BIAcore binding assays.

a) Association (light gray block) and dissociation (dark grey block) profiles for VHH M1 or M5 binding to MD2004 VLP coupled on the sensor surface. VHH M1 concentrations spanned from 45 to 1226 nM and VHH M5 concentrations spanned from 6 to 167 nM. The surface density of VLPs was 3000 RU for both VHHs. Red lines correspond to the fit of a 1:1 (one step) binding model. b) Sequential binding of VHH M1 and VHH M5 to coupled MD2004 VLPs. VHH M1 injected at 450 nM completely inhibited the binding of 5.57 nM. Inhibition was overcome with 150 nM VHH M5. VHH M5 was injected at 450 nM but did not modulate VHH M1 binding as shown in the case of the 5.57 or 150 nM injection of VHH M1. Contact times for both injections were 180 s. The black profiles correspond to the kinetics of binding of VHH (corresponding case) binding to MD2004 while the red profiles highlight the binding profile in the presence of VHH.