Polymorphism in the Yersinia LcrV Antigen Enables Immune Escape From the Protection Conferred by an LcrV-Secreting Lactococcus Lactis in a Pseudotuberculosis Mouse Model

Yersinioses caused by Yersinia pestis, Yersinia pseudotuberculosis, and Yersinia enterocolitica are significant concerns in human and veterinary health. The link between virulence and the potent LcrV antigen has prompted the latter's selection as a major component of anti-Yersinia vaccines. Here, we report that (i) the group of Yersinia species encompassing Y. pestis and Y. pseudotuberculosis produces at least five different clades of LcrV and (ii) vaccination of mice with an LcrV-secreting Lactococcus lactis only protected against Yersinia strains producing the same LcrV clade as that of used for vaccination. By vaccinating with engineered LcrVs and challenging mice with strains producing either type of LcrV or a LcrV mutated for regions of interest, we highlight key polymorphic residues responsible for the absence of cross-protection. Our results show that an anti-LcrV-based vaccine should contain multiple LcrV clades if protection against the widest possible array of Yersinia strains is sought.

Flagellin-Mediated Protection against Intestinal Yersinia pseudotuberculosis Infection Does Not Require Interleukin-22

Signaling through Toll-like receptors (TLRs), the main receptors in innate immunity, is essential for the defense of mucosal surfaces. It was previously shown that systemic TLR5 stimulation by bacterial flagellin induces an immediate, transient interleukin-22 (IL-22)-dependent antimicrobial response to bacterial or viral infections of the mucosa. This process was dependent on the activation of type 3 innate lymphoid cells (ILCs). The objective of the present study was to analyze the effects of flagellin treatment in a murine model of oral infection with Yersinia pseudotuberculosis (an invasive, Gram-negative, enteropathogenic bacterium that targets the small intestine). We found that systemic administration of flagellin significantly increased the survival rate after intestinal infection (but not systemic infection) by Y. pseudotuberculosis This protection was associated with a low bacterial count in the gut and the spleen. In contrast, no protection was afforded by administration of the TLR4 agonist lipopolysaccharide, suggesting the presence of a flagellin-specific effect. Lastly, we found that TLR5- and MyD88-mediated signaling was required for the protective effects of flagellin, whereas neither lymphoid cells nor IL-22 was involved.

Characterization of the protective immune response to Yersinia pseudotuberculosis infection in mice vaccinated with an LcrV-secreting strain of Lactococcus lactis

BACKGROUND

Pseudotuberculosis is an infection caused by the bacterial enteropathogen Yersinia pseudotuberculosis and is considered to be a significant problem in veterinary medicine. We previously found that intranasal administration of a recombinant Lactococcus lactis strain that secretes the low-calcium response V (LcrV) antigen from Y. pseudotuberculosis (Ll-LcrV) confers protection against a lethal Y. pseudotuberculosis infection. Here, we aimed at characterizing the immunological basis of this LcrV-elicited protective response and at determining the duration of vaccine-induced immunity.

METHODS

Splenocytes from BALB/c mice intranasally immunized with Ll-LcrV or Ll as control were immunostained then analyzed by flow cytometry. Protection against a lethal intravenous injection of Y. pseudotuberculosis was also determined (i) in immunized BALB/c mice depleted or not of CD4⁺, CD8⁺ or CD25⁺ cells and (ii) in naïve BALB/c mice receiving serum from immunized mice by counting the number of bacteria in liver and spleen. Lastly, survival rate of immunized BALB/c mice following a lethal intravenous injection of Y. pseudotuberculosis was followed up to 9-months.

RESULTS

We found that T and B lymphocytes but not non-conventional lymphoid cells were affected by Ll-LcrV immunization. We also observed that depletion of CD4⁺ and CD25⁺ but not CD8⁺ cells in immunized mice eradicated protection against a lethal systemic Y. pseudotuberculosis infection, suggesting that activated CD4⁺ T lymphocytes are required for vaccine-induced protection. Adoptive transfer of LcrV-specific antibodies from Ll-LcrV-immunized animals significantly reduced the bacterial counts in the liver compared to non-vaccinated mice. Lastly, the protective immunity conferred by Ll-LcrV decreased slightly over time; nevertheless almost 60% of the mice survived a lethal bacterial challenge at 9months post-vaccination.

CONCLUSION

Mucosal vaccination of mice with Ll-LcrV induced cell- and antibody-mediated protective immunity against Y. pseudotuberculosis infection in the mouse and the protection is long-lasting.

Biodegradable fibre scaffolds incorporating water-soluble drugs and proteins

A new type of biodegradable drug-loaded fibre scaffold has been successfully produced for the benefit of water-soluble drugs and proteins. Model drug loaded calcium carbonate (CaCO3) microparticles incorporated into poly(lactic acid-co-glycolic acid) (PLGA) fibres were manufactured by co-precipitation of CaCO3 and the drug molecules, followed by electrospinning of a suspension of such drug-loaded microparticles in a PLGA solution. Rhodamine 6G and bovine serum albumin were used as model drugs for our release study, representing small bioactive molecules and protein, respectively. A bead and string structure of fibres was achieved. The drug release was investigated with different drug loadings and in different pH release mediums. Results showed that a slow and sustained drug release was achieved in 40 days and the CaCO3 microparticles used as the second barrier restrained the initial burst release.

