Abstract Purpose: In the present study an antigenmimetic peptide of the anti-JL1 leukemia-specific monoclonal antibody (mAb) was identified and characterized.
Methods: From combinatorial peptide phage display libraries displaying the random linear heptapeptides and dodecapeptides, we selected clones with affinity to antiJL1 mAb through repeated rounds of panning on a mAb-coated ELISA plate. The antigenicity and immunogenicity of the peptide epitopes were then studied using chemically synthesized peptides.

Results:The selected clones had the LXPSIP consensus sequence. Two synthetic peptides LPPSIPFGLTVGGGGS and LLPSIPNQAYLGGGGS specifically reacted with antiJL1 mAb in ELISA.

These two peptides were found to inhibit the interaction between anti-JL1 mAb and JL1 antigen-positive Molt-4 cells. Although the immune sera raised against the keyhole limpet hemocyanin-conjugated peptides failed to react with Molt-4 cells, it showed strong reactivity to the peptide epitope. However, one mAb raised by peptide immunization successfully bound to Molt-4 cells. Conclusion: An epitope-mimetic peptide of anti-JL1 mAb was found using combinatorial peptide phage display libraries. It induced strong humoral response against itself, but only a limited fraction of thishumoral response was cross-reactive with the original JL1 antigen.