cytokines and enzymes, the production of reactive oxygen species, presentation of antigen and secretion of tissue remodeling factors. However, as short-lived cells that lack memory, macrophages are also amendable to reprogramming, making them promising targets for anti-inflammatory interventions.

Single-nucleotide polymorphism rs7251246 in ITPKC is associated with susceptibility and coronary artery lesions in Kawasaki disease

Kawasaki disease (KD) is a multi-systemic vasculitis that preferentially affects children. A single nucleotide polymorphism (SNP) in inositol 1,4,5-trisphosphate 3-kinase C (ITPKC) has been identified to be an important polymorphism in the risk of KD. This study was conducted to comprehensively investigate the associations between all tagging SNPs of ITPKC in the risk of KD in a Taiwanese population. A total of 950 subjects (381 KD patients and 569 controls) were recruited. Seven tagging SNPs (rs11673492, rs7257602, rs7251246, rs890934, rs10420685, rs2607420, rs2290692) were selected for TaqMan allelic discrimination assay. Clinical data of coronary artery lesions (CAL) and aneurysms were collected for analysis. A significant association was found between rs7251246 in ITPKC and CAL formation. Haplotype analysis for ITPKC polymorphisms also confirmed this association in the patients with CAL and aneurysm formation. This is the first study to identify that SNP rs7251246 in ITPKC is associated with the severity of KD.

Urine proteomics for discovery of improved diagnostic markers of Kawasaki disease

Kawasaki disease (KD) is a systemic vasculitis of unknown etiology. Absence of definitive diagnostic markers limits the accuracy of clinical evaluations of suspected KD with significant increases in morbidity. In turn, incomplete understanding of its molecular pathogenesis hinders the identification of rational targets needed to improve therapy. We used high-accuracy mass spectrometry proteomics to analyse over 2000 unique proteins in clinical urine specimens of patients with KD. We discovered that urine proteomes of patients with KD, but not those with mimicking conditions, were enriched for markers of cellular injury such as filamin and talin, immune regulators such as complement regulator CSMD3, immune pattern recognition receptor muclin, and immune cytokine protease meprin A. Significant elevations of filamin C and meprin A were detected in both the serum and urine in two independent cohorts of patients with KD, comprised of a total of 236 patients. Meprin A and filamin C exhibited superior diagnostic performance as compared to currently used markers of disease in a blinded case-control study of 107 patients with suspected KD, with receiver operating characteristic areas under the curve of 0.98 (95% confidence intervals [CI] of 0.97-1 and 0.95-1, respectively). Notably, meprin A was enriched in the coronary artery lesions of a mouse model of KD. In all, urine proteome profiles revealed novel candidate molecular markers of KD, including filamin C and meprin A that exhibit excellent diagnostic performance. These disease markers may improve the diagnostic accuracy of clinical evaluations of children with suspected KD, lead to the identification of novel therapeutic targets, and allow the development of a biological classification of Kawasaki disease.

Plasmacytoid dendritic cells: biomarkers or potential therapeutic targets in atherosclerosis?

Plasmacytoid dendritic cells (pDCs) represent a unique subset of dendritic cells that play distinct and critical roles in the immune response. Importantly, pDCs play a pivotal role in several chronic autoimmune diseases strongly characterized by an increased risk of vascular pathology. Clinical studies have shown that pDCs are detectable in atherosclerotic plaques and others have suggested an association between reduced numbers of circulating pDCs and cardiovascular events. Although the causal relationship between pDCs and atherosclerosis is still uncertain, recent results from mouse models are starting to define the specific role(s) of pDCs in the disease process. In this review, we will discuss the role of pDCs in innate and adaptive immunity, the emerging evidence demonstrating the contribution of pDCs to vascular pathology and we will consider the possible impact of pDCs on the acceleration of atherosclerosis in chronic inflammatory autoimmune diseases. Finally, we will discuss how pDCs could be targeted for therapeutic utility.

Calcineurin inhibitor treatment of intravenous immunoglobulin-resistant Kawasaki disease

OBJECTIVE

To describe the clinical course and outcome of 10 patients with Kawasaki disease (KD) treated with a calcineurin inhibitor after failing to respond to multiple therapies.

STUDY DESIGN

Demographic and clinical data were prospectively collected using standardized case report forms. T-cell phenotypes were determined by flow cytometry, and KD risk alleles in ITPKC (rs28493229), CASP3 (rs72689236), and FCGR2A (rs1801274) were genotyped.

RESULTS

Intravenous followed by oral therapy with cyclosporine (CSA) or oral tacrolimus was well tolerated and resulted in defervescence and resolution of inflammation in all 10 patients. There were no serious adverse events, and a standardized treatment protocol was developed based on our experiences with this patient population. Analysis of T-cell phenotype by flow cytometry in 2 subjects showed a decrease in circulating activated CD8(+) and CD4(+) T effector memory cells after treatment with CSA. However, suppression of regulatory T-cells was not seen, suggesting targeting of specific, proinflammatory T-cell compartments by CSA.