Proposed reclassification of Pasteurella lymphangitidis Sneath & Stevens 1990 as Yersinia pseudotuberculosis

The 16S rRNA gene sequences of Pasteurella lymphangitidis , Yersinia pseudotuberculosis and Yersinia pestis were found to be identical and multilocus sequence analysis could not discriminate between the three species. The susceptibility to a Y. pseudotuberculosis phage and the presence of the Y. pseudotuberculosis -specific invasin gene in P. lymphangitidis indicate that the latter should be reclassified as Y. pseudotuberculosis .

[Blood donor hemovigilance: impact for donor and recipient safety]

Since its creation in 1993, hemovigilance has an important place for blood safety. The part concerning donors, as the name suggests, targeted on improvement of donor's safety covers in fact the two points of the transfusion chain with serious adverse events in donor, epidemiologic survey for recipients and post-donation information on the two sides. Organized management and close collaboration between the actors of the transfusion chain are necessary to ensure the effectiveness of the system.

Efficacy of ciprofloxacin-gentamicin combination therapy in murine bubonic plague

Potential benefits of combination antibiotic therapy for the treatment of plague have never been evaluated. We compared the efficacy of a ciprofloxacin (CIN) and gentamicin (GEN) combination therapy with that of each antibiotic administered alone (i) against Yersinia pestis in vitro and (ii) in a mouse model of bubonic plague in which animals were intravenously injected with antibiotics for five days, starting at two different times after infection (44 h and 56 h). In vitro, the CIN+GEN combination was synergistic at 0.5x the individual drugs’ MICs and indifferent at 1x- or 2x MIC. In vivo, the survival rate for mice treated with CIN+GEN was similar to that observed with CIN alone and slightly higher than that observed for GEN alone 100, 100 and 85%, respectively when treatment was started 44 h post challenge. 100% of survivors were recorded in the CIN+GEN group vs 86 and 83% in the CIN and GEN groups, respectively when treatment was delayed to 56 h post-challenge. However, these differences were not statistically significant. Five days after the end of treatment, Y. pestis were observed in lymph nodes draining the inoculation site (but not in the spleen) in surviving mice in each of the three groups. The median lymph node log₁₀ CFU recovered from persistently infected lymph nodes was significantly higher with GEN than with CIN (5.8 vs. 3.2, p = 0.04) or CIN+GEN (5.8 vs. 2.8, p = 0.01). Taken as the whole, our data show that CIN+GEN combination is as effective as CIN alone but, regimens containing CIN are more effective to eradicate Y. pestis from the draining lymph node than the recommended GEN monotherapy. Moreover, draining lymph nodes may serve as a reservoir for the continued release of Y. pestis into the blood – even after five days of intravenous antibiotic treatment.

Multi-scale mechanical characterization of scaffolds for heart valve tissue engineering

Electrospinning is a promising technology to produce scaffolds for cardiovascular tissue engineering. Each electrospun scaffold is characterized by a complex micro-scale structure that is responsible for its macroscopic mechanical behavior. In this study, we focus on the development and the validation of a computational micro-scale model that takes into account the structural features of the electrospun material, and is suitable for studying the multi-scale scaffold mechanics. We show that the computational tool developed is able to describe and predict the mechanical behavior of electrospun scaffolds characterized by different microstructures. Moreover, we explore the global mechanical properties of valve-shaped scaffolds with different microstructural features, and compare the deformation of these scaffolds when submitted to diastolic pressures with a tissue engineered and a native valve. It is shown that a pronounced degree of anisotropy is necessary to reproduce the deformation patterns observed in the native heart valve.

[The management of post donation information: a fundamental element of blood safety]

Post donation information management is a fundamental axis of haemovigilance in terms of blood safety. It requires an organization ensuring a permanent reactivity, a good sensitization of French National Blood Service professionals and needs also a strong awareness of blood donors. Previous identification of stakeholders to warn during these kinds of alerts is essential to avoid the use of any blood product presenting a potential risk. The recent implementation of a consensual internal document aims to target the reinforcement of a homogeneous decision-making process, combining blood product self-sufficiency and above all recipient safety.

Autophagosomes can support Yersinia pseudotuberculosis replication in macrophages

Yersinia pseudotuberculosis is able to replicate inside macrophages. However, the intracellular trafficking of the pathogen after its entry into the macrophage remains poorly understood. Using in vitro infected bone marrow-derived macrophages, we show that Y. pseudotuberculosis activates the autophagy pathway. Host cell autophagosomes subverted by bacteria do not become acidified and sustain bacteria replication. Moreover, we report that autophagy inhibition correlated with bacterial trafficking inside an acidic compartment. This study indicates that Y. pseudotuberculosis hijacks the autophagy pathway for its replication and also opens up new opportunities for deciphering the molecular basis of the host cell signalling response to intracellular Yersinia infection.

Characterizing consumer health terminology in the breast cancer field

Despite the large availability of medical information on the Internet, health consumers still encounter problems to find, interpret and understand this information. These problems are mainly due to their lack in medical knowledge and the difference between their language and the language of health professionals. In order to propose information retrieval services more adapted to health consumers language and knowledge, we have developed techniques to collect, identify and analyze the terms and the expressions used by lay persons to talk about breast cancer. The study of health consumers' language is a relatively recent research field. Many studies have been conducted to analyze and characterize the vocabulary used by health consumers to talk about medical subjects in English. We have conducted the same study for the French language in the breast cancer field. We have gathered a corpus of texts to identify terms and expressions used by health consumers who talk about breast cancer in French. The terms have been organized in a concept-based terminology. This terminology has been analyzed on several levels: concept level, term level, term-concept level and finally relation level.

