Isolation and characterization of TR-c, an antigen of the Reiter treponeme precipitating with antibodies in syphilis.

TR-c is a Reiter treponemal antigen that cross-reacts with an antigen in Treponema pallidum (Nichols pathogenic strain). Sera from patients with secondary syphilis contain precipitating antibodies against TR-c. The isolation of TR-c from a crude bacterial sonicate involves five fractionation steps: anion exchange chromatography (DE-52 Whatman), gel filtration (Ac-A-22, Ultrogel), and affinity chromatography respectively on phenyl-Sepharose CL 4B, iminodiacetic acid-Sepharose CL 4B, and lysine-Sepharose 4B. The purified TR-c was enriched 320 times compared with the starting material, and the recovery was 22%. TR-c was shown to be a protein, it did not bind to a series of lectins, and by gel filtration and polyacrylamide gel electrophoresis (PAGE) and mol. wt was determined to be in the range of 630,000-730,000. It was found by SDS-PAGE to be composed of identical subunits, each having a mol. wt of 48,000. The isolated TR-c was immunochemically pure when tested in crossed immunoelectrophoresis against polyspecific anti-Reiter Ig. The purified TR-c antigen was used for production of a monospecific rabbit antiserum. Monospecific rabbit anti-TR-c gave strong fluorescence with both the Reiter treponeme and T. pallidum.