Reiter protein antigen. I. Relationship of some physical and chemical characteristics to serological activity.

The Italian workers D'Alessandro, Oddo, Comes, and Dardanoni (1949) and D'Alessandro and Dardanoni (1953) described the isolation of four serologically active components of Reiter's treponeme. These contributions represent milestones in the sero-diagnosis of syphilis since they were the initial systematic investigations into the serological components of treponemes. One of the components was considered to be a soluble protein and was identified by the letters "ATPS"-antigene treponemico proteico solubile. ATPS was shown to be serologically active when employed as antigen in a complement fixation test. In the present report ATPS is designated "Reiter protein antigen" or "Reiter protein" to specifically identify the treponemal source. Several clinico-serological evaluations have demonstrated that, when used in certain complement-fixation techniques, Reiter protein provides a highly specific antigen in a serological test for syphilis (Wallace and Harris, 1962). The use of the antigen in complement-fixation testing of clinical specimens has been designated the Reiter protein complement-fixation (RPCF) (Cannefax and Garson, 1957) and the Kolmer Reiter protein (KRP) test (Bossak, Falcone, Duncan, and Harris, 1958). During the developmental phase of RPCF testing and antigen preparation, it was observed that the antigenic titre of several lots of Reiter protein was relatively constant from lot to lot. However, it was observed that there were physical, chemical, and certain serological differences between individual lots of Reiter protein prepared from organisms grown under identical cultural conditions and strict adherence to the D'Alessandro method of protein isolation. These differences were manifested by the presence or absence of zoning in the antigen titration, differences in the optical density, and variability of protein concentration with respect to an almost