CHARACTERIZATION OF 2 CONFORMATIONAL EPITOPES OF THE CHLAMYDIA-TRACHOMATIS SEROVAR L2 DNAK IMMUNOGEN

Chlamydia trachomatis DnaK is an important immunogen in chlamydial inf ections. DnaK is composed of a conserved N-terminal ATP-binding domain and a variable C-terminal peptide-binding domain. To locate the immun ogenic part of C. trachomatis DnaK, we generated monoclonal antibodies (MAbs) against this protein. By use of recombinant DNA techniques, we located the epitopes for two MAbs in the C-terminal variable part. Al though the antibodies reacted in an immunoblot assay, it was not possi ble to map the epitopes completely by use of 16-mer synthetic peptides displaced by one amino acid corresponding to the C-terminal part of C . trachomatis DnaK. To determine the limits of the epitopes, C. tracho matis DnaK and glutatione S-transferase fusion proteins were construct ed and affinity purified. The purified DnaK fusion proteins were used for a fluid-phase inhibition enzyme-linked immunosorbent assay with th e two antibodies. The epitopes were found not to overlap. To obtain Dn aK fragments recognized by the antibodies with the same affinity as na tive C. trachomatis DnaK, it was necessary to express, respectively, r egions of 127 and 77 amino acids. The MAbs described in this study thu s recognized conformational epitopes of C. trachomatis DnaK.