Purification of a Reiter treponemal protein antigen that is immunologically related to an antigen in Treponema pallidum.

A protein antigen called TR-o was isolated from supernatant of a sonically treated Reiter treponeme. The isolation procedure included anion-exchange chromatography on Whatman DE-52, hydrophobic interaction chromatography on decyl agarose, and finally gel filtration on Ac-A-22 Ultrogel. The fractionations were monitored by immunoprecipitation techniques. The recovery was found to be 35%, and the isolated protein was enriched 220 times. The molecular weight of the native protein was estimated to be 550,000 by polyacrylamide gel electrophoresis and 450,000 by gel filtration. Only one 66,000-molecular-weight polypeptide was found by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified protein. The protein was immunologically pure when tested in crossed immunoelectrophoresis against polyspecific rabbit anti-Reiter immunoglobulin, detecting more than 40 treponemal antigens. A monospecific antiserum was raised in rabbits immunized with the purified protein. Monospecific rabbit anti-TR-o gave strong fluorescence with both the Reiter treponeme and Treponema pallidum. The corresponding antigen in T. pallidum could not be demonstrated directly in a crude T. pallidum sonic extract, but rabbit anti-T. pallidum immunoglobulin contained precipitating antibodies against the purified protein. No antibodies against TR-o were found in selected sera from patients with secondary syphilis reactive in traditional syphilis tests.