Evolution of the RBD-specific IgG associated anti-RBD avidity and ADCC activity in SARS-CoV-2-naive and PI individuals vaccinated with a short or a long interval
(A) SARS-CoV-2 vaccine cohorts design.
(B–E) Indirect ELISAs were performed by incubating plasma samples from naive (B and D) and PI (C and E) donors vaccinated with a short interval (SI) or a long interval (LI) with recombinant SARS-CoV-2 RBD protein. The plasmas were collected at different time points from prior vaccination to after the third dose of mRNA vaccine. Anti-RBD Ab binding was detected using HRP-conjugated anti-human IgG.
(B and C) RLU values obtained were normalized to the signal obtained with the anti-RBD CR3022 mAb present in each plate.
(D and E) The RBD avidity index corresponded to the value obtained with the stringent (8M urea) ELISA divided by that obtained without urea.
(F and G) CEM.NKr parental cells were mixed at a 1:1 ratio with CEM.NKr-S cells and were used as target cells. PBMCs from uninfected donors were used as effector cells in a FACS-based ADCC assay.
(B–G) (Left panels) Each curve represents the values obtained with the plasma of one donor at every time point. (Right panels) The bold lines represent the mean of each group. Naive and PI donors vaccinated with the SI are represented by blue and yellow lines, respectively, and naive and PI donors vaccinated with the LI are represented by red and black lines, respectively. The time of vaccine dose injections is indicated by an associated color syringe. Limits of detection are plotted. Statistical analyses indicate the differences measured between plasma samples from naive donors vaccinated with an SI or an LI (B, D, and F) or PI donors vaccinated with an SI or an LI (C, E, and G), collected between 0 and 100 days post-vaccination (dpv), 101 and 300 dpv, or 300 + dpv (for more details, see Figure S3) (∗∗p < 0.01; ∗∗∗∗p < 0.0001; ns, non-significant). For naive donors vaccinated with the SI, n = 44 at weeks 0, 3, and 26; n = 45 at week 2; n = 46 at weeks 4 and 13; n = 30 at week 39; n = 22 at week 44; n = 35 at week 46; and n = 20 at week 57. For naive donors vaccinated with the LI, n = 25 at weeks 0, 3, and 12; n = 29 at week 19; n = 28 at week 32; n = 20 at week 50; and n = 14 at week 63. For PI donors vaccinated with the SI, n = 13 at weeks 0 and 26; n = 16 at week 2; n = 14 at week 3; n = 15 at weeks 4 and 13; n = 10 at week 39; n = 5 at week 44; n = 11 at week 46; and n = 3 at week 57. For PI donors vaccinated with the LI, n = 10 at week 0; n = 14 at weeks 3 and 32; n = 15 at weeks 12 and 19; and n = 12 at weeks 50 and 63.