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

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Abstract
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%; the isolated protein was enriched 220 times. The MW of the native protein was estimated to be 550,000 by polyacrylamide gel electrophoresis and 450,000 by gel filtration. Only one 66,000-MW 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 Ig, detecting > 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 T. pallidum. The corresponding antigen in T. pallidum could not be demonstrated directly in a crude T. pallidum sonic extract, but rabbit anti-T. pallidum Ig 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.