Hypoxic single-pass isolated hepatic perfusion of hypotonic Cisplatin: safety study in the pig

BACKGROUND

Isolated hepatic perfusion (IHP) of chemotherapy has been proposed to deliver high doses of drug while avoiding systemic toxicity. Hypotonic cisplatin has a high in vitro activity on human colon cancer cells. We studied the safety of a 30-min hypoxic single-pass IHP with hypotonic cisplatin.

METHODS

A preliminary in vitro assay was performed to compare the cytotoxicity of cisplatin and oxaliplatin, in either a normotonic or hypotonic medium. Cisplatin in hypotonic medium was then chosen for the in vivo IHP. Eleven pigs underwent 30 min of IHP with 0, 50, 75, or 100 mg/L of cisplatin in a hypotonic solution under total vascular exclusion of the liver. Clinical and biological parameters were recorded for 30 days, and liver histology was performed at necropsy. The cytotoxic activity of the effluent against resistant human colon cancer cells was tested in vitro.

RESULTS

No hepatic failure was recorded after IHP with cisplatin, but limited foci of necrosis were found at necropsy in animals receiving 75 or 100 mg/L of cisplatin. No clinical, biological, macroscopic, or microscopic toxicity was observed after IHP with 50 mg/L of hypotonic cisplatin. The liver effluent showed high in vitro cytotoxic activity against colon cancer cells.

CONCLUSIONS

A hypoxic single-pass isolated liver perfusion with hypotonic cisplatin is feasible and safe. Effluent from the liver is highly cytotoxic on cancer cells. A clinical study with 50 mg/L of hypotonic cisplatin is warranted in patients with unresectable liver metastases from colon cancer.

Toll-like receptor 2 is critical for induction of Reg3 beta expression and intestinal clearance of Yersinia pseudotuberculosis

OBJECTIVE

Yersinia pseudotuberculosis causes ileitis and mesenteric lymphadenitis by mainly invading the Peyer's patches that are positioned in the terminal ileum. Whereas toll-like-receptor 2 (TLR2) controls mucosal inflammation by detecting certain microbiota-derived signals, its exact role in protecting Peyer's patches against bacterial invasion has not been defined.

DESIGN

Wild-type, Tlr2-, Nod2- and MyD88-deficient animals were challenged by Y pseudotuberculosis via the oral or systemic route. The role of microbiota in conditioning Peyer's patches against Yersinia through TLR2 was assessed by delivering, ad libitum, exogenous TLR2 agonists in drinking water to germ-free and streptomycin-treated animals. Bacterial eradication from Peyer's patches was measured by using a colony-forming unit assay. Expression of cryptdins and the c-type lectin Reg3 beta was quantified by quantitative reverse transcriptase polymerase chain reaction analysis.

RESULTS

Our data demonstrated that Tlr2-deficient mice failed to limit Yersinia dissemination from the Peyer's patches and succumbed to sepsis independently of nucleotide-binding and oligomerisation domain 2 (NOD2). Recognition of both microbiota-derived and myeloid differentiation factor 88 (MyD88)-mediated elicitors was found to be critically involved in gut protection against Yersinia-induced lethality, while TLR2 was dispensable to systemic Yersinia infection. Gene expression analyses revealed that optimal epithelial transcript level of the anti-infective Reg3 beta requires TLR2 activation. Consistently, Yersinia infection triggered TLR2-dependent Reg3 beta expression in Peyer's patches. Importantly, oral treatment with exogenous TLR2 agonists in germ-free animals was able to further enhance Yersinia-induced expression of Reg3 beta and to restore intestinal resistance to Yersinia. Lastly, genetic ablation of Reg3 beta resulted in impaired clearance of the bacterial load in Peyer's patches.

CONCLUSIONS

TLR2/REG3 beta is thus an essential component in conditioning epithelial defence signalling pathways against bacterial invasion.

An iron-regulated LysR-type element mediates antimicrobial peptide resistance and virulence in Yersinia pseudotuberculosis

During the course of its infection of the mammalian digestive tract, the entero-invasive, Gram-negative bacterium Yersinia pseudotuberculosis must overcome various hostile living conditions (notably, iron starvation and the presence of antimicrobial compounds produced in situ). We have previously reported that in vitro bacterial growth during iron deprivation raises resistance to the antimicrobial peptide polymyxin B; here, we show that this phenotype is mediated by a chromosomal gene (YPTB0333) encoding a transcriptional regulator from the LysR family. We determined that the product of YPTB0333 is a pleiotropic regulator which controls (in addition to its own expression) genes encoding the Yfe iron-uptake system and polymyxin B resistance. Lastly, by using a mouse model of oral infection, we demonstrated that YPTB0333 is required for colonization of Peyer's patches and mesenteric lymph nodes by Y. pseudotuberculosis.

Protection against Yersinia pseudotuberculosis infection conferred by a Lactococcus lactis mucosal delivery vector secreting LcrV

Herein, we sought to evaluate the potential of a recombinant Lactococcus lactis strain secreting the Yersinia pseudotuberculosis low-calcium response V (LcrV) antigen for mucosal vaccination against Yersinia infections. We showed that the recombinant strain induced specific systemic and mucosal antibody and cellular immune responses after intranasal immunization and protected mice against both oral and systemic Y. pseudotuberculosis infections. This constitutes the first proof of principle for a novel anti-Yersinia mucosal vaccination strategy using recombinant lactic acid bacteria.

