Figure 3: Thr50Asn substitution in F2 enables viral escape from F-VHH-4 and F-VHH-L66 neutralization.

F-VHH-4 escape virus (left panel) or RSV A2 (right panel) (25 PFU) was incubated for 30 min at 37 °C with different concentrations of the indicated VHH or mAb before addition to a monolayer of Vero cells. Three days later, cells were fixed and stained with polyclonal anti-RSV serum to visualize the plaques (enumerated in the Y axis).