Neutralizing peptide ligands selected from phage-displayed libraries mimicthe conformational epitope on domain III of the Japanese encephalitis virus envelope protein

The envelope (E) protein of Japanese encephalitis virus (JEV) contains 500 amino acids with six "conserved" disulfide bonds to maintain its conformati onal structure. Neutralizing epitopes located on the E protein are mostly c onformational dependent. In this study, we used phage-displayed 12-residue combinatorial peptide libraries to select high-affinity peptide ligands bou nd to monoclonal antibody E3.3. The specific peptide ligands presented on t en high-affinity phage clones displayed six different amino acid sequences, all showing a novel cis-proline turn structure. After being superimposed o nto the best fit of the three-dimensional structure of JEV E protein, these peptide structures were mapped to a conformational region constituted by t hree continuous polypeptide segments (E307-E309, E327-E333, E386-E390) in d omain III. Synthetic peptide ligands based on one peptide sequence (E18) we re further investigated using alanine scanning within the cis-proline turn structure to demonstrate its unique molecular characteristics. Our results showed that three residues forming the novel cis-proline turn structure wer e all important in eliciting JEV-specific neutralizing antibodies in mice. (C) 2001 Elsevier Science B.V. All rights reserved.