Growth of Yersinia pseudotuberculosis in human plasma: impacts on virulence and metabolic gene expression

BACKGROUND

In man, infection by the Gram-negative enteropathogen Yersinia pseudotuberculosis is usually limited to the terminal ileum. However, in immunocompromised patients, the microorganism may disseminate from the digestive tract and thus cause a systemic infection with septicemia.

RESULTS

To gain insight into the metabolic pathways and virulence factors expressed by the bacterium at the blood stage of pseudotuberculosis, we compared the overall gene transcription patterns (the transcriptome) of bacterial cells cultured in either human plasma or Luria-Bertani medium. The most marked plasma-triggered metabolic consequence in Y. pseudotuberculosis was the switch to high glucose consumption, which is reminiscent of the acetogenic pathway (known as "glucose overflow") in Escherichia coli. However, upregulation of the glyoxylate shunt enzymes suggests that (in contrast to E. coli) acetate may be further metabolized in Y. pseudotuberculosis. Our data also indicate that the bloodstream environment can regulate major virulence genes (positively or negatively); the yadA adhesin gene and most of the transcriptional units of the pYV-encoded type III secretion apparatus were found to be upregulated, whereas transcription of the pH6 antigen locus was strongly repressed.

CONCLUSION

Our results suggest that plasma growth of Y. pseudotuberculosis is responsible for major transcriptional regulatory events and prompts key metabolic reorientations within the bacterium, which may in turn have an impact on virulence.

Sudden onset of pseudotuberculosis in humans, France, 2004-05

Cases of Yersinia pseudotuberculosis infection increased in France during the winter of 2004-05 in the absence of epidemiologic links between patients or strains. This increase represents transient amplification of a pathogen endemic to the area and may be related to increased prevalence of the pathogen in rodent reservoirs.

Skeletal myogenesis on highly orientated microfibrous polyesterurethane scaffolds

Skeletal myogenesis is a complex process, which is known to be intimately depending on an optimal outside-in substrate-cell signaling. Current attempts to reproduce skeletal muscle tissue in vitro using traditional scaffolds mainly suffer from poor directionality of the myofibers, resulting in an ineffective vectorial power generation. In this study, we aimed at investigating skeletal myogenesis on novel biodegradable microfibrous scaffolds made of DegraPol, a block polyesterurethane previously demonstrated to be suitable for this application. DegraPol was processed by electrospinning in the form of highly orientated ("O") and nonorientated ("N/O") microfibrous meshes and by solvent-casting in the form of nonporous films ("F"). The effect of the fiber orientation at the scaffold surface was evaluated by investigating C2C12 and L6 proliferation (via SEM analysis and alamarBlue test) and differentiation (via RT-PCR analysis and MHC immunostaining). We demonstrated that highly orientated elastomeric microfibrous DegraPol scaffolds enable skeletal myogenesis in vitro by aiding in (a) myoblast adhesion, (b) myotube alignment, and (c) noncoplanar arrangement of cells, by providing the necessary directional cues along with architectural and mechanical support.

Transcriptome analysis of Yersinia pestis in human plasma: an approach for discovering bacterial genes involved in septicaemic plague

Yersinia pestis is the aetiologic agent of plague. Without appropriate treatment, the pathogen rapidly causes septicaemia, the terminal and fatal phase of the disease. In order to identify bacterial genes which are essential during septicaemic plague in humans, we performed a transcriptome analysis on the fully virulent Y. pestis CO92 strain grown in either decomplemented human plasma or Luria-Bertani medium, incubated at either 28 or 37 degrees C and harvested at either the mid-exponential or the stationary growth phase. Y. pestis genes involved in 12 iron-acquisition systems and one iron-storage system (bfr, bfd) were specifically induced in human plasma. Of these, the ybt and tonB genes (encoding the yersiniabactin siderophore virulence factor and the siderophore transporter, respectively) were induced at 37 degrees C, i.e. under conditions mimicking the mammalian environment. Growth in human plasma also upregulated genes involved in the synthesis of five fimbrial-like structures (including the Psa virulence factor), and in purine/pyrimidine metabolism (the nrd genes). Genes known to play a role in the virulence of several bacterial pathogens (such as those encoding the Lpp lipoprotein and non-iron metal-uptake proteins) were induced in human plasma, during either the exponential or the stationary phase. Finally, 120 genes encoding proteins of unknown function were upregulated in human plasma. Eleven of these genes were specifically transcribed at 37 degrees C and may thus represent new virulence factors that are important during the septicaemic phase of human plague.

Prevention and treatment of colitis with Lactococcus lactis secreting the immunomodulatory Yersinia LcrV protein

BACKGROUND & AIMS

The low calcium response V (LcrV) protein synthesized by gram-negative, pathogenic yersiniae participates in bacterial evasion of the host's innate immune response by stimulating synthesis of the anti-inflammatory interleukin (IL)-10 and preventing the activation of proinflammatory cytokines.

METHODS

We genetically engineered the food-grade bacterium Lactococcus lactis to secrete the LcrV protein from the enteropathogenic species Yersinia pseudotuberculosis. The protective and therapeutic potential of orally administered LcrV-secreting L lactis was evaluated in 2 models of acute experimental colitis (induced by trinitrobenzene sulfonic acid [TNBS] and dextran sodium sulfate [DSS], respectively) in wild-type and knockout mice.

