Cloning the arterial IgA antibody response during acute Kawasaki disease

The Future of Kawasaki Disease Diagnosis: Liquid Biopsy May Hold the Key

Kawasaki disease (KD) is a febrile illness characterised by systemic inflammation of small- and medium-sized blood vessels, which commonly occurs in young children. Although self-limiting, there is a risk of developing coronary artery lesions as the disease progresses, with delay in diagnosis and treatment. Unfortunately, the diagnosis of KD continues to remain a clinical dilemma. Thus, this article not only summarises the key research gaps associated with KD, but also evaluates the possibility of using circulating endothelial injury biomarkers, such as circulating endothelial cells, endothelial microparticles and vascular endothelial cell-free DNA, as diagnostic and prognostic tools for KD: a "liquid biopsy" approach. The challenges of translating liquid biopsies to use in KD and the opportunities for improvement in its diagnosis and management that such translation may provide are discussed. The use of endothelial damage markers, which are easily obtained via blood collection, as diagnostic tools is promising, and we hope this will be translated to clinical applications in the near future.

T Cell Receptor Sequences Amplified during Severe COVID-19 and Multisystem Inflammatory Syndrome in Children Mimic SARS-CoV-2, Its Bacterial Co-Infections and Host Autoantigens

Published hypervariable region V-beta T cell receptor (TCR) sequences were collected from people with severe COVID-19 characterized by having various autoimmune complications, including blood coagulopathies and cardiac autoimmunity, as well as from patients diagnosed with the Kawasaki disease (KD)-like multisystem inflammatory syndrome in children (MIS-C). These were compared with comparable published v-beta TCR sequences from people diagnosed with KD and from healthy individuals. Since TCR V-beta sequences are supposed to be complementary to antigens that induce clonal expansion, it was surprising that only a quarter of the TCR sequences derived from severe COVID-19 and MIS-C patients mimicked SARS-CoV-2 proteins. Thirty percent of the KD-derived TCR mimicked coronaviruses other than SARS-CoV-2. In contrast, only three percent of the TCR sequences from healthy individuals and those diagnosed with autoimmune myocarditis displayed similarities to any coronavirus. In each disease, significant increases were found in the amount of TCRs from healthy individuals mimicking specific bacterial co-infections (especially Enterococcus faecium, Staphylococcal and Streptococcal antigens) and host autoantigens targeted by autoimmune diseases (especially myosin, collagen, phospholipid-associated proteins, and blood coagulation proteins). Theoretical explanations for these surprising observations and implications to unravel the causes of autoimmune diseases are explored.

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.

Single-cell RNA sequencing of peripheral blood mononuclear cells from acute Kawasaki disease patients

Kawasaki disease (KD) is the most common cause of acquired heart disease in children in developed countries. Although functional and phenotypic changes of immune cells have been reported, a global understanding of immune responses underlying acute KD is unclear. Here, using single-cell RNA sequencing, we profile peripheral blood mononuclear cells from seven patients with acute KD before and after intravenous immunoglobulin therapy and from three age-matched healthy controls. The most differentially expressed genes are identified in monocytes, with high expression of pro-inflammatory mediators, immunoglobulin receptors and low expression of MHC class II genes in acute KD. Single-cell RNA sequencing and flow cytometry analyses, of cells from an additional 16 KD patients, show that although the percentage of total B cells is substantially decreased after therapy, the percentage of plasma cells among the B cells is significantly increased. The percentage of CD8+ T cells is decreased in acute KD, notably effector memory CD8+ T cells compared with healthy controls. Oligoclonal expansions of both B cell receptors and T cell receptors are observed after therapy. We identify biological processes potentially underlying the changes of each cell type. The single-cell landscape of both innate and adaptive immune responses provides insights into pathogenesis and therapy of KD.