CONCLUSION

Treatment of refractory KD with a calcineurin inhibitor appears to be a safe and effective approach that achieves rapid control of inflammation associated with clinical improvement.

Augmented TLR2 expression on monocytes in both human Kawasaki disease and a mouse model of coronary arteritis

BACKGROUND

Kawasaki disease (KD) of unknown immunopathogenesis is an acute febrile systemic vasculitis and the leading cause of acquired heart diseases in childhood. To search for a better strategy for the prevention and treatment of KD, this study compared and validated human KD immunopathogenesis in a mouse model of Lactobacillus casei cell wall extract (LCWE)-induced coronary arteritis.

METHODS

Recruited subjects fulfilled the criteria of KD and were admitted for intravenous gamma globulin (IVIG) treatment at the Kaohsiung Chang Gung Memorial Hospital from 2001 to 2009. Blood samples from KD patients were collected before and after IVIG treatment, and cardiovascular abnormalities were examined by transthoracic echocardiography. Wild-type male BALB/c mice (4-week-old) were intraperitoneally injected with LCWE (1 mg/mL) to induce coronary arteritis. The induced immune response in mice was examined on days 1, 3, 7, and 14 post injections, and histopathology studies were performed on days 7 and 14.

RESULTS

Both human KD patients and LCWE-treated mice developed coronary arteritis, myocarditis, valvulitis, and pericarditis, as well as elevated plasma levels of interleukin (IL)-2, IL-6, IL-10, monocyte chemoattractant protein (MCP)-1, and tumor necrosis factor (TNF)-α in acute phase. Most of these proinflammatory cytokines declined to normal levels in mice, whereas normal levels were achieved in patients only after IVIG treatment, with a few exceptions. Toll-like receptor (TLR)-2, but not TLR4 surface enhancement on circulating CD14+ monocytes, was augmented in KD patients before IVIG treatment and in LCWE-treated mice, which declined in patients after IVIG treatment.

CONCLUSION

This result suggests that that not only TLR2 augmentation on CD14+ monocytes might be an inflammatory marker for both human KD patients and LCWE-induced CAL mouse model but also this model is feasible for studying therapeutic strategies of coronary arteritis in human KD by modulating TLR2-mediated immune activation on CD14+ monocytes.

Dectin-1/Syk signaling is involved in Lactobacillus casei cell wall extract-induced mouse model of Kawasaki disease

Kawasaki disease (KD) is not only the leading cause of childhood acquired heart diseases, but also causes profound coronary artery sequelae due to chronic vascular inflammation in adulthood. Of unknown underlying mechanism, both innate and adaptive immune responses are involved in the pathogenesis of coronary artery lesions (CALs). We investigated the role of dectin-1/spleen tyrosine kinase (Syk) pathway on macrophage in responsive to Lactobacillus casei cell wall extract (LCWE) in vitro and in vivo. We found that LCWE induced in vitro macrophage activation with increased production of IL-6, TNF-α, and MCP-1, concomitantly with Syk activation, and dectin-1 and TLR2 enhancement. In vivo, LCWE induced infiltration of dectin-1(+) macrophages into CALs and cardiac upregulation of IL-6 and MCP-1 on day 14 post-injection. Most importantly, Syk inhibition alleviated LCWE-induced arteritis in BALB/c mice. Blockade of either dectin-1 or Syk significantly inhibited LCWE-induced IL-6 and MCP-1 production both in vitro and in vivo. This study demonstrates that the macrophage dectin-1/Syk-mediated pathway is involved in LCWE-induced CALs and production of IL-6 and MCP-1. Given the functional equivalence of human dectin-1 to murine, the importance of dectin-1/Syk pathway in the development of murine CALs warrants further investigation on their roles in human KD.

Kawasaki disease: laboratory findings and an immunopathogenesis on the premise of a "protein homeostasis system"

