Characterization of circulating immune cells in acute Kawasaki disease suggests exposure to different antigens

The etiologies of Kawasaki disease

Kawasaki disease (KD) is a systemic vasculitis that affects young children and can result in coronary artery aneurysms. The etiology is currently unknown, but new clues from the epidemiology of KD in Japan, the country of highest incidence, are beginning to shed light on what may trigger this acute inflammatory condition. Additional clues from the global changes in KD incidence during the COVID-19 pandemic, coupled with a new birth cohort study from Japan, point to the potential role of person-to-person transmission of an infectious agent. However, the rising incidence of KD in Japan, with coherent waves across the entire country, points to an increasing intensity of exposure that cannot be explained by person-to-person spread. This Review discusses new and historical observations that guide us toward a better understanding of KD etiology and explores hypotheses and interpretations that can provide direction for future investigations. Once the etiology of KD is determined, accurate diagnostic tests will become available, and new, less expensive, and more effective targeted therapies will likely be possible. Clearly, solving the mystery of the etiologies of KD remains a priority for pediatric research.

[Predictive value of peripheral blood lymphocyte subsets for children with intravenous immunoglobulin-resistant Kawasaki disease]

OBJECTIVES

Based on peripheral blood lymphocyte subsets and common laboratory test indexes, this study aimed to construct a predictive scoring system for intravenous immunoglobulin (IVIG)-resistant Kawasaki disease (KD).

METHODS

Children hospitalized in Tianjin Children's Hospital from January 2021 to March 2023 were included in the study (185 cases of IVIG-sensitive KD and 41 cases of IVIG -resistant KD). Forty-six healthy children matched for age and gender were selected as controls. The relative percentage and absolute counts of peripheral lymphocyte subsets were measured by flow cytometry. Multivariate logistic regression was used to identify the predictive factors for IVIG-resistant KD and to construct a predictive scoring system for predicting IVIG-resistant KD.

RESULTS

The multivariate logistic regression analysis showed that CD4+ T cell absolute count, natural killer cell absolute count, serum sodium level, globulin level, and total bilirubin level were identified as predictive factors for IVIG-resistant KD (P<0.05). The predictive scoring system based on these factors achieved a sensitivity of 70.7% and a specificity of 83.8% in predicting IVIG-resistant KD.

CONCLUSIONS

Peripheral blood lymphocyte subsets can serve as predictive indicators for IVIG-resistant KD in children. The introduction of this indicator and the establishment of a scoring system based on it can provide a higher accuracy in predicting IVIG-resistant KD in children.

Identification of Hub Biomarkers and Immune and Inflammation Pathways Contributing to Kawasaki Disease Progression with RT-qPCR Verification

Background. Kawasaki disease (KD) is characterized by a disordered inflammation response of unknown etiology. Immune cells are closely associated with its onset, although the immune-related genes’ expression and possibly involved immune regulatory mechanisms are little known. This study aims to identify KD-implicated significant immune- and inflammation-related biomarkers and pathways and their association with immune cell infiltration. Patients and Methods. Gene microarray data were collected from the Gene Expression Omnibus database. Differential expression analysis, weighted gene coexpression network analysis (WGCNA), least absolute shrinkage and selection operator (LASSO) regression, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and gene set enrichment analysis (GSEA) were used to find KD hub markers. GSEA was used to assess the infiltration by 28 immune cell types and their connections to essential gene markers. Receiver operating characteristic (ROC) curves were used to examine hub markers’ diagnostic effectiveness. Finally, hub genes’ expressions were validated in Chinese KD patients by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Results. One hundred and fifty-one unique genes were found. Among 10 coexpression modules at WGCNA, one hub module exhibited the strongest association with KD. Thirty-six overlapping genes were identified. Six hub genes were potential biomarkers according to LASSO analysis. Immune infiltration revealed connections among activated and effector memory CD4+ T cells, neutrophils, activated dendritic cells, and macrophages. The six hub genes’ diagnostic value was shown by ROC curve analysis. Hub genes were enriched in immunological and inflammatory pathways. RT-qPCR verification results of FCGR1B ( $P<0.001$ ), GPR84 ( $P<0.001$ ), KREMEN1 ( $P<0.001$ ), LRG1 ( $P<0.001$ ), and TDRD9 ( $P<0.001$ ) upregulated expression in Chinese KD patients are consistent with our database analysis. Conclusion. Neutrophils, macrophages, and activated dendritic cells are strongly linked to KD pathophysiology. Through immune-related signaling pathways, hub genes such as FCGR1B, GPR84, KREMEN1, LRG1, and TDRD9 may be implicated in KD advancement.

