No abstract

Background Transfusion of SARS‐CoV‐2 convalescent plasma is a promising treatment for severe COVID‐19 cases, with success of the intervention based on neutralizing antibody content. Measurement by serological correlates without biocontainment needs, and an understanding of donor characteristics that may allow for targeting of more potent donors would greatly facilitate effective collection. Study design and methods One hundred convalescent plasma units were characterized for functionally active SARS‐CoV‐2 neutralizing antibodies, as well as for SARS‐CoV‐2 binding antibodies, with the intention to establish a correlation between the functionally more relevant neutralization assay and the more accessible ELISA. Donor demographics such as COVID‐19 disease severity, age and sex were correlated with antibody titers. Results A mean neutralization titer 50% of 1:230 (range < 1:8 – 1:1765) was seen for the 100 convalescent plasma units, with highly significant (p < 0.0001), yet quantitatively limited (R 2 = 0.2830) correlation with results of the ELISA. Exclusion of units with particularly high titers (>1:500) from analysis improved correlation (R 2 = 0.5386). A tendency of higher titer plasma units from donors with increased disease severity, advanced age and of male sex was seen, yet the functional relevance of this difference is questionable. Conclusion The ELISA‐based correlation to neutralization titer enabled a threshold proposal that could be used to eliminate lower titer units from the clinical supply for COVID‐19 treatment. Disease severity may be associated with the development of higher titers of neutralizing antibodies, although larger case numbers will be needed for additional confirmation. This article is protected by copyright. All rights reserved.

19Transfusion of SARS-CoV-2 convalescent plasma is a promising treatment for severe 20 COVID-19 cases, with success of the intervention based on neutralizing antibody content. (neutralization testing) as well as Veronika Sulzer and Sabrina Brandtner (cell culture) are 103 gratefully acknowledged. Andrea Hörl and Hannah Griebler (Center for Virology, Medical 104 University of Vienna) are gratefully acknowledged for ELISA testing. SARS-CoV-2 was 105 sourced via EVAg (supported by the European Community) and kindly provided by Christian 106 Drosten and Victor Corman (

Convalescent plasma (CP) has been in use for the treatment of numerous infectious diseases for more than a century, recently also for coronavirus disease 2019 (COVID-19). A major challenge for this treatment is identifying suitable donors with sufficient levels of functional antibodies and to determine the optimal time span for CP donation. In this retrospective study, we analyzed 189 CP donations of 66 donors regarding anti-SARS-CoV-2 anti-S IgG antibody levels. We found a significant correlation between the semi-quantitative SARS-CoV-2 IgG ratio values and in vitro antibody functionality. A time-to-event analysis allowed us to predict the optimal time span of COVID-19 CP donor suitability. We found that high IgG ratio values, which significantly correlate with high in vitro antibody functionality, were suitable for CP donation for a median of 134 days after the first CP donation. Donors with lower IgG ratios were suitable for a median of 53 days. Our data support plasma collection centers to determine optimal points in time for CP donation by means of widely used semi-quantitative laboratory IgG ratio values.