T-Cell Immunity in COVID-19-Recovered Individuals and Individuals Vaccinated with the Combined Vector Vaccine Gam-COVID-Vac.

The COVID-19 pandemic has required extensive research on the new coronavirus SARS-CoV-2 and the creation of new highly effective vaccines. The presence of T-cells in the body that respond to virus antigens suggests adequate antiviral immunity. We investigated T-cell immunity in individuals who recovered from mild and moderate COVID-19 and in individuals vaccinated with the Gam-COVID-Vac combined vector vaccine. The ELISPOT method was used to determine the number of T-cells responding with IFN-γ synthesis to stimulation by peptides containing epitopes of the S-protein or N-, M-, ORF3, and ORF7 proteins, using peripheral blood mononuclear cells (PBMCs). At the same time, the multiplex method was used to determine the accumulation of IFN-γ and other cytokines in the culture medium. According to the data obtained, the proportion of positive conclusions about the T-cell immune response to SARS-CoV-2 antigens in control, recovered, and vaccinated individuals was 12%, 70%, and 52%, respectively. At the same time, more than half of the vaccinated individuals with a T-cell response were sensitized to the antigens of N-, M-, ORF3, and ORF7 proteins not produced by Gam-COVID-Vac, indicating a high likelihood of asymptomatic SARS-CoV-2 infection. Increased IFN-γ release by single sensitized T-cells in response to specific stimulation in recovered and vaccinated individuals did not result in the accumulation of this and other cytokines in the culture medium. These findings suggest a balance between cytokine production and utilization by immunocompetent cells as a prerequisite for providing a controlled cytokine signal and avoiding a "cytokine storm".

Von Willebrand Factor and ADAMTS-13 Are Associated with the Severity of COVID-19 Disease.

Coagulopathy in COVID-19 patients is presumably based on systemic hypercoagulation with the inflammatory response. As a result of endothelial dysfunction, tissue factor and von Willebrand factor (vWF) are released into the blood stream, which leads to prothrombinase activation. The vWF/ADAMTS-13 ratio can be used for monitoring the severity of the disease. This observational prospective study included 141 patients with COVID-19. In patients with mild COVID-19 (group 1), the assessment was performed on the 3rd-7th day of illness (point 1) and 14-28 days after recovery (point 2). In patients with moderate (groups 2) and severe (group 3) COVID-19, the assessment was performed during hospitalization (point 1) and after 14 days (point 2). The vWF:RCo/ADAMTS-13:activity (point 1), vWF/ADAMTS-13 (point 2) and vWF:RCo/ADAMTS-13:activity (point 2) ratios were significantly higher in patients with moderate and severe COVID-19. Moreover, in these patients, both ratios increased after recovery (point 2), which is a negative prognostic factor of thrombotic complications. Thus, COVID-19 is characterized by a decrease in the concentration and activity of ADAMTS-13 metalloproteinase, especially in patients with the severe form of COVID-19. A decrease in ADAMTS-13 activity results in an increase in vWF concentration and activity so the ratio of vWF to ADAMTS-13 changes significantly.