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1.
Front Immunol ; 12: 780900, 2021.
Article in English | MEDLINE | ID: covidwho-1662580

ABSTRACT

Mesenchymal stem cells (MSCs) are multipotent adult stem cells present in virtually all tissues; they have potent self-renewal capacity and differentiate into multiple cell types. For many reasons, these cells are a promising therapeutic alternative to treat patients with severe COVID-19 and pulmonary post-COVID sequelae. These cells are not only essential for tissue regeneration; they can also alter the pulmonary environment through the paracrine secretion of several mediators. They can control or promote inflammation, induce other stem cells differentiation, restrain the virus load, and much more. In this work, we performed single-cell RNA-seq data analysis of MSCs in bronchoalveolar lavage samples from control individuals and COVID-19 patients with mild and severe clinical conditions. When we compared samples from mild cases with control individuals, most genes transcriptionally upregulated in COVID-19 were involved in cell proliferation. However, a new set of genes with distinct biological functions was upregulated when we compared severely affected with mild COVID-19 patients. In this analysis, the cells upregulated genes related to cell dispersion/migration and induced the γ-activated sequence (GAS) genes, probably triggered by IFNGR1 and IFNGR2. Then, IRF-1 was upregulated, one of the GAS target genes, leading to the interferon-stimulated response (ISR) and the overexpression of many signature target genes. The MSCs also upregulated genes involved in the mesenchymal-epithelial transition, virus control, cell chemotaxis, and used the cytoplasmic RNA danger sensors RIG-1, MDA5, and PKR. In a non-comparative analysis, we observed that MSCs from severe cases do not express many NF-κB upstream receptors, such as Toll-like (TLRs) TLR-3, -7, and -8; tumor necrosis factor (TNFR1 or TNFR2), RANK, CD40, and IL-1R1. Indeed, many NF-κB inhibitors were upregulated, including PPP2CB, OPTN, NFKBIA, and FHL2, suggesting that MSCs do not play a role in the "cytokine storm" observed. Therefore, lung MSCs in COVID-19 sense immune danger and act protectively in concert with the pulmonary environment, confirming their therapeutic potential in cell-based therapy for COVID-19. The transcription of MSCs senescence markers is discussed.


Subject(s)
COVID-19/immunology , Cell Proliferation/physiology , Inflammation/immunology , Lung/immunology , Mesenchymal Stem Cells/immunology , Regeneration/immunology , Adult , COVID-19/metabolism , Cell Differentiation/immunology , Cell Movement/immunology , Cytoplasm/immunology , Epithelial-Mesenchymal Transition/immunology , Humans , Inflammation/metabolism , Mesenchymal Stem Cells/metabolism , SARS-CoV-2/immunology , Up-Regulation/immunology , Young Adult
2.
Int Immunopharmacol ; 104: 108502, 2022 03.
Article in English | MEDLINE | ID: covidwho-1641351

ABSTRACT

BACKGROUND: SARS-CoV-2 infection can lead to the abnormal induction of cytokines and a dysregulated hyperinflammatory state that is implicated in disease severity and risk of death. There are several molecules present in blood associated with immune cellular response, inflammation, and oxidative stress that could be used as severity markers in respiratory viral infections such as COVID-19. However, there is a lack of clinical studies evaluating the role of oxidative stress-related molecules including glial fibrillary acidic protein (GFAP), the receptor for advanced glycation end products (RAGE), high mobility group box-1 protein (HMGB1) and cyclo-oxygenase-2 (COX-2) in COVID-19 pathogenesis. AIM: To evaluate the role of oxidative stress-related molecules in COVID-19. METHOD: An observational study with 93 Brazilian participants from September 2020 to April 2021, comprising 23 patients with COVID-19 admitted to intensive care unit (ICU), 19 outpatients with COVID-19 with mild to moderate symptoms, 17 individuals reporting a COVID-19 history, and 34 healthy controls. Blood samples were taken from all participants and western blot assay was used to determine the RAGE, HMGB1, GFAP, and COX-2 immunocontent. RESULTS: We found that GFAP levels were higher in patients with severe or critical COVID-19 compared to outpatients (p = 0.030) and controls (p < 0.001). A significant increase in immunocontents of RAGE (p < 0.001) and HMGB1 (p < 0.001) were also found among patients admitted to the ICU compared to healthy controls, as well as an overexpression of the inducible COX-2 (p < 0.001). In addition, we found a moderate to strong correlation between RAGE, GFAP and HMGB1 proteins. CONCLUSION: SARS-CoV-2 infection induces the upregulation of GFAP, RAGE, HMGB1, and COX-2 in patients with the most severe forms of COVID-19.


