Cytoskeletal requirements in Chlamydia trachomatis infection of host cells.

Infection of genital epithelial cells by the closely related sexually transmitted pathogens Chlamydia trachomatis serovars E and L2 results in different clinical disease manifestations. Following entry into target host cells, individual vesicles containing chlamydiae fuse with one another to form one large inclusion. At the cellular level, the only obvious difference between these serovars is the time until inclusion maturation, which is 48 h for the invasive serovar L2 and 72 h for serovar E. To begin to define the intracellular events of these pathogens, the effect of cytoskeletal disruption on early endosome fusion and inclusion development in epithelial (HEC-1B) and fibroblast (McCoy) cells was analyzed by fluorescence microscopy. Disruption of microfilaments with cytochalasin D markedly reduced serovar E, but not serovar L2, infection of both cell lines. Conversely, microfilament as well as microtubule disruption, with colchicine or nocodazole, had no effect on serovar E inclusion development but resulted in the formation of multiple serovar L2 inclusions per cell during early and mid-development. Later in serovar L2 inclusion development (> 36 h postinfection), vesicles containing chlamydiae fused to form one large inclusion in the absence of an intact cytoskeleton. These results imply that (i) C. trachomatis serovar E may utilize a different pathway for uptake and development from serovar L2; (ii) these differences are consistent in both epithelial cells and fibroblasts; and (iii) the cytoskeleton plays a unique role in the infection of host cells by these two genital pathogens.     

Reactivation of Chlamydia trachomatis lung infection in mice by cortisone.

To study the latency, chronicity, and recurrent nature of chlamydial infection, we attempted to reactivate Chlamydia trachomatis lung infection in mice by immunosuppressive therapy with cortisone. Mice were treated with subcutaneous injections of cortisone acetate (125 mg/kg) every other day, starting on day 14 after intranasal inoculation of C. trachomatis serotype B (TW-5). C. trachomatis was recovered from the lungs beginning day 6 after the start of cortisone treatment until the end of the observation period on day 12 of treatment. Overall, the reactivation was successful in 8 of 55 mice treated with cortisone, in contrast to 0 of 41 inoculated, untreated mice (P = 0.009) and 0 of 35 uninoculated, treated mice. Cortisone treatment affected the ability of peritoneal exudate cells to respond to migratory inhibition after exposure to purified whole organisms of C. trachomatis serotype B (TW-5) but had little effect on serum antibody titers, indicating a possible role for cellular immunity in resistance against C. trachomatis infection in the lung.     

Impact of host genetics on susceptibility to human Chlamydia trachomatis disease

Evidence that host genetic factors play a major role in susceptibility or resistance to many infectious diseases is increasing, due to major advances in genetic epidemiological methodology. Recent human genome mapping information and the identification of a large number of candidate genes provide the tools for such studies. The information obtained is important for understanding the pathogenesis of disease and for the design of preventive and therapeutic strategies. In the study of Chlamydia trachomatis disease pathogenesis, much research focuses on how bacterial factors modulate the immune response and thus contribute to the disease process. It is likely, however, that host factors also play a role, and therefore susceptibility to disease is the result of an environmental effect set against a background of genetic factors. This review outlines the evidence for the contribution of host genetic factors to susceptibility to C. trachomatis disease in humans.     

Effect of methylamine and monodansylcadaverine on the susceptibility of McCoy cells to Chlamydia trachomatis infection

We used inhibitors of receptor-mediated endocytosis to study the mechanisms of infectivity, especially the uptake mechanism, of Chlamydia trachomatis for cultured cells. The effect of methylamine and monodansylcadaverine on the different stages of the chlamydial growth cycle in McCoy cells was examined. There was a dose-related decrease in the number of chlamydial inclusions in the presence of these agents. Monodansylcadaverine also decreased the chlamydia-dependent uptake of radioactive amino acids. The agents did not affect the attachment of chlamydiae to the cells, but they increased the protease-removable fraction of cell-bound chlamydiae. The amines reduced the number of inclusions when added at different times during the first 24 h of infection. However, this effect was influenced by host cell density, so that the effect of the amines at the early infectious phase was nullified in confluent monolayers, whereas, during later phases, the effect was comparatively independent of host cell density. This indicates that the amines have different modes of action at different infectious stages. The effect of the amines was reversible, and they had no effect on the infectivity of pretreated chlamydial elementary bodies. These experiments suggest that methylamine and monodansylcadaverine inhibit both the internalization of chlamydiae into McCoy cells and their intracellular development. These results are consistent with the hypothesis that chlamydiae utilize a constitutive cellular process, such as receptor-mediated endocytosis, to enter cells.     