Severe COVID-19, multisystem inflammatory syndrome in children, and Kawasaki disease: immunological mechanisms, clinical manifestations and management

Multisystem inflammatory syndrome (MIS-C) is a pediatric hyperinflammation disorder caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). It has now been reported from several countries the world over. Some of the clinical manifestations of MIS-C mimic Kawasaki disease (KD) shock syndrome. MIS-C develops 4–6 weeks following SARS-CoV-2 infection, and is presumably initiated by adaptive immune response. Though it has multisystem involvement, it is the cardiovascular manifestations that are most prominent. High titres of anti-SARS-CoV-2 antibodies are seen in these patients. As this is a new disease entity, its immunopathogenesis is not fully elucidated. Whether it has some overlap with KD is still unclear. Current treatment guidelines recommend use of intravenous immunoglobulin and high-dose corticosteroids as first-line treatment. Mortality rates of MIS-C are lower compared to adult forms of severe COVID-19 disease.

Identification of a unique TCR repertoire, consistent with a superantigen selection process in Children with Multi-system Inflammatory Syndrome

Multisystem Inflammatory Syndrome in Children (MIS-C), a hyperinflammatory syndrome associated with SARS-CoV-2 infection, shares many clinical features with toxic shock syndrome, which is triggered by bacterial superantigens. The superantigen specificity for binding different Vβ-chains results in Vβ-skewing, whereby T cells with specific Vβ-chains and diverse antigen specificity are overrepresented in the TCR repertoire. Here, we characterized the TCR repertoire of MIS-C patients and found a profound expansion of TCR Βeta Variable gene (TRBV)11-2. Furthermore, TRBV11-2 skewing was remarkably correlated with MIS-C severity and serum cytokine levels. Further analysis of TRBJ gene usage and CDR3 length distribution of MIS-C expanding TRBV11-2 clones revealed extensive junctional diversity, indicating a superantigen-mediated selection process for TRBV expansion. In silico modelling indicates that polyacidic residues in TCR Vβ11-2 engage in strong interactions with the superantigen-like motif of SARS-CoV-2 spike glycoprotein. Overall, our data indicate that the immune response in MIS-C is consistent with superantigenic activation.

COVID-19: Infection or Autoimmunity

The clinical and laboratory features of COVID-19 are reviewed with attention to the immunologic manifestations of the disease. Recent COVID-19 publications describe a variety of clinical presentations including an asymptomatic state, pneumonia, a hemophagocytic lymphohistiocytosis like syndrome, Multisystem Inflammatory Syndrome in Children (MIS-C) but, also called Pediatric Inflammatory Multisystem Syndrome-Toxic Shock (PIMS-TS), Kawasaki Disease, and myocarditis. A common theme amongst multiple reports suggests an overexuberant autoimmune component of the disease but a common pathophysiology to explain the variations in clinical presentation has been elusive. Review of the basic science of other viral induced autoimmune disorders may give clues as to why immunosuppressive and immunomodulating regimens now appear to have some efficacy in COVID-19. Review of the immunopathology also reveals other therapies that have yet to be explored. There is potential use of T cell depleting therapies and possibly anti-CD20 therapy for COVID-19 and clinical research using these medications is warranted.

A Protein Epitope Targeted by the Antibody Response to Kawasaki Disease

BACKGROUND

Kawasaki disease (KD) is the leading cause of childhood acquired heart disease in developed nations and can result in coronary artery aneurysms and death. Clinical and epidemiologic features implicate an infectious cause but specific antigenic targets of the disease are unknown. Peripheral blood plasmablasts are normally highly clonally diverse but the antibodies they encode are approximately 70% antigen-specific 1-2 weeks after infection.

METHODS

We isolated single peripheral blood plasmablasts from children with KD 1-3 weeks after onset and prepared 60 monoclonal antibodies (mAbs). We used the mAbs to identify their target antigens and assessed serologic response among KD patients and controls to specific antigen.

RESULTS

Thirty-two mAbs from 9 of 11 patients recognize antigen within intracytoplasmic inclusion bodies in ciliated bronchial epithelial cells of fatal cases. Five of these mAbs, from 3 patients with coronary aneurysms, recognize a specific peptide, which blocks binding to inclusion bodies. Sera from 5/8 KD patients day ≥ 8 after illness onset, compared with 0/17 infant controls (P < .01), recognized the KD peptide antigen.

CONCLUSIONS

These results identify a protein epitope targeted by the antibody response to KD and provide a means to elucidate the pathogenesis of this important worldwide pediatric problem.

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.

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.