Subject(s)
COVID-19/diagnosis , Adolescent , Adult , Aged , Aged, 80 and over , Biomarkers/blood , COVID-19/blood , COVID-19/immunology , COVID-19/virology , Case-Control Studies , Child , Cyclooxygenase 2/blood , Cyclooxygenase 2/metabolism , Female , Glial Fibrillary Acidic Protein/blood , Glial Fibrillary Acidic Protein/metabolism , HMGB1 Protein/blood , HMGB1 Protein/metabolism , Healthy Volunteers , Humans , Inflammation/blood , Inflammation/diagnosis , Inflammation/immunology , Inflammation/virology , Male , Middle Aged , Oxidative Stress/immunology , Receptor for Advanced Glycation End Products/blood , Receptor for Advanced Glycation End Products/metabolism , SARS-CoV-2/immunology , Severity of Illness Index , Up-Regulation/immunology , Young Adult
3.
Med Oncol ; 39(3): 32, 2022 Jan 20.
Article in English | MEDLINE | ID: covidwho-1633699

ABSTRACT

To investigate the effects of isolated SARS-CoV-2 spike protein on prostate cancer cell survival. The effects of SARS-CoV-2 spike protein on LNCaP prostate cancer cell survival were assessed using clonogenic cell survival assay, quick cell proliferation assay, and caspase-3 activity kits. RT-PCR and immunohistochemistry were performed to investigate underlying molecular mechanisms. SARS-CoV-2 spike protein was found to inhibit prostate cancer cell proliferation as well as promote apoptosis. Further investigation revealed that anti-proliferative effects were associated with downregulation of the pro-proliferative molecule cyclin-dependent kinase 4 (CDK4). The increased rate of apoptosis was associated with the upregulation of pro-apoptotic molecule Fas ligand (FasL). SARS-CoV-2 spike protein inhibits the growth of LNCaP prostate cancer cells in vitro by a two-pronged approach of downregulating the expression of CDK4 and upregulating FasL. The introduction of SARS-CoV-2 spike protein into the body via COVID-19 vaccination may have the potential to inhibit prostate cancer in patients. This potential beneficial association between COVID-19 vaccines and prostate cancer inhibition will require more extensive studies before any conclusions can be drawn about any in vivo effects in a human model.


Subject(s)
COVID-19 Vaccines/immunology , Cell Proliferation/physiology , Prostatic Neoplasms/immunology , Prostatic Neoplasms/pathology , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/immunology , Antibodies, Viral/immunology , Apoptosis/immunology , COVID-19/immunology , Cell Line, Tumor , Cell Survival/immunology , Down-Regulation/immunology , Humans , Male , Up-Regulation/immunology , Vaccination/methods
4.
Eur J Immunol ; 52(1): 138-148, 2022 01.
Article in English | MEDLINE | ID: covidwho-1479399

