Differences in the association of Chlamydia trachomatis serovar E and serovar L2 with epithelial cells in vitro may reflect biological differences in vivo.

Chlamydia trachomatis serovar E is one of the most common bacterial sexually transmitted pathogens. Since it is an obligate intracellular bacterium, efficient colonization of genital mucosal epithelial cells is crucial to the infectious process. Serovar E elementary bodies (EB) metabolically radiolabeled with 35S-Cys-Met and harvested from microcarrier bead cultures, which significantly improves the infectious EB-to-particle ratio, provided a more accurate picture of the parameters of attachment of EB to human endometrial epithelial cells (HEC-1B) than did less infectious 14C-EB harvested from flask cultures. Binding of serovar E EB was (i) equivalent at 35 and 4 degrees C, (ii) decreased by preexposure of EB to heat or the topical microbicide C31G, (iii) comparable among common eukaryotic cell lines (HeLa, McCoy), and (iv) significantly increased to the apical surfaces of polarized cells versus nonpolarized cells. In parallel experiments with C. trachomatis serovar L2, serovar E attachment was not affected by heparin or heparan sulfate whereas these glucosaminoglycans dramatically reduced serovar L2 attachment. These data were confirmed by competitive inhibition of serovar E binding and infectivity by excess unlabeled live and UV-inactivated serovar E EB but not by excess serovar L2 EB. The noninvasive serovar E strains in the lumen of the genital tract enter and exit the apical domains of target columnar epithelial cells to spread canalicularly in an ascending fashion from the lower to the upper genital tract. In contrast, the invasive serovar L2 strains are primarily submucosal pathogens and likely use the glucosaminoglycans concentrated in the extracellular matrix to colonize the basolateral domains of mucosal epithelia to perpetuate the infectious process.     

Superoxide dismutase and catalase activity in HeLa 229 cells infected with Chlamydia trachomatis

Cytosolic superoxide dismutase (SOD) activity was found to increase with time during HeLa cell culture, this increase being due exclusively to Mn-SOD. Infection of the cells by Chlamydia trachomatis resulted in a further enhancement of this Mn-SOD activity, whereas cytosolic catalase activity was decreased in these infected cells. Superoxide (O-2.) being able to induce Mn-SOD and to inhibit catalase, these data suggest that Chlamydia trachomatis infection could be responsible for an increase in O-2. production by the infected HeLa cells.     

Chlamydia trachomatis (L2 serovar) binds to distinct subpopulations of human peripheral blood leukocytes

We have previously shown that infants with pneumonitis caused by Chlamydia trachomatis, an obligate intracellular bacterium, possess increased percentages of B lymphocytes but not T lymphocytes in their peripheral blood. It was then demonstrated that chlamydiae induce proliferation in vitro of human peripheral blood B lymphocytes and, in the presence of T cells, differentiation of B cells to immunoglobulin-secreting cells. In this study, we show that C. trachomatis (L2 serovar) binds preferentially to 50% of human B lymphocytes from peripheral blood but only to a small percentage, if any, of T cells. Both monocytes and granulocytes bind and ingest chlamydiae. Despite chlamydial binding to B cells and ingestion by monocytes, no uptake by B cells and limited growth (fewer than 0.5% inclusion-containing cells) in monocytes occur. There is a dramatic decrease in the percentage of cells associated with the bacteria after culture. These results are the first demonstration of binding of C. trachomatis (L2 serovar) to lymphocytes and represent a direct step toward correlating physical interactions between bacteria and lymphocytes with specific immunostimulatory activities in vitro.     

Mucosal and peripheral immune responses to chlamydial heat shock proteins in women infected with Chlamydia trachomatis