Difference in susceptibility to gram-negative urinary tract infection between C3H/HeJ and C3H/HeN mice

The difference in susceptibility to urinary tract infection between C3H/HeJ and C3H/HeN mice was tested for with gram-negative strains differing in lipopolysaccharide composition. Recently, impaired clearance of Escherichia coli from the kidney of C3H/HeJ compared to C3H/HeN mice was shown to be correlated with the LPS low responsiveness. In this study, a difference in clearance from the kidneys of C3H/HeJ and C3H/HeN mice was found only with lipopolysaccharide-containing bacteria. Gram-positive bacteria, e.g., Staphylococcus saprophyticus and Streptococcus agalactiae, were recovered in essentially equal numbers from the kidneys of mice of both strains. In contrast, of the lipopolysaccharide-containing strains used, all persisted in higher numbers in the kidneys of C3H/HeJ mice than in the kidneys of C3H/HeN mice. Variations in the O side chain did not eliminate this difference. E. coli Hu734 O75+K5+ and the rfb- mutant O75-K5+ remained in similar numbers in C3H/HeJ mice, although O75-K5+ was eliminated more rapidly in C3H/HeN mice. The core structure did not affect the differential persistence in the two mouse strains. The rfb mutants with R1-R4 cores were eliminated after 24 h from the C3H/HeN mice, but remained in significant numbers in the kidneys of C3H/HeJ mice. Even the Re mutant of Salmonella minnesota persisted in low numbers in C3H/HeJ mice. The relative bacterial recovery from either mouse strain was related to the overall virulence of the infecting bacterial strain, but the difference between C3H/HeJ and C3H/HeN mice was associated with responsiveness to parts of lipopolysaccharide common to the bacterial strains tested.     

炎症性细胞因子在沙眼衣原体肺感染中的表达及其与机体防御的关系

目的 探讨炎症性细胞因子TNF-a，IL-1β和IL-6在沙眼衣原体肺感染中的产生及与机体防御的关系。方法 用沙眼衣原体小鼠肺炎株(MoPn)通过鼻腔感染小鼠，用过氧化物酶连接的鼠抗衣原体脂多糖单抗染色HeLa229细胞检测衣原体在肺组织的生长；通过测定中性粒细胞髓过氧化物酶(MPO)检测中性粒细胞在小鼠肺组织中的聚集；用RT-PCR检测小鼠肺组织炎症性细胞因子mRNA表达。结果 MoPn感染后第2天，肺组织有衣原体生长，于感染后第7天达高峰，第21天清除感染的衣原体。感染后第3天，前炎症细胞因子TNF-α，IL-B和IL-6在小鼠肺组织中的表达明显增高，IL-1β mRNA表达于感染第7天后降低，而TNF-a和IL-6 mRNA的表达至感染后第14天仍维持较高水平。高水平的TNF-α，IL-lβ和IL-6表达出现于中性粒细胞浸润的高峰期。结论 衣原体肺感染诱导前炎症细胞因子TNF-α，IL-1β和IL-6的高表达，可能具有中性粒细胞趋化活性，并参与衣原体感染的免疫防御。     

Genetic analysis of susceptibility to Chlamydia trachomatis in mouse

Chlamydia trachomatis is a bacterial pathogen that is a major cause of blindness and infertility in diverse populations across the world. In an effort to model genetic complexities that are observed in human populations and to identify novel genes involved in susceptibility to C. trachomatis, we have adapted a murine model of systemic infection for use in genetic analysis. In this model, chlamydial colonization and replication is measured in the spleens of mice shortly after intravenous delivery of C. trachomatis L2. Here, we show that C57BL/6J and C3H/HeJ inbred mice are differentially susceptible to this systemic infection. Additionally, fibroblasts cultured from C57BL/6J and C3H/HeJ embryos are differentially permissive for chlamydial replication. We have taken advantage of this natural variation to map quantitative trait loci on Chromosomes 2, 3, and 11 that segregate with the bacterial load in F2 cross progeny during the acute phase of C. trachomatis infection in vivo. To validate our mapping results, we also generated mice that are congenic for a portion of Chromosome 11 from the susceptible parent. This congenic interval confers increased susceptibility to C. trachomatis, both in vivo and in vitro, suggesting that our screen identified at least one gene that is involved in cellular resistance to C. trachomatis replication.     

