Alterations in CD39/CD73 Axis of T cells associated with COVID-19 severity (preprint)

Purinergic signaling modulates immune function and is involved in the immunopathogenesis of several viral infections. This study aimed to investigate alterations in purinergic pathways in COVID-19 patients. Lower plasma ATP and adenosine levels were identified in mild and severe COVID-19 patients associated with proinflammatory cytokine profiles compared to healthy controls. Mild COVID-19 patients presented lower frequencies of CD4+CD25+CD39+ (activated/memory Treg) and CD4+CD25+CD39+CD73+ T cells, and increased frequencies of high differentiated (CD27-CD28-) CD8+T cells compared to health controls. Severe COVID-19 patients also showed higher frequencies of CD4+CD39+, CD4+CD25-CD39+ (memory T effector cell), high differentiated CD8+ T cells (CD27-CD28-) and diminished frequencies of CD4+CD73+, CD4+CD25+CD39+ mTreg, CD4+CD25+CD39+CD73+, CD8+CD73+ and low-differentiated CD8+ T cells (CD27+CD28+) in the blood in relation to mild COVID-19 patients and controls. Moreover, severe COVID-19 patients presented higher expression of PD-1 on low-differentiated CD8+ T cells. Both severe and mild COVID-19 patients presented higher frequencies of CD4+Annexin-V+ and CD8+Annexin-V+ T cells, showing increased T cell apoptosis. Plasma samples collected from severe COVID-19 patients were able to decrease the expression of CD73 on CD4+ and CD8+ T cells of a healthy donor. Interestingly, the in vitro incubation of PBMC from severe COVID-19 patients with adenosine reduced the NF-kB activation in T cells and monocytes. Together, these data add new knowledge regarding the immunopathology of COVID-19 through purinergic regulation, especially concerning adenosine deficiency. Brief Commentary Background Host factors modulates the type and the strength of the immune response during the viral infection, as well as the disease outcomes. However, to date, the role of purinergic signaling in SARS-CoV-2 infection remains unclear. We sought to evaluate alterations in extracellular adenine nucleotides and CD39/CD73 axis in T cells and their relationship with acute COVID-19 immunopathogenesis. Translational Significance COVID-19 patients present lower extracellular ATP and adenosine levels associated with altered CD39 and CD73 expression in CD4+ and CD8+ T cells. Purinergic signaling correlated with alterations in the differentiation status of CD8+ T cells, lymphocyte mitochondrial membrane polarization and T cell apoptosis. Our demonstration of the lower NF-κB activation in T cells and monocytes after in vitro adenosine treatment may indicate the regulatory effect of adenosine in the inflammation and cytokine storm of COVID-19. This study adds new knowledge regarding the immunopathology of COVID-19 through purinergic regulation.

Strong anti-viral responses in pediatric COVID-19 patients in South Brazil (preprint)

Epidemiological evidence that COVID-19 manifests as a milder disease in children compared to adults has been reported by numerous studies, but the mechanisms underlying this phenomenon have not been characterized. It is still unclear how frequently children get infected, and/or generate immune responses to SARS-CoV-2. We have performed immune profiling of pediatric and adult COVID-19 patients in Brazil, producing over 38 thousand data points, asking if cellular or humoral immune responses could help explain milder disease in children. In this study, pediatric COVID-19 patients presented high viral titers. Though their non-specific immune profile was dominated by naive, non-activated lymphocytes, their dendritic cells expressed high levels of HLA-DR and were low in CX3CR1, indicating competence to generate immune responses that are not targeted to inflamed tissue. Finally, children formed strong specific antibody and T cell responses for viral structural proteins. Children s T cell responses differed from adults in that their CD8+ TNF+ T cell responses were low for S peptide but significantly higher against N and M peptide pools. Altogether, our data support a scenario in which SARS-CoV-2 infected children may contribute to transmission, though generating strong and differential responses to the virus that might associate with protection in pediatric COVID-19 presentation.

Strong specific anti-viral responses in pediatric COVID-19 patients in South Brazil (preprint)

Epidemiological evidence that COVID-19 manifests as a milder disease in children compared to adults has been reported by numerous studies, but the mechanisms underlying this phenomenon have not been characterized. It is still unclear how frequently children get infected, and/or generate immune responses to SARS-CoV-2. We have performed immune profiling of pediatric and adult COVID-19 patients in Brazil, producing over 38 thousand data points, asking if cellular or humoral immune responses could help explain milder disease in children. In this study, pediatric COVID-19 patients presented high viral titers. Though their non-specific immune profile was dominated by naive, non-activated lymphocytes, their dendritic cells expressed high levels of HLA-DR and were low in CX3CR1, indicating competence to generate immune responses that are not targeted to inflamed tissue. Finally, children formed strong specific antibody and T cell responses for viral structural proteins. Children’s T cell responses differed from adults in that their CD8+ TNFα+ T cell responses were low for S peptide but significantly higher against N and M peptide pools. Altogether, our data support a scenario in which SARS-CoV-2 infected children may contribute to transmission, though generating strong and differential responses to the virus that might associate with protection in pediatric COVID-19 presentation.