Kawasaki disease (KD) is a self-limited systemic inflammatory illness, and coronary artery lesions (CALs) are a major complication determining the prognosis of the disease. Epidemiologic studies in Asian children suggest that the etiologic agent(s) of KD may be associated with environmental changes. Laboratory findings are useful for the diagnosis of incomplete KD, and they can guide the next-step in treatment of initial intravenous immunoglobulin non-responders. CALs seem to develop in the early stages of the disease before a peak in inflammation. Therefore early treatment, before the peak in inflammation, is mandatory to reduce the risk of CAL progression and severity of CALs. The immunopathogenesis of KD is more likely that of acute rheumatic fever than scarlet fever. A hypothetical pathogenesis of KD is proposed under the premise of a "protein homeostasis system"; where innate and adaptive immune cells control pathogenic proteins that are toxic to host cells at a molecular level. After an infection of unknown KD pathogen(s), the pathogenic proteins produced from an unknown focus, spread and bind to endothelial cells of coronary arteries as main target cells. To control the action of pathogenic proteins and/or substances from the injured cells, immune cells are activated. Initially, non-specific T cells and non-specific antibodies are involved in this reaction, while hyperactivated immune cells produce various cytokines, leading to a cytokine imbalance associated with further endothelial cell injury. After the emergence of specific T cells and specific antibodies against the pathogenic proteins, tissue injury ceases and a repair reaction begins with the immune cells.

Interleukin-1β is crucial for the induction of coronary artery inflammation in a mouse model of Kawasaki disease

BACKGROUND

Kawasaki disease (KD) is the most common cause of acute vasculitis and acquired cardiac disease in US children. Untreated, children may develop coronary artery aneurysms, myocardial infarction, and sudden death as a result of the illness. Up to a third of KD patients fail to respond to intravenous immunoglobulin, the standard therapy, and alternative treatments are being investigated. Genetic studies have indicated a possible role for interleukin (IL)-1β in KD. We therefore explored the role of IL-1β in a murine model of KD.

METHODS AND RESULTS

Using an established mouse model of KD that involves injection of Lactobacillus casei cell wall extract (LCWE), we investigated the role of IL-1β and caspase-1 (activated by the inflammasome and required for IL-1β maturation) in coronary arteritis and evaluated the efficacy of IL-1 receptor antagonist as a potential treatment. LCWE-induced IL-1β maturation and secretion were dependent on the NLRP3 inflammasome in macrophages. Both caspase-1-deficient and IL-1 receptor-deficient mice were protected from LCWE-induced coronary lesions. Injection of recombinant IL-1β into caspase-1-deficient mice restored the ability of LCWE to cause coronary lesions in response to LCWE. Furthermore, daily injections of the IL-1 receptor antagonist prevented LCWE-mediated coronary lesions up to 3 days after LCWE injection.

CONCLUSIONS

Our results strongly suggest that caspase-1 and IL-1β play critical roles in the development of coronary lesions in this KD mouse model, blocked by IL-1 receptor antagonist. Therefore, anti-IL-1β treatment strategies may constitute an effective, more targeted treatment of KD to prevent coronary lesions.

The Molecular Biology and Treatment of Systemic Vasculitis in Children

Primary systemic vasculitides are rare in childhood but are associated with significant morbidity and mortality. The cause of the majority of vasculitides is unknown, although it is likely that a complex interaction between environmental factors, such as infections and inherited host responses, triggers the disease and determines the vasculitis phenotype. Several genetic polymorphisms in vasculitides have now been described, which may be relevant in terms of disease predisposition or development of disease complications. Treatment regimens continue to improve with the use of different immunosuppressive medications and newer therapeutic approaches such as biologic agents. This chapter reviews recent studies shedding light on the pathogenesis of vasculitis with emphasis on molecular biology where known, and summarizes current treatment strategies. We discuss new emerging challenges particularly with respect to the long-term cardiovascular morbidity for children with systemic vasculitis and emphasize the importance of future international multicenter collaborative studies to further increase and standardize the scientific base investigating and treating childhood vasculitis.

T cell costimulatory and coinhibitory pathways in vascular inflammatory diseases

A broad array of evidence indicates that T lymphocytes make significant contributions to vascular inflammation in the setting of atherosclerotic disease, hypertension, autoimmune vasculitis, and other disorders. Experimental data show that costimulatory and coinhibitory pathways involving molecules of the B7-CD28 and TNF–TNFR families regulate T cell responses that promote vascular disease. Antigen presenting cells (APCs) display both peptide–major histocompatibility complex antigen and costimulators or coinhibitors to T cells. Two major types of APCs, dendritic cells (DCs) and macrophages, are present in significant numbers in the walls of arteries affected by atherosclerosis and arteritis, and some DCs are present in normal arteries. Costimulatory and coinhibitory molecules expressed by these vascular APCs can contribute to the activation or inhibition of effector T cells within the arterial wall. Vascular DCs may also be involved in transport of antigens to secondary lymphoid organs, where they activate or tolerize naïve T cells, depending on the balance of costimulators and coinhibitors they express. Costimulatory blockade is already an approved therapeutic approach to treat autoimmune disease and prevent transplant rejection. Preclinical models suggest that costimulatory blockade may also be effective in treating vascular disease. Experiential data in mice show that DCs pulsed with the appropriate antigens and treated in a way that reduces costimulatory capacity can reduce atherosclerotic disease, presumably by inducing T cell tolerance. Progress in treating vascular disease by immune modulation will require a more complete understanding of the functions of different costimulatory and coinhibitory pathways and the different subsets of vascular APCs involved.