Most of the studies on 60-kDa and 10-kDa chlamydial heat shock proteins (HSPs) to date have been carried out with blood lymphocytes or serum antibody responses, which do not provide a clear picture of the actual pathogenesis as they do not differentiate primary infection from recurrent infection. Thus, in the present study induction of the immune response was evaluated by studying lymphoproliferation of both cervical and peripheral lymphocytes to synthetic peptides of cHSP60, cHSP10 and major outer membrane protein (MOMP) antigen. In addition, cervical antibody prevalence to MOMP antigen, cHSP60 and cHSP10 and cytokine levels in cervical washes was also determined. Positive proliferative responses of cervical lymphocytes to cHSP10 peptide were significantly higher (P < 0.05) in women with recurrent infections and that to MOMP antigen were significantly higher in primary infection. On proliferation of PBMCs with the above antigens, no significant difference was observed between primary and recurrent infection. Prevalence of cervical IgG and IgA antibodies to Chlamydia trachomatis was significantly higher (P < 0.05) during primary infection than recurrent infections. In contrast, prevalence of IgG and IgA antibodies to cHSP10 and IgG antibodies to cHSP60 was higher during recurrent infections than primary infections. Interferon (IFN)-gamma levels were significantly higher in cervical washes of women with recurrent infection and correlated strongly with cHSP60 antibody titres. Our data thus suggest that mucosal responses are more appropriate in understanding the pathogenesis of chlamydial infection and IFN-gamma could be involved in the modulation of immune responses towards chlamydial infection directly, by causing acute inflammation, or indirectly through modulation of HSP expression.     

Interaction of Chlamydia trachomatis serovar L2 with the host autophagic pathway

Chlamydiae are obligate intracellular pathogens that replicate within a membrane-bound compartment (the inclusion) and are associated with important human diseases, such as trachoma, pneumonia, and atherosclerosis. We have examined the interaction of the host autophagic pathway with Chlamydia trachomatis serovar L2 by using the specific autophagosomal stain monodansylcadaverine, antibodies to autophagosome-associated markers, and traditionally used autophagic inhibitors, particularly 3-methyladenine and amino acids. Chlamydial inclusions did not sequester monodansylcadaverine, suggesting absence of fusion with autophagosomes. Interestingly, exposure of cultures infected for 19 h to 3-methyladenine or single amino acids until the end of infection (44 h) caused various degrees of abnormalities in the inclusion maturation and in the progeny infectivity. Incubation of host cells with chemicals throughout the entire period of infection modulated the growth of Chlamydia even more dramatically. Remarkably, autophagosomal markers MAP-LC3 and calreticulin were redistributed to the inclusion of Chlamydia, a process that appears to be sensitive to 3-methyladenine and some amino acids. The present data indicate the lack of autophagosomal fusion with the inclusion because it was devoid of monodansylcadaverine and no distinct rim of autophagosomal protein-specific staining around the inclusion could be observed. However, high sensitivity of Chlamydia to conditions that could inhibit host autophagic pathway and the close association of MAP-LC3 and calreticulin with the inclusion membrane still suggest a potential role of host autophagy in the pathogenesis of Chlamydia.     

Parasite-specified phagocytosis of Chlamydia psittaci and Chlamydia trachomatis by L and HeLa cells.

Phagocytosis of the 6BC strain of Chlamydia psittaci and the lymphogranuloma venereum 440L strain of Chlamydia trachomatis by L cells and HeLa 229 cells occurred at rates and to extents that were 10 to 100 times greater than those observed for the phagocytosis of Escherichia coli and polystyrene latex spheres. Both species of Chlamydia were efficiently taken up by host cells of a type they had not previously encountered. Phagocytosis of chlamydiae was brought about by the interaction of parasite surface ligands with elements of the host cell surface. The chlamydial ligands were readily denatured by heat, were masked by antibody, and were resistant to proteases and detergents. The host cell components were reversibly removed by proteases. Chlamydial phagocytosis was inhibited when host cells were incubated for many hours with cycloheximide. It was suggested that the presence on the chlamydial cell surface of ligands with high affinity for normal, ubiquitously occurring structures on the surface of host cells is an evolutionary adaptation to intracellular existence. The term parasite-specified phagocytosis was used to describe the efficient phagocytosis of chlamydiae by nonprofessional phagocytes and to distinguish it from the host-specified immunological and non-immunological phagocytosis carried out by professional phagocytes.     

