Probing antinuclear antibody specificities by peptide phage display libraries

Objective To uncover the specificities of autoantibodies to nuclear proteins (ANA) in patients with juvenile rheumatoid arthritis (JRA). Methods Peptide ligands for ANA were selected by panning random peptide phage displ ay libraries on antibodies binding to HEp-2 cells. Positive phage clones we re identified by the immunoscreening technique. Results Groups of peptides were identified, some of which share the core motifs of KTTTnPY, RVADnL/I or RnNSPL. Perinuclear and nuclear staining of HEp-2 cell s were obtained with patient serum antibodies binding to the phage displayi ng the core peptide motifs. In contrast, no significant reactivity was seen with the antibodies binding to the wild type phage. Antibodies to the phag e displaying peptides containing some of the core motifs were detected more frequently in ANA-positive as compared to ANA-negative JRA patients. Homol ogy search with the selected core motifs revealed a significant homology wi th a number of human nuclear proteins and proteins from potential infectiou s agents that could serve as trigger in the breakdown of tolerance. Conclusion Panning of phage display libraries on antibodies reacting with cellular str uctures can lead to the identification of their specificities. Thus, the pe ptide epitopes reported here constitute additional information that may lea d to the development of diagnostic tests and the identification of the pare ntal antigens that initiated the B cell responses in patients with JRA.