title: Persisting Rickettsia typhi Causes Fatal Central Nervous System Inflammation.
abstract: Rickettsioses are emerging febrile diseases caused by obligate intracellular bacteria belonging to the family Rickettsiaceae. Rickettsia typhi belongs to the typhus group (TG) of this family and is the causative agent of endemic typhus, a disease that can be fatal. In the present study, we analyzed the course of R. typhi infection in C57BL/6 RAG1(-/-) mice. Although these mice lack adaptive immunity, they developed only mild and temporary symptoms of disease and survived R. typhi infection for a long period of time. To our surprise, 3 to 4 months after infection, C57BL/6 RAG1(-/-) mice suddenly developed lethal neurological disorders. Analysis of these mice at the time of death revealed high bacterial loads, predominantly in the brain. This was accompanied by a massive expansion of microglia and by neuronal cell death. Furthermore, high numbers of infiltrating CD11b(+) macrophages were detectable in the brain. In contrast to the microglia, these cells harbored R. typhi and showed an inflammatory phenotype, as indicated by inducible nitric oxide synthase (iNOS) expression, which was not observed in the periphery. Having shown that R. typhi persists in immunocompromised mice, we finally asked whether the bacteria are also able to persist in resistant C57BL/6 and BALB/c wild-type mice. Indeed, R. typhi could be recultivated from lung, spleen, and brain tissues from both strains even up to 1 year after infection. This is the first report demonstrating persistence and reappearance of R. typhi, mainly restricted to the central nervous system in immunocompromised mice.
authors.affiliation: Department of Immunology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany osterloh@bni-hamburg.de.
authors.forename: Anke
authors.initials: A
authors.lastname: Osterloh
authors.affiliation: Department of Immunology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Papp
authors.affiliation: Department of Immunology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
authors.forename: Kristin
authors.initials: K
authors.lastname: Moderzynski
authors.affiliation: Department of Immunology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
authors.forename: Svenja
authors.initials: S
authors.lastname: Kuehl
authors.affiliation: Department of Immunology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
authors.forename: Ulricke
authors.initials: U
authors.lastname: Richardt
authors.affiliation: Institute for Immunology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Fleischer
mesh_terms: D000818:Animals; D001921:Brain / Q000469:parasitology / Q000473:pathology; D002494:Central Nervous System Infections / Q000382:microbiology* / Q000473:pathology*; D002908:Chronic Disease; D018398:Homeodomain Proteins / Q000235:genetics; D007249:Inflammation / Q000473:pathology*; D008168:Lung / Q000469:parasitology; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D052247:Nitric Oxide Synthase Type II / Q000032:analysis; D012286:Rickettsia typhi / Q000302:isolation & purification*; D013154:Spleen / Q000469:parasitology; D014437:Typhus, Endemic Flea-Borne / Q000382:microbiology* / Q000473:pathology*
chemical_list: D018398:Homeodomain Proteins; C064658:RAG-1 protein; D052247:Nitric Oxide Synthase Type II