Intravenous immunoglobulin induces IgG internalization by tolerogenic myeloid dendritic cells that secrete IL-10 and expand Fc-specific regulatory T cells

Intravenous immunoglobulin (IVIG) is used as an immunomodulatory agent in many inflammatory conditions including Multisystem Inflammatory Syndrome-Children (MIS-C) and Kawasaki disease (KD). However, the exact mechanisms underlying its anti-inflammatory action are incompletely characterized. Here, we show that in KD, a pediatric acute vasculitis that affects the coronary arteries, IVIG induces a repertoire of natural Treg that recognize immunodominant peptides in the Fc heavy chain constant region. To address which antigen-presenting cell (APC) populations present Fc peptides to Treg, we studied the uptake of IgG by innate cells in subacute KD patients 2 weeks after IVIG and in children 1.6–14 years after KD. Healthy adults served as controls. IgG at high concentrations was internalized predominantly by two myeloid dendritic cell (DC) lineages, CD14⁺ cDC2 and ILT-4⁺ CD4⁺ tmDC mostly through Fcγ receptor (R) II and to a lesser extent FcγRIII. Following IgG internalization, these two DC lineages secreted IL-10 and presented processed Fc peptides to Treg. The validation of IVIG function in expanding Fc-specific Treg presented by CD14⁺ cDC2 and ILT-4⁺ CD4⁺ tmDC was addressed in a small cohort of patients with MIS-C. Taken together, these results suggest a novel immune regulatory function of IgG in activating tolerogenic innate cells and expanding Treg, which reveals an important anti-inflammatory mechanism of action of IVIG.

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.

Characterization of SARS-CoV-2 and common cold coronavirus-specific T-cell responses in MIS-C and Kawasaki disease children

The immunopathogenesis of multisystem inflammatory syndrome (MIS-C) in children that may follow exposure to SARS-CoV-2 is incompletely understood. Here, we studied SARS-CoV-2-specific T cells in MIS-C, Kawasaki disease (KD), and SARS-CoV-2 convalescent controls using peptide pools derived from SARS-CoV-2 spike or nonspike proteins, and common cold coronaviruses (CCC). Coordinated CD4+ and CD8+ SARS-CoV-2-specific T cells were detected in five MIS-C subjects with cross-reactivity to CCC. CD4+ and CD8+ T-cell responses alone were documented in three and one subjects, respectively. T-cell specificities in MIS-C did not correlate with disease severity and were similar to SARS-CoV-2 convalescent controls. T-cell memory and cross-reactivity to CCC in MIS-C and SARS-CoV-2 convalescent controls were also similar. The chemokine receptor CCR6, but not CCR9, was highly expressed on SARS-CoV-2-specific CD4+ but not on CD8+ T cells. Only two of 10 KD subjects showed a T-cell response to CCC. Enumeration of myeloid APCs revealed low cell precursors in MIS-C subjects compared to KD. In summary, children with MIS-C mount a normal T-cell response to SARS-CoV-2 with no apparent relationship to antecedent CCC exposure. Low numbers of tolerogenic myeloid DCs may impair their anti-inflammatory response.

Immune profile of children diagnosed with multisystem inflammatory syndrome associated with SARS-CoV-2 infection (MIS-C)

Introduction

The pathophysiology of multisystem inflammatory syndrome associated with SARS-CoV-2 infection (MIS-C) remains poorly understood. This study aimed to define peripheral blood immune features in patients with MIS-C.

Material and methods

We analyzed seven children diagnosed with MIS-C between April 1 and May 15, 2021, in St. Joseph's Children's Hospital in Poznan (Poland).

Results

All patients had elevated inflammatory markers, IgG antibodies against SARS-CoV-2, and lymphopenia with a marked decrease in CD4+ and CD8+ T cells. The majority of CD4+ T cells were naive cells. Almost all (6/7) of the analyzed patients had a higher CD4+/CD8+ T cell ratio than average values. B cells were within the normal range - the majority were non-memory cells.

