Chlamydia trachomatis is an obligate intracellular bacterial pathogen that causes blinding
trachoma and
sexually transmitted disease afflicting hundreds of millions of people globally. A fundamental but poorly understood pathophysiological characteristic of chlamydial
infection is the propensity to cause
persistent infection that drives damaging inflammatory disease. The chlamydial plasmid is a
virulence factor, but its role in the pathogenesis of
persistent infection capable of driving immunopathology is unknown. Here, we show by using mouse and nonhuman primate
infection models that the secreted plasmid gene
protein 3 (Pgp3) is essential for establishing
persistent infection. Ppg3-dependent persistent
genital tract infection resulted in a severe
endometritis caused by an intense infiltration of endometrial submucosal macrophages. Pgp3 released from the cytosol of lysed infected oviduct epithelial cells, not organism outer membrane-associated Pgp3, inhibited the chlamydial killing activity of
antimicrobial peptides. Genetic Pgp3 rescue experiments in
cathelin-related antimicrobial peptide (
CRAMP)-deficient mice showed Pgp3-targeted
antimicrobial peptides to subvert innate immunity as a pathogenic strategy to establish
persistent infection. These findings provide important advances in understanding the role of Pgp3 in the pathogenesis of persistent chlamydial
infection and associated immunopathology.IMPORTANCEChlamydia trachomatis can cause
persistent infection that drives damaging inflammatory responses resulting in
infertility and
blindness. Little is known about chlamydial genes that cause persistence or factors that drive damaging pathology. In this work, we show that the C. trachomatis plasmid
protein gene 3 (Pgp3) is the essential
virulence factor for establishing persistent female genital tract
infection and provide supportive evidence that Pgp3 functions similarly in a nonhuman primate
trachoma model. We further show that persistent Ppg3-dependent
infection drives damaging immunopathology. These results are important advances in understanding the pathophysiology of chlamydial persistence.