Fig. 2: COVID-19 patient sera recognise two linear epitopes in SARS-CoV-2 spike protein.

a Sera of COVID-19 (n = 6) patients at 1:1000 dilution were subjected to peptide-based IgG ELISA using peptide pools covering the entire S protein of SARS-CoV-2 in duplicates. Sera of pooled healthy donors (n = 13) were assessed in parallel. Data are presented as mean patient OD values subtracted of healthy control value are presented, negative values are plotted as zero. b Sera of COVID-19 patients (n = 6) were subjected to peptide-based ELISA for IgG detection using individual peptides of SARS-CoV-2 S peptide pools S14 and S21. The z score values of each patient were calculated using the formula [OD value of patient for peptide−average (OD values of patient)]/standard deviation (OD values of patient). Data shown are from two independent experiments and presented as mean. c Serum peptide binding response of COVID-19 patients on SARS-CoV-2 peptides S14P5 and S21P2, and the corresponding regions on SARS-CoV peptides S45P3 and S51P5, respectively, was determined by ELISA at 1:1000 dilution. Statistical analysis was carried out with paired parametric two-tailed t test (*p < 0.05). d Peptides S14P5 and S21P2 response in 41 COVID-19 patients and 29 healthy controls assessed by ELISA in 1% Triton X-treated plasma fraction at 1:1000 dilution. Data are presented as mean of baseline subtracted OD of two independent experiments and was analysed by Mann–Whitney U test (***p < 0.001). e Spearman correlation of ELISA response from 41 COVID-19 patients to individual peptides from d and sera IC₅₀ neutralisation against SARS-CoV-2 S pseudotyped lentiviruses (Supplementary Table 4) were shown. Line was drawn using non-linear regression with 1/Y² weighting. Source data are provided as a Source Data file.