Physiopathology of Pseudomonas aeruginosa pneumonia : involvement of alveolar epithelial cells through IL-22 and role of the immune escape

Pseudorrwnas aeruginosa (PA) est un pathogène opportuniste responsable de pneumonies nosocomiales chez les patients immunodéprimés. L'émergence des souches multirésistantes rend les traitements antibiotiques inefficaces nécessitant la mise en place de thérapeutiques alternatives. Les cellules épithéliales alvéolaires (AEC) constituent la première barrière physique que rencontre PA et ces cellules jouent un rôle important dans la réponse innée suite à l'infection. L'interleukine(IL)-22 est une cytokine dont l'intérêt thérapeutique est prometteur de par son action de protection des épithéliums. Le renforcement de la barrière épithéliale par le traitement à l'IL-22 a montré des effets protecteurs contre l'infection à PA dans un modèle murin de pneumonie. Nous avons caractérisé l'action in vitro de l'IL-22 au cours de l'infection à PA en utilisant une lignée transformée d' AEC de type II et nous avons démontré que cette cytokine potentialise l'expression d'interférons lambda (IFN°À) connus pour être bénéfiques au cours des infections virales. L'administration in vivo d'IFN-À dans un modèle murin de pneumonie aiguë à PA montre une amélioration significative de la pathologie accompagnée d'une réduction du recrutement de polynucléaires neutrophiles. PA est un pathogène capable d'échappement immunitaire lors de la mise en place de la réponse de l'hôte au cours de l'infection. En développant ex vivo un modèle de granulome à PA, nous avons observé une augmentation d'expression des 1,. molécules PD-Ll sur les monocytes. Ceci suggère une implication de la voie PD-I/PD-Ll dans l'épuisement lymphocytaire au cours de l'infection à PA.Pseudorrwnas aeruginosa (PA) is an opportunistic pathogen, and a leading cause of nosocomial infections, Emergence of multidrug resistant strains alter antibiotic efficacy and requires the development of alternative therapeutics. Alveolar epithelial cells (AEC) are the first line of defence against PA and play a crucial role in initiating immune response following infection. Interleukin (IL)-22 is cytokine recently discovered acting specifically onto epithelial cells. IL-22 is a promising therapeutic when considering its epithelium protective action during infections. Reinforcement of epithelial barrier by IL-22 treatment showed protective effects against PA in a murine pneumonia model. We here characterized the in vitro IL-22 effects during PA infection by using transformed cell line of AEC type II and showed enhanced Interferons lambda (IFN-À) production, which are known to be protective against viral infection. In vivo IFN-À administration in a murine model of acute PA pneumonia showed significant pathology improvement and dampened neutrophil recruitment. PA is a pathogen able to interfere and to escape the host response during infection. To study the mechanisms of immune escape and subversion of PA during host response, we developed an in vitro granuloma model following PA infection. We showed a significant induction of PD-LI expression in monocytes suggesting a PD- I/PD-LI involvement in T cells exhaustion during PA infection

DFT Studies on Electronic, Elastic, Thermoelectric and Optical Properties of New Half-Heusler XRhZ (X = V, Nb and Z = Si, Ge) Semiconductors

Density functional theory is used to explore the physical properties of the new half-Heusler alloys XRhZ (X =V, Nb and Z = Si, Ge). The exchange-correlation effects were treated by the TB-mBJ potential. The four studied compounds are nonmagnetic semiconductor with an indirect band gap. The formation enthalpy, cohesive energy and phonon band structures demonstrated that these semiconductors are structurally and dynamically stable. It was predicted by the elastic study that the XRhZ compounds (X = V, Nb and Z = Si, Ge) have stable mechanical properties, they possess an anisotropic character and reveal the ductile nature with a B/G ratio >1.75. The optical results show an interesting photocatalytic potential for the NbRhSi and NbRhGe semiconductors; they exhibit a high absorption coefficient in the visible domain, which is around 112.104 cm-1. For energies greater than 10 eV (UV domain), the refractive index is less than one. The thermoelectric results confirmed that the XRhZ (X=V, Nb and Z=Si, Ge) compounds are very attractive for thermoelectric devices working in large temperature range including ambient temperature

