SURFACE-ASSOCIATED ANTIGENS OF TREPONEMA-PALLIDUM CONCEALED BY AN INERT OUTER LAYER

Abstract

Soluble antigens of T. pallidum were examined by 2 dimensional immunoelectrophoresis against antisera from infected or artificially immunized rabbits. Concentrated suspensions of intact cells did not release antigens after storage at 4.degree., incubation at 37.degree. or vortex mixing. Antigens were released after disintegration of treponemes by ultrasonic vibration or by treatment with non-ionic or anionic detergents. An antigenic component of sonicated treponemes, present in both the non-pathogenic, cultivable Reiter treponeme and T. pallidum, was identified as axial filament. The combination of antibody with unfixed whole organisms was monitored by an indirect fluorescent antibody method; whereas antibody did not combine with intact organisms, detergent-treated organisms were highly reactive. Immune-EM showed that whereas in intact treponemes, axial filaments were unable to combine with antibody, detergent treatment allowed access to axial filaments by antibody. In intact treponemes the axial filaments are thought to be located beneath the outer membrane, which may thus comprise the postulated antigenically inert outer layer.