(Panel A) Relative affinities of V1C7 (circles), V2B9 (squares), V2E8 (triangles), and V5C1 (inverted triangles) for ricin toxin, as determined by ELISA in which ricin was captured onto plastic surface by ASF. (Panel B) Ricin toxin-neutralizing activities associated with the V1C7-like VHHs (symbols as in Panel A), determined in a Vero cell cytotoxicity assay (see Materials and Methods). The values shown are the average (with standard deviation) of two separate experiments each done in triplicate.