RECOMBINANT TREPONEMA-PALLIDUM ANTIGENS IN SYPHILIS SEROLOGY

Treponema pallidum, the etiological agent of syphilis, is characterize d by a paucity of surface exposed outer membrane proteins and a high c ontent of cytoplasma membrane associated lipoproteins. At all stages o f infection intense antibody responses against lipoproteins are detect able. In order to provide antigens for syphilis diagnosis the highly i mmunogenic lipoproteins TpN17, TpN29-35 (TpD), TpN44.5 (TmpA), TpN47, and TpN35 (TmpC) and the membrane protein TpN39 (BMP) were cloned. Ins ertion of PCR amplified DNA into an E. colt expression vector resulted in high level expression of antigens. N-terminal hexahistidine sequen ce allowed efficient purification of fusion proteins by metal chelate affinity chromatography. The recombinant antigens were tested in enzym e-linked immunosorbent assays. TpN17, TpN47, and TpN44.5 antigens show ed high antibody titers. Assays with the three antigens combined resul ted in a further improvement of diagnostic sensitivity in comparison w ith single antigens. Antibodies were found in 17 of 18 patients in all stages of syphilis, whereas 42 normal human sera were nonreactive. No cross-reactivity was detected in 24 sera of patients with Lyme borrel iosis.