Clinical and Proteomic Correlates of Plasma ACE2 (Angiotensin-Converting Enzyme 2) in Human Heart Failure.

ACE2 (angiotensin-converting enzyme 2) is a key component of the renin-angiotensin-aldosterone system. Yet, little is known about the clinical and biologic correlates of circulating ACE2 levels in humans. We assessed the clinical and proteomic correlates of plasma (soluble) ACE2 protein levels in human heart failure. We measured plasma ACE2 using a modified aptamer assay among PHFS (Penn Heart Failure Study) participants (n=2248). We performed an association study of ACE2 against ≈5000 other plasma proteins measured with the SomaScan platform. Plasma ACE2 was not associated with ACE inhibitor and angiotensin-receptor blocker use. Plasma ACE2 was associated with older age, male sex, diabetes mellitus, a lower estimated glomerular filtration rate, worse New York Heart Association class, a history of coronary artery bypass surgery, and higher pro-BNP (pro-B-type natriuretic peptide) levels. Plasma ACE2 exhibited associations with 1011 other plasma proteins. In pathway overrepresentation analyses, top canonical pathways associated with plasma ACE2 included clathrin-mediated endocytosis signaling, actin cytoskeleton signaling, mechanisms of viral exit from host cells, EIF2 (eukaryotic initiation factor 2) signaling, and the protein ubiquitination pathway. In conclusion, in humans with heart failure, plasma ACE2 is associated with various clinical factors known to be associated with severe coronavirus disease 2019 (COVID-19), including older age, male sex, and diabetes mellitus, but is not associated with ACE inhibitor and angiotensin-receptor blocker use. Plasma ACE2 protein levels are prominently associated with multiple cellular pathways involved in cellular endocytosis, exocytosis, and intracellular protein trafficking. Whether these have a causal relationship with ACE2 or are relevant to novel coronavirus-2 infection remains to be assessed in future studies.

Antecedent Administration of Angiotensin-Converting Enzyme Inhibitors or Angiotensin II Receptor Antagonists and Survival After Hospitalization for COVID-19 Syndrome.

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) utilizes the angiotensin-converting enzyme-2 (ACE-2) receptor to enter human cells. Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor antagonists (ARB) are associated with ACE-2 upregulation. We hypothesized that antecedent use of ACEI/ARB may be associated with mortality in coronavirus disease 2019 (COVID-19). Methods and Results We used the Coracle registry, which contains data of patients hospitalized with COVID-19 in 4 regions of Italy, and restricted analyses to those ≥50 years of age. The primary outcome was in-hospital mortality. Among these 781 patients, 133 (17.0%) used an ARB and 171 (21.9%) used an ACEI. While neither sex nor smoking status differed by user groups, patients on ACEI/ARB were older and more likely to have hypertension, diabetes mellitus, and congestive heart failure. The overall mortality rate was 15.1% (118/781) and increased with age (PTrend<0.0001). The crude odds ratios (ORs) for death for ACEI users and ARB users were 0.98, 95% CI, 0.60-1.60, P=0.9333, and 1.13, 95% CI, 0.67-1.91, P=0.6385, respectively. After adjusting for age, hypertension, diabetes mellitus, and congestive heart failure, antecedent ACEI administration was associated with reduced mortality (OR, 0.55; 95% CI, 0.31-0.98, P=0.0436); a similar, but weaker trend was observed for ARB administration (OR, 0.58; 95% CI, 0.32-1.07, P=0.0796). Conclusions In those aged ≥50 years hospitalized with COVID-19, antecedent use of ACEI was independently associated with reduced risk of inpatient death. Our findings suggest a protective role of renin-angiotensin-aldosterone system inhibition in patients with high cardiovascular risk affected by COVID-19.

Destabilizing the structural integrity of COVID-19 by caulerpin and its derivatives along with some antiviral drugs: An in silico approaches for a combination therapy.

