Plasmid-Encoded Pgp3 Is a Major Virulence Factor for Chlamydia muridarum To Induce Hydrosalpinx in Mice

Abstract

dHydrosalpinx induction in mice by Chlamydia muridarum infection, a model that has been used to study C. trachomatis pathogenesis in women, is known to depend on the cryptic plasmid that encodes eight genes designated pgp1 to pgp8. To identify the plasmid-encoded pathogenic determinants, we evaluated C. muridarum transformants deficient in the plasmid-borne gene pgp3, -4, or -7 for induction of hydrosalpinx. C. muridarum transformants with an in-frame deletion of either pgp3 or -4 but not -7 failed to induce hydrosalpinx. The deletion mutant phenotype was reproduced by using transformants with premature termination codon insertions in the corresponding pgp genes (to minimize polar effects inherent in the deletion mutants). Pgp4 is known to regulate pgp3 expression, while lack of Pgp3 does not significantly affect Pgp4 function. Thus, we conclude that Pgp3 is an effector virulence factor and that lack of Pgp3 may be responsible for the attenuation in C. muridarum pathogenicity described above. This attenuated pathogenicity was further correlated with a rapid decrease in chlamydial survival in the lower genital tract and reduced ascension to the upper genital tract in mice infected with C. muridarum deficient in Pgp3 but not Pgp7. The Pgp3-deficient C. muridarum organisms were also less invasive when delivered directly to the oviduct on day 7 after inoculation. These observations demonstrate that plasmid-encoded Pgp3 is required for C. muridarum survival in the mouse genital tract and represents a major virulence factor in C. muridarum pathogenesis in mice.

The Chlamydia-Secreted Protease CPAF Promotes Chlamydial Survival in the Mouse Lower Genital Tract

“…Ramsey et al (6) also used the mouse model for defining the role of the plasmid-encoded Pgp3 in the survival of C. trachomatis in the mouse genital tract. This finding was validated in a C. muridarum infection mouse model in which a Pgp3-deficient C. muridarum strain was no longer able to induce hydrosalpinx (18). Pgp3 is an immunodominant antigen that is secreted into the cytosol of the infected cells (19)(20)(21).…”

In VivoandEx VivoImaging Reveals a Long-Lasting Chlamydial Infection in the Mouse Gastrointestinal Tract following Genital Tract Inoculation

“…We then further compared the C. muridarum spreading to the GI tract following intravaginal versus intrabursal inoculations. We previously showed that after intrabursal inoculation, there was a delay in live organisms descending to the vagina and being excreted out of the mouse body (8,38). We expected a significant delay of the spreading of the intrabursally inoculated organisms to the GI tract if oral uptake or anorectal contact of the excreted live organisms was required for the chlamydial spreading.…”

“…The clone CMUT3G42.2.1 was previously used for transformation with a luciferase expression plasmid designated pGFP-luci-CM (33). For the current study, the CMUT3G5 clone was used for transformation with the same pGFP-luci-CM plasmid (33) as described previously (37,38). Thus, the luciferase-expressing C. muridarum clone used in the current study was designated Nigg3-CMUT3G5-pGFP-Luci or G5-pGFP-Luci for short.…”

Intravenous Inoculation with Chlamydia muridarum Leads to a Long-Lasting Infection Restricted to the Gastrointestinal Tract

“…CP009760.1) with that of the reference C. muridarum strain (40), we redesignated this strain Nigg3. To make the luciferase-expressing C. muridarum strain, a recombinant pGFP-luci-CM plasmid or the pGFP:CM plasmid alone (41) was transformed into a Nigg3-derived plasmid-free clone as described previously (13,42). Both the luciferase-expressing C. muridarum strain (designated CMUT3G5-pGFP-Luci [abbreviated CM-luci]) and the C. muridarum strain transformed with green fluorescent protein (GFP) plasmid alone (designated CMUT3G5-pGFP [abbreviated CM-GFP]) were used in the present study, and they were propagated and purified as elementary bodies (EBs) as mentioned above.…”

“…This is because a single inoculation of C. muridarum organisms in the mouse lower genital tract can cause hydrosalpinx and infertility (7)(8)(9), closely mimicking the tubal adhesion, hydrosalpinx, and infertility observed in women urogenitally infected with C. trachomatis (10)(11)(12). Although C. muridarum is not a natural sexually transmitted agent of mice, chlamydiologists have used this model not only to identify both chlamydial (13)(14)(15)(16)(17) and host (1,5,(18)(19)(20)(21)(22)(23)(24) pathogenic determinants but also to define the roles of ascending infection and tubal inflammation in chlamydial induction of hydrosalpinx (9,16,25,26). Nevertheless, questions such as how a self-limited infection with C. muridarum in the mouse genital tract can trigger tubal fibrosis or hydrosalpinx that lasts long after the tubal infection is resolved (9,25) remain unanswered.…”