The invention discloses the Chlamydia PMPE and PMPI polypeptide, polypeptides derived therefrp, (PMP-derived polypeptides), nucleotide sequences encoding said polypeptides, antibodies that specifically bind the PMP polypeptides and PMP-derived polypeptides and T-cells specific for PMP polypeptides and PMP-derived polypeptides. Also disclosed are prophylactic and therapeutic compositions, including immunogenic compositions, e.g., vaccines, comprising PMP polypeptides or PMP-derived polypeptides or antibodies thereto. The invention additionally discloses methods of inducing in animals an immune response to Chlamydia cells, Chlamydia elementary bodies, and/or cells expressing Chlamydial proteins, e.g., cell infected with Chlamydia.