Overlapping peptides libraries spanning the entire length of SOX2 were synthesized as previously described[27 (link)]. The SOX2 library consisted of 86 peptides divided into 4 sub-mixes (Supplementary Table 2). M1 peptides cover SOX2 residues 1–89, M2 residues 79–171, M3 residues 161–246 and M4 residues 236–321. A pool of peptides derived from cytomegalovirus, Epstein–Barr virus and influenza virus (CEF; Anaspec Inc.) and Candida albicans (Greer Laboratories Inc.) were used as a positive control.