Figure 3.

Antigenic reactivity of synthetic peptides with comirnaty vaccine recipient sera. Serum samples from an infection-naïve individual who received comirnaty vaccine in a 2-dose regimen were collected at 0.5 month or 2 months after the injection of a second dose. A pool of ten infection-naïve individuals collected in 2019 (Table S3) served as negative control serum. In (A), serum samples at dilution 1:100 were assessed for the detection of antibodies against SARS-CoV-2 N and S proteins by indirect ELISA using soluble rN and rRBD proteins for antigen-based antibody capture. The intensity values of serum samples were measured at O.D. 450 nm. The results are the mean (± SEM) of three replicates. Statistical comparisons were performed between serum samples. Statistically significant comparisons are shown as * p < 10^–4 (ns: non-statistically significant, p > 0.05). In (B), the serum samples were assayed at dilution 1:50 on synthetic peptides and their variants (200 ng.ml⁻¹) through synthetic peptide-based ELISA. The intensity values of vaccine serum sample were measured at O.D. 450 nm. The results are the mean (± SEM) of three replicates. Pairwise comparisons between peptides showed that the experimental points for S1P4 and S2P6 peptides are significantly different from the other peptides (** p < 10^–4, * p < 10^–3). The differences between 0.5 month and 2.0 month for the synthetic S1P4 and S2P6 peptides are non-statistically significant (ns, p > 0.05).