An ELISA assay was used to assess the binding ability of the Fabs and IgG1s. Briefly, F1-and V-antigens were coated to a Costar high binding 96-well plate (Corning, Corning, NY) and incubated overnight at 4uC. The next day, the plate was blocked with 2% dry milk in PBS before serial dilution of Fabs or IgGs were applied to the plate. After an incubation of the plate at 37uC for one hour, anti-His-horse radish peroxidase (HRP) for Fab detection or anti-human-Fc-HRP (for IgG detection) in PBS+2% dry milk was added to each plate and incubated for another hour at 37uC. The plates were then washed four times, and the ABTS substrate (Roche, Mannheim, Germany) was added. After approximately 10 min at room temperature, the OD405 was taken.