Plasmid-Cured Chlamydia caviae Activates TLR2-Dependent Signaling and Retains Virulence in the Guinea Pig Model of Genital Tract Infection

Lauren C Frazer,Kumar Chandra-Kuntal,Margaret Mintus,Matthew Zurenski,Yasser M Abdelrahman,Robin R Ingalls,Robert J Belland,Toni Darville,Catherine M O'Connell,Charles W Andrews,Kathleen A Kelly

doi:10.1371/journal.pone.0030747

Abstract

Loss of the conserved “cryptic” plasmid from C. trachomatis and C. muridarum is pleiotropic, resulting in reduced innate inflammatory activation via TLR2, glycogen accumulation and infectivity. The more genetically distant C. caviae GPIC is a natural pathogen of guinea pigs and induces upper genital tract pathology when inoculated intravaginally, modeling human disease. To examine the contribution of pCpGP1 to C. caviae pathogenesis, a cured derivative of GPIC, strain CC13, was derived and evaluated in vitro and in vivo. Transcriptional profiling of CC13 revealed only partial conservation of previously identified plasmid-responsive chromosomal loci (PRCL) in C. caviae. However, 2-deoxyglucose (2DG) treatment of GPIC and CC13 resulted in reduced transcription of all identified PRCL, including glgA, indicating the presence of a plasmid-independent glucose response in this species. In contrast to plasmid-cured C. muridarum and C. trachomatis, plasmid-cured C. caviae strain CC13 signaled via TLR2 in vitro and elicited cytokine production in vivo similar to wild-type C. caviae. Furthermore, inflammatory pathology induced by infection of guinea pigs with CC13 was similar to that induced by GPIC, although we observed more rapid resolution of CC13 infection in estrogen-treated guinea pigs. These data indicate that either the plasmid is not involved in expression or regulation of virulence in C. caviae or that redundant effectors prevent these phenotypic changes from being observed in C. caviae plasmid-cured strains.

Highlights

Chlamydiaceae are gram-negative obligate intracellular pathogens that infect ocular, genital and respiratory tissues in both humans and animals
This high degree of genetic-relatedness extends to carriage of a 7.5 kb ‘‘cryptic’’ plasmid by Chlamydia trachomatis, C. muridarum, C. psittaci, C. felis, strains of C. pneumoniae that do not infect humans and C. caviae
Plasmid-deficient C.caviae CC13 displays normal infectivity L929 cells infected with C. caviae guinea pig inclusion conjunctivitis (GPIC) were treated with novobiocin (62.5 mg/ml) and plated in a plaque assay as previously described for curing of the plasmid from C. muridarum [3]

Summary

Introduction

Chlamydiaceae are gram-negative obligate intracellular pathogens that infect ocular, genital and respiratory tissues in both humans and animals. The genomes of chlamydial species are highly conserved, which likely reflects the specific requirements of intracellular pathogens for survival and the limited opportunity for genetic exchange with other bacterial pathogens within this intracellular niche (reviewed by Stephens et al [1]). This high degree of genetic-relatedness extends to carriage of a 7.5 kb ‘‘cryptic’’ plasmid by Chlamydia trachomatis (human), C. muridarum (mice), C. psittaci (birds), C. felis (cats), strains of C. pneumoniae that do not infect humans and C. caviae (guinea pigs). We demonstrated that these phenotypic changes are conserved in plasmid-cured C. trachomatis and identified a number of PRCL that, in addition to plasmid-encoded gene products, are candidate effectors of these virulence properties [8]

Methods

Results

Conclusion