Background and Objectives In the absence of a vaccine or specific antiviral drugs against SARS-CoV-2 COVID-19 convalescent plasma became one of the experimental treatment options in many countries. Aim of this study was to assess the impact of different pathogen reduction technologies on the immunological properties of COVID-19 convalescent plasma. Materials and Methods In our experiment 140 doses of plasma collected by plasmapheresis from COVID-19 convalescent donors were subjected to pathogen reduction with one of three different methods: methylene blue (M), riboflavin (R), and amotosalen (A). To conduct a paired two-sample comparison each plasma dose was divided into 2 that were treated by one of these technologies. The titres of SARS-CoV2 neutralizing antibodies (NtAbs) and levels of specific immunoglobulins to RBD, S- and N- proteins of SARS-CoV-2 were measured before and after pathogen reduction. Results All methods reduced NtAbs titers significantly but not at the same grade: among units with the initial titre 80 or above, 81% of units had unchanged titres while 19% decreased by 1 step after methylene blue; 60% unchanged and 40% - decreased by 1 step after amotosalen; 43% unchanged, 67% a one-step decrease and 6% - a two-step decrease after riboflavin. Pairwise two-sample comparisons (M vs A, M vs R and A vs R) revealed the most prominent and statistically significant decrease in all studied parameters (except anti-RBD) following pathogen reduction with riboflavin. Conclusion Pathogen reduction with amotosalen and methylene blue provides the greater likelihood of preserving the immunological properties of the COVID-19 convalescent plasma compared to riboflavin.

The aim of this study was to identify single nucleotide variants in genes associated with susceptibility to or severe outcomes of COVID-19. A total of 319 genomic DNA samples from patients with varying degrees of disease severity and 78 control DNA samples from people who had regular or prolonged contact with patients with COVID-19 but did not have clinical manifestations and/or antibodies to SARS-CoV-2. Seven SNPs were identified that were statistically associated with disease risk or severe course, rs1799864 in the CCR2 gene (OR = 2.21), rs1990760 in the IFIH1 gene (OR = 2.41), rs1800629 in the TNF gene (OR = 1.98), rs75603675 in the TMPRSS2 gene (OR = 1.86), rs7842 in the C3AR1 gene (OR = 2.08), rs179008 in the gene TLR7 (OR = 1.85), rs324011 in the C3AR1 gene (OR = 2.08), rs179008 in the TLR7 gene (OR = 1.85), and rs324011 in the STAT6 gene (OR = 1.84), as well as two variants associated with protection from COVID-19, rs744166 in the STAT3 gene (OR = 0.36) and rs1898830 in the TLR2 gene (OR = 0.47). The genotype in the region of these markers can be the criterion of the therapeutic approach for patients with COVID-19.

Conclusion Pathogen reduction with methylene blue or with amotosalen provides the greater likelihood of preserving the immunological properties of the COVID-19 convalescent plasma compared to riboflavin.

Vaccination against COVID-19 has occurred in Russia for more than two years. According to the Russian official clinical guidelines to maintain tense immunity in the conditions of the ongoing COVID-19 pandemic, it is necessary to use booster immunization six months after primary vaccination or a previous COVID-19 contraction. It is especially important to ensure the maintenance of protective immunity in the elderly, who are at risk of severe courses of COVID-19. Meanwhile, the immunological effectiveness of the booster doses has not been sufficiently substantiated. To investigate the immunogenicity of Sputnik V within the recommended revaccination regimen and evaluate the effectiveness of booster doses, we conducted this study on 3983 samples obtained from individuals previously vaccinated with Sputnik V in Moscow. We analyzed the level of antibodies in BAU/mL three times: (i) six months after primary immunization immediately before the booster (RV), (ii) 3 weeks after the introduction of the first component of the booster (RV1), and (iii) 3 weeks after the introduction of the second component of the booster (RV2). Six months after the primary vaccination with Sputnik V, 95.5% of patients maintained a positive level of IgG antibodies to the receptor-binding domain (RBD) of SARS-CoV-2. The degree of increase in the specific virus-neutralizing antibodies level after revaccination increased with a decrease in their initial level just before the booster dose application. In the group of people with the level of antibodies up to 100 BAU/mL six months after the vaccination, a more than eightfold increase (p < 0.001, Wilcoxon criterion with Bonferroni adjustment) in the level of specific antibodies was observed (Me = 8.84 (IQR: 3.63–30.61)). A significant increase in the IgG level after receiving both the first and the second booster doses occurred at the initial titer level up to 300 BAU/ mL (p < 0.001) in those who did not contract COVID-19 in the past and up to 100 BAU/mL (p < 0.001) in those who were previously infected with SARS-CoV-2. A significant increase in the antibody level after the first dose of the booster was noted for people who had up to 500 BAU/mL (p < 0.05), regardless of the previous COVID-19 infection. Thus, revaccination is most effective in individuals with an antibody level below 500 BAU/mL, regardless of the vaccinee age and COVID-19 contraction. For the first time, it has been shown that a single booster dose of the Sputnik vaccine is sufficient to form a protective immunity in most vaccinees regardless of age and preexisting antibody level.