Purification of TR-b, a Reiter treponeme protein antigen precipitating with antibodies in human syphilitic sera.

TR-b is a Reiter treponeme antigen, cross-reacting with an antigen in Treponema pallidum (Nichols pathogenic strain). Sera from patients with secondary syphilis contain precipitating antibodies against TR-b. The isolation of TR-b from a bacterial sonic extract is described here. It involved five fractionation steps: anion-exchange chromatography (DE-52 Whatman), gel filtration (Ac-A-22 Ultrogel), and affinity chromatography on phenyl-Sepharose CL 4B, iminodiacetic acid-Sepharose CL 4B, and lysine-Sepharose 4B, respectively. The purified TR-b was enriched 199 times compared with the starting material, and the recovery was 12%. TR-b was shown to be a protein; it did not bind to a series of lectins, and by gel filtration and polyacrylamide gel electrophoresis, the molecular weight was determined to be 610,000 to 630,000. It was found by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be composed of identical 70,000-dalton subunits. The isolated TR-b was immunologically pure when tested in crossed immunoelectrophoresis against polyspecific anti-Reiter immunoglobulin. The purified TR-b antigen was used for the production of a monospecific rabbit antiserum, giving strong fluorescence with both the Reiter treponeme and T. pallidum in an indirect immunofluorescence test.