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Kawasaki disease (KD) is the leading cause of acquired heart disease among children. Murine and human data suggest that the NLRP3-IL-1β pathway is the main driver of KD pathophysiology. NLRP3 can be activated during defective autophagy/mitophagy. We used the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis to examine the role of autophagy/mitophagy on cardiovascular lesion development. LCWE-injected mice had impaired autophagy/mitophagy and increased levels of ROS in cardiovascular lesions, together with increased systemic 8-OHdG release. Enhanced autophagic flux significantly reduced cardiovascular lesions in LCWE-injected mice, whereas autophagy blockade increased inflammation. Vascular smooth muscle cell-specific deletion of Atg16l1 and global Parkin-/- significantly increased disease formation, supporting the importance of autophagy/mitophagy in this model. Ogg1-/- mice had significantly increased lesions with increased NLRP3 activity, whereas treatment with MitoQ reduced vascular tissue inflammation, ROS production, and systemic 8-OHdG release. Treatment with MN58b or Metformin (increasing AMPK and reducing ROS) resulted in decreased cardiovascular lesions. Our results demonstrate that impaired autophagy/mitophagy and ROS-dependent damage exacerbate the development of murine KD vasculitis. This pathway can be efficiently targeted to reduce disease severity. These findings enhance our understanding of KD pathogenesis and identify potentially novel therapeutic avenues for KD treatment.

We recently discovered a superantigen-like motif sequentially and structurally similar to a staphylococcal enterotoxin B (SEB) segment, near the S1/S2 cleavage site of the SARS-CoV-2 spike protein, which might explain the multisystem inflammatory syndrome (MIS-C) observed in children and the cytokine storm in severe COVID-19 patients. We show here that an anti-SEB monoclonal antibody (mAb), 6D3, can bind this viral motif at its polybasic (PRRA) insert to inhibit infection in live virus assays. The overlap between the superantigenic site of the spike and its proteolytic cleavage site suggests that the mAb prevents viral entry by interfering with the proteolytic activity of cell proteases (furin and TMPRSS2). The high affinity of 6D3 for this site originates from a polyacidic segment at its heavy chain CDR2. The study points to the potential utility of 6D3 for possibly treating COVID-19, MIS-C, or common colds caused by human coronaviruses that also possess a furin-like cleavage site.

Multisystem Inflammatory Syndrome in Children (MIS-C) associated with COVID-19 is a newly recognized condition in children with recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. These children and adult patients with severe hyperinflammation present with a constellation of symptoms that strongly resemble toxic shock syndrome, an escalation of the cytotoxic adaptive immune response triggered upon the binding of pathogenic superantigens to T cell receptors (TCRs) and/or major histocompatibility complex class II (MHCII) molecules. Here, using structure-based computational models, we demonstrate that the SARS-CoV-2 spike (S) glycoprotein exhibits a high-affinity motif for binding TCRs, and may form a ternary complex with MHCII. The binding epitope on S harbors a sequence motif unique to SARS-CoV-2 (not present in other SARS-related coronaviruses), which is highly similar in both sequence and structure to the bacterial superantigen staphylococcal enterotoxin B. This interaction between the virus and human T cells could be strengthened by a rare mutation (D839Y/N/E) from a European strain of SARS-CoV-2. Furthermore, the interfacial region includes selected residues from an intercellular adhesion molecule (ICAM)-like motif shared between the SARS viruses from the 2003 and 2019 pandemics. A neurotoxin-like sequence motif on the receptor-binding domain also exhibits a high tendency to bind TCRs. Analysis of the TCR repertoire in adult COVID-19 patients demonstrates that those with severe hyperinflammatory disease exhibit TCR skewing consistent with superantigen activation. These data suggest that SARS-CoV-2 S may act as a superantigen to trigger the development of MIS-C as well as cytokine storm in adult COVID-19 patients, with important implications for the development of therapeutic approaches.

In men, the incidence of melanoma rises rapidly after age 50, and nearly two thirds of melanoma deaths are male. The immune system is known to play a key role in controlling the growth and spread of malignancies, but whether age- and sex-dependent changes in immune cell function account for this effect remains unknown. Here, we show that in castrated male mice, neutrophil maturation and function are impaired, leading to elevated metastatic burden in two models of melanoma. Replacement of testosterone effectively normalized the tumor burden in castrated male mice. Further, the aberrant neutrophil phenotype was also observed in prostate cancer patients receiving androgen deprivation therapy, highlighting the evolutionary conservation and clinical relevance of the phenotype. Taken together, these results provide a better understanding of the role of androgen signaling in neutrophil function and the impact of this biology on immune control of malignancies.

