Innate Host Defense and Inflammation - Inserm U874  


  HEADDr Michel Chignard / michel.chignard@pasteur.fr
  MEMBERSDr Viviane Balloy, Diane Barbier, Dr Fatima Ben Mohamed, Claire Besson, Dr Fany Blanc, Dr Michel Chignard, Dr Delphyne Descamps, Dr Laetitia Furio, Dr Ignacio Garcia Verdugo, Dominique Leduc, Pr Jean-Michel Sallenave, Dr Mustapha Si-Tahar, Brigitte Solhonne, Dr Lhousseine Touqui, Josiane Villeneuve, Dr Yongzheng Wu


  Annual Report

Introduction. The lung is the site of various infectious diseases for which mechanisms of innate defense and inflammation play a major role. Acute pneumonias from bacterial, fungal or viral origins and Chronic obstructive pulmonary disease (COPD) or cystic fibrosis (CF) are typical lung pathologies. The induction of innate defense is a beneficial process but its exacerbation may lead to a pathologic inflammatory status. Therefore, the aim of our research is to contribute to the qualitative and quantitative understanding of the mechanisms involved in these diseases, which would allow to target the events enhancing innate immunity without exacerbating the inflammatory process, or to down-regulate inflammation without compromising innate defense.

Role of Toll-like receptors (TLR) in fungal and bacterial infections. TLR recognize specific conserved molecular patterns expressed by microorganisms and trigger an innate immune response through a signaling pathway that involves mainly the adapter MyD88. We specifically studied the role of those receptors in the defense against microorganisms such as the opportunistic fungus Aspergillus fumigatus, and the Gram- bacteria Pseudomonas aeruginosa andBurkholderia cenocepacia. Although it has been reported thatA. fumigatusinduces innate responses in vivothrough TLR2 (our own data in collaboration with the Unité des Aspergillus), TLR4 and MyD88, we observed that respiratory epithelial cells (REC) activated by A. fumigatusin vitroproduced IL-8 and IL-6 independently from those pathways. In addition, we looked at the susceptibility of mice to P. aeruginosaand B. cenocepaciaacute lung infection. We demonstrated that the TLR4/MyD88-dependent pathway critically contributes to a detrimental host inflammatory response that leads to B. cenocepacia-trigerred fatal pneumonia. In parallel, using a mice model deficient for TLR4 and 5, we showed that the lung lethal infection by P. aeruginosainvolves the type II secretion system. In addition, we have recently discovered a new pathway leading to the recognition and phagocytosis of P. aeruginosa by alveolar macrophages,linking TLR5 recognition and inflammasome activation.

Molecular mechanisms involved in innate immune response to influenza A virus (IAV) infection. Respiratory viral infections have been implicated in exacerbations of allergic asthma, characterized by a Th2-biased immune response. Respiratory viruses target airway epithelial cells and dendritic cells (DCs). Their activation is, at least in part, mediated by a TLR3-dependent recognition of virus-derived double-stranded RNA (dsRNA). To elucidate the role of epithelial cells and DCs and the implication of TLR3/TRIF pathway, we contributed to a study that used a mouse model of lung allergic exacerbation. We found that treatment with dsRNA significantly increased airway hyperresponsiveness and lung inflammation. This was associated with an infiltrate of eosinophils, myeloid DCs, and T lymphocytes. In vivo and in vitro treatment with dsRNA amplified airway epithelial production of the pro-Th2 chemokines CCL11 and CCL17, their secretion being enhanced by Th2 cytokines. In conclusion, dsRNA derived from respiratory viruses trigger exacerbation of the pulmonary allergic reaction through TLR3/TRIF-dependent pathway. Moreover, Th2 cytokines participate in this process by modulating the response of airway epithelium and DCs to dsRNA.

In parallel, we also focus on the mechanisms of IAV entry into cells and the induction of mucins as a potential protective pathway. Entry is considered to be triggered by host cellular trypsin-type proteases, which proteolytically activate the viral surface hemagglutinin (HA). We performed studies to (i) characterize the cellular proteases involved in the maturation of HA in the infected host and (ii) analyze the effect of anti-proteases in vivo usingan adenovirus(Ad)-mediated gene transfer strategy as well as transgenic mice. Altogether, these studies may constitute a key step towards the identification of new targets for the treatment of IAV infections.

