Abstract
Intracellular replication and persistence strategies of the Q fever pathogenCoxiella burnetiiCoxiella burnetii is the causative agent of human Q Fever, considered as one of the most relevant re- emerging zoonosis in Europe. C. burnetii infects humans through the inhalation of contaminated aerosols, causing epidemics with serious economic and health consequences. Following internalisation, C. burnetii subverts host cell functions to inhibit the innate immune response and generate a replicative niche called CCV (Coxiella-containing vacuole) characterised by a unique protein and lipid composition. My thesis project focuses on the study of the host/pathogen interactions underlying the persistence and intracellular replication of C. burnetii.First, the function of the effector protein NopA was discovered showing how this protein inhibits the innate immune response in infected cells. The results obtained during my PhD have shown that NopA interacts with Ran and triggers an imbalance in its nucleocytoplasmic gradient, thereby perturbing the nuclear import of eukaryotic proteins and the expression of pro-inflammatory cytokines. In parallel, the role of lipid metabolism in the establishment of the CCV was investigated. By using a wide array of lipid probes and confocal microscopy, the lipid signature of CCVs was determined and revealed that PI(4)P and LBPA are actively subverted by C. burnetii during infection. Lipid pulldown assays then led to the identification of C. burnetii candidate effector proteins interacting with host cell lipids. One of them, CBU0635, is a putative phosphoinositide phosphatase that diverts the secretory pathway to the forming Coxiella- containing vacuole while CBU2007 manipulates lysobisphosphatidic acid metabolism to recruit the ESCRT machinery and block the biogenesis of multivesicular bodies. These results help to better understand intracellular replication and persistence strategies of C. burnetii and could allow the development of new antimicrobials and the therapeutic repurposing of C. burnetii proteins.