ABSTRACT

The interferon pathway, a key antiviral defense mechanism, is being considered as a therapeutic target in COVID-19. Both, substitution of interferon and JAK/STAT inhibition to limit cytokine storms have been proposed. However, little is known about possible abnormalities in STAT signaling in immune cells during SARS-CoV-2 infection. We investigated downstream targets of interferon signaling, including STAT1, STAT2, pSTAT1 and 2, and IRF1, 7 and 9 by flow cytometry in 30 patients with COVID-19, 17 with mild, and 13 with severe infection. We report upregulation of STAT1 and IRF9 in mild and severe COVID-19 cases, which correlated with the IFN-signature assessed by Siglec-1 (CD169) expression on peripheral monocytes. Interestingly, Siglec-1 and STAT1 in CD14+ monocytes and plasmablasts showed lower expression among severe cases compared to mild cases. Contrary to the baseline STAT1 expression, the phosphorylation of STAT1 was enhanced in severe COVID-19 cases, indicating a dysbalanced JAK/STAT signaling that fails to induce transcription of interferon stimulated response elements (ISRE). This abnormality persisted after IFN-α and IFN-γ stimulation of PBMCs from patients with severe COVID-19. Data suggest impaired STAT1 transcriptional upregulation among severely infected patients may represent a potential predictive biomarker and would allow stratification of patients for certain interferon-pathway targeted treatments.


Subject(s)
COVID-19/immunology , Monocytes/immunology , SARS-CoV-2/immunology , STAT1 Transcription Factor/immunology , Signal Transduction/immunology , Up-Regulation/immunology , Adult , Aged , Female , Humans , Interferon Regulatory Factors/immunology , Male , Middle Aged , Patient Acuity , Phosphorylation/immunology
5.
Int J Mol Sci ; 22(18)2021 Sep 13.
Article in English | MEDLINE | ID: covidwho-1409702

ABSTRACT

The coronavirus disease 2019 (COVID-19) pandemic with high infectivity and mortality has caused severe social and economic impacts worldwide. Growing reports of COVID-19 patients with multi-organ damage indicated that severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) may also disturb the cardiovascular system. Herein, we used human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iCMs) as the in vitro platform to examine the consequence of SARS-CoV2 infection on iCMs. Differentiated iCMs expressed the primary SARS-CoV2 receptor angiotensin-converting enzyme-II (ACE2) and the transmembrane protease serine type 2 (TMPRSS2) receptor suggesting the susceptibility of iCMs to SARS-CoV2. Following the infection of iCMs with SARS-CoV2, the viral nucleocapsid (N) protein was detected in the host cells, demonstrating the successful infection. Bioinformatics analysis revealed that the SARS-CoV2 infection upregulates several inflammation-related genes, including the proinflammatory cytokine tumor necrosis factor-α (TNF-α). The pretreatment of iCMs with TNF-α for 24 h, significantly increased the expression of ACE2 and TMPRSS2, SASR-CoV2 entry receptors. The TNF-α pretreatment enhanced the entry of GFP-expressing SARS-CoV2 pseudovirus into iCMs, and the neutralization of TNF-α ameliorated the TNF-α-enhanced viral entry. Collectively, SARS-CoV2 elevated TNF-α expression, which in turn enhanced the SARS-CoV2 viral entry. Our findings suggest that, TNF-α may participate in the cytokine storm and aggravate the myocardial damage in COVID-19 patients.


Subject(s)
COVID-19/complications , Cardiovascular Diseases/immunology , Cytokine Release Syndrome/immunology , SARS-CoV-2/immunology , Tumor Necrosis Factor-alpha/metabolism , Angiotensin-Converting Enzyme 2/metabolism , COVID-19/immunology , COVID-19/pathology , COVID-19/virology , Cardiovascular Diseases/virology , Cell Differentiation , Cell Line , Computational Biology , Coronavirus Nucleocapsid Proteins/metabolism , Cytokine Release Syndrome/pathology , Cytokine Release Syndrome/virology , Humans , Induced Pluripotent Stem Cells , Myocardium/cytology , Myocardium/immunology , Myocardium/pathology , Myocytes, Cardiac/metabolism , Myocytes, Cardiac/virology , Phosphoproteins/metabolism , SARS-CoV-2/metabolism , SARS-CoV-2/pathogenicity , Serine Endopeptidases/metabolism , Tumor Necrosis Factor-alpha/antagonists & inhibitors , Up-Regulation/immunology , Virus Internalization/drug effects
6.
Hepatology ; 74(4): 1825-1844, 2021 10.
Article in English | MEDLINE | ID: covidwho-1372726

