Biolayer interferometry (BLI).

BLI experiments were performed on an OctetRed 96 system (FortéBio). All samples were diluted with the Octet buffer (DPBS with 0.05% Tween-20 and 0.1% BSA), and assays were performed under agitation (1000 rpm). mAbs (200 nM) were loaded onto anti-human IgG Fc capture (AHC) Biosensors (FortéBio) and then dipped into antigen solutions (150–200 nM) for binding analysis, followed by dissociation into the Octet buffer. Alternatively, biotinylated antigens (200 nM) were loaded onto Streptavidin biosensors (Sartorius) and then dipped into antibody solutions (200 nM) for binding analysis, followed by dissociation into the Octet buffer. Serial dilutions of Fabs were used to measure the affinity (K_D) for biotinylated antigens. Data were processed by Data Analysis software (version 9.0.0.15, FortéBio) and then plotted. Shifts in nanometers of mAb-binding to wild-type proteins were used as the maximal binding value (1.0) and shifts from oligoD-modified proteins were normalized as a fraction of the maximal binding value.