Autophagy can either antagonize or promote intracellular bacterial growth, depending on the pathogen. Here, we investigated the role of autophagy during a pulmonary infection with the obligate intracellular pathogen, Chlamydia pneumoniae (CP). In mouse embryonic fibroblasts (MEFs) or macrophages, deficiency of autophagy pathway components led to enhanced CP replication, suggesting that autophagy exerts a bactericidal role. However, in vivo, mice with myeloid-specific deletion of the autophagic protein ATG16L1 suffered increased mortality during CP infection, neutrophilia, and increased inflammasome activation despite no change in bacterial burden. Induction of autophagy led to reduced CP replication in vitro, but impaired survival in CP-infected mice, associated with an initial reduction in IL-1β production, followed by enhanced neutrophil recruitment, defective CP clearance, and later inflammasome activation and IL-1β production, which drove the resulting mortality. Taken together, our data suggest that a delicate interplay exists between autophagy and inflammasome activation in determining the outcome of CP infection, perturbation of which can result in inflammatory pathology or unrestricted bacterial growth.

Receptor interacting protein 2 (RIP2) plays a role in sensing intracellular pathogens, but its function in T cells is unclear. We show that RIP2 deficiency in CD4+ T cells resulted in chronic and severe interleukin-17A-mediated inflammation during Chlamydia pneumoniae lung infection, increased T helper 17 (Th17) cell formation in lungs of infected mice, accelerated atherosclerosis, and more severe experimental autoimmune encephalomyelitis. While RIP2 deficiency resulted in reduced conventional Th17 cell differentiation, it led to significantly enhanced differentiation of pathogenic (p)Th17 cells, which was dependent on RORα transcription factor and interleukin-1 but independent of nucleotide oligomerization domain (NOD) 1 and 2. Overexpression of RIP2 resulted in suppression of pTh17 cell differentiation, an effect mediated by its CARD domain, and phenocopied by a cell-permeable RIP2 CARD peptide. Our data suggest that RIP2 has a T cell-intrinsic role in determining the balance between homeostatic and pathogenic Th17 cell responses.

Pathogen burden accelerates atherosclerosis, but the mechanisms remain unresolved. Activation of the NLRP3 inflammasome is linked to atherogenesis. Here we investigated whether Chlamydia pneumoniae (C.pn) infection engages NLRP3 in promoting atherosclerosis. C.pn potentiated hyperlipidemia-induced inflammasome activity in cultured macrophages and in foam cells in atherosclerotic lesions of Ldlr-/- mice. C.pn-induced acceleration of atherosclerosis was significantly dependent on NLRP3 and caspase-1. We discovered that C.pn-induced extracellular IL-1β triggers a negative feedback loop to inhibit GPR109a and ABCA1 expression and cholesterol efflux, leading to accumulation of intracellular cholesterol and foam cell formation. Gpr109a and Abca1 were both upregulated in plaque lesions in Nlrp3-/- mice in both hyperlipidemic and C.pn infection models. Mature IL-1β and cholesterol may compete for access to the ABCA1 transporter to be exported from macrophages. C.pn exploits this metabolic-immune crosstalk, which can be modulated by NLRP3 inhibitors to alleviate atherosclerosis.

Background: Kawasaki disease (KD), an acute febrile illness and systemic vasculitis, is the leading cause of acquired heart disease in children in industrialized countries. KD leads to the development of coronary artery aneurysms (CAA) in affected children, which may persist for months and even years after the acute phase of the disease. There is an unmet need to characterize the immune and pathological mechanisms of the long-term complications of KD. Methods: We examined cardiovascular complications in the Lactobacillus casei cell wall extract (LCWE) mouse model of KD-like vasculitis over 4 months. The long-term immune, pathological, and functional changes occurring in cardiovascular lesions were characterized by histological examination, flow cytometric analysis, immunofluorescent staining of cardiovascular tissues, and transthoracic echocardiogram. Results: CAA and abdominal aorta dilations were detected up to 16 weeks following LCWE injection and initiation of acute vasculitis. We observed alterations in the composition of circulating immune cell profiles, such as increased monocyte frequencies in the acute phase of the disease and higher counts of neutrophils. We determined a positive correlation between circulating neutrophil and inflammatory monocyte counts and the severity of cardiovascular lesions early after LCWE injection. LCWE-induced KD-like vasculitis was associated with myocarditis and myocardial dysfunction, characterized by diminished ejection fraction and left ventricular remodeling, which worsened over time. We observed extensive fibrosis within the inflamed cardiac tissue early in the disease and myocardial fibrosis in later stages. Conclusion: Our findings indicate that increased circulating neutrophil counts in the acute phase are a reliable predictor of cardiovascular inflammation severity in LCWE-injected mice. Furthermore, long-term cardiac complications stemming from inflammatory cell infiltrations in the aortic root and coronary arteries, myocardial dysfunction, and myocardial fibrosis persist over long periods and are still detected up to 16 weeks after LCWE injection. [ABSTRACT FROM AUTHOR]

