The hybridoma for mAb 1A9 was previously generated [20]. All mAbs were purified from cell culture supernatants using HiTrap protein G HP affinity columns (GE Healthcare, Chicago, IL, United States) and stored at −80 °C. The purity of the mAb was confirmed by sodium dodecyl sulphate-polyacrylamide gel electrophoretic (SDS-PAGE) analysis. The concentration of the purified mAb was determined using the Coomassie Plus protein assay reagent (Thermo Fisher Scientific).