A project to develop a state-of-the-art serodiagnostic assay for syphilis with recombinant Treponema pallidum antigens is proposed. The development of recombinant DNA-derived reagents would be of great benefit to the public health agencies, clinical labs, hospitals and blood banks who conduct serodiagnostic tests for syphilis by improving accuracy and lowering the costs of testing. The antigens would be proteins reliably and inexpensively produced from bacteria bearing chimeric DNA. They would readily lend themselves to inclusion in automated diagnostic systems and one-day testing in doctors' offices. It is proposed here to purify antigens expressed by E. coli - T. pallidum recombinant plasmids and evaluate them as serodiagnostic reagents in an experimental immunoassay system. This would test the feasibility of a recombinant-DNA approach. Additionally, it is proposed to explore whether or not these antigens would best be provided by a chimeric-DNA expression vector other than E. coli.