title: Genome-wide RNAi screen in IFN-γ-treated human macrophages identifies genes mediating resistance to the intracellular pathogen Francisella tularensis.
abstract: Interferon-gamma (IFN-γ) inhibits intracellular replication of Francisella tularensis in human monocyte-derived macrophages (HMDM) and in mice, but the mechanisms of this protective effect are poorly characterized. We used genome-wide RNA interference (RNAi) screening in the human macrophage cell line THP-1 to identify genes that mediate the beneficial effects of IFN-γ on F. tularensis infection. A primary screen identified ∼200 replicated candidate genes. These were prioritized according to mRNA expression in IFN-γ-primed and F. tularensis-challenged macrophages. A panel of 20 top hits was further assessed by re-testing using individual shRNAs or siRNAs in THP-1 cells, HMDMs and primary human lung macrophages. Six of eight validated genes tested were also found to confer resistance to Listeria monocytogenes infection, suggesting a broadly shared host gene program for intracellular pathogens. The F. tularensis-validated hits included 'druggable' targets such as TNFRSF9, which encodes CD137. Treating HMDM with a blocking antibody to CD137 confirmed a beneficial role of CD137 in macrophage clearance of F. tularensis. These studies reveal a number of important mediators of IFN-γ activated host defense against intracellular pathogens, and implicate CD137 as a potential therapeutic target and regulator of macrophage interactions with Francisella tularensis.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Zhou
authors.forename: Glen
authors.initials: G
authors.lastname: DeLoid
authors.forename: Erica
authors.initials: E
authors.lastname: Browning
authors.forename: David J
authors.initials: DJ
authors.lastname: Gregory
authors.forename: Fengxiao
authors.initials: F
authors.lastname: Tan
authors.forename: Alice S
authors.initials: AS
authors.lastname: Bedugnis
authors.forename: Amy
authors.initials: A
authors.lastname: Imrich
authors.forename: Henry
authors.initials: H
authors.lastname: Koziel
authors.forename: Igor
authors.initials: I
authors.lastname: Kramnik
authors.forename: Quan
authors.initials: Q
authors.lastname: Lu
authors.forename: Lester
authors.initials: L
authors.lastname: Kobzik
mesh_terms: D002478:Cells, Cultured; D005604:Francisella tularensis / Q000235:genetics / Q000276:immunology*; D015894:Genome, Human / Q000276:immunology*; D055106:Genome-Wide Association Study; D006801:Humans; D007109:Immunity / Q000235:genetics*; D007371:Interferon-gamma / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000382:microbiology*; D035683:MicroRNAs / Q000235:genetics; D034622:RNA Interference; D053261:Tumor Necrosis Factor Receptor Superfamily, Member 9
chemical_list: D035683:MicroRNAs; D053261:Tumor Necrosis Factor Receptor Superfamily, Member 9; D007371:Interferon-gamma