Vascular repair and anti-inflammatory effects of soluble epoxide hydrolase inhibitor

Kawasaki disease (KD) is the leading cause of acquired heart disease in pediatric patients in developed countries. Coronary artery aneurysms and myocardial infarction may occur if the disease remains untreated. An estimated 10-20% of KD patients do not respond to intravenous gamma globulin (IVIG), and thus, alternative treatments are currently being investigated. Epoxyeicosatrienoic acids (EETs) are natural anti-inflammatory factors and angiogenic mediators degraded by soluble epoxide hydrolase (sEH). sEH inhibitory factors have been demonstrated to stabilize EET levels, inhibit inflammation and promote vascular repair in vivo. The present study aimed to determine whether an increase in EET levels induced by treatment with the sEH inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA) promotes vascular repair in human coronary arterial endothelial cells (HCAECs) and reduces inflammation in a mouse model of KD induced by Lactobacillus casei cell wall extract. The effect of AUDA on vascular repair in HCAECs was assessed by using cell proliferation, migration, adhesion and tube formation assays, and the anti-inflammatory effect of AUDA in the mouse model of KD was determined by detecting the expression of matrix metalloproteinase (MMP)-9, tumor necrosis factor (TNF)-α and interleukin (IL)-1β at the protein level via ELISA. The results demonstrated that AUDA increased the proliferation, migration, adhesion and tube formation ability of HCAECs in a dose-dependent manner. Furthermore, in the mouse model of KD, AUDA reduced the protein expression of MMP-9, IL-1β and TNF-α, indicating that AUDA may alleviate inflammatory reactions in the coronary arteries of KD model mice. The present results also indicate that these effects may be exerted through the peroxisome proliferator activated receptor γ signaling pathway. Taken together, the present study supports the potential utility of AUDA in the treatment of KD.

Aetiological Significance of Infectious Stimuli in Kawasaki Disease

Kawasaki disease (KD) is a pediatric vasculitis syndrome that is often involves coronary artery lesions (e. g., coronary artery aneurysms). Although its causal factors and entire pathogenesis remain elusive, the available evidence indicates that the pathogenesis of KD is closely associated with dysregulation of immune responses to various viruses or microbes. In this short review, we address several essential aspects of the etiology of KD with respect to the immune response to infectious stimuli: 1) the role of viral infections, 2) the role of bacterial infections and the superantigen hypothesis, 3) involvement of innate immune response including pathogens/microbe-associated molecular patterns and complement pathways, and 4) the influence of genetic background on the response to infectious stimuli. Based on the clinical and experimental evidence, we discuss the possibility that a wide range of microbes and viruses could cause KD through common and distinct immune processes.

How Should We Classify Kawasaki Disease?

The exact classification of Kawasaki disease (KD) has been debated. Infectious disease specialists have claimed it as an infection with a classic immune responses to an as yet unidentified pathogen that localizes to the coronary arteries. Others have favored an autoreactive hypothesis that KD is triggered by an antigen that shares homology with structures in the vascular wall, and molecular mimicry resulting in an immune response directed to that tissue. Rheumatologists have classified it as a systemic vasculitis, while some immunologists have stressed the robust nature of the innate immune response that causes both systemic inflammation as well as damage to the coronary arterial wall and questioned whether KD falls within the spectrum of autoinflammatory diseases. This review will describe the evidences available up to now regarding these hypotheses.

