Developing Peptide Mimotopes of Capsular Polysaccharides and Lipopolysaccharides Protective Antigens of Pathogenic Burkholderia Bacteria.

Burkholderia pseudomallei (BP) and Burkholderia mallei (BM) are two species of pathogenic Burkholderia bacteria. Our laboratory previously identified four monoclonal antibodies (MAbs) that reacted against Burkholderia capsular polysaccharides (PS) and lipopolysaccharides (LPS) and effectively protected against a lethal dose of BP/BM infections in mice. In this study, we used phage display panning against three different phage peptide libraries to select phage clones specifically recognized by each of the four protective MAbs. After sequencing a total of 179 candidate phage clones, we examined in detail six selected phage clones carrying different peptide inserts for the specificity of binding by the respective target MAbs. Chemically synthesized peptides corresponding to those displayed by the six phage clones were conjugated to keyhole limpet hemocyanin carrier protein and tested for their binding specificity to the respective protective MAbs. The study revealed that four of the six peptides, all derived from the library displaying dodecapeptides, functioned well as "mimotopes" of Burkholderia PS and LPS as demonstrated by a high degree of specific competition against the binding of three protective MAbs to BP and BM. Our results suggest that the four selected peptide mimics corresponding to PS/LPS protective antigens of BP and BM could potentially be developed into peptide vaccines against pathogenic Burkholderia bacteria.