ABSTRACT

BACKGROUND AND AIMS: NASH will soon become the leading cause of liver transplantation in the United States and is also associated with increased COVID-19 mortality. Currently, there are no Food and Drug Administration-approved drugs available that slow NASH progression or address NASH liver involvement in COVID-19. Because animal models cannot fully recapitulate human NASH, we hypothesized that stem cells isolated directly from end-stage liver from patients with NASH may address current knowledge gaps in human NASH pathology. APPROACH AND RESULTS: We devised methods that allow the derivation, proliferation, hepatic differentiation, and extensive characterization of bipotent ductal organoids from irreversibly damaged liver from patients with NASH. The transcriptomes of organoids derived from NASH liver, but not healthy liver, show significant up-regulation of proinflammatory and cytochrome p450-related pathways, as well as of known liver fibrosis and tumor markers, with the degree of up-regulation being patient-specific. Functionally, NASH liver organoids exhibit reduced passaging/growth capacity and hallmarks of NASH liver, including decreased albumin production, increased free fatty acid-induced lipid accumulation, increased sensitivity to apoptotic stimuli, and increased cytochrome P450 metabolism. After hepatic differentiation, NASH liver organoids exhibit reduced ability to dedifferentiate back to the biliary state, consistent with the known reduced regenerative ability of NASH livers. Intriguingly, NASH liver organoids also show strongly increased permissiveness to severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) vesicular stomatitis pseudovirus as well as up-regulation of ubiquitin D, a known inhibitor of the antiviral interferon host response. CONCLUSION: Expansion of primary liver stem cells/organoids derived directly from irreversibly damaged liver from patients with NASH opens up experimental avenues for personalized disease modeling and drug development that has the potential to slow human NASH progression and to counteract NASH-related SARS-CoV-2 effects.


Subject(s)
End Stage Liver Disease/pathology , Liver/pathology , Non-alcoholic Fatty Liver Disease/pathology , Organoids/metabolism , Adult , Aged , Biopsy , COVID-19/complications , COVID-19/virology , Cell Differentiation/immunology , End Stage Liver Disease/immunology , Female , Gene Expression Profiling , Healthy Volunteers , Hepatocytes/immunology , Hepatocytes/metabolism , Humans , Induced Pluripotent Stem Cells/immunology , Induced Pluripotent Stem Cells/metabolism , Liver/cytology , Liver/immunology , Liver Regeneration , Male , Middle Aged , Non-alcoholic Fatty Liver Disease/immunology , Non-alcoholic Fatty Liver Disease/virology , Organoids/immunology , SARS-CoV-2/immunology , Up-Regulation/immunology
7.
Sci Rep ; 11(1): 11462, 2021 06 01.
Article in English | MEDLINE | ID: covidwho-1253984

ABSTRACT

An excessive immune response known as cytokine storm is the hallmark of severe COVID-19. The cause of this cytokine rampage is yet not known. Based on recent epidemiological evidence, we hypothesized that CD80/86 signaling is essential for this hyperinflammation, and that blocking this proinflammatory axis could be an effective therapeutic approach to protect against severe COVID-19. Here we provide exploratory evidence that abatacept, a drug that blocks CD80/86 co-stimulation, produces changes at the systemic level that are highly antagonistic of the proinflammatory processes elicited by COVID-19. Using RNA-seq from blood samples from a longitudinal cohort of n = 38 rheumatic patients treated with abatacept, we determined the immunological processes that are significantly regulated by this treatment. We then analyzed available blood RNA-seq from two COVID19 patient cohorts, a very early cohort from the epicenter of the pandemic in China (n = 3 COVID-19 cases and n = 3 controls), and a recent and larger cohort from the USA (n = 49 severe and n = 51 mild COVD-19 patients). We found a highly significant antagonism between SARS-CoV-2 infection and COVID-19 severity with the systemic response to abatacept. Analysis of previous single-cell RNA-seq data from bronchoalveolar lavage fluid from mild and severe COVID-19 patients and controls, reinforce the implication of the CD80/86 proinflammatory axis. Our functional results further support abatacept as a candidate therapeutic approach to prevent severe COVID-19.


