Erythrocytes Functionality in SARS-CoV-2 Infection: Potential Link with Alzheimer's Disease

Pathology of Red Blood Cells in Patients with SARS-CoV-2

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been associated with various hematological disorders. Understanding the pathology of erythrocytes (red blood cells) in coronavirus infection may provide insights into disease severity and progression. Objective: To review and analyze the general pathology of erythrocytes in patients infected with SARS-CoV-2, focusing on clinical and laboratory findings across different severity groups. Methods: Patients were classified into four groups based on clinical criteria: Group 1: Regular group (fever, respiratory symptoms, and radiographic evidence of pneumonia). Group 2: Severe group (shortness of breath >30 breaths/min, peripheral blood oxygen saturation <92% at rest, extensive pneumonia, respiratory failure requiring mechanical ventilation, and/or organ failure necessitating intensive care). Group 3: Low saturation group (peripheral blood oxygen saturation <85% at rest). Group 4: Erythroblastosis group (erythroblast count >0.5% among total nucleated blood cells). Clinical laboratory investigations included major routine studies and scanning microspectrophotometry to measure hemoglobin (Hb) spectra in unstained erythrocytes. Results: Erythroblasts were detected in approximately 30% of SARS-CoV-2 patients, predominantly in the severe group. Serum ferritin, C-reactive protein (CRP), and anisocytosis were strongly correlated with disease severity. Microspectrophotometric studies revealed significant changes in hemoglobin adsorption spectra, with an increase in Hb absorbance at 420 nm in severe cases compared to normal controls. Conclusions: Elevated serum ferritin, CRP levels, anisocytosis, and altered hemoglobin absorption at 420 nm wavelength are associated with adverse outcomes in SARS-CoV-2 infection. These findings highlight the potential utility of hematological parameters as markers for disease severity and prognosis in viral infections.

The Ways of the Virus: Interactions of Platelets and Red Blood Cells with SARS-CoV-2, and Their Potential Pathophysiological Significance in COVID-19

The hematological effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are important in COVID-19 pathophysiology. However, the interactions of SARS-CoV-2 with platelets and red blood cells are still poorly understood. There are conflicting data regarding the mechanisms and significance of these interactions. The aim of this review is to put together available data and discuss hypotheses, the known and suspected effects of the virus on these blood cells, their pathophysiological and diagnostic significance, and the potential role of platelets and red blood cells in the virus's transport, propagation, and clearance by the immune system. We pay particular attention to the mutual activation of platelets, the immune system, the endothelium, and blood coagulation and how this changes with the evolution of SARS-CoV-2. There is now convincing evidence that platelets, along with platelet and erythroid precursors (but not mature erythrocytes), are frequently infected by SARS-CoV-2 and functionally changed. The mechanisms of infection of these cells and their role are not yet entirely clear. Still, the changes in platelets and red blood cells in COVID-19 are significantly associated with disease severity and are likely to have prognostic and pathophysiological significance in the development of thrombotic and pulmonary complications.