Presently, the SARS-CoV-2 (COVID-19) pandemic has been spreading throughout the world. Some drugs such as lopinavir, simeprevir, hydroxychloroquine, chloroquine, and amprenavir have been recommended for COVID-19 treatment by some researchers, but these drugs were not effective enough against this virus. This study based on in silico approaches was aimed to increase the anti-COVID-19 activities of these drugs by using caulerpin and its derivatives as an adjunct drug against SARS-CoV-2 receptor proteins: the SARS-CoV-2 main protease and the SARS-CoV-2 spike protein. Caulerpin exhibited antiviral activities against chikungunya virus and herpes simplex virus type 1. Caulerpin and some of its derivatives showed inhibitory activity against Alzheimer's disease. The web server ANCHOR revealed higher protein stability for the two receptors with disordered score (< 0.6). Molecular docking analysis showed that the binding energies of most of the caulerpin derivatives were higher than all the suggested drugs for the two receptors. Also, we deduced that inserting NH2, halogen, and vinyl groups can increase the binding affinity of caulerpin toward 6VYB and 6LU7, while inserting an alkyl group decreases the binding affinity of caulerpin toward 6VYB and 6LU7. So, we can modify the inhibitory effect of caulerpin against 6VYB and 6LU7 by inserting NH2, halogen, and vinyl groups. Based on the protein disordered results, the SARS-CoV-2 main protease and SARS-CoV-2 spike protein domain are highly stable proteins, so it is quite difficult to unstabilize their integrity by using individual drugs. Also, molecular dynamics (MD) simulation indicates that binding of the combination therapy of simeprevir and the candidate studied compounds to the receptors was stable and had no major effect on the flexibility of the protein throughout the simulations and provided a suitable basis for our study. So, this study suggested that caulerpin and its derivatives could be used as a combination therapy along with lopinavir, simeprevir, hydroxychloroquine, chloroquine, and amprenavir for disrupting the stability of SARS-CoV2 receptor proteins to increase the antiviral activity of these drugs.

Vitamin D and Immune Regulation: Antibacterial, Antiviral, Anti-Inflammatory.

Regulation of immune function continues to be one of the most well-recognized extraskeletal actions of vitamin D. This stemmed initially from the discovery that antigen presenting cells such as macrophages could actively metabolize precursor 25-hydroxyvitamin D (25D) to active 1,25-dihydroxyvitamin D (1,25D). Parallel observation that activated cells from the immune system expressed the intracellular vitamin D receptor (VDR) for 1,25D suggested a potential role for vitamin D as a localized endogenous modulator of immune function. Subsequent studies have expanded our understanding of how vitamin D exerts effects on both the innate and adaptive arms of the immune system. At an innate level, intracrine synthesis of 1,25D by macrophages and dendritic cells stimulates expression of antimicrobial proteins such as cathelicidin, as well as lowering intracellular iron concentrations via suppression of hepcidin. By potently enhancing autophagy, 1,25D may also play an important role in combatting intracellular pathogens such as M. tuberculosis and viral infections. Local synthesis of 1,25D by macrophages and dendritic cells also appears to play a pivotal role in mediating T-cell responses to vitamin D, leading to suppression of inflammatory T helper (Th)1 and Th17 cells, and concomitant induction of immunotolerogenic T-regulatory responses. The aim of this review is to provide an update on our current understanding of these prominent immune actions of vitamin D, as well as highlighting new, less well-recognized immune effects of vitamin D. The review also aims to place this mechanistic basis for the link between vitamin D and immunity with studies in vivo that have explored a role for vitamin D supplementation as a strategy for improved immune health. This has gained prominence in recent months with the global coronavirus disease 2019 health crisis and highlights important new objectives for future studies of vitamin D and immune function. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Systematic Analysis of Coronavirus Disease 2019 (COVID-19) Receptor ACE2 in Malignant Tumors: Pan-Cancer Analysis.