High analytical sensitivity and low rates of inhibition may contribute to detection of Chlamydia trachomatis in significantly more women by the APTIMA Combo 2 assay

The clinical sensitivity of nucleic acid amplification tests may be determined by analytical sensitivity and inhibitors in patient samples. We established endpoints for detection of propagated Chlamydia trachomatis L2 434, diluted according to swab and urine protocols for APTIMA Combo 2 (AC2), ProbeTec ET (PT), and Amplicor (AMP) assays. AC2 was 1,000-fold more sensitive than PT and 10-fold more sensitive than AMP on mock swab specimens. For urine, AC2 analytical sensitivity was 100-fold greater than those of the other assays. Spiking an aliquot of each clinical-trial sample from 298 women demonstrated inhibition rates in first-void urine (FVU), cervical swabs (CS), and vaginal swabs (VS) of 12.1%, 12.8%, and 10.4% for AMP; 27.2%, 2%, and 2%, for PT; and 0.3%, 1.7%, and 1.3% for AC2. Inhibition of our C. trachomatis spike and the PT or AMP amplification controls from the manufacturers showed less than 50% correlation. Using an infected-patient reference standard (a specimen positive in at least two tests or a single test positive in two of three samples) in AC2, the VS identified 68/69 (98.6%) infected women compared to CS (89.9%) or FVU (81.2%). Significantly fewer women were identified by PT (65.2%, 63.8%, and 66.7%) or AMP (65.2%, 59.4%, and 56.5%) with the three specimens. By individual specimen type, AC2 confirmed virtually all PT- and AMP-positive specimens, but rates of AC2 confirmation by AMP or PT ranged from 62.9 to 80.3%. The AC2 test identified significantly more women infected with C. trachomatis (P = 0.001). Vaginal swabs appear to be the specimen of choice for screening.     

Effect of Chlamydia trachomatis infection on atherosclerosis in apolipoprotein E-deficient mice

We have previously demonstrated that Chlamydia pneumoniae accelerates plaque formation in apolipoprotein E-deficient (ApoE(-/-)) mice following intranasal inoculations. In this study, we evaluated the effect of respiratory tract infection with Chlamydia trachomatis on the progression of atherosclerosis in ApoE(-/-) mice. The study showed that in contrast to infection with Chlamydia pneumoniae, infection of the lung and aorta with C. trachomatis was mild and transient and did not significantly accelerate plaque development.     

Role of gamma-delta T cells in murine Chlamydia trachomatis infection.

The role of gamma-delta T cells in host resistance to Chlamydia trachomatis was characterized by using a murine model of pneumonia caused by the mouse pneumonitis agent (MoPn), murine C. trachomatis. At days 3 and 7 after infection, gamma-delta T-cell-deficient knockout mice had significantly higher levels of MoPn in the lungs than did immunologically intact controls. At day 20, paradoxically, gamma-delta T-cell-deficient mice were more resistant to MoPn than were controls. This increased resistance was not due to an increased production of toxic cytokines or interleukin-10 in controls on that day. Gamma-delta T cells play a role in protection early in MoPn infection, but they may be deleterious later in infection, as has been observed in models of salmonella and trypanosome infection.     

The importance of interferon-gamma in an early infection of Chlamydia psittaci in mice.

Athymic mice (nu/nu) and their hairy littermates (nu/+) were infected experimentally with Chlamydia psittaci and the role of endogenous interferon-gamma (IFN-gamma) on the resolution of the infection was studied. The pathological changes produced in the spleen, liver and lung were exacerbated by administration of a monoclonal antibody (mAb) to IFN-gamma and an increased number of viable chlamydiae were recovered from the tissues of both nu/+ and nu/nu mice treated in this way.     

Effect of cortisol on the growth of Chlamydia trachomatis in McCoy cells.

The number of intracytoplasmic inclusions of Chlamydia trachomatis produced in McCoy cell monolayer cultures infected with a constant inoculum of a recently isolated genital strain was compared in cultures of untreated replicating cells and in monolayers which had been incubated in the presence of cortisol at initial extracellular concentrations between 0.0001 and 100 microgram/ml. The effect of adding cortisol was dependent on its concentration, on the time of addition to the tissue culture medium, and on the initial number of McCoy cells seeded to form the monolayer. When a concentration of 1.0 microgram/ml was added at the time of infection with C. trachomatis, the number of inclusions detectable after a further 48 h of incubation was increased by 1.84-fold over those detected in untreated cells. The mean size of inclusions and the ease of their recognition in McCoy cell cultures was also increased by this procedure.     

Dissociation of innate susceptibility to Salmonella infection and endotoxin responsiveness in C3HeB/FeJ mice and other strains in the C3H lineage.