Subject(s)
Abatacept/pharmacology , COVID-19/drug therapy , Cytokine Release Syndrome/prevention & control , Immunosuppressive Agents/pharmacology , SARS-CoV-2/immunology , Signal Transduction/drug effects , Abatacept/therapeutic use , Aged , Arthritis, Rheumatoid/blood , Arthritis, Rheumatoid/drug therapy , Arthritis, Rheumatoid/immunology , B7-1 Antigen/metabolism , B7-2 Antigen/metabolism , Bronchoalveolar Lavage Fluid/cytology , COVID-19/blood , COVID-19/complications , COVID-19/immunology , China , Cytokine Release Syndrome/immunology , Cytokine Release Syndrome/virology , Female , Humans , Immunosuppressive Agents/therapeutic use , Male , Middle Aged , Observational Studies as Topic , RNA-Seq , Severity of Illness Index , Signal Transduction/immunology , Single-Cell Analysis , Spain , United States , Up-Regulation/drug effects , Up-Regulation/immunology
8.
Eur J Immunol ; 51(6): 1436-1448, 2021 06.
Article in English | MEDLINE | ID: covidwho-1156872

ABSTRACT

COVID-19 is a life-threatening disease leading to bilateral pneumonia and respiratory failure. The underlying reasons why a smaller percentage of patients present with severe pulmonary symptoms whereas the majority is only mildly affected are to date not well understood. Comparing the immunological phenotype in healthy donors and patients with mild versus severe COVID-19 shows that in COVID-19 patients, NK-/B-cell activation and proliferation are enhanced independent of severity. As an important precondition for effective antibody responses, T-follicular helper cells and antibody secreting cells are increased both in patients with mild and severe SARS-CoV-2 infection. Beyond this, T cells in COVID-19 patients exhibit a stronger activation profile with differentiation toward effector cell phenotypes. Importantly, when looking at the rates of pulmonary complications in COVID-19 patients, the chemokine receptor CCR4 is higher expressed by both CD4 and CD8 T cells of patients with severe COVID-19. This raises the hypothesis that CCR4 upregulation on T cells in the pathogenesis of COVID-19 promotes stronger T-cell attraction to the lungs leading to increased immune activation with presumably higher pulmonary toxicity. Our study contributes significantly to the understanding of the immunological changes during COVID-19, as new therapeutic agents, preferentially targeting the immune system, are highly warranted.


Subject(s)
CD8-Positive T-Lymphocytes/immunology , COVID-19/immunology , Lung/immunology , Lymphocyte Activation , Receptors, CCR4/immunology , SARS-CoV-2/immunology , Up-Regulation/immunology , Adult , CD8-Positive T-Lymphocytes/pathology , COVID-19/pathology , Female , Humans , Lung/pathology , Lung/virology , Male , Middle Aged , Severity of Illness Index
9.
J Adv Res ; 30: 133-145, 2021 05.
Article in English | MEDLINE | ID: covidwho-950741

ABSTRACT

Background: Micro-RNAs (miRNAS) are non-coding, small RNAs that have essential roles in different biological processes through silencing genes, they consist of 18-24 nucleotide length RNA molecules. Recently, miRNAs have been viewed as important modulators of viral infections they can function as suppressors of gene expression by targeting cellular or viral RNAs during infection. Aim of review: We describe the biological roles and effects of miRNAs on SARS-CoV-2 life-cycle and pathogenicity, and we discuss the modulation of the immune system with micro-RNAs which would serve as a new foundation for the treatment of SARS-CoV-2 and other viral infections. Key scientific concepts of review: miRNAs are the key players that regulate the expression of the gene in the post-transcriptional phase and have important effects on viral infections, thus are potential targets in the development of novel therapeutics for the treatment of viral infections. Besides, micro-RNAs (miRNAs) modulation of immune-pathogenesis responses to viral infection is one of the most-known indirect effects, which leads to suppressing of the interferon (IFN-α/ß) signalling cascade or upregulation of the IFN-α/ß production another IFN-stimulated gene (ISGs) that inhibit replication of the virus. These virus-mediated alterations in miRNA levels lead to an environment that might either enhance or inhibit virus replication.


