Isolation and antigenic characteristics of axial filaments from the Reiter Treponeme

Axial filaments were isolated and purified from Reiter treponemes after detergent solubilization of the cells" outer envelope. The axial filaments were separated from the spirochetal cells by shearing, purified by density gradient centrifugation, and fragmented by ultrasonication. Acrylamide gel electrophoresis of dissociated filaments revealed two major protein bands. Gel diffusion precipitin tests and immunoelectrophoresis between a purified axial filament suspension and anti-Reiter treponeme serum gave a single precipitin line. Checkerboard complement fixation tests also gave results consistent with a single antigen-antibody system. Tests with immune sera to other cultivable spirochetes were positive with some and negative with others. In addition, strongly positive reactions were obtained in complement fixation and precipitin tests with sera from rabbits and humans with syphilis and other treponematoses. However, both serological tests gave reactions of partial identity between the antigen(s) of Reiter treponeme axial filaments and those of the pathogenic treponemes. It was concluded from these studies that the axial filaments were probably the cellular locus of the so-called "Reiter protein" antigen of syphilis serology.