Octet data analysis software version 11

Kinetic binding interactions between Abs and sIL-5Rα were measured using an Octet QKe instrument (ForteBio) (18 (link)). All kinetic experiments were conducted at 30°C with orbital shaking at 1,000 rpm in 200 µl in 96-well black flat-bottom plates (VWR International, 82050-784). Each purified Ab was diluted to 1 μg/ml in 1× kinetics buffer (Fertebio, 18–1,105, diluted with PBS, pH 7.4) and was directly immobilized on anti-human IgG Fc capture (AHC) biosensors (ForteBio, 18–5,060) at an approximately 1.0 nm response. After an equilibration step of 300 s, the binding isotherms were monitored by exposure of separate sensors simultaneously to different concentrations of sIL-5Rα. The association of the antigen was measured for 300 s, followed by a dissociation step lasting 600 s. For all experiments, an empty reference sensor without the sIL-5Rα antigen was utilized to take into account nonspecific binding of the analyte to the sensor. Association and dissociation rate constants were calculated by fitting to sensorgrams via the 1:1 binding model included in the Octet Data Analysis software, version 11.0 (ForteBio).

Before BLI assay, purified EV-D68 18947 viral particles²⁸ were labeled with EZ-Link™ Sulfo-NHS-LC-LC-Biotin (Thermo Fisher Scientific, USA) following manufacturer’s instructions and then purified using Zeba™ spin desalting column (Thermo Fisher Scientific) to remove excess non-reacted biotin. To determine binding affinity of the antibodies to EV-D68, BLI assay was performed in an Octet^® RED96 System (Pall FortéBio, USA) according to manufacturer’s instructions. Briefly, biotinylated EV-D68 18947 virion was immobilized onto streptavidin-coated biosensors (Pall FortéBio) until saturation. The antigen-bound biosensors were placed in wells containing a series of diluted MAb samples to allow antigen-antibody association and were then dipped into dissociation buffer (0.01 M PBS supplemented with 0.1% bovine serum albumin and 0.02% Tween 20). Equilibrium dissociation constants (KD) were calculated using Octet data analysis software version 11.0 (Pall FortéBio).
For competitive binding assay, the immobilized EV-D68 18947 virion were placed in wells containing 30 µg/mL of the first antibody for 500 s (association phase). The sensors were then immersed into wells containing dissociation buffer, 2H12 or 8F12 alone (30 µg/mL; control) or the antibody mixture (30 µg/mL of 8F12 plus 30 µg/mL of 2H12) for 500 s. The data were then analyzed using Octet data analysis software (Pall FortéBio).

To determine the RBD-binding affinities of the MAbs, BLI experiments were carried out on an Octet Red96 instrument (Pall FortéBio, USA). Wild-type RBD or S trimer protein was loaded onto the Ni-NTA biosensors (Pall FortéBio) until saturation. The antigen-coated sensors were moved to wells containing individual MAb samples at varying concentrations for a 500-sec association step and then moved to wells containing dissociation buffer (0.01 M PBS with 0.02% Tween 20 and 0.1% bovine serum albumin) for a 500-sec dissociation step. Data were analyzed using Octet data analysis software version 11.0 (Pall FortéBio).