Reiter's protein complement-fixation test; report of a trial in 1,000 unselected cases.

In recent years there has been a tendency to experiment with antigens derived from treponemata in the diagnostic tests for treponemal disease in the hope that they might prove more sensitive and more specific than the cardiolipin antigen which is now the standard preparation. These antigens have been prepared either from a virulent strain of Treponema pallidum or from the avirulent Reiter strain, which is said to have been originally derived from a virulent Treponema pallidum (Ruge, 1956). The preparation of antigens from virulent Treponema pallidum involves the maintenance and handling of infected rabbits, a task which routine laboratories would prefer to avoid. The Reiter treponeme, however, grows readily in vitro and is convenient to handle. Tests using the Reiter strain have been of two types: (1) Those in which the whole treponeme has formed the antigen. (2) Those in which a protein extract of the treponeme has been used. D'Alessandro and Dardanoni (1953) have shown that at least four antigenic fractions of the Reiter treponeme can be prepared: (1) A protein antigen, (2) A lipid antigen which has the same specificity as cardiolipin, (3) A further lipid antigen, (4) A polysaccharide antigen. The protein antigen was more sensitive than the whole treponeme when titrated with the serum of experimentally-infected animals and showed no reaction with an antibody prepared against cardiolipin. Sera from syphilitic patients also reacted to a higher titre with the protein antigen than with cardiolipin. However, the antibody involved in the Reiter protein complement-fixation test (RPCFT)