Analysis of presence and short-term persistence of SARS-CoV-2 neutralizing antibodies in COVID-19 convalescent plasma donors

In March 2020, the FDA approved the use of COVID-19 convalescent plasma (CCP) as an investigational new drug for treatment of COVID-19. Since then, collection of CCP from COVID-19 recovered patients has been implemented in several donor centers across the country. Children’s Hospital Colorado rapidly put into practice a CCP collection protocol, necessitating the development and implementation of assays to evaluate SARS-CoV-2 antibodies in CCP units. We evaluated 87 separate units of CCP collected from 36 donors over two to four sequential donations using both antigen- binding assays for SARS-CoV-2 nucleoprotein and spike antigens, and a live virus focus reduction neutralization test (FRNT50). Our data shows that the majority of donors (83%) had a FRNT50 titer of 1:80 or greater, and 61% had a titer ≥ 1:160, which meet the FDA’s criteria for acceptable CCP units. Additionally, our data indicates that analysis of antibodies to a single SARS-CoV-2 antigen is likely to miss a percentage of seroconverters; however, these individuals tend to have neutralizing antibody titers of <1:80. Of note, there was considerable variability in the short term, sustained antibody response, measured by neutralizing antibody titers, among our donor population. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by the Department of Pediatrics, the Department of Immunology and Microbiology, University of Colorado School of Medicine and Childrens Hospital, Colorado. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Colorado Multiple Institutional Review Board (COMIRB) All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data included in this manuscript was generated at Children's Hospital, Colorado and the University of Colorado School of Medicine