Kinetics of antibody response to polypeptides of pathogenic and nonpathogenic treponemes in experimental syphilis

Antigenic cross-reactivity between Treponema pallidum subspecies pallidum (TP) and nonpathogenic Treponema phagedenis biotype Reiter (TR), Treponema refringens strain Noguchi (TN), and Treponema vincentii (TV) was examined by the Western immunoblotting technique in pooled sera from five rabbits infected intratesticularly with T. pallidum. Sera were obtained before infection and on days 6, 12, 20, 30, 60, and 120 after infection. The pooled preinfection sera reacted with nine polypeptides of TV, nine of TS, and five of TR. The pooled sera did not show any clear-cut reactions with TP, but some individual rabbit sera did demonstrate visible reaction with three to five polypeptides of TP. Twelve days after infection, multiple serum antibodies reacting with polypeptides of all treponemes were detected. The number of antibodies reacting with polypeptides and the intensity of reaction increased with the duration of infection; for the nonpathogenic treponemes (TV, TS, TR) 21-26 polypeptides were identified on day 30, and by day 60 a total of 21 were detected for TP. By day 120 the reaction had become less pronounced, and fewer reactive polypeptides were seen. The extent of the cross-reactivity with the three nonpathogenic treponemes reflects the complex structure of T. pallidum, which should be viewed as a mosaic of more cross-reacting than strain- or species-specific antigens.