BACKGROUND: Coronavirus disease 2019 (COVID-19) was first detected in patients with pneumonia in December 2019 in China and it spread rapidly to the rest of the world becoming a global pandemic. Several observational studies have reported that cancer is a risk factor for COVID-19. On the other hand, ACE2, a receptor for the SARS-CoV-2 virus, was found to be aberrantly expressed in many tumors. However, the characterization of aberrant ACE2 expression in malignant tumors has not been elucidated. Here, we conducted a systematic analysis of the ACE2 expression profile across 31 types of tumors. METHODS: Distribution of ACE2 expression was analyzed using the GTEx, CCLE, TCGA pan-cancer databases. We evaluated the effect of ACE2 on clinical prognosis using the Kaplan-Meier survival plot and COX regression analysis. Correlation between ACE2 and immune infiltration levels was investigated in various cancer types. Additionally, the correlation between ACE2 and immune neoantigen, TMB, microsatellite instability, Mismatch Repair Genes (MMRs), HLA gene members, and DNA Methyltransferase (DNMT) was investigated. The frequency of ACE2 gene mutation in various tumors was analyzed. Functional enrichment analysis was conducted in various cancer types using the GSEA method. RESULTS: In normal tissues, ACE2 was highly expressed in almost all 31 organs tested. In cancer cell lines, the expression level of ACE2 was low to medium. Although aberrant expression was observed in most cancer types, high expression of ACE2 was not linked to OS, DFS, RFS, and DFI in most tumors in TCGA pan-cancer data. We found that ACE2 expression was significantly correlated with the infiltrating levels of macrophages and dendritic cells, CD4+ T cells, CD8+ T cells, and B cells in multiple tumors. A positive correlation between ACE2 expression and immune neoantigen, TMB, and microsatellite instability was found in multiple cancers. GSEA analysis which was carried out to determine the effect of ACE2 on tumors indicated that several cancer-associated pathways and immune-related pathways were hyperactivated in the high ACE2 expression group of most tumors. CONCLUSION: These findings suggest that ACE2 is not correlated with prognosis in most cancer types. However, elevated ACE2 is significantly correlated with immune infiltrating levels, including those of CD8+ T cells, CD4+ T cells, macrophages, neutrophils, and DCs in multiple cancers, especially in lung and breast cancer patients. These findings suggest that ACE2 may affect the tumor environment in cancer patients with COVID-19.

Features of HLA class I expression and its clinical relevance in SARS-CoV-2: What do we know so far?

Modifications in HLA-I expression are found in many viral diseases. They represent one of the immune evasion strategies most widely used by viruses to block antigen presentation and NK cell response, and SARS-CoV-2 is no exception. These alterations result from a combination of virus-specific factors, genetically encoded mechanisms, and the status of host defences and range from loss or upregulation of HLA-I molecules to selective increases of HLA-I alleles. In this review, I will first analyse characteristic features of altered HLA-I expression found in SARS-CoV-2. I will then discuss the potential factors underlying these defects, focussing on HLA-E and class-I-related (like) molecules and their receptors, the most documented HLA-I alterations. I will also draw attention to potential differences between cells transfected to express viral proteins and those presented as part of authentic infection. Consideration of these factors and others affecting HLA-I expression may provide us with improved possibilities for research into cellular immunity against viral variants.

Vitamin D, Depressive Symptoms, and Covid-19 Pandemic.

Since the COVID-19 outbreak, studies across diverse countries have strongly pointed toward the emergence of a mental health crisis, with a dramatic increase in the prevalence of depressive psychopathology and suicidal tendencies. Vitamin D deficiency has been associated with an increased risk of mental health problems as well as individual responses to stress. Studies have discussed the relationship between low serum vitamin D concentrations and depressive symptoms, suggesting that maintaining adequate concentrations of serum vitamin D seems to have a protective effect against it. Vitamin D was found to contribute to improved serotonergic neurotransmission in the experimental model of depression by regulating serotonin metabolism. The signaling of 1,25-dihydroxyvitamin D3, the active form of vitamin D, through vitamin D receptor (VDR) induces the expression of the gene of tryptophan hydroxylase 2 (TPH2), influences the expression of serotonin reuptake transporter (SERT) as well as the levels of monoamine oxidase-A (MAO-A), the enzyme responsible for serotonin catabolism. Vitamin D also presents a relevant link with chronobiological interplay, which could influence the development of depressive symptoms when unbalance between light-dark cycles occurs. In this Perspective, we discussed the significant role of vitamin D in the elevation of stress-related depressive symptoms during the COVID-19 pandemic. It is suggested that vitamin D monitoring and, when deficiency is detected, supplementation could be considered as an important healthcare measure while lockdown and social isolation procedures last during the COVID-19 pandemic.

