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.

Increased LPS levels coexist with systemic inflammation and result in monocyte activation in severe COVID-19 patients (preprint)

This study aimed to evaluate the link between microbial translocation markers and systemic inflammation at the earliest time-point after hospitalization and at the last 72 h of hospitalization in survivors and non-survivors COVID-19 patients. Sixty-six SARS-CoV-2 RT-PCR+ infected patients and nine non-COVID-19 pneumonia controls were admitted in this study. Blood samples were collected at hospital admission (T1) (Controls and COVID-19+ patients) and 0-72 h before hospital discharge (T2, alive or dead) to analyze systemic cytokines and chemokines, LPS concentrations and soluble CD14 (sCD14) levels. THP-1 human monocytic cell line was incubated with plasma from survivors and non-survivors COVID-19 patients and their phenotype, activation status, TLR4, and chemokine receptors were analyzed by flow cytometry. COVID-19 patients presented higher IL-6, IFN-γ, TNF-α, TGF-β1, CCL2/MCP-1, CCL4/MIP-1β, and CCL5/RANTES levels than controls. Moreover, LPS and sCD14 were higher at hospital admission in SARS-CoV-2-infected patients. Non-survivors COVID-19 patients had increased LPS levels concomitant with higher IL-6, TNF-α, CCL2/MCP-1, and CCL5/RANTES levels at T2. Increased expression of CD16 and CCR5 were identified in THP-1 cells incubated with the plasma of survivor patients obtained at T2. The incubation of THP-1 with T2 plasma of non-survivors COVID-19 leads to higher TLR4, CCR2, CCR5, CCR7, and CD69 expression. In conclusion, increased microbial translocation during hospitalization coexist with the inflammatory condition of SARS-CoV-2 infection and could lead to higher monocyte activation in non-survivors COVID-19 patients.