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COVID-19 manifests as a milder disease in children than adults, but the underlying mechanisms are not fully characterized. Here we assess the difference in cellular or humoral immune responses of pediatric and adult COVID-19 patients to see if these factors contribute to the severity dichotomy. Children’s non-specific immune profile is dominated by naive lymphocytes and HLA-DRhighCX3CR1low dendritic cells; meanwhile, children show strong specific antibody and T cell responses for viral structural proteins, with their T cell responses differing from adults by having weaker CD8+TNF+ T cells responses to S peptide pool but stronger responses to N and M peptide pools. Finally, viral mRNA is more abundant in pediatric patients. Our data thus support a scenario in which SARS-CoV-2 infected children contribute to transmission yet are less susceptible to COVID-19 symptoms due to strong and differential responses to the virus., Children often show milder COVID-19 symptoms, but the underlying mechanistic insights are still lacking. Here the authors profile both pediatric and adult cohorts of COVID-19 patients in Brazil to find that children exhibit higher viral load but stronger and biased cellular immunity, thereby serving clues for the differential responses in children.

Serological testing is a powerful tool in epidemiological studies for understanding viral circulation and assessing the effectiveness of virus control measures, as is the case of SARS-CoV-2, the pathogenic agent of COVID-19. Immunoassays can quantitatively reveal the concentration of antiviral antibodies. The assessment of antiviral antibody titers may provide information on virus exposure, and changes in IgG levels are also indicative of a reduction in viral circulation. In this work, we describe a serological study for the evaluation of antiviral IgG and IgM antibodies and their correlation with antiviral activity. The serological assay for IgG detection used two SARS-CoV-2 proteins as antigens, the nucleocapsid N protein and the 3CL protease. Cross-reactivity tests in animals have shown high selectivity for detection of antiviral antibodies, using both the N and 3CL antigens. Using samples of human serum from individuals previously diagnosed by PCR for COVID-19, we observed high sensitivity of the ELISA assay. Serological results with human samples also suggest that the combination of higher titers of antiviral IgG antibodies to different antigen targets may be associated with greater neutralization activity, which can be enhanced in the presence of antiviral IgM antibodies

Objectives Emerging evidence of dysregulation of the myeloid cell compartment urges investigations on neutrophil characteristics in coronavirus disease 2019 (COVID‐19). We isolated neutrophils from the blood of COVID‐19 patients receiving general ward care and from patients hospitalised at intensive care units (ICUs) to explore the kinetics of circulating neutrophils and factors important for neutrophil migration and activation. Methods Multicolour flow cytometry was exploited for the analysis of neutrophil differentiation and activation markers. Multiplex and ELISA technologies were used for the quantification of protease, protease inhibitor, chemokine and cytokine concentrations in plasma. Neutrophil polarisation responses were evaluated microscopically. Gelatinolytic and metalloproteinase activity in plasma was determined using a fluorogenic substrate. Co‐culturing healthy donor neutrophils with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) allowed us to investigate viral replication in neutrophils. Results Upon ICU admission, patients displayed high plasma concentrations of granulocyte–colony‐stimulating factor (G‐CSF) and the chemokine CXCL8, accompanied by emergency myelopoiesis as illustrated by high levels of circulating CD10−, immature neutrophils with reduced CXCR2 and C5aR expression. Neutrophil elastase and non‐metalloproteinase‐derived gelatinolytic activity were increased in plasma from ICU patients. Significantly higher levels of circulating tissue inhibitor of metalloproteinase 1 (TIMP‐1) in patients at ICU admission yielded decreased total MMP proteolytic activity in blood. COVID‐19 neutrophils were hyper‐responsive to CXCL8 and CXCL12 in shape change assays. Finally, SARS‐CoV‐2 failed to replicate inside human neutrophils. Conclusion Our study provides detailed insights into the kinetics of neutrophil phenotype and function in severe COVID‐19 patients, and supports the concept of an increased neutrophil activation state in the circulation., In this study, we found that patients suffering from severe COVID‐19 presented with immature, activated blood neutrophils and were characterized by elevated plasma levels of G‐CSF and CXCL8 that disappeared towards ICU discharge. Elevated neutrophil‐derived proteases in plasma of ICU patients were associated with increased non‐metalloproteinase‐derived gelatinolytic activity but decreased total MMP proteolytic activity. SARS‐CoV‐2 failed to replicate inside human neutrophils, suggesting that changes observed in neutrophils from patients with COVID‐19 are indirect consequences of SARS‐CoV‐2 infection in vivo.

