properties of the COVID-19 convalescent plasma

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.