Conclusions

Children with MIS-C do not resemble adults during COVID-19 recovery. The immune profile of the studied patients differs from that of children with Kawasaki disease (KD), but it is similar to that of adults with severe COVID-19. The proposed explanation is a profound lymphopenia caused by SARS-CoV-2 infection - which persists for weeks - as a result leading to uncontrolled inflammation. In COVID-19 patients the T cell level returns to normal after the second week of the disease. Our data suggest that in children prolonged lymphopenia after COVID-19 can be a practical marker for possible MIS-C alert. If there is a continuum from lymphopenia to MIS-C, there is room for screening and prevention. Further studies are needed to determine whether steroid treatment introduced in a child with prolonged lymphopenia could stop the inflammatory process.

Atlas of circulating immune cells in Kawasaki disease

Increasing evidence shows that the pathogenesis of Kawasaki disease (KD) is caused by abnormal and unbalanced innate and adaptive immune responses. However, the changes in and functions of adaptive immune cells in the peripheral blood of subjects with KD remain controversial. In this study, three different methods, CIBERSORT, Immune Cell Abundance Identifier (ImmuCellAI), and immune cell markers, were used to evaluate the proportions and abundances of immune cells in eight KD datasets (GSE9863, GSE9864, GSE18606, GSE63881, GSE68004, GSE73461, GSE73463, and GSE64486; a total of 1,251 samples). Compared with those in normal controls and convalescent KD samples, the proportions and abundances of innate immune cells such as neutrophils, monocytes, and macrophages in acute KD peripheral blood samples were significantly increased, while those of adaptive immune cells such as B and T cells were significantly decreased. The change tendencies of these immune cells were similar to those observed in other febrile illnesses but were more significant. However, in the coronary artery tissues of patients with convalescent KD, adaptive immune cells, especially B cells and CD8+ T cell subsets, were significantly increased. This result suggests that adaptive immune cells can be selectively recruited from peripheral blood into the coronary arteries. In addition, we found that elevated neutrophils in peripheral blood could be used as a biomarker to assist in the differential diagnosis of KD, but we did not find immune cells that could accurately predict intravenousimmunoglobulin (IVIG) responses in multiple datasets.

Circulating Immune Cell Profile and Changes in Intravenous Immunoglobulin Responsiveness Over the Disease Course in Children With Kawasaki Disease

Kawasaki disease (KD) is an acute, self-limited febrile illness of young children. The etiology of KD remains to be poorly understood. There has been limited research on longitudinal examination of peripheral blood leukocytes for immune profiling particularly in relation to treatment response with intravenous immunoglobulin (IVIG). This study profiles immune cells at the time of diagnosis and over the disease course. In addition, we identified the characteristics of the immune cells in IVIG-responsive patients with KD. We enrolled patients diagnosed with KD between May 1, 2017, and January 1, 2020. Blood was taken at least three times from all enrolled patients: at diagnosis (before IVIG infusion) and immediately and 2 weeks after IVIG infusion. We evaluated the laboratory findings and results of flow cytometry analysis of immune cells at all stages, focusing on CD4⁺ T lymphocytes, CD8⁺ T lymphocytes, CD19⁺ B lymphocytes, granulocytes, classical monocytes, and natural killer (NK) cells. Non-febrile healthy controls (NFCs) and other febrile controls (OFCs) were also enrolled. A total of 68 patients were enrolled and divided into two groups according to IVIG resistance status: IVIG-responsive (n = 55) and IVIG-resistant (n = 13). The total fever duration was significantly longer in the IVIG-resistant group (9.7 ± 5.3 days) than in the IVIG-responsive group (6.7 ± 3.0 days; P = 0.02). There was a significant difference in intermediate CD14⁺CD16⁺ monocytes between KD patients and both NFC and OFCs; they were significantly higher and lower in KD patients than NFC and OFCs, respectively (P < 0.001). The levels of all three subtypes of NK cells were significantly lower in KD patients than in both NFC and OFCs (P < 0.001). Regarding IVIG responsiveness, CD14⁺CD16⁺ intermediate monocyte levels were significantly lower in the IVIG-resistant group (P < 0.001). In addition, CD56^-CD16⁺ NK cell expression was significantly lower in the IVIG-resistant group than in the IVIG-responsive group (P = 0.002). In conclusion, our results suggest CD56^-CD16⁺N NK cells and CD14⁺CD16⁺ intermediate monocytes might play an essential role in immunopathogenesis of KD. Further studies are warranted to explore the role of these subpopulations particularly for the observed association with coronary artery lesions (CAL) and treatment response.

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.