FIG. 2.

Antibody responses after challenge correlate with treponeme detection. Sera were collected from groups of three rabbits immunized with the N-terminal region of Nichols TprK before and 36 to 41 days after challenge with the Nichols strain (A), clonal Chicago strain (B), or Chicago isolate (C) and were tested in ELISAs against TprK peptides specific for either the Nichols (left) or clonal Chicago (right) strain. (A to C, top graphs) Antibodies from immunized rabbits before challenge recognize conserved and V-region peptides within the Nichols N-terminal immunogen (peptides 1 to 24 shown to the left of the broken lines). (A, bottom panels) Immunized rabbits challenged with the Nichols strain did not develop additional antibodies to peptides in the C terminus of TprK not included in the immunogen (right of the dashed lines). (B, bottom graphs) Immunized rabbits challenged with the clonal Chicago strain produced new antibodies specific for C-terminal Chicago-based peptides. Immunized rabbits challenged with the Chicago isolate produced new antibodies against multiple C-terminal Chicago peptides and only two Nichols-based peptides. (C, bottom graphs). OD405, optical density at 405 nm.