A longitudinal study of convalescent plasma (CCP) donors and correlation of ABO group, initial neutralizing antibodies (nAb), and body mass index (BMI) with nAb and anti-nucleocapsid (NP) SARS-CoV-2 antibody kinetics: Proposals for better quality of CCP collections.

Abstract

IntroductionLittle is known about the neutralizing (nAb) and binding antibody kinetics in COVID‐19 convalescent plasma donors, especially during the first 100 days after disease onset.Materials and MethodsA cohort of previously RT‐PCR positive (detected by nasopharyngeal swab during the acute phase), male convalescent patients, all with mild symptoms, were enrolled in serial blood sample collection for a longitudinal nAb titers and anti‐nucleocapsid (NP) antibodies (IgM, IgG and IgA) evaluation. NAbs were detected by a cytopathic effect‐based virus neutralization test (CPE‐based VNT), carried out with SARS‐CoV‐2 (GenBank: MT350282).ResultsA total of 78 male volunteers provided 316 samples, spanning a total of 4820 days of study. Although only 25% of donors kept nAb titers ≥160 within 100 days after the onset of disease, there was >75% probability of sustaining nAb titers ≥160 in volunteers whose initial nAb titer was ≥1280, weight ≥ 90 kg or obese, according to their body mass index (BMI), as evidenced by Kaplan–Meier analysis and Cox hazard regression (all p < .02). There was no correlation between the ABO group, ABO antibody titers and persistent high nAb titers. High IgG anti‐NP (S/CO ≥5.0) is a good surrogate for detecting nAb ≥ 160, defined by the ROC curve (sensitivity = 90.5%; CI95%: 84.5%–94.7%).ConclusionSelection of CCP donors for multiple collections based on initial high nAb titers (≥1280) or BMI ≥ 30 kg/m2 provides a simple strategy to achieve higher quality in CCP programs. High IgG anti‐NP levels can also be used as surrogate markers for high nAb screening.