Interleukin-22 regulates interferon lambda expression in a mice model of pseudomonas aeruginosa pneumonia

International audienceBackground:Interleukin (IL)-22 is a cytokine involved in tissue protection and repair following lung pathologies.Interferon (IFN)-λcytokines displayed similar properties during viral infection and a synergy of action betweenthese two players has been documented in the intestine. We hypothesize that duringPseudomonas aeruginosachallenge, IL-22 up-regulates IFN-λand that IFN-λexhibits protective functions duringPseudomonas aeruginosaacute pneumonia model in mice.Methods:Using an in vitro human alveolar epithelial cell line A549, we assessed the ability of IL-22 to enhanceIFN-λexpression during infection. IFN-λprotective function was evaluated in an acute mouse pneumonia model.Results:Wefirst demonstrated in murine lungs that only type-II alveolar cells express IL-22 receptor and that IL-22 treatment of A549 cell line up-regulates IFN-λexpression. In a murine acute pneumonia model, IL-22 ad-ministration maintained significant IFN-λlevels in the broncho-alveolarfluids whereas IL-22 neutralizationabolished IFN-λup-regulation. In vivo administration of IFN-λduringPseudomonas aeruginosapneumonia im-proves mice outcome by dampening neutrophil recruitment and decreasing epithelium damages.Discussion:We show here that IL-22 regulates IFN-λlevels duringPseudomonas aeruginosapneumonia

Hyperinvasive Meningococci Induce Intra-nuclear Cleavage of the NF-κB Protein p65/RelA by Meningococcal IgA Protease.

International audienceDifferential modulation of NF-κB during meningococcal infection is critical in innate immune response to meningococcal disease. Non-invasive isolates of Neisseria meningitidis provoke a sustained NF-κB activation in epithelial cells. However, the hyperinvasive isolates of the ST-11 clonal complex (ST-11) only induce an early NF-κB activation followed by a sustained activation of JNK and apoptosis. We show that this temporal activation of NF-κB was caused by specific cleavage at the C-terminal region of NF-κB p65/RelA component within the nucleus of infected cells. This cleavage was mediated by the secreted 150 kDa meningococcal ST-11 IgA protease carrying nuclear localisation signals (NLS) in its α-peptide moiety that allowed efficient intra-nuclear transport. In a collection of non-ST-11 healthy carriage isolates lacking NLS in the α-peptide, secreted IgA protease was devoid of intra-nuclear transport. This part of iga polymorphism allows non-invasive isolates lacking NLS, unlike hyperinvasive ST-11 isolates of N. meningitides habouring NLS in their α-peptide, to be carried asymptomatically in the human nasopharynx through selective eradication of their ability to induce apoptosis in infected epithelial cells

Interleukin-22 level is negatively correlated with neutrophil recruitment in the lungs in a Pseudomonas aeruginosa pneumonia model

International audiencePseudomonas aeruginosa is a major threat for immune-compromised patients. Bacterial pneumonia can induce uncontrolled and massive neutrophil recruitment ultimately leading to acute respiratory distress syndrome and epithelium damage. Interleukin-22 plays a central role in the protection of the epithelium. In this study, we aimed to evaluate the role of interleukin-22 and its soluble receptor IL-22BP in an acute Pseudomonas aeruginosa pneumonia model in mice. In this model, we noted a transient increase of IL-22 during Pseudomonas aeruginosa challenge. Using an antibody-based approach, we demonstrated that IL-22 neutralisation led to increased susceptibility to infection and to lung damage correlated with an increase in neutrophil accumulation in the lungs. On the contrary, rIL-22 administration or IL-22BP neutralisation led to a decrease in mouse susceptibility and lung damage associated with a decrease in neutrophil accumulation. This study demonstrated that the IL-22/IL-22BP system plays a major role during Pseudomonas aeruginosa pneumonia by moderating neutrophil accumulation in the lungs that ultimately leads to epithelium protection. Pneumonia induced by Pseudomonas aeruginosa (PA), a Gram-negative opportunistic bacteria, is a major threat for immune-compromised patients 1. During infection, the host must activate a robust but adapted immune response against the pathogen while protecting the integrity and the functionality of the lungs. In the early period of pulmonary infection, there is massive polymorphonuclear neutrophil (PMN) recruitment generating oedema and tissue damage through the generation of an oxidative burst and pro-inflammatory microenvironment. Deregulated and overwhelming activation of PMN can lead to destruction of the alveolar-capillary barrier and to acute respiratory distress syndrome (ARDS) 2. Interleukin (IL)-22 is a member of the IL-10 superfamily and is currently described as the cytokine of epithelium protection

IgA protease of ST-11 isolates promotes sustained activation of JNK and apoptosis of epithelial cells.

