Summary of HX-MS epitopes on RiVax for clusters I to IV. (A) Strongly protected regions for each MAb are shown in a linear representation of the primary sequence of RiVax, aligned with a secondary structure cartoon. Coils denote helices, arrows indicate β secondary structure, and the bulges denote bends. The colored rectangles denote epitopes and are labeled with the corresponding MAb designation. The colors of the rectangles correspond to epitope clusters as denoted in panel B. (B) The strongly protected regions for each cluster are summed over all MAbs belonging to that cluster and shown mapped to the crystal structure of the ricin holotoxin (PDB ID: 2AAI) (14), with each cluster colored as indicated. Where overlaps occurred, they were resolved as follows: cluster III overwrites cluster IV; cluster II overwrites clusters III to IV; and cluster I overwrites clusters II to IV.