The Epidemiology and Pathogenesis of Kawasaki Disease

Epidemiologic and clinical features of Kawasaki Disease (KD) strongly support an infectious etiology. KD is worldwide, most prominently in Japan, Korea, and Taiwan, reflecting increased genetic susceptibility among Asian populations. In Hawaii, KD rates are 20-fold higher in Japanese ethnics than in Caucasians, intermediate in other ethnicities. The age distribution of KD, highest in children < 2 yo, lower in those < 6 months, is compatible with infection by a ubiquitous agent resulting in increasing immunity with age and with transplacental immunity, as with some classic viruses. The primarily winter-spring KD seasonality and well-documented Japanese epidemics with wave-like spread also support an infectious trigger. We hypothesize KD pathogenesis involves an RNA virus that usually causes asymptomatic infection but KD in a subset of genetically predisposed children. CD8 T cells, oligoclonal IgA, and upregulation of cytotoxic T cell and interferon pathway genes in the coronaries in fatal KD also support a viral etiology. Cytoplasmic inclusion bodies in ciliated bronchial epithelium identified by monoclonal antibodies made from oligoclonal IgA heavy chains also supports a viral etiology. Recent availability of "second generation" antibodies from KD peripheral blood plasmablasts may identify a specific viral antigen. Thus, we propose an unidentified ("new") RNA virus infects bronchial epithelium usually causing asymptomatic infection but KD in a subset of genetically predisposed children. The agent persists in inclusion bodies, with intermittent respiratory shedding, entering the bloodstream via macrophages targeting coronaries. Antigen-specific IgA plasma cells and CD8 T cells respond but coronaries can be damaged. IVIG may include antibody against the agent. Post infection, 97-99% of KD patients are immune to the agent, protected against recurrence. The agent can spread either from those with asymptomatic primary infection in winter-spring or from a previously infected contact who intermittently sheds the agent.

Is Kawasaki disease an infectious disorder?

Although the etiology of Kawasaki disease (KD) is largely unknown, a large body of clinical, epidemiologic, immunologic, pathologic and ultrastructural evidence suggests that an infectious agent triggers a cascade that causes the illness. However, this elusive infectious agent remains unidentified at present. Increasingly sensitive molecular methods for identifying microbial nucleic acids and proteins in tissue samples continue to rapidly emerge, and these methods should be utilized in studies on KD etiology as they become available. Identifying the etiology of this enigmatic disease remains the single most important research goal in the field, and accomplishing this goal is the best means to improve diagnosis, treatment and prevention of this potentially fatal childhood disease.

Kawasaki disease and coronary artery aneurysms: from childhood to adulthood

Kawasaki disease is an acute, systemic vasculitis of childhood and confers a 25% risk of developing coronary artery aneurysms. Its etiology is unknown, but the incidence is increasing rapidly with linked gene polymorphisms having been identified. A constellation of symptoms, epidemics and seasonality all implicate an unidentified infective or environmental cause. Intravenous immunoglobulin therapy, aspirin and steroids all form the mainstay of acute treatment and reduces the incidence of coronary artery aneurysms if given before 7 days. However, in some, these lesions persist and require ongoing management during follow-up during childhood and into adult life. Evidence for further investigations in order to minimize complications is presented in order to minimize the myofibroblast proliferation and stenosis in the long term.

Arterial immune protein expression demonstrates the complexity of immune responses in Kawasaki disease arteritis

A more complete understanding of immune-mediated damage to the coronary arteries in children with Kawasaki disease (KD) is required for improvements in patient treatment and outcomes. We recently reported the transcriptional profile of KD coronary arteritis, and in this study sought to determine protein expression of transcriptionally up-regulated immune genes in KD coronary arteries from the first 2 months after disease onset. We examined the coronary arteries of 12 fatal KD cases and 13 childhood controls for expression of a set of proteins whose genes were highly up-regulated in the KD coronary artery transcriptome: allograft inflammatory factor 1 (AIF1), interleukin 18 (IL-18), CD74, CD1c, CD20 (MS4A1), Toll-like receptor 7 (TLR-7) and Z-DNA binding protein 1 (ZBP1). Immunohistochemistry and immunofluorescence studies were performed to evaluate protein expression and co-localization, respectively. AIF1 was expressed transmurally in KD arteritis and localized to macrophages and myeloid dendritic cells. CD74, which interacts with major histocompatibility complex (MHC) class II on antigen-presenting cells, localized to the intima-media. CD1c, a marker of myeloid dendritic cells, was expressed in a transmural pattern, as were IL-18 and CD20. ZBP1 and TLR-7 were up-regulated compared to controls, but less highly compared to the other proteins. These findings provide evidence of antigen presentation and interferon response in KD arteritis. In combination with prior studies demonstrating T lymphocyte activation, these results demonstrate the complexity of the KD arterial immune response.

