title: Induction of inflammatory responses from THP-1 cells by cell-free filtrates from clinical isolates of Alloiococcus otitidis.
abstract: In our model system using the THP-1 monocytic cell line, whole heat-killed cells of Alloiococcus otitidis elicited several pro-inflammatory cytokines identified in ear effusions of children with otitis media (OM). Levels of these cytokines were equivalent to or greater than those elicited by a standard Gram-positive otopathogen, Streptococcus pneumoniae. The current study examined the hypothesis that extracellular material produced by A. otitidis might also contribute to the inflammatory responses in OM. Cell-free culture filtrates of recent A. otitidis isolates (n = 39) were tested for induction of pro-inflammatory cytokines from THP-1 cells primed with IFN-γ. The highest responses were from IL-8 followed by IL-1β, and the lowest from IL-6. Filtrates from nine isolates were treated with lysozyme or proteinase K to assess the nature of the extracellular stimulants. Peptidoglycan was not a major component eliciting the responses. There was no correlation between colony type or β-haemolysin production. Proteinase K treatment indicated extracellular proteins might induce the inflammatory responses, particularly the 70-75 ku band. Further studies on the role of the extracellular proteins of A. otitidis and cytokine responses in pathogenesis of ear infections are needed.
authors.affiliation: 1Hunter Area Pathology Service Microbiology, The University of Newcastle, Newcastle, New South Wales, Australia.
authors.forename: Christopher
authors.initials: C
authors.lastname: Ashhurst-Smith
authors.forename: Sharron T
authors.initials: ST
authors.lastname: Hall
authors.forename: Christine J
authors.initials: CJ
authors.lastname: Burns
authors.forename: John
authors.initials: J
authors.lastname: Stuart
authors.forename: C Caroline
authors.initials: CC
authors.lastname: Blackwell
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D056568:Carnobacteriaceae / Q000737:chemistry* / Q000254:growth & development; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis; D019286:Endopeptidase K / Q000737:chemistry; D006460:Hemolysin Proteins / Q000096:biosynthesis; D006801:Humans; D006868:Hydrolysis; D007249:Inflammation / Q000276:immunology / Q000473:pathology*; D007371:Interferon-gamma / Q000494:pharmacology; D009000:Monocytes / Q000276:immunology / Q000473:pathology*; D009113:Muramidase / Q000737:chemistry; D010033:Otitis Media / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D016207:Cytokines; D006460:Hemolysin Proteins; D007371:Interferon-gamma; D009113:Muramidase; D019286:Endopeptidase K
keywords: Alloiococcus otitidis; cytokines; otitis media