Differences in innate immune responses correlate with differences in murine susceptibility to Chlamydia muridarum pulmonary infection

We investigated the phenotypic basis for genetically determined differences in susceptibility and resistance to Chlamydia muridarum pulmonary infection using BALB/c and C57BL/6 mice. Following C. muridarum intranasal inoculation, the intensity of infection was very different between BALB/c and C57BL/6 beginning as early as 3 days post‐infection. Intrapulmonary cytokine patterns also differed at early time‐points (days 2 and 4) between these two strains of mice. The early recruitment of neutrophils to lung tissue was greater in BALB/c than in C57BL/6 mice and correlated with a higher number of inclusion forming units (IFU) of C. muridarum. At day 12 post‐infection, BALB/c mice continued to demonstrate a greater burden of infection, significantly higher lung cytokine levels for tumour necrosis factor‐α and interleukin‐17 (IL‐17) and a significantly lower level for interferon‐γ than did C57BL/6 mice. In vitro, bone‐marrow‐derived dendritic cells (BMDCs) from BALB/c mice underwent less functional maturation in response to C. muridarum infection than did BMDCs from C57BL/6 mice. The BMDCs of BALB/c mice expressed lower levels of activation markers (CD80, CD86, CD40 and major histocompatibility complex class II) and secreted less IL‐12 and more IL‐23 than BMDCs from C57BL/6 mice. Overall, the data demonstrate that the differences exhibited by BALB/c and C57BL/6 mice following C. muridarum pulmonary infection are associated with differences in early innate cytokine and cellular responses that are correlated with late differences in T helper type 17 versus type 1 adaptive immune responses.     

Contrast of Glycogenesis and protein synthesis in monkey kidney cells and HeLa cells infected with Chlamydia trachomatis lymphogranuloma venereum

Glycogen metabolism of monkey kidney (LLC-MK-2) cells and HeLa 229 cells infected with a Chlamydia trachomatis lymphogranuloma venereum 440 L (LGV) was studied. The growth cycle of LGV in both host cells was similar; however, a greater number of infectious organism developed intracellularly and were released into the medium during LGV infection of HeLa 229 cells than MK-2 cells. A rapid infection accompanied by a high rate of glycogen synthesis and a short period of accumulation was found in GeLa 229 cells infected with LGV. LGV infected MK-2 cells started to accumulate glycogen about the same time as HeLa 229 cells; however, the rate of glycogen synthesis was lower and the period of accumulation was longer. The LGV agent grew in cycloheximide-treated cells in the absence of host cell protein synthesis. Protein synthesis associated with LGV throughout the developmental cycle was similar in both cell types and could be abolished by chloramphenicol. The continued synthesis of glycogen in the presence of cycloheximide suggested that the synthesis of glycogen was directed by the organism in both MK-2 cells and HeLa 229 cells.     

Response of Chlamydia trachomatis serovar E to iron restriction in vitro and evidence for iron-regulated chlamydial proteins.

Iron is a well-established mediator of virulence in several bacterial pathogens, yet little is known about the role of iron in infectious disease processes caused by obligate intracellular bacterial pathogens. In this study, the effect of iron limitation was examined for the sexually transmitted infectious agent Chlamydia trachomatis in an in vitro model of human genital infection using the intracellular iron-chelating reagent deferoxamine mesylate (Desferal). Iron restriction caused a significant reduction in infectivity of C. trachomatis elementary bodies (EB) harvested from Desferal-exposed polarized epithelial cells when compared to that of EB harvested from iron-sufficient control cell cultures. Replacement of the Desferal exposure medium with medium containing iron-saturated transferrin restored chlamydial infectivity, whereas replacement with growth medium alone had no effect. The following three prominent morphological features were observed by electron microscopic examination of chlamydia-infected cells exposed to Desferal: (i) inclusions containing chlamydiae greatly delayed in maturation, (ii) substantial blebbing within chlamydial inclusions, and (iii) electron-dense material surrounding inclusions. Protein analyses of highly purified EB by two-dimensional polyacrylamide gel electrophoresis revealed that there were at least 19 candidate iron-repressible proteins in C. trachomatis and at least one protein which was iron inducible. One putative iron-repressible protein was confirmed by Western blot (immunoblot) analysis to be the chlamydial heat shock protein 60 (hsp60). The enhanced production of this antigen by chlamydiae as a result of iron limitation is of particular importance since there is a well-documented association between chlamydial hsp60 and destructive immunopathological sequelae in infected patients.     