Critical Determinants of Cytokine Storm and Type I Interferon Response in COVID-19 Pathogenesis.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19), a rapidly evolving pandemic worldwide with at least 68 million COVID-19-positive cases and a mortality rate of about 2.2%, as of 10 December 2020. About 20% of COVID-19 patients exhibit moderate to severe symptoms. Severe COVID-19 manifests as acute respiratory distress syndrome (ARDS) with elevated plasma proinflammatory cytokines, including interleukin 1ß (IL-1ß), IL-6, tumor necrosis factor α (TNF-α), C-X-C motif chemokine ligand 10 (CXCL10/IP10), macrophage inflammatory protein 1 alpha (MIP-1α), and chemokine (C-C motif) ligand 2 (CCL2), with low levels of interferon type I (IFN-I) in the early stage and elevated levels of IFN-I during the advanced stage of COVID-19. Most of the severe and critically ill COVID-19 patients have had preexisting comorbidities, including hypertension, diabetes, cardiovascular diseases, and respiratory diseases. These conditions are known to perturb the levels of cytokines, chemokines, and angiotensin-converting enzyme 2 (ACE2), an essential receptor involved in SARS-CoV-2 entry into the host cells. ACE2 downregulation during SARS-CoV-2 infection activates the angiotensin II/angiotensin receptor (AT1R)-mediated hypercytokinemia and hyperinflammatory syndrome. However, several SARS-CoV-2 proteins, including open reading frame 3b (ORF3b), ORF6, ORF7, ORF8, and the nucleocapsid (N) protein, can inhibit IFN type I and II (IFN-I and -II) production. Thus, hyperinflammation, in combination with the lack of IFN responses against SARS-CoV-2 early on during infection, makes the patients succumb rapidly to COVID-19. Therefore, therapeutic approaches involving anti-cytokine/anti-cytokine-signaling and IFN therapy would favor the disease prognosis in COVID-19. This review describes critical host and viral factors underpinning the inflammatory "cytokine storm" induction and IFN antagonism during COVID-19 pathogenesis. Therapeutic approaches to reduce hyperinflammation and their limitations are also discussed.

TrkC Is Essential for Nephron Function and Trans-Activates Igf1R Signaling.

BACKGROUND: Injury to kidney podocytes often results in chronic glomerular disease and consecutive nephron malfunction. For most glomerular diseases, targeted therapies are lacking. Thus, it is important to identify novel signaling pathways contributing to glomerular disease. Neurotrophic tyrosine kinase receptor 3 (TrkC) is expressed in podocytes and the protein transmits signals to the podocyte actin cytoskeleton. METHODS: Nephron-specific TrkC knockout (TrkC-KO) and nephron-specific TrkC-overexpressing (TrkC-OE) mice were generated to dissect the role of TrkC in nephron development and maintenance. RESULTS: Both TrkC-KO and TrkC-OE mice exhibited enlarged glomeruli, mesangial proliferation, basement membrane thickening, albuminuria, podocyte loss, and aspects of FSGS during aging. Igf1 receptor (Igf1R)-associated gene expression was dysregulated in TrkC-KO mouse glomeruli. Phosphoproteins associated with insulin, erb-b2 receptor tyrosine kinase (Erbb), and Toll-like receptor signaling were enriched in lysates of podocytes treated with the TrkC ligand neurotrophin-3 (Nt-3). Activation of TrkC by Nt-3 resulted in phosphorylation of the Igf1R on activating tyrosine residues in podocytes. Igf1R phosphorylation was increased in TrkC-OE mouse kidneys while it was decreased in TrkC-KO kidneys. Furthermore, TrkC expression was elevated in glomerular tissue of patients with diabetic kidney disease compared with control glomerular tissue. CONCLUSIONS: Our results show that TrkC is essential for maintaining glomerular integrity. Furthermore, TrkC modulates Igf-related signaling in podocytes.

Single-cell transcriptomic reveals molecular diversity and developmental heterogeneity of human stem cell-derived oligodendrocyte lineage cells.

Injury and loss of oligodendrocytes can cause demyelinating diseases such as multiple sclerosis. To improve our understanding of human oligodendrocyte development, which could facilitate development of remyelination-based treatment strategies, here we describe time-course single-cell-transcriptomic analysis of developing human stem cell-derived oligodendrocyte-lineage-cells (hOLLCs). The study includes hOLLCs derived from both genome engineered embryonic stem cell (ESC) reporter cells containing an Identification-and-Purification tag driven by the endogenous PDGFRα promoter and from unmodified induced pluripotent (iPS) cells. Our analysis uncovers substantial transcriptional heterogeneity of PDGFRα-lineage hOLLCs. We discover sub-populations of human oligodendrocyte progenitor cells (hOPCs) including a potential cytokine-responsive hOPC subset, and identify candidate regulatory genes/networks that define the identity of these sub-populations. Pseudotime trajectory analysis defines developmental pathways of oligodendrocytes vs astrocytes from PDGFRα-expressing hOPCs and predicts differentially expressed genes between the two lineages. In addition, pathway enrichment analysis followed by pharmacological intervention of these pathways confirm that mTOR and cholesterol biosynthesis signaling pathways are involved in maturation of oligodendrocytes from hOPCs.

