Y. pestis purified F1,V, and F1-V [34] protein antigens were obtained from Brad Powell (USAMRIID, Fort Detrick, Frederick, MD). The 27-peptide array that covered the F1-antigen were 14to 17-mers with 11 amino acid overlaps; they were obtained from the Biodefense and Emerging Infections Research Resources Repository (BEI)(Manassas, VA). The 53-peptide array that covered the V-antigen were 15-to 17-mers with 11 or 12 amino acid overlaps and were obtained from BEI.