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. We evaluated the systemic levels of adenine-based purines, the frequencies of CD4+ and CD8+ T cells expressing CD39/CD73 ectonucleotidases, CD8+CD27-/+CD28-/+ T cells expressing PD-1 and the rates of lymphocyte apoptosis in the peripheral blood of patients with mild or severe COVID-19. Lower plasma ATP and adenosine levels were identified in mild and severe COVID-19 patients associated with higher systemic levels of IL-6, IL-10 and IL-17A compared to health 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. Together, these data add new knowledge regarding the immunopathology of COVID-19 through purinergic regulation.
Alterations in CD39/CD73 Axis of T cells associated with COVID-19 severity