Subject(s)
COVID-19/immunology , Immunity/genetics , MicroRNAs/immunology , RNA, Viral/immunology , SARS-CoV-2/genetics , Gene Silencing/immunology , Humans , Interferons/immunology , Signal Transduction/immunology , Up-Regulation/immunology , Virus Diseases/immunology , Virus Replication/immunology
10.
Immun Inflamm Dis ; 8(4): 753-762, 2020 12.
Article in English | MEDLINE | ID: covidwho-893223

ABSTRACT

BACKGROUND: Severe acute respiratory syndrome coronavirus clade 2 (SARS-CoV-2) is a single-stranded RNA virus responsible for the global pandemic of the coronavirus disease-2019 (COVID-19). To date, there are still no effective approaches for the prevention and treatment of COVID-19. OBJECTIVE: The present study aims to explore the possible mechanisms of SARS-CoV-2 infection in human lung cells. METHODS: Data interpretation was conducted by recruiting bioinformatics analysis, including Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways analysis using downloaded data from the NCBI Gene Expression Omnibus database. RESULTS: The present study demonstrated that SARS-CoV-2 infection induces the upregulation of 14 interferon-stimulated genes, indicative of immune, and interferon responses to the virus. Notably, genes for pyrimidine metabolism and steroid hormone biosynthesis are selectively enriched in human lung cells after SARS-CoV-2 infection, suggesting that altered pyrimidine metabolism and steroid biosynthesis are remarkable, and perhaps druggable features after SARS-CoV-2 infection. Besides, there is a strong positive correlation between viral ORF1ab, ORF6, and angiotensin-converting enzyme 2 (ACE2) expression in human lung cells, implying that ACE2 facilitates SARS-CoV-2 infection and replication in host cells probably through the induction of ORF1ab and ORF6.


Subject(s)
Betacoronavirus/pathogenicity , Coronavirus Infections/etiology , Interferons/metabolism , Lung/pathology , Peptidyl-Dipeptidase A/metabolism , Pneumonia, Viral/etiology , Angiotensin-Converting Enzyme 2 , Betacoronavirus/metabolism , COVID-19 , Computational Biology , Coronavirus Infections/pathology , Epithelial Cells/immunology , Epithelial Cells/metabolism , Epithelial Cells/virology , Gene Expression Profiling , Humans , Lung/cytology , Lung/immunology , Lung/virology , Pandemics , Pneumonia, Viral/pathology , Polyproteins , Pyrimidines/metabolism , Respiratory Mucosa/cytology , Respiratory Mucosa/immunology , Respiratory Mucosa/metabolism , Respiratory Mucosa/virology , SARS-CoV-2 , Signal Transduction/immunology , Steroids/biosynthesis , Up-Regulation/immunology , Viral Proteins/metabolism
11.
Hum Immunol ; 81(12): 702-708, 2020 Dec.
Article in English | MEDLINE | ID: covidwho-773666