Pathogénie de la maladie de Kawasaki : quoi de neuf ?

La maladie de Kawasaki (MK) est une vascularite inflammatoire aiguë survenant le plus souvent chez le nourrisson et dont le pronostic est dicté par l’atteinte coronarienne. La cause de cette maladie reste inconnue mais différentes hypothèses ont été développées ces dernières années et s’associent à des travaux de recherche pour la compréhension de la physiopathologie de la MK. La présentation clinique de la MK partage de nombreux signes avec des maladies infectieuses virales et bactériennes. La possibilité d’une maladie infectieuse à superantigène a été suggérée. La fréquence augmentée dans certaines populations, la survenue précoce à l’âge pédiatrique supporte la participation de facteurs génétiques dans le développement de la maladie. Certaines anomalies immunologiques sont également retrouvées chez les sujets présentant une MK, suggérant qu’un déséquilibre immunologique est à l’origine de la vascularite.

Inhibition of transforming growth factor β worsens elastin degradation in a murine model of Kawasaki disease

Kawasaki disease (KD) is an acute inflammatory illness marked by coronary arteritis. However, the factors increasing susceptibility to coronary artery lesions are unknown. Because transforming growth factor (TGF) β increases elastin synthesis and suppresses proteolysis, we hypothesized that, in contrast to the benefit observed in aneurysms forming in those with Marfan syndrome, inhibition of TGF-β would worsen inflammatory-induced coronary artery lesions. By using a murine model of KD in which injection of Lactobacillus casei wall extract (LCWE) induces coronary arteritis, we show that LCWE increased TGF-β signaling in the coronary smooth muscle cells beginning at 2 days and continuing through 14 days, the point of peak coronary inflammation. By 42 days, LCWE caused fragmentation of the internal and external elastic lamina. Blocking TGF-β by administration of a neutralizing antibody accentuated the LCWE-mediated fragmentation of elastin and induced an overall loss of medial elastin without increasing the inflammatory response. We attributed these increased pathological characteristics to a reduction in the proteolytic inhibitor, plasminogen activator inhibitor-1, and an associated threefold increase in matrix metalloproteinase 9 activity compared with LCWE alone. Therefore, our data demonstrate that in the coronary arteritis associated with KD, TGF-β suppresses elastin degradation by inhibiting plasmin-mediated matrix metalloproteinase 9 activation. Thus, strategies to block TGF-β, used in those with Marfan syndrome, are unlikely to be beneficial and could be detrimental.

Kawasaki disease: update on pathogenesis

PURPOSE OF REVIEW

This review will highlight recent advances in our understanding of the pathogenesis of Kawasaki disease, highlighting the molecular players involved in regulation of T-cell activation and their affect on disease incidence and outcome in both humans and mouse.

RECENT FINDINGS

Kawasaki disease is the most common cause of multisystem vasculitis in childhood. The vessels most commonly damaged are the coronary arteries, making Kawasaki disease the number one cause of acquired heart disease in children from the developed world. The contribution of genetics to disease predisposition is clearly implicated, but the mechanisms involved in regulating predisposition to disease susceptibility and outcome are not clearly understood. Two independent approaches have recently identified regulation of T-cell activation as the critical factor in determining susceptibility and severity of Kawasaki disease. Firstly, genetic analysis of affected Japanese children identified ITPKC, 1,4,5-triphosphate 3-kinase C, a kinase involved in regulation of T-cell activation, to be significantly associated with susceptibility to and increased severity of Kawasaki disease. A second independent approach using an animal model of Kawasaki disease has also identified regulation of T-cell activation, specifically costimulation, the second signal regulating optimal T-cell activation as the critical regulator of susceptibility to and severity of disease.

SUMMARY

Understanding the molecular players responsible for dysregulation of the immune response in Kawasaki disease will foster development of improved diagnostic/predictive tools and more rational use of therapeutic agents to improve outcome in affected children.

Plasmacytoid dendritic cells: from heart to vessels

Cardiovascular diseases, formerly only attributed to the alterations of the stromal component, are now recognized as immune-based pathologies. Plasmacytoid Dendritic Cells (pDCs) are important immune orchestrators in heart and vessels. They highly produce IFN type I that promote the polarization of T cells towards a Th1 phenotype; however, pDCs can also participate to suppressive networks via the recruitment of T regulatory cells that downmodulate proinflammatory responses. pDCs populate the vessel wall layers during pathological conditions, such as atherosclerosis. It is thus clear that a better identification of pDCs activity in cardiovascular diseases can not only elucidate pathological mechanisms but also lead to new therapeutic approaches.