title: In situ microscopy analysis reveals local innate immune response developed around Brucella infected cells in resistant and susceptible mice.
abstract: Brucella are facultative intracellular bacteria that chronically infect humans and animals causing brucellosis. Brucella are able to invade and replicate in a broad range of cell lines in vitro, however the cells supporting bacterial growth in vivo are largely unknown. In order to identify these, we used a Brucella melitensis strain stably expressing mCherry fluorescent protein to determine the phenotype of infected cells in spleen and liver, two major sites of B. melitensis growth in mice. In both tissues, the majority of primary infected cells expressed the F4/80 myeloid marker. The peak of infection correlated with granuloma development. These structures were mainly composed of CD11b⁺ F4/80⁺ MHC-II⁺ cells expressing iNOS/NOS2 enzyme. A fraction of these cells also expressed CD11c marker and appeared similar to inflammatory dendritic cells (DCs). Analysis of genetically deficient mice revealed that differentiation of iNOS⁺ inflammatory DC, granuloma formation and control of bacterial growth were deeply affected by the absence of MyD88, IL-12p35 and IFN-γ molecules. During chronic phase of infection in susceptible mice, we identified a particular subset of DC expressing both CD11c and CD205, serving as a reservoir for the bacteria. Taken together, our results describe the cellular nature of immune effectors involved during Brucella infection and reveal a previously unappreciated role for DC subsets, both as effectors and reservoir cells, in the pathogenesis of brucellosis.
authors.affiliation: Unité de Recherche en Biologie Moléculaire, Laboratoire d'Immunologie et de Microbiologie, Faculté Universitaire Notre Dame de la Paix, Namur, Belgium.
authors.forename: Richard
authors.initials: R
authors.lastname: Copin
authors.forename: Marie-Alice
authors.initials: MA
authors.lastname: Vitry
authors.forename: Delphine
authors.initials: D
authors.lastname: Hanot Mambres
authors.forename: Arnaud
authors.initials: A
authors.lastname: Machelart
authors.forename: Carl
authors.initials: C
authors.lastname: De Trez
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Vanderwinden
authors.forename: Stefan
authors.initials: S
authors.lastname: Magez
authors.forename: Shizuo
authors.initials: S
authors.lastname: Akira
authors.forename: Bernhard
authors.initials: B
authors.lastname: Ryffel
authors.forename: Yves
authors.initials: Y
authors.lastname: Carlier
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Letesson
authors.forename: Eric
authors.initials: E
authors.lastname: Muraille
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002002:Brucella / Q000276:immunology* / Q000472:pathogenicity; D002006:Brucellosis / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D002469:Cell Separation; D003713:Dendritic Cells / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D004195:Disease Models, Animal; D004198:Disease Susceptibility; D007113:Immunity, Innate; D008099:Liver / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D008171:Lung Diseases / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D010641:Phenotype; D013154:Spleen / Q000276:immunology / Q000382:microbiology / Q000473:pathology
chemical_list: D015415:Biomarkers; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II