Made available in DSpace on 2020-12-12T02:25:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundo de Apoio ao Ensino, à Pesquisa e Extensão, Universidade Estadual de Campinas Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) COVID-19 can result in severe lung injury. It remained to be determined why diabetic individuals with uncontrolled glucose levels are more prone to develop the severe form of COVID-19. The molecular mechanism underlying SARS-CoV-2 infection and what determines the onset of the cytokine storm found in severe COVID-19 patients are unknown. Monocytes and macrophages are the most enriched immune cell types in the lungs of COVID-19 patients and appear to have a central role in the pathogenicity of the disease. These cells adapt their metabolism upon infection and become highly glycolytic, which facilitates SARS-CoV-2 replication. The infection triggers mitochondrial ROS production, which induces stabilization of hypoxia-inducible factor-1α (HIF-1α) and consequently promotes glycolysis. HIF-1α-induced changes in monocyte metabolism by SARS-CoV-2 infection directly inhibit T cell response and reduce epithelial cell survival. Targeting HIF-1ɑ may have great therapeutic potential for the development of novel drugs to treat COVID-19. Diabetic people with uncontrolled blood glucose levels have a greater risk to develop severe COVID-19 disease. Codo et al. show that elevated glucose levels and glycolysis promote SARS-CoV-2 (CoV-2) replication and cytokine production in monocytes through a mitochondrial ROS/hypoxia-inducible factor-1α dependent pathway, resulting in T cell dysfunction and epithelial cell death. Laboratory of Immunometabolism Department of Genetics Evolution Microbiology and Immunology Institute of Biology University of Campinas Department of Genetics Evolution Microbiology and Immunology Institute of Biology University of Campinas Department of Biochemistry and Tissue Biology Institute of Biology University of Campinas Department of Genetics at Ribeirao Preto Medical School University of Sao Paulo, Ribeirao Preto Department of Clinical and Toxicological analyses School of Pharmaceutical Sciences University of São Paulo Brazilian Biosciences National Laboratory (LNBio), Campinas Department of Animal Biology Institute of Biology University of Campinas, Campinas Department of Internal Medicine School of Medical Sciences University of Campinas, Campinas Department of Clinical Medicine School of Medical Sciences University of Campinas, Campinas Hematology and Hemotherapy Center University of Campinas, Campinas Obesity and Comorbidities Research Center (OCRC) University of Campinas Experimental Medicine Research Cluster (EMRC) University of Campinas Department of Structural and Functional Biology Institute of Biosciences São Paulo State University (UNESP), Botucatu D'Or Institute for Research and Education (IDOR) Instituto Nacional de Biomarcadores em Neuropsiquiatria Conselho Nacional de Desenvolvimento Científico e Tecnológico Department of Structural and Functional Biology Institute of Biosciences São Paulo State University (UNESP), Botucatu FAPESP: 20/04579-7 FAPESP: 2015/15626-8 FAPESP: 2016/18031-8 FAPESP: 2016/23328-0 FAPESP: 2017/01184-9 FAPESP: 2018/22505-0 FAPESP: 2019/00098-7 FAPESP: 2019/06372-3 FAPESP: 2020/04522-5 FAPESP: 2020/04558-0 FAPESP: 2020/04583-4 FAPESP: 2020/04746-0 FAPESP: 2020/04919-2 Fundo de Apoio ao Ensino, à Pesquisa e Extensão, Universidade Estadual de Campinas: 2274/20

COVID-19 can result in severe lung injury. It remained to be determined why diabetic individuals with uncontrolled glucose levels are more prone to develop the severe form of COVID-19. The molecular mechanism underlying SARS-CoV-2 infection and what determines the onset of the cytokine storm found in severe COVID-19 patients are unknown. Monocytes/macrophages are the most enriched immune cell types in the lungs of COVID-19 patients and appear to have a central role in the pathogenicity of the disease. These cells adapt their metabolism upon infection and become highly glycolytic, which facilitates SARS-CoV-2 replication. The infection triggers mitochondrial ROS production, which induces stabilization of hypoxia-inducible factor- 1α (HIF - 1α) and consequently promotes glycolysis. HIF- 1α-induced changes in monocyte metabolism by SARS-CoV-2 infection directly inhibit T cell response and reduce epithelial cell survival. Targeting HIF-1 ɑ may have great therapeutic potential for the development of novel drugs to treat COVID-19.

Mayaro virus (MAYV) belongs to the Alphavirus genus along with other important viruses such as Chikungunya virus (CHIKV). The chronic disease caused by MAYV is described by a highly incapacitating joint pain which may endure for several weeks or months in at least 50% of the symptomatic patients. Recently, reports of sporadic outbreaks in humans has increased, however, the dynamic of the Mayaro infection is not completely understood and there is still no treatment or vaccine available. Herein, our goal was to develop an animal immunocompromised model ideal to understand the immunologic dynamic of the disease and perform antiviral tests.