Multisystem inflammatory syndrome in children (MIS-C) manifests as a severe and uncontrolled inflammatory response with multiorgan involvement, occurring weeks after SARS-CoV-2 infection. Here, we utilized proteomics, RNA sequencing, autoantibody arrays, and B cell receptor (BCR) repertoire analysis to characterize MIS-C immunopathogenesis and identify factors contributing to severe manifestations and intensive care unit admission. Inflammation markers, humoral immune responses, neutrophil activation, and complement and coagulation pathways were highly enriched in MIS-C patient serum, with a more hyperinflammatory profile in severe than in mild MIS-C cases. We identified a strong autoimmune signature in MIS-C, with autoantibodies targeted to both ubiquitously expressed and tissue-specific antigens, suggesting autoantigen release and excessive antigenic drive may result from systemic tissue damage. We further identified a cluster of patients with enhanced neutrophil responses as well as high anti-Spike IgG and autoantibody titers. BCR sequencing of these patients identified a strong imprint of antigenic drive with substantial BCR sequence connectivity and usage of autoimmunity-associated immunoglobulin heavy chain variable region (IGHV) genes. This cluster was linked to a TRBV112 expanded T cell receptor (TCR) repertoire, consistent with previous studies indicating a superantigen-driven pathogenic process. Overall, we identify a combination of pathogenic pathways that culminate in MIS-C and may inform treatment., Introduction While cases of severe coronavirus disease 2019 (COVID-19) occur relatively less frequently in children than adults (1, 2), a small proportion of SARS-CoV-2-infected children develop a novel pediatric febrile [...]

Multisystem inflammatory syndrome in children (MIS-C), a hyperinflammatory syndrome associated with SARS-CoV-2 infection, shares clinical features with toxic shock syndrome, which is triggered by bacterial superantigens. Superantigen specificity for different V[beta] chains results in V[beta] skewing, whereby T cells with specific V[beta] chains and diverse antigen specificity are overrepresented in the T cell receptor (TCR) repertoire. Here, we characterized the TCR repertoire of MIS-C patients and found a profound expansion of TCR[beta] variable gene 11-2 (TRBV11-2), with up to 24% of clonal T cell space occupied by TRBV112 T cells, which correlated with MIS-C severity and serum cytokine levels. Analysis of TRBJ gene usage and complementarity-determining region 3 (CDR3) length distribution of MIS-C expanded TRBV11-2 clones revealed extensive junctional diversity. Patients with TRBV11-2 expansion shared HLA class I alleles A02, B35, and C04, indicating what we believe is a novel mechanism for CDR3-independent T cell expansion. In silico modeling indicated that polyacidic residues in the V[beta] chain encoded by TRBV11-2 (V[beta]21.3) strongly interact with the superantigen- like motif of SARS-CoV-2 spike glycoprotein, suggesting that unprocessed SARS-CoV-2 spike may directly mediate TRBV11-2 expansion. Overall, our data indicate that a CDR3-independent interaction between SARS-CoV-2 spike and TCR leads to T cell expansion and possibly activation, which may account for the clinical presentation of MIS-C., Introduction Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019 (COVID-19), which started as an epidemic in China and culminated in a global pandemic. [...]