RESULTS

Oral administration of LcrV-secreting L lactis led to active delivery of LcrV and induction of IL-10 (via a Toll-like receptor 2-dependent pathway) in the colon and prevented TNBS-induced colitis, in contrast to the L lactis control not producing LcrV. Down-regulation of tissue inflammatory markers correlated well with the reduction in damage to the colonic mucosa. In contrast, TNBS-induced colitis was not prevented in IL-10(-/-) mice pretreated with LcrV-secreting L lactis, thus showing that IL-10 is required for LcrV protection. Administration of LcrV-secreting L lactis also proved to be very effective in preventing and treating acute DSS-induced colitis.

CONCLUSIONS

LcrV-secreting L lactis decreased experimentally induced intestinal inflammation in 2 murine models of colitis. This novel approach highlights the potential of using pathogen-derived immunomodulating molecules in vivo as novel therapeutics for inflammatory bowel diseases.

Phenotypic analysis of Yersinia pseudotuberculosis 32777 response regulator mutants: new insights into two-component system regulon plasticity in bacteria

Two-component regulatory systems (2CSs) typically comprise a sensor kinase and a response regulator that, in concert, monitor the concentration of particular extracellular factors and mediate the transcription of specific genes accordingly. As such, 2CSs play an important role in the regulation of bacterial pathogenesis. On the basis of genome-wide in silico analysis, the Gram-negative enteropathogenic bacterium Yersinia pseudotuberculosis is thought to encode 24 complete 2CSs. In the present work, we mutated the corresponding 2CS response regulator-encoding genes in Y. pseudotuberculosis strain 32777 and assessed the in vitro resistance of each mutant to the various types of stress encountered by Yersinia cells in the digestive tract. Eight of the generated regulatory mutants (phoP, ompR, pmrA, ntrC-, arcA-, rstA-, rcsB-, and yfhA-like mutants) showed significant changes in tolerance towards at least one type of stress, when compared with the wild-type strain. Of these eight, four (ompR, phoP, rstA-, and yfhA-like mutants) were found to be less virulent than the wild type in the BALB/c mouse model. Although some mutant phenotypes were consistent with those (when known) of the corresponding, putative ortholog mutants in other pathogenic species, several response regulators behaved differently in Y. pseudotuberculosis; these included the PmrA, PhoP, and ArcA-like response regulators, which were found to control bile salt resistance in a manner different from that observed in Salmonella. Hence, in addition to genome evolution, transcriptional network remodeling may be a major cause of phenotypic adaptation (and thus species divergence) in Y. pseudotuberculosis.

Similarities of Kawasaki disease and Yersinia pseudotuberculosis infection epidemiology

Although an infectious etiology is strongly suspected in Kawasaki disease (KD), an etiologic agent has not yet been identified. By reviewing epidemiologic data published in past decades, this work highlights a higher incidence of KD when populations were exposed to the risk of Yersinia pseudotuberculosis infection. This hitherto unnoticed element reinforces the hypothesis whereby this bacterium might contribute to the development of KD in some cases.

NODs in defence: from vulnerable antimicrobial peptides to chronic inflammation

Defensins and cathelicidins are prevalent and essential gastrointestinal cationic antimicrobial peptides (CAPs). However, these defensive peptides are not infallible because certain enteropathogens can overcome their protective function. Furthermore, impaired defensin synthesis has been linked to the occurrence of Crohn's disease (CD), a chronic inflammatory bowel disease. Recently, defective bacterial sensing through NOD1 and NOD2 has been related to reduced defensin production, CD predisposition and susceptibility to enteric infection. Hence, we propose that microbial sensors at the gut interface monitor the levels of these effector peptides, which might function as "danger" signals to confer tolerance and alert immunocytes. Further work is required to clarify how gastrointestinal CAPs are regulated and to assess their role in maintaining epithelial homeostasis and triggering adaptive immunity.

High intra-abdominal pressure enhances the penetration and antitumor effect of intraperitoneal cisplatin on experimental peritoneal carcinomatosis

OBJECTIVE

To investigate the role of increased intra-abdominal pressure (IAP) on the intratumoral accumulation and the antitumor effect of intraperitoneal cisplatin in rats with advanced peritoneal carcinomatosis. To evaluate the tolerance of IAP in pigs, as it is a large animal with a body size equivalent to humans.

SUMMARY BACKGROUND DATA

To investigate if an active convection, driven by a positive IAP, increases cisplatin penetration and antitumor effectiveness in a model of advanced peritoneal carcinomatosis in rats.

EXPERIMENTAL DESIGN

BDIX rats with macroscopic peritoneal tumors received cisplatin administered as intravenous injection (IV), conventional intraperitoneal injection (IP), or sustained intraperitoneal injection of cisplatin given in a large volume of solvent for maintaining IAP for 1 hour. Platinum tissue concentration was measured by atomic absorption spectroscopy (AAS), and platinum distribution into the tumor nodules was assessed by the particular-induced x-ray emission (PIXE) method. The antitumor effect was assessed in a survival experiment. The hemodynamic, local, and systemic tolerance of IAP, with or without cisplatin, was evaluated in Large White pigs.

RESULTS

The maximum tolerated IAP was 22 mm Hg for 1 hour in nonventilated rats. IAP, in comparison with IV or conventional IP injections, resulted in the increased concentration and depth of diffusion of platinum into diaphragm and peritoneal tumor nodules. Consequently, IAP treatment induced an extended survival of rats treated at an advanced stage of carcinomatosis. In 7 50- to 70-kg ventilated pigs, a 40-mm Hg IAP was well tolerated when maintained stable for 2 hours. Renal failure occurred in pigs receiving a total dose of 200 and 400 mg of cisplatin with IAP, but a dose of 100 mg was well tolerated.