<p>(A) Hec-1B cells were infected with the indicated strains. At each time point, samples were lysed and immunoblotted with rabbit polyclonal anti-phospho-JNK antibodies (upper panel). The membranes were subsequently stripped and re-probed with rabbit polyclonal anti-JNK antibodies as protein loading controls. Blots are representative of three separate experiments with similar results. (B) Cells were left uninfected or infected with the indicated strains for 9 h then analysed for apoptosis using annexin V staining and flow cytometry. Histogram bars represent the mean ± SD from three independent experiments. **, <i>P</i> < 0.01, ***, <i>P</i> <0.001.</p

ST-11 IgA protease-mediated nuclear cleavage of p65/RelA alters selectively expression of NF-κB responsive genes.

<p>Hec-1-B cells were infected for the indicated periods, After infection of Hec-1-B cells with the indicated strains and periods, mRNA levels of c-FLIP (A), IL-8 (B) and TNF-α (C) were evaluated by real-time PCR. Target mRNA expression was normalized to β-actin mRNA. ***, <i>P</i><0.001<i>; **</i>, <i>P</i><0.01</p

Cleavage of p65/RelA correlates with nuclear translocation of IgA protease.

<p>(A) Similarity between amino acid sequences of the hinge region of human IgA1, part of the N-terminal peptide of the human lysosome-associated membrane glycoprotein 1 LAMP1 (Accession N°: AAH06345), synaptobrevin II (Accession N°: AAF15551) targeted by neisseria IgA protease and part of the carboxy terminal peptide of the p65/RelA subunit of NF-κB (Accession N°: CAA80524). The position of amino acid residues are indicated by superscript numbers delimiting each peptide sequence. Specific cleavage sites are indicated in red and the cleavage position is represented by double-headed arrows. (B) Schematic overview of the various domains and sub-domains of neisserial IgA protease. Autocatalyic cleavage sites CS1 and CS2 and their sequences are indicated by double-headed arrows. SS: signal sequence. (C) Nuclear fractions were prepared from Hec-1-B cells infected with LNP19995 or LNP21019 at indicated time points. Samples were resolved in SDS-PAGE and probed with anti-N-terminal p65 mAb or rabbit polyclonal serum specific to IgaP sub-domain or anti-NalP specific serum. Histone H3 was used as loading control.</p

Nuclear cleavage of p65/RelA is carried out by a ST-11 meningococcal secreted serine protease.

<p>(A) For in vivo experiments (left panel), Hec-1B cells were infected for 9h in absence or presence of 1 μg.ml^-1 cycloheximide (CHX), 5μg.ml^-1 chloramphenicol (CMP) or 5 mM PMSF. After incubation cells were harvested, and nuclear fractions were prepared. For <i>in vitro</i> experiments (right panel), nuclear extracts were prepared from LPS-stimulated cells and then incubated with native meningococcal secreted proteins (N-MSP) in absence or presence of 5 mM PMSF, or heat-inactivated MSP (H-MSP) of the ST-11 isolate LNP19995. Samples were resolved by SDS-PAGE and immunoblotted with anti-p65/RelA mAb, anti-IgA protease or anti-NalP sera.Histone H3 expression (lower panel) was used as loading control. Immunoblot is representative of three independent experiments which yielded similar results. (B) Whole lysates of bacteria recovered from (A), were resolved by SDS-PAGE and immunoblotted with anti-IgA protease or anti-NalP sera.Mutant strains 19995<i>Δiga</i> and 19995<i>ΔnalP</i> were used as negative controls. Full length precursors and autocleaved forms are indicated by arrows. * represent a cross reactive bands.</p