HLA-B27 BINDING PEPTIDES DERIVED FROM THE 57 KD HEAT-SHOCK PROTEIN OFCHLAMYDIA-TRACHOMATIS - NOVEL INSIGHTS INTO THE PEPTIDE BINDING RULES

In this study we investigate the 57 kD heat shock protein of Chlamydia trachomatis for potential HLA-B27 restricted T cell epitopes. This pr otein is known to elicit T cell immunity, as judged by delayed type hy persensitivity. We synthesized 24 peptides containing the B27 anchor a mino acid arginine at position 2, according to the rules previously de scribed for peptide binding to MHC class I molecules. The nonamer pept ides were tested in an in vitro assembly assay; six out of the 24 pept ides bind to HLA-B27 although their sequences only partially match the HLA-B27 binding motif. Two of these six peptides carry negatively cha rged amino acids which apparently fit into the P1 pocket and in three out of the six a positively charged amino acid fits into the P3 pocket . In addition, two octamer peptides stabilized the HLA-B27 molecule wi thout containing an appropriate amino or carboxy terminus. Therefore o ur data suggest that current binding rules will need to be refined bef ore they can be used to accurately predict potential T cell epitopes. Furthermore our HLA-B27-binding peptides should prove useful probes fo r the study of the processing and presentation of this bacterial antig en, and of changes in the T cell repertoire induced by this form of in fection.