Studies of various mouse strains in the C3H lineage have shown that there is no correlation between innate susceptibility to Salmonella infection and sensitivity to the toxic or mitogenic effects of lipopolysaccharide (LPS). C3H/HeNCrlBR mice were Salmonella resistant, but sensitive to the toxic and mitogenic effects of LPS, whereas C3HeB/FeJ mice were Salmonella susceptible as the C3H/HeJ mice, yet were mitogenically responsive to LPS and sensitive to its lethal effects. Furthermore, other mouse strains (C3H/HeTex and C3H/HeDub) displayed intermediate susceptibility to Salmonella infection and were responders to the mitogenic and toxic effects of LPS. These results are interpreted to mean that endotoxemia cannot be a major factor in the pathogenesis of Salmonella infection and provide evidence for the involvement of multiple factors in the control of innate resistance to Salmonella infection in mice of the C3H lineage.     

Prevalence of Chlamydia trachomatis lung infection in patients with acquired immune deficiency syndrome.

Brush biopsies and lung lavages were obtained from 263 individuals with acquired immune deficiency syndrome who collectively had 658 hospitalizations for pneumonia. Chlamydia trachomatis was isolated during three (0.5%) of the episodes, indicating that it was not an important respiratory tract pathogen in this population.     

Effects of estradiol and progesterone on susceptibility and early immune responses to Chlamydia trachomatis infection in the female reproductive tract

We have used a previously described rodent model to examine the influence of hormonal environment on susceptibility and immune responses to genital Chlamydia infection. Ovariectomized rats were administered estradiol, progesterone, or a combination of both, infected with Chlamydia trachomatis via the intrauterine route, and sacrificed 5 days later. Histopathological examination showed severe inflammation in the uteri and vaginae of progesterone-treated animals, whereas animals receiving estradiol or a combination of both hormones showed no inflammation. Large numbers of chlamydiae were found in vaginal secretions of progesterone-treated and combination-treated animals, while estradiol-treated animals had none. Tissue localization showed that numerous chlamydial inclusions were present in the uterine epithelium of the progesterone group and the cervicovaginal epithelium of the combination group. Examination of the acute immune responses of the infected animals showed that maximum activation was present in the draining lymph node cells from the progesterone-treated group, and these cells were producing large amounts of interleukin-10 and gamma interferon compared to other hormone-treated groups. In contrast, spleen cell proliferation was suppressed in progesterone-treated animals compared to other hormone-treated groups. We conclude that progesterone increases and estradiol decreases susceptibility to intrauterine chlamydial infection in this rat model. Our data demonstrate that hormone environment, at the time of infection, has a profound effect on the outcome of microbial infection in the female reproductive tract.     

Humoral immune response to plasmid protein pgp3 in patients with Chlamydia trachomatis infection.

We identified, by two-dimensional electrophoretic analysis and microsequencing, a protein of Chlamydia trachomatis elementary bodies which corresponds to the polypeptide (pgp3) encoded by open reading frame 3 (ORF3). Amino acid analysis showed that the first residue (Gly) found in the native protein is the one encoded by the second ORF3 codon, implying a typical bacterial removal of the first Met residue. Relatively large amounts of recombinant pgp3 (r-pgp3) in a stable, water-soluble form were obtained by overexpressing ORF3 in Escherichia coli and purifying the product from periplasmic extracts under nondenaturing conditions. These r-pgp3 preparations allowed specific detection of anti-pgp3 antibodies by enzyme-linked immunosorbent assay. Analysis of a group of 170 sera from healthy blood donors and from patients who were seropositive or -negative for C. trachomatis and Chlamydia pneumoniae showed that an immune response to pgp3 occurs in the majority (ca. 81%) of patients with sexually transmitted diseases who are seropositive for C. trachomatis and generally correlates with the response to cell surface antigens. No reaction between r-pgp3 and C. pneumoniae-positive sera was detected.     

Ligase chain reaction to detect Chlamydia trachomatis infection of the cervix.

We performed a multicenter evaluation of ligase chain reaction (LCR) in the diagnosis of Chlamydia trachomatis infection of the cervix. This LCR provides an amplification of target sequences within the chlamydial cryptic plasmid. The LCR results were compared with those of isolation in cell culture. Discrepant (tissue culture-negative and LCR-positive) test results were resolved by the application of a direct immunofluorescent-antibody test to detect chlamydial elementary bodies and by the use of alternate DNA primers that targeted the chlamydial major outer membrane protein gene. A total of 234 of 2,132 specimens (10.9%) could be confirmed as containing C. trachomatis. Of these, 152 were detected by isolation in cell culture and 221 were detected by LCR. The corresponding sensitivities were 94% for LCR and 65% for cell culture. There was greater variability among study site results for cell culture sensitivity (52 to 92%) than for LCR sensitivity (87 to 98%). The specificity of each test was greater than 99.9%. Thus, LCR offers a highly sensitive nonculture method for detecting chlamydial infection of the cervix.     

Entry of the lymphogranuloma venereum strain of Chlamydia trachomatis into host cells involves cholesterol-rich membrane domains

Chlamydiae are bacterial pathogens which develop strictly inside the epithelial cells of their hosts. The mechanism used by chlamydiae to enter cells is not well characterized; however, it is thought to consist of a receptor-mediated process. In addition, the formation of clathrin-coated pits appears to be dispensable for chlamydiae to be internalized by host cells. Clathrin-independent endocytosis has recently been shown to occur through cholesterol-rich lipid microdomains, which are characterized by detergent insolubility. In the present study, we investigated whether these lipid domains play a role in Chlamydia trachomatis serovar L2 internalization by host cells. Our results show that after binding to HeLa cells, chlamydiae are associated with detergent-resistant lipid microdomains (DRMs), which can be isolated by fractionation of infected HeLa cells and flotation on a sucrose gradient. After internalization by HeLa cells, chlamydiae were still found in DRMs. In addition, extraction of plasma membrane cholesterol inhibited infection of HeLa cells by C. trachomatis. Many of the proteins associated with DRMs are glycosylphosphatidylinositol (GPI)-anchored proteins; however, our results could not identify a role for GPI-anchored proteins in the entry process. The same results were obtained for Chlamydia psittaci strain GPIC. We propose that cholesterol-rich domains participate in the entry of chlamydiae into host cells. Chlamydia binding to cholesterol-rich domains may lead to coalescence of the bacterial cells, which could trigger internalization by host cells.     

MIP-1α和MCP-1在沙眼衣原体肺感染中的产生及与机体防御的关系

目的：探讨趋化性细胞因子巨噬细胞炎症蛋白-1(MIP-1α)和单核细胞趋化蛋白-1(MCP-1)在沙眼衣原体肺感染中的产生及与机体防御的关系。方法：用沙眼衣原体小鼠肺炎株(MoPn)通过鼻腔感染小鼠，酶消化法制备小鼠肺组织炎症细胞，Wright-Giemsa染色计数巨噬细胞占肺炎症细胞的百分率；用RT-PCR检测小鼠肺组织趋化性细胞因子及细胞因子mRNA表达；ELISA法检测肺组织匀浆中细胞因子分泌。结果：MoPn感染后7及14天，MIP-1α和MCP-1及其相应的受体CCR1、CCR2在小鼠肺组织中的表达明显增高。与之趋化作用有关的单核．巨噬细胞在肺组织中的浸润也随之增高；而且MoPn感染上调Th1细胞因子IFN-γ及IL-12的表达及分泌，未见Th2细胞因子IL-4在肺组织中的基因表达及分泌；但具有免疫抑制作用的Th2细胞因子IL-10在感染后7天明显表达。结论：衣原体呼吸道感染诱导CC趋化性细胞因子MIP-1α和MCP-1高表达，可能与单核细胞免疫防御及Th1／Th2免疫应答调节有关。     

Dissemination of Chlamydia trachomatis chronic genital tract infection in gamma interferon gene knockout mice.

Mice (C57BL/6), treated with progesterone and infected intravaginally with the mouse pneumonitis strain of Chlamydia trachomatis (MoPn), acquired genital tract disease that ascended from the endocervix to the uterine horns, oviducts, and ovaries in a temporal fashion before the occurrence of spontaneous microbiological resolution by about 28 days after infection. Surprisingly, dissemination of MoPn in small numbers to draining lymph nodes, the peritoneal cavity, spleen, liver, kidneys, and lungs occurred in normal mice during the early stages of disease (7 to 14 days) in a portion of infected animals but resolved from these tissues, by microbiological criteria, prior to resolution of genital tract involvement. In contrast, gamma interferon knockout (IFN-gamma KO) mice exhibited dissemination of infection to a greater extent and for longer periods in a variety of tissues, and a portion of infected IFN-gamma KO mice failed to microbiologically resolve their genital tract disease. By comparison, C57BL/6 SCID mice uniformly failed to resolve their genital tract disease and exhibited high levels of dissemination to all tissues tested for extended (50-day) periods of times. Interestingly, although IFN-gamma KO mice failed to completely clear organisms from their genital tracts, they exhibited an attenuated infection indistinguishable from that of heterozygous littermates when challenged 112 days after primary infection. These data support a role for IFN-gamma in containing dissemination of MoPn from the genital tract to extragenital sites and in the microbiological resolution of infection. Data also indicate that IFN-gamma is not required for modulating reinfections, which normally follow a shorter and less dramatic course.