Contributors: Physiopathologie et Epidémiologie des Maladies Respiratoires (PHERE (UMR_S_1152 / U1152)); Université Paris Diderot - Paris 7 (UPD7)-Institut National de la Santé et de la Recherche Médicale (INSERM); Lab Excellence Inflamex; Université Paris Diderot - Paris 7 (UPD7); Centre de recherche sur l'Inflammation (CRI (UMR_S_1149 / ERL_8252 / U1149)); Université Paris Diderot - Paris 7 (UPD7)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS); Centre d’Infection et d’Immunité de Lille - INSERM U 1019 - UMR 9017 - UMR 8204 (CIIL); Institut Pasteur de Lille; Réseau International des Instituts Pasteur (RIIP)-Réseau International des Instituts Pasteur (RIIP)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université de Lille-Centre Hospitalier Régional Universitaire CHU Lille (CHRU Lille)-Centre National de la Recherche Scientifique (CNRS); Laboratoire d'ingénierie des systèmes macromoléculaires (LISM); Aix Marseille Université (AMU)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS); Fondation pour la Recherche Medicale” forfinancing a 6 months grant to FB (dossier FRM: FDT20150532126)and “Vaincre la Mucoviscidose”.; We wish to thank Prs G. Döhring and DE. Ohman for the gift of purified LasB and the PAO1 LasB-deleted strain (PD0240), respectively, and Dr. Gyorgy Fejer (University of Plymouth, United Kingdom) for the kind gift of MPI cells. We acknowledge Mrs. B. Solhonne and V. Balloy for technical assistance, and Drs. M. Chignard, M. Le Gars, D. Descamps, I. Garcia-Verdugo, R. Ramphal, and D. Pidart for useful discussions and advice at the onset of the project. We also thank the Mass Spectrometry Laboratory (Institut Jacques Monod, UMR 7592, Univ Paris Diderot, CNRS, Sorbonne Paris Cité, F-75205 Paris, France) for LC-MS/MS acquisition and analysis.
نبذة مختصرة : International audience ; Pseudomonas aeruginosa (P.a) is a pathogen causing significant morbidity and mortality, in particular, in hospital patients undergoing ventilation and in patients with cystic fibrosis. Among the virulence factors secreted or injected into host cells, the physiopathological relevance of type II secretions system (T2SS) is less studied. Although there is extensive literature on the destructive role of LasB in vitro on secreted innate immune components and on some stromal cell receptors, studies on its direct action on myeloid cells are scant. Using a variety of methods, including the use of bacterial mutants, gene-targeted mice, and proteomics technology, we show here, using non-opsonic conditions (thus mimicking resting and naïve conditions in the alveolar space), that LasB, an important component of the P.a T2SS is highly virulent in vivo, and can subvert alveolar macrophage (AM) activity and bacterial killing, in vitro and in vivo by downregulating important secreted innate immune molecules (complement factors, cytokines, etc.) and receptors (IFNAR, Csf1r, etc.). In particular, we show that LasB downregulates the production of C3 and factor B complement molecules, as well as the activation of reactive oxygen species production by AM. In addition, we showed that purified LasB impaired significantly the ability of AM to clear an unrelated bacterium, namely Streptococcus pneumoniae. These data provide a new mechanism of action for LasB, potentially partly explaining the early onset of P.a, alone, or with other bacteria, within the alveolar lumen in susceptible individuals, such as ventilated, chronic obstructive pulmonary disease and cystic fibrosis patients.
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