ABSTRACT

To discover immune factors that can predict the progression of COVID-19, we evaluated circulating immune cells and plasma cytokines in COVID-19 patients. We found that T cells, including CD4+ T cells and CD8+ T cells, were significantly decreased in severe COVID-19 symptoms but not in mild symptoms, in comparison with healthy people. T cells remained at a low level after recovery from severe COVID-19. CD4+CD25+CD127low Treg-enriched cells were significantly increased in either mild or severe COVID-19 patients, regardless of recovery or not. Moreover, in either mild or severe COVID-19 patients, Treg-enriched cells up-regulated CD25 and down-regulated CD127. After recovery, CD25 was partially down-regulated but still higher than the normal level, while CD127 returned to the normal level in mild patients but not severe patients. B cells were decreased in mild patients and further decreased in severe patients, and remained low after recovery. NK cells were decreased only in severe COVID-19, with a tendency to return to the normal level after recovery. Plasma IL-6 and IL-10 were both elevated in severe patients but not in mild patients. After recovery, IL-6 remained higher than its normal level, while IL-10 returned to the normal level. Binary logistic regression analysis indicated that CD4+ T cells, B cells, IL-6, and IL-10 were significantly associated with COVID-19 severity. Therefore, these parameters are indicators of COVID-19 severity. Dynamic monitoring of these parameters would benefit therapy planning and prognosis evaluation.


Subject(s)
B-Lymphocytes/immunology , COVID-19/immunology , Interleukin-10/blood , Interleukin-6/blood , Killer Cells, Natural/immunology , SARS-CoV-2/genetics , T-Lymphocytes, Regulatory/immunology , Adult , Aged , COVID-19/blood , COVID-19/epidemiology , COVID-19/virology , China/epidemiology , Female , Humans , Inflammation/immunology , Lymphocyte Count , Male , Middle Aged , Prognosis , Severity of Illness Index , Up-Regulation/immunology
12.
mBio ; 11(3)2020 06 23.
Article in English | MEDLINE | ID: covidwho-612678

ABSTRACT

It is well understood that the adaptive immune response to infectious agents includes a modulating suppressive component as well as an activating component. We now show that the very early innate response also has an immunosuppressive component. Infected cells upregulate the CD47 "don't eat me" signal, which slows the phagocytic uptake of dying and viable cells as well as downstream antigen-presenting cell (APC) functions. A CD47 mimic that acts as an essential virulence factor is encoded by all poxviruses, but CD47 expression on infected cells was found to be upregulated even by pathogens, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), that encode no mimic. CD47 upregulation was revealed to be a host response induced by the stimulation of both endosomal and cytosolic pathogen recognition receptors (PRRs). Furthermore, proinflammatory cytokines, including those found in the plasma of hepatitis C patients, upregulated CD47 on uninfected dendritic cells, thereby linking innate modulation with downstream adaptive immune responses. Indeed, results from antibody-mediated CD47 blockade experiments as well as CD47 knockout mice revealed an immunosuppressive role for CD47 during infections with lymphocytic choriomeningitis virus and Mycobacterium tuberculosis Since CD47 blockade operates at the level of pattern recognition receptors rather than at a pathogen or antigen-specific level, these findings identify CD47 as a novel potential immunotherapeutic target for the enhancement of immune responses to a broad range of infectious agents.IMPORTANCE Immune responses to infectious agents are initiated when a pathogen or its components bind to pattern recognition receptors (PRRs). PRR binding sets off a cascade of events that activates immune responses. We now show that, in addition to activating immune responses, PRR signaling also initiates an immunosuppressive response, probably to limit inflammation. The importance of the current findings is that blockade of immunomodulatory signaling, which is mediated by the upregulation of the CD47 molecule, can lead to enhanced immune responses to any pathogen that triggers PRR signaling. Since most or all pathogens trigger PRRs, CD47 blockade could be used to speed up and strengthen both innate and adaptive immune responses when medically indicated. Such immunotherapy could be done without a requirement for knowing the HLA type of the individual, the specific antigens of the pathogen, or, in the case of bacterial infections, the antimicrobial resistance profile.


Subject(s)
Betacoronavirus/immunology , CD47 Antigen/metabolism , Immunomodulation/immunology , Receptors, Pattern Recognition/immunology , A549 Cells , Adaptive Immunity/immunology , Animals , CD47 Antigen/genetics , Cell Line, Tumor , Cytokines/immunology , Female , Humans , Immunity, Innate/immunology , Lymphocytic choriomeningitis virus/immunology , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Mycobacterium tuberculosis/immunology , SARS-CoV-2 , Up-Regulation/immunology
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