The Aryl Hydrocarbon Receptor as a Modulator of Anti-viral Immunity.

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor, which interacts with a wide range of organic molecules of endogenous and exogenous origin, including environmental pollutants, tryptophan metabolites, and microbial metabolites. The activation of AHR by these agonists drives its translocation into the nucleus where it controls the expression of a large number of target genes that include the AHR repressor (AHRR), detoxifying monooxygenases (CYP1A1 and CYP1B1), and cytokines. Recent advances reveal that AHR signaling modulates aspects of the intrinsic, innate and adaptive immune response to diverse microorganisms. This review will focus on the increasing evidence supporting a role for AHR as a modulator of the host response to viral infection.

Functions of Thrombospondin-1 in the Tumor Microenvironment.

The identification of thrombospondin-1 as an angiogenesis inhibitor in 1990 prompted interest in its role in cancer biology and potential as a therapeutic target. Decreased thrombospondin-1 mRNA and protein expression are associated with progression in several cancers, while expression by nonmalignant cells in the tumor microenvironment and circulating levels in cancer patients can be elevated. THBS1 is not a tumor suppressor gene, but the regulation of its expression in malignant cells by oncogenes and tumor suppressor genes mediates some of their effects on carcinogenesis, tumor progression, and metastasis. In addition to regulating angiogenesis and perfusion of the tumor vasculature, thrombospondin-1 limits antitumor immunity by CD47-dependent regulation of innate and adaptive immune cells. Conversely, thrombospondin-1 is a component of particles released by immune cells that mediate tumor cell killing. Thrombospondin-1 differentially regulates the sensitivity of malignant and nonmalignant cells to genotoxic stress caused by radiotherapy and chemotherapy. The diverse activities of thrombospondin-1 to regulate autophagy, senescence, stem cell maintenance, extracellular vesicle function, and metabolic responses to ischemic and genotoxic stress are mediated by several cell surface receptors and by regulating the functions of several secreted proteins. This review highlights progress in understanding thrombospondin-1 functions in cancer and the challenges that remain in harnessing its therapeutic potential.

Virus-Mediated Cell-Cell Fusion.

Cell-cell fusion between eukaryotic cells is a general process involved in many physiological and pathological conditions, including infections by bacteria, parasites, and viruses. As obligate intracellular pathogens, viruses use intracellular machineries and pathways for efficient replication in their host target cells. Interestingly, certain viruses, and, more especially, enveloped viruses belonging to different viral families and including human pathogens, can mediate cell-cell fusion between infected cells and neighboring non-infected cells. Depending of the cellular environment and tissue organization, this virus-mediated cell-cell fusion leads to the merge of membrane and cytoplasm contents and formation of multinucleated cells, also called syncytia, that can express high amount of viral antigens in tissues and organs of infected hosts. This ability of some viruses to trigger cell-cell fusion between infected cells as virus-donor cells and surrounding non-infected target cells is mainly related to virus-encoded fusion proteins, known as viral fusogens displaying high fusogenic properties, and expressed at the cell surface of the virus-donor cells. Virus-induced cell-cell fusion is then mediated by interactions of these viral fusion proteins with surface molecules or receptors involved in virus entry and expressed on neighboring non-infected cells. Thus, the goal of this review is to give an overview of the different animal virus families, with a more special focus on human pathogens, that can trigger cell-cell fusion.

Application of CAR-T Cell Therapy beyond Oncology: Autoimmune Diseases and Viral Infections.

Adoptive cell transfer (ACT) has long been at the forefront of the battle with cancer that began last century with the therapeutic application of tumor-infiltrating lymphocytes (TILs) against melanoma. The development of novel ACT approaches led researchers and clinicians to highly efficient technologies based on genetically engineered T lymphocytes, with chimeric antigen receptor (CAR)-T cells as the most prominent example. CARs consist of an extracellular domain that represents the single-chain variable fragment (scFv) of a monoclonal antibody (mAb) responsible for target recognition and the intracellular domain, which was built from up to several signaling motifs that mediated T cell activation. The number of potential targets amenable for CAR-T cell therapy is expanding rapidly, which means that the tremendous success of this approach in oncology could be further translated to treating other diseases. In this review, we outlined modern trends and recent developments in CAR-T cell therapy from an unusual point of view by focusing on diseases beyond cancer, such as autoimmune disorders and viral infections, including SARS-CoV-2.

