title: FcγR mediates TLR2- and Syk-dependent NLRP3 inflammasome activation by inactivated Francisella tularensis LVS immune complexes.
abstract: IgG (mAb)-opsonized, inactivated Francisella tularensis LVS (iFt-mAb) enhances TLR2-dependent IL-6 production by macrophages via Fcγ receptors (FcγR). In mice, vaccination with iFt-mAb provides IgA-dependent protection against lethal challenge with Ft LVS. Because inflammasome maturation of IL-1β is thought important for antibody-mediated immunity, we considered the possibility that iFt-mAb elicits an FcγR-dependent myeloid cell inflammasome response. Herein, we find that iFt-mAb enhances macrophage and dendritic cell IL-1β responses in a TLR2- and FcγR-dependent fashion. Although iFt-mAb complexes bind FcγR and are internalized, sensing of cytosolic DNA by absent in melanoma 2 (AIM2) is not required for the IL-1β response. In contrast, ASC, caspase-1, and NLR family pyrin domain-containing 3 (NLRP3) are indispensable. Further, FcγR-mediated spleen tyrosine kinase (Syk) signaling is required for this NLRP3-dependent IL-1β response, but the alternative IL-1β convertase caspase-8 is insufficient. Finally, iFt-mAb-vaccinated wild-type mice exhibit a significant delay in time to death, but IL-1R1- or Nlrp3-deficient mice vaccinated in this way are not protected and lack appreciable Francisella-specific antibodies. This study demonstrates that FcγR-mediated Syk activation leads to NLRP3 inflammasome-dependent IL-1β production in macrophages and suggests that an Nlrp3- and IL-1R-dependent process contributes to the IgA response important for protection against Ft LVS. These findings extend our understanding of cellular responses to inactivated pathogen-opsonized vaccine, establish FcγR-elicited Syk kinase-mediated NLRP3 inflammasome activation, and provide additional insight toward understanding crosstalk between TLR and FcγR signals.
authors.affiliation: Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA.
authors.forename: Ellen B
authors.initials: EB
authors.lastname: Duffy
authors.affiliation: Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA.
authors.forename: Sivakumar
authors.initials: S
authors.lastname: Periasamy
authors.affiliation: Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA.
authors.forename: Danielle
authors.initials: D
authors.lastname: Hunt
authors.affiliation: Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA.
authors.forename: James R
authors.initials: JR
authors.lastname: Drake
authors.affiliation: Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA hartonj@mail.amc.edu.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Harton
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology; D000936:Antigen-Antibody Complex / Q000276:immunology*; D000942:Antigens, Bacterial / Q000276:immunology*; D001428:Bacterial Vaccines; D053181:Caspase 8 / Q000276:immunology; D002460:Cell Line; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D005604:Francisella tularensis / Q000276:immunology*; D058847:Inflammasomes / Q000276:immunology*; D053583:Interleukin-1beta / Q000276:immunology; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009000:Monocytes / Q000276:immunology / Q000378:metabolism; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein / Q000172:deficiency / Q000276:immunology*; D017452:Receptors, IgG / Q000276:immunology*; D015398:Signal Transduction; D000072377:Syk Kinase / Q000276:immunology*; D051195:Toll-Like Receptor 2 / Q000276:immunology*; D014611:Vaccination
chemical_list: D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D000942:Antigens, Bacterial; D001428:Bacterial Vaccines; D058847:Inflammasomes; D053583:Interleukin-1beta; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; C492716:Nlrp3 protein, mouse; D017452:Receptors, IgG; C495342:TLR2 protein, human; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; C505530:CASP8 protein, human; C505526:Casp8 protein, mouse; D053181:Caspase 8
keywords: IL-1β; macrophage; vaccine