Correspondence to Author: Alexander Kazimirskii, 

Pirogov Russian National Research Medical University, Ostrovityanova St.1, Moscow 117997, Russian Federation

Abstract:

Post- COVID is characterized by a decrease in the patients’ quality of life, a tendency to hemocoagulation. Symptoms of post- COVID are diverse and difficult to classify. Purpose : Study of neutrophil extracellular traps (NETs) in post-COVID patients to clarify the mechanisms of damage. Patients and methods : Two groups of patients with post COVID were examined. In the first group (21 patients), COVID-19 treatment was carried out in a hospital, in the second group (20 patients) - on an outpatient clinic. The comparison group consisted of 10 patients with acute appendicitis, the control group consisted of 20 healthy people. Neutrophils were isolated using gradient centrifugation. NETs was visualized using fluorescence microscopy with SYBR Green dye (Evrogen; Russia), which specifically interacts with double-stranded DNA. Purine nitrogenous bases (PNB) were determined by the color reaction method based on their interaction with silver nitric acid. Results : In patients with post- COVID treated on an outpatient clinic, the number of NETs (6.55±0.94%) was 7.6 times higher than in patients treated in a hospital (0.86±0.51%), and the tendency to increase the number of symptoms per patient (3.81±0.72) compared to outpatient patients (2.40±1.10), which indicates an effective suppression of the pathological process in the hospital. In all patients with post- COVID, NETs was detected only in the form of single strands of DNA. The concentration of extracellular PNB in the blood plasma of patients with post- COVID for more than 3 months was 7-35 mg / ml. In the comparison group, this index increased briefly (3-5 days) to 0.2-1.8 mg / ml. There are no extracellular PNB in the blood of healthy donors. We believe that patients with post- COVID develop spontaneous enzymatic degradation of DNA strands, which leads to an increase in extracellular PNB. Extracellular PNB are toxic because they can cause cell damage and inhibit the activity of T-lymphocytes, causing secondary immunodeficiency. Conclusion : Virus-induced endothelial damage triggers contact interactions between neutrophils and fibroblasts, which causes neutrophils to form filamentous NETs. Spontaneous degradation of DNA fibers leads to an increase in extracellular PNB, which are factors of secondary alteration and damage endothelial cells and internal organs.

Keywords

post-COVID, neutrophil extracellular traps, NETs, NETs in filamentous form, post-COVID pathogenesis

Citation:

Alexander Kazimirskii. Post-covid syndrome - a model of pathogenesis. Journal of Immunology 2024.