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) the 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.