Mapping Epitopes Using Phage Display

The epitopes were mapped with purified 1A5 and 1F3 using the Ph.D-12™ Phage Display Peptide Library Kit (New England BioLabs Inc., Ipswich, MA, USA) as previously described [24 (link),25 (link)]. Briefly, each well of a 96-well plate was coated with 10 μg/mL of purified mAb and then blocked with blocking buffer. The phage library was added to the plate and incubated for 1 h. After five washes with Tris-buffered saline (TBS) (50 mM Tris-HCl, 150 mM NaCl; pH 7.5), 1 M Tris-HCl (pH 9.1) was added to the plate [24 (link),25 (link)]. The eluted phages were amplified and titered on lysogeny broth (LB)/isopropyl β-d-1-thiogalactopyranoside (IPTG)/5-bromo-4-chloro-3-indolyl-d-galactoside (X-Gal) plates for selection. Three rounds of biopanning were performed. The ratio of output to input was calculated as the titer of the amplified output phages/the titer of the input phages.