CONCLUSIONS

Intraperitoneal chemotherapy with increased IAP, in comparison with conventional IP or IV chemotherapy, improved the tumor accumulation and the antitumor effect of cisplatin in rats bearing advanced peritoneal carcinomatosis. In preclinical conditions, the tolerance of sustained IAP was manageable in ventilated pigs.

Describing ancient horizontal gene transfers at the nucleotide and gene levels by comparative pathogenicity island genometrics

MOTIVATION

Lateral gene transfer is a major mechanism contributing to bacterial genome dynamics and pathovar emergence via pathogenicity island (PAI) spreading. However, since few of these genomic exchanges are experimentally reproducible, it is difficult to establish evolutionary scenarios for the successive PAI transmissions between bacterial genera. Methods initially developed at the gene and/or nucleotide level for genomics, i.e. comparisons of concatenated sequences, ortholog frequency, gene order or dinucleotide usage, were combined and applied here to homologous PAIs: we call this approach comparative PAI genometrics.

RESULTS

YAPI, a Yersinia PAI, and related islands were compared with measure evolutionary relationships between related modules. Through use of our genometric approach designed for tracking codon usage adaptation and gene phylogeny, an ancient inter-genus PAI transfer was oriented for the first time by characterizing the genomic environment in which the ancestral island emerged and its subsequent transfers to other bacterial genera.

Linkage of the horizontally acquired ypm and pil genes in Yersinia pseudotuberculosis

The superantigen-encoding ypm gene and the pil gene cluster governing type IV pilus biogenesis have been laterally acquired by Yersinia pseudotuberculosis. PCR assays on 270 unrelated strains from various environmental and animal sources revealed a significant association of ypm and pil in isolates.

A Multi-Source Information System via the Internet for End-Stage Renal Disease: Scalability and Data Quality

A Multi-Source Information System (MSIS), has been designed for the Renal Epidemiology and Information Network (REIN) dedicated to End-Stage Renal Disease (ESRD). MSIS aims at providing reliable follow-up data for ESRD patients. It is based on an n-tier architecture, made out of a universal client, a dynamic Web server connected to a production database and to a data warehouse. MSIS is operational since 2002 and progressively deployed in 9 regions in France. It includes 11,500 patients. MSIS facilitates documenting medical events which occur during the course of ESRD patient' health care and provides means to control the quality of each patient's record and reconstruct the patient trajectory of care. Consolidated data are made available to a data warehouse and to a geographic information system for analysis and data representation in support of public-health decision making.

The pmrF polymyxin-resistance operon of Yersinia pseudotuberculosis is upregulated by the PhoP-PhoQ two-component system but not by PmrA-PmrB, and is not required for virulence

The Yersinia pseudotuberculosis chromosome contains a seven-gene polycistronic unit (the pmrF operon) whose products share extensive homologies with their pmrF counterparts in Salmonella enterica serovar Typhimurium (S. typhimurium), another Gram-negative bacterial enteropathogen. This gene cluster is essential for addition of 4-aminoarabinose to the lipid moiety of LPS, as demonstrated by MALDI-TOF mass spectrometry of lipid A from both wild-type and pmrF-mutated strains. As in S. typhimurium, 4-aminoarabinose substitution of lipid A contributes to in vitro resistance of Y. pseudotuberculosis to the antimicrobial peptide polymyxin B. Whereas pmrF expression in S. typhimurium is mediated by both the PhoP-PhoQ and PmrA-PmrB two-component regulatory systems, it appears to be PmrA-PmrB-independent in Y. pseudotuberculosis, with the response regulator PhoP interacting directly with the pmrF operon promoter region. This result reveals that the ubiquitous PmrA-PmrB regulatory system controls different regulons in distinct bacterial species. In addition, pmrF inactivation in Y. pseudotuberculosis has no effect on bacterial virulence in the mouse, again in contrast to the situation in S. typhimurium. The marked differences in pmrF operon regulation in these two phylogenetically close bacterial species may be related to their dissimilar lifestyles.

The response regulator PhoP of Yersinia pseudotuberculosis is important for replication in macrophages and for virulence

Yersinia pestis and Yersinia pseudotuberculosis are closely related facultative intracellular pathogens. The response regulator PhoP was previously shown to be important for Y. pestis survival in macrophages and for virulence in a murine bubonic plague infection assay. Here the importance of PhoP for Y. pseudotuberculosis pathogenesis was investigated. Y. pseudotuberculosis phoP mutants were unable to replicate in low-Mg(2+) medium or in macrophages. phoP(+) Y. pseudotuberculosis strains initiated replication in macrophages after a lag period of approximately 5 h, as shown by fluorescence microscopy and viable count assays. Y. pseudotuberculosis phoP mutants died at a low rate in macrophages; there was no decrease in viability over the first 5 h of infection, and there was a 10-fold decrease in viability between 5 and 24 h of infection. Trafficking of phagosomes containing phoP(+) or phoP mutant Y. pseudotuberculosis was studied by using immunofluorescence microscopy and cathepsin D as a marker for lysosomes. Phagosomes containing phoP mutant Y. pseudotuberculosis acquired cathepsin D at a higher rate than phagosomes containing phoP(+) bacteria. However, the increased rate of marker acquisition for phagosomes containing mutant bacteria was only evident approximately 5 h after infection, suggesting that phoP mutants are able to retard phagosome maturation during the lag phase of intracellular growth. The results obtained with a Y. pestis phoP mutant were similar to those described above, except that the rates of intracellular killing and trafficking to cathepsin D-positive vacuoles were significantly higher. A Y. pseudotuberculosis phoP mutant was 100-fold less virulent than the wild-type strain in a murine intestinal infection model, suggesting that survival and replication in macrophages are important for Y. pseudotuberculosis pathogenesis.

