The invention provides novel vectors, attenuated pathogens, compositions, methods and kits for preventing and/or treating chlamydia infections.

Chlamydia trachomatis is an obligate intracellular human pathogen with a unique biphasic developmental growth cycle. It's the etiological agent of trachoma, the world's leading cause of preventable blindness and the most common cause of bacterial sexually transmitted disease. C. trachomatis isolates maintain a highly conserved plasmid and naturally occurring plasmidless clinical isolates are rare, implicating its importance in chlamydial pathogenesis. Understanding the plasmid's role in chlamydial pathogenesis at a molecular level is an important objective for the future control of chlamydial infections. The NIAID inventor had studied chlamydia strains in both non-human primate and murine infectious models providing evidence that plasmids play an important role in chlamydial pathogenesis. In addition, the study results of macaque model of trachoma supports the use of plasmid-deficient organisms as novel live-attenuated chlamydial vaccines.