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

Wendel, Silvano; Fontão‐Wendel, Rita; Fachini, Roberta; Candelaria, Gabriela; Scuracchio, Patricia; Achkar, Ruth; Brito, Mayra; Reis, Luiz Fernando; Camargo, Anamaria; Amano, Mariane; Machado, Rafael; Araujo, Danielle; Soares, Camila; Durigon, Edison

INTRODUCTION: Little 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 METHODS: A 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). RESULTS: A 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%). CONCLUSION: Selection of CCP donors for multiple collections based on initial high nAb titers (≥1280) or BMI ≥ 30 kg/m(2) 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.