Acquisition and processing of sequence data.
A total of 10 whole genome sequences of SARS-CoV-2 (2019-nCoV) were downloaded on 30 January 2020 from the GISAID database 1 
Multiple sequence alignment was conducted on the spike protein sequences of SARS-CoV, MERS-CoV, and SARS-CoV-2 using CLUSTAL W 2 . Next, the pairwise scoring matrix of the distances was computed using Fitch similarity from aligned sequences 3 . And, based on the resulting scoring matrix, phylogenetic tree was constructed using neighbor-joining method 4 .
The sequence-based antibody epitopes score was analyzed using BepiPred-2.0 bioinformatic tool 5 , and the antibody epitope candidates were analyzed using the default threshold value of 0.50. The surface epitope accessibility was computed using Emini surface accessibility scale method 6 . Next, the antibody epitope candidates were filtered by the surface accessible epitopes score using the default threshold value of 1.0 (Fig. 1k) .
The 3-D cryo-electron microscopy structure of the SARS-CoV spike protein complexed with its host cell receptor ACE2 protein were derived from Protein Data Bank (PDB accession: 6ACJ) ) 7 . Next, according to the SARS-CoV-2 spike protein sequence, the Swiss-model bioinformatic tool 8 was used to model the 3-D complex structure of the SARS-CoV-2 spike protein binding to ACE2.
All statistical analyses were performed by using R v3.6.1. Wilcoxon signed-rank for two samples and Kruskal-Wallis test with Dunn's multiple comparison test for multiple samples were performed using the stats package as appropriate. All statistical tests used 0.05 as the significance level, and p ≥ 0.05 were considered as not significant (n.s.), and p < 0.05