Characterization of 100 sequential SARS‐CoV‐2 convalescent plasma donations

Jungbauer, Christof; Weseslindtner, Lukas; Weidner, Lisa; Gänsdorfer, Simon; Farcet, Maria R.; Gschaider‐Reichhart, Eva; Kreil, Thomas R.

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.