Introduction: Osteopontin (OPN; also known as SPP1), an immunomodulatory cytokine highly expressed in bone marrow-derived macrophages (BMMΦ), is known to regulate diverse cellular and molecular immune responses. We previously revealed that glatiramer acetate (GA) stimulation of BMMΦ upregulates OPN expression, promoting an anti-inflammatory, pro-healing phenotype, whereas OPN inhibition triggers a pro-inflammatory phenotype. However, the precise role of OPN in macrophage activation state is unknown. Methods: Here, we applied global proteome profiling via mass spectrometry (MS) analysis to gain a mechanistic understanding of OPN suppression versus induction in primary macrophage cultures. We analyzed protein networks and immunerelated functional pathways in BMMΦ either with OPN knockout (OPNKO) or GAmediated OPN induction compared with wild type (WT) macrophages. The most significant differentially expressed proteins (DEPs) were validated using immunocytochemistry, western blot, and immunoprecipitation assays. Results and discussion: We identified 631 DEPs in OPNKO or GA-stimulated macrophages as compared to WT macrophages. The two topmost downregulated DEPs in OPNKO macrophages were ubiquitin C-terminal hydrolase L1 (UCHL1), a crucial component of the ubiquitin-proteasome system (UPS), and the anti-inflammatory Heme oxygenase 1 (HMOX-1), whereas GA stimulation upregulated their expression. We found that UCHL1, previously described as a neuron-specific protein, is expressed by BMMΦ and itsregulation in macrophages was OPN-dependent. Moreover, UCHL1 interacted with OPN in a protein complex. The effects of GA activation on inducing UCHL1 and anti-inflammatory macrophage profiles were mediated by OPN. Functional pathway analyses revealed two inversely regulated pathways in OPN-deficient macrophages: activated oxidative stress and lysosome-mitochondria-mediated apoptosis (e.g., ROS, Lamp1-2, ATP-synthase subunits, cathepsins, and cytochrome C and B subunits) and inhibited translation and proteolytic pathways (e.g., 60S and 40S ribosomal subunits and UPS proteins). In agreement with the proteome-bioinformatics data, western blot and immunocytochemical analyses revealed that OPN deficiency perturbs protein homeostasis in macrophages--inhibiting translation and protein turnover and inducing apoptosis--whereas OPN induction by GA restores cellular proteostasis. Taken together, OPN is essential for macrophage homeostatic balance via the regulation of protein synthesis, UCHL1-UPS axis, and mitochondria-mediated apoptotic processes, indicating its potential application in immune-based therapies. [ABSTRACT FROM AUTHOR]

Multisystem inflammatory syndrome in children (MIS-C) is a febrile pediatric inflammatory disease that may develop weeks after initial SARS-CoV-2 infection or exposure. MIS-C involves systemic hyperinflammation and multiorgan involvement, including severe cardiovascular, gastrointestinal (GI) and neurological symptoms. Some clinical attributes of MIS-C--such as persistent fever, rashes, conjunctivitis and oral mucosa changes (red fissured lips and strawberry tongue)--overlap with features of Kawasaki disease (KD). In addition, MIS-C shares striking clinical similarities with toxic shock syndrome (TSS), which is triggered by bacterial superantigens (SAgs). The remarkable similarities between MIS-C and TSS prompted a search for SAg-like structures in the SARS-CoV-2 virus and the discovery of a unique SAg-like motif highly similar to a Staphylococcal enterotoxin B (SEB) fragment in the SARS-CoV-2 spike 1 (S1) glycoprotein. Computational studies suggest that the SAg-like motif has a high affinity for binding T-cell receptors (TCRs) and MHC Class II proteins. Immunosequencing of peripheral blood samples from MIS-C patients revealed a profound expansion of TCR b variable gene 11-2 (TRBV11-2), which correlates withMIS-C severity and serum cytokine levels, consistent with a SAg-triggered immune response. Computational sequence analysis of SARS-CoV-2 spike further identified conserved neurotoxin-like motifs which may alter neuronal cell function and contribute to neurological symptoms in COVID-19 and MIS-C patients. Additionally, autoantibodies are detected during MIS-C, which may indicate development of post-SARS-CoV-2 autoreactive and autoimmune responses. Finally, prolonged persistence of SARS-CoV-2 RNA in the gut, increased gut permeability and elevated levels of circulating S1 have been observed in children with MIS-C. Accordingly, we hypothesize that continuous and prolonged exposure to the viral SAg-like and neurotoxin-like motifs in SARS-CoV-2 spike may promote autoimmunity leading to the development of postacute COVID-19 syndromes, including MIS-C and long COVID, as well as the neurological complications resulting from SARS-CoV-2 infection. [ABSTRACT FROM AUTHOR]

Objective: Kawasaki disease (KD) is the most common cause of acquired pediatric heart disease in the developed world. 10% of KD patients are resistant to front-line therapy, and no interventions exist to address secondary complications such as myocardial fibrosis. We sought to identify proteins and pathways associated with disease and anti-IL-1 treatment in a mouse model of KD. Methods: Vasculitis was induced via Lactobacillus casei cell wall extract (LCWE) injection in 5-week-old male mice. Groups of mice were injected with LCWE alone, LCWE and IL-1 receptor antagonist anakinra, or saline for controls. Upper heart tissue was assessed by quantitative mass spectrometry analysis. Expression and activation of STAT3 was assessed by immunohistochemistry, immunofluorescence and Western blot, and IL-6 expression by RNA-seq and ELISA. A STAT3 small molecular inhibitor and anti-IL-6R antibody were used to evaluate the role of STAT3 and IL-6 in disease development. Results: STAT3 was highly expressed and phosphorylated in cardiac tissue of LCWE-injected mice, and reduced following anakinra treatment. Il6 and Stat 3 gene expression was enhanced in abdominal aorta of LCWE-injected mice and reduced with Anakinra treatment. IL-6 serum levels were enhanced in LCWE-injected mice and normalized by anakinra. However, neither inhibition of STAT3 nor blockade of IL-6 altered disease development. Conclusion: Proteomic analysis of cardiac tissues demonstrates differential protein expression between KD-like, control and anakinra treated cardiac tissue. STAT3 and IL-6 were highly upregulated with LCWE and normalized by anakinra treatment. However, both STAT3 and IL-6 were dispensable for disease development indicating they may be bystanders of inflammation. [ABSTRACT FROM AUTHOR]