Observational study of Interleukin-21 (IL-21) does not distinguish Kawasaki disease from other causes of fever in children

BACKGROUND

Kawasaki disease (KD) is a febrile childhood vasculitis of unknown etiology. The diagnosis is highly concerning as over a quarter of children who fail to receive timely treatment with intravenous immunoglobulin (IVIG) will develop coronary aneurysms. Diagnosis relies on proper symptomatology and is supported by non-specific markers of inflammation. Previous studies have identified elevated plasma levels of interleukin-21 (IL-21) as a sensitive and specific biomarker in KD. The aim of this study is to assess the validity of IL-21 as a diagnostic biomarker for KD in febrile children in North America.

METHODS

Plasma samples were collected from children who presented to an urban Emergency Department in North America. IL-21 levels were measured using commercial ELISA kits in 12 KD versus 60 controls subjects.

RESULTS

Our study shows that IL-21 levels were non-specifically elevated across all febrile children, irrespective of KD diagnosis. Length of fever prior to sample collection does not correlate with IL-21 levels. Other inflammatory markers and laboratory values were also compared to IL-21 and show no significant correlation.

CONCLUSIONS

Since IL-21 is elevated non-specifically in this cohort, our data supports that IL-21 is not an appropriate biomarker for diagnosis of KD in North American pediatric populations.

Factors affecting N-terminal pro-brain natriuretic peptide elevation in the acute phase of Kawasaki disease

BACKGROUND

The aim of this study was to investigate the clinical significance and factors that affect N-terminal pro-brain natriuretic peptide (NT-proBNP) elevation in the acute phase of Kawasaki disease (KD) despite the absence of apparent cardiac complications.

METHODS

The laboratory and echocardiography results of 44 KD patients in the acute and subacute phases were reviewed.

RESULTS

With preserved cardiac function, median NT-proBNP was significantly elevated in the acute phase compared with the subacute phase (343 pg/mL, IQR, 162-1182 pg/mL vs 98 pg/mL, IQR, 61-205 pg/mL, respectively; P < 0.0001). The respective levels of tumor necrosis factor (TNF)-α, soluble TNF receptor (sTNFR)1, and sTNFR2 were also significantly elevated in the acute phase compared with the subacute phase: TNF-α, 3.3 pg/mL (IQR, 2.6-4.8 pg/mL) versus 2.4 pg/mL (IQR 1.9-4.0 pg/mL; P < 0.01), sTNFR1, 2741 pg/mL (IQR, 2080-3183 pg/mL) versus 976 pg/mL (IQR, 814-1247 pg/mL; P < 0.0001), sTNFR2, 5644 pg/mL (IQR, 4693-7520 pg/mL) versus 3169 pg/mL (IQR, 2132-3878 pg/mL; P < 0.0001). Log-transformed NT-proBNP was correlated with TNF-α (r = 0.29, P = 0.056), sTNFR1 (r = 0.60, P < 0.0001), and sTNFR2 (r = 0.65, P < 0.0001). TNF-α was correlated with sTNFR1 (r = 0.35, P = 0.02) and sTNFR2 (r = 0.51, P < 0.001).

CONCLUSION

Tumor necrosis factor-α may cause NT-proBNP elevation in the acute phase of KD, and NT-proBNP level may be an indicator of TNF-α activity.

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.

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.

Kawasaki disease: insights into pathogenesis and approaches to treatment

This Review summarizes recent advances in understanding of the pathologic processes and pathophysiologic mechanisms leading to coronary arteritis in Kawasaki disease, and describes current approaches to its treatment. Kawasaki disease is the most common cause of acquired heart disease among children in developed countries, in whom the resulting coronary artery abnormalities can cause myocardial ischaemia, infarction and even death. Epidemiologic data strongly suggest an infectious aetiology, although the causative agent has yet to be identified. Genetic factors also increase susceptibility to Kawasaki disease, as indicated by its strikingly high incidence rate in children of Asian ethnicity and by an increased incidence in first-degree family members. The treatment of Kawasaki disease is based on timely administration of intravenous immunoglobulin and aspirin. However, the management of patients who do not respond to this standard therapy remains challenging; although several options are available, comparative data on which to base treatment decisions are scarce. The added value of adjunctive therapy with corticosteroids in patients at particularly high risk of coronary complications has been demonstrated in Japanese populations, but identification of high-risk patients has proven to be difficult in ethnically diverse populations.

