A heat-labile protein of Chlamydia trachomatis binds to HeLa cells and inhibits the adherence of chlamydiae

Anti-inflammatory effects of silver-polyvinyl pyrrolidone (Ag-PVP) nanoparticles in mouse macrophages infected with live Chlamydia trachomatis

Chlamydia trachomatis is a very common sexually transmissible infection in both developing and developed countries. A hallmark of C. trachomatis infection is the induction of severe inflammatory responses which play critical roles in its pathogenesis. Antibiotics are the only treatment option currently available for controlling C. trachomatis infection; however, they are efficacious only when administered early after an infection. The objectives of this study are to explore alternative strategies in the control and regulation of inflammatory responses triggered by a C. trachomatis infection. We employed silver-polyvinyl pyrrolidone (Ag-PVP) nanoparticles, which have been shown to possess anti-inflammatory properties, as our target and the in vitro mouse J774 macrophage model of C. trachomatis infection. Our hypothesis is that small sizes of Ag-PVP nanoparticles will control inflammatory mediators triggered by a C. trachomatis infection. Cytotoxicity studies using Ag-PVP nanoparticles of 10, 20, and 80 nm sizes revealed >80% macrophage viability up to a concentration of 6.25 μg/mL, with the 10 nm size being the least toxic. All sizes of Ag-PVP nanoparticles, especially the 10 nm size, reduced the levels of the prototypic cytokines, tumor necrosis factor (TNF) and interleukin (IL)-6, as elicited from C. trachomatis infected macrophages. Additionally, Ag-PVP nanoparticles (10 nm) selectively inhibited a broad spectrum of other cytokines and chemokines produced by infected macrophages. Of significance, Ag-PVP nanoparticles (10 nm) caused perturbations in a variety of upstream (toll like receptor 2 [TLR2], nucleotide-binding oligomerization-protein 2 [NOD2], cluster of differentiation [CD]40, CD80, and CD86) and downstream (IL-1 receptor-associated kinase 3 [IRAK3] and matrix metallopeptidase 9 [MMP9]) inflammatory signaling pathways by downregulating their messenger ribonucleic acid (mRNA) gene transcript expressions as induced by C. trachomatis in macrophages. Collectively, our data provides further evidence for the anti-inflammatory properties of Ag-PVP nanoparticles, and opens new possibilities for smaller sizes of Ag-PVP nanoparticles to be employed as regulators of inflammatory responses induced by C. trachomatis.

Radiofrequency ablation versus surgical resection for small hepatocellular carcinoma: a meta-analysis

AIM: To compare the therapeutic effects of radiofrequency ablation (RFA) and surgical hepatic resection (HR) in the treatment of small hepatocellular carcinoma (HCC).

METHODS: Literature about the controlled trials evaluating the efficacy between RFA and HR for the treatment of small HCC published between 1991 and 2011 were searched electronically. The criteria recommended by the Cochrane Handbook 4.2.2 for Systematic Reviews of Interventions were used for choosing the trails and assessing the quality of included studies. RevMan5.0.25 software was used for systematic review and meta-analysis.

RESULTS: Two randomized controlled trials and nine non-randomized controlled trials were included. A total of 2 965 patients were involved: 1 459 patients were treated with radiofrequency ablation as the initial treatment and 1 506 patients with surgical resection. Compared to the RFA group, the 3, 5-year survival rates and 1, 3, 5-year recurrence-free survival rates in the HR group was significantly higher (all P < 0.05). There were no significant difference in the 1-year survival rate between the RFA group and HR group (P > 0.05). Complications were significantly fewer in the RFA group than in the HR group (P < 0.05).

CONCLUSION: Surgical resection has more major complications than radiofrequency ablation, but the overall efficacy of surgical resection is better than radiofrequency ablation in the management of small HCC.

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.

Surface accessibility of the 70-kilodalton Chlamydia trachomatis heat shock protein following reduction of outer membrane protein disulfide bonds