Multisystem Inflammatory Syndrome in Children (MIS-C) associated with COVID-19 is a newly recognized condition in children with recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. These children and adult patients with severe hyperinflammation present with a constellation of symptoms that strongly resemble toxic shock syndrome, an escalation of the cytotoxic adaptive immune response triggered upon the binding of pathogenic superantigens to T cell receptors (TCRs) and/or major histocompatibility complex class II (MHCII) molecules. Here, using structure-based computational models, we demonstrate that the SARS-CoV-2 spike (S) glycoprotein exhibits a high-affinity motif for binding TCRs, and may form a ternary complex with MHCII. The binding epitope on S harbors a sequence motif unique to SARS-CoV-2 (not present in other SARS-related coronaviruses), which is highly similar in both sequence and structure to the bacterial superantigen staphylococcal enterotoxin B. This interaction between the virus and human T cells could be strengthened by a rare mutation (D839Y/N/E) from a European strain of SARS-CoV-2. Furthermore, the interfacial region includes selected residues from an intercellular adhesion molecule (ICAM)-like motif shared between the SARS viruses from the 2003 and 2019 pandemics. A neurotoxin-like sequence motif on the receptor-binding domain also exhibits a high tendency to bind TCRs. Analysis of the TCR repertoire in adult COVID-19 patients demonstrates that those with severe hyperinflammatory disease exhibit TCR skewing consistent with superantigen activation. These data suggest that SARS-CoV-2 S may act as a superantigen to trigger the development of MIS-C as well as cytokine storm in adult COVID-19 patients, with important implications for the development of therapeutic approaches. [ABSTRACT FROM AUTHOR]

Background: Osteopontin (OPN; Spp1) is an immunomodulatory cytokine highly expressed by bone marrow‐derived macrophages (BMMΦ) known to regulate immune cell responses to brain injury. We have previously found that glatiramer acetate (GA) upregulates Spp1 expression, promoting an anti‐inflammatory and highly phagocytic phenotype in macrophages. Knockout of OPN (Spp1‐/‐) in BMMΦ impairs Alzheimer's disease (AD)‐related amyloid‐β (Aβ40 and Aβ42) phagocytosis and hinders the neuroprotective phenotype. Method: Here, we applied quantitative proteomics profiling and targeted immunohistochemistry (IHC) to explore the effects of Spp1 deficiency and GA modulation on protein networks of BMMΦ in vitro and in brains of AD transgenic (ADtg) mice. Result: Mass spectrometry analysis detected over 630 differentially expressed proteins in Spp1‐/‐ BMMΦ cell culture lysates. Approximately 170 proteins showed significantly (p<0.05) altered expression (>1.2‐fold). In Spp1‐/‐ cells, proteins were downregulated by a factor of 0.1‐1.23, whereas the same proteins were upregulated in GA‐stimulated cells by a factor of 0.1 to 1.42, relative to WT cells. Numerous ubiquitin proteasome system (UPS) related proteins were downregulated in Spp1‐/‐ macrophages. Of UPS proteins, ubiquitin carboxyterminal hydrolase L1 (UCHL1) was most downregulated in Spp1‐/‐ cells and upregulated by GA stimulation. We confirmed these findings by IHC and Western blot analysis in BMMΦ cells. Additionally, UCHL1 colocalized within Spp1‐expressing Iba1+CD45high infiltrating myelomonocytes in vivo; these cells migrated and concentrated around Aβ plaques in cortices ADtg mice. We revealed that Spp1 directly interacts with UCHL1 as validated by co‐immunoprecipitation. Further, substantial reductions in expression of proteins involved in translation in Spp1‐/‐ BMMΦ indicate that Spp1 may regulate translation processes. Importantly, lysosomal, mitochondrial and apoptosis pathway‐associated proteins were upregulated in Spp1‐deficient macrophages, including Lysozyme C‐2, ATP‐synthase subunits, Cathepsins and Cytochrome C and B subunits. Enhanced expression of lysosomal proteins in SPP1‐/‐ BMMΦ cells indicates increased autophagy. Conclusion: Spp1 deficiency in macrophages downregulates UCHL1 and associates with lysosome‐mitochondria mediated apoptosis pathway. This study reveals that UCHL1 is expressed by macrophages in vitro as well as in vivo in cerebral infiltrating immune cells in ADtg mice, thereby identifying novel UPS and lysosome‐mitochondrial related therapeutic targets for AD. [ABSTRACT FROM AUTHOR]