Update on Kawasaki disease: epidemiology, aetiology and pathogenesis

Kawasaki disease is an acute systemic vasculitis predominantly affecting young children. It is due to an abnormal host response to as yet unidentified infectious trigger(s). Kawasaki disease may cause coronary artery damage, long-term cardiovascular morbidity and occasionally mortality, especially if the diagnosis is missed or timely treatment is not given. This is the first of two updates on Kawasaki disease. Here we review recent advances in epidemiology, possible aetiologies, host susceptibility and pathogenesis of this fascinating condition.

Can a systems biology approach unlock the mysteries of Kawasaki disease?

Kawasaki disease (KD) is a systemic inflammatory illness of childhood that particularly affects the coronary arteries. It can lead to coronary artery aneurysms, myocardial infarction, and sudden death. Clinical and epidemiologic data support an infectious cause, and the etiology remains unknown, but recent data support infection with a 'new' virus. Genetic factors influence KD susceptibility; the incidence is 10-fold higher in children of Asian when compared with Caucasian ethnicity. Recent research has identified genes affecting immune response that are associated with KD susceptibility and outcome. A re-examination of the pathologic features of KD has yielded a three process model of KD vasculopathy, providing a framework for understanding the KD arterial immune response and the damage it inflicts and for identifying new therapeutic targets for KD patients with coronary artery abnormalities. The researcher is faced with many challenges in determining the pathogenesis of KD. A systems biology approach incorporating genomics, proteomics, transcriptomics, and microbial bioinformatics analysis of high-throughput sequence data from KD tissues could provide the keys to unlocking the mysteries of this potentially fatal illness of childhood.

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.

Recent advances in the understanding and management of kawasaki disease

Kawasaki disease (KD) is an acute systemic inflammatory illness of childhood that can result in coronary artery aneurysms, myocardial infarction, and sudden death. Clinical and epidemiologic data point to an unknown infectious agent as the cause. We discovered that an oligoclonal IgA immune response is present in arterial tissue in acute KD. Synthetic versions of prevalent IgA antibodies in the KD arterial wall identify cytoplasmic inclusion bodies in acute KD ciliated bronchial epithelium and other inflamed KD tissues. Light and electron microscopic studies show that the inclusion bodies are consistent with aggregates of viral protein and RNA, and are likely formed by the KD etiologic agent. KD susceptibility is likely to be polygenic. Treatment of gammaglobulin nonresponders usually consists of additional intravenous immunoglobulin, methylprednisolone, and/or infliximab. Additional data regarding KD pathogenesis are urgently needed to provide other targets for therapy for those patients at highest risk of developing coronary artery abnormalities.

Kawasaki disease: novel insights into etiology and genetic susceptibility

Kawasaki disease (KD) is a vasculitis of young childhood that particularly affects the coronary arteries. Molecular analysis of the oligoclonal IgA response in acute KD led to production of synthetic KD antibodies. These antibodies identify intracytoplasmic inclusion bodies in acute KD tissues. Light and electron microscopic studies indicate that the inclusion bodies are consistent with aggregates of viral proteins and RNA. Advances in molecular genetic analysis and completion of the Human Genome Project have sparked a worldwide effort to identify genes associated with KD. A polymorphism of one such gene, ITPKC, a negative regulator of T cell activation, confers susceptibility to KD in Japanese populations and increases the risk of developing coronary artery abnormalities in both Japanese and U.S. children. Identification of the etiologic agent and of genes conferring KD susceptibility are the best means of improving diagnosis and therapy and enabling prevention of this important disorder of childhood.

Ultrastructural, immunofluorescence, and RNA evidence support the hypothesis of a "new" virus associated with Kawasaki disease

BACKGROUND

Intracytoplasmic inclusion bodies (ICI) have been identified in ciliated bronchial epithelium of Kawasaki disease (KD) patients using a synthetic antibody derived from acute KD arterial IgA plasma cells; ICI may derive from the KD etiologic agent.

METHODS

Acute KD bronchial epithelium was subjected to immunofluorescence for ICI and cytokeratin, high-throughput sequencing, and transmission electron microscopy (TEM). Interferon pathway gene expression profiling was performed on KD lung.