ACE2 expression is related to the interferon response in airway epithelial cells but is that functional for SARS-CoV-2 entry?

In vitro interferon (IFN)α treatment of primary human upper airway basal cells has been shown to drive ACE2 expression, the receptor of SARS-CoV-2. The protease furin is also involved in mediating SARS-CoV-2 and other viral infections, although its association with early IFN response has not been evaluated yet. In order to assess the in vivo relationship between ACE2 and furin expression and the IFN response in nasopharyngeal cells, we first examined ACE2 and furin levels and their correlation with the well-known marker of IFNs' activation, ISG15, in children (n = 59) and adults (n = 48), during respiratory diseases not caused by SARS-CoV-2. A strong positive correlation was found between ACE2 expression, but not of furin, and ISG15 in all patients analyzed. In addition, type I and III IFN stimulation experiments were performed to examine the IFN-mediated activation of ACE2 isoforms (full-length and truncated) and furin in epithelial cell lines. Following all the IFNs treatments, only the truncated ACE2 levels, were upregulated significantly in the A549 and Calu3 cells, in particular by type I IFNs. If confirmed in vivo following IFNs' activation, the induction of the truncated ACE2 isoform only would not enhance the risk of SARS-CoV-2 infection in the respiratory tract.

Insight into vaccine development for Alpha-coronaviruses based on structural and immunological analyses of spike proteins.

Coronaviruses that infect humans belong to the Alpha-coronavirus (including HCoV-229E) and Beta-coronavirus (including SARS-CoV and SARS-CoV-2) genera. In particular, SARS-CoV-2 is currently a major threat to public health worldwide. The spike (S) homotrimers bind to their receptors via the receptor-binding domain (RBD), which is a major target to block viral entry. In this study, we selected Alpha-coronavirus (HCoV-229E) and Beta-coronavirus (SARS-CoV and SARS-CoV-2) as models. Their RBDs exist two different conformational states (lying or standing) in the prefusion S-trimer structure. Then, the differences in the immune responses to RBDs from these coronaviruses were analyzed structurally and immunologically. Our results showed that more RBD-specific antibodies (antibody titers: 1.28×105; 2.75×105) were induced by the S-trimer with the RBD in the "standing" state (SARS-CoV and SARS-CoV-2) than the S-trimer with the RBD in the "lying" state (HCoV-229E, antibody titers: <500), and more S-trimer-specific antibodies were induced by the RBD in the SARS-CoV and SARS-CoV-2 (antibody titers: 6.72×105; 5×105) than HCoV-229E (antibody titers:1.125×103). Besides, we found that the ability of the HCoV-229E RBD to induce neutralizing antibodies was lower than S-trimer, and the intact and stable S1 subunit was essential for producing efficient neutralizing antibodies against HCoV-229E. Importantly, our results reveal different vaccine strategies for coronaviruses, and S-trimer is better than RBD as a target for vaccine development in Alpha-coronavirus Our findings will provide important implications for future development of coronavirus vaccines.Importance Outbreak of coronaviruses, especially SARS-CoV-2, poses a serious threat to global public health. Development of vaccines to prevent the coronaviruses that can infect humans has always been a top priority. Coronavirus spike (S) protein is considered as a major target for vaccine development. Currently, structural studies have shown that Alpha-coronavirus (HCoV-229E) and Beta-coronavirus (SARS-CoV and SARS-CoV-2) RBDs are in "lying" and "standing" states in the prefusion S-trimer structure. Here, we evaluated the ability of S-trimer and RBD to induce neutralizing antibodies among these coronaviruses. Our results showed that the S-trimer and RBD are both candidates for subunit vaccines in Beta-coronavirus (SARS-CoV and SARS-CoV-2) with a RBD "standing" state. However, for Alpha-coronavirus (HCoV-229E) with a RBD "lying" state, the S-trimer may be more suitable for subunit vaccines than the RBD. Our results will provide novel ideas for the development of vaccines targeting S protein in the future.