Insights into the evolution of Yersinia pestis through whole-genome comparison with Yersinia pseudotuberculosis

Yersinia pestis, the causative agent of plague, is a highly uniform clone that diverged recently from the enteric pathogen Yersinia pseudotuberculosis. Despite their close genetic relationship, they differ radically in their pathogenicity and transmission. Here, we report the complete genomic sequence of Y. pseudotuberculosis IP32953 and its use for detailed genome comparisons with available Y. pestis sequences. Analyses of identified differences across a panel of Yersinia isolates from around the world reveal 32 Y. pestis chromosomal genes that, together with the two Y. pestis-specific plasmids, to our knowledge, represent the only new genetic material in Y. pestis acquired since the the divergence from Y. pseudotuberculosis. In contrast, 149 other pseudogenes (doubling the previous estimate) and 317 genes absent from Y. pestis were detected, indicating that as many as 13% of Y. pseudotuberculosis genes no longer function in Y. pestis. Extensive insertion sequence-mediated genome rearrangements and reductive evolution through massive gene loss, resulting in elimination and modification of preexisting gene expression pathways, appear to be more important than acquisition of genes in the evolution of Y. pestis. These results provide a sobering example of how a highly virulent epidemic clone can suddenly emerge from a less virulent, closely related progenitor.

YAPI, a new Yersinia pseudotuberculosis pathogenicity island

Pathogenicity islands (PAIs) are chromosomal clusters of pathogen-specific virulence genes often found at tRNA loci. In the Yersinia pseudotuberculosis 32777 chromosome, we characterized a 98-kb segment that has all of the characteristic features of a PAI, including insertion in a (phenylalanine) tRNA gene, the presence of a bacteriophage-like integrase-encoding gene, and direct repeats at the integration sites. The G+C content of the segment ranges from 31 to 60%, reflecting a genetic mosaic: this is consistent with the notion that the sequences were horizontally acquired. The PAI, termed YAPI (for Yersinia adhesion pathogenicity island), carries 95 open reading frames and includes (i) the previously described pil operon, encoding a type IV pilus that contributes to pathogenicity (F. Collyn et al., Infect. Immun. 70:6196-6205, 2002); (ii) a block of genes potentially involved in general metabolism; (iii) a gene cluster for a restriction-modification system; and (iv) a large number of mobile genetic elements. Furthermore, the PAI can excise itself from the chromosome at low frequency and in a precise manner, and deletion does not result in a significant decrease of bacterial virulence compared to inactivation of the fimbrial gene cluster alone. The prevalence and size of the PAI vary from one Y. pseudotuberculosis strain to another, and it can be found integrated into either of the two phe tRNA loci present on the species' chromosome. YAPI was not detected in the genome of the genetically closely related species Y. pestis, whereas a homologous PAI is harbored by the Y. enterocolitica chromosome.

Yersinia pseudotuberculosis anti-inflammatory components reduce trinitrobenzene sulfonic acid-induced colitis in the mouse

Rectal instillation of trinitrobenzene sulfonic acid (TNBS) induces acute colitis in the mouse. We tested the efficacy of Yersinia pseudotuberculosis anti-inflammatory components in preventing TNBS-triggered colitis. Animals were orally inoculated with virulence-attenuated Yersinia cells (a phoP mutant) prior to TNBS administration. Under these experimental conditions, colonic lesions and tumor necrosis factor alpha mRNA levels were significantly reduced.

A dynamic Web application within an n-tier architecture: a Multi-Source Information System for end-stage renal disease

A Multi-Source Information System (MSIS) has been designed for the Renal Epidemiology and Information Network (REIN) dedicated to End-Stage Renal Disease. Interoperability has been considered at 4 levels: semantics, network, formats and contents. An n-tier architecture has been chosen at the network level. It is made out of a universal client, a dynamic Web server connected to a production database and to a data warehouse. The MSIS is patient-oriented, based on a regional organization. Its implementation in the context of a regional experimentation is presented with insights on the design and underlying technologies. The n-tier architecture is a robust model and flexible enough to aggregate multiple information sources and integrate modular developments. The data warehouse is dedicated to support health care decision-making.

Yersinia pseudotuberculosis harbors a type IV pilus gene cluster that contributes to pathogenicity

Fimbriae have been shown to play an essential role in the adhesion of pathogenic gram-negative bacteria to host cells. In the enteroinvasive bacterium Yersinia pseudotuberculosis, we characterized a previously unknown 11-kb chromosomal locus involved in the synthesis of type IV pili. The locus consists of 11 open reading frames forming a polycistronic unit and encoding putative Pil proteins, PilLMNOPQRSUVW. When introduced into Escherichia coli, the Y. pseudotuberculosis operon reconstituted bundles of filaments at a pole on the bacterial surface, demonstrating that the pil locus was functional in a heterogenous genetic background. Environmental factors regulated transcription of the Y. pseudotuberculosis operon; in particular, temperature, osmolarity, and oxygen tension were critical cues. Deletion of the type IV pilus gene cluster was associated with a reduction of Y. pseudotuberculosis pathogenicity for mice infected orally. Forty-one percent of Y. pseudotuberculosis strains isolated from human or animal sources harbored the type IV pilus locus. Therefore, the pil locus of Y. pseudotuberculosis might constitute an "adaptation island," permitting the microorganism to colonize a vast reservoir.

