FIG. 6.

Binding of serum antibody induced by protective MSP1a/b immunization to Florida strain MSP1b variants. Purified MSP1bF2 (lanes 5), MSP1bF3 (lanes 4), MSP1bF4 (lanes 3), and, as a negative antigen control, B. bigemina RAP-1 (lanes 1) were electrophoresed on SDS-containing polyacrylamide gels and transferred to nitrocellulose. Lane 2 in each gel was unloaded. Membranes were reacted with a 1:2,000 dilution of serum from calf 541 prior to MSP1a/b immunization (right panel), calf 541 after MSP1a/b immunization (center panel), or calf 535, immunized with saponin alone (left panel). The position of the 97-kDa molecular size marker is indicated by a dash to the right of each panel.