D2.426 - Polarization of PBMCs during SARS-CoV-2 Infections

The purpose of the study was to characterize the phenotypic profile of peripheral blood mononuclear cells (PBMCs) in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Peripheral blood samples were collected from patients during the early stages of the pandemic, COVID-19. Venous blood was withdrawn on the day when patients were admitted to the hospital and after seven days. Patients were informed about the purpose of the study. All of them signed a written consent form to confirm their volunteer participation to the study. Collected blood samples prepared on a ficoll gradient were centrifuged at 700xg for 30 minutes to isolate PBMCs. Those cells were stained with fluorescent-labeled antibodies that bind to cell surface markers of PBMCs.  Flow cytometry was conducted to determine the profile of PBMCs. Statistics were conducted by using GraphPad Prism Software.

We found an important (p < 0.05) reduction in T cell populations as well as in natural killer (NK) cells. Particularly, CD8⁺ cytotoxic T lymphocytes were affected severely. In contrast, we did not observe any significant change in B cell populations. We also detected a significant (p < 0.05) increase in both monocytes and neutrophils. Finally, SARS-CoV-2 infection resulted in skewed T helper (Th) responses altering Th1/Th2 and Th17/Treg balances significantly (p < 0.05).

Based on our findings, we concluded that SARS-CoV-2 infection is the main cause for the lymphopenia and significant alterations in the entire PBMC populations. Functional explanations would bring additional information about those mechanisms that lead to the alterations in both myeloid and lymphoid compartments of immune reactions.