PhD PROPOSAL FOR THE PASTEUR-PARIS UNIVERSITY INTERNATIONAL PROGRAM

 

Deadline for full application: December 15th, 2013

Interviews: March, 2014

Start of the Ph.D.: October 1st, 2014

 

 

Department: Microbiology

Title of the PhD project: Escape of pathogenic Leptospira from the immune system and chronic colonization of the mouse kidney

Name of the lab: BGPB

Head of the lab: Ivo BONECA

PhD advisor: Catherine WERTS

Email address: cwerts@pasteur.fr

Web site address of the lab: http://www.pasteur.fr/ip/easysite/pasteur/fr/recherche/departements-scie...

Doctoral school affiliation and University: GC2ID/Paris 5 Descartes

 

Presentation of the laboratory and its research topics:

The Biology and genetics of bacterial cell wall (BGPB) unit studies the biosynthesis and degradation of peptidoglycan and other bacterial cell wall components, and their recognition by the host immune system using different models such as Helicobacter pylori and Leptospira interrogans.

 

Description of the project:

Conserved microbial components such as bacterial lipopolysaccharide, flagellin, nucleic acids and peptidoglycan are referred to as “microbe associated molecular patterns” (MAMPs) and are recognized by “pattern recognition receptors” (PRRs) of the innate immune system, such as Toll-like and/or Nod-like receptors, which initiate an inflammatory response aimed at clearance of the pathogen. Leptospirosis is a zoonosis transmitted by chronically infected asymptomatic rodents, through excretion in their urine of bacteria, contaminating the soil. Pathogenic Leptospira interrogans are spiral motile bacteria that enter a diverse range of hosts through the skin and mucosa. Infected humans can develop either a flu-like, usually mild illness, or severe disease with kidney, liver and heart failure. In East Asia, leptospirosis is a serious health issue affecting paddy fields workers. 

Previous studies of the laboratory have focused on innate recognition of Leptospira interrogans’s lipopolysaccharide (LPS) and lipoproteins. LPS from Leptospira is atypical and is recognized by TLR2, as are Leptospira lipoproteins. Although Leptospiral LPS it is recognized perfectly by mouse TLR4, it evades recognition by human TLR4. Whereas control mice are asymptomatic, we found that transgenic mice, deficient for TLR4 and TLR2, are very sensitive to leptospirosis, and showed a crucial role of B cells and TLR4 in the clearance of Leptospira. We also recently deciphered the mechanism of inflammasome activation and subsequent IL1ß secretion by Leptospira, which is dependent on NLRP3 and TLR2/4 signaling. In addition, we have recently developed bioluminescent Leptospira and are beginning to use live imaging to study the consequences of chronic renal infection in mice.

The candidate’s project aims to better understand how pathogenic Leptospira escape the innate immune responses, chronically colonize the kidneys and alter the renal functions of their hosts. He/she will first study the innate response to flagellin, a very potent MAMP, usually recognized by TLR5 and the NLRC4 inflammasome. Leptospira species, whose cell wall possesses two membranes, are peculiar since they harbor one flagellum at each pole. These endoflagella do not protrude to the exterior of the bacterium, but are contained within the periplasmic space. The candidate will purify the flagellin subunits and whole flagella, and study their reactivity towards different human and murine PRRs using human cells and macrophages from transgenic mice. In parallel, bone marrow derived macrophages, human macrophage cell lines and transgenic mice will be infected with live bacteria to study the signaling pathways involved. We also wonder whether asymptomatic leptospirosis can sensitize the kidney and further favor other bacterial infections or nephropathy. Using a murine model of renal chronic infection with Leptospira, the candidate will study the pathophysiological consequences of chronic renal carriage of Leptospira in a model of experimental retrourethral infection of mice, using uropathogenic strains of E. coli or upon administration of toxic herbal compounds. 

This project will integrate different approaches and techniques (in vitro/in vivo, molecular biology, biochemistry, cell signaling, FACS analysis) and new tools (bioluminescent bacteria, murine models of acute and chronic leptospirosis) to better understand the specificities of mouse and human responses to Leptospira, and to address several fundamental questions relating to the ability of Leptospira to escape immune responses and colonize kidneys, which could potentially favor other kidney pathologies by perturbing kidney function.

 

 

 

References:

Lacroix-Lamandé S, d'Andon MF, Michel E, Ratet G, Philpott DJ, Girardin SE, Boneca IG, Vandewalle A, Werts C. Downregulation of the Na/K-ATPase pump by leptospiral glycolipoprotein activates the NLRP3 inflammasome. J Immunol. 2012 Mar 15;188(6):2805-14. Epub 2012 Feb 8.

TLR4- and TLR2-mediated B cell responses control the clearance of the bacterial pathogen, Leptospira interrogans. Chassin C, Picardeau M, Goujon JM, Bourhy P, Quellard N, Darche S, Badell E, d'Andon MF, Winter N, Lacroix-Lamandé S, Buzoni-Gatel D, Vandewalle A, Werts C. J Immunol. 2009 Aug 15;183(4):2669-77. Epub 2009 Jul 27.  

 

Chaput C, Ecobichon C, Cayet N, Girardin SE, Werts C, Guadagnini S, Prevost MC, Mengin-Lecreulx D, Labigne A, Boneca IG. Role of AmiA in the morphological transition of Helicobacter pylori and in immune escape. PLoS Pathog. 2006 Sep;2(9):e97.

 

Nahori M, Fournié-Amazouz E, Que-Gewirth N.S, Balloy V, Chignard, Raetz C.R.H, Saint-Girons I, Werts C. Differential TLR recognition of leptospiral lipid A and LPS in murine and human cells. Running title: leptospiral lipid A is a murine but not a human TLR4-MD2 agonist. J. Immunol. 2005; 175:6022-31

 

Werts C, Tapping RI, Mathison JC, Chuang TH, Kravchenko V, Saint Girons I, Haake DA, Godowski PJ, Hayashi F, Ozinsky A, Underhill DM, Kirschning CJ, Wagner H, Aderem A, Tobias PS, Ulevitch RJ. Leptospiral lipopolysaccharide activates cells through a TLR2-dependent mechanism. Nat Immunol. 2001 Apr;2(4):346-52.

 

 

 

Keywords:

 

Innate immunity, Toll-like receptors, Nod-like receptor, TLR5, NLRC4, Flagellin, Inflammasome

Leptospira interrogans, leptospirosis, kidney, murine models, chronic infection, acute infection

 

 

Expected profile of the candidate (optional):

 

in mouse work will be The candidate will work with mice and pathogenic Leptospira.

 

 

Contact: Catherine WERTS. cwerts@pasteur.fr

Mis à jour le 16/09/2013