Babesiosis and Sickle Red blood Cells: Loss of Deformability, Heightened Osmotic fragility, and Hypervesiculation.

Abstract

Babesiosis in sickle cell disease (SCD) is marked by severe anemia but the underlying red blood cell (RBC) rheological parameters remain largely undefined. Here, we describe altered RBC deformability from both primary (host RBC sickle hemoglobin mediated) and secondary changes (Babesia parasite infection mediated) to the RBC membrane using wild type AA, sickle trait AS and sickle SS RBCs. Our ektacytometry (LORRCA) analysis demonstrates that the changes in the host RBC bio-mechanical properties, pre- and post- Babesia infection, reside on a spectrum of severity, with wild type infected AA cells, despite showing a significant reduction of deformability under both shear and osmolarity gradients, exhibiting only a mild phenotype; compared to infected AS RBCs which show median changes in deformability and infected SS RBCs which exhibit the most dramatic impact of infection on cellular rheology, including an increase in Point of Sickling values. Further, using Image stream cytometric technology to quantify changes in cellular shape and area along with a tunable resistive pulse sensor to measure release of extra-cellular vesicles (EV) from these host RBCs, before and after infection, we offer a potential mechanistic basis for this extreme SS RBC rheologic profile, which include enhanced sickling rates and osmotic fragility, loss of RBC surface area and hypervesiculation in infected SS host RBCs. These results underly the importance of understanding the impact of intra-erythrocytic parasitic infections of SCD RBCs, especially on their cellular membranes and studying the mechanisms that lead to hyper hemolysis and extreme anemia in the SCD patient population.