Immunological Assessment of Pediatric Multisystem Inflammatory Syndrome Related to Coronavirus Disease 2019.

BACKGROUND: Recently, cases of multisystem inflammatory syndrome in children (MIS-C) associated with coronavirus disease 2019 (COVID-19) have been reported worldwide. Negative polymerase chain reaction (RT-PCR) testing associated with positive serology in most of the cases suggests a postinfectious syndrome. Because the pathophysiology of this syndrome is still poorly understood, extensive virological and immunological investigations are needed. METHODS: We report a series of 4 pediatric patients admitted to Geneva University Hospitals with persistent fever and laboratory evidence of inflammation meeting the published definition of MIS-C related to COVID-19, to whom an extensive virological and immunological workup was performed. RESULTS: RT-PCRs on multiple anatomical compartments were negative, whereas anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglobulin A (IgA) and immunoglobulin G (IgG) were strongly positive by enzyme-linked immunosorbent assay and immunofluorescence. Both pseudoneutralization and full virus neutralization assays showed the presence of neutralizing antibodies in all children, confirming a recent infection with SARS-CoV-2. The analyses of cytokine profiles revealed an elevation in all cytokines, as reported in adults with severe COVID-19. Although differing in clinical presentation, some features of MIS-C show phenotypic overlap with hemophagocytic lymphohistiocytosis (HLH). In contrast to patients with primary HLH, our patients showed normal perforin expression and natural killer (NK) cell degranulation. The levels of soluble interleukin (IL)-2 receptor (sIL-2R) correlated with the severity of disease, reflecting recent T-cell activation. CONCLUSION: Our findings suggest that MIS-C related to COVID-19 is caused by a postinfectious inflammatory syndrome associated with an elevation in all cytokines, and markers of recent T-cell activation (sIL-2R) occurring despite a strong and specific humoral response to SARS-CoV-2. Further functional and genetic analyses are essential to better understand the mechanisms of host-pathogen interactions.

Neutrophils: Many Ways to Die.

Neutrophils or polymorphonuclear leukocytes (PMN) are key participants in the innate immune response for their ability to execute different effector functions. These cells express a vast array of membrane receptors that allow them to recognize and eliminate infectious agents effectively and respond appropriately to microenvironmental stimuli that regulate neutrophil functions, such as activation, migration, generation of reactive oxygen species, formation of neutrophil extracellular traps, and mediator secretion, among others. Currently, it has been realized that activated neutrophils can accomplish their effector functions and simultaneously activate mechanisms of cell death in response to different intracellular or extracellular factors. Although several studies have revealed similarities between the mechanisms of cell death of neutrophils and other cell types, neutrophils have distinctive properties, such as a high production of reactive oxygen species (ROS) and nitrogen species (RNS), that are important for their effector function in infections and pathologies such as cancer, autoimmune diseases, and immunodeficiencies, influencing their cell death mechanisms. The present work offers a synthesis of the conditions and molecules implicated in the regulation and activation of the processes of neutrophil death: apoptosis, autophagy, pyroptosis, necroptosis, NETosis, and necrosis. This information allows to understand the duality encountered by PMNs upon activation. The effector functions are carried out to eliminate invading pathogens, but in several instances, these functions involve activation of signaling cascades that culminate in the death of the neutrophil. This process guarantees the correct elimination of pathogenic agents, damaged or senescent cells, and the timely resolution of the inflammation that is essential for the maintenance of homeostasis in the organism. In addition, they alert the organism when the immunological system is being deregulated, promoting the activation of other cells of the immune system, such as B and T lymphocytes, which produce cytokines that potentiate the microbicide functions.

