Kinetics of neutralizing antibodies (nAb) SARS-CoV-2 and anti-nucleocapsid (NP) antibodies in convalescent plasma donors

Background/Case Studies: COVID-19 convalescent plasma (CCP) has been used for therapy in severely affected COVID-19 patients The rational relies on the presence of nAb in convalescent's bloodstream, which might suppress patient's viremia Little is known about the nAb kinetics in CCP donors Study Design/Methods: A cohort of previously RTPCR+ ve, male, volunteer, non-remunerated, mild convalescent donors has been studied, based on serial virus neutralization tests (CPE-based VNT, GenBank: MT MT350282, transformed in natural log) and specific IgM, IgG and IgA anti-nucleocapsid protein (NP) SARS-CoV-2 ELISA, depicted as signal/cutoff (S/CO) Results/Findings: A total of 63 donors were evaluated within a period ranging from 14-97 days after full recovery of symptoms (DARS) There was initially a decline in nAb and IgA anti-NP from the first to third collection (median = 45days), followed by an unexpected rise in two additional collections No differences were seen for IgM and IgG anti-NP Data are shown below, with statistical values between subsequent samples Conclusions: There is a great variability in nAb titers, with a declining trend over time Although this was clear during the first three collections, the sudden rise could be explained by biological nAb fluctuation or by viral re-exposure after recovery, due to contact with infected people (pandemic still active in our region) Although IgA anti-NP shows a wide range, its declining trend could be signaling a possible role of IgA as an important component of nAb Further studies are required to better understand the kinetic behavior of these antibodies