RESULTS

An intermediate filament cytokeratin "cage" was not observed around KD ICI, making it unlikely that ICI are overproduced or misfolded human protein aggregates. Many interferon-stimulated genes were detected in the bronchial epithelium, and significant modulation of the interferon response pathway was observed in the lung tissue of KD patients. No known virus was identified by sequencing. Aggregates of virus-like particles (VLP) were detected by TEM in all 3 acute KD patients from whom nonembedded formalin-fixed lung tissue was available.

CONCLUSIONS

KD ICI are most likely virus induced; bronchial cells with ICI contain VLP that share morphologic features among several different RNA viral families. Expedited autopsies and tissue fixation from acute KD fatalities are urgently needed to more clearly ascertain the VLP. These findings are compatible with the hypothesis that the infectious etiologic agent of KD may be a "new" RNA virus.

Pathogenesis and management of Kawasaki disease

Kawasaki disease (KD) is an acute systemic inflammatory illness of young children that can result in coronary artery aneurysms, myocardial infarction and sudden death in previously healthy children. Clinical and epidemiologic features support an infectious cause, but the etiology remains unknown four decades after KD was first identified by Tomisaku Kawasaki. Finding the cause of KD is a pediatric research priority. We review the unique immunopathology of KD and describe the current treatment. New research has led to identification of viral-like cytoplasmic inclusion bodies in acute KD tissues; this finding could lead to identification of the elusive etiologic agent and result in significant advances in KD diagnosis and treatment. Current management of acute KD is based upon prospective, multicenter treatment trials of intravenous immunoglobulin (IVIG) with high-dose aspirin. Optimal therapy is 2 g/kg IVIG with high-dose aspirin as soon as possible after diagnosis during the acute febrile phase of illness, followed by low-dose aspirin until follow-up echocardiograms indicate a lack of coronary abnormalities. The addition of one dose of intravenous pulse steroid has not been shown to be beneficial. For the 10-15% of patients with refractory KD, few controlled data are available. Options include repeat IVIG (our preference), a 3-day course of intravenous pulse methylprednisolone, or infliximab (Remicade). Patients with mild-to-moderate coronary abnormalities should receive an antiplatelet agent such as low-dose aspirin (3-5 mg/kg/day) or clopidogrel (1 mg/kg/day up to 75 mg), and those with giant (approximately 8 mm diameter) or multiple coronary aneurysms should receive an antiplatelet agent with an anticoagulant such as warfarin or low-molecular-weight heparin. Acute coronary obstruction requires acute thrombolytic therapy with a surgical or percutaneous interventional procedure.

Virus-induced vasculitis

There is a growing understanding of the different syndromes that have a definite, and in some cases a possible, association with viral infections. Hepatitis C virus-associated mixed cryoglobulinemias and hepatitis B virus-associated polyarteritis nodosa are examples of a vasculitis with a definite viral association. However, various types of cutaneous vasculitis are examples of a vasculitis with only a possible association with a viral infection.

Lung parenchymal consolidation as an uncommon presentation and cause of delayed diagnosis in atypical Kawasaki syndrome

We report three patients who initially showed prolonged fever, lung parenchymal consolidation and laboratory findings of pneumonia, and secondarily presented a clinical picture ascribed to Kawasaki syndrome. Two of these children developed coronary artery dilations, which regressed upon echocardiography after 12 months. In the case of infants showing broncho-pulmonary abnormalities with slow resolution, active inflammatory parameters and high fever persistence, pediatricians should consider atypical Kawasaki syndrome as a possible alternative diagnosis.

Searching for the cause of Kawasaki disease--cytoplasmic inclusion bodies provide new insight

Although Kawasaki disease (KD) is the most common cause of acquired heart disease in children in the developed world, its aetiology remains unknown. In this Opinion, Anne Rowley and colleagues discuss evidence, including recently identified cytoplasmic inclusion bodies, which suggests that KD is caused by an infectious agent.

Kawasaki disease (KD) has emerged as the most common cause of acquired heart disease in children in the developed world. The cause of KD remains unknown, although an as-yet unidentified infectious agent might be responsible. By determining the causative agent, we can improve diagnosis, therapy and prevention of KD. Recently, identification of an antigen-driven IgA response that was directed at cytoplasmic inclusion bodies in KD tissues has provided new insights that could unlock the mysteries of KD.