Numerous investigations have shown that 70-kDa heat shock protein (Hsp70) homologs interact tightly with hydrophobic proteins and functionally assist proteins in membranous organelles and environments. One such protein is the Chlamydia trachomatis Hsp70 that is associated with isolated outer membrane complexes of infectious elementary bodies (EB). Previous observations have indicated that chlamydial Hsp70 plays a role in EB attachment to, or entry into, endometrial epithelial cells. In this study, immunofluorescence microscopy and transmission electron microscopy observations showed that chlamydial Hsp70 is not a surface-displayed ligand on purified EB. However, brief exposure of EB to the thiol reducing agent dithiothreitol (DTT) led to surface accessibility of the Hsp70 substrate-binding domain. Reduction of the highly disulfide-cross-linked EB outer membrane proteins with DTT resulted in a decrease in EB attachment and infectivity. Interestingly, exposure of EB to the membrane-impermeable thiol-alkylating reagent 5,5'-dithiobis(2-nitrobenzoic acid) enhanced attachment but compromised infectivity, suggesting that EB outer membrane proteins must be reduced for entry and productive infection. Together, our data suggest that (i) the structural integrity of the EB outer membrane, maintained by protein disulfide bonds, is important during the initial stages of attachment; (ii) reduction occurs within the localized microenvironment of host cell surfaces once intimate contact is established between EB and host cells; and (iii) subsequent conformational changes in EB ultrastructure allow productive infection in host cells. The accessibility of the Hsp70 substrate-binding domain may support the hypothesis that this protein plays a role in events following the initial stage of attachment instead of serving as a primary, surface-displayed adhesin.

Chlamydia infection of epithelial cells expressing dynamin and Eps15 mutants: clathrin-independent entry into cells and dynamin-dependent productive growth

Chlamydiae enter epithelial cells via a mechanism that still remains to be fully elucidated. In this study we investigated the pathway of entry of C. psittaci GPIC and C. trachomatis LGV/L2 into HeLa cells and demonstrated that it does not depend on clathrin coated vesicle formation. We used mutant cell lines defective in clathrin-mediated endocytosis due to overexpression of dominant negative mutants of either dynamin I or Eps15 proteins. When clathrin-dependent endocytosis was inhibited by overexpression of the dynK44A mutant of dynamin I (defective in GTPase activity), Chlamydia entry was not affected. However, in these cells there was a dramatic inhibition in the proliferation of Chlamydia and the growth of the chlamydia vacuole (inclusion). When clathrin-dependent endocytosis was inhibited by overexpression of an Eps15 dominant negative mutant, the entry and growth of Chlamydia was unaltered. These results indicate that the effect on the growth of Chlamydia in the dynK44A cells was not simply due to a deprivation of nutrients taken up by endocytosis. Instead, the dominant-negative mutant of dynamin most likely affects the vesicular traffic between the Chlamydia inclusion and intracellular membrane compartments. In addition, cytochalasin D inhibited Chlamydia entry by more than 90%, indicating that chlamydiae enter epithelial cells by an actin-dependent mechanism resembling phagocytosis. Finally, dynamin is apparently not involved in the formation of phagocytic vesicles containing Chlamydia.

Localization of intracellular Ca2+ stores in HeLa cells during infection with Chlamydia trachomatis

Chlamydia trachomatis elementary bodies (EBs) enter epithelial cells within membrane-bound endosomes that aggregate with each other in a calcium-regulated process, but avoid fusion with lysosomes. Annexin III but not I translocates to chlamydial aggregates and inclusions. In this study, we localize the intracellular Ca2+ stores during the course of infection by analyzing the distribution of three intracellular Ca2+ store proteins: calreticulin, type-1 inositol-1,4, 5-trisphosphate receptor (IP3-R), and Sarcoplasmic/Endoplasmic Reticulum Ca2+ ATPase type 2 (SERCA2) in HeLa cells infected with C. trachomatis serovar L2. In uninfected cells, immunofluorescence staining of the proteins showed a fine granular distributed pattern for all three proteins. After infection with C. trachomatis, calreticulin was found at the periphery of chlamydial aggregates and inclusions from 3 to 48 hours post-infection. In infected cells, SERCA2 was intimately associated with chlamydial inclusions after 3 and 24 hours, but not after 48 hours. Moreover, IP3-R was translocated to and colocalized with EB aggregates and chlamydial inclusions and had a distribution very similar to that of SERCA 2. After 24 hours incubation with chlamydiae, there was a local accumulation of [Ca2+]i (105+/-17 nM) in the proximity of chlamydial inclusions, compared to 50+/-13 nM in other parts of the cell cytoplasm. In the absence of extracellular Ca2+, this local accumulation of Ca2+ increased to 295+/-50 nM after adding 50 microM ATP, and to a similar extent after adding 100 nM thapsigargin (Tg). These data indicate that during infection of HeLa cells with chlamydiae, intracellular Ca2+ stores are redistributed, causing local accumulation of Ca2+ in the vicinity of chlamydial inclusions. These changes may trigger the association of certain proteins such as annexins with chlamydia-containing vesicles, and thereby regulation of membrane-membrane interaction during endosome aggregation and inclusion formation.