Bioinformatics and system biology approach to identify the influences of COVID-19 on cardiovascular and hypertensive comorbidities.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infected individuals that have hypertension or cardiovascular comorbidities have an elevated risk of serious coronavirus disease 2019 (COVID-19) disease and high rates of mortality but how COVID-$19$ and cardiovascular diseases interact are unclear. We therefore sought to identify novel mechanisms of interaction by identifying genes with altered expression in SARS-CoV-$2$ infection that are relevant to the pathogenesis of cardiovascular disease and hypertension. Some recent research shows the SARS-CoV-$2$ uses the angiotensin converting enzyme-$2$ (ACE-$2$) as a receptor to infect human susceptible cells. The ACE2 gene is expressed in many human tissues, including intestine, testis, kidneys, heart and lungs. ACE2 usually converts Angiotensin I in the renin-angiotensin-aldosterone system to Angiotensin II, which affects blood pressure levels. ACE inhibitors prescribed for cardiovascular disease and hypertension may increase the levels of ACE-$2$, although there are claims that such medications actually reduce lung injury caused by COVID-$19$. We employed bioinformatics and systematic approaches to identify such genetic links, using messenger RNA data peripheral blood cells from COVID-$19$ patients and compared them with blood samples from patients with either chronic heart failure disease or hypertensive diseases. We have also considered the immune response genes with elevated expression in COVID-$19$ to those active in cardiovascular diseases and hypertension. Differentially expressed genes (DEGs) common to COVID-$19$ and chronic heart failure, and common to COVID-$19$ and hypertension, were identified; the involvement of these common genes in the signalling pathways and ontologies studied. COVID-$19$ does not share a large number of differentially expressed genes with the conditions under consideration. However, those that were identified included genes playing roles in T cell functions, toll-like receptor pathways, cytokines, chemokines, cell stress, type 2 diabetes and gastric cancer. We also identified protein-protein interactions, gene regulatory networks and suggested drug and chemical compound interactions using the differentially expressed genes. The result of this study may help in identifying significant targets of treatment that can combat the ongoing pandemic due to SARS-CoV-$2$ infection.

Discontinuation versus continuation of renin-angiotensin-system inhibitors in COVID-19 (ACEI-COVID): a prospective, parallel group, randomised, controlled, open-label trial.

BACKGROUND: SARS-CoV-2 entry in human cells depends on angiotensin-converting enzyme 2, which can be upregulated by inhibitors of the renin-angiotensin system (RAS). We aimed to test our hypothesis that discontinuation of chronic treatment with ACE-inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) mitigates the course o\f recent-onset COVID-19. METHODS: ACEI-COVID was a parallel group, randomised, controlled, open-label trial done at 35 centres in Austria and Germany. Patients aged 18 years and older were enrolled if they presented with recent symptomatic SARS-CoV-2 infection and were chronically treated with ACEIs or ARBs. Patients were randomly assigned 1:1 to discontinuation or continuation of RAS inhibition for 30 days. Primary outcome was the maximum sequential organ failure assessment (SOFA) score within 30 days, where death was scored with the maximum achievable SOFA score. Secondary endpoints were area under the death-adjusted SOFA score (AUCSOFA), mean SOFA score, admission to the intensive care unit, mechanical ventilation, and death. Analyses were done on a modified intention-to-treat basis. This trial is registered with ClinicalTrials.gov, NCT04353596. FINDINGS: Between April 20, 2020, and Jan 20, 2021, 204 patients (median age 75 years [IQR 66-80], 37% females) were randomly assigned to discontinue (n=104) or continue (n=100) RAS inhibition. Within 30 days, eight (8%) of 104 died in the discontinuation group and 12 (12%) of 100 patients died in the continuation group (p=0·42). There was no significant difference in the primary endpoint between the discontinuation and continuation group (median [IQR] maximum SOFA score 0·00 (0·00-2·00) vs 1·00 (0·00-3·00); p=0·12). Discontinuation was associated with a significantly lower AUCSOFA (0·00 [0·00-9·25] vs 3·50 [0·00-23·50]; p=0·040), mean SOFA score (0·00 [0·00-0·31] vs 0·12 [0·00-0·78]; p=0·040), and 30-day SOFA score (0·00 [10-90th percentile, 0·00-1·20] vs 0·00 [0·00-24·00]; p=0·023). At 30 days, 11 (11%) in the discontinuation group and 23 (23%) in the continuation group had signs of organ dysfunction (SOFA score ≥1) or were dead (p=0·017). There were no significant differences for mechanical ventilation (10 (10%) vs 8 (8%), p=0·87) and admission to intensive care unit (20 [19%] vs 18 [18%], p=0·96) between the discontinuation and continuation group. INTERPRETATION: Discontinuation of RAS-inhibition in COVID-19 had no significant effect on the maximum severity of COVID-19 but may lead to a faster and better recovery. The decision to continue or discontinue should be made on an individual basis, considering the risk profile, the indication for RAS inhibition, and the availability of alternative therapies and outpatient monitoring options. FUNDING: Austrian Science Fund and German Center for Cardiovascular Research.