Mechanisms of regulation and roles of phospholipases A2. Although antibiotic resistance is recognized as a major public health worldwide only few studies have been performed to identify alternative approaches to eradicate bacteria in animal models. We have investigated the potential role of antimicrobial peptides including secreted phospholipase A2 (sPLA2) in the control of lung infection by P. aeruginsoa.Using a mouse model of lung infection we showed that intranasal instillation of the type-IIA sPLA2 (sPLA2-IIA) was able to eliminate multi-resistant strains of P. aeruginosaand to increase animal survival. This enzyme attenuated P. aeruginosadissemination and proliferation as evidenced by a non-invasive method using a bioluminescent strain of this bacterium. The bactericidal effect of sPLA2-IIA was due to hydrolysis of membrane phospholipids of P. aeruginosa.On the other hand, we showed, in a collaborative study, that bacteriophage treatment was also effective in saving animals from lethal infection and prevented bacterial proliferation and dissemination. The effect of bacteriophages was specific for the bacterial strains used.

Thus, both sPLA2 and bacteriophages can be considered as therapeutic agents to combat bacterial lung infection.

Modulation of the maladaptive mucosal host response in cystic fibrosis. The neutrophil is a major inflammatory cell type which can be involved in maladaptive responses to inflammatory/infective stimuli at mucosal surfaces. Among the potentially noxious mediators that this cell type can release, neutrophil elastase (NE) bioactivity has been shown to be present at high levels in the lung and intestine. Using pleiotropic anti-NE/anti-infective molecules (SLPI and elafin : over-expression obtained by adenovirus, transgenic mice, recombinant P. aeruginosa and probiotic bacterial strains), we aimed to correct this maladaptive phenotype, in a variety of in vitro and murine models, with potential translational applications in diseases such as cystic fibrosis, emphysema, and inflammatory bowel diseases.

Keywords: Innate immunity, Lung, Infection, Inflammation, Signalling



  Publications

- Pothlichet J, Burtey A, Kubarenko AV, Caignard G. Solhonne B, Tangy F, Ben-Ali M, Quintana-Murci L, Heinzmann A, Chiche JD, Vidalain PO, Weber AN, Chignard M, Si-Tahar M.Study of human RIG-I polymorphisms identifies two variants with an opposite impact on the antiviral immune response. PLoS One. 2009;4:e7582.

- Raymond B, Batsche E, Boutillon F, Wu YZ, Leduc D, Balloy V, Raoust E, Muchardt C, Goossens PL, Touqui L. Anthrax lethal toxin impairs IL-8 expression in epithelial cells through inhibition of histone H3 modification. PLoS Pathog. 2009;5 :e1000359.

- Wilkinson TS, Dhaliwal K, Hamilton TW, Lipka AF, Farrell L, Davidson DJ, Duffin R, Morris AC, Haslett C, Govan JR, Gregory CD, Sallenave JM, Simpson AJ. Trappin-2 promotes early clearance of Pseudomonas aeruginosa through CD14-dependent macrophage activation and neutrophil recruitment. Am J Pathol. 2009; 174:1338-46.

- Balloy V, Sallenave JM, Wu Y, Touqui L, Latgé JP, Si-Tahar M, Chignard M. Aspergillus fumigatus-induced interleukin-8 synthesis by respiratory epithelial cells is controlled by the phosphatidylinositol 3-kinase, p38 MAPK, and ERK1/2 pathways and not by the toll-like receptor-MyD88 pathway. J Biol Chem. 2008;283:30513-21.

- Ramphal R, Balloy V, Jyot J, Verma A, Si-Tahar M, Chignard M. Control of Pseudomonas aeruginosa in the lung requires the recognition of either lipopolysaccharide or flagellin. J Immunol. 2008;181:586-92.





Activity Reports 2010 - Institut Pasteur
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