Characteristics of Products of Fibrinogen Origin in the Presence of Anti- SARS-CoV-2 IgG in the Bloodstream

Background: The hemostasis system has been extensively investigated in patients in the acute phase of coronavirus disease 2019 (COVID-19). In contrast, the post-COVID syndrome is a poorly known entity, and there is a lack of information on the mechanisms underlying the hemostasis abnormalities in the post-COVID period. Aim: To analyze the potential changes in the parameters of the hemostasis system in the post- COVID period in the plasma of donors with different titers of anti-SARS-CoV-2 IgG. Methods: The plasma from 160 donors who had recovered from COVID infection was used in the study. Based on the results of the Abbott SARS-CoV-2 IgG serological assay, all donors were divided into several groups: 5 ± 3 (n = 20); 55 ± 5 (n = 20); 65 ± 5 (n = 20); 75 ± 5 (n = 20); 85 ± 5 (n = 20); 95 ± 5 (n = 20); 125 ± 5 (n = 20); 175 ± 5 (n = 20) Index (S/C). A total of 20 healthy individuals without anti-SARS-CoV-2 IgG constituted the control group. Key laboratory parameters, such as fibrinogen concentrations, soluble fibrin monomer complex (SFMCs), and Ddimer, were investigated. In addition, the qualitative composition of the fraction of SFMCs was analyzed. Results: The slight increase in the concentration of fibrinogen, SFMCs, and D-dimers in some donor groups have been found, which could cause the development of hemostasis disorders. In the fraction of SFMCs, the increase in the number of protein fragments with a molecular weight of less than 250 kDa and an increase in the level of proteins with a molecular weight of more than 270 kDa was revealed. Conclusion: The obtained results indicated the relationship between the changes in the parameters of the hemostasis system and the titers of anti-SARS-CoV-2 IgG in donors in the post-COVID period. It can be assumed that donors with higher titers of anti-SARS-CoV-2 IgG (>55 ± 5 Index (S/C)) are more prone to hemostasis abnormalities in the post-COVID period since a pronounced imbalance in the levels of SFMCs and D-dimer characterizes them. The appearance of protein fragments of different molecular weights in the fraction of SFMC points to uncontrolled activation of biochemical processes involving molecules of fibrinogenic origin. Additional studies are required to elucidate the role of anti-SARS-CoV-2 IgG in the post-COVID period.