The binding of the GBP-H1a fusion protein onto the surface of a SPR bare gold chip was characterized by SPR measurement using a BIAcore3000 TM with an automatic flow injection system (Biacore AB, Uppsala, Sweden). All experiments were performed in phosphate-buffered saline (PBS, pH 7.4) at room temperature. A fresh SPR sensor chip was attached to a separate chip carrier for easy assembly in the SPR system. After docking and priming of the SPR chip, PBS was used to flush the activated surface and thereby minimize non-specific binding and any unbound sites by removing loosely bound material and dust. All samples were injected onto the gold chip surface at a flow rate of 5 μL/min for 10 min at room temperature using a liquid-handling micropipette in the SPR system. The surface was then washed and equilibrated using PBS. The GBP-H1a fusion protein (50 μL of a 25 μg/mL solution) was injected onto the SPR chip surface. Before binding anti-H1 Ab, 50 μL BSA of 100 μg/mL was injected to block non-specific binding for 10 min. All SPR sensorgrams were fitted globally using BIA evaluation software (Biacore).