title: Escherichia coli ghosts promote innate immune responses in human keratinocytes.
abstract: Bacterial ghosts (BGs) as non-living bacterial envelopes devoid of cytoplasmic content with preserved and intact inner and outer membrane structures of their living counterparts have been used to study the ability of their surface components for the induction of antimicrobial peptides and pro-inflammatory cytokines in human primary keratinocytes (KCs). Quantitative real-time PCR analysis revealed that incubation of KCs with BGs generated from wild-type Escherichia coli induced the mRNA expression of antimicrobial psoriasin (S100A7c) in a BGs particle concentration-dependent manner. Using immunoblot analysis we showed that BGs generated from the flagellin-deficient (ΔFliC) E. coli strain NK9375 were as effective as its isogenic wild-type (wt) E. coli strain NK9373 to induce psoriasin expression when normalized to BG particles being taken up by KCs. However, results obtained from endocytic activity of KCs reflect that internalization of BGs is greatly dependent on the presence of flagellin on the surface of BGs. Moreover, BGs derived from wt E. coli NK9373 strongly induced the release of the pro-inflammatory cytokines IL-6 and IL-8, compared to ΔFliC E. coli NK9375 BGs. Taken together, obtained data demonstrate that non-living BGs possessing all bacterial bio-adhesive surface properties in their original state while not posing any infectious threat have the capacity to induce the expression of innate immune modulators and that these responses are partially dependent on the presence of flagellin.
authors.affiliation: Department of Dermatology, Medical University of Vienna, A-1090 Vienna, Austria.
authors.forename: Arby
authors.initials: A
authors.lastname: Abtin
authors.forename: Pavol
authors.initials: P
authors.lastname: Kudela
authors.forename: Ulrike Beate
authors.initials: UB
authors.lastname: Mayr
authors.forename: Verena Juliana
authors.initials: VJ
authors.lastname: Koller
authors.forename: Michael
authors.initials: M
authors.lastname: Mildner
authors.forename: Erwin
authors.initials: E
authors.lastname: Tschachler
authors.forename: Werner
authors.initials: W
authors.lastname: Lubitz
mesh_terms: D004705:Endocytosis; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology*; D029968:Escherichia coli Proteins / Q000235:genetics; D005408:Flagellin; D017353:Gene Deletion; D006801:Humans; D007113:Immunity, Innate; D015603:Keratinocytes / Q000276:immunology* / Q000382:microbiology; D000075023:S100 Calcium Binding Protein A7; D009418:S100 Proteins / Q000096:biosynthesis*
chemical_list: D029968:Escherichia coli Proteins; C516095:FliC protein, E coli; D000075023:S100 Calcium Binding Protein A7; D009418:S100 Proteins; C089242:S100A7 protein, human; D005408:Flagellin