Evaluation of ATP-adenosine axis in lymphocytes in SARS-CoV-2 infection

Adenosine triphosphate (ATP) is a predominantly intracellular molecule that can be released to the extracellular space during cellular activation, tissue stress or damage. Out of the cell, ATP can play a crucial role in immune responses and inflammation. Extracellular ATP can be rapidly converted to ADP, AMP and adenosine by ectonucleotidases, such as CD39 and CD73 that are present in the cell membrane. Adenosine, in turn, can induce anti-inflammatory responses by inducing cyclic AMP. Changes in ATP metabolism and signaling have already been observed in cases of viral infection with chronic immunoactivation, such as HIV, and our preliminary data suggest that a similar scenario could be occurring in the infection with the new coronavirus that causes COVID-19. This infection can lead to a high production of pro-inflammatory cytokines, a phenomenon known as cytokine storm. Analyzing CD39 and CD73 expression in leukocytes of COVID-19 patients, with moderate and severe clinical forms of the disease, from the Clinics Hospital of São Paulo we observed a reduction in the frequency of neutrophils and CD8+ T cells expressing CD73. Besides that, we detected a reduction of CD19+CD39+CD73+ cells in peripheral blood of patients with severe COVID-19, suggesting that extracellular ATP metabolism in B cells can be altered in the disease. Therefore, we believe that the reduction of CD19+CD39+CD73+ cells could be associated to the pro-inflammatory profile observed in COVID-19 patients. To test our hypothesis, CD19+ B cells will be isolated from COVID-19 patients and healthy controls and ATP metabolism into adenosine will be evaluated by high performance liquid chromatography (HPLC). The immunomodulatory effects of adenosine will be tested in vitro in B cell and mononuclear cells cultures. The immunomodulatory role of B cells from COVID-19 patients in autologous T cell activation and proliferation will also be investigated. Finally, we will also verify the expression of other ectonucleotidases and adenosine receptors in COVID-19 patients as well as the serum levels of adenosine. These results may help to understand the mechanisms involved in COVID-19 pathogenesis and will indicate possible strategies for therapeutic interventions.