Correlation of Body Mass Index (BMI), initial neutralizing antibodies (nAb), ABO group and kinetics of nAb and anti-nucleocapsid (NP) SARS-CoV-2 antibodies in convalescent plasma (CCP) donors – A longitudinal study with proposals for better quality of CCP collections

Introduction A cohort of COVID-19 convalescent volunteers allowed the study of neutralizing (nAb) and ligand antibodies kinetics by providing sequential samples during a median of 100 days after onset of disease. Material and Methods A cohort of previously RT-PCR+ve (detected by nasopharyngeal swab during the acute phase), male convalescent patients, all with mild symptoms, were enrolled on serial blood sample collection for evaluation of longitudinal nAb titers and anti-nucleocapsid (NP) antibodies (IgM, IgG and IgA). 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, after a median of 100 days after the onset of disease, there was a high probability of sustaining nAB titers ≥160 in volunteers whose initial nAb titer was ≥1280, weight ≥ 90kg or BMI classified as overweight or obese, evidenced by Kaplan-Meier estimates and Cox hazard regression. There was no correlation between 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 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 overweight/obese (BMI) 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.