Genes encoding specific nickel transport systems flank the chromosomal urease locus of pathogenic yersiniae

The transition metal nickel is an essential cofactor for a number of bacterial enzymes, one of which is urease. Prior to its incorporation into metalloenzyme active sites, nickel must be imported into the cell. Here, we report identification of two loci corresponding to nickel-specific transport systems in the gram-negative, ureolytic bacterium Yersinia pseudotuberculosis. The loci are located on each side of the chromosomal urease gene cluster ureABCEFGD and have the same orientation as the latter. The yntABCDE locus upstream of the ure genes encodes five predicted products with sequence homology to ATP-binding cassette nickel permeases present in several gram-negative bacteria. The ureH gene, located downstream of ure, encodes a single-component carrier which displays homology to polypeptides of the nickel-cobalt transporter family. Transporters with homology to these two classes are also present (again in proximity to the urease locus) in the other two pathogenic yersiniae, Y. pestis and Y. enterocolitica. An Escherichia coli nikA insertion mutant recovered nickel uptake ability following heterologous complementation with either the ynt or the ureH plasmid-borne gene of Y. pseudotuberculosis, demonstrating that each carrier is necessary and sufficient for nickel transport. Deletion of ynt in Y. pseudotuberculosis almost completely abolished bacterial urease activity, whereas deletion of ureH had no effect. Nevertheless, rates of nickel transport were significantly altered in both ynt and ureH mutants. Furthermore, the ynt ureH double mutant was totally devoid of nickel uptake ability, thus indicating that Ynt and UreH constitute the only routes for nickel entry. Both Ynt and UreH show selectivity for Ni(2+) ions. This is the first reported identification of genes coding for both kinds of nickel-specific permeases situated adjacent to the urease gene cluster in the genome of a microorganism.

The superantigen gene ypm is located in an unstable chromosomal locus of Yersinia pseudotuberculosis

Yersinia pseudotuberculosis produces YPM (Y. pseudotuberculosis-derived mitogen), a superantigenic toxin that exacerbates the virulence of the bacterium in vivo. To date, three alleles of the superantigen gene (ypmA, ypmB, and ypmC) have been described. These genes are not found in all Y. pseudotuberculosis strains and have a low GC content, suggesting their location on mobile genetic elements. To elucidate this question, the genetic environment of the superantigen-encoding genes was characterized and 11 open reading frames (ORFs) were defined. Sequence analysis revealed that the ypm genes were not associated with plasmids, phages, transposons, or pathogenicity islands and that the superantigen genes were always located in the chromosome between ORF3 and ORF4. Nonsuperantigenic strains exhibited the same genetic organization of the locus but lacked the ypm gene between ORF3 and ORF4. A new insertion sequence, designated IS1398, which displays features of the Tn3 family, was characterized downstream of the ypmA and ypmC genes. A 13.3-kb region containing the ypm genes was not found in the genome of Y. pestis (CO92 and KIM 5 strains). We experimentally induced deletion of the ypm gene from a superantigen-expressing Y. pseudotuberculosis: using the association of aph(3')-IIIa and sacB genes, we demonstrated that when these reporter genes were present in the ypm locus, deletion of these genes was about 250 times more frequent than when they were located in another region of the Y. pseudotuberculosis chromosome. These results indicate that unlike other superantigenic toxin genes, the Yersinia ypm genes are not associated with mobile genetic elements but are inserted in an unstable locus of the genome.

The Yersinia pseudotuberculosis Yut protein, a new type of urea transporter homologous to eukaryotic channels and functionally interchangeable in vitro with the Helicobacter pylori UreI protein

Urea uptake in eukaryotes and prokaryotes occurs via diffusion or active transport across the cell membrane. Facilitated diffusion of urea in both types of organisms requires a single-component channel. In bacteria, these transport systems allow rapid access of urease to its substrate, resulting in ammonia production, which is needed either for resistance to acidity or as a nitrogen source. In Yersinia pseudotuberculosis, a ureolytic enteropathogenic bacterium, a gene of unknown function (yut) located near the urease locus was found to encode a putative membrane protein with weak homology to single-component eukaryotic urea transporters. When expressed in Xenopus oocytes, Yut greatly increases cellular permeability to urea. Inactivation of yut in Y. pseudotuberculosis results in diminished apparent urease activity and reduced resistance to acidity in vitro when urea is present in the medium. In the mouse model, bacterial colonization of the intestine mucosa is delayed with the Yut-deficient mutant. Although structurally unrelated, Yut and the Helicobacter pylori UreI urea channel were shown to be functionally interchangeable in vitro and are sufficient to allow urea uptake in both bacteria, thereby confirming their function in the respective parent organisms. Homologues of Yut were found in other yersiniae, Actinobacillus pleuropneumoniae, Brucella melitensis, Pseudomonas aeruginosa and Staphylococcus aureus. The Y. pseudotuberculosis Yut protein is therefore the first member of a novel class of bacterial urea permeases related to eukaryotic transporters.