腺病毒介导MOMP基因转染对树突状细胞免疫功能的影响

目的 探讨腺病毒(Ad)介导E型沙眼衣原体(Ct)主要外膜蛋白(MOMP)基因转染对树突状细胞(DC)的表型及体内免疫功能的影响.方法 用小鼠重组粒细胞一巨噬细胞集落刺激因子(GM-CSF)及白细胞介素4(IL-4)从小鼠骨髓干细胞中诱导培养DC,并用大肠杆菌脂多糖(LPS)促进DC的成熟,流式细胞仪检测DC表型.用不同感染滴度(MOI)的含增强绿色荧光蛋白(EGFP)基因的重组Ad转染DC,荧光显微镜下观察EGFP的表达细胞百分率,选择最佳MOI;用最佳MOI的含MOMP基因的重组腺病毒(Ad-MOMP)转染DC,流式细胞术检测转染前后DC表型变化,并用活细胞计数试剂盒8(CCK-8)检测转染前后DC刺激同种淋巴细胞增殖的能力;ELISA检测转染前后DC分泌细胞因子及DC、T细胞共同培养上清中细胞因子的水平.Ad-MOMP转染DC经尾静脉免疫小鼠,ELISA检测其脾脏淋巴细胞分泌的细胞因子.结果 诱导的DC形态典型,表面高表达CD11c、MHCⅡ类分子,中度表达CD80分子.MOI=1000为重组Ad转染DC最佳滴度,此时90%以上的DC表达荧光,Ad-MOMP转染DC后能检测到MOMP的表达.Ad-MOMP转染对DC表面的特征性表型CD11c无影响,而CD80及MHCⅡ表达上调;转染后的DC分泌大量IL-12,具有较强的刺激同种异体淋巴细胞增殖的能力,并刺激T细胞分泌大量IFN-γ.Ad-MOMP转染DC后尾静脉免疫小鼠,其脾细胞产生高水平的IFN-γ.结论 Ad载体能介导外源MOMP基因在DC中的表达,Ad-MOMP转染DC后MOMP基因的表达能增强DC抗原提呈功能,促进DC活化,转染后的DC与T细胞共孵育能诱导T细胞向TH1细胞分化,体内实验表明Ad-MOMP转染DC能诱导衣原体特异性TH1反应.这为Ad-MOMP转染的DC疫苗用于免疫治疗提供了理论依据和技术基础.     

Binding, ingestion, and multiplication of Chlamydia trachomatis (L2 serovar) in human leukocyte cell lines.

We examined the ability of lymphoblastoid-myeloid cell lines to bind, ingest, and permit multiplication of Chlamydia trachomatis (L2 serovar). Four types of chlamydia-cell line interactions were observed: minimal bacterial binding; bacterial binding, followed by ingestion and high-level multiplication; bacterial binding, followed by ingestion but minimal multiplication; and bacterial binding, but minimal ingestion or replication. Our data demonstrate that at 37 degrees C in vitro the L2 serovar can both bind avidly to a cell without entering it and enter nonphagocytic cells but not grow.     

Sustained interleukin-6 and interleukin-8 expression following infection with Chlamydia trachomatis serovar L2 in a HeLa/THP-1 cell co-culture model

Chlamydia trachomatis, an intracellular obligate bacterium, remains responsible for a large spectrum of disorders that can progress to chronic diseases, resulting in severe sequelae, such as tubal infertility and blindness. These sequelae may be due to deleterious immune responses induced by repeated or persistent infections. By initiating and regulating inflammation as well as immune responses, pro-inflammatory cytokines secreted by local infected epithelial and immune cells, such as monocytes, may play an essential role in immunity and in the immunopathogenesis of chlamydial diseases. In this study, we mimicked the in vivo interaction between epithelial cells and monocytes by co-culturing epithelial-like HeLa cells with monocyte-like THP-1 cells. Pro-inflammatory cytokines [interleukin-beta (IL-1beta), IL-6, IL-8, IL-10, IL-12p70 and tumour necrosis factor-alpha (TNF-alpha)] were measured by multiplexed cytometric bead array assay over a period of 18 days. We observed that pro-inflammatory cytokine secretion was augmented after C. trachomatis infection in HeLa and THP-1 cells. However, this heightened secretion was subsequently reduced. When infected HeLa cells were co-cultured with THP-1 cells, IL-6 and IL-8 secretion was sustained, IL-1beta expression followed a bell-shaped curve and IL-10, IL-12p70 and TNF-alpha synthesis was down regulated. IL-6 and IL-8 may be involved in the immunopathogenesis of chronic chlamydial infections. We also observed that throughout C. trachomatis persistence induced by doxycycline (Dox) treatment, IL-1beta, IL-6, IL-8 and TNF-alpha expression was reduced, whereas the synthesis of IL-10 and IL-12p70 remained unchanged but not sustained. Thus, during chlamydial persistence infection evoked by treatment with Dox, none of the tested cytokines showed sustained expression.     

