Effects of recombinant SARS-CoV-2 spike protein variants on red blood cells parameters and red blood cell distribution width.

We planned a series of experiments to investigate the possible role of spike protein of different SARS-CoV-2 variants in influencing erythrocyte biology. The values of erythrocyte count, hemoglobin, and mean corpuscular hemoglobin (MHC) did not vary across all samples challenged with both concentrations of the four different SARS-CoV-2 recombinant spike proteins. A significant increase in mean corpuscular volume (MCV) was observed with the recombinant SARS-CoV-2 Alpha and Delta spike proteins at both 2 and 20 ng/mL final concentrations. Red blood cell distribution width (RDW) values increased significantly in samples treated with 20 ng/mL of all SARS-CoV-2 recombinant spike proteins and reached the highest values in samples treated with Omicron recombinant spike protein. Blood smear revision evidenced hemagglutination and rouleaux in samples to which recombinant SARS-CoV-2 spike proteins were added, especially in those with Alpha and Delta variants.