The intracellular life of Chlamydia psittaci: how do the bacteria interact with the host cell?

Throughout the life of any organism interactions with the surrounding environment are always taking place, a process that leads to evolution. Chlamydia psittaci is an obligate intracellular parasite, but it must also be capable of extracellular survival in order to search for new host cells. Therefore, these peculiar prokaryotes have evolved two different particles and a unique developmental cycle that, together with a series of not yet fully understood interactions with their host cells, allow them to fulfil the requirements for their permanence in nature. These interactions are the subject of this paper. Particular attention is paid to the attachment and internalization of the bacteria, the chlamydial vacuole, and the avoidance of lysosomal degradation.

Haemophilus ducreyi infection causes basal keratinocyte cytotoxicity and elicits a unique cytokine induction pattern in an In vitro human skin model

Haemophilus ducreyi is the etiologic agent of the sexually transmitted genital ulcer disease chancroid. Predominantly a cutaneous pathogen, H. ducreyi is present in chancroid ulcers that are characterized by extensive neutrophil accumulation in intraepidermal lesions accompanied by a mononuclear infiltrate in the dermis. We used an in vitro human skin model composed of foreskin fibroblasts and keratinocytes to examine host skin cell interactions with H. ducreyi 35000. Bacteria replicated and persisted in artificial skin for at least 14 days. We observed H. ducreyi inside suprabasal keratinocytes using transmission electron microscopy. Although no bacteria were seen in the basal keratinocyte region, these cells were disrupted in infected cocultures. H. ducreyi infection stimulated increased secretion of interleukin-6 (IL-6) and IL-8 by skin cells. Conversely, tumor necrosis factor alpha and IL-1alpha levels were not elevated. IL-8 produced in response to H. ducreyi infection may be involved in recruiting polymorphonuclear leukocytes and other inflammatory cells, thereby contributing to the tissue necrosis and ulcer formation characteristic of chancroid.

A recombinant Chlamydia trachomatis major outer membrane protein binds to heparan sulfate receptors on epithelial cells

Chlamydial attachment to columnar conjunctival or urogenital epithelial cells is an initial and critical step in the pathogenesis of chlamydial mucosal infections. The chlamydial major outer membrane protein (MOMP) has been implicated as a putative chlamydial cytoadhesin; however, direct evidence supporting this hypothesis has not been reported. The function of MOMP as a cytoadhesin was directly investigated by expressing the protein as a fusion with the Escherichia coli maltose binding protein (MBP-MOMP) and studying its interaction with human epithelial cells. The recombinant MBP-MOMP bound specifically to HeLa cells at 4 degrees C but was not internalized after shifting the temperature to 37 degrees C. The MBP-MOMP competitively inhibited the infectivity of viable chlamydiae for epithelial cells, indicating that the MOMP and intact chlamydiae bind the same host receptor. Heparan sulfate markedly reduced binding of the MBP-MOMP to cells, whereas chondroitin sulfate had no effect on binding. Enzymatic treatment of cells with heparitinase but not chondroitinase inhibited the binding of MBP-MOMP. These same treatments were also shown to reduce the infectivity of chlamydiae for epithelial cells. Mutant cell lines defective in heparan sulfate synthesis but not chondroitin sulfate synthesis showed a marked reduction in the binding of MBP-MOMP and were also less susceptible to infection by chlamydiae. Collectively, these findings provide strong evidence that the MOMP functions as a chlamydial cytoadhesin and that heparan sulfate proteoglycans are the host-cell receptors to which the MOMP binds.

Interaction of outer envelope proteins of Chlamydia psittaci GPIC with the HeLa cell surface

The chlamydial life cycle involves the intimate interaction of components of the infectious elementary body (EB) surface with receptors on the susceptible eukaryotic cell plasma membrane. We have developed an in vitro ligand binding assay system for the identification and characterization of detergent-extracted EB envelope proteins capable of binding to glutaraldehyde-fixed HeLa cell surfaces. With this assay, the developmentally regulated cysteine-rich envelope protein Omp2 of Chlamydia psittaci strain guinea pig inclusion conjunctivitis was shown to bind specifically to HeLa cells. HeLa cells bound Omp2 selectively over other cell wall-associated proteins, including the major outer membrane protein, and the binding of Omp2 was abolished under conditions which alter its conformation. Furthermore, trypsin treatment, which reduces EB adherence, resulted in the proteolytic removal of a small terminal peptide of Omp2 at the EB surface and inactivated Omp2 in the ligand binding assay, while having a negligible effect on the major outer membrane protein. Collectively, our results suggest that Omp2 possesses the capacity to engage in a specific interaction with the host eukaryotic cell. We speculate that, since Omp2 is present only in the infectious EB form, the observed in vitro interaction may be representative of a determining step of the chlamydial pathogenic process.

