Figure 2: Prokaryotic expression, purification and identification of VP1. The vector pET-28a-VP1 was transformed into E. coli strain BL21, and GST-VP1 was expressed and purified on a GST-affinity column, and then analyzed by western blot. A. SDS-PAGE detection of unpurified (lane 1) and purified (lane 2) VP1 protein, 37 kDa in size. B. Western blot analysis of VP1 using sera from mice challenged with EV71 (lane 1), mice immunized with expressed VP1 (lane 2), and a commercialized VP1 polyclonal antibody (lane 3).