Polymorphisms in Chlamydia trachomatis tryptophan synthase genes differentiate between genital and ocular isolates.
We previously reported that laboratory reference strains of Chlamydia trachomatis differing in infection organotropism correlated with inactivating mutations in the pathogen's tryptophan synthase (trpBA) genes. Here, we have applied functional genomics to extend this work and find that the paradigm established for reference serovars also applies to clinical isolates - specifically, all ocular trachoma isolates tested have inactivating mutations in the synthase, whereas all genital isolates encode a functional enzyme. Moreover, functional enzyme activity was directly correlated to IFN-gamma resistance through an indole rescue mechanism. Hence, a strong selective pressure exists for genital strains to maintain a functional synthase capable of using indole for tryptophan biosynthesis. The fact that ocular serovars (serovar B) isolated from the genital tract were found to possess a functional synthase provided further persuasive evidence of this association. These results argue that there is an important host-parasite relationship between chlamydial genital strains and the human host that determines organotropism of infection and the pathophysiology of disease. We speculate that this relationship involves the production of indole by components of the vaginal microbial flora, allowing chlamydiae to escape IFN-gamma-mediated eradication and thus establish persistent infection.
Caldwell
Harlan D
HD
Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, Montana, USA.
Wood
Heidi
H
Crane
Debbie
D
Bailey
Robin
R
Jones
Robert B
RB
Mabey
David
D
Maclean
Ian
I
Mohammed
Zeena
Z
Peeling
Rosanna
R
Roshick
Christine
C
Schachter
Julius
J
Solomon
Anthony W
AW
Stamm
Walter E
WE
Suchland
Robert J
RJ
Taylor
Lacey
L
West
Sheila K
SK
Quinn
Tom C
TC
Belland
Robert J
RJ
McClarty
Grant
G
D000942:Antigens, Bacterial / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001483:Base Sequence; D015153:Blotting, Western; D002454:Cell Differentiation; D002692:Chlamydia trachomatis / Q000201:enzymology* / Q000235:genetics; D005123:Eye / Q000382:microbiology*; D005260:Female; D005836:Genitalia, Female / Q000382:microbiology*; D006367:HeLa Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007371:Interferon-gamma / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013045:Species Specificity; D014367:Tryptophan Synthase / Q000235:genetics*
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D007211:Indoles; D008565:Membrane Proteins; D007371:Interferon-gamma; D014367:Tryptophan Synthase