BACKGROUNDWeeks after SARS-CoV-2 infection or exposure, some children develop a severe, life-threatening illness called multisystem inflammatory syndrome in children (MIS-C). Gastrointestinal (GI) symptoms are common in patients with MIS-C, and a severe hyperinflammatory response ensues with potential for cardiac complications. The cause of MIS-C has not been identified to date.METHODSHere, we analyzed biospecimens from 100 children: 19 with MIS-C, 26 with acute COVID-19, and 55 controls. Stools were assessed for SARS-CoV-2 by reverse transcription PCR (RT-PCR), and plasma was examined for markers of breakdown of mucosal barrier integrity, including zonulin. Ultrasensitive antigen detection was used to probe for SARS-CoV-2 antigenemia in plasma, and immune responses were characterized. As a proof of concept, we treated a patient with MIS-C with larazotide, a zonulin antagonist, and monitored the effect on antigenemia and the patient's clinical response.RESULTSWe showed that in children with MIS-C, a prolonged presence of SARS-CoV-2 in the GI tract led to the release of zonulin, a biomarker of intestinal permeability, with subsequent trafficking of SARS-CoV-2 antigens into the bloodstream, leading to hyperinflammation. The patient with MIS-C treated with larazotide had a coinciding decrease in plasma SARS-CoV-2 spike antigen levels and inflammatory markers and a resultant clinical improvement above that achieved with currently available treatments.CONCLUSIONThese mechanistic data on MIS-C pathogenesis provide insight into targets for diagnosing, treating, and preventing MIS-C, which are urgently needed for this increasingly common severe COVID-19-related disease in children. [ABSTRACT FROM AUTHOR]

Genomic instability and inflammation are distinct hallmarks of aging, but the connection between them is poorly understood. Understanding their interrelationship will help unravel new mechanisms and therapeutic targets of aging and age-associated diseases. Here we report a novel mechanism directly linking genomic instability and inflammation in senescent cells through a mitochondria-regulated molecular circuit driven by p53 and cytoplasmic chromatin fragments (CCF). We show, through activation or inactivation of p53 by genetic and pharmacologic approaches, that p53 suppresses CCF accumulation and the downstream inflammatory senescence-associated secretory phenotype (SASP), without affecting cell cycle arrest. p53 activation suppressed CCF formation by promoting DNA repair, and this is reflected in maintenance of genomic integrity, particularly in subtelomeric regions, as shown by single cell genome resequencing. Activation of p53 in aged mice by pharmacological inhibition of MDM2 reversed signatures of aging, including age- and senescence-associated transcriptomic signatures of inflammation and age-associated accumulation of monocytes and macrophages in liver. Remarkably, mitochondria in senescent cells suppressed p53 activity by promoting CCF formation and thereby restricting ATM-dependent nuclear DNA damage signaling. These data provide evidence for a mitochondria-regulated p53 signaling circuit in senescent cells that controls DNA repair, genome integrity, and senescence- and age-associated inflammation. This pathway is immunomodulatory in mice and a potential target for healthy aging interventions by small molecules already shown to activate p53.

Kawasaki disease (KD) is the leading cause of acquired heart disease among children. Increased platelet counts and activation are observed during the course of KD, and elevated platelet counts are associated with higher risks of developing intravenous immunoglobulin resistance and coronary artery aneurysms. However, the role of platelets in KD pathogenesis remains unclear. Here, we analyzed transcriptomics data generated from the whole blood of patients with KD and discovered changes in the expression of platelet-related genes during acute KD. In the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis, LCWE injection increased platelet counts and the formation of monocyte-platelet aggregates (MPAs), upregulated the concentration of soluble P-selectin, and increased circulating thrombopoietin and interleukin 6 (IL-6). Furthermore, platelet counts correlated with the severity of cardiovascular inflammation. Genetic depletion of platelets (Mpl-/- mice) or treatment with an anti-CD42b antibody significantly reduced LCWE-induced cardiovascular lesions. Furthermore, in the mouse model, platelets promoted vascular inflammation via the formation of MPAs, which likely amplified IL-1B production. Altogether, our results indicate that platelet activation exacerbates the development of cardiovascular lesions in a murine model of KD vasculitis. These findings enhance our understanding of KD vasculitis pathogenesis and highlight MPAs, which are known to enhance IL-1B production, as a potential therapeutic target for this disorder.