Binding of Chlamydia trachomatis serovar L2 to collagen types I and IV, fibronectin, heparan sulphate, laminin and vitronectin

Chlamydia trachomatis serovar L2 elementary bodies were tested for binding to 125I-labelled components of the extracellular matrix. C. trachomatis bound high levels of collagen type I and heparan sulphate, whereas the binding to collagen type IV, fibronectin, laminin and vitronectin was substantially less. Preliminary characterization showed that chlamydial surface proteins are essential for binding to occur. Our results suggest that a selective affinity for C. trachomatis to a limited number of components of the extracellular matrix may have important implications mediating attachment to host cell surfaces and localization of chlamydiae in other tissues, such as joints.

Chlamydia trachomatis Mip-like protein

A 27 kDa Chlamydia trachomatis Mip-like protein with homology of a 175-amino-acid C-terminal fragment to the surface-exposed Legionella pneumophila mip-gene product has previously been described. In this paper the entire chlamydia Mip-like sequence of C. trachomatis serovar L2 (lymphogranuloma venereum (LGV) biovar) is presented. The sequence shows high similarity to the legionella Mip protein and its C-terminal region, like that of the legionella Mip, has high amino acid similarity to eukaryotic and prokaryotic FK506-binding proteins. The chlamydial mip-like gene was detected by polymerase chain reaction (PCR) in other C. trachomatis serovars and by sequencing of the mip-like genes of serovars B and E (trachoma biovar) was shown to be highly conserved within the two major biovars of C. trachomatis. Monoclonal and polyclonal antibodies raised against the recombinant Mip-like protein failed to demonstrate surface-exposed epitopes on infectious elementary bodies or reproductive reticulate body forms either by immunofluorescence or immuno-gold electron microscopy. However, a complement-dependent inhibition of up to 91% of infectivity for cell cultures was observed with antibodies to the N-terminal fragment of the Mip-like protein suggesting that antibody-accessible epitopes are present on infectious EBs.

Recombinant Escherichia coli clones expressing Chlamydia trachomatis gene products attach to human endometrial epithelial cells

To identify Chlamydia trachomatis genes involved in attachment to host cells, a chlamydial genomic library was screened on the basis of binding characteristics by two methods. In the whole-cell screen, individual recombinant Escherichia coli clones were assayed for adherence to eukaryotic cells. In the membrane-binding screen, each recombinant colony of E. coli was treated with CHCl3 and assayed for binding to purified, 3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propanesulfonate (CHAPS)-solubilized, 35S-labeled eukaryotic membrane material. Initial screening with McCoy cells was refined by using HEC-1B cells, a human endometrial epithelial cell line, which discriminate among recombinants adhering to McCoy cells. Some recombinants demonstrate significantly greater adherence to HEC-1B cells than to McCoy cells and appear, by transmission electron microscopy, to associate with electron-dense areas of the epithelial cell plasma membrane, resembling coated pits. Recombinants positive by one or both screening methods were examined by Southern and Western (immunoblot) analyses, which revealed the presence of chlamydial sequences inserted in the plasmids and the expression of novel 18-, 28-, and approximately 82 kDa, and perhaps of 18 Maxicell analysis of selected recombinants confirmed that the proteins of 28 and approximately 82 kDa, and perhaps of 18 kDa, are plasmid encoded. Antiserum generated against the recombinant approximately 82-kDa protein reacted in Western analysis with a similar-sized protein from C. trachomatis serovar E elementary bodies (EB) and reticulate bodies, serovar L2 EB, and C. psittaci EB. E. coli JM109(pPBW58) contains a 6.7-kb plasmid insert which encodes proteins of all three sizes. Under a number of different conditions in the whole-cell attachment assay--i.e., at 4 degrees C, in Ca(2+)- and Mg(2+)-free medium, in the presence of trypsin or dextran sulfate, and with rabbit aortic endothelial cells--the binding specificity of JM109(pPBW58) parallels that of C. trachomatis EB. Finally, the adherence phenotype of E. coli JM109(pPBW58) correlates directly with the presence of the recombinant plasmid; the phenotype is lost concurrently with loss of the recombinant plasmid, and the into E. coli JM109. The role of the 18-, 28-, and approximately 82-kDa proteins in mediating attachment, whether they act in concert as a complex or individually, has yet to be determined.