RNA-containing cytoplasmic inclusion bodies in ciliated bronchial epithelium months to years after acute Kawasaki disease

Background

Kawasaki Disease (KD) is the most common cause of acquired heart disease in children in developed nations. The KD etiologic agent is unknown but likely to be a ubiquitous microbe that usually causes asymptomatic childhood infection, resulting in KD only in genetically susceptible individuals. KD synthetic antibodies made from prevalent IgA gene sequences in KD arterial tissue detect intracytoplasmic inclusion bodies (ICI) resembling viral ICI in acute KD but not control infant ciliated bronchial epithelium. The prevalence of ICI in late-stage KD fatalities and in older individuals with non-KD illness should be low, unless persistent infection is common.

Methods and Principal Findings

Lung tissue from late-stage KD fatalities and non-infant controls was examined by light microscopy for the presence of ICI. Nucleic acid stains and transmission electron microscopy (TEM) were performed on tissues that were strongly positive for ICI. ICI were present in ciliated bronchial epithelium in 6/7 (86%) late-stage KD fatalities and 7/27 (26%) controls ages 9–84 years (p = 0.01). Nucleic acid stains revealed RNA but not DNA within the ICI. ICI were also identified in lung macrophages in some KD cases. TEM of bronchial epithelium and macrophages from KD cases revealed finely granular homogeneous ICI.

Significance

These findings are consistent with a previously unidentified, ubiquitous RNA virus that forms ICI and can result in persistent infection in bronchial epithelium and macrophages as the etiologic agent of KD.

Kawasaki Disease

Kawasaki disease (KD) is an acute inflammatory vasculitis of childhood which was initially described more than 4 decades ago, yet the specific etiology remains unknown. It has become the most common cause of acquired cardiovascular disease in children in the United States. Advances in clinical therapies have reduced, but not eliminated, the incidence of coronary artery abnormalities in affected children. Pathophysiology seems to include an intense elaboration of cytokines, endothelin, and other vasoactive mediators resulting in the development of vascular endothelial changes that may leave a permanent impact on vascular integrity. Treatment with intravenous immune globulin and aspirin remains the primary management strategy and steroid therapy remains contoversial. In severe circumstances, coronary reperfusion strategies are required, and coronary artery surgery in children with KD has been required, albeit infrequently. KD may be a harbinger for early onset coronary artery disease in adults. Recently developed AHA recommendations have amended diagnostic strategies and indicated a stratified approach to the long-term follow up of this enigmatic yet widespread disease.

New developments in the search for the etiologic agent of Kawasaki disease

PURPOSE OF REVIEW

The aim of this article is to review recent developments in the search for the etiologic agent of Kawasaki disease.

RECENT FINDINGS

Two recently proposed theories of Kawasaki disease etiology, the toxic shock syndrome toxin-1 hypothesis and the coronavirus NL-63 hypothesis, have been studied extensively and have been disproven. Surprisingly, IgA plasma cells infiltrate inflamed tissues in acute Kawasaki disease, including the coronary artery, and are oligoclonal, or antigen-driven. Synthetic versions of predominant IgA antibodies in acute Kawasaki disease arterial tissue bind to an antigen present in acute Kawasaki disease ciliated bronchial epithelium and in a subset of macrophages in acute inflamed Kawasaki disease tissues. Light and electron microscopic studies of the antigen in acute Kawasaki disease ciliated bronchial epithelium indicate that the Kawasaki disease-associated antigen localizes to cytoplasmic inclusion bodies that are consistent with aggregates of viral protein and associated nucleic acid.

SUMMARY

The identification of cytoplasmic inclusion bodies in acute Kawasaki disease ciliated bronchial epithelium has provided direction for future Kawasaki disease etiology studies. Transmission electron microscopic examination of glutaraldehyde-fixed medium-sized bronchi from acute Kawasaki disease fatalities and analysis of the protein and nucleic acid components of the inclusions should provide important information about these inclusion bodies and speed the identification of the specific etiologic agent of Kawasaki disease.