Multisystem inflammatory syndrome in children (MIS-C) is a febrile pediatric inflammatory disease that may develop weeks after initial SARS-CoV-2 infection or exposure. MIS-C involves systemic hyperinflammation and multiorgan involvement, including severe cardiovascular, gastrointestinal (GI) and neurological symptoms. Some clinical attributes of MIS-C-such as persistent fever, rashes, conjunctivitis and oral mucosa changes (red fissured lips and strawberry tongue)-overlap with features of Kawasaki disease (KD). In addition, MIS-C shares striking clinical similarities with toxic shock syndrome (TSS), which is triggered by bacterial superantigens (SAgs). The remarkable similarities between MIS-C and TSS prompted a search for SAg-like structures in the SARS-CoV-2 virus and the discovery of a unique SAg-like motif highly similar to a Staphylococcal enterotoxin B (SEB) fragment in the SARS-CoV-2 spike 1 (S1) glycoprotein. Computational studies suggest that the SAg-like motif has a high affinity for binding T-cell receptors (TCRs) and MHC Class II proteins. Immunosequencing of peripheral blood samples from MIS-C patients revealed a profound expansion of TCR β variable gene 11-2 (TRBV11-2), which correlates with MIS-C severity and serum cytokine levels, consistent with a SAg-triggered immune response. Computational sequence analysis of SARS-CoV-2 spike further identified conserved neurotoxin-like motifs which may alter neuronal cell function and contribute to neurological symptoms in COVID-19 and MIS-C patients. Additionally, autoantibodies are detected during MIS-C, which may indicate development of post-SARS-CoV-2 autoreactive and autoimmune responses. Finally, prolonged persistence of SARS-CoV-2 RNA in the gut, increased gut permeability and elevated levels of circulating S1 have been observed in children with MIS-C. Accordingly, we hypothesize that continuous and prolonged exposure to the viral SAg-like and neurotoxin-like motifs in SARS-CoV-2 spike may promote autoimmunity leading to the development of post-acute COVID-19 syndromes, including MIS-C and long COVID, as well as the neurological complications resulting from SARS-CoV-2 infection., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Noval Rivas, Porritt, Cheng, Bahar and Arditi.)

Kawasaki disease (KD) is the leading cause of noncongenital heart disease in children. Studies in mice and humans propound the NLRP3/IL-1β pathway as the principal driver of KD pathophysiology. Endoplasmic reticulum (ER) stress can activate the NLRP3 inflammasome, but the potential implication of ER stress in KD pathophysiology has not been investigated to our knowledge. We used human patient data and the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis to characterize the impact of ER stress on the development of cardiovascular lesions. KD patient transcriptomics and single-cell RNA sequencing of the abdominal aorta from LCWE-injected mice revealed changes in the expression of ER stress genes. Alleviating ER stress genetically, by conditional deletion of inositol-requiring enzyme 1 (IRE1) in myeloid cells, or pharmacologically, by inhibition of IRE1 endoribonuclease (RNase) activity, led to significant reduction of LCWE-induced cardiovascular lesion formation as well as reduced caspase-1 activity and IL-1β secretion. These results demonstrate the causal relationship of ER stress to KD pathogenesis and highlight IRE1 RNase activity as a potential new therapeutic target.

Kawasaki disease (KD), an acute febrile childhood illness and systemic vasculitis of unknown etiology, is the leading cause of acquired heart disease among children. Experimental data from murine models of KD vasculitis and transcriptomics data generated from whole blood of KD patients indicate the involvement of the NLRP3 inflammasome and interleukin-1 (IL-1) signaling in KD pathogenesis. MicroRNA-223 (miR-223) is a negative regulator of NLRP3 activity and IL-1β production, and its expression has been reported to be upregulated during acute human KD; however, the specific role of miR-223 during KD vasculitis remains unknown. Here, using the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis, we demonstrate increased miR-223 expression in LCWE-induced cardiovascular lesions. Compared with control WT mice, LCWE-injected miR-223-deficient mice ( miR223 -/ y mice correlated with increased NLRP3 inflammasome activity and elevated IL-1β production, indicating that miR-223 limits cardiovascular lesion development by downmodulating NLRP3 inflammasome activity. Collectively, our data reveal a previously unappreciated role of miR-223 in regulating innate immune responses and in limiting KD vasculitis and its cardiovascular lesions by constraining the NLRP3 inflammasome and the IL-1β pathway. These data also suggest that miR-223 expression may be used as a marker for KD vasculitis pathogenesis and provide a novel therapeutic target.miR223 -/ y mice correlated with increased NLRP3 inflammasome activity and elevated IL-1β production, indicating that miR-223 limits cardiovascular lesion development by downmodulating NLRP3 inflammasome activity. Collectively, our data reveal a previously unappreciated role of miR-223 in regulating innate immune responses and in limiting KD vasculitis and its cardiovascular lesions by constraining the NLRP3 inflammasome and the IL-1β pathway. These data also suggest that miR-223 expression may be used as a marker for KD vasculitis pathogenesis and provide a novel therapeutic target., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Maruyama, Kocatürk, Lee, Abe, Lane, Moreira, Chen, Fishbein, Porritt, Noval Rivas and Arditi.)

