Recombinant peptides fused to domain-1 of the phage pIII coat protein were produced to confirm the specific binding of the 1A3 and 2C7 mAbs to their respective peptides by Western blot and ELISA (Figures S4 and S5 and Figure 1B). Competition-binding assays using pIII-D1-CWSYAVHPEC and pIII-D1-CMPSVILPSC phages as well as their respective synthetic peptides (P1A3 for CWSYAVHPEC and P2C7 for CMPSVILPSC) showed that increased concentrations of the synthetic peptides inhibited the binding of each phage to the 1A3 or 2C7 mAbs (Figure 1C–E), which confirmed their specificities. Additionally, ELISAs with the KLH-derivatized synthetic peptides also indicated specific binding to the 1A3 and 2C7 mAbs (Figure 1F,G). These two synthetic peptides (CWSYAVHPEC and CMPSVILPSC, which were named P1A3 and P2C7) were subsequently tested for biological activity.