title: The impact of Toll-like-receptor-9 on intestinal microbiota composition and extra-intestinal sequelae in experimental Toxoplasma gondii induced ileitis.
abstract: BACKGROUND
  Following peroral Toxoplasma (T.) gondii infection, susceptible mice develop acute ileitis due to a microbiota-dependent Th1 type immunopathology. Toll-like-receptor (TLR)-9 is known to recognize bacterial DNA and mediates intestinal inflammation, but its impact on intestinal microbiota composition and extra-intestinal sequelae following T. gondii infection has not yet been elucidated.
  
  
  RESULTS
  Seven days following peroral infection (p.i.) with 100 cysts of T. gondii ME49 strain, TLR-9(-/-) and wildtype (WT) mice suffered from comparable ileitis, whereas ileal parasitic loads as well as IFN-γ and nitric oxide levels were higher in TLR-9(-/-) compared to WT mice. Locally, TLR-9(-/-) mice exhibited increased ileal CD3+, but not FOXP3+ cell numbers at day 7 p.i.; in mesenteric lymph nodes IFN-γ-producing CD4+ cell numbers and TNF-α and IFN-γ concentrations were also increased in TLR-9(-/-) compared to WT mice. T. gondii DNA levels, however, did not differ in mice of either genotype. Differences in intestinal microbiota were rather subtle except for bifidobacteria that were virtually absent in both, naïve and T. gondii infected TLR-9(-/-), but not WT mice. Extra-intestinally, TLR-9(-/-) mice displayed less distinct systemic immune responses as indicated by lower serum IL-6, and splenic TNF-α and IFN-γ levels as compared to WT mice despite higher translocation rates of intestinal bacteria to extra-intestinal compartments such as liver, spleen, kidney, and cardiac blood. Most importantly, brains were also affected in this inflammatory scenario as early as day 7 p.i. Remarkably, TLR-9(-/-) mice exhibited more pronounced inflammatory infiltrates with higher numbers of F4/80+ macrophages and microglia in the cortex and meninges as compared to WT mice, whereas T. gondii DNA levels did not differ.
  
  
  CONCLUSIONS
  We here show that TLR-9 is not required for the development of T. gondii induced ileitis but mediates distinct inflammatory changes in intestinal and extra-intestinal compartments including the brain.
authors.affiliation: Department of Microbiology and Hygiene, Charité - University Medicine Berlin, Centrum 5, Campus Benjamin Franklin, Hindenburgdamm 27, D-12203 Berlin, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Bereswill
authors.affiliation: Department of Internal Medicine, Rheumatology and Clinical Immunology/Research Center ImmunoSciences (RCIS), Charité - University Medicine Berlin, Berlin, Germany.
authors.forename: Anja A
authors.initials: AA
authors.lastname: Kühl
authors.affiliation: Department of Microbiology and Hygiene, Charité - University Medicine Berlin, Centrum 5, Campus Benjamin Franklin, Hindenburgdamm 27, D-12203 Berlin, Germany.
authors.forename: Marie
authors.initials: M
authors.lastname: Alutis
authors.affiliation: Department of Microbiology and Hygiene, Charité - University Medicine Berlin, Centrum 5, Campus Benjamin Franklin, Hindenburgdamm 27, D-12203 Berlin, Germany.
authors.forename: André
authors.initials: A
authors.lastname: Fischer
authors.affiliation: Department of Microbiology and Hygiene, University of Magdeburg, Magdeburg, Germany.
authors.forename: Luisa
authors.initials: L
authors.lastname: Möhle
authors.affiliation: Department of Microbiology and Hygiene, Charité - University Medicine Berlin, Centrum 5, Campus Benjamin Franklin, Hindenburgdamm 27, D-12203 Berlin, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Struck
authors.affiliation: Department of Microbiology and Hygiene, Charité - University Medicine Berlin, Centrum 5, Campus Benjamin Franklin, Hindenburgdamm 27, D-12203 Berlin, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Liesenfeld
authors.affiliation: Department of Microbiology and Hygiene, Charité - University Medicine Berlin, Centrum 5, Campus Benjamin Franklin, Hindenburgdamm 27, D-12203 Berlin, Germany.
authors.forename: Ulf B
authors.initials: UB
authors.lastname: Göbel
authors.affiliation: Department of Microbiology and Hygiene, University of Magdeburg, Magdeburg, Germany.
authors.forename: Ildikò R
authors.initials: IR
authors.lastname: Dunay
authors.affiliation: Department of Microbiology and Hygiene, Charité - University Medicine Berlin, Centrum 5, Campus Benjamin Franklin, Hindenburgdamm 27, D-12203 Berlin, Germany.
authors.forename: Markus M
authors.initials: MM
authors.lastname: Heimesaat
keywords: Acute ileitis; Bacterial translocation; Bifidobacteria; Extra-intestinal immune responses; FOXP3; Gut-brain-axis; Intestinal microbiota composition; Intracerebral inflammation; Pro-inflammatory cytokines; Regulatory T cells; Systemic inflammatory response; TLR-9; Th1-type immunopathology; Toxoplasma gondii