We recently discovered a superantigen-like motif, similar to Staphylococcal enterotoxin B (SEB), near the S1/S2 cleavage site of SARS-CoV-2 Spike protein, which might explain the multisystem-inflammatory syndrome (MIS-C) observed in children and cytokine storm in severe COVID-19 patients. We show here that an anti-SEB monoclonal antibody (mAb), 6D3, can bind this viral motif, and in particular its PRRA insert, to inhibit infection by blocking the access of host cell proteases, TMPRSS2 or furin, to the cleavage site. The high affinity of 6D3 for the furin-cleavage site originates from a poly-acidic segment at its heavy chain CDR2, a feature shared with SARS-CoV-2-neutralizing mAb 4A8. The affinity of 6D3 and 4A8 for this site points to their potential utility as therapeutics for treating COVID-19, MIS-C, or common cold caused by human coronaviruses (HCoVs) that possess a furin-like cleavage site.

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., Competing Interests: Conflicts of interest The authors have declared that no conflict of interest exists.

Multisystem Inflammatory Syndrome in Children (MIS-C) associated with Coronavirus Disease 2019 (COVID-19) is a newly recognized condition in which children with recent SARS-CoV-2 infection present with a constellation of symptoms including hypotension, multiorgan involvement, and elevated inflammatory markers. These symptoms and the associated laboratory values strongly resemble toxic shock syndrome, an escalation of the cytotoxic adaptive immune response triggered upon the binding of pathogenic superantigens to MHCII molecules and T cell receptors (TCRs). Here, we used structure-based computational models to demonstrate that the SARS-CoV-2 spike (S) exhibits a high-affinity motif for binding TCR, interacting closely with both the α- and β-chains variable domains' complementarity-determining regions. The binding epitope on S harbors a sequence motif unique to SARS-CoV-2 (not present in any other SARS coronavirus), which is highly similar in both sequence and structure to bacterial superantigens. Further examination revealed that this interaction between the virus and human T cells is strengthened in the context of a recently reported rare mutation (D839Y/N/E) from a European strain of SARS-CoV-2. Furthermore, the interfacial region includes selected residues from a motif shared between the SARS viruses from the 2003 and 2019 pandemics, which has intracellular adhesion molecule (ICAM)-like character. These data suggest that the SARS-CoV-2 S may act as a superantigen to drive the development of MIS-C as well as cytokine storm in adult COVID-19 patients, with important implications for the development of therapeutic approaches.

Chlamydia pneumoniae , an obligate intracellular bacterial pathogen, has long been investigated as a potential developmental or exacerbating factor in various pathologies. Its unique lifestyle and ability to disseminate throughout the host while persisting in relative safety from the immune response has placed this obligate intracellular pathogen in the crosshairs as a potentially mitigating factor in chronic inflammatory diseases. Many animal model and human correlative studies have been performed to confirm or deny a role for C. pneumoniae infection in these disorders. In some cases, antibiotic clinical trials were conducted to prove a link between bacterial infections and atherosclerosis. In this review, we detail the latest information regarding the potential role that C. pneumoniae infection may have in chronic inflammatory diseases.

Glucocorticosteroids (GCS) are used on a daily basis to reduce airway inflammation in asthma and chronic obstructive pulmonary disease (COPD). This treatment is usually escalated during acute disease exacerbations, events often associated with virus infections. We examined the impact of GCS on anti-viral defences and virus replication and assessed supplementary interferon (IFN) treatment. Here, we report that treatment of primary human airway cells in vitro with GCS prior to rhinovirus (RV) or influenza A virus (IAV) infection significantly reduces the expression of innate anti-viral genes and increases viral replication. Mice given intranasal treatment with GCS prior to IAV infection developed more severe disease associated with amplified virus replication and elevated inflammation in the airways. Adjuvant IFN treatment markedly reduced GCS-amplified infections in human airway cells and in mouse lung. This study demonstrates that GCS cause an extrinsic compromise in anti-viral defences, enhancing respiratory virus infections and provides a rationale for adjuvant IFN treatment.