含E型沙眼衣原体MOMP基因的重组腺病毒和DNA疫苗联合免疫效果的研究

目的探讨E型沙眼衣原体（Ct）主要外膜蛋白（MOMP）DNA疫苗和重组腺病毒联合免疫小鼠诱导的免疫效应。方法构建、纯化重组腺病毒Ad-MOMP及重组真核表达质粒pVAX1-MOMP。设计4种免疫方案,分别为DNA免疫（ DNA组）、重组腺病毒免疫（ Ad组）、DNA初次免疫-重组腺病毒加强免疫（ DNA/Ad组）、重组腺病毒初次免疫-DNA加强免疫（ Ad/DNA组）。末次免疫后2周检测小鼠血清特异IgG、IgG1、IgG2a、IgA抗体,阴道分泌物SIgA抗体及脾淋巴细胞分泌IFN-γ、IL-10水平。结果DNA组诱导较弱免疫应答,未产生SIgA抗体及Th1反应。 Ad组诱导出Th1反应及SIgA抗体,且血清抗体显著高于DNA组。联合免疫均能诱导明显强于单独免疫的黏膜SIgA、血清抗体及Th1反应。 Ad/DNA组的Th1反应强于DNA/Ad组;而DNA/Ad组的血清抗体和黏膜抗体水平强于Ad/DNA组。结论Ad-MOMP能诱导黏膜免疫及Th1细胞免疫应答,DNA/Ad及Ad/DNA联合免疫产生的特异性免疫应答明显强于单独免疫。其中Ad/DNA的Th1反应优势更明显,DNA/Ad的血清抗体和黏膜抗体反应更强。接种顺序会影响联合免疫的强弱及类型,这为Ct疫苗的设计研究提供新的思路和实验依据。     

Co-incubation of human spermatozoa with Chlamydia trachomatis serovar E causes premature sperm death

The aim of this work was to investigate the effect of elementary bodies (EB) of Chlamydia trachomatis serovars E and LGV on sperm motility, viability and acrosomal status. Highly motile preparations of spermatozoa from normozoospermic patients were co-incubated for 6 h with 0.54x10(6) EB per ml. At 1, 3 and 6 h of incubation, sperm motility was determined by computer-assisted semen analysis (CASA) and the proportion of dead cells determined by the hypo-osmotic swelling (HOS) test. Acrosomal status was also examined using a standard monoclonal antibody assay. In the absence of EB, the percentage of motile spermatozoa remained >69% over the 6h incubation and the proportion of dead spermatozoa at <12%. However, during the incubation with EB of serovar E there was a significant decline in the percentage of motile spermatozoa (P < 0.05), and a corresponding increase in the proportion of dead spermatozoa (P < 0.05) at all time-points. However, following incubation with serovar LGV, only the percentage of dead spermatozoa after 6 h incubation was significantly different from the control (P < 0.05). The amount of acrosome-reacted spermatozoa remained unchanged (<16%) in all incubations at all time-points. Dose-response experiments indicated that increasing the concentration of EB to 2.5x10(6) per ml did not significantly alter the results. Furthermore, co-incubation of spermatozoa with dead EB (killed by heat treatment) abolished the chlamydia-mediated response, indicating that the effect is a result of the live organism and not soluble components or membrane elements. These data suggest that a detrimental effect on sperm function by some serovars may be an as yet unrecognized component of infertility problems.     

Vesicles containing Chlamydia trachomatis serovar L2 remain above pH 6 within HEC-1B cells.

Chlamydia trachomatis serovar L2 is an obligate intracellular bacterium which is internalized in target epithelial cells by endocytosis and resides within a membrane-bound vesicle. Over the next several hours following entry, individual serovar L2-containing vesicles fuse with one another to form a single membrane-bound vesicle (or inclusion) within which the microcolony develops. The experiments reported here directly examined the pH of vesicles containing chlamydiae. The pH was determined by measuring emission ratios of the fluorescent, pH-sensitive probe SNAFL (5-[and 6-]-carboxyseminaphthofluorescein-1, succinimidyl ester) conjugated to chlamydiae. The pH remained above 6.0 at 2, 4, and 12 h after infection, while the pH of vesicles contained heat-killed organisms fell 5.3. In the presence of amines, which raise the pH of acidic compartments, C. trachomatis inclusion formation was unaffected. Inactivation of Na+,K+ -ATPases, the ion pumps responsible for maintaining a pH above 6 within early endocytic vesicles, inhibited the growth of C. trachomatis within epithelial cells. Preventing vesicular acidification by inhibiting the vacuolar proton ATPase did not affect chlamydial growth. Thus, chlamydiae do not reside within highly acidic vesicles and avoid the pathway leading to lysosomes.     

Cell-mediated immune responses in owl monkeys (Aotus trivirgatus) with trachoma to soluble antigens of Chlamydia trachomatis.

The first temporal study of the cell-mediated immune responses (CMI) following ocular infections with Chlamydia trachomatis is presented. We examined the CMI of owl monkeys infected with trachoma to soluble antigens of C. trachomatis by leucocyte migration inhibition (LIF) and delayed hypersensitivity skin testing. Delayed hypersensitivity of a systemic nature developed after a local eye infection in owl monkeys; clearance of inclusions from conjunctival cells coincided with the onset of this response. The association of eye secretion and circulating antibodies with recovery from primary infection was not so striking. Both cellular and humoral immune responses persisted for at least 2 months, at which time all test animals were completely resistant to re-infection. The elicitation of cell-mediated immune reactions with solubilized chlamydial antigens may permit the isolation of specific antigens involved in the generation of protective immunity in the owl monkey model.     

Interaction of Chlamydia trachomatis organisms and HeLa 229 cells.

The infection of HeLa 229 cells in monolayer culture with trachoma (B/TW-5/OT) and lymphogranuloma venereum (LGV) (L2/434/Bu) organism was studied in terms of two parameters: radioactivity counts of cell-associated tritium labeled organisms at the initial stage of inoculation for measurement of attachment, and inclusion counts of infection cells after incubation for measurement of growth. Factors affecting attachment and inclusion formation and correlation of the two are presented. It was shown that attachment is an important initial step in infection by Chlamydia trachomatis. The rate of attachment was temperature dependent. The attachment of LGV organisms was affected more profoundly by temperature than was that of trachoma organisms. Attachment and inclusion formation of trachoma and LGV organisms were inhibited by heparin. Diethylaminoethyl-dextran was again shown to enhance attachment and inclusion formation of trachoma but not LGV organisms. NaF had no effect on attachment, but inhibited inclusion formation of both trachoma and LGV organisms. Both attachment and inclusion formation of trachoma organisms were strongly enhanced by centrifugation of the inoculum onto the cell monolayer. Although inclusion formation of trachoma organism was much greater in susceptible cells (HeLa 229) than relatively insusceptible cells (fetal tonsil), attachment was only slightly greater. The results based on the test of two cell lines suggested that attachment prpbably is not a critical factor in determing a cell line's susceptibility to infection with trachoma organisms.     

Characterization of a linear epitope on Chlamydia trachomatis serovar L2 DnaK-like protein.

A cytoplasmic 75-kDa immunogen from Chlamydia trachomatis serovar L2 has previously been characterized as being similar to the Escherichia coli heat shock protein DnaK. We have localized a linear epitope for one monoclonal antibody specific for C. trachomatis DnaK. By use of a recombinant DNA technique, the epitope was limited to 14 amino acids. With synthetic peptides, the epitope was further limited to eight amino acids. Six of these amino acids are conserved in bovine HSP70, which has a known three-dimensional structure. The amino acid sequence homologous to the epitope is located in a linear part of the HSP70 molecule known as connect II.