Detection of antigenic determinants in the Treponema pallidum membrane protein TmpA using overlapping synthetic peptides.

The antigenic structure of the 42 kDa membrane protein of Treponema Pallidum, TmpA, was studied using synthetic peptides. Ten overlapping peptides, 35-40 residues each, were synthesized in order to cover the entire sequence of the molecule. The antigenic activity of the fragments was examined by enzyme-linked immunosorbent assay (ELISA). In this way it was possible to demonstrate a significant antigenic activity of four peptides which were reactive with syphilitic sera. The N-terminal fragment TmpA1, 38 residues long, proved to be the most reactive. Its antigenic structure was therefore studied in more detail, by examining shorter fragments. The N-terminal portion of TmpA1, consisting of 19 residues, (ASGAKEEAEKKAAEQRALL) represents an important fragment of the molecule, and was specifically interactive with most of the syphilitic sera examined.