Uses of the plasmid-encoded protein pgp3 from C. trachomatis, serotype D, purified by ion exchange column chromatography and shown to be suitable for quantitative immunoassay on clinical samples in an ELISA format, in methods of eliciting and diagnosing an immune response are described.
1. A method of eliciting an immune response in a subject to a recombinant Chlamydia trachomatis pgp3 protein comprising administering to the subject an effective amount of an isolated and purified recombinant Chlamydia trachomatis pgp3 protein having its native amino acid conformation, wherein the recombinant Chlamydia trachomatis pgp3 protein is recognized by antibodies against pgp3 conformational epitopes.
2. The method of claim 1 wherein the subject is a human.