Waning of SARS-CoV-2 RBD antibodies in longitudinal convalescent plasma samples within 4 months after symptom onset

Abstract

There is a Blood Commentary on this article in this issue.

Figure 1.

Longitudinal analysis of the anti-RBD antibody response in 15 repeat CCP donors. Males and females with no history of pregnancy who recovered from a diagnosed COVID-19 infection were invited to donate plasma after informed consent. A volume of 500 to 750 mL plasma was collected by plasmapheresis (TRIMA Accel; Terumo BCT). Donors were allowed to donate plasma units every 6 days, for a maximum of 12 weeks. The level of anti-RBD antibodies was determined in our semiquantitative in-house ELISA (see supplemental Methods), using a 1:100 dilution of plasma. (A) Each curve represents the mean OD_450nm ± SD obtained with the plasma of 1 donor at every donation (4-9 donations per donor) as a function of the days after symptom onset. The dotted line represents the cutoff value of the ELISA; some donors became seronegative at their last donation. (B) Same results but presented as the relative anti-RBD antibody level calculated at each time point using the first time point as reference: 1 − [OD_450nm at each donation/OD_450nm at first donation] × 100. (C) Correlation between the number of donations by each donor and the overall decline in anti-RBD level calculated using the following formula: 1 − [OD_450nm at the last donation/maximal OD_450nm obtained] × 100. (D) Correlation between the number of days between symptom onset and the last donation with the overall decline in anti-RBD level for each donor.

Figure 2.

Evolution of the anti-RBD antibody response over time in repeat CCP donors. The time from onset of symptoms (33-114 days) was divided in quartiles containing similar numbers (between 19 and 22) of samples obtained from the donors shown in Figure 1. The mean and median OD_450nm were calculated using all samples in each quartile. Each sample is represented by a dot. Boxes and horizontal bars denote IQR, whereas horizontal line and lozenge in boxes correspond to median and mean value, respectively. Whisker end points are equal to the maximum and minimum values below or above the median ± 1.5 times the IQR. Statistical